[PATCH 01/20] io-controller: Documentation

[PATCH 01/20] io-controller: Documentation

[Vivek Goyal]

o Documentation for io-controller.

Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 Documentation/block/00-INDEX          |    2 +
 Documentation/block/io-controller.txt |  326 +++++++++++++++++++++++++++++++++
 2 files changed, 328 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/block/io-controller.txt

diff --git a/Documentation/block/00-INDEX b/Documentation/block/00-INDEX
index 961a051..dc8bf95 100644
--- a/Documentation/block/00-INDEX
+++ b/Documentation/block/00-INDEX
@@ -10,6 +10,8 @@ capability.txt
 	- Generic Block Device Capability (/sys/block/<disk>/capability)
 deadline-iosched.txt
 	- Deadline IO scheduler tunables
+io-controller.txt
+	- IO controller for provding hierarchical IO scheduling
 ioprio.txt
 	- Block io priorities (in CFQ scheduler)
 request.txt
diff --git a/Documentation/block/io-controller.txt b/Documentation/block/io-controller.txt
new file mode 100644
index 0000000..5669b81
--- /dev/null
+++ b/Documentation/block/io-controller.txt
@@ -0,0 +1,326 @@
+				IO Controller
+				=============
+
+Overview
+========
+
+This patchset implements a proportional weight IO controller. That is one
+can create cgroups and assign prio/weights to those cgroups and task group
+will get access to disk proportionate to the weight of the group.
+
+These patches modify elevator layer and individual IO schedulers to do
+IO control hence this io controller works only on block devices which use
+one of the standard io schedulers can not be used with any xyz logical block
+device.
+
+The assumption/thought behind modifying IO scheduler is that resource control
+is needed only on leaf nodes where the actual contention for resources is
+present and not on intertermediate logical block devices.
+
+Consider following hypothetical scenario. Lets say there are three physical
+disks, namely sda, sdb and sdc. Two logical volumes (lv0 and lv1) have been
+created on top of these. Some part of sdb is in lv0 and some part is in lv1.
+
+			    lv0      lv1
+			  /	\  /     \
+			sda      sdb      sdc
+
+Also consider following cgroup hierarchy
+
+				root
+				/   \
+			       A     B
+			      / \    / \
+			     T1 T2  T3  T4
+
+A and B are two cgroups and T1, T2, T3 and T4 are tasks with-in those cgroups.
+Assuming T1, T2, T3 and T4 are doing IO on lv0 and lv1. These tasks should
+get their fair share of bandwidth on disks sda, sdb and sdc. There is no
+IO control on intermediate logical block nodes (lv0, lv1).
+
+So if tasks T1 and T2 are doing IO on lv0 and T3 and T4 are doing IO on lv1
+only, there will not be any contetion for resources between group A and B if
+IO is going to sda or sdc. But if actual IO gets translated to disk sdb, then
+IO scheduler associated with the sdb will distribute disk bandwidth to
+group A and B proportionate to their weight.
+
+CFQ already has the notion of fairness and it provides differential disk
+access based on priority and class of the task. Just that it is flat and
+with cgroup stuff, it needs to be made hierarchical to achive a good
+hierarchical control on IO.
+
+Rest of the IO schedulers (noop, deadline and AS) don't have any notion
+of fairness among various threads. They maintain only one queue where all
+the IO gets queued (internally this queue is split in read and write queue
+for deadline and AS). With this patchset, now we maintain one queue per
+cgropu per device and then try to do fair queuing among those queues.
+
+One of the concerns raised with modifying IO schedulers was that we don't
+want to replicate the code in all the IO schedulers. These patches share
+the fair queuing code which has been moved to a common layer (elevator
+layer). Hence we don't end up replicating code across IO schedulers. Following
+diagram depicts the concept.
+
+			--------------------------------
+			| Elevator Layer + Fair Queuing |
+			--------------------------------
+			 |	     |	     |       |
+			NOOP     DEADLINE    AS     CFQ
+
+Design
+======
+This patchset primarily uses BFQ (Budget Fair Queuing) code to provide
+fairness among different IO queues. Fabio and Paolo implemented BFQ which uses
+B-WF2Q+ algorithm for fair queuing.
+
+Why BFQ?
+
+- Not sure if weighted round robin logic of CFQ can be easily extended for
+  hierarchical mode. One of the things is that we can not keep dividing
+  the time slice of parent group among childrens. Deeper we go in hierarchy
+  time slice will get smaller.
+
+  One of the ways to implement hierarchical support could be to keep track
+  of virtual time and service provided to queue/group and select a queue/group
+  for service based on any of the various available algoriths.
+
+  BFQ already had support for hierarchical scheduling, taking those patches
+  was easier.
+
+- BFQ was designed to provide tighter bounds/delay w.r.t service provided
+  to a queue. Delay/Jitter with BFQ is O(1).
+
+  Note: BFQ originally used amount of IO done (number of sectors) as notion
+        of service provided. IOW, it tried to provide fairness in terms of
+        actual IO done and not in terms of actual time disk access was
+	given to a queue.
+
+	This patcheset modified BFQ to provide fairness in time domain because
+	that's what CFQ does. So idea was try not to deviate too much from
+	the CFQ behavior initially.
+
+	Providing fairness in time domain makes accounting trciky because
+	due to command queueing, at one time there might be multiple requests
+	from different queues and there is no easy way to find out how much
+	disk time actually was consumed by the requests of a particular
+	queue. More about this in comments in source code.
+
+We have taken BFQ code as starting point for providing fairness among groups
+because it already contained lots of features which we required to implement
+hierarhical IO scheduling. With this patch set, I am not trying to ensure O(1)
+delay here as my goal is to provide fairness among groups. Most likely that
+will mean that latencies are not worse than what cfq currently provides (if
+not improved ones). Once fairness is ensured, one can look into  more in
+ensuring O(1) latencies.
+
+From data structure point of view, one can think of a tree per device, where
+io groups and io queues are hanging and are being scheduled using B-WF2Q+
+algorithm. io_queue, is end queue where requests are actually stored and
+dispatched from (like cfqq).
+
+These io queues are primarily created by and managed by end io schedulers
+depending on its semantics. For example, noop, deadline and AS ioschedulers
+keep one io queues per cgroup and cfqq keeps one io queue per io_context in
+a cgroup (apart from async queues).
+
+A request is mapped to an io group by elevator layer and which io queue it
+is mapped to with in group depends on ioscheduler. Currently "current" task
+is used to determine the cgroup (hence io group) of the request. Down the
+line we need to make use of bio-cgroup patches to map delayed writes to
+right group.
+
+Going back to old behavior
+==========================
+In new scheme of things essentially we are creating hierarchical fair
+queuing logic in elevator layer and chaning IO schedulers to make use of
+that logic so that end IO schedulers start supporting hierarchical scheduling.
+
+Elevator layer continues to support the old interfaces. So even if fair queuing
+is enabled at elevator layer, one can have both new hierchical scheduler as
+well as old non-hierarchical scheduler operating.
+
+Also noop, deadline and AS have option of enabling hierarchical scheduling.
+If it is selected, fair queuing is done in hierarchical manner. If hierarchical
+scheduling is disabled, noop, deadline and AS should retain their existing
+behavior.
+
+CFQ is the only exception where one can not disable fair queuing as it is
+needed for provding fairness among various threads even in non-hierarchical
+mode.
+
+Various user visible config options
+===================================
+CONFIG_IOSCHED_NOOP_HIER
+	- Enables hierchical fair queuing in noop. Not selecting this option
+	  leads to old behavior of noop.
+
+CONFIG_IOSCHED_DEADLINE_HIER
+	- Enables hierchical fair queuing in deadline. Not selecting this
+	  option leads to old behavior of deadline.
+
+CONFIG_IOSCHED_AS_HIER
+	- Enables hierchical fair queuing in AS. Not selecting this option
+	  leads to old behavior of AS.
+
+CONFIG_IOSCHED_CFQ_HIER
+	- Enables hierarchical fair queuing in CFQ. Not selecting this option
+	  still does fair queuing among various queus but it is flat and not
+	  hierarchical.
+
+CGROUP_BLKIO
+	- This option enables blkio-cgroup controller for IO tracking
+	  purposes. That means, by this controller one can attribute a write
+	  to the original cgroup and not assume that it belongs to submitting
+	  thread.
+
+CONFIG_TRACK_ASYNC_CONTEXT
+	- Currently CFQ attributes the writes to the submitting thread and
+	  caches the async queue pointer in the io context of the process.
+	  If this option is set, it tells cfq and elevator fair queuing logic
+	  that for async writes make use of IO tracking patches and attribute
+	  writes to original cgroup and not to write submitting thread.
+
+CONFIG_DEBUG_GROUP_IOSCHED
+	- Throws extra debug messages in blktrace output helpful in doing
+	  doing debugging in hierarchical setup.
+
+	- Also allows for export of extra debug statistics like group queue
+	  and dequeue statistics on device through cgroup interface.
+
+Config options selected automatically
+=====================================
+These config options are not user visible and are selected/deselected
+automatically based on IO scheduler configurations.
+
+CONFIG_ELV_FAIR_QUEUING
+	- Enables/Disables the fair queuing logic at elevator layer.
+
+CONFIG_GROUP_IOSCHED
+	- Enables/Disables hierarchical queuing and associated cgroup bits.
+
+HOWTO
+=====
+So far I have done very simple testing of running two dd threads in two
+different cgroups. Here is what you can do.
+
+- Enable hierarchical scheduling in io scheuduler of your choice (say cfq).
+	CONFIG_IOSCHED_CFQ_HIER=y
+
+- Enable IO tracking for async writes.
+	CONFIG_TRACK_ASYNC_CONTEXT=y
+
+  (This will automatically select CGROUP_BLKIO)
+
+- Compile and boot into kernel and mount IO controller and blkio io tracking
+  controller.
+
+	mount -t cgroup -o io,blkio none /cgroup
+
+- Create two cgroups
+	mkdir -p /cgroup/test1/ /cgroup/test2
+
+- Set weights of group test1 and test2
+	echo 1000 > /cgroup/test1/io.ioprio
+	echo 500 > /cgroup/test2/io.ioprio
+
+- Set "fairness" parameter to 1 at the disk you are testing.
+
+  echo 1 > /sys/block/<disk>/queue/fairness
+
+- Create two same size files (say 512MB each) on same disk (file1, file2) and
+  launch two dd threads in different cgroup to read those files. Make sure
+  right io scheduler is being used for the block device where files are
+  present (the one you compiled in hierarchical mode).
+
+	sync
+	echo 3 > /proc/sys/vm/drop_caches
+
+	dd if=/mnt/sdb/zerofile1 of=/dev/null &
+	echo $! > /cgroup/test1/tasks
+	cat /cgroup/test1/tasks
+
+	dd if=/mnt/sdb/zerofile2 of=/dev/null &
+	echo $! > /cgroup/test2/tasks
+	cat /cgroup/test2/tasks
+
+- At macro level, first dd should finish first. To get more precise data, keep
+  on looking at (with the help of script), at io.disk_time and io.disk_sectors
+  files of both test1 and test2 groups. This will tell how much disk time
+  (in milli seconds), each group got and how many secotors each group
+  dispatched to the disk. We provide fairness in terms of disk time, so
+  ideally io.disk_time of cgroups should be in proportion to the weight.
+  (It is hard to achieve though :-)).
+
+Details of cgroup files
+=======================
+- io.ioprio_class
+	- Specifies class of the cgroup (RT, BE, IDLE). This is default io
+	  class of the group on all the devices until and unless overridden by
+	  per device rule. (See io.policy).
+
+	  1 = RT; 2 = BE, 3 = IDLE
+
+- io.weight
+	- Specifies per cgroup weight. This is default weight of the group
+	  on all the devices until and unless overridden by per device rule.
+	  (See io.policy).
+
+- io.disk_time
+	- disk time allocated to cgroup per device in milliseconds. First
+	  two fields specify the major and minor number of the device and
+	  third field specifies the disk time allocated to group in
+	  milliseconds.
+
+- io.disk_sectors
+	- number of sectors transferred to/from disk by the group. First
+	  two fields specify the major and minor number of the device and
+	  third field specifies the number of sectors transferred by the
+	  group to/from the device.
+
+- io.disk_queue
+	- Debugging aid only enabled if CONFIG_DEBUG_GROUP_IOSCHED=y. This
+	  gives the statistics about how many a times a group was queued
+	  on service tree of the device. First two fields specify the major
+	  and minor number of the device and third field specifies the number
+	  of times a group was queued on a particular device.
+
+- io.disk_queue
+	- Debugging aid only enabled if CONFIG_DEBUG_GROUP_IOSCHED=y. This
+	  gives the statistics about how many a times a group was de-queued
+	  or removed from the service tree of the device. This basically gives
+	  and idea if we can generate enough IO to create continuously
+	  backlogged groups. First two fields specify the major and minor
+	  number of the device and third field specifies the number
+	  of times a group was de-queued on a particular device.
+
+- io.policy
+	- One can specify per cgroup per device rules using this interface.
+	  These rules override the default value of group weight and class as
+	  specified by io.weight and io.ioprio_class.
+
+	  Following is the format.
+
+	#echo DEV:weight:ioprio_class > /patch/to/cgroup/io.policy
+
+	weight=0 means removing a policy.
+
+	Examples:
+
+	Configure weight=300 ioprio_class=2 on /dev/hdb in this cgroup
+	# echo /dev/hdb:300:2 > io.policy
+	# cat io.policy
+	dev weight class
+	/dev/hdb 300 2
+
+	Configure weight=500 ioprio_class=1 on /dev/hda in this cgroup
+	# echo /dev/hda:500:1 > io.policy
+	# cat io.policy
+	dev weight class
+	/dev/hda 500 1
+	/dev/hdb 300 2
+
+	Remove the policy for /dev/hda in this cgroup
+	# echo /dev/hda:0:1 > io.policy
+	# cat io.policy
+	dev weight class
+	/dev/hdb 300 2
-- 
1.6.0.1

[PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Vivek Goyal]

This is common fair queuing code in elevator layer. This is controlled by
config option CONFIG_ELV_FAIR_QUEUING. This patch initially only introduces
flat fair queuing support where there is only one group, "root group" and all
the tasks belong to root group.

This elevator layer changes are backward compatible. That means any ioscheduler
using old interfaces will continue to work.

This code is essentially the CFQ code for fair queuing. The primary difference
is that flat rounding robin algorithm of CFQ has been replaced with BFQ (WF2Q+).

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Fabio Checconi <fabio-f9ZlEuEWxVeACYmtYXMKmw@public.gmane.org>
Signed-off-by: Paolo Valente <paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org>
Signed-off-by: Aristeu Rozanski <aris-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/Kconfig.iosched    |   13 +
 block/Makefile           |    1 +
 block/blk-sysfs.c        |   25 +
 block/elevator-fq.c      | 2078 ++++++++++++++++++++++++++++++++++++++++++++++
 block/elevator-fq.h      |  488 +++++++++++
 block/elevator.c         |   46 +-
 include/linux/blkdev.h   |    5 +
 include/linux/elevator.h |   51 ++
 8 files changed, 2696 insertions(+), 11 deletions(-)
 create mode 100644 block/elevator-fq.c
 create mode 100644 block/elevator-fq.h

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 7e803fc..3398134 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -2,6 +2,19 @@ if BLOCK
 
 menu "IO Schedulers"
 
+config ELV_FAIR_QUEUING
+	bool "Elevator Fair Queuing Support"
+	default n
+	---help---
+	  Traditionally only cfq had notion of multiple queues and it did
+	  fair queuing at its own. With the cgroups and need of controlling
+	  IO, now even the simple io schedulers like noop, deadline, as will
+	  have one queue per cgroup and will need hierarchical fair queuing.
+	  Instead of every io scheduler implementing its own fair queuing
+	  logic, this option enables fair queuing in elevator layer so that
+	  other ioschedulers can make use of it.
+	  If unsure, say N.
+
 config IOSCHED_NOOP
 	bool
 	default y
diff --git a/block/Makefile b/block/Makefile
index e9fa4dd..94bfc6e 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -15,3 +15,4 @@ obj-$(CONFIG_IOSCHED_CFQ)	+= cfq-iosched.o
 
 obj-$(CONFIG_BLOCK_COMPAT)	+= compat_ioctl.o
 obj-$(CONFIG_BLK_DEV_INTEGRITY)	+= blk-integrity.o
+obj-$(CONFIG_ELV_FAIR_QUEUING)	+= elevator-fq.o
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 3ff9bba..082a273 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -276,6 +276,26 @@ static struct queue_sysfs_entry queue_iostats_entry = {
 	.store = queue_iostats_store,
 };
 
+#ifdef CONFIG_ELV_FAIR_QUEUING
+static struct queue_sysfs_entry queue_slice_idle_entry = {
+	.attr = {.name = "slice_idle", .mode = S_IRUGO | S_IWUSR },
+	.show = elv_slice_idle_show,
+	.store = elv_slice_idle_store,
+};
+
+static struct queue_sysfs_entry queue_slice_sync_entry = {
+	.attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR },
+	.show = elv_slice_sync_show,
+	.store = elv_slice_sync_store,
+};
+
+static struct queue_sysfs_entry queue_slice_async_entry = {
+	.attr = {.name = "slice_async", .mode = S_IRUGO | S_IWUSR },
+	.show = elv_slice_async_show,
+	.store = elv_slice_async_store,
+};
+#endif
+
 static struct attribute *default_attrs[] = {
 	&queue_requests_entry.attr,
 	&queue_ra_entry.attr,
@@ -287,6 +307,11 @@ static struct attribute *default_attrs[] = {
 	&queue_nomerges_entry.attr,
 	&queue_rq_affinity_entry.attr,
 	&queue_iostats_entry.attr,
+#ifdef CONFIG_ELV_FAIR_QUEUING
+	&queue_slice_idle_entry.attr,
+	&queue_slice_sync_entry.attr,
+	&queue_slice_async_entry.attr,
+#endif
 	NULL,
 };
 
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
new file mode 100644
index 0000000..c5cc080
--- /dev/null
+++ b/block/elevator-fq.c
@@ -0,0 +1,2078 @@
+/*
+ * BFQ: Hierarchical B-WF2Q+ scheduler.
+ *
+ * Based on ideas and code from CFQ:
+ * Copyright (C) 2003 Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
+ *
+ * Copyright (C) 2008 Fabio Checconi <fabio-f9ZlEuEWxVeACYmtYXMKmw@public.gmane.org>
+ *		      Paolo Valente <paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org>
+ */
+
+#include <linux/blkdev.h>
+#include "elevator-fq.h"
+#include <linux/blktrace_api.h>
+
+/* Values taken from cfq */
+const int elv_slice_sync = HZ / 10;
+int elv_slice_async = HZ / 25;
+const int elv_slice_async_rq = 2;
+int elv_slice_idle = HZ / 125;
+static struct kmem_cache *elv_ioq_pool;
+
+#define ELV_SLICE_SCALE		(5)
+#define ELV_HW_QUEUE_MIN	(5)
+#define IO_SERVICE_TREE_INIT   ((struct io_service_tree)		\
+				{ RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
+
+static inline struct io_queue *elv_close_cooperator(struct request_queue *q,
+					struct io_queue *ioq, int probe);
+struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
+						 int extract);
+
+static inline int elv_prio_slice(struct elv_fq_data *efqd, int sync,
+					unsigned short prio)
+{
+	const int base_slice = efqd->elv_slice[sync];
+
+	WARN_ON(prio >= IOPRIO_BE_NR);
+
+	return base_slice + (base_slice/ELV_SLICE_SCALE * (4 - prio));
+}
+
+static inline int
+elv_prio_to_slice(struct elv_fq_data *efqd, struct io_queue *ioq)
+{
+	return elv_prio_slice(efqd, elv_ioq_sync(ioq), ioq->entity.ioprio);
+}
+
+/* Mainly the BFQ scheduling code Follows */
+
+/*
+ * Shift for timestamp calculations.  This actually limits the maximum
+ * service allowed in one timestamp delta (small shift values increase it),
+ * the maximum total weight that can be used for the queues in the system
+ * (big shift values increase it), and the period of virtual time wraparounds.
+ */
+#define WFQ_SERVICE_SHIFT	22
+
+/**
+ * bfq_gt - compare two timestamps.
+ * @a: first ts.
+ * @b: second ts.
+ *
+ * Return @a > @b, dealing with wrapping correctly.
+ */
+static inline int bfq_gt(bfq_timestamp_t a, bfq_timestamp_t b)
+{
+	return (s64)(a - b) > 0;
+}
+
+/**
+ * bfq_delta - map service into the virtual time domain.
+ * @service: amount of service.
+ * @weight: scale factor.
+ */
+static inline bfq_timestamp_t bfq_delta(bfq_service_t service,
+					bfq_weight_t weight)
+{
+	bfq_timestamp_t d = (bfq_timestamp_t)service << WFQ_SERVICE_SHIFT;
+
+	do_div(d, weight);
+	return d;
+}
+
+/**
+ * bfq_calc_finish - assign the finish time to an entity.
+ * @entity: the entity to act upon.
+ * @service: the service to be charged to the entity.
+ */
+static inline void bfq_calc_finish(struct io_entity *entity,
+				   bfq_service_t service)
+{
+	BUG_ON(entity->weight == 0);
+
+	entity->finish = entity->start + bfq_delta(service, entity->weight);
+}
+
+static inline struct io_queue *io_entity_to_ioq(struct io_entity *entity)
+{
+	struct io_queue *ioq = NULL;
+
+	BUG_ON(entity == NULL);
+	if (entity->my_sched_data == NULL)
+		ioq = container_of(entity, struct io_queue, entity);
+	return ioq;
+}
+
+/**
+ * bfq_entity_of - get an entity from a node.
+ * @node: the node field of the entity.
+ *
+ * Convert a node pointer to the relative entity.  This is used only
+ * to simplify the logic of some functions and not as the generic
+ * conversion mechanism because, e.g., in the tree walking functions,
+ * the check for a %NULL value would be redundant.
+ */
+static inline struct io_entity *bfq_entity_of(struct rb_node *node)
+{
+	struct io_entity *entity = NULL;
+
+	if (node != NULL)
+		entity = rb_entry(node, struct io_entity, rb_node);
+
+	return entity;
+}
+
+/**
+ * bfq_extract - remove an entity from a tree.
+ * @root: the tree root.
+ * @entity: the entity to remove.
+ */
+static inline void bfq_extract(struct rb_root *root, struct io_entity *entity)
+{
+	BUG_ON(entity->tree != root);
+
+	entity->tree = NULL;
+	rb_erase(&entity->rb_node, root);
+}
+
+/**
+ * bfq_idle_extract - extract an entity from the idle tree.
+ * @st: the service tree of the owning @entity.
+ * @entity: the entity being removed.
+ */
+static void bfq_idle_extract(struct io_service_tree *st,
+				struct io_entity *entity)
+{
+	struct rb_node *next;
+	struct io_queue *ioq = io_entity_to_ioq(entity);
+
+	BUG_ON(entity->tree != &st->idle);
+
+	if (entity == st->first_idle) {
+		next = rb_next(&entity->rb_node);
+		st->first_idle = bfq_entity_of(next);
+	}
+
+	if (entity == st->last_idle) {
+		next = rb_prev(&entity->rb_node);
+		st->last_idle = bfq_entity_of(next);
+	}
+
+	bfq_extract(&st->idle, entity);
+
+	/* Delete queue from idle list */
+	if (ioq)
+		list_del(&ioq->queue_list);
+}
+
+/**
+ * bfq_insert - generic tree insertion.
+ * @root: tree root.
+ * @entity: entity to insert.
+ *
+ * This is used for the idle and the active tree, since they are both
+ * ordered by finish time.
+ */
+static void bfq_insert(struct rb_root *root, struct io_entity *entity)
+{
+	struct io_entity *entry;
+	struct rb_node **node = &root->rb_node;
+	struct rb_node *parent = NULL;
+
+	BUG_ON(entity->tree != NULL);
+
+	while (*node != NULL) {
+		parent = *node;
+		entry = rb_entry(parent, struct io_entity, rb_node);
+
+		if (bfq_gt(entry->finish, entity->finish))
+			node = &parent->rb_left;
+		else
+			node = &parent->rb_right;
+	}
+
+	rb_link_node(&entity->rb_node, parent, node);
+	rb_insert_color(&entity->rb_node, root);
+
+	entity->tree = root;
+}
+
+/**
+ * bfq_update_min - update the min_start field of a entity.
+ * @entity: the entity to update.
+ * @node: one of its children.
+ *
+ * This function is called when @entity may store an invalid value for
+ * min_start due to updates to the active tree.  The function  assumes
+ * that the subtree rooted at @node (which may be its left or its right
+ * child) has a valid min_start value.
+ */
+static inline void bfq_update_min(struct io_entity *entity,
+					struct rb_node *node)
+{
+	struct io_entity *child;
+
+	if (node != NULL) {
+		child = rb_entry(node, struct io_entity, rb_node);
+		if (bfq_gt(entity->min_start, child->min_start))
+			entity->min_start = child->min_start;
+	}
+}
+
+/**
+ * bfq_update_active_node - recalculate min_start.
+ * @node: the node to update.
+ *
+ * @node may have changed position or one of its children may have moved,
+ * this function updates its min_start value.  The left and right subtrees
+ * are assumed to hold a correct min_start value.
+ */
+static inline void bfq_update_active_node(struct rb_node *node)
+{
+	struct io_entity *entity = rb_entry(node, struct io_entity, rb_node);
+
+	entity->min_start = entity->start;
+	bfq_update_min(entity, node->rb_right);
+	bfq_update_min(entity, node->rb_left);
+}
+
+/**
+ * bfq_update_active_tree - update min_start for the whole active tree.
+ * @node: the starting node.
+ *
+ * @node must be the deepest modified node after an update.  This function
+ * updates its min_start using the values held by its children, assuming
+ * that they did not change, and then updates all the nodes that may have
+ * changed in the path to the root.  The only nodes that may have changed
+ * are the ones in the path or their siblings.
+ */
+static void bfq_update_active_tree(struct rb_node *node)
+{
+	struct rb_node *parent;
+
+up:
+	bfq_update_active_node(node);
+
+	parent = rb_parent(node);
+	if (parent == NULL)
+		return;
+
+	if (node == parent->rb_left && parent->rb_right != NULL)
+		bfq_update_active_node(parent->rb_right);
+	else if (parent->rb_left != NULL)
+		bfq_update_active_node(parent->rb_left);
+
+	node = parent;
+	goto up;
+}
+
+/**
+ * bfq_active_insert - insert an entity in the active tree of its group/device.
+ * @st: the service tree of the entity.
+ * @entity: the entity being inserted.
+ *
+ * The active tree is ordered by finish time, but an extra key is kept
+ * per each node, containing the minimum value for the start times of
+ * its children (and the node itself), so it's possible to search for
+ * the eligible node with the lowest finish time in logarithmic time.
+ */
+static void bfq_active_insert(struct io_service_tree *st,
+					struct io_entity *entity)
+{
+	struct rb_node *node = &entity->rb_node;
+
+	bfq_insert(&st->active, entity);
+
+	if (node->rb_left != NULL)
+		node = node->rb_left;
+	else if (node->rb_right != NULL)
+		node = node->rb_right;
+
+	bfq_update_active_tree(node);
+}
+
+/**
+ * bfq_ioprio_to_weight - calc a weight from an ioprio.
+ * @ioprio: the ioprio value to convert.
+ */
+static bfq_weight_t bfq_ioprio_to_weight(int ioprio)
+{
+	WARN_ON(ioprio < 0 || ioprio >= IOPRIO_BE_NR);
+	return IOPRIO_BE_NR - ioprio;
+}
+
+void bfq_get_entity(struct io_entity *entity)
+{
+	struct io_queue *ioq = io_entity_to_ioq(entity);
+
+	if (ioq)
+		elv_get_ioq(ioq);
+}
+
+void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
+{
+	entity->ioprio = entity->new_ioprio;
+	entity->ioprio_class = entity->new_ioprio_class;
+	entity->sched_data = &iog->sched_data;
+}
+
+/**
+ * bfq_find_deepest - find the deepest node that an extraction can modify.
+ * @node: the node being removed.
+ *
+ * Do the first step of an extraction in an rb tree, looking for the
+ * node that will replace @node, and returning the deepest node that
+ * the following modifications to the tree can touch.  If @node is the
+ * last node in the tree return %NULL.
+ */
+static struct rb_node *bfq_find_deepest(struct rb_node *node)
+{
+	struct rb_node *deepest;
+
+	if (node->rb_right == NULL && node->rb_left == NULL)
+		deepest = rb_parent(node);
+	else if (node->rb_right == NULL)
+		deepest = node->rb_left;
+	else if (node->rb_left == NULL)
+		deepest = node->rb_right;
+	else {
+		deepest = rb_next(node);
+		if (deepest->rb_right != NULL)
+			deepest = deepest->rb_right;
+		else if (rb_parent(deepest) != node)
+			deepest = rb_parent(deepest);
+	}
+
+	return deepest;
+}
+
+/**
+ * bfq_active_extract - remove an entity from the active tree.
+ * @st: the service_tree containing the tree.
+ * @entity: the entity being removed.
+ */
+static void bfq_active_extract(struct io_service_tree *st,
+				struct io_entity *entity)
+{
+	struct rb_node *node;
+
+	node = bfq_find_deepest(&entity->rb_node);
+	bfq_extract(&st->active, entity);
+
+	if (node != NULL)
+		bfq_update_active_tree(node);
+}
+
+/**
+ * bfq_idle_insert - insert an entity into the idle tree.
+ * @st: the service tree containing the tree.
+ * @entity: the entity to insert.
+ */
+static void bfq_idle_insert(struct io_service_tree *st,
+					struct io_entity *entity)
+{
+	struct io_entity *first_idle = st->first_idle;
+	struct io_entity *last_idle = st->last_idle;
+	struct io_queue *ioq = io_entity_to_ioq(entity);
+
+	if (first_idle == NULL || bfq_gt(first_idle->finish, entity->finish))
+		st->first_idle = entity;
+	if (last_idle == NULL || bfq_gt(entity->finish, last_idle->finish))
+		st->last_idle = entity;
+
+	bfq_insert(&st->idle, entity);
+
+	/* Add this queue to idle list */
+	if (ioq)
+		list_add(&ioq->queue_list, &ioq->efqd->idle_list);
+}
+
+/**
+ * bfq_forget_entity - remove an entity from the wfq trees.
+ * @st: the service tree.
+ * @entity: the entity being removed.
+ *
+ * Update the device status and forget everything about @entity, putting
+ * the device reference to it, if it is a queue.  Entities belonging to
+ * groups are not refcounted.
+ */
+static void bfq_forget_entity(struct io_service_tree *st,
+				struct io_entity *entity)
+{
+	struct io_queue *ioq = NULL;
+
+	BUG_ON(!entity->on_st);
+	entity->on_st = 0;
+	st->wsum -= entity->weight;
+	ioq = io_entity_to_ioq(entity);
+	if (!ioq)
+		return;
+	elv_put_ioq(ioq);
+}
+
+/**
+ * bfq_put_idle_entity - release the idle tree ref of an entity.
+ * @st: service tree for the entity.
+ * @entity: the entity being released.
+ */
+void bfq_put_idle_entity(struct io_service_tree *st,
+				struct io_entity *entity)
+{
+	bfq_idle_extract(st, entity);
+	bfq_forget_entity(st, entity);
+}
+
+/**
+ * bfq_forget_idle - update the idle tree if necessary.
+ * @st: the service tree to act upon.
+ *
+ * To preserve the global O(log N) complexity we only remove one entry here;
+ * as the idle tree will not grow indefinitely this can be done safely.
+ */
+void bfq_forget_idle(struct io_service_tree *st)
+{
+	struct io_entity *first_idle = st->first_idle;
+	struct io_entity *last_idle = st->last_idle;
+
+	if (RB_EMPTY_ROOT(&st->active) && last_idle != NULL &&
+	    !bfq_gt(last_idle->finish, st->vtime)) {
+		/*
+		 * Active tree is empty. Pull back vtime to finish time of
+		 * last idle entity on idle tree.
+		 * Rational seems to be that it reduces the possibility of
+		 * vtime wraparound (bfq_gt(V-F) < 0).
+		 */
+		st->vtime = last_idle->finish;
+	}
+
+	if (first_idle != NULL && !bfq_gt(first_idle->finish, st->vtime))
+		bfq_put_idle_entity(st, first_idle);
+}
+
+
+static struct io_service_tree *
+__bfq_entity_update_prio(struct io_service_tree *old_st,
+				struct io_entity *entity)
+{
+	struct io_service_tree *new_st = old_st;
+	struct io_queue *ioq = io_entity_to_ioq(entity);
+
+	if (entity->ioprio_changed) {
+		entity->ioprio = entity->new_ioprio;
+		entity->ioprio_class = entity->new_ioprio_class;
+		entity->ioprio_changed = 0;
+
+		/*
+		 * Also update the scaled budget for ioq. Group will get the
+		 * updated budget once ioq is selected to run next.
+		 */
+		if (ioq) {
+			struct elv_fq_data *efqd = ioq->efqd;
+			entity->budget = elv_prio_to_slice(efqd, ioq);
+		}
+
+		old_st->wsum -= entity->weight;
+		entity->weight = bfq_ioprio_to_weight(entity->ioprio);
+
+		/*
+		 * NOTE: here we may be changing the weight too early,
+		 * this will cause unfairness.  The correct approach
+		 * would have required additional complexity to defer
+		 * weight changes to the proper time instants (i.e.,
+		 * when entity->finish <= old_st->vtime).
+		 */
+		new_st = io_entity_service_tree(entity);
+		new_st->wsum += entity->weight;
+
+		if (new_st != old_st)
+			entity->start = new_st->vtime;
+	}
+
+	return new_st;
+}
+
+/**
+ * __bfq_activate_entity - activate an entity.
+ * @entity: the entity being activated.
+ *
+ * Called whenever an entity is activated, i.e., it is not active and one
+ * of its children receives a new request, or has to be reactivated due to
+ * budget exhaustion.  It uses the current budget of the entity (and the
+ * service received if @entity is active) of the queue to calculate its
+ * timestamps.
+ */
+static void __bfq_activate_entity(struct io_entity *entity, int add_front)
+{
+	struct io_sched_data *sd = entity->sched_data;
+	struct io_service_tree *st = io_entity_service_tree(entity);
+
+	if (entity == sd->active_entity) {
+		BUG_ON(entity->tree != NULL);
+		/*
+		 * If we are requeueing the current entity we have
+		 * to take care of not charging to it service it has
+		 * not received.
+		 */
+		bfq_calc_finish(entity, entity->service);
+		entity->start = entity->finish;
+		sd->active_entity = NULL;
+	} else if (entity->tree == &st->active) {
+		/*
+		 * Requeueing an entity due to a change of some
+		 * next_active entity below it.  We reuse the old
+		 * start time.
+		 */
+		bfq_active_extract(st, entity);
+	} else if (entity->tree == &st->idle) {
+		/*
+		 * Must be on the idle tree, bfq_idle_extract() will
+		 * check for that.
+		 */
+		bfq_idle_extract(st, entity);
+		entity->start = bfq_gt(st->vtime, entity->finish) ?
+				       st->vtime : entity->finish;
+	} else {
+		/*
+		 * The finish time of the entity may be invalid, and
+		 * it is in the past for sure, otherwise the queue
+		 * would have been on the idle tree.
+		 */
+		entity->start = st->vtime;
+		st->wsum += entity->weight;
+		bfq_get_entity(entity);
+
+		BUG_ON(entity->on_st);
+		entity->on_st = 1;
+	}
+
+	st = __bfq_entity_update_prio(st, entity);
+	/*
+	 * This is to emulate cfq like functionality where preemption can
+	 * happen with-in same class, like sync queue preempting async queue
+	 * May be this is not a very good idea from fairness point of view
+	 * as preempting queue gains share. Keeping it for now.
+	 */
+	if (add_front) {
+		struct io_entity *next_entity;
+
+		/*
+		 * Determine the entity which will be dispatched next
+		 * Use sd->next_active once hierarchical patch is applied
+		 */
+		next_entity = bfq_lookup_next_entity(sd, 0);
+
+		if (next_entity && next_entity != entity) {
+			struct io_service_tree *new_st;
+			bfq_timestamp_t delta;
+
+			new_st = io_entity_service_tree(next_entity);
+
+			/*
+			 * At this point, both entities should belong to
+			 * same service tree as cross service tree preemption
+			 * is automatically taken care by algorithm
+			 */
+			BUG_ON(new_st != st);
+			entity->finish = next_entity->finish - 1;
+			delta = bfq_delta(entity->budget, entity->weight);
+			entity->start = entity->finish - delta;
+			if (bfq_gt(entity->start, st->vtime))
+				entity->start = st->vtime;
+		}
+	} else {
+		bfq_calc_finish(entity, entity->budget);
+	}
+	bfq_active_insert(st, entity);
+}
+
+/**
+ * bfq_activate_entity - activate an entity.
+ * @entity: the entity to activate.
+ */
+void bfq_activate_entity(struct io_entity *entity, int add_front)
+{
+	__bfq_activate_entity(entity, add_front);
+}
+
+/**
+ * __bfq_deactivate_entity - deactivate an entity from its service tree.
+ * @entity: the entity to deactivate.
+ * @requeue: if false, the entity will not be put into the idle tree.
+ *
+ * Deactivate an entity, independently from its previous state.  If the
+ * entity was not on a service tree just return, otherwise if it is on
+ * any scheduler tree, extract it from that tree, and if necessary
+ * and if the caller did not specify @requeue, put it on the idle tree.
+ *
+ */
+int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
+{
+	struct io_sched_data *sd = entity->sched_data;
+	struct io_service_tree *st = io_entity_service_tree(entity);
+	int was_active = entity == sd->active_entity;
+	int ret = 0;
+
+	if (!entity->on_st)
+		return 0;
+
+	BUG_ON(was_active && entity->tree != NULL);
+
+	if (was_active) {
+		bfq_calc_finish(entity, entity->service);
+		sd->active_entity = NULL;
+	} else if (entity->tree == &st->active)
+		bfq_active_extract(st, entity);
+	else if (entity->tree == &st->idle)
+		bfq_idle_extract(st, entity);
+	else if (entity->tree != NULL)
+		BUG();
+
+	if (!requeue || !bfq_gt(entity->finish, st->vtime))
+		bfq_forget_entity(st, entity);
+	else
+		bfq_idle_insert(st, entity);
+
+	BUG_ON(sd->active_entity == entity);
+
+	return ret;
+}
+
+/**
+ * bfq_deactivate_entity - deactivate an entity.
+ * @entity: the entity to deactivate.
+ * @requeue: true if the entity can be put on the idle tree
+ */
+void bfq_deactivate_entity(struct io_entity *entity, int requeue)
+{
+	__bfq_deactivate_entity(entity, requeue);
+}
+
+/**
+ * bfq_update_vtime - update vtime if necessary.
+ * @st: the service tree to act upon.
+ *
+ * If necessary update the service tree vtime to have at least one
+ * eligible entity, skipping to its start time.  Assumes that the
+ * active tree of the device is not empty.
+ *
+ * NOTE: this hierarchical implementation updates vtimes quite often,
+ * we may end up with reactivated tasks getting timestamps after a
+ * vtime skip done because we needed a ->first_active entity on some
+ * intermediate node.
+ */
+static void bfq_update_vtime(struct io_service_tree *st)
+{
+	struct io_entity *entry;
+	struct rb_node *node = st->active.rb_node;
+
+	entry = rb_entry(node, struct io_entity, rb_node);
+	if (bfq_gt(entry->min_start, st->vtime)) {
+		st->vtime = entry->min_start;
+		bfq_forget_idle(st);
+	}
+}
+
+/**
+ * bfq_first_active - find the eligible entity with the smallest finish time
+ * @st: the service tree to select from.
+ *
+ * This function searches the first schedulable entity, starting from the
+ * root of the tree and going on the left every time on this side there is
+ * a subtree with at least one eligible (start <= vtime) entity.  The path
+ * on the right is followed only if a) the left subtree contains no eligible
+ * entities and b) no eligible entity has been found yet.
+ */
+static struct io_entity *bfq_first_active_entity(struct io_service_tree *st)
+{
+	struct io_entity *entry, *first = NULL;
+	struct rb_node *node = st->active.rb_node;
+
+	while (node != NULL) {
+		entry = rb_entry(node, struct io_entity, rb_node);
+left:
+		if (!bfq_gt(entry->start, st->vtime))
+			first = entry;
+
+		BUG_ON(bfq_gt(entry->min_start, st->vtime));
+
+		if (node->rb_left != NULL) {
+			entry = rb_entry(node->rb_left,
+					 struct io_entity, rb_node);
+			if (!bfq_gt(entry->min_start, st->vtime)) {
+				node = node->rb_left;
+				goto left;
+			}
+		}
+		if (first != NULL)
+			break;
+		node = node->rb_right;
+	}
+
+	BUG_ON(first == NULL && !RB_EMPTY_ROOT(&st->active));
+	return first;
+}
+
+/**
+ * __bfq_lookup_next_entity - return the first eligible entity in @st.
+ * @st: the service tree.
+ *
+ * Update the virtual time in @st and return the first eligible entity
+ * it contains.
+ */
+static struct io_entity *__bfq_lookup_next_entity(struct io_service_tree *st)
+{
+	struct io_entity *entity;
+
+	if (RB_EMPTY_ROOT(&st->active))
+		return NULL;
+
+	bfq_update_vtime(st);
+	entity = bfq_first_active_entity(st);
+	BUG_ON(bfq_gt(entity->start, st->vtime));
+
+	return entity;
+}
+
+/**
+ * bfq_lookup_next_entity - return the first eligible entity in @sd.
+ * @sd: the sched_data.
+ * @extract: if true the returned entity will be also extracted from @sd.
+ *
+ * NOTE: since we cache the next_active entity at each level of the
+ * hierarchy, the complexity of the lookup can be decreased with
+ * absolutely no effort just returning the cached next_active value;
+ * we prefer to do full lookups to test the consistency of * the data
+ * structures.
+ */
+struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
+						 int extract)
+{
+	struct io_service_tree *st = sd->service_tree;
+	struct io_entity *entity;
+	int i;
+
+	/*
+	 * One can check for which will be next selected entity without
+	 * expiring the current one.
+	 */
+	BUG_ON(extract && sd->active_entity != NULL);
+
+	for (i = 0; i < IO_IOPRIO_CLASSES; i++, st++) {
+		entity = __bfq_lookup_next_entity(st);
+		if (entity != NULL) {
+			if (extract) {
+				bfq_active_extract(st, entity);
+				sd->active_entity = entity;
+			}
+			break;
+		}
+	}
+
+	return entity;
+}
+
+void entity_served(struct io_entity *entity, bfq_service_t served)
+{
+	struct io_service_tree *st;
+
+	st = io_entity_service_tree(entity);
+	entity->service += served;
+	BUG_ON(st->wsum == 0);
+	st->vtime += bfq_delta(served, st->wsum);
+	bfq_forget_idle(st);
+}
+
+/* Elevator fair queuing function */
+struct io_queue *rq_ioq(struct request *rq)
+{
+	return rq->ioq;
+}
+
+static inline struct io_queue *elv_active_ioq(struct elevator_queue *e)
+{
+	return e->efqd.active_queue;
+}
+
+void *elv_active_sched_queue(struct elevator_queue *e)
+{
+	return ioq_sched_queue(elv_active_ioq(e));
+}
+EXPORT_SYMBOL(elv_active_sched_queue);
+
+int elv_nr_busy_ioq(struct elevator_queue *e)
+{
+	return e->efqd.busy_queues;
+}
+EXPORT_SYMBOL(elv_nr_busy_ioq);
+
+int elv_nr_busy_rt_ioq(struct elevator_queue *e)
+{
+	return e->efqd.busy_rt_queues;
+}
+EXPORT_SYMBOL(elv_nr_busy_rt_ioq);
+
+int elv_hw_tag(struct elevator_queue *e)
+{
+	return e->efqd.hw_tag;
+}
+EXPORT_SYMBOL(elv_hw_tag);
+
+/* Helper functions for operating on elevator idle slice timer */
+int elv_mod_idle_slice_timer(struct elevator_queue *eq, unsigned long expires)
+{
+	struct elv_fq_data *efqd = &eq->efqd;
+
+	return mod_timer(&efqd->idle_slice_timer, expires);
+}
+EXPORT_SYMBOL(elv_mod_idle_slice_timer);
+
+int elv_del_idle_slice_timer(struct elevator_queue *eq)
+{
+	struct elv_fq_data *efqd = &eq->efqd;
+
+	return del_timer(&efqd->idle_slice_timer);
+}
+EXPORT_SYMBOL(elv_del_idle_slice_timer);
+
+unsigned int elv_get_slice_idle(struct elevator_queue *eq)
+{
+	return eq->efqd.elv_slice_idle;
+}
+EXPORT_SYMBOL(elv_get_slice_idle);
+
+void elv_ioq_served(struct io_queue *ioq, bfq_service_t served)
+{
+	entity_served(&ioq->entity, served);
+}
+
+/* Tells whether ioq is queued in root group or not */
+static inline int is_root_group_ioq(struct request_queue *q,
+					struct io_queue *ioq)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+
+	return (ioq->entity.sched_data == &efqd->root_group->sched_data);
+}
+
+/* Functions to show and store elv_idle_slice value through sysfs */
+ssize_t elv_slice_idle_show(struct request_queue *q, char *name)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	data = jiffies_to_msecs(efqd->elv_slice_idle);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+	return sprintf(name, "%d\n", data);
+}
+
+ssize_t elv_slice_idle_store(struct request_queue *q, const char *name,
+			  size_t count)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	char *p = (char *)name;
+
+	data = simple_strtoul(p, &p, 10);
+
+	if (data < 0)
+		data = 0;
+	else if (data > INT_MAX)
+		data = INT_MAX;
+
+	data = msecs_to_jiffies(data);
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	efqd->elv_slice_idle = data;
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	return count;
+}
+
+/* Functions to show and store elv_slice_sync value through sysfs */
+ssize_t elv_slice_sync_show(struct request_queue *q, char *name)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	data = efqd->elv_slice[1];
+	spin_unlock_irqrestore(q->queue_lock, flags);
+	return sprintf(name, "%d\n", data);
+}
+
+ssize_t elv_slice_sync_store(struct request_queue *q, const char *name,
+			  size_t count)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	char *p = (char *)name;
+
+	data = simple_strtoul(p, &p, 10);
+
+	if (data < 0)
+		data = 0;
+	/* 100ms is the limit for now*/
+	else if (data > 100)
+		data = 100;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	efqd->elv_slice[1] = data;
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	return count;
+}
+
+/* Functions to show and store elv_slice_async value through sysfs */
+ssize_t elv_slice_async_show(struct request_queue *q, char *name)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	data = efqd->elv_slice[0];
+	spin_unlock_irqrestore(q->queue_lock, flags);
+	return sprintf(name, "%d\n", data);
+}
+
+ssize_t elv_slice_async_store(struct request_queue *q, const char *name,
+			  size_t count)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	char *p = (char *)name;
+
+	data = simple_strtoul(p, &p, 10);
+
+	if (data < 0)
+		data = 0;
+	/* 100ms is the limit for now*/
+	else if (data > 100)
+		data = 100;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	efqd->elv_slice[0] = data;
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	return count;
+}
+
+void elv_schedule_dispatch(struct request_queue *q)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+
+	if (elv_nr_busy_ioq(q->elevator)) {
+		elv_log(efqd, "schedule dispatch");
+		kblockd_schedule_work(efqd->queue, &efqd->unplug_work);
+	}
+}
+EXPORT_SYMBOL(elv_schedule_dispatch);
+
+void elv_kick_queue(struct work_struct *work)
+{
+	struct elv_fq_data *efqd =
+		container_of(work, struct elv_fq_data, unplug_work);
+	struct request_queue *q = efqd->queue;
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	blk_start_queueing(q);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+void elv_shutdown_timer_wq(struct elevator_queue *e)
+{
+	del_timer_sync(&e->efqd.idle_slice_timer);
+	cancel_work_sync(&e->efqd.unplug_work);
+}
+EXPORT_SYMBOL(elv_shutdown_timer_wq);
+
+void elv_ioq_set_prio_slice(struct request_queue *q, struct io_queue *ioq)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+
+	ioq->slice_end = jiffies + ioq->entity.budget;
+	elv_log_ioq(efqd, ioq, "set_slice=%lu", ioq->entity.budget);
+}
+
+static void elv_ioq_update_io_thinktime(struct io_queue *ioq)
+{
+	struct elv_fq_data *efqd = ioq->efqd;
+	unsigned long elapsed = jiffies - ioq->last_end_request;
+	unsigned long ttime = min(elapsed, 2UL * efqd->elv_slice_idle);
+
+	ioq->ttime_samples = (7*ioq->ttime_samples + 256) / 8;
+	ioq->ttime_total = (7*ioq->ttime_total + 256*ttime) / 8;
+	ioq->ttime_mean = (ioq->ttime_total + 128) / ioq->ttime_samples;
+}
+
+/*
+ * Disable idle window if the process thinks too long.
+ * This idle flag can also be updated by io scheduler.
+ */
+static void elv_ioq_update_idle_window(struct elevator_queue *eq,
+				struct io_queue *ioq, struct request *rq)
+{
+	int old_idle, enable_idle;
+	struct elv_fq_data *efqd = ioq->efqd;
+
+	/*
+	 * Don't idle for async or idle io prio class
+	 */
+	if (!elv_ioq_sync(ioq) || elv_ioq_class_idle(ioq))
+		return;
+
+	enable_idle = old_idle = elv_ioq_idle_window(ioq);
+
+	if (!efqd->elv_slice_idle)
+		enable_idle = 0;
+	else if (ioq_sample_valid(ioq->ttime_samples)) {
+		if (ioq->ttime_mean > efqd->elv_slice_idle)
+			enable_idle = 0;
+		else
+			enable_idle = 1;
+	}
+
+	/*
+	 * From think time perspective idle should be enabled. Check with
+	 * io scheduler if it wants to disable idling based on additional
+	 * considrations like seek pattern.
+	 */
+	if (enable_idle) {
+		if (eq->ops->elevator_update_idle_window_fn)
+			enable_idle = eq->ops->elevator_update_idle_window_fn(
+						eq, ioq->sched_queue, rq);
+		if (!enable_idle)
+			elv_log_ioq(efqd, ioq, "iosched disabled idle");
+	}
+
+	if (old_idle != enable_idle) {
+		elv_log_ioq(efqd, ioq, "idle=%d", enable_idle);
+		if (enable_idle)
+			elv_mark_ioq_idle_window(ioq);
+		else
+			elv_clear_ioq_idle_window(ioq);
+	}
+}
+
+struct io_queue *elv_alloc_ioq(struct request_queue *q, gfp_t gfp_mask)
+{
+	struct io_queue *ioq = NULL;
+
+	ioq = kmem_cache_alloc_node(elv_ioq_pool, gfp_mask, q->node);
+	return ioq;
+}
+EXPORT_SYMBOL(elv_alloc_ioq);
+
+void elv_free_ioq(struct io_queue *ioq)
+{
+	kmem_cache_free(elv_ioq_pool, ioq);
+}
+EXPORT_SYMBOL(elv_free_ioq);
+
+int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq,
+			void *sched_queue, int ioprio_class, int ioprio,
+			int is_sync)
+{
+	struct elv_fq_data *efqd = &eq->efqd;
+	struct io_group *iog = io_lookup_io_group_current(efqd->queue);
+
+	RB_CLEAR_NODE(&ioq->entity.rb_node);
+	atomic_set(&ioq->ref, 0);
+	ioq->efqd = efqd;
+	elv_ioq_set_ioprio_class(ioq, ioprio_class);
+	elv_ioq_set_ioprio(ioq, ioprio);
+	ioq->pid = current->pid;
+	ioq->sched_queue = sched_queue;
+	if (is_sync && !elv_ioq_class_idle(ioq))
+		elv_mark_ioq_idle_window(ioq);
+	bfq_init_entity(&ioq->entity, iog);
+	ioq->entity.budget = elv_prio_to_slice(efqd, ioq);
+	return 0;
+}
+EXPORT_SYMBOL(elv_init_ioq);
+
+void elv_put_ioq(struct io_queue *ioq)
+{
+	struct elv_fq_data *efqd = ioq->efqd;
+	struct elevator_queue *e = container_of(efqd, struct elevator_queue,
+						efqd);
+
+	BUG_ON(atomic_read(&ioq->ref) <= 0);
+	if (!atomic_dec_and_test(&ioq->ref))
+		return;
+	BUG_ON(ioq->nr_queued);
+	BUG_ON(ioq->entity.tree != NULL);
+	BUG_ON(elv_ioq_busy(ioq));
+	BUG_ON(efqd->active_queue == ioq);
+
+	/* Can be called by outgoing elevator. Don't use q */
+	BUG_ON(!e->ops->elevator_free_sched_queue_fn);
+
+	e->ops->elevator_free_sched_queue_fn(e, ioq->sched_queue);
+	elv_log_ioq(efqd, ioq, "put_queue");
+	elv_free_ioq(ioq);
+}
+EXPORT_SYMBOL(elv_put_ioq);
+
+void elv_release_ioq(struct elevator_queue *e, struct io_queue **ioq_ptr)
+{
+	struct io_queue *ioq = *ioq_ptr;
+
+	if (ioq != NULL) {
+		/* Drop the reference taken by the io group */
+		elv_put_ioq(ioq);
+		*ioq_ptr = NULL;
+	}
+}
+
+/*
+ * Normally next io queue to be served is selected from the service tree.
+ * This function allows one to choose a specific io queue to run next
+ * out of order. This is primarily to accomodate the close_cooperator
+ * feature of cfq.
+ *
+ * Currently it is done only for root level as to begin with supporting
+ * close cooperator feature only for root group to make sure default
+ * cfq behavior in flat hierarchy is not changed.
+ */
+void elv_set_next_ioq(struct request_queue *q, struct io_queue *ioq)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+	struct io_entity *entity = &ioq->entity;
+	struct io_sched_data *sd = &efqd->root_group->sched_data;
+	struct io_service_tree *st = io_entity_service_tree(entity);
+
+	BUG_ON(efqd->active_queue != NULL || sd->active_entity != NULL);
+	BUG_ON(!efqd->busy_queues);
+	BUG_ON(sd != entity->sched_data);
+	BUG_ON(!st);
+
+	bfq_update_vtime(st);
+	bfq_active_extract(st, entity);
+	sd->active_entity = entity;
+	entity->service = 0;
+	elv_log_ioq(efqd, ioq, "set_next_ioq");
+}
+
+/* Get next queue for service. */
+struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+	struct io_entity *entity = NULL;
+	struct io_queue *ioq = NULL;
+	struct io_sched_data *sd;
+
+	/*
+	 * one can check for which queue will be selected next while having
+	 * one queue active. preempt logic uses it.
+	 */
+	BUG_ON(extract && efqd->active_queue != NULL);
+
+	if (!efqd->busy_queues)
+		return NULL;
+
+	sd = &efqd->root_group->sched_data;
+	if (extract)
+		entity = bfq_lookup_next_entity(sd, 1);
+	else
+		entity = bfq_lookup_next_entity(sd, 0);
+
+	BUG_ON(!entity);
+	if (extract)
+		entity->service = 0;
+	ioq = io_entity_to_ioq(entity);
+
+	return ioq;
+}
+
+/*
+ * coop tells that io scheduler selected a queue for us and we did not
+ * select the next queue based on fairness.
+ */
+static void __elv_set_active_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
+					int coop)
+{
+	struct request_queue *q = efqd->queue;
+
+	if (ioq) {
+		elv_log_ioq(efqd, ioq, "set_active, busy=%d",
+							efqd->busy_queues);
+		ioq->slice_end = 0;
+
+		elv_clear_ioq_wait_request(ioq);
+		elv_clear_ioq_must_dispatch(ioq);
+		elv_mark_ioq_slice_new(ioq);
+
+		del_timer(&efqd->idle_slice_timer);
+	}
+
+	efqd->active_queue = ioq;
+
+	/* Let iosched know if it wants to take some action */
+	if (ioq) {
+		if (q->elevator->ops->elevator_active_ioq_set_fn)
+			q->elevator->ops->elevator_active_ioq_set_fn(q,
+							ioq->sched_queue, coop);
+	}
+}
+
+/* Get and set a new active queue for service. */
+struct io_queue *elv_set_active_ioq(struct request_queue *q,
+						struct io_queue *ioq)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+	int coop = 0;
+
+	if (!ioq)
+		ioq = elv_get_next_ioq(q, 1);
+	else {
+		elv_set_next_ioq(q, ioq);
+		/*
+		 * io scheduler selected the next queue for us. Pass this
+		 * this info back to io scheudler. cfq currently uses it
+		 * to reset coop flag on the queue.
+		 */
+		coop = 1;
+	}
+	__elv_set_active_ioq(efqd, ioq, coop);
+	return ioq;
+}
+
+void elv_reset_active_ioq(struct elv_fq_data *efqd)
+{
+	struct request_queue *q = efqd->queue;
+	struct io_queue *ioq = elv_active_ioq(efqd->queue->elevator);
+
+	if (q->elevator->ops->elevator_active_ioq_reset_fn)
+		q->elevator->ops->elevator_active_ioq_reset_fn(q,
+							ioq->sched_queue);
+	efqd->active_queue = NULL;
+	del_timer(&efqd->idle_slice_timer);
+}
+
+void elv_activate_ioq(struct io_queue *ioq, int add_front)
+{
+	bfq_activate_entity(&ioq->entity, add_front);
+}
+
+void elv_deactivate_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
+					int requeue)
+{
+	if (ioq == efqd->active_queue)
+		elv_reset_active_ioq(efqd);
+
+	bfq_deactivate_entity(&ioq->entity, requeue);
+}
+
+/* Called when an inactive queue receives a new request. */
+void elv_add_ioq_busy(struct elv_fq_data *efqd, struct io_queue *ioq)
+{
+	BUG_ON(elv_ioq_busy(ioq));
+	BUG_ON(ioq == efqd->active_queue);
+	elv_log_ioq(efqd, ioq, "add to busy");
+	elv_activate_ioq(ioq, 0);
+	elv_mark_ioq_busy(ioq);
+	efqd->busy_queues++;
+	if (elv_ioq_class_rt(ioq))
+		efqd->busy_rt_queues++;
+}
+
+void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
+					int requeue)
+{
+	struct elv_fq_data *efqd = &e->efqd;
+
+	BUG_ON(!elv_ioq_busy(ioq));
+	BUG_ON(ioq->nr_queued);
+	elv_log_ioq(efqd, ioq, "del from busy");
+	elv_clear_ioq_busy(ioq);
+	BUG_ON(efqd->busy_queues == 0);
+	efqd->busy_queues--;
+	if (elv_ioq_class_rt(ioq))
+		efqd->busy_rt_queues--;
+
+	elv_deactivate_ioq(efqd, ioq, requeue);
+}
+
+/*
+ * Do the accounting. Determine how much service (in terms of time slices)
+ * current queue used and adjust the start, finish time of queue and vtime
+ * of the tree accordingly.
+ *
+ * Determining the service used in terms of time is tricky in certain
+ * situations. Especially when underlying device supports command queuing
+ * and requests from multiple queues can be there at same time, then it
+ * is not clear which queue consumed how much of disk time.
+ *
+ * To mitigate this problem, cfq starts the time slice of the queue only
+ * after first request from the queue has completed. This does not work
+ * very well if we expire the queue before we wait for first and more
+ * request to finish from the queue. For seeky queues, we will expire the
+ * queue after dispatching few requests without waiting and start dispatching
+ * from next queue.
+ *
+ * Not sure how to determine the time consumed by queue in such scenarios.
+ * Currently as a crude approximation, we are charging 25% of time slice
+ * for such cases. A better mechanism is needed for accurate accounting.
+ */
+void __elv_ioq_slice_expired(struct request_queue *q, struct io_queue *ioq)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+	struct io_entity *entity = &ioq->entity;
+	long slice_unused = 0, slice_used = 0, slice_overshoot = 0;
+
+	assert_spin_locked(q->queue_lock);
+	elv_log_ioq(efqd, ioq, "slice expired");
+
+	if (elv_ioq_wait_request(ioq))
+		del_timer(&efqd->idle_slice_timer);
+
+	elv_clear_ioq_wait_request(ioq);
+
+	/*
+	 * if ioq->slice_end = 0, that means a queue was expired before first
+	 * reuqest from the queue got completed. Of course we are not planning
+	 * to idle on the queue otherwise we would not have expired it.
+	 *
+	 * Charge for the 25% slice in such cases. This is not the best thing
+	 * to do but at the same time not very sure what's the next best
+	 * thing to do.
+	 *
+	 * This arises from that fact that we don't have the notion of
+	 * one queue being operational at one time. io scheduler can dispatch
+	 * requests from multiple queues in one dispatch round. Ideally for
+	 * more accurate accounting of exact disk time used by disk, one
+	 * should dispatch requests from only one queue and wait for all
+	 * the requests to finish. But this will reduce throughput.
+	 */
+	if (!ioq->slice_end)
+		slice_used = entity->budget/4;
+	else {
+		if (time_after(ioq->slice_end, jiffies)) {
+			slice_unused = ioq->slice_end - jiffies;
+			if (slice_unused == entity->budget) {
+				/*
+				 * queue got expired immediately after
+				 * completing first request. Charge 25% of
+				 * slice.
+				 */
+				slice_used = entity->budget/4;
+			} else
+				slice_used = entity->budget - slice_unused;
+		} else {
+			slice_overshoot = jiffies - ioq->slice_end;
+			slice_used = entity->budget + slice_overshoot;
+		}
+	}
+
+	elv_log_ioq(efqd, ioq, "sl_end=%lx, jiffies=%lx", ioq->slice_end,
+			jiffies);
+	elv_log_ioq(efqd, ioq, "sl_used=%ld, budget=%ld overshoot=%ld",
+				slice_used, entity->budget, slice_overshoot);
+	elv_ioq_served(ioq, slice_used);
+
+	BUG_ON(ioq != efqd->active_queue);
+	elv_reset_active_ioq(efqd);
+
+	if (!ioq->nr_queued)
+		elv_del_ioq_busy(q->elevator, ioq, 1);
+	else
+		elv_activate_ioq(ioq, 0);
+}
+EXPORT_SYMBOL(__elv_ioq_slice_expired);
+
+/*
+ *  Expire the ioq.
+ */
+void elv_ioq_slice_expired(struct request_queue *q)
+{
+	struct io_queue *ioq = elv_active_ioq(q->elevator);
+
+	if (ioq)
+		__elv_ioq_slice_expired(q, ioq);
+}
+
+/*
+ * Check if new_cfqq should preempt the currently active queue. Return 0 for
+ * no or if we aren't sure, a 1 will cause a preemption attempt.
+ */
+int elv_should_preempt(struct request_queue *q, struct io_queue *new_ioq,
+			struct request *rq)
+{
+	struct io_queue *ioq;
+	struct elevator_queue *eq = q->elevator;
+
+	ioq = elv_active_ioq(eq);
+
+	if (!ioq)
+		return 0;
+
+	if (elv_ioq_slice_used(ioq))
+		return 1;
+
+	if (elv_ioq_class_idle(new_ioq))
+		return 0;
+
+	if (elv_ioq_class_idle(ioq))
+		return 1;
+
+	/*
+	 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
+	 */
+	if (elv_ioq_class_rt(new_ioq) && !elv_ioq_class_rt(ioq))
+		return 1;
+
+	/*
+	 * Check with io scheduler if it has additional criterion based on
+	 * which it wants to preempt existing queue.
+	 */
+	if (eq->ops->elevator_should_preempt_fn)
+		return eq->ops->elevator_should_preempt_fn(q, new_ioq, rq);
+
+	return 0;
+}
+
+static void elv_preempt_queue(struct request_queue *q, struct io_queue *ioq)
+{
+	elv_log_ioq(&q->elevator->efqd, ioq, "preempt");
+	elv_ioq_slice_expired(q);
+
+	/*
+	 * Put the new queue at the front of the of the current list,
+	 * so we know that it will be selected next.
+	 */
+
+	elv_activate_ioq(ioq, 1);
+	elv_ioq_set_slice_end(ioq, 0);
+	elv_mark_ioq_slice_new(ioq);
+}
+
+void elv_ioq_request_add(struct request_queue *q, struct request *rq)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+	struct io_queue *ioq = rq->ioq;
+
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return;
+
+	BUG_ON(!efqd);
+	BUG_ON(!ioq);
+	efqd->rq_queued++;
+	ioq->nr_queued++;
+
+	if (!elv_ioq_busy(ioq))
+		elv_add_ioq_busy(efqd, ioq);
+
+	elv_ioq_update_io_thinktime(ioq);
+	elv_ioq_update_idle_window(q->elevator, ioq, rq);
+
+	if (ioq == elv_active_ioq(q->elevator)) {
+		/*
+		 * Remember that we saw a request from this process, but
+		 * don't start queuing just yet. Otherwise we risk seeing lots
+		 * of tiny requests, because we disrupt the normal plugging
+		 * and merging. If the request is already larger than a single
+		 * page, let it rip immediately. For that case we assume that
+		 * merging is already done. Ditto for a busy system that
+		 * has other work pending, don't risk delaying until the
+		 * idle timer unplug to continue working.
+		 */
+		if (elv_ioq_wait_request(ioq)) {
+			if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
+			    efqd->busy_queues > 1) {
+				del_timer(&efqd->idle_slice_timer);
+				blk_start_queueing(q);
+			}
+			elv_mark_ioq_must_dispatch(ioq);
+		}
+	} else if (elv_should_preempt(q, ioq, rq)) {
+		/*
+		 * not the active queue - expire current slice if it is
+		 * idle and has expired it's mean thinktime or this new queue
+		 * has some old slice time left and is of higher priority or
+		 * this new queue is RT and the current one is BE
+		 */
+		elv_preempt_queue(q, ioq);
+		blk_start_queueing(q);
+	}
+}
+
+void elv_idle_slice_timer(unsigned long data)
+{
+	struct elv_fq_data *efqd = (struct elv_fq_data *)data;
+	struct io_queue *ioq;
+	unsigned long flags;
+	struct request_queue *q = efqd->queue;
+
+	elv_log(efqd, "idle timer fired");
+
+	spin_lock_irqsave(q->queue_lock, flags);
+
+	ioq = efqd->active_queue;
+
+	if (ioq) {
+
+		/*
+		 * We saw a request before the queue expired, let it through
+		 */
+		if (elv_ioq_must_dispatch(ioq))
+			goto out_kick;
+
+		/*
+		 * expired
+		 */
+		if (elv_ioq_slice_used(ioq))
+			goto expire;
+
+		/*
+		 * only expire and reinvoke request handler, if there are
+		 * other queues with pending requests
+		 */
+		if (!elv_nr_busy_ioq(q->elevator))
+			goto out_cont;
+
+		/*
+		 * not expired and it has a request pending, let it dispatch
+		 */
+		if (ioq->nr_queued)
+			goto out_kick;
+	}
+expire:
+	elv_ioq_slice_expired(q);
+out_kick:
+	elv_schedule_dispatch(q);
+out_cont:
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+void elv_ioq_arm_slice_timer(struct request_queue *q)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+	struct io_queue *ioq = elv_active_ioq(q->elevator);
+	unsigned long sl;
+
+	BUG_ON(!ioq);
+
+	/*
+	 * SSD device without seek penalty, disable idling. But only do so
+	 * for devices that support queuing, otherwise we still have a problem
+	 * with sync vs async workloads.
+	 */
+	if (blk_queue_nonrot(q) && efqd->hw_tag)
+		return;
+
+	/*
+	 * still requests with the driver, don't idle
+	 */
+	if (efqd->rq_in_driver)
+		return;
+
+	/*
+	 * idle is disabled, either manually or by past process history
+	 */
+	if (!efqd->elv_slice_idle || !elv_ioq_idle_window(ioq))
+		return;
+
+	/*
+	 * may be iosched got its own idling logic. In that case io
+	 * schduler will take care of arming the timer, if need be.
+	 */
+	if (q->elevator->ops->elevator_arm_slice_timer_fn) {
+		q->elevator->ops->elevator_arm_slice_timer_fn(q,
+						ioq->sched_queue);
+	} else {
+		elv_mark_ioq_wait_request(ioq);
+		sl = efqd->elv_slice_idle;
+		mod_timer(&efqd->idle_slice_timer, jiffies + sl);
+		elv_log_ioq(efqd, ioq, "arm idle: %lu", sl);
+	}
+}
+
+void elv_free_idle_ioq_list(struct elevator_queue *e)
+{
+	struct io_queue *ioq, *n;
+	struct elv_fq_data *efqd = &e->efqd;
+
+	list_for_each_entry_safe(ioq, n, &efqd->idle_list, queue_list)
+		elv_deactivate_ioq(efqd, ioq, 0);
+}
+
+/* Common layer function to select the next queue to dispatch from */
+void *elv_fq_select_ioq(struct request_queue *q, int force)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+	struct io_queue *new_ioq = NULL, *ioq = elv_active_ioq(q->elevator);
+
+	if (!elv_nr_busy_ioq(q->elevator))
+		return NULL;
+
+	if (ioq == NULL)
+		goto new_queue;
+
+	/*
+	 * Force dispatch. Continue to dispatch from current queue as long
+	 * as it has requests.
+	 */
+	if (unlikely(force)) {
+		if (ioq->nr_queued)
+			goto keep_queue;
+		else
+			goto expire;
+	}
+
+	/*
+	 * The active queue has run out of time, expire it and select new.
+	 */
+	if (elv_ioq_slice_used(ioq) && !elv_ioq_must_dispatch(ioq))
+		goto expire;
+
+	/*
+	 * If we have a RT cfqq waiting, then we pre-empt the current non-rt
+	 * cfqq.
+	 */
+	if (!elv_ioq_class_rt(ioq) && efqd->busy_rt_queues) {
+		/*
+		 * We simulate this as cfqq timed out so that it gets to bank
+		 * the remaining of its time slice.
+		 */
+		elv_log_ioq(efqd, ioq, "preempt");
+		goto expire;
+	}
+
+	/*
+	 * The active queue has requests and isn't expired, allow it to
+	 * dispatch.
+	 */
+
+	if (ioq->nr_queued)
+		goto keep_queue;
+
+	/*
+	 * If another queue has a request waiting within our mean seek
+	 * distance, let it run.  The expire code will check for close
+	 * cooperators and put the close queue at the front of the service
+	 * tree.
+	 */
+	new_ioq = elv_close_cooperator(q, ioq, 0);
+	if (new_ioq)
+		goto expire;
+
+	/*
+	 * No requests pending. If the active queue still has requests in
+	 * flight or is idling for a new request, allow either of these
+	 * conditions to happen (or time out) before selecting a new queue.
+	 */
+
+	if (timer_pending(&efqd->idle_slice_timer) ||
+	    (elv_ioq_nr_dispatched(ioq) && elv_ioq_idle_window(ioq))) {
+		ioq = NULL;
+		goto keep_queue;
+	}
+
+expire:
+	elv_ioq_slice_expired(q);
+new_queue:
+	ioq = elv_set_active_ioq(q, new_ioq);
+keep_queue:
+	return ioq;
+}
+
+/* A request got removed from io_queue. Do the accounting */
+void elv_ioq_request_removed(struct elevator_queue *e, struct request *rq)
+{
+	struct io_queue *ioq;
+	struct elv_fq_data *efqd;
+
+	if (!elv_iosched_fair_queuing_enabled(e))
+		return;
+
+	ioq = rq->ioq;
+	BUG_ON(!ioq);
+	ioq->nr_queued--;
+
+	efqd = ioq->efqd;
+	BUG_ON(!efqd);
+	efqd->rq_queued--;
+
+	if (elv_ioq_busy(ioq) && (elv_active_ioq(e) != ioq) && !ioq->nr_queued)
+		elv_del_ioq_busy(e, ioq, 1);
+}
+
+/* A request got dispatched. Do the accounting. */
+void elv_fq_dispatched_request(struct elevator_queue *e, struct request *rq)
+{
+	struct io_queue *ioq = rq->ioq;
+
+	if (!elv_iosched_fair_queuing_enabled(e))
+		return;
+
+	BUG_ON(!ioq);
+	elv_ioq_request_dispatched(ioq);
+	elv_ioq_request_removed(e, rq);
+	elv_clear_ioq_must_dispatch(ioq);
+}
+
+void elv_fq_activate_rq(struct request_queue *q, struct request *rq)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return;
+
+	efqd->rq_in_driver++;
+	elv_log_ioq(efqd, rq_ioq(rq), "activate rq, drv=%d",
+						efqd->rq_in_driver);
+}
+
+void elv_fq_deactivate_rq(struct request_queue *q, struct request *rq)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return;
+
+	WARN_ON(!efqd->rq_in_driver);
+	efqd->rq_in_driver--;
+	elv_log_ioq(efqd, rq_ioq(rq), "deactivate rq, drv=%d",
+						efqd->rq_in_driver);
+}
+
+/*
+ * Update hw_tag based on peak queue depth over 50 samples under
+ * sufficient load.
+ */
+static void elv_update_hw_tag(struct elv_fq_data *efqd)
+{
+	if (efqd->rq_in_driver > efqd->rq_in_driver_peak)
+		efqd->rq_in_driver_peak = efqd->rq_in_driver;
+
+	if (efqd->rq_queued <= ELV_HW_QUEUE_MIN &&
+	    efqd->rq_in_driver <= ELV_HW_QUEUE_MIN)
+		return;
+
+	if (efqd->hw_tag_samples++ < 50)
+		return;
+
+	if (efqd->rq_in_driver_peak >= ELV_HW_QUEUE_MIN)
+		efqd->hw_tag = 1;
+	else
+		efqd->hw_tag = 0;
+
+	efqd->hw_tag_samples = 0;
+	efqd->rq_in_driver_peak = 0;
+}
+
+/*
+ * If ioscheduler has functionality of keeping track of close cooperator, check
+ * with it if it has got a closely co-operating queue.
+ */
+static inline struct io_queue *elv_close_cooperator(struct request_queue *q,
+					struct io_queue *ioq, int probe)
+{
+	struct elevator_queue *e = q->elevator;
+	struct io_queue *new_ioq = NULL;
+
+	/*
+	 * Currently this feature is supported only for flat hierarchy or
+	 * root group queues so that default cfq behavior is not changed.
+	 */
+	if (!is_root_group_ioq(q, ioq))
+		return NULL;
+
+	if (q->elevator->ops->elevator_close_cooperator_fn)
+		new_ioq = e->ops->elevator_close_cooperator_fn(q,
+						ioq->sched_queue, probe);
+
+	/* Only select co-operating queue if it belongs to root group */
+	if (new_ioq && !is_root_group_ioq(q, new_ioq))
+		return NULL;
+
+	return new_ioq;
+}
+
+/* A request got completed from io_queue. Do the accounting. */
+void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
+{
+	const int sync = rq_is_sync(rq);
+	struct io_queue *ioq;
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return;
+
+	ioq = rq->ioq;
+
+	elv_log_ioq(efqd, ioq, "complete");
+
+	elv_update_hw_tag(efqd);
+
+	WARN_ON(!efqd->rq_in_driver);
+	WARN_ON(!ioq->dispatched);
+	efqd->rq_in_driver--;
+	ioq->dispatched--;
+
+	if (sync)
+		ioq->last_end_request = jiffies;
+
+	/*
+	 * If this is the active queue, check if it needs to be expired,
+	 * or if we want to idle in case it has no pending requests.
+	 */
+
+	if (elv_active_ioq(q->elevator) == ioq) {
+		if (elv_ioq_slice_new(ioq)) {
+			elv_ioq_set_prio_slice(q, ioq);
+			elv_clear_ioq_slice_new(ioq);
+		}
+		/*
+		 * If there are no requests waiting in this queue, and
+		 * there are other queues ready to issue requests, AND
+		 * those other queues are issuing requests within our
+		 * mean seek distance, give them a chance to run instead
+		 * of idling.
+		 */
+		if (elv_ioq_slice_used(ioq) || elv_ioq_class_idle(ioq))
+			elv_ioq_slice_expired(q);
+		else if (!ioq->nr_queued && !elv_close_cooperator(q, ioq, 1)
+			 && sync && !rq_noidle(rq))
+			elv_ioq_arm_slice_timer(q);
+	}
+
+	if (!efqd->rq_in_driver)
+		elv_schedule_dispatch(q);
+}
+
+struct io_group *io_lookup_io_group_current(struct request_queue *q)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+
+	return efqd->root_group;
+}
+EXPORT_SYMBOL(io_lookup_io_group_current);
+
+void *io_group_async_queue_prio(struct io_group *iog, int ioprio_class,
+					int ioprio)
+{
+	struct io_queue *ioq = NULL;
+
+	switch (ioprio_class) {
+	case IOPRIO_CLASS_RT:
+		ioq = iog->async_queue[0][ioprio];
+		break;
+	case IOPRIO_CLASS_BE:
+		ioq = iog->async_queue[1][ioprio];
+		break;
+	case IOPRIO_CLASS_IDLE:
+		ioq = iog->async_idle_queue;
+		break;
+	default:
+		BUG();
+	}
+
+	if (ioq)
+		return ioq->sched_queue;
+	return NULL;
+}
+EXPORT_SYMBOL(io_group_async_queue_prio);
+
+void io_group_set_async_queue(struct io_group *iog, int ioprio_class,
+					int ioprio, struct io_queue *ioq)
+{
+	switch (ioprio_class) {
+	case IOPRIO_CLASS_RT:
+		iog->async_queue[0][ioprio] = ioq;
+		break;
+	case IOPRIO_CLASS_BE:
+		iog->async_queue[1][ioprio] = ioq;
+		break;
+	case IOPRIO_CLASS_IDLE:
+		iog->async_idle_queue = ioq;
+		break;
+	default:
+		BUG();
+	}
+
+	/*
+	 * Take the group reference and pin the queue. Group exit will
+	 * clean it up
+	 */
+	elv_get_ioq(ioq);
+}
+EXPORT_SYMBOL(io_group_set_async_queue);
+
+/*
+ * Release all the io group references to its async queues.
+ */
+void io_put_io_group_queues(struct elevator_queue *e, struct io_group *iog)
+{
+	int i, j;
+
+	for (i = 0; i < 2; i++)
+		for (j = 0; j < IOPRIO_BE_NR; j++)
+			elv_release_ioq(e, &iog->async_queue[i][j]);
+
+	/* Free up async idle queue */
+	elv_release_ioq(e, &iog->async_idle_queue);
+}
+
+struct io_group *io_alloc_root_group(struct request_queue *q,
+					struct elevator_queue *e, void *key)
+{
+	struct io_group *iog;
+	int i;
+
+	iog = kmalloc_node(sizeof(*iog), GFP_KERNEL | __GFP_ZERO, q->node);
+	if (iog == NULL)
+		return NULL;
+
+	for (i = 0; i < IO_IOPRIO_CLASSES; i++)
+		iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
+
+	return iog;
+}
+
+void io_free_root_group(struct elevator_queue *e)
+{
+	struct io_group *iog = e->efqd.root_group;
+	io_put_io_group_queues(e, iog);
+	kfree(iog);
+}
+
+static void elv_slab_kill(void)
+{
+	/*
+	 * Caller already ensured that pending RCU callbacks are completed,
+	 * so we should have no busy allocations at this point.
+	 */
+	if (elv_ioq_pool)
+		kmem_cache_destroy(elv_ioq_pool);
+}
+
+static int __init elv_slab_setup(void)
+{
+	elv_ioq_pool = KMEM_CACHE(io_queue, 0);
+	if (!elv_ioq_pool)
+		goto fail;
+
+	return 0;
+fail:
+	elv_slab_kill();
+	return -ENOMEM;
+}
+
+/* Initialize fair queueing data associated with elevator */
+int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e)
+{
+	struct io_group *iog;
+	struct elv_fq_data *efqd = &e->efqd;
+
+	if (!elv_iosched_fair_queuing_enabled(e))
+		return 0;
+
+	iog = io_alloc_root_group(q, e, efqd);
+	if (iog == NULL)
+		return 1;
+
+	efqd->root_group = iog;
+	efqd->queue = q;
+
+	init_timer(&efqd->idle_slice_timer);
+	efqd->idle_slice_timer.function = elv_idle_slice_timer;
+	efqd->idle_slice_timer.data = (unsigned long) efqd;
+
+	INIT_WORK(&efqd->unplug_work, elv_kick_queue);
+
+	INIT_LIST_HEAD(&efqd->idle_list);
+
+	efqd->elv_slice[0] = elv_slice_async;
+	efqd->elv_slice[1] = elv_slice_sync;
+	efqd->elv_slice_idle = elv_slice_idle;
+	efqd->hw_tag = 1;
+
+	return 0;
+}
+
+/*
+ * elv_exit_fq_data is called before we call elevator_exit_fn. Before
+ * we ask elevator to cleanup its queues, we do the cleanup here so
+ * that all the group and idle tree references to ioq are dropped. Later
+ * during elevator cleanup, ioc reference will be dropped which will lead
+ * to removal of ioscheduler queue as well as associated ioq object.
+ */
+void elv_exit_fq_data(struct elevator_queue *e)
+{
+	struct elv_fq_data *efqd = &e->efqd;
+	struct request_queue *q = efqd->queue;
+
+	if (!elv_iosched_fair_queuing_enabled(e))
+		return;
+
+	elv_shutdown_timer_wq(e);
+
+	spin_lock_irq(q->queue_lock);
+	/* This should drop all the idle tree references of ioq */
+	elv_free_idle_ioq_list(e);
+	spin_unlock_irq(q->queue_lock);
+
+	elv_shutdown_timer_wq(e);
+
+	BUG_ON(timer_pending(&efqd->idle_slice_timer));
+	io_free_root_group(e);
+}
+
+/*
+ * This is called after the io scheduler has cleaned up its data structres.
+ * I don't think that this function is required. Right now just keeping it
+ * because cfq cleans up timer and work queue again after freeing up
+ * io contexts. To me io scheduler has already been drained out, and all
+ * the active queue have already been expired so time and work queue should
+ * not been activated during cleanup process.
+ *
+ * Keeping it here for the time being. Will get rid of it later.
+ */
+void elv_exit_fq_data_post(struct elevator_queue *e)
+{
+	struct elv_fq_data *efqd = &e->efqd;
+
+	if (!elv_iosched_fair_queuing_enabled(e))
+		return;
+
+	elv_shutdown_timer_wq(e);
+	BUG_ON(timer_pending(&efqd->idle_slice_timer));
+}
+
+
+static int __init elv_fq_init(void)
+{
+	if (elv_slab_setup())
+		return -ENOMEM;
+
+	/* could be 0 on HZ < 1000 setups */
+
+	if (!elv_slice_async)
+		elv_slice_async = 1;
+
+	if (!elv_slice_idle)
+		elv_slice_idle = 1;
+
+	return 0;
+}
+
+module_init(elv_fq_init);
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
new file mode 100644
index 0000000..3bea279
--- /dev/null
+++ b/block/elevator-fq.h
@@ -0,0 +1,488 @@
+/*
+ * BFQ: data structures and common functions prototypes.
+ *
+ * Based on ideas and code from CFQ:
+ * Copyright (C) 2003 Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
+ *
+ * Copyright (C) 2008 Fabio Checconi <fabio-f9ZlEuEWxVeACYmtYXMKmw@public.gmane.org>
+ *		      Paolo Valente <paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org>
+ */
+
+#include <linux/blkdev.h>
+
+#ifndef _BFQ_SCHED_H
+#define _BFQ_SCHED_H
+
+#define IO_IOPRIO_CLASSES	3
+
+typedef u64 bfq_timestamp_t;
+typedef unsigned long bfq_weight_t;
+typedef unsigned long bfq_service_t;
+struct io_entity;
+struct io_queue;
+
+#ifdef CONFIG_ELV_FAIR_QUEUING
+
+/**
+ * struct bfq_service_tree - per ioprio_class service tree.
+ * @active: tree for active entities (i.e., those backlogged).
+ * @idle: tree for idle entities (i.e., those not backlogged, with V <= F_i).
+ * @first_idle: idle entity with minimum F_i.
+ * @last_idle: idle entity with maximum F_i.
+ * @vtime: scheduler virtual time.
+ * @wsum: scheduler weight sum; active and idle entities contribute to it.
+ *
+ * Each service tree represents a B-WF2Q+ scheduler on its own.  Each
+ * ioprio_class has its own independent scheduler, and so its own
+ * bfq_service_tree.  All the fields are protected by the queue lock
+ * of the containing efqd.
+ */
+struct io_service_tree {
+	struct rb_root active;
+	struct rb_root idle;
+
+	struct io_entity *first_idle;
+	struct io_entity *last_idle;
+
+	bfq_timestamp_t vtime;
+	bfq_weight_t wsum;
+};
+
+/**
+ * struct bfq_sched_data - multi-class scheduler.
+ * @active_entity: entity under service.
+ * @next_active: head-of-the-line entity in the scheduler.
+ * @service_tree: array of service trees, one per ioprio_class.
+ *
+ * bfq_sched_data is the basic scheduler queue.  It supports three
+ * ioprio_classes, and can be used either as a toplevel queue or as
+ * an intermediate queue on a hierarchical setup.
+ * @next_active points to the active entity of the sched_data service
+ * trees that will be scheduled next.
+ *
+ * The supported ioprio_classes are the same as in CFQ, in descending
+ * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
+ * Requests from higher priority queues are served before all the
+ * requests from lower priority queues; among requests of the same
+ * queue requests are served according to B-WF2Q+.
+ * All the fields are protected by the queue lock of the containing bfqd.
+ */
+struct io_sched_data {
+	struct io_entity *active_entity;
+	struct io_service_tree service_tree[IO_IOPRIO_CLASSES];
+};
+
+/**
+ * struct bfq_entity - schedulable entity.
+ * @rb_node: service_tree member.
+ * @on_st: flag, true if the entity is on a tree (either the active or
+ *         the idle one of its service_tree).
+ * @finish: B-WF2Q+ finish timestamp (aka F_i).
+ * @start: B-WF2Q+ start timestamp (aka S_i).
+ * @tree: tree the entity is enqueued into; %NULL if not on a tree.
+ * @min_start: minimum start time of the (active) subtree rooted at
+ *             this entity; used for O(log N) lookups into active trees.
+ * @service: service received during the last round of service.
+ * @budget: budget used to calculate F_i; F_i = S_i + @budget / @weight.
+ * @weight: weight of the queue, calculated as IOPRIO_BE_NR - @ioprio.
+ * @parent: parent entity, for hierarchical scheduling.
+ * @my_sched_data: for non-leaf nodes in the cgroup hierarchy, the
+ *                 associated scheduler queue, %NULL on leaf nodes.
+ * @sched_data: the scheduler queue this entity belongs to.
+ * @ioprio: the ioprio in use.
+ * @new_ioprio: when an ioprio change is requested, the new ioprio value
+ * @ioprio_class: the ioprio_class in use.
+ * @new_ioprio_class: when an ioprio_class change is requested, the new
+ *                    ioprio_class value.
+ * @ioprio_changed: flag, true when the user requested an ioprio or
+ *                  ioprio_class change.
+ *
+ * A bfq_entity is used to represent either a bfq_queue (leaf node in the
+ * cgroup hierarchy) or a bfq_group into the upper level scheduler.  Each
+ * entity belongs to the sched_data of the parent group in the cgroup
+ * hierarchy.  Non-leaf entities have also their own sched_data, stored
+ * in @my_sched_data.
+ *
+ * Each entity stores independently its priority values; this would allow
+ * different weights on different devices, but this functionality is not
+ * exported to userspace by now.  Priorities are updated lazily, first
+ * storing the new values into the new_* fields, then setting the
+ * @ioprio_changed flag.  As soon as there is a transition in the entity
+ * state that allows the priority update to take place the effective and
+ * the requested priority values are synchronized.
+ *
+ * The weight value is calculated from the ioprio to export the same
+ * interface as CFQ.  When dealing with ``well-behaved'' queues (i.e.,
+ * queues that do not spend too much time to consume their budget and
+ * have true sequential behavior, and when there are no external factors
+ * breaking anticipation) the relative weights at each level of the
+ * cgroups hierarchy should be guaranteed.
+ * All the fields are protected by the queue lock of the containing bfqd.
+ */
+struct io_entity {
+	struct rb_node rb_node;
+
+	int on_st;
+
+	bfq_timestamp_t finish;
+	bfq_timestamp_t start;
+
+	struct rb_root *tree;
+
+	bfq_timestamp_t min_start;
+
+	bfq_service_t service, budget;
+	bfq_weight_t weight;
+
+	struct io_entity *parent;
+
+	struct io_sched_data *my_sched_data;
+	struct io_sched_data *sched_data;
+
+	unsigned short ioprio, new_ioprio;
+	unsigned short ioprio_class, new_ioprio_class;
+
+	int ioprio_changed;
+};
+
+/*
+ * A common structure embedded by every io scheduler into their respective
+ * queue structure.
+ */
+struct io_queue {
+	struct io_entity entity;
+	atomic_t ref;
+	unsigned int flags;
+
+	/* Pointer to generic elevator data structure */
+	struct elv_fq_data *efqd;
+	struct list_head queue_list;
+	pid_t pid;
+
+	/* Number of requests queued on this io queue */
+	unsigned long nr_queued;
+
+	/* Requests dispatched from this queue */
+	int dispatched;
+
+	/* Keep a track of think time of processes in this queue */
+	unsigned long last_end_request;
+	unsigned long ttime_total;
+	unsigned long ttime_samples;
+	unsigned long ttime_mean;
+
+	unsigned long slice_end;
+
+	/* Pointer to io scheduler's queue */
+	void *sched_queue;
+};
+
+struct io_group {
+	struct io_sched_data sched_data;
+
+	/* async_queue and idle_queue are used only for cfq */
+	struct io_queue *async_queue[2][IOPRIO_BE_NR];
+	struct io_queue *async_idle_queue;
+};
+
+struct elv_fq_data {
+	struct io_group *root_group;
+
+	/* List of io queues on idle tree. */
+	struct list_head idle_list;
+
+	struct request_queue *queue;
+	unsigned int busy_queues;
+	/*
+	 * Used to track any pending rt requests so we can pre-empt current
+	 * non-RT cfqq in service when this value is non-zero.
+	 */
+	unsigned int busy_rt_queues;
+
+	/* Number of requests queued */
+	int rq_queued;
+
+	/* Pointer to the ioscheduler queue being served */
+	void *active_queue;
+
+	int rq_in_driver;
+	int hw_tag;
+	int hw_tag_samples;
+	int rq_in_driver_peak;
+
+	/*
+	 * elevator fair queuing layer has the capability to provide idling
+	 * for ensuring fairness for processes doing dependent reads.
+	 * This might be needed to ensure fairness among two processes doing
+	 * synchronous reads in two different cgroups. noop and deadline don't
+	 * have any notion of anticipation/idling. As of now, these are the
+	 * users of this functionality.
+	 */
+	unsigned int elv_slice_idle;
+	struct timer_list idle_slice_timer;
+	struct work_struct unplug_work;
+
+	unsigned int elv_slice[2];
+};
+
+extern int elv_slice_idle;
+extern int elv_slice_async;
+
+/* Logging facilities. */
+#define elv_log_ioq(efqd, ioq, fmt, args...) \
+	blk_add_trace_msg((efqd)->queue, "elv%d%c " fmt, (ioq)->pid,	\
+				elv_ioq_sync(ioq) ? 'S' : 'A', ##args)
+
+#define elv_log(efqd, fmt, args...) \
+	blk_add_trace_msg((efqd)->queue, "elv " fmt, ##args)
+
+#define ioq_sample_valid(samples)   ((samples) > 80)
+
+/* Some shared queue flag manipulation functions among elevators */
+
+enum elv_queue_state_flags {
+	ELV_QUEUE_FLAG_busy = 0,          /* has requests or is under service */
+	ELV_QUEUE_FLAG_sync,              /* synchronous queue */
+	ELV_QUEUE_FLAG_idle_window,	  /* elevator slice idling enabled */
+	ELV_QUEUE_FLAG_wait_request,	  /* waiting for a request */
+	ELV_QUEUE_FLAG_must_dispatch,	  /* must be allowed a dispatch */
+	ELV_QUEUE_FLAG_slice_new,	  /* no requests dispatched in slice */
+	ELV_QUEUE_FLAG_NR,
+};
+
+#define ELV_IO_QUEUE_FLAG_FNS(name)					\
+static inline void elv_mark_ioq_##name(struct io_queue *ioq)		\
+{                                                                       \
+	(ioq)->flags |= (1 << ELV_QUEUE_FLAG_##name);			\
+}                                                                       \
+static inline void elv_clear_ioq_##name(struct io_queue *ioq)		\
+{                                                                       \
+	(ioq)->flags &= ~(1 << ELV_QUEUE_FLAG_##name);			\
+}                                                                       \
+static inline int elv_ioq_##name(struct io_queue *ioq)         		\
+{                                                                       \
+	return ((ioq)->flags & (1 << ELV_QUEUE_FLAG_##name)) != 0;	\
+}
+
+ELV_IO_QUEUE_FLAG_FNS(busy)
+ELV_IO_QUEUE_FLAG_FNS(sync)
+ELV_IO_QUEUE_FLAG_FNS(wait_request)
+ELV_IO_QUEUE_FLAG_FNS(must_dispatch)
+ELV_IO_QUEUE_FLAG_FNS(idle_window)
+ELV_IO_QUEUE_FLAG_FNS(slice_new)
+
+static inline struct io_service_tree *
+io_entity_service_tree(struct io_entity *entity)
+{
+	struct io_sched_data *sched_data = entity->sched_data;
+	unsigned int idx = entity->ioprio_class - 1;
+
+	BUG_ON(idx >= IO_IOPRIO_CLASSES);
+	BUG_ON(sched_data == NULL);
+
+	return sched_data->service_tree + idx;
+}
+
+/* A request got dispatched from the io_queue. Do the accounting. */
+static inline void elv_ioq_request_dispatched(struct io_queue *ioq)
+{
+	ioq->dispatched++;
+}
+
+static inline int elv_ioq_slice_used(struct io_queue *ioq)
+{
+	if (elv_ioq_slice_new(ioq))
+		return 0;
+	if (time_before(jiffies, ioq->slice_end))
+		return 0;
+
+	return 1;
+}
+
+/* How many request are currently dispatched from the queue */
+static inline int elv_ioq_nr_dispatched(struct io_queue *ioq)
+{
+	return ioq->dispatched;
+}
+
+/* How many request are currently queued in the queue */
+static inline int elv_ioq_nr_queued(struct io_queue *ioq)
+{
+	return ioq->nr_queued;
+}
+
+static inline pid_t elv_ioq_pid(struct io_queue *ioq)
+{
+	return ioq->pid;
+}
+
+static inline unsigned long elv_ioq_ttime_mean(struct io_queue *ioq)
+{
+	return ioq->ttime_mean;
+}
+
+static inline unsigned long elv_ioq_sample_valid(struct io_queue *ioq)
+{
+	return ioq_sample_valid(ioq->ttime_samples);
+}
+
+static inline void elv_get_ioq(struct io_queue *ioq)
+{
+	atomic_inc(&ioq->ref);
+}
+
+static inline void elv_ioq_set_slice_end(struct io_queue *ioq,
+						unsigned long slice_end)
+{
+	ioq->slice_end = slice_end;
+}
+
+static inline int elv_ioq_class_idle(struct io_queue *ioq)
+{
+	return ioq->entity.ioprio_class == IOPRIO_CLASS_IDLE;
+}
+
+static inline int elv_ioq_class_rt(struct io_queue *ioq)
+{
+	return ioq->entity.ioprio_class == IOPRIO_CLASS_RT;
+}
+
+static inline int elv_ioq_ioprio_class(struct io_queue *ioq)
+{
+	return ioq->entity.new_ioprio_class;
+}
+
+static inline int elv_ioq_ioprio(struct io_queue *ioq)
+{
+	return ioq->entity.new_ioprio;
+}
+
+static inline void elv_ioq_set_ioprio_class(struct io_queue *ioq,
+						int ioprio_class)
+{
+	ioq->entity.new_ioprio_class = ioprio_class;
+	ioq->entity.ioprio_changed = 1;
+}
+
+static inline void elv_ioq_set_ioprio(struct io_queue *ioq, int ioprio)
+{
+	ioq->entity.new_ioprio = ioprio;
+	ioq->entity.ioprio_changed = 1;
+}
+
+static inline void *ioq_sched_queue(struct io_queue *ioq)
+{
+	if (ioq)
+		return ioq->sched_queue;
+	return NULL;
+}
+
+static inline struct io_group *ioq_to_io_group(struct io_queue *ioq)
+{
+	return container_of(ioq->entity.sched_data, struct io_group,
+						sched_data);
+}
+
+/* Functions used by blksysfs.c */
+extern ssize_t elv_slice_idle_show(struct request_queue *q, char *name);
+extern ssize_t elv_slice_idle_store(struct request_queue *q, const char *name,
+						size_t count);
+extern ssize_t elv_slice_sync_show(struct request_queue *q, char *name);
+extern ssize_t elv_slice_sync_store(struct request_queue *q, const char *name,
+						size_t count);
+extern ssize_t elv_slice_async_show(struct request_queue *q, char *name);
+extern ssize_t elv_slice_async_store(struct request_queue *q, const char *name,
+						size_t count);
+
+/* Functions used by elevator.c */
+extern int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e);
+extern void elv_exit_fq_data(struct elevator_queue *e);
+extern void elv_exit_fq_data_post(struct elevator_queue *e);
+
+extern void elv_ioq_request_add(struct request_queue *q, struct request *rq);
+extern void elv_ioq_request_removed(struct elevator_queue *e,
+					struct request *rq);
+extern void elv_fq_dispatched_request(struct elevator_queue *e,
+					struct request *rq);
+
+extern void elv_fq_activate_rq(struct request_queue *q, struct request *rq);
+extern void elv_fq_deactivate_rq(struct request_queue *q, struct request *rq);
+
+extern void elv_ioq_completed_request(struct request_queue *q,
+				struct request *rq);
+
+extern void *elv_fq_select_ioq(struct request_queue *q, int force);
+extern struct io_queue *rq_ioq(struct request *rq);
+
+/* Functions used by io schedulers */
+extern void elv_put_ioq(struct io_queue *ioq);
+extern void __elv_ioq_slice_expired(struct request_queue *q,
+					struct io_queue *ioq);
+extern int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq,
+		void *sched_queue, int ioprio_class, int ioprio, int is_sync);
+extern void elv_schedule_dispatch(struct request_queue *q);
+extern int elv_hw_tag(struct elevator_queue *e);
+extern void *elv_active_sched_queue(struct elevator_queue *e);
+extern int elv_mod_idle_slice_timer(struct elevator_queue *eq,
+					unsigned long expires);
+extern int elv_del_idle_slice_timer(struct elevator_queue *eq);
+extern unsigned int elv_get_slice_idle(struct elevator_queue *eq);
+extern void *io_group_async_queue_prio(struct io_group *iog, int ioprio_class,
+					int ioprio);
+extern void io_group_set_async_queue(struct io_group *iog, int ioprio_class,
+					int ioprio, struct io_queue *ioq);
+extern struct io_group *io_lookup_io_group_current(struct request_queue *q);
+extern int elv_nr_busy_ioq(struct elevator_queue *e);
+extern int elv_nr_busy_rt_ioq(struct elevator_queue *e);
+extern struct io_queue *elv_alloc_ioq(struct request_queue *q, gfp_t gfp_mask);
+extern void elv_free_ioq(struct io_queue *ioq);
+
+#else /* CONFIG_ELV_FAIR_QUEUING */
+
+static inline int elv_init_fq_data(struct request_queue *q,
+					struct elevator_queue *e)
+{
+	return 0;
+}
+
+static inline void elv_exit_fq_data(struct elevator_queue *e) {}
+static inline void elv_exit_fq_data_post(struct elevator_queue *e) {}
+
+static inline void elv_fq_activate_rq(struct request_queue *q,
+					struct request *rq)
+{
+}
+
+static inline void elv_fq_deactivate_rq(struct request_queue *q,
+					struct request *rq)
+{
+}
+
+static inline void elv_fq_dispatched_request(struct elevator_queue *e,
+						struct request *rq)
+{
+}
+
+static inline void elv_ioq_request_removed(struct elevator_queue *e,
+						struct request *rq)
+{
+}
+
+static inline void elv_ioq_request_add(struct request_queue *q,
+					struct request *rq)
+{
+}
+
+static inline void elv_ioq_completed_request(struct request_queue *q,
+						struct request *rq)
+{
+}
+
+static inline void *ioq_sched_queue(struct io_queue *ioq) { return NULL; }
+static inline struct io_queue *rq_ioq(struct request *rq) { return NULL; }
+static inline void *elv_fq_select_ioq(struct request_queue *q, int force)
+{
+	return NULL;
+}
+#endif /* CONFIG_ELV_FAIR_QUEUING */
+#endif /* _BFQ_SCHED_H */
diff --git a/block/elevator.c b/block/elevator.c
index 7073a90..c2f07f5 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -231,6 +231,9 @@ static struct elevator_queue *elevator_alloc(struct request_queue *q,
 	for (i = 0; i < ELV_HASH_ENTRIES; i++)
 		INIT_HLIST_HEAD(&eq->hash[i]);
 
+	if (elv_init_fq_data(q, eq))
+		goto err;
+
 	return eq;
 err:
 	kfree(eq);
@@ -301,9 +304,11 @@ EXPORT_SYMBOL(elevator_init);
 void elevator_exit(struct elevator_queue *e)
 {
 	mutex_lock(&e->sysfs_lock);
+	elv_exit_fq_data(e);
 	if (e->ops->elevator_exit_fn)
 		e->ops->elevator_exit_fn(e);
 	e->ops = NULL;
+	elv_exit_fq_data_post(e);
 	mutex_unlock(&e->sysfs_lock);
 
 	kobject_put(&e->kobj);
@@ -314,6 +319,8 @@ static void elv_activate_rq(struct request_queue *q, struct request *rq)
 {
 	struct elevator_queue *e = q->elevator;
 
+	elv_fq_activate_rq(q, rq);
+
 	if (e->ops->elevator_activate_req_fn)
 		e->ops->elevator_activate_req_fn(q, rq);
 }
@@ -322,6 +329,8 @@ static void elv_deactivate_rq(struct request_queue *q, struct request *rq)
 {
 	struct elevator_queue *e = q->elevator;
 
+	elv_fq_deactivate_rq(q, rq);
+
 	if (e->ops->elevator_deactivate_req_fn)
 		e->ops->elevator_deactivate_req_fn(q, rq);
 }
@@ -446,6 +455,7 @@ void elv_dispatch_sort(struct request_queue *q, struct request *rq)
 	elv_rqhash_del(q, rq);
 
 	q->nr_sorted--;
+	elv_fq_dispatched_request(q->elevator, rq);
 
 	boundary = q->end_sector;
 	stop_flags = REQ_SOFTBARRIER | REQ_HARDBARRIER | REQ_STARTED;
@@ -486,6 +496,7 @@ void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
 	elv_rqhash_del(q, rq);
 
 	q->nr_sorted--;
+	elv_fq_dispatched_request(q->elevator, rq);
 
 	q->end_sector = rq_end_sector(rq);
 	q->boundary_rq = rq;
@@ -553,6 +564,7 @@ void elv_merge_requests(struct request_queue *q, struct request *rq,
 	elv_rqhash_del(q, next);
 
 	q->nr_sorted--;
+	elv_ioq_request_removed(e, next);
 	q->last_merge = rq;
 }
 
@@ -657,12 +669,8 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
 				q->last_merge = rq;
 		}
 
-		/*
-		 * Some ioscheds (cfq) run q->request_fn directly, so
-		 * rq cannot be accessed after calling
-		 * elevator_add_req_fn.
-		 */
 		q->elevator->ops->elevator_add_req_fn(q, rq);
+		elv_ioq_request_add(q, rq);
 		break;
 
 	case ELEVATOR_INSERT_REQUEUE:
@@ -872,13 +880,12 @@ void elv_dequeue_request(struct request_queue *q, struct request *rq)
 
 int elv_queue_empty(struct request_queue *q)
 {
-	struct elevator_queue *e = q->elevator;
-
 	if (!list_empty(&q->queue_head))
 		return 0;
 
-	if (e->ops->elevator_queue_empty_fn)
-		return e->ops->elevator_queue_empty_fn(q);
+	/* Hopefully nr_sorted works and no need to call queue_empty_fn */
+	if (q->nr_sorted)
+		return 0;
 
 	return 1;
 }
@@ -953,8 +960,11 @@ void elv_completed_request(struct request_queue *q, struct request *rq)
 	 */
 	if (blk_account_rq(rq)) {
 		q->in_flight--;
-		if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
-			e->ops->elevator_completed_req_fn(q, rq);
+		if (blk_sorted_rq(rq)) {
+			if (e->ops->elevator_completed_req_fn)
+				e->ops->elevator_completed_req_fn(q, rq);
+			elv_ioq_completed_request(q, rq);
+		}
 	}
 
 	/*
@@ -1242,3 +1252,17 @@ struct request *elv_rb_latter_request(struct request_queue *q,
 	return NULL;
 }
 EXPORT_SYMBOL(elv_rb_latter_request);
+
+/* Get the io scheduler queue pointer. For cfq, it is stored in rq->ioq*/
+void *elv_get_sched_queue(struct request_queue *q, struct request *rq)
+{
+	return ioq_sched_queue(rq_ioq(rq));
+}
+EXPORT_SYMBOL(elv_get_sched_queue);
+
+/* Select an ioscheduler queue to dispatch request from. */
+void *elv_select_sched_queue(struct request_queue *q, int force)
+{
+	return ioq_sched_queue(elv_fq_select_ioq(q, force));
+}
+EXPORT_SYMBOL(elv_select_sched_queue);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index b4f71f1..96a94c9 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -245,6 +245,11 @@ struct request {
 
 	/* for bidi */
 	struct request *next_rq;
+
+#ifdef CONFIG_ELV_FAIR_QUEUING
+	/* io queue request belongs to */
+	struct io_queue *ioq;
+#endif
 };
 
 static inline unsigned short req_get_ioprio(struct request *req)
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index c59b769..679c149 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -2,6 +2,7 @@
 #define _LINUX_ELEVATOR_H
 
 #include <linux/percpu.h>
+#include "../../block/elevator-fq.h"
 
 #ifdef CONFIG_BLOCK
 
@@ -29,6 +30,18 @@ typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct reques
 
 typedef void *(elevator_init_fn) (struct request_queue *);
 typedef void (elevator_exit_fn) (struct elevator_queue *);
+#ifdef CONFIG_ELV_FAIR_QUEUING
+typedef void (elevator_free_sched_queue_fn) (struct elevator_queue*, void *);
+typedef void (elevator_active_ioq_set_fn) (struct request_queue*, void *, int);
+typedef void (elevator_active_ioq_reset_fn) (struct request_queue *, void*);
+typedef void (elevator_arm_slice_timer_fn) (struct request_queue*, void*);
+typedef int (elevator_should_preempt_fn) (struct request_queue*, void*,
+						struct request*);
+typedef int (elevator_update_idle_window_fn) (struct elevator_queue*, void*,
+						struct request*);
+typedef struct io_queue* (elevator_close_cooperator_fn) (struct request_queue*,
+						void*, int probe);
+#endif
 
 struct elevator_ops
 {
@@ -56,6 +69,17 @@ struct elevator_ops
 	elevator_init_fn *elevator_init_fn;
 	elevator_exit_fn *elevator_exit_fn;
 	void (*trim)(struct io_context *);
+
+#ifdef CONFIG_ELV_FAIR_QUEUING
+	elevator_free_sched_queue_fn *elevator_free_sched_queue_fn;
+	elevator_active_ioq_set_fn *elevator_active_ioq_set_fn;
+	elevator_active_ioq_reset_fn *elevator_active_ioq_reset_fn;
+
+	elevator_arm_slice_timer_fn *elevator_arm_slice_timer_fn;
+	elevator_should_preempt_fn *elevator_should_preempt_fn;
+	elevator_update_idle_window_fn *elevator_update_idle_window_fn;
+	elevator_close_cooperator_fn *elevator_close_cooperator_fn;
+#endif
 };
 
 #define ELV_NAME_MAX	(16)
@@ -76,6 +100,9 @@ struct elevator_type
 	struct elv_fs_entry *elevator_attrs;
 	char elevator_name[ELV_NAME_MAX];
 	struct module *elevator_owner;
+#ifdef CONFIG_ELV_FAIR_QUEUING
+	int elevator_features;
+#endif
 };
 
 /*
@@ -89,6 +116,10 @@ struct elevator_queue
 	struct elevator_type *elevator_type;
 	struct mutex sysfs_lock;
 	struct hlist_head *hash;
+#ifdef CONFIG_ELV_FAIR_QUEUING
+	/* fair queuing data */
+	struct elv_fq_data efqd;
+#endif
 };
 
 /*
@@ -209,5 +240,25 @@ enum {
 	__val;							\
 })
 
+/* iosched can let elevator know their feature set/capability */
+#ifdef CONFIG_ELV_FAIR_QUEUING
+
+/* iosched wants to use fq logic of elevator layer */
+#define	ELV_IOSCHED_NEED_FQ	1
+
+static inline int elv_iosched_fair_queuing_enabled(struct elevator_queue *e)
+{
+	return (e->elevator_type->elevator_features) & ELV_IOSCHED_NEED_FQ;
+}
+
+#else /* ELV_IOSCHED_FAIR_QUEUING */
+
+static inline int elv_iosched_fair_queuing_enabled(struct elevator_queue *e)
+{
+	return 0;
+}
+#endif /* ELV_IOSCHED_FAIR_QUEUING */
+extern void *elv_get_sched_queue(struct request_queue *q, struct request *rq);
+extern void *elv_select_sched_queue(struct request_queue *q, int force);
 #endif /* CONFIG_BLOCK */
 #endif
-- 
1.6.0.1

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Fabio Checconi]

> From: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> Date: Wed, May 27, 2009 01:53:59PM -0700
>
> On Tue, May 26, 2009 at 3:41 PM, Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > This is common fair queuing code in elevator layer. This is controlled by
...
> > +/**
> > + * __bfq_lookup_next_entity - return the first eligible entity in @st.
> > + * @st: the service tree.
> > + *
> > + * Update the virtual time in @st and return the first eligible entity
> > + * it contains.
> > + */
> > +static struct io_entity *__bfq_lookup_next_entity(struct io_service_tree *st)
> > +{
> > +	struct io_entity *entity;
> > +
> > +	if (RB_EMPTY_ROOT(&st->active))
> > +		return NULL;
> > +
> > +	bfq_update_vtime(st);
> 
> Vivek, Paolo, Fabio,
> Over here we call bfq_update_vtime(), and this function could have
> been called even when we are just doing a lookup (and not an extract).
> So vtime is updated while we are not really selecting the next queue
> for service (for an example, see elv_preempt_queue()). This can result
> in a call to update_vtime when only an entity with small weight (say
> weight=1) is backlogged and another entity with bigger weight (say 10)
> is getting serviced so it is not in the tree (we extract the entity
> which is getting service). This results in a big vtime jump to the
> start time of the entity with weight 1 (entity of weight 1 would have
> big start times, as it has small weight). Now when another entity with
> bigger weight (say 90) gets backlogged, it is assigned a new vtime
> from service tree's vtime, causing it to get a big value. In the
> meanwhile, iog for weight 10 keeps getting service for many quantums,
> as it was continuously backlogged.
> 
> The problem happens because we extract an entity (removing it from the
> tree) while it is getting service, and do vtime jumps based on what is
> still in the tree. I think we need to add an extra check on the vtime
> of the entity in service, before we take a vtime jump.
> 
> I have actually seen this happening when trying to debug on of my
> tests. Please let me know what you think.
> 

IIRC this behavior is not coming from bfq, as the original code
called __bfq_lookup_next_entity() without extraction only if there
was no entity under service (in bfq_update_next_active() it checked
for sd->active_entity != NULL).

I've not looked at the details of what changed, thus I don't know
why the old behavior cannot be maintained, but the virtual time jump
should be avoided in this case (and it is not specified by the wf2q+
algorithm).

[ sorry for the excessive trimming, but due to some charset problems
  the quotations were unreadable ]

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Vivek Goyal]

On Wed, May 27, 2009 at 01:53:59PM -0700, Nauman Rafique wrote:

[..]
> > +/**
> > + * __bfq_lookup_next_entity - return the first eligible entity in @st.
> > + * @st: the service tree.
> > + *
> > + * Update the virtual time in @st and return the first eligible entity
> > + * it contains.
> > + */
> > +static struct io_entity *__bfq_lookup_next_entity(struct io_service_tree *st)
> > +{
> > +       struct io_entity *entity;
> > +
> > +       if (RB_EMPTY_ROOT(&st->active))
> > +               return NULL;
> > +
> > +       bfq_update_vtime(st);
> 
> Vivek, Paolo, Fabio,
> Over here we call bfq_update_vtime(), and this function could have
> been called even when we are just doing a lookup (and not an extract).
> So vtime is updated while we are not really selecting the next queue
> for service (for an example, see elv_preempt_queue()). This can result
> in a call to update_vtime when only an entity with small weight (say
> weight=1) is backlogged and another entity with bigger weight (say 10)
> is getting serviced so it is not in the tree (we extract the entity
> which is getting service). This results in a big vtime jump to the
> start time of the entity with weight 1 (entity of weight 1 would have
> big start times, as it has small weight). Now when another entity with
> bigger weight (say 90) gets backlogged, it is assigned a new vtime
> from service tree's vtime, causing it to get a big value. In the
> meanwhile, iog for weight 10 keeps getting service for many quantums,
> as it was continuously backlogged.
> 
> The problem happens because we extract an entity (removing it from the
> tree) while it is getting service, and do vtime jumps based on what is
> still in the tree. I think we need to add an extra check on the vtime
> of the entity in service, before we take a vtime jump.
> 
> I have actually seen this happening when trying to debug on of my
> tests. Please let me know what you think.
> 

Hi Nauman,

This sounds like a problem but apart from elv_preempt_queue(), in which path
do you see it?

Initially fabio posted the patches where preemption was allowed only if
the preempting queue is the next one to be served. To keep the behavior
same as CFQ, I have changed that logic and if we decide to preempt the
current queue (based on many checks like sync or async), I expire the
current queue and add the new queue to the front of the service tree so
that it is selected next. It does impact the fairness a bit but that's how
cfq does it today and concept of preemption with-in same prio class is
somewhat peculiar.

So in latest patches preemption path is covered. There does not seem to be
other paths where we do lookups while and active entity is being served.
For example, update_next_active() does not continue with lookup if there
is an active entity. So with this version of patch, you should not face
the issue.

In general, I think it is a good idea to fix it in update_vtime() so
that not to udpate vtime if there is an active entity and not rely on 
caller who makes sure that update_vtime() is not called when there is
an active entity. Do you have a quick patch for that?

Thanks
Vivek

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Nauman Rafique]

On Thu, May 28, 2009 at 9:00 AM, Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> On Wed, May 27, 2009 at 01:53:59PM -0700, Nauman Rafique wrote:
>
> [..]
>> > +/**
>> > + * __bfq_lookup_next_entity - return the first eligible entity in @st.
>> > + * @st: the service tree.
>> > + *
>> > + * Update the virtual time in @st and return the first eligible entity
>> > + * it contains.
>> > + */
>> > +static struct io_entity *__bfq_lookup_next_entity(struct io_service_tree *st)
>> > +{
>> > +       struct io_entity *entity;
>> > +
>> > +       if (RB_EMPTY_ROOT(&st->active))
>> > +               return NULL;
>> > +
>> > +       bfq_update_vtime(st);
>>
>> Vivek, Paolo, Fabio,
>> Over here we call bfq_update_vtime(), and this function could have
>> been called even when we are just doing a lookup (and not an extract).
>> So vtime is updated while we are not really selecting the next queue
>> for service (for an example, see elv_preempt_queue()). This can result
>> in a call to update_vtime when only an entity with small weight (say
>> weight=1) is backlogged and another entity with bigger weight (say 10)
>> is getting serviced so it is not in the tree (we extract the entity
>> which is getting service). This results in a big vtime jump to the
>> start time of the entity with weight 1 (entity of weight 1 would have
>> big start times, as it has small weight). Now when another entity with
>> bigger weight (say 90) gets backlogged, it is assigned a new vtime
>> from service tree's vtime, causing it to get a big value. In the
>> meanwhile, iog for weight 10 keeps getting service for many quantums,
>> as it was continuously backlogged.
>>
>> The problem happens because we extract an entity (removing it from the
>> tree) while it is getting service, and do vtime jumps based on what is
>> still in the tree. I think we need to add an extra check on the vtime
>> of the entity in service, before we take a vtime jump.
>>
>> I have actually seen this happening when trying to debug on of my
>> tests. Please let me know what you think.
>>
>
> Hi Nauman,
>
> This sounds like a problem but apart from elv_preempt_queue(), in which path
> do you see it?
>
> Initially fabio posted the patches where preemption was allowed only if
> the preempting queue is the next one to be served. To keep the behavior
> same as CFQ, I have changed that logic and if we decide to preempt the
> current queue (based on many checks like sync or async), I expire the
> current queue and add the new queue to the front of the service tree so
> that it is selected next. It does impact the fairness a bit but that's how
> cfq does it today and concept of preemption with-in same prio class is
> somewhat peculiar.
>
> So in latest patches preemption path is covered. There does not seem to be
> other paths where we do lookups while and active entity is being served.
> For example, update_next_active() does not continue with lookup if there
> is an active entity. So with this version of patch, you should not face
> the issue.
>
> In general, I think it is a good idea to fix it in update_vtime() so
> that not to udpate vtime if there is an active entity and not rely on
> caller who makes sure that update_vtime() is not called when there is
> an active entity. Do you have a quick patch for that?

Adding this extra check in update_vtime() is tricky. If we don't
update vtime, then its possible that lookup would return no entity,
even though there are backlogged queues, as all backlogged entities
might be not eligible (i.e have start times bigger than vtime).
When an entity is currently under service, we don't know what would be
the next entity really, as it could be the current entity under
service, depending on the actual time slice used by under service
entity.

You are right that the lookup (without extract) was done only in
preemption path. And with your latest changes, even that is removed.
In this case, just having a BUG_ON() to ensure this does not happen
should suffice.

commit dc54ad458b907db5523e8a088786014da8c4b3b2
Author: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Date:   Thu May 28 12:27:00 2009 -0700

    Add a BUG_ON() that should fire when we can update vtime while just
    doing a lookup for next entity (and not extraction).

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index f1179aa..d512c1b 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -1036,8 +1036,11 @@ struct io_entity *bfq_lookup_next_entity(struct
io_sched_data *sd,
        /*
         * One can check for which will be next selected entity without
         * expiring the current one.
+        * Also, we should not call lookup when an entity is active, as
+        * we extract an active entity from tree, and doing lookup can result
+        * in an erroneous vtime jump when active entity is extacted from tree.
         */
-       BUG_ON(extract && sd->active_entity != NULL);
+       BUG_ON(sd->active_entity != NULL);

        for (i = 0; i < IO_IOPRIO_CLASSES; i++, st++) {
                entity = __bfq_lookup_next_entity(st);


I have some concerns about the new preemption logic. We modify the
start and finish time to make sure the entity gets selected next. So
the entity which preempts others can eventually get more service than
others (specially if it keeps preempting others). It seems that we can
fix that by temporarily pushing the entity to the front, without
modifying start/finish times. One way to do that is to add an extra
flag to an entity. When the flag is set, we can ignore finish times
and prefer the entity (in bfq_first_active_entity()). This has the
advantage that since we are preserving start/finish times, over time,
such an entity will be de-prioritized over others. In order to ensure
that actually does happen, we can introduce a threshold (call it
preempt_threshold). Then the entity with the flag set would jump to
the front only if the difference between 'its finish time' and 'the
finish time of other entities' is within this threshold. Let me know
if it makes sense.

>
> Thanks
> Vivek
>

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Vivek Goyal]

On Thu, May 28, 2009 at 12:41:27PM -0700, Nauman Rafique wrote:
> On Thu, May 28, 2009 at 9:00 AM, Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > On Wed, May 27, 2009 at 01:53:59PM -0700, Nauman Rafique wrote:
> >
> > [..]
> >> > +/**
> >> > + * __bfq_lookup_next_entity - return the first eligible entity in @st.
> >> > + * @st: the service tree.
> >> > + *
> >> > + * Update the virtual time in @st and return the first eligible entity
> >> > + * it contains.
> >> > + */
> >> > +static struct io_entity *__bfq_lookup_next_entity(struct io_service_tree *st)
> >> > +{
> >> > +       struct io_entity *entity;
> >> > +
> >> > +       if (RB_EMPTY_ROOT(&st->active))
> >> > +               return NULL;
> >> > +
> >> > +       bfq_update_vtime(st);
> >>
> >> Vivek, Paolo, Fabio,
> >> Over here we call bfq_update_vtime(), and this function could have
> >> been called even when we are just doing a lookup (and not an extract).
> >> So vtime is updated while we are not really selecting the next queue
> >> for service (for an example, see elv_preempt_queue()). This can result
> >> in a call to update_vtime when only an entity with small weight (say
> >> weight=1) is backlogged and another entity with bigger weight (say 10)
> >> is getting serviced so it is not in the tree (we extract the entity
> >> which is getting service). This results in a big vtime jump to the
> >> start time of the entity with weight 1 (entity of weight 1 would have
> >> big start times, as it has small weight). Now when another entity with
> >> bigger weight (say 90) gets backlogged, it is assigned a new vtime
> >> from service tree's vtime, causing it to get a big value. In the
> >> meanwhile, iog for weight 10 keeps getting service for many quantums,
> >> as it was continuously backlogged.
> >>
> >> The problem happens because we extract an entity (removing it from the
> >> tree) while it is getting service, and do vtime jumps based on what is
> >> still in the tree. I think we need to add an extra check on the vtime
> >> of the entity in service, before we take a vtime jump.
> >>
> >> I have actually seen this happening when trying to debug on of my
> >> tests. Please let me know what you think.
> >>
> >
> > Hi Nauman,
> >
> > This sounds like a problem but apart from elv_preempt_queue(), in which path
> > do you see it?
> >
> > Initially fabio posted the patches where preemption was allowed only if
> > the preempting queue is the next one to be served. To keep the behavior
> > same as CFQ, I have changed that logic and if we decide to preempt the
> > current queue (based on many checks like sync or async), I expire the
> > current queue and add the new queue to the front of the service tree so
> > that it is selected next. It does impact the fairness a bit but that's how
> > cfq does it today and concept of preemption with-in same prio class is
> > somewhat peculiar.
> >
> > So in latest patches preemption path is covered. There does not seem to be
> > other paths where we do lookups while and active entity is being served.
> > For example, update_next_active() does not continue with lookup if there
> > is an active entity. So with this version of patch, you should not face
> > the issue.
> >
> > In general, I think it is a good idea to fix it in update_vtime() so
> > that not to udpate vtime if there is an active entity and not rely on
> > caller who makes sure that update_vtime() is not called when there is
> > an active entity. Do you have a quick patch for that?
> 
> Adding this extra check in update_vtime() is tricky. If we don't
> update vtime, then its possible that lookup would return no entity,
> even though there are backlogged queues, as all backlogged entities
> might be not eligible (i.e have start times bigger than vtime).
> When an entity is currently under service, we don't know what would be
> the next entity really, as it could be the current entity under
> service, depending on the actual time slice used by under service
> entity.
> 
> You are right that the lookup (without extract) was done only in
> preemption path. And with your latest changes, even that is removed.
> In this case, just having a BUG_ON() to ensure this does not happen
> should suffice.
> 
> commit dc54ad458b907db5523e8a088786014da8c4b3b2
> Author: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> Date:   Thu May 28 12:27:00 2009 -0700
> 
>     Add a BUG_ON() that should fire when we can update vtime while just
>     doing a lookup for next entity (and not extraction).
> 
> diff --git a/block/elevator-fq.c b/block/elevator-fq.c
> index f1179aa..d512c1b 100644
> --- a/block/elevator-fq.c
> +++ b/block/elevator-fq.c
> @@ -1036,8 +1036,11 @@ struct io_entity *bfq_lookup_next_entity(struct
> io_sched_data *sd,
>         /*
>          * One can check for which will be next selected entity without
>          * expiring the current one.
> +        * Also, we should not call lookup when an entity is active, as
> +        * we extract an active entity from tree, and doing lookup can result
> +        * in an erroneous vtime jump when active entity is extacted from tree.
>          */
> -       BUG_ON(extract && sd->active_entity != NULL);
> +       BUG_ON(sd->active_entity != NULL);

I think this should be good. I had added this "extract" in the past, because
preemption logic could do lookup which an entity was active.

> 
>         for (i = 0; i < IO_IOPRIO_CLASSES; i++, st++) {
>                 entity = __bfq_lookup_next_entity(st);
> 
> 
> I have some concerns about the new preemption logic.

Actually we need a more proper definition of in-class preemption. Across
class preemption means that RT class always gets to run first.

What does in-class preemption mean? If I look at the current CFQ code,
it does look like that preempting process will gain share. It is always
added to the front of the tree with "rb_key=0" and that means, this new
queue will get fresh time slice (even if it got time slice very recently).

Currently I have just tried to make the behavior same as CFQ to reduce
the possiblility of regressions. That's a different thing that we can
discuss what should be the exact behavior in case of in-class preemption
and first it needs to be fixed in CFQ, if current behavior is an issue.

On the other hand, I am not sure if previous bfq preemption logic was
working. We were checking if the new request belonged to the queue which
will be served next, then preempt the existing queue. While looking
for the next queue, I think we did not consider the current active
entity (as it was not on the tree). So after expiry of the current
queue, it might get selected next if it has not got its share. So there
was no point in preempting the queue. If queue already got its share, then
anyway the next queue will be selected next and there is no point in
preempting the current queue.

I am not sure why reads should preempt writes in CFQ. We are already giving
preference to reads by giving these bigger time slice as compared to
writes and that should take care of read being preferred over writes?
 
Thanks
Vivek
  
> We modify the
> start and finish time to make sure the entity gets selected next. So
> the entity which preempts others can eventually get more service than
> others (specially if it keeps preempting others). It seems that we can
> fix that by temporarily pushing the entity to the front, without
> modifying start/finish times. One way to do that is to add an extra
> flag to an entity. When the flag is set, we can ignore finish times
> and prefer the entity (in bfq_first_active_entity()). This has the
> advantage that since we are preserving start/finish times, over time,
> such an entity will be de-prioritized over others. In order to ensure
> that actually does happen, we can introduce a threshold (call it
> preempt_threshold). Then the entity with the flag set would jump to
> the front only if the difference between 'its finish time' and 'the
> finish time of other entities' is within this threshold. Let me know
> if it makes sense.
> 
> >
> > Thanks
> > Vivek
> >

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Fabio Checconi]

> From: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Date: Fri, May 29, 2009 12:06:10PM -0400
>
> On Thu, May 28, 2009 at 12:41:27PM -0700, Nauman Rafique wrote:
...
> > I have some concerns about the new preemption logic.
> 
> Actually we need a more proper definition of in-class preemption. Across
> class preemption means that RT class always gets to run first.
> 
> What does in-class preemption mean? If I look at the current CFQ code,
> it does look like that preempting process will gain share. It is always
> added to the front of the tree with "rb_key=0" and that means, this new
> queue will get fresh time slice (even if it got time slice very recently).
> 
> Currently I have just tried to make the behavior same as CFQ to reduce
> the possiblility of regressions. That's a different thing that we can
> discuss what should be the exact behavior in case of in-class preemption
> and first it needs to be fixed in CFQ, if current behavior is an issue.
> 
> On the other hand, I am not sure if previous bfq preemption logic was
> working. We were checking if the new request belonged to the queue which
> will be served next, then preempt the existing queue. While looking
> for the next queue, I think we did not consider the current active
> entity (as it was not on the tree). So after expiry of the current
> queue, it might get selected next if it has not got its share. So there
> was no point in preempting the queue. If queue already got its share, then
> anyway the next queue will be selected next and there is no point in
> preempting the current queue.
> 

BFQ had no preemption logic, as far as I know; it simply was not
preemptive, and the guarantees it provided took that into account.

I don't know what is the best way to introduce a CFQ-like preemption logic
into the wf2q+ code; for sure anything that does not schedule according
to the algorithm's timestamps is a good candidate to break the guarantees
the scheduler can provide, making it an extremely complex way to get
the same worst-case delays of a (much simpler) round-robin scheduler.

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Nauman Rafique]

On Fri, May 29, 2009 at 9:57 AM, Fabio Checconi <fchecconi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>> From: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>> Date: Fri, May 29, 2009 12:06:10PM -0400
>>
>> On Thu, May 28, 2009 at 12:41:27PM -0700, Nauman Rafique wrote:
> ...
>> > I have some concerns about the new preemption logic.
>>
>> Actually we need a more proper definition of in-class preemption. Across
>> class preemption means that RT class always gets to run first.
>>
>> What does in-class preemption mean? If I look at the current CFQ code,
>> it does look like that preempting process will gain share. It is always
>> added to the front of the tree with "rb_key=0" and that means, this new
>> queue will get fresh time slice (even if it got time slice very recently).
>>
>> Currently I have just tried to make the behavior same as CFQ to reduce
>> the possiblility of regressions. That's a different thing that we can
>> discuss what should be the exact behavior in case of in-class preemption
>> and first it needs to be fixed in CFQ, if current behavior is an issue.
>>
>> On the other hand, I am not sure if previous bfq preemption logic was
>> working. We were checking if the new request belonged to the queue which
>> will be served next, then preempt the existing queue. While looking
>> for the next queue, I think we did not consider the current active
>> entity (as it was not on the tree). So after expiry of the current
>> queue, it might get selected next if it has not got its share. So there
>> was no point in preempting the queue. If queue already got its share, then
>> anyway the next queue will be selected next and there is no point in
>> preempting the current queue.
>>
>
> BFQ had no preemption logic, as far as I know; it simply was not
> preemptive, and the guarantees it provided took that into account.
>
> I don't know what is the best way to introduce a CFQ-like preemption logic
> into the wf2q+ code; for sure anything that does not schedule according
> to the algorithm's timestamps is a good candidate to break the guarantees
> the scheduler can provide, making it an extremely complex way to get
> the same worst-case delays of a (much simpler) round-robin scheduler.
>

What you guys think of my suggestion of handling preemption?
Basically, we don't modify the start/finish tags, so overall the
fairness properties should not be broken. But in short term, we still
allow preemption and let one queue jump another.

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Vivek Goyal]

On Fri, May 29, 2009 at 12:06:03PM -0700, Nauman Rafique wrote:
> On Fri, May 29, 2009 at 9:57 AM, Fabio Checconi <fchecconi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >> From: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> >> Date: Fri, May 29, 2009 12:06:10PM -0400
> >>
> >> On Thu, May 28, 2009 at 12:41:27PM -0700, Nauman Rafique wrote:
> > ...
> >> > I have some concerns about the new preemption logic.
> >>
> >> Actually we need a more proper definition of in-class preemption. Across
> >> class preemption means that RT class always gets to run first.
> >>
> >> What does in-class preemption mean? If I look at the current CFQ code,
> >> it does look like that preempting process will gain share. It is always
> >> added to the front of the tree with "rb_key=0" and that means, this new
> >> queue will get fresh time slice (even if it got time slice very recently).
> >>
> >> Currently I have just tried to make the behavior same as CFQ to reduce
> >> the possiblility of regressions. That's a different thing that we can
> >> discuss what should be the exact behavior in case of in-class preemption
> >> and first it needs to be fixed in CFQ, if current behavior is an issue.
> >>
> >> On the other hand, I am not sure if previous bfq preemption logic was
> >> working. We were checking if the new request belonged to the queue which
> >> will be served next, then preempt the existing queue. While looking
> >> for the next queue, I think we did not consider the current active
> >> entity (as it was not on the tree). So after expiry of the current
> >> queue, it might get selected next if it has not got its share. So there
> >> was no point in preempting the queue. If queue already got its share, then
> >> anyway the next queue will be selected next and there is no point in
> >> preempting the current queue.
> >>
> >
> > BFQ had no preemption logic, as far as I know; it simply was not
> > preemptive, and the guarantees it provided took that into account.
> >
> > I don't know what is the best way to introduce a CFQ-like preemption logic
> > into the wf2q+ code; for sure anything that does not schedule according
> > to the algorithm's timestamps is a good candidate to break the guarantees
> > the scheduler can provide, making it an extremely complex way to get
> > the same worst-case delays of a (much simpler) round-robin scheduler.
> >
> 
> What you guys think of my suggestion of handling preemption?
> Basically, we don't modify the start/finish tags, so overall the
> fairness properties should not be broken. But in short term, we still
> allow preemption and let one queue jump another.

It sounded complicated from the description of it. I would prefer either
we get rid of in-class preemtion thing completely or do in-class preemtption
at the cost of gaining share, like cfq does.

In fact, to begin with, I prefer to be as close as possible to CFQ and then
change things selectively one piece at a time so that we can analyze the
impact well.

Thanks
Vivek

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Nauman Rafique]

On Tue, May 26, 2009 at 3:41 PM, Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> This is common fair queuing code in elevator layer. This is controlled by
> config option CONFIG_ELV_FAIR_QUEUING. This patch initially only introduces
> flat fair queuing support where there is only one group, "root group" and all
> the tasks belong to root group.
>
> This elevator layer changes are backward compatible. That means any ioscheduler
> using old interfaces will continue to work.
>
> This code is essentially the CFQ code for fair queuing. The primary difference
> is that flat rounding robin algorithm of CFQ has been replaced with BFQ (WF2Q+).
>
> Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Fabio Checconi <fabio-f9ZlEuEWxVeACYmtYXMKmw@public.gmane.org>
> Signed-off-by: Paolo Valente <paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org>
> Signed-off-by: Aristeu Rozanski <aris-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  block/Kconfig.iosched    |   13 +
>  block/Makefile           |    1 +
>  block/blk-sysfs.c        |   25 +
>  block/elevator-fq.c      | 2078 ++++++++++++++++++++++++++++++++++++++++++++++
>  block/elevator-fq.h      |  488 +++++++++++
>  block/elevator.c         |   46 +-
>  include/linux/blkdev.h   |    5 +
>  include/linux/elevator.h |   51 ++
>  8 files changed, 2696 insertions(+), 11 deletions(-)
>  create mode 100644 block/elevator-fq.c
>  create mode 100644 block/elevator-fq.h
>
> diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
> index 7e803fc..3398134 100644
> --- a/block/Kconfig.iosched
> +++ b/block/Kconfig.iosched
> @@ -2,6 +2,19 @@ if BLOCK
>
>  menu "IO Schedulers"
>
> +config ELV_FAIR_QUEUING
> +       bool "Elevator Fair Queuing Support"
> +       default n
> +       ---help---
> +         Traditionally only cfq had notion of multiple queues and it did
> +         fair queuing at its own. With the cgroups and need of controlling
> +         IO, now even the simple io schedulers like noop, deadline, as will
> +         have one queue per cgroup and will need hierarchical fair queuing.
> +         Instead of every io scheduler implementing its own fair queuing
> +         logic, this option enables fair queuing in elevator layer so that
> +         other ioschedulers can make use of it.
> +         If unsure, say N.
> +
>  config IOSCHED_NOOP
>        bool
>        default y
> diff --git a/block/Makefile b/block/Makefile
> index e9fa4dd..94bfc6e 100644
> --- a/block/Makefile
> +++ b/block/Makefile
> @@ -15,3 +15,4 @@ obj-$(CONFIG_IOSCHED_CFQ)     += cfq-iosched.o
>
>  obj-$(CONFIG_BLOCK_COMPAT)     += compat_ioctl.o
>  obj-$(CONFIG_BLK_DEV_INTEGRITY)        += blk-integrity.o
> +obj-$(CONFIG_ELV_FAIR_QUEUING) += elevator-fq.o
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index 3ff9bba..082a273 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -276,6 +276,26 @@ static struct queue_sysfs_entry queue_iostats_entry = {
>        .store = queue_iostats_store,
>  };
>
> +#ifdef CONFIG_ELV_FAIR_QUEUING
> +static struct queue_sysfs_entry queue_slice_idle_entry = {
> +       .attr = {.name = "slice_idle", .mode = S_IRUGO | S_IWUSR },
> +       .show = elv_slice_idle_show,
> +       .store = elv_slice_idle_store,
> +};
> +
> +static struct queue_sysfs_entry queue_slice_sync_entry = {
> +       .attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR },
> +       .show = elv_slice_sync_show,
> +       .store = elv_slice_sync_store,
> +};
> +
> +static struct queue_sysfs_entry queue_slice_async_entry = {
> +       .attr = {.name = "slice_async", .mode = S_IRUGO | S_IWUSR },
> +       .show = elv_slice_async_show,
> +       .store = elv_slice_async_store,
> +};
> +#endif
> +
>  static struct attribute *default_attrs[] = {
>        &queue_requests_entry.attr,
>        &queue_ra_entry.attr,
> @@ -287,6 +307,11 @@ static struct attribute *default_attrs[] = {
>        &queue_nomerges_entry.attr,
>        &queue_rq_affinity_entry.attr,
>        &queue_iostats_entry.attr,
> +#ifdef CONFIG_ELV_FAIR_QUEUING
> +       &queue_slice_idle_entry.attr,
> +       &queue_slice_sync_entry.attr,
> +       &queue_slice_async_entry.attr,
> +#endif
>        NULL,
>  };
>
> diff --git a/block/elevator-fq.c b/block/elevator-fq.c
> new file mode 100644
> index 0000000..c5cc080
> --- /dev/null
> +++ b/block/elevator-fq.c
> @@ -0,0 +1,2078 @@
> +/*
> + * BFQ: Hierarchical B-WF2Q+ scheduler.
> + *
> + * Based on ideas and code from CFQ:
> + * Copyright (C) 2003 Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
> + *
> + * Copyright (C) 2008 Fabio Checconi <fabio-f9ZlEuEWxVeACYmtYXMKmw@public.gmane.org>
> + *                   Paolo Valente <paolo.valente@unimore.it>
> + */
> +
> +#include <linux/blkdev.h>
> +#include "elevator-fq.h"
> +#include <linux/blktrace_api.h>
> +
> +/* Values taken from cfq */
> +const int elv_slice_sync = HZ / 10;
> +int elv_slice_async = HZ / 25;
> +const int elv_slice_async_rq = 2;
> +int elv_slice_idle = HZ / 125;
> +static struct kmem_cache *elv_ioq_pool;
> +
> +#define ELV_SLICE_SCALE                (5)
> +#define ELV_HW_QUEUE_MIN       (5)
> +#define IO_SERVICE_TREE_INIT   ((struct io_service_tree)               \
> +                               { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
> +
> +static inline struct io_queue *elv_close_cooperator(struct request_queue *q,
> +                                       struct io_queue *ioq, int probe);
> +struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
> +                                                int extract);
> +
> +static inline int elv_prio_slice(struct elv_fq_data *efqd, int sync,
> +                                       unsigned short prio)
> +{
> +       const int base_slice = efqd->elv_slice[sync];
> +
> +       WARN_ON(prio >= IOPRIO_BE_NR);
> +
> +       return base_slice + (base_slice/ELV_SLICE_SCALE * (4 - prio));
> +}
> +
> +static inline int
> +elv_prio_to_slice(struct elv_fq_data *efqd, struct io_queue *ioq)
> +{
> +       return elv_prio_slice(efqd, elv_ioq_sync(ioq), ioq->entity.ioprio);
> +}
> +
> +/* Mainly the BFQ scheduling code Follows */
> +
> +/*
> + * Shift for timestamp calculations.  This actually limits the maximum
> + * service allowed in one timestamp delta (small shift values increase it),
> + * the maximum total weight that can be used for the queues in the system
> + * (big shift values increase it), and the period of virtual time wraparounds.
> + */
> +#define WFQ_SERVICE_SHIFT      22
> +
> +/**
> + * bfq_gt - compare two timestamps.
> + * @a: first ts.
> + * @b: second ts.
> + *
> + * Return @a > @b, dealing with wrapping correctly.
> + */
> +static inline int bfq_gt(bfq_timestamp_t a, bfq_timestamp_t b)
> +{
> +       return (s64)(a - b) > 0;
> +}
> +
> +/**
> + * bfq_delta - map service into the virtual time domain.
> + * @service: amount of service.
> + * @weight: scale factor.
> + */
> +static inline bfq_timestamp_t bfq_delta(bfq_service_t service,
> +                                       bfq_weight_t weight)
> +{
> +       bfq_timestamp_t d = (bfq_timestamp_t)service << WFQ_SERVICE_SHIFT;
> +
> +       do_div(d, weight);
> +       return d;
> +}
> +
> +/**
> + * bfq_calc_finish - assign the finish time to an entity.
> + * @entity: the entity to act upon.
> + * @service: the service to be charged to the entity.
> + */
> +static inline void bfq_calc_finish(struct io_entity *entity,
> +                                  bfq_service_t service)
> +{
> +       BUG_ON(entity->weight == 0);
> +
> +       entity->finish = entity->start + bfq_delta(service, entity->weight);
> +}
> +
> +static inline struct io_queue *io_entity_to_ioq(struct io_entity *entity)
> +{
> +       struct io_queue *ioq = NULL;
> +
> +       BUG_ON(entity == NULL);
> +       if (entity->my_sched_data == NULL)
> +               ioq = container_of(entity, struct io_queue, entity);
> +       return ioq;
> +}
> +
> +/**
> + * bfq_entity_of - get an entity from a node.
> + * @node: the node field of the entity.
> + *
> + * Convert a node pointer to the relative entity.  This is used only
> + * to simplify the logic of some functions and not as the generic
> + * conversion mechanism because, e.g., in the tree walking functions,
> + * the check for a %NULL value would be redundant.
> + */
> +static inline struct io_entity *bfq_entity_of(struct rb_node *node)
> +{
> +       struct io_entity *entity = NULL;
> +
> +       if (node != NULL)
> +               entity = rb_entry(node, struct io_entity, rb_node);
> +
> +       return entity;
> +}
> +
> +/**
> + * bfq_extract - remove an entity from a tree.
> + * @root: the tree root.
> + * @entity: the entity to remove.
> + */
> +static inline void bfq_extract(struct rb_root *root, struct io_entity *entity)
> +{
> +       BUG_ON(entity->tree != root);
> +
> +       entity->tree = NULL;
> +       rb_erase(&entity->rb_node, root);
> +}
> +
> +/**
> + * bfq_idle_extract - extract an entity from the idle tree.
> + * @st: the service tree of the owning @entity.
> + * @entity: the entity being removed.
> + */
> +static void bfq_idle_extract(struct io_service_tree *st,
> +                               struct io_entity *entity)
> +{
> +       struct rb_node *next;
> +       struct io_queue *ioq = io_entity_to_ioq(entity);
> +
> +       BUG_ON(entity->tree != &st->idle);
> +
> +       if (entity == st->first_idle) {
> +               next = rb_next(&entity->rb_node);
> +               st->first_idle = bfq_entity_of(next);
> +       }
> +
> +       if (entity == st->last_idle) {
> +               next = rb_prev(&entity->rb_node);
> +               st->last_idle = bfq_entity_of(next);
> +       }
> +
> +       bfq_extract(&st->idle, entity);
> +
> +       /* Delete queue from idle list */
> +       if (ioq)
> +               list_del(&ioq->queue_list);
> +}
> +
> +/**
> + * bfq_insert - generic tree insertion.
> + * @root: tree root.
> + * @entity: entity to insert.
> + *
> + * This is used for the idle and the active tree, since they are both
> + * ordered by finish time.
> + */
> +static void bfq_insert(struct rb_root *root, struct io_entity *entity)
> +{
> +       struct io_entity *entry;
> +       struct rb_node **node = &root->rb_node;
> +       struct rb_node *parent = NULL;
> +
> +       BUG_ON(entity->tree != NULL);
> +
> +       while (*node != NULL) {
> +               parent = *node;
> +               entry = rb_entry(parent, struct io_entity, rb_node);
> +
> +               if (bfq_gt(entry->finish, entity->finish))
> +                       node = &parent->rb_left;
> +               else
> +                       node = &parent->rb_right;
> +       }
> +
> +       rb_link_node(&entity->rb_node, parent, node);
> +       rb_insert_color(&entity->rb_node, root);
> +
> +       entity->tree = root;
> +}
> +
> +/**
> + * bfq_update_min - update the min_start field of a entity.
> + * @entity: the entity to update.
> + * @node: one of its children.
> + *
> + * This function is called when @entity may store an invalid value for
> + * min_start due to updates to the active tree.  The function  assumes
> + * that the subtree rooted at @node (which may be its left or its right
> + * child) has a valid min_start value.
> + */
> +static inline void bfq_update_min(struct io_entity *entity,
> +                                       struct rb_node *node)
> +{
> +       struct io_entity *child;
> +
> +       if (node != NULL) {
> +               child = rb_entry(node, struct io_entity, rb_node);
> +               if (bfq_gt(entity->min_start, child->min_start))
> +                       entity->min_start = child->min_start;
> +       }
> +}
> +
> +/**
> + * bfq_update_active_node - recalculate min_start.
> + * @node: the node to update.
> + *
> + * @node may have changed position or one of its children may have moved,
> + * this function updates its min_start value.  The left and right subtrees
> + * are assumed to hold a correct min_start value.
> + */
> +static inline void bfq_update_active_node(struct rb_node *node)
> +{
> +       struct io_entity *entity = rb_entry(node, struct io_entity, rb_node);
> +
> +       entity->min_start = entity->start;
> +       bfq_update_min(entity, node->rb_right);
> +       bfq_update_min(entity, node->rb_left);
> +}
> +
> +/**
> + * bfq_update_active_tree - update min_start for the whole active tree.
> + * @node: the starting node.
> + *
> + * @node must be the deepest modified node after an update.  This function
> + * updates its min_start using the values held by its children, assuming
> + * that they did not change, and then updates all the nodes that may have
> + * changed in the path to the root.  The only nodes that may have changed
> + * are the ones in the path or their siblings.
> + */
> +static void bfq_update_active_tree(struct rb_node *node)
> +{
> +       struct rb_node *parent;
> +
> +up:
> +       bfq_update_active_node(node);
> +
> +       parent = rb_parent(node);
> +       if (parent == NULL)
> +               return;
> +
> +       if (node == parent->rb_left && parent->rb_right != NULL)
> +               bfq_update_active_node(parent->rb_right);
> +       else if (parent->rb_left != NULL)
> +               bfq_update_active_node(parent->rb_left);
> +
> +       node = parent;
> +       goto up;
> +}
> +
> +/**
> + * bfq_active_insert - insert an entity in the active tree of its group/device.
> + * @st: the service tree of the entity.
> + * @entity: the entity being inserted.
> + *
> + * The active tree is ordered by finish time, but an extra key is kept
> + * per each node, containing the minimum value for the start times of
> + * its children (and the node itself), so it's possible to search for
> + * the eligible node with the lowest finish time in logarithmic time.
> + */
> +static void bfq_active_insert(struct io_service_tree *st,
> +                                       struct io_entity *entity)
> +{
> +       struct rb_node *node = &entity->rb_node;
> +
> +       bfq_insert(&st->active, entity);
> +
> +       if (node->rb_left != NULL)
> +               node = node->rb_left;
> +       else if (node->rb_right != NULL)
> +               node = node->rb_right;
> +
> +       bfq_update_active_tree(node);
> +}
> +
> +/**
> + * bfq_ioprio_to_weight - calc a weight from an ioprio.
> + * @ioprio: the ioprio value to convert.
> + */
> +static bfq_weight_t bfq_ioprio_to_weight(int ioprio)
> +{
> +       WARN_ON(ioprio < 0 || ioprio >= IOPRIO_BE_NR);
> +       return IOPRIO_BE_NR - ioprio;
> +}
> +
> +void bfq_get_entity(struct io_entity *entity)
> +{
> +       struct io_queue *ioq = io_entity_to_ioq(entity);
> +
> +       if (ioq)
> +               elv_get_ioq(ioq);
> +}
> +
> +void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
> +{
> +       entity->ioprio = entity->new_ioprio;
> +       entity->ioprio_class = entity->new_ioprio_class;
> +       entity->sched_data = &iog->sched_data;
> +}
> +
> +/**
> + * bfq_find_deepest - find the deepest node that an extraction can modify.
> + * @node: the node being removed.
> + *
> + * Do the first step of an extraction in an rb tree, looking for the
> + * node that will replace @node, and returning the deepest node that
> + * the following modifications to the tree can touch.  If @node is the
> + * last node in the tree return %NULL.
> + */
> +static struct rb_node *bfq_find_deepest(struct rb_node *node)
> +{
> +       struct rb_node *deepest;
> +
> +       if (node->rb_right == NULL && node->rb_left == NULL)
> +               deepest = rb_parent(node);
> +       else if (node->rb_right == NULL)
> +               deepest = node->rb_left;
> +       else if (node->rb_left == NULL)
> +               deepest = node->rb_right;
> +       else {
> +               deepest = rb_next(node);
> +               if (deepest->rb_right != NULL)
> +                       deepest = deepest->rb_right;
> +               else if (rb_parent(deepest) != node)
> +                       deepest = rb_parent(deepest);
> +       }
> +
> +       return deepest;
> +}
> +
> +/**
> + * bfq_active_extract - remove an entity from the active tree.
> + * @st: the service_tree containing the tree.
> + * @entity: the entity being removed.
> + */
> +static void bfq_active_extract(struct io_service_tree *st,
> +                               struct io_entity *entity)
> +{
> +       struct rb_node *node;
> +
> +       node = bfq_find_deepest(&entity->rb_node);
> +       bfq_extract(&st->active, entity);
> +
> +       if (node != NULL)
> +               bfq_update_active_tree(node);
> +}
> +
> +/**
> + * bfq_idle_insert - insert an entity into the idle tree.
> + * @st: the service tree containing the tree.
> + * @entity: the entity to insert.
> + */
> +static void bfq_idle_insert(struct io_service_tree *st,
> +                                       struct io_entity *entity)
> +{
> +       struct io_entity *first_idle = st->first_idle;
> +       struct io_entity *last_idle = st->last_idle;
> +       struct io_queue *ioq = io_entity_to_ioq(entity);
> +
> +       if (first_idle == NULL || bfq_gt(first_idle->finish, entity->finish))
> +               st->first_idle = entity;
> +       if (last_idle == NULL || bfq_gt(entity->finish, last_idle->finish))
> +               st->last_idle = entity;
> +
> +       bfq_insert(&st->idle, entity);
> +
> +       /* Add this queue to idle list */
> +       if (ioq)
> +               list_add(&ioq->queue_list, &ioq->efqd->idle_list);
> +}
> +
> +/**
> + * bfq_forget_entity - remove an entity from the wfq trees.
> + * @st: the service tree.
> + * @entity: the entity being removed.
> + *
> + * Update the device status and forget everything about @entity, putting
> + * the device reference to it, if it is a queue.  Entities belonging to
> + * groups are not refcounted.
> + */
> +static void bfq_forget_entity(struct io_service_tree *st,
> +                               struct io_entity *entity)
> +{
> +       struct io_queue *ioq = NULL;
> +
> +       BUG_ON(!entity->on_st);
> +       entity->on_st = 0;
> +       st->wsum -= entity->weight;
> +       ioq = io_entity_to_ioq(entity);
> +       if (!ioq)
> +               return;
> +       elv_put_ioq(ioq);
> +}
> +
> +/**
> + * bfq_put_idle_entity - release the idle tree ref of an entity.
> + * @st: service tree for the entity.
> + * @entity: the entity being released.
> + */
> +void bfq_put_idle_entity(struct io_service_tree *st,
> +                               struct io_entity *entity)
> +{
> +       bfq_idle_extract(st, entity);
> +       bfq_forget_entity(st, entity);
> +}
> +
> +/**
> + * bfq_forget_idle - update the idle tree if necessary.
> + * @st: the service tree to act upon.
> + *
> + * To preserve the global O(log N) complexity we only remove one entry here;
> + * as the idle tree will not grow indefinitely this can be done safely.
> + */
> +void bfq_forget_idle(struct io_service_tree *st)
> +{
> +       struct io_entity *first_idle = st->first_idle;
> +       struct io_entity *last_idle = st->last_idle;
> +
> +       if (RB_EMPTY_ROOT(&st->active) && last_idle != NULL &&
> +           !bfq_gt(last_idle->finish, st->vtime)) {
> +               /*
> +                * Active tree is empty. Pull back vtime to finish time of
> +                * last idle entity on idle tree.
> +                * Rational seems to be that it reduces the possibility of
> +                * vtime wraparound (bfq_gt(V-F) < 0).
> +                */
> +               st->vtime = last_idle->finish;
> +       }
> +
> +       if (first_idle != NULL && !bfq_gt(first_idle->finish, st->vtime))
> +               bfq_put_idle_entity(st, first_idle);
> +}
> +
> +
> +static struct io_service_tree *
> +__bfq_entity_update_prio(struct io_service_tree *old_st,
> +                               struct io_entity *entity)
> +{
> +       struct io_service_tree *new_st = old_st;
> +       struct io_queue *ioq = io_entity_to_ioq(entity);
> +
> +       if (entity->ioprio_changed) {
> +               entity->ioprio = entity->new_ioprio;
> +               entity->ioprio_class = entity->new_ioprio_class;
> +               entity->ioprio_changed = 0;
> +
> +               /*
> +                * Also update the scaled budget for ioq. Group will get the
> +                * updated budget once ioq is selected to run next.
> +                */
> +               if (ioq) {
> +                       struct elv_fq_data *efqd = ioq->efqd;
> +                       entity->budget = elv_prio_to_slice(efqd, ioq);
> +               }
> +
> +               old_st->wsum -= entity->weight;
> +               entity->weight = bfq_ioprio_to_weight(entity->ioprio);
> +
> +               /*
> +                * NOTE: here we may be changing the weight too early,
> +                * this will cause unfairness.  The correct approach
> +                * would have required additional complexity to defer
> +                * weight changes to the proper time instants (i.e.,
> +                * when entity->finish <= old_st->vtime).
> +                */
> +               new_st = io_entity_service_tree(entity);
> +               new_st->wsum += entity->weight;
> +
> +               if (new_st != old_st)
> +                       entity->start = new_st->vtime;
> +       }
> +
> +       return new_st;
> +}
> +
> +/**
> + * __bfq_activate_entity - activate an entity.
> + * @entity: the entity being activated.
> + *
> + * Called whenever an entity is activated, i.e., it is not active and one
> + * of its children receives a new request, or has to be reactivated due to
> + * budget exhaustion.  It uses the current budget of the entity (and the
> + * service received if @entity is active) of the queue to calculate its
> + * timestamps.
> + */
> +static void __bfq_activate_entity(struct io_entity *entity, int add_front)
> +{
> +       struct io_sched_data *sd = entity->sched_data;
> +       struct io_service_tree *st = io_entity_service_tree(entity);
> +
> +       if (entity == sd->active_entity) {
> +               BUG_ON(entity->tree != NULL);
> +               /*
> +                * If we are requeueing the current entity we have
> +                * to take care of not charging to it service it has
> +                * not received.
> +                */
> +               bfq_calc_finish(entity, entity->service);
> +               entity->start = entity->finish;
> +               sd->active_entity = NULL;
> +       } else if (entity->tree == &st->active) {
> +               /*
> +                * Requeueing an entity due to a change of some
> +                * next_active entity below it.  We reuse the old
> +                * start time.
> +                */
> +               bfq_active_extract(st, entity);
> +       } else if (entity->tree == &st->idle) {
> +               /*
> +                * Must be on the idle tree, bfq_idle_extract() will
> +                * check for that.
> +                */
> +               bfq_idle_extract(st, entity);
> +               entity->start = bfq_gt(st->vtime, entity->finish) ?
> +                                      st->vtime : entity->finish;
> +       } else {
> +               /*
> +                * The finish time of the entity may be invalid, and
> +                * it is in the past for sure, otherwise the queue
> +                * would have been on the idle tree.
> +                */
> +               entity->start = st->vtime;
> +               st->wsum += entity->weight;
> +               bfq_get_entity(entity);
> +
> +               BUG_ON(entity->on_st);
> +               entity->on_st = 1;
> +       }
> +
> +       st = __bfq_entity_update_prio(st, entity);
> +       /*
> +        * This is to emulate cfq like functionality where preemption can
> +        * happen with-in same class, like sync queue preempting async queue
> +        * May be this is not a very good idea from fairness point of view
> +        * as preempting queue gains share. Keeping it for now.
> +        */
> +       if (add_front) {
> +               struct io_entity *next_entity;
> +
> +               /*
> +                * Determine the entity which will be dispatched next
> +                * Use sd->next_active once hierarchical patch is applied
> +                */
> +               next_entity = bfq_lookup_next_entity(sd, 0);
> +
> +               if (next_entity && next_entity != entity) {
> +                       struct io_service_tree *new_st;
> +                       bfq_timestamp_t delta;
> +
> +                       new_st = io_entity_service_tree(next_entity);
> +
> +                       /*
> +                        * At this point, both entities should belong to
> +                        * same service tree as cross service tree preemption
> +                        * is automatically taken care by algorithm
> +                        */
> +                       BUG_ON(new_st != st);
> +                       entity->finish = next_entity->finish - 1;
> +                       delta = bfq_delta(entity->budget, entity->weight);
> +                       entity->start = entity->finish - delta;
> +                       if (bfq_gt(entity->start, st->vtime))
> +                               entity->start = st->vtime;
> +               }
> +       } else {
> +               bfq_calc_finish(entity, entity->budget);
> +       }
> +       bfq_active_insert(st, entity);
> +}
> +
> +/**
> + * bfq_activate_entity - activate an entity.
> + * @entity: the entity to activate.
> + */
> +void bfq_activate_entity(struct io_entity *entity, int add_front)
> +{
> +       __bfq_activate_entity(entity, add_front);
> +}
> +
> +/**
> + * __bfq_deactivate_entity - deactivate an entity from its service tree.
> + * @entity: the entity to deactivate.
> + * @requeue: if false, the entity will not be put into the idle tree.
> + *
> + * Deactivate an entity, independently from its previous state.  If the
> + * entity was not on a service tree just return, otherwise if it is on
> + * any scheduler tree, extract it from that tree, and if necessary
> + * and if the caller did not specify @requeue, put it on the idle tree.
> + *
> + */
> +int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
> +{
> +       struct io_sched_data *sd = entity->sched_data;
> +       struct io_service_tree *st = io_entity_service_tree(entity);
> +       int was_active = entity == sd->active_entity;
> +       int ret = 0;
> +
> +       if (!entity->on_st)
> +               return 0;
> +
> +       BUG_ON(was_active && entity->tree != NULL);
> +
> +       if (was_active) {
> +               bfq_calc_finish(entity, entity->service);
> +               sd->active_entity = NULL;
> +       } else if (entity->tree == &st->active)
> +               bfq_active_extract(st, entity);
> +       else if (entity->tree == &st->idle)
> +               bfq_idle_extract(st, entity);
> +       else if (entity->tree != NULL)
> +               BUG();
> +
> +       if (!requeue || !bfq_gt(entity->finish, st->vtime))
> +               bfq_forget_entity(st, entity);
> +       else
> +               bfq_idle_insert(st, entity);
> +
> +       BUG_ON(sd->active_entity == entity);
> +
> +       return ret;
> +}
> +
> +/**
> + * bfq_deactivate_entity - deactivate an entity.
> + * @entity: the entity to deactivate.
> + * @requeue: true if the entity can be put on the idle tree
> + */
> +void bfq_deactivate_entity(struct io_entity *entity, int requeue)
> +{
> +       __bfq_deactivate_entity(entity, requeue);
> +}
> +
> +/**
> + * bfq_update_vtime - update vtime if necessary.
> + * @st: the service tree to act upon.
> + *
> + * If necessary update the service tree vtime to have at least one
> + * eligible entity, skipping to its start time.  Assumes that the
> + * active tree of the device is not empty.
> + *
> + * NOTE: this hierarchical implementation updates vtimes quite often,
> + * we may end up with reactivated tasks getting timestamps after a
> + * vtime skip done because we needed a ->first_active entity on some
> + * intermediate node.
> + */
> +static void bfq_update_vtime(struct io_service_tree *st)
> +{
> +       struct io_entity *entry;
> +       struct rb_node *node = st->active.rb_node;
> +
> +       entry = rb_entry(node, struct io_entity, rb_node);
> +       if (bfq_gt(entry->min_start, st->vtime)) {
> +               st->vtime = entry->min_start;
> +               bfq_forget_idle(st);
> +       }
> +}
> +
> +/**
> + * bfq_first_active - find the eligible entity with the smallest finish time
> + * @st: the service tree to select from.
> + *
> + * This function searches the first schedulable entity, starting from the
> + * root of the tree and going on the left every time on this side there is
> + * a subtree with at least one eligible (start <= vtime) entity.  The path
> + * on the right is followed only if a) the left subtree contains no eligible
> + * entities and b) no eligible entity has been found yet.
> + */
> +static struct io_entity *bfq_first_active_entity(struct io_service_tree *st)
> +{
> +       struct io_entity *entry, *first = NULL;
> +       struct rb_node *node = st->active.rb_node;
> +
> +       while (node != NULL) {
> +               entry = rb_entry(node, struct io_entity, rb_node);
> +left:
> +               if (!bfq_gt(entry->start, st->vtime))
> +                       first = entry;
> +
> +               BUG_ON(bfq_gt(entry->min_start, st->vtime));
> +
> +               if (node->rb_left != NULL) {
> +                       entry = rb_entry(node->rb_left,
> +                                        struct io_entity, rb_node);
> +                       if (!bfq_gt(entry->min_start, st->vtime)) {
> +                               node = node->rb_left;
> +                               goto left;
> +                       }
> +               }
> +               if (first != NULL)
> +                       break;
> +               node = node->rb_right;
> +       }
> +
> +       BUG_ON(first == NULL && !RB_EMPTY_ROOT(&st->active));
> +       return first;
> +}
> +
> +/**
> + * __bfq_lookup_next_entity - return the first eligible entity in @st.
> + * @st: the service tree.
> + *
> + * Update the virtual time in @st and return the first eligible entity
> + * it contains.
> + */
> +static struct io_entity *__bfq_lookup_next_entity(struct io_service_tree *st)
> +{
> +       struct io_entity *entity;
> +
> +       if (RB_EMPTY_ROOT(&st->active))
> +               return NULL;
> +
> +       bfq_update_vtime(st);

Vivek, Paolo, Fabio,
Over here we call bfq_update_vtime(), and this function could have
been called even when we are just doing a lookup (and not an extract).
So vtime is updated while we are not really selecting the next queue
for service (for an example, see elv_preempt_queue()). This can result
in a call to update_vtime when only an entity with small weight (say
weight=1) is backlogged and another entity with bigger weight (say 10)
is getting serviced so it is not in the tree (we extract the entity
which is getting service). This results in a big vtime jump to the
start time of the entity with weight 1 (entity of weight 1 would have
big start times, as it has small weight). Now when another entity with
bigger weight (say 90) gets backlogged, it is assigned a new vtime
from service tree's vtime, causing it to get a big value. In the
meanwhile, iog for weight 10 keeps getting service for many quantums,
as it was continuously backlogged.

The problem happens because we extract an entity (removing it from the
tree) while it is getting service, and do vtime jumps based on what is
still in the tree. I think we need to add an extra check on the vtime
of the entity in service, before we take a vtime jump.

I have actually seen this happening when trying to debug on of my
tests. Please let me know what you think.

> +       entity = bfq_first_active_entity(st);
> +       BUG_ON(bfq_gt(entity->start, st->vtime));
> +
> +       return entity;
> +}
> +
> +/**
> + * bfq_lookup_next_entity - return the first eligible entity in @sd.
> + * @sd: the sched_data.
> + * @extract: if true the returned entity will be also extracted from @sd.
> + *
> + * NOTE: since we cache the next_active entity at each level of the
> + * hierarchy, the complexity of the lookup can be decreased with
> + * absolutely no effort just returning the cached next_active value;
> + * we prefer to do full lookups to test the consistency of * the data
> + * structures.
> + */
> +struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
> +                                                int extract)
> +{
> +       struct io_service_tree *st = sd->service_tree;
> +       struct io_entity *entity;
> +       int i;
> +
> +       /*
> +        * One can check for which will be next selected entity without
> +        * expiring the current one.
> +        */
> +       BUG_ON(extract && sd->active_entity != NULL);
> +
> +       for (i = 0; i < IO_IOPRIO_CLASSES; i++, st++) {
> +               entity = __bfq_lookup_next_entity(st);
> +               if (entity != NULL) {
> +                       if (extract) {
> +                               bfq_active_extract(st, entity);
> +                               sd->active_entity = entity;
> +                       }
> +                       break;
> +               }
> +       }
> +
> +       return entity;
> +}
> +
> +void entity_served(struct io_entity *entity, bfq_service_t served)
> +{
> +       struct io_service_tree *st;
> +
> +       st = io_entity_service_tree(entity);
> +       entity->service += served;
> +       BUG_ON(st->wsum == 0);
> +       st->vtime += bfq_delta(served, st->wsum);
> +       bfq_forget_idle(st);
> +}
> +
> +/* Elevator fair queuing function */
> +struct io_queue *rq_ioq(struct request *rq)
> +{
> +       return rq->ioq;
> +}
> +
> +static inline struct io_queue *elv_active_ioq(struct elevator_queue *e)
> +{
> +       return e->efqd.active_queue;
> +}
> +
> +void *elv_active_sched_queue(struct elevator_queue *e)
> +{
> +       return ioq_sched_queue(elv_active_ioq(e));
> +}
> +EXPORT_SYMBOL(elv_active_sched_queue);
> +
> +int elv_nr_busy_ioq(struct elevator_queue *e)
> +{
> +       return e->efqd.busy_queues;
> +}
> +EXPORT_SYMBOL(elv_nr_busy_ioq);
> +
> +int elv_nr_busy_rt_ioq(struct elevator_queue *e)
> +{
> +       return e->efqd.busy_rt_queues;
> +}
> +EXPORT_SYMBOL(elv_nr_busy_rt_ioq);
> +
> +int elv_hw_tag(struct elevator_queue *e)
> +{
> +       return e->efqd.hw_tag;
> +}
> +EXPORT_SYMBOL(elv_hw_tag);
> +
> +/* Helper functions for operating on elevator idle slice timer */
> +int elv_mod_idle_slice_timer(struct elevator_queue *eq, unsigned long expires)
> +{
> +       struct elv_fq_data *efqd = &eq->efqd;
> +
> +       return mod_timer(&efqd->idle_slice_timer, expires);
> +}
> +EXPORT_SYMBOL(elv_mod_idle_slice_timer);
> +
> +int elv_del_idle_slice_timer(struct elevator_queue *eq)
> +{
> +       struct elv_fq_data *efqd = &eq->efqd;
> +
> +       return del_timer(&efqd->idle_slice_timer);
> +}
> +EXPORT_SYMBOL(elv_del_idle_slice_timer);
> +
> +unsigned int elv_get_slice_idle(struct elevator_queue *eq)
> +{
> +       return eq->efqd.elv_slice_idle;
> +}
> +EXPORT_SYMBOL(elv_get_slice_idle);
> +
> +void elv_ioq_served(struct io_queue *ioq, bfq_service_t served)
> +{
> +       entity_served(&ioq->entity, served);
> +}
> +
> +/* Tells whether ioq is queued in root group or not */
> +static inline int is_root_group_ioq(struct request_queue *q,
> +                                       struct io_queue *ioq)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +
> +       return (ioq->entity.sched_data == &efqd->root_group->sched_data);
> +}
> +
> +/* Functions to show and store elv_idle_slice value through sysfs */
> +ssize_t elv_slice_idle_show(struct request_queue *q, char *name)
> +{
> +       struct elv_fq_data *efqd;
> +       unsigned int data;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(q->queue_lock, flags);
> +       efqd = &q->elevator->efqd;
> +       data = jiffies_to_msecs(efqd->elv_slice_idle);
> +       spin_unlock_irqrestore(q->queue_lock, flags);
> +       return sprintf(name, "%d\n", data);
> +}
> +
> +ssize_t elv_slice_idle_store(struct request_queue *q, const char *name,
> +                         size_t count)
> +{
> +       struct elv_fq_data *efqd;
> +       unsigned int data;
> +       unsigned long flags;
> +
> +       char *p = (char *)name;
> +
> +       data = simple_strtoul(p, &p, 10);
> +
> +       if (data < 0)
> +               data = 0;
> +       else if (data > INT_MAX)
> +               data = INT_MAX;
> +
> +       data = msecs_to_jiffies(data);
> +
> +       spin_lock_irqsave(q->queue_lock, flags);
> +       efqd = &q->elevator->efqd;
> +       efqd->elv_slice_idle = data;
> +       spin_unlock_irqrestore(q->queue_lock, flags);
> +
> +       return count;
> +}
> +
> +/* Functions to show and store elv_slice_sync value through sysfs */
> +ssize_t elv_slice_sync_show(struct request_queue *q, char *name)
> +{
> +       struct elv_fq_data *efqd;
> +       unsigned int data;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(q->queue_lock, flags);
> +       efqd = &q->elevator->efqd;
> +       data = efqd->elv_slice[1];
> +       spin_unlock_irqrestore(q->queue_lock, flags);
> +       return sprintf(name, "%d\n", data);
> +}
> +
> +ssize_t elv_slice_sync_store(struct request_queue *q, const char *name,
> +                         size_t count)
> +{
> +       struct elv_fq_data *efqd;
> +       unsigned int data;
> +       unsigned long flags;
> +
> +       char *p = (char *)name;
> +
> +       data = simple_strtoul(p, &p, 10);
> +
> +       if (data < 0)
> +               data = 0;
> +       /* 100ms is the limit for now*/
> +       else if (data > 100)
> +               data = 100;
> +
> +       spin_lock_irqsave(q->queue_lock, flags);
> +       efqd = &q->elevator->efqd;
> +       efqd->elv_slice[1] = data;
> +       spin_unlock_irqrestore(q->queue_lock, flags);
> +
> +       return count;
> +}
> +
> +/* Functions to show and store elv_slice_async value through sysfs */
> +ssize_t elv_slice_async_show(struct request_queue *q, char *name)
> +{
> +       struct elv_fq_data *efqd;
> +       unsigned int data;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(q->queue_lock, flags);
> +       efqd = &q->elevator->efqd;
> +       data = efqd->elv_slice[0];
> +       spin_unlock_irqrestore(q->queue_lock, flags);
> +       return sprintf(name, "%d\n", data);
> +}
> +
> +ssize_t elv_slice_async_store(struct request_queue *q, const char *name,
> +                         size_t count)
> +{
> +       struct elv_fq_data *efqd;
> +       unsigned int data;
> +       unsigned long flags;
> +
> +       char *p = (char *)name;
> +
> +       data = simple_strtoul(p, &p, 10);
> +
> +       if (data < 0)
> +               data = 0;
> +       /* 100ms is the limit for now*/
> +       else if (data > 100)
> +               data = 100;
> +
> +       spin_lock_irqsave(q->queue_lock, flags);
> +       efqd = &q->elevator->efqd;
> +       efqd->elv_slice[0] = data;
> +       spin_unlock_irqrestore(q->queue_lock, flags);
> +
> +       return count;
> +}
> +
> +void elv_schedule_dispatch(struct request_queue *q)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +
> +       if (elv_nr_busy_ioq(q->elevator)) {
> +               elv_log(efqd, "schedule dispatch");
> +               kblockd_schedule_work(efqd->queue, &efqd->unplug_work);
> +       }
> +}
> +EXPORT_SYMBOL(elv_schedule_dispatch);
> +
> +void elv_kick_queue(struct work_struct *work)
> +{
> +       struct elv_fq_data *efqd =
> +               container_of(work, struct elv_fq_data, unplug_work);
> +       struct request_queue *q = efqd->queue;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(q->queue_lock, flags);
> +       blk_start_queueing(q);
> +       spin_unlock_irqrestore(q->queue_lock, flags);
> +}
> +
> +void elv_shutdown_timer_wq(struct elevator_queue *e)
> +{
> +       del_timer_sync(&e->efqd.idle_slice_timer);
> +       cancel_work_sync(&e->efqd.unplug_work);
> +}
> +EXPORT_SYMBOL(elv_shutdown_timer_wq);
> +
> +void elv_ioq_set_prio_slice(struct request_queue *q, struct io_queue *ioq)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +
> +       ioq->slice_end = jiffies + ioq->entity.budget;
> +       elv_log_ioq(efqd, ioq, "set_slice=%lu", ioq->entity.budget);
> +}
> +
> +static void elv_ioq_update_io_thinktime(struct io_queue *ioq)
> +{
> +       struct elv_fq_data *efqd = ioq->efqd;
> +       unsigned long elapsed = jiffies - ioq->last_end_request;
> +       unsigned long ttime = min(elapsed, 2UL * efqd->elv_slice_idle);
> +
> +       ioq->ttime_samples = (7*ioq->ttime_samples + 256) / 8;
> +       ioq->ttime_total = (7*ioq->ttime_total + 256*ttime) / 8;
> +       ioq->ttime_mean = (ioq->ttime_total + 128) / ioq->ttime_samples;
> +}
> +
> +/*
> + * Disable idle window if the process thinks too long.
> + * This idle flag can also be updated by io scheduler.
> + */
> +static void elv_ioq_update_idle_window(struct elevator_queue *eq,
> +                               struct io_queue *ioq, struct request *rq)
> +{
> +       int old_idle, enable_idle;
> +       struct elv_fq_data *efqd = ioq->efqd;
> +
> +       /*
> +        * Don't idle for async or idle io prio class
> +        */
> +       if (!elv_ioq_sync(ioq) || elv_ioq_class_idle(ioq))
> +               return;
> +
> +       enable_idle = old_idle = elv_ioq_idle_window(ioq);
> +
> +       if (!efqd->elv_slice_idle)
> +               enable_idle = 0;
> +       else if (ioq_sample_valid(ioq->ttime_samples)) {
> +               if (ioq->ttime_mean > efqd->elv_slice_idle)
> +                       enable_idle = 0;
> +               else
> +                       enable_idle = 1;
> +       }
> +
> +       /*
> +        * From think time perspective idle should be enabled. Check with
> +        * io scheduler if it wants to disable idling based on additional
> +        * considrations like seek pattern.
> +        */
> +       if (enable_idle) {
> +               if (eq->ops->elevator_update_idle_window_fn)
> +                       enable_idle = eq->ops->elevator_update_idle_window_fn(
> +                                               eq, ioq->sched_queue, rq);
> +               if (!enable_idle)
> +                       elv_log_ioq(efqd, ioq, "iosched disabled idle");
> +       }
> +
> +       if (old_idle != enable_idle) {
> +               elv_log_ioq(efqd, ioq, "idle=%d", enable_idle);
> +               if (enable_idle)
> +                       elv_mark_ioq_idle_window(ioq);
> +               else
> +                       elv_clear_ioq_idle_window(ioq);
> +       }
> +}
> +
> +struct io_queue *elv_alloc_ioq(struct request_queue *q, gfp_t gfp_mask)
> +{
> +       struct io_queue *ioq = NULL;
> +
> +       ioq = kmem_cache_alloc_node(elv_ioq_pool, gfp_mask, q->node);
> +       return ioq;
> +}
> +EXPORT_SYMBOL(elv_alloc_ioq);
> +
> +void elv_free_ioq(struct io_queue *ioq)
> +{
> +       kmem_cache_free(elv_ioq_pool, ioq);
> +}
> +EXPORT_SYMBOL(elv_free_ioq);
> +
> +int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq,
> +                       void *sched_queue, int ioprio_class, int ioprio,
> +                       int is_sync)
> +{
> +       struct elv_fq_data *efqd = &eq->efqd;
> +       struct io_group *iog = io_lookup_io_group_current(efqd->queue);
> +
> +       RB_CLEAR_NODE(&ioq->entity.rb_node);
> +       atomic_set(&ioq->ref, 0);
> +       ioq->efqd = efqd;
> +       elv_ioq_set_ioprio_class(ioq, ioprio_class);
> +       elv_ioq_set_ioprio(ioq, ioprio);
> +       ioq->pid = current->pid;
> +       ioq->sched_queue = sched_queue;
> +       if (is_sync && !elv_ioq_class_idle(ioq))
> +               elv_mark_ioq_idle_window(ioq);
> +       bfq_init_entity(&ioq->entity, iog);
> +       ioq->entity.budget = elv_prio_to_slice(efqd, ioq);
> +       return 0;
> +}
> +EXPORT_SYMBOL(elv_init_ioq);
> +
> +void elv_put_ioq(struct io_queue *ioq)
> +{
> +       struct elv_fq_data *efqd = ioq->efqd;
> +       struct elevator_queue *e = container_of(efqd, struct elevator_queue,
> +                                               efqd);
> +
> +       BUG_ON(atomic_read(&ioq->ref) <= 0);
> +       if (!atomic_dec_and_test(&ioq->ref))
> +               return;
> +       BUG_ON(ioq->nr_queued);
> +       BUG_ON(ioq->entity.tree != NULL);
> +       BUG_ON(elv_ioq_busy(ioq));
> +       BUG_ON(efqd->active_queue == ioq);
> +
> +       /* Can be called by outgoing elevator. Don't use q */
> +       BUG_ON(!e->ops->elevator_free_sched_queue_fn);
> +
> +       e->ops->elevator_free_sched_queue_fn(e, ioq->sched_queue);
> +       elv_log_ioq(efqd, ioq, "put_queue");
> +       elv_free_ioq(ioq);
> +}
> +EXPORT_SYMBOL(elv_put_ioq);
> +
> +void elv_release_ioq(struct elevator_queue *e, struct io_queue **ioq_ptr)
> +{
> +       struct io_queue *ioq = *ioq_ptr;
> +
> +       if (ioq != NULL) {
> +               /* Drop the reference taken by the io group */
> +               elv_put_ioq(ioq);
> +               *ioq_ptr = NULL;
> +       }
> +}
> +
> +/*
> + * Normally next io queue to be served is selected from the service tree.
> + * This function allows one to choose a specific io queue to run next
> + * out of order. This is primarily to accomodate the close_cooperator
> + * feature of cfq.
> + *
> + * Currently it is done only for root level as to begin with supporting
> + * close cooperator feature only for root group to make sure default
> + * cfq behavior in flat hierarchy is not changed.
> + */
> +void elv_set_next_ioq(struct request_queue *q, struct io_queue *ioq)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +       struct io_entity *entity = &ioq->entity;
> +       struct io_sched_data *sd = &efqd->root_group->sched_data;
> +       struct io_service_tree *st = io_entity_service_tree(entity);
> +
> +       BUG_ON(efqd->active_queue != NULL || sd->active_entity != NULL);
> +       BUG_ON(!efqd->busy_queues);
> +       BUG_ON(sd != entity->sched_data);
> +       BUG_ON(!st);
> +
> +       bfq_update_vtime(st);
> +       bfq_active_extract(st, entity);
> +       sd->active_entity = entity;
> +       entity->service = 0;
> +       elv_log_ioq(efqd, ioq, "set_next_ioq");
> +}
> +
> +/* Get next queue for service. */
> +struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +       struct io_entity *entity = NULL;
> +       struct io_queue *ioq = NULL;
> +       struct io_sched_data *sd;
> +
> +       /*
> +        * one can check for which queue will be selected next while having
> +        * one queue active. preempt logic uses it.
> +        */
> +       BUG_ON(extract && efqd->active_queue != NULL);
> +
> +       if (!efqd->busy_queues)
> +               return NULL;
> +
> +       sd = &efqd->root_group->sched_data;
> +       if (extract)
> +               entity = bfq_lookup_next_entity(sd, 1);
> +       else
> +               entity = bfq_lookup_next_entity(sd, 0);
> +
> +       BUG_ON(!entity);
> +       if (extract)
> +               entity->service = 0;
> +       ioq = io_entity_to_ioq(entity);
> +
> +       return ioq;
> +}
> +
> +/*
> + * coop tells that io scheduler selected a queue for us and we did not
> + * select the next queue based on fairness.
> + */
> +static void __elv_set_active_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
> +                                       int coop)
> +{
> +       struct request_queue *q = efqd->queue;
> +
> +       if (ioq) {
> +               elv_log_ioq(efqd, ioq, "set_active, busy=%d",
> +                                                       efqd->busy_queues);
> +               ioq->slice_end = 0;
> +
> +               elv_clear_ioq_wait_request(ioq);
> +               elv_clear_ioq_must_dispatch(ioq);
> +               elv_mark_ioq_slice_new(ioq);
> +
> +               del_timer(&efqd->idle_slice_timer);
> +       }
> +
> +       efqd->active_queue = ioq;
> +
> +       /* Let iosched know if it wants to take some action */
> +       if (ioq) {
> +               if (q->elevator->ops->elevator_active_ioq_set_fn)
> +                       q->elevator->ops->elevator_active_ioq_set_fn(q,
> +                                                       ioq->sched_queue, coop);
> +       }
> +}
> +
> +/* Get and set a new active queue for service. */
> +struct io_queue *elv_set_active_ioq(struct request_queue *q,
> +                                               struct io_queue *ioq)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +       int coop = 0;
> +
> +       if (!ioq)
> +               ioq = elv_get_next_ioq(q, 1);
> +       else {
> +               elv_set_next_ioq(q, ioq);
> +               /*
> +                * io scheduler selected the next queue for us. Pass this
> +                * this info back to io scheudler. cfq currently uses it
> +                * to reset coop flag on the queue.
> +                */
> +               coop = 1;
> +       }
> +       __elv_set_active_ioq(efqd, ioq, coop);
> +       return ioq;
> +}
> +
> +void elv_reset_active_ioq(struct elv_fq_data *efqd)
> +{
> +       struct request_queue *q = efqd->queue;
> +       struct io_queue *ioq = elv_active_ioq(efqd->queue->elevator);
> +
> +       if (q->elevator->ops->elevator_active_ioq_reset_fn)
> +               q->elevator->ops->elevator_active_ioq_reset_fn(q,
> +                                                       ioq->sched_queue);
> +       efqd->active_queue = NULL;
> +       del_timer(&efqd->idle_slice_timer);
> +}
> +
> +void elv_activate_ioq(struct io_queue *ioq, int add_front)
> +{
> +       bfq_activate_entity(&ioq->entity, add_front);
> +}
> +
> +void elv_deactivate_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
> +                                       int requeue)
> +{
> +       if (ioq == efqd->active_queue)
> +               elv_reset_active_ioq(efqd);
> +
> +       bfq_deactivate_entity(&ioq->entity, requeue);
> +}
> +
> +/* Called when an inactive queue receives a new request. */
> +void elv_add_ioq_busy(struct elv_fq_data *efqd, struct io_queue *ioq)
> +{
> +       BUG_ON(elv_ioq_busy(ioq));
> +       BUG_ON(ioq == efqd->active_queue);
> +       elv_log_ioq(efqd, ioq, "add to busy");
> +       elv_activate_ioq(ioq, 0);
> +       elv_mark_ioq_busy(ioq);
> +       efqd->busy_queues++;
> +       if (elv_ioq_class_rt(ioq))
> +               efqd->busy_rt_queues++;
> +}
> +
> +void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
> +                                       int requeue)
> +{
> +       struct elv_fq_data *efqd = &e->efqd;
> +
> +       BUG_ON(!elv_ioq_busy(ioq));
> +       BUG_ON(ioq->nr_queued);
> +       elv_log_ioq(efqd, ioq, "del from busy");
> +       elv_clear_ioq_busy(ioq);
> +       BUG_ON(efqd->busy_queues == 0);
> +       efqd->busy_queues--;
> +       if (elv_ioq_class_rt(ioq))
> +               efqd->busy_rt_queues--;
> +
> +       elv_deactivate_ioq(efqd, ioq, requeue);
> +}
> +
> +/*
> + * Do the accounting. Determine how much service (in terms of time slices)
> + * current queue used and adjust the start, finish time of queue and vtime
> + * of the tree accordingly.
> + *
> + * Determining the service used in terms of time is tricky in certain
> + * situations. Especially when underlying device supports command queuing
> + * and requests from multiple queues can be there at same time, then it
> + * is not clear which queue consumed how much of disk time.
> + *
> + * To mitigate this problem, cfq starts the time slice of the queue only
> + * after first request from the queue has completed. This does not work
> + * very well if we expire the queue before we wait for first and more
> + * request to finish from the queue. For seeky queues, we will expire the
> + * queue after dispatching few requests without waiting and start dispatching
> + * from next queue.
> + *
> + * Not sure how to determine the time consumed by queue in such scenarios.
> + * Currently as a crude approximation, we are charging 25% of time slice
> + * for such cases. A better mechanism is needed for accurate accounting.
> + */
> +void __elv_ioq_slice_expired(struct request_queue *q, struct io_queue *ioq)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +       struct io_entity *entity = &ioq->entity;
> +       long slice_unused = 0, slice_used = 0, slice_overshoot = 0;
> +
> +       assert_spin_locked(q->queue_lock);
> +       elv_log_ioq(efqd, ioq, "slice expired");
> +
> +       if (elv_ioq_wait_request(ioq))
> +               del_timer(&efqd->idle_slice_timer);
> +
> +       elv_clear_ioq_wait_request(ioq);
> +
> +       /*
> +        * if ioq->slice_end = 0, that means a queue was expired before first
> +        * reuqest from the queue got completed. Of course we are not planning
> +        * to idle on the queue otherwise we would not have expired it.
> +        *
> +        * Charge for the 25% slice in such cases. This is not the best thing
> +        * to do but at the same time not very sure what's the next best
> +        * thing to do.
> +        *
> +        * This arises from that fact that we don't have the notion of
> +        * one queue being operational at one time. io scheduler can dispatch
> +        * requests from multiple queues in one dispatch round. Ideally for
> +        * more accurate accounting of exact disk time used by disk, one
> +        * should dispatch requests from only one queue and wait for all
> +        * the requests to finish. But this will reduce throughput.
> +        */
> +       if (!ioq->slice_end)
> +               slice_used = entity->budget/4;
> +       else {
> +               if (time_after(ioq->slice_end, jiffies)) {
> +                       slice_unused = ioq->slice_end - jiffies;
> +                       if (slice_unused == entity->budget) {
> +                               /*
> +                                * queue got expired immediately after
> +                                * completing first request. Charge 25% of
> +                                * slice.
> +                                */
> +                               slice_used = entity->budget/4;
> +                       } else
> +                               slice_used = entity->budget - slice_unused;
> +               } else {
> +                       slice_overshoot = jiffies - ioq->slice_end;
> +                       slice_used = entity->budget + slice_overshoot;
> +               }
> +       }
> +
> +       elv_log_ioq(efqd, ioq, "sl_end=%lx, jiffies=%lx", ioq->slice_end,
> +                       jiffies);
> +       elv_log_ioq(efqd, ioq, "sl_used=%ld, budget=%ld overshoot=%ld",
> +                               slice_used, entity->budget, slice_overshoot);
> +       elv_ioq_served(ioq, slice_used);
> +
> +       BUG_ON(ioq != efqd->active_queue);
> +       elv_reset_active_ioq(efqd);
> +
> +       if (!ioq->nr_queued)
> +               elv_del_ioq_busy(q->elevator, ioq, 1);
> +       else
> +               elv_activate_ioq(ioq, 0);
> +}
> +EXPORT_SYMBOL(__elv_ioq_slice_expired);
> +
> +/*
> + *  Expire the ioq.
> + */
> +void elv_ioq_slice_expired(struct request_queue *q)
> +{
> +       struct io_queue *ioq = elv_active_ioq(q->elevator);
> +
> +       if (ioq)
> +               __elv_ioq_slice_expired(q, ioq);
> +}
> +
> +/*
> + * Check if new_cfqq should preempt the currently active queue. Return 0 for
> + * no or if we aren't sure, a 1 will cause a preemption attempt.
> + */
> +int elv_should_preempt(struct request_queue *q, struct io_queue *new_ioq,
> +                       struct request *rq)
> +{
> +       struct io_queue *ioq;
> +       struct elevator_queue *eq = q->elevator;
> +
> +       ioq = elv_active_ioq(eq);
> +
> +       if (!ioq)
> +               return 0;
> +
> +       if (elv_ioq_slice_used(ioq))
> +               return 1;
> +
> +       if (elv_ioq_class_idle(new_ioq))
> +               return 0;
> +
> +       if (elv_ioq_class_idle(ioq))
> +               return 1;
> +
> +       /*
> +        * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
> +        */
> +       if (elv_ioq_class_rt(new_ioq) && !elv_ioq_class_rt(ioq))
> +               return 1;
> +
> +       /*
> +        * Check with io scheduler if it has additional criterion based on
> +        * which it wants to preempt existing queue.
> +        */
> +       if (eq->ops->elevator_should_preempt_fn)
> +               return eq->ops->elevator_should_preempt_fn(q, new_ioq, rq);
> +
> +       return 0;
> +}
> +
> +static void elv_preempt_queue(struct request_queue *q, struct io_queue *ioq)
> +{
> +       elv_log_ioq(&q->elevator->efqd, ioq, "preempt");
> +       elv_ioq_slice_expired(q);
> +
> +       /*
> +        * Put the new queue at the front of the of the current list,
> +        * so we know that it will be selected next.
> +        */
> +
> +       elv_activate_ioq(ioq, 1);
> +       elv_ioq_set_slice_end(ioq, 0);
> +       elv_mark_ioq_slice_new(ioq);
> +}
> +
> +void elv_ioq_request_add(struct request_queue *q, struct request *rq)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +       struct io_queue *ioq = rq->ioq;
> +
> +       if (!elv_iosched_fair_queuing_enabled(q->elevator))
> +               return;
> +
> +       BUG_ON(!efqd);
> +       BUG_ON(!ioq);
> +       efqd->rq_queued++;
> +       ioq->nr_queued++;
> +
> +       if (!elv_ioq_busy(ioq))
> +               elv_add_ioq_busy(efqd, ioq);
> +
> +       elv_ioq_update_io_thinktime(ioq);
> +       elv_ioq_update_idle_window(q->elevator, ioq, rq);
> +
> +       if (ioq == elv_active_ioq(q->elevator)) {
> +               /*
> +                * Remember that we saw a request from this process, but
> +                * don't start queuing just yet. Otherwise we risk seeing lots
> +                * of tiny requests, because we disrupt the normal plugging
> +                * and merging. If the request is already larger than a single
> +                * page, let it rip immediately. For that case we assume that
> +                * merging is already done. Ditto for a busy system that
> +                * has other work pending, don't risk delaying until the
> +                * idle timer unplug to continue working.
> +                */
> +               if (elv_ioq_wait_request(ioq)) {
> +                       if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
> +                           efqd->busy_queues > 1) {
> +                               del_timer(&efqd->idle_slice_timer);
> +                               blk_start_queueing(q);
> +                       }
> +                       elv_mark_ioq_must_dispatch(ioq);
> +               }
> +       } else if (elv_should_preempt(q, ioq, rq)) {
> +               /*
> +                * not the active queue - expire current slice if it is
> +                * idle and has expired it's mean thinktime or this new queue
> +                * has some old slice time left and is of higher priority or
> +                * this new queue is RT and the current one is BE
> +                */
> +               elv_preempt_queue(q, ioq);
> +               blk_start_queueing(q);
> +       }
> +}
> +
> +void elv_idle_slice_timer(unsigned long data)
> +{
> +       struct elv_fq_data *efqd = (struct elv_fq_data *)data;
> +       struct io_queue *ioq;
> +       unsigned long flags;
> +       struct request_queue *q = efqd->queue;
> +
> +       elv_log(efqd, "idle timer fired");
> +
> +       spin_lock_irqsave(q->queue_lock, flags);
> +
> +       ioq = efqd->active_queue;
> +
> +       if (ioq) {
> +
> +               /*
> +                * We saw a request before the queue expired, let it through
> +                */
> +               if (elv_ioq_must_dispatch(ioq))
> +                       goto out_kick;
> +
> +               /*
> +                * expired
> +                */
> +               if (elv_ioq_slice_used(ioq))
> +                       goto expire;
> +
> +               /*
> +                * only expire and reinvoke request handler, if there are
> +                * other queues with pending requests
> +                */
> +               if (!elv_nr_busy_ioq(q->elevator))
> +                       goto out_cont;
> +
> +               /*
> +                * not expired and it has a request pending, let it dispatch
> +                */
> +               if (ioq->nr_queued)
> +                       goto out_kick;
> +       }
> +expire:
> +       elv_ioq_slice_expired(q);
> +out_kick:
> +       elv_schedule_dispatch(q);
> +out_cont:
> +       spin_unlock_irqrestore(q->queue_lock, flags);
> +}
> +
> +void elv_ioq_arm_slice_timer(struct request_queue *q)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +       struct io_queue *ioq = elv_active_ioq(q->elevator);
> +       unsigned long sl;
> +
> +       BUG_ON(!ioq);
> +
> +       /*
> +        * SSD device without seek penalty, disable idling. But only do so
> +        * for devices that support queuing, otherwise we still have a problem
> +        * with sync vs async workloads.
> +        */
> +       if (blk_queue_nonrot(q) && efqd->hw_tag)
> +               return;
> +
> +       /*
> +        * still requests with the driver, don't idle
> +        */
> +       if (efqd->rq_in_driver)
> +               return;
> +
> +       /*
> +        * idle is disabled, either manually or by past process history
> +        */
> +       if (!efqd->elv_slice_idle || !elv_ioq_idle_window(ioq))
> +               return;
> +
> +       /*
> +        * may be iosched got its own idling logic. In that case io
> +        * schduler will take care of arming the timer, if need be.
> +        */
> +       if (q->elevator->ops->elevator_arm_slice_timer_fn) {
> +               q->elevator->ops->elevator_arm_slice_timer_fn(q,
> +                                               ioq->sched_queue);
> +       } else {
> +               elv_mark_ioq_wait_request(ioq);
> +               sl = efqd->elv_slice_idle;
> +               mod_timer(&efqd->idle_slice_timer, jiffies + sl);
> +               elv_log_ioq(efqd, ioq, "arm idle: %lu", sl);
> +       }
> +}
> +
> +void elv_free_idle_ioq_list(struct elevator_queue *e)
> +{
> +       struct io_queue *ioq, *n;
> +       struct elv_fq_data *efqd = &e->efqd;
> +
> +       list_for_each_entry_safe(ioq, n, &efqd->idle_list, queue_list)
> +               elv_deactivate_ioq(efqd, ioq, 0);
> +}
> +
> +/* Common layer function to select the next queue to dispatch from */
> +void *elv_fq_select_ioq(struct request_queue *q, int force)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +       struct io_queue *new_ioq = NULL, *ioq = elv_active_ioq(q->elevator);
> +
> +       if (!elv_nr_busy_ioq(q->elevator))
> +               return NULL;
> +
> +       if (ioq == NULL)
> +               goto new_queue;
> +
> +       /*
> +        * Force dispatch. Continue to dispatch from current queue as long
> +        * as it has requests.
> +        */
> +       if (unlikely(force)) {
> +               if (ioq->nr_queued)
> +                       goto keep_queue;
> +               else
> +                       goto expire;
> +       }
> +
> +       /*
> +        * The active queue has run out of time, expire it and select new.
> +        */
> +       if (elv_ioq_slice_used(ioq) && !elv_ioq_must_dispatch(ioq))
> +               goto expire;
> +
> +       /*
> +        * If we have a RT cfqq waiting, then we pre-empt the current non-rt
> +        * cfqq.
> +        */
> +       if (!elv_ioq_class_rt(ioq) && efqd->busy_rt_queues) {
> +               /*
> +                * We simulate this as cfqq timed out so that it gets to bank
> +                * the remaining of its time slice.
> +                */
> +               elv_log_ioq(efqd, ioq, "preempt");
> +               goto expire;
> +       }
> +
> +       /*
> +        * The active queue has requests and isn't expired, allow it to
> +        * dispatch.
> +        */
> +
> +       if (ioq->nr_queued)
> +               goto keep_queue;
> +
> +       /*
> +        * If another queue has a request waiting within our mean seek
> +        * distance, let it run.  The expire code will check for close
> +        * cooperators and put the close queue at the front of the service
> +        * tree.
> +        */
> +       new_ioq = elv_close_cooperator(q, ioq, 0);
> +       if (new_ioq)
> +               goto expire;
> +
> +       /*
> +        * No requests pending. If the active queue still has requests in
> +        * flight or is idling for a new request, allow either of these
> +        * conditions to happen (or time out) before selecting a new queue.
> +        */
> +
> +       if (timer_pending(&efqd->idle_slice_timer) ||
> +           (elv_ioq_nr_dispatched(ioq) && elv_ioq_idle_window(ioq))) {
> +               ioq = NULL;
> +               goto keep_queue;
> +       }
> +
> +expire:
> +       elv_ioq_slice_expired(q);
> +new_queue:
> +       ioq = elv_set_active_ioq(q, new_ioq);
> +keep_queue:
> +       return ioq;
> +}
> +
> +/* A request got removed from io_queue. Do the accounting */
> +void elv_ioq_request_removed(struct elevator_queue *e, struct request *rq)
> +{
> +       struct io_queue *ioq;
> +       struct elv_fq_data *efqd;
> +
> +       if (!elv_iosched_fair_queuing_enabled(e))
> +               return;
> +
> +       ioq = rq->ioq;
> +       BUG_ON(!ioq);
> +       ioq->nr_queued--;
> +
> +       efqd = ioq->efqd;
> +       BUG_ON(!efqd);
> +       efqd->rq_queued--;
> +
> +       if (elv_ioq_busy(ioq) && (elv_active_ioq(e) != ioq) && !ioq->nr_queued)
> +               elv_del_ioq_busy(e, ioq, 1);
> +}
> +
> +/* A request got dispatched. Do the accounting. */
> +void elv_fq_dispatched_request(struct elevator_queue *e, struct request *rq)
> +{
> +       struct io_queue *ioq = rq->ioq;
> +
> +       if (!elv_iosched_fair_queuing_enabled(e))
> +               return;
> +
> +       BUG_ON(!ioq);
> +       elv_ioq_request_dispatched(ioq);
> +       elv_ioq_request_removed(e, rq);
> +       elv_clear_ioq_must_dispatch(ioq);
> +}
> +
> +void elv_fq_activate_rq(struct request_queue *q, struct request *rq)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +
> +       if (!elv_iosched_fair_queuing_enabled(q->elevator))
> +               return;
> +
> +       efqd->rq_in_driver++;
> +       elv_log_ioq(efqd, rq_ioq(rq), "activate rq, drv=%d",
> +                                               efqd->rq_in_driver);
> +}
> +
> +void elv_fq_deactivate_rq(struct request_queue *q, struct request *rq)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +
> +       if (!elv_iosched_fair_queuing_enabled(q->elevator))
> +               return;
> +
> +       WARN_ON(!efqd->rq_in_driver);
> +       efqd->rq_in_driver--;
> +       elv_log_ioq(efqd, rq_ioq(rq), "deactivate rq, drv=%d",
> +                                               efqd->rq_in_driver);
> +}
> +
> +/*
> + * Update hw_tag based on peak queue depth over 50 samples under
> + * sufficient load.
> + */
> +static void elv_update_hw_tag(struct elv_fq_data *efqd)
> +{
> +       if (efqd->rq_in_driver > efqd->rq_in_driver_peak)
> +               efqd->rq_in_driver_peak = efqd->rq_in_driver;
> +
> +       if (efqd->rq_queued <= ELV_HW_QUEUE_MIN &&
> +           efqd->rq_in_driver <= ELV_HW_QUEUE_MIN)
> +               return;
> +
> +       if (efqd->hw_tag_samples++ < 50)
> +               return;
> +
> +       if (efqd->rq_in_driver_peak >= ELV_HW_QUEUE_MIN)
> +               efqd->hw_tag = 1;
> +       else
> +               efqd->hw_tag = 0;
> +
> +       efqd->hw_tag_samples = 0;
> +       efqd->rq_in_driver_peak = 0;
> +}
> +
> +/*
> + * If ioscheduler has functionality of keeping track of close cooperator, check
> + * with it if it has got a closely co-operating queue.
> + */
> +static inline struct io_queue *elv_close_cooperator(struct request_queue *q,
> +                                       struct io_queue *ioq, int probe)
> +{
> +       struct elevator_queue *e = q->elevator;
> +       struct io_queue *new_ioq = NULL;
> +
> +       /*
> +        * Currently this feature is supported only for flat hierarchy or
> +        * root group queues so that default cfq behavior is not changed.
> +        */
> +       if (!is_root_group_ioq(q, ioq))
> +               return NULL;
> +
> +       if (q->elevator->ops->elevator_close_cooperator_fn)
> +               new_ioq = e->ops->elevator_close_cooperator_fn(q,
> +                                               ioq->sched_queue, probe);
> +
> +       /* Only select co-operating queue if it belongs to root group */
> +       if (new_ioq && !is_root_group_ioq(q, new_ioq))
> +               return NULL;
> +
> +       return new_ioq;
> +}
> +
> +/* A request got completed from io_queue. Do the accounting. */
> +void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
> +{
> +       const int sync = rq_is_sync(rq);
> +       struct io_queue *ioq;
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +
> +       if (!elv_iosched_fair_queuing_enabled(q->elevator))
> +               return;
> +
> +       ioq = rq->ioq;
> +
> +       elv_log_ioq(efqd, ioq, "complete");
> +
> +       elv_update_hw_tag(efqd);
> +
> +       WARN_ON(!efqd->rq_in_driver);
> +       WARN_ON(!ioq->dispatched);
> +       efqd->rq_in_driver--;
> +       ioq->dispatched--;
> +
> +       if (sync)
> +               ioq->last_end_request = jiffies;
> +
> +       /*
> +        * If this is the active queue, check if it needs to be expired,
> +        * or if we want to idle in case it has no pending requests.
> +        */
> +
> +       if (elv_active_ioq(q->elevator) == ioq) {
> +               if (elv_ioq_slice_new(ioq)) {
> +                       elv_ioq_set_prio_slice(q, ioq);
> +                       elv_clear_ioq_slice_new(ioq);
> +               }
> +               /*
> +                * If there are no requests waiting in this queue, and
> +                * there are other queues ready to issue requests, AND
> +                * those other queues are issuing requests within our
> +                * mean seek distance, give them a chance to run instead
> +                * of idling.
> +                */
> +               if (elv_ioq_slice_used(ioq) || elv_ioq_class_idle(ioq))
> +                       elv_ioq_slice_expired(q);
> +               else if (!ioq->nr_queued && !elv_close_cooperator(q, ioq, 1)
> +                        && sync && !rq_noidle(rq))
> +                       elv_ioq_arm_slice_timer(q);
> +       }
> +
> +       if (!efqd->rq_in_driver)
> +               elv_schedule_dispatch(q);
> +}
> +
> +struct io_group *io_lookup_io_group_current(struct request_queue *q)
> +{
> +       struct elv_fq_data *efqd = &q->elevator->efqd;
> +
> +       return efqd->root_group;
> +}
> +EXPORT_SYMBOL(io_lookup_io_group_current);
> +
> +void *io_group_async_queue_prio(struct io_group *iog, int ioprio_class,
> +                                       int ioprio)
> +{
> +       struct io_queue *ioq = NULL;
> +
> +       switch (ioprio_class) {
> +       case IOPRIO_CLASS_RT:
> +               ioq = iog->async_queue[0][ioprio];
> +               break;
> +       case IOPRIO_CLASS_BE:
> +               ioq = iog->async_queue[1][ioprio];
> +               break;
> +       case IOPRIO_CLASS_IDLE:
> +               ioq = iog->async_idle_queue;
> +               break;
> +       default:
> +               BUG();
> +       }
> +
> +       if (ioq)
> +               return ioq->sched_queue;
> +       return NULL;
> +}
> +EXPORT_SYMBOL(io_group_async_queue_prio);
> +
> +void io_group_set_async_queue(struct io_group *iog, int ioprio_class,
> +                                       int ioprio, struct io_queue *ioq)
> +{
> +       switch (ioprio_class) {
> +       case IOPRIO_CLASS_RT:
> +               iog->async_queue[0][ioprio] = ioq;
> +               break;
> +       case IOPRIO_CLASS_BE:
> +               iog->async_queue[1][ioprio] = ioq;
> +               break;
> +       case IOPRIO_CLASS_IDLE:
> +               iog->async_idle_queue = ioq;
> +               break;
> +       default:
> +               BUG();
> +       }
> +
> +       /*
> +        * Take the group reference and pin the queue. Group exit will
> +        * clean it up
> +        */
> +       elv_get_ioq(ioq);
> +}
> +EXPORT_SYMBOL(io_group_set_async_queue);
> +
> +/*
> + * Release all the io group references to its async queues.
> + */
> +void io_put_io_group_queues(struct elevator_queue *e, struct io_group *iog)
> +{
> +       int i, j;
> +
> +       for (i = 0; i < 2; i++)
> +               for (j = 0; j < IOPRIO_BE_NR; j++)
> +                       elv_release_ioq(e, &iog->async_queue[i][j]);
> +
> +       /* Free up async idle queue */
> +       elv_release_ioq(e, &iog->async_idle_queue);
> +}
> +
> +struct io_group *io_alloc_root_group(struct request_queue *q,
> +                                       struct elevator_queue *e, void *key)
> +{
> +       struct io_group *iog;
> +       int i;
> +
> +       iog = kmalloc_node(sizeof(*iog), GFP_KERNEL | __GFP_ZERO, q->node);
> +       if (iog == NULL)
> +               return NULL;
> +
> +       for (i = 0; i < IO_IOPRIO_CLASSES; i++)
> +               iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
> +
> +       return iog;
> +}
> +
> +void io_free_root_group(struct elevator_queue *e)
> +{
> +       struct io_group *iog = e->efqd.root_group;
> +       io_put_io_group_queues(e, iog);
> +       kfree(iog);
> +}
> +
> +static void elv_slab_kill(void)
> +{
> +       /*
> +        * Caller already ensured that pending RCU callbacks are completed,
> +        * so we should have no busy allocations at this point.
> +        */
> +       if (elv_ioq_pool)
> +               kmem_cache_destroy(elv_ioq_pool);
> +}
> +
> +static int __init elv_slab_setup(void)
> +{
> +       elv_ioq_pool = KMEM_CACHE(io_queue, 0);
> +       if (!elv_ioq_pool)
> +               goto fail;
> +
> +       return 0;
> +fail:
> +       elv_slab_kill();
> +       return -ENOMEM;
> +}
> +
> +/* Initialize fair queueing data associated with elevator */
> +int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e)
> +{
> +       struct io_group *iog;
> +       struct elv_fq_data *efqd = &e->efqd;
> +
> +       if (!elv_iosched_fair_queuing_enabled(e))
> +               return 0;
> +
> +       iog = io_alloc_root_group(q, e, efqd);
> +       if (iog == NULL)
> +               return 1;
> +
> +       efqd->root_group = iog;
> +       efqd->queue = q;
> +
> +       init_timer(&efqd->idle_slice_timer);
> +       efqd->idle_slice_timer.function = elv_idle_slice_timer;
> +       efqd->idle_slice_timer.data = (unsigned long) efqd;
> +
> +       INIT_WORK(&efqd->unplug_work, elv_kick_queue);
> +
> +       INIT_LIST_HEAD(&efqd->idle_list);
> +
> +       efqd->elv_slice[0] = elv_slice_async;
> +       efqd->elv_slice[1] = elv_slice_sync;
> +       efqd->elv_slice_idle = elv_slice_idle;
> +       efqd->hw_tag = 1;
> +
> +       return 0;
> +}
> +
> +/*
> + * elv_exit_fq_data is called before we call elevator_exit_fn. Before
> + * we ask elevator to cleanup its queues, we do the cleanup here so
> + * that all the group and idle tree references to ioq are dropped. Later
> + * during elevator cleanup, ioc reference will be dropped which will lead
> + * to removal of ioscheduler queue as well as associated ioq object.
> + */
> +void elv_exit_fq_data(struct elevator_queue *e)
> +{
> +       struct elv_fq_data *efqd = &e->efqd;
> +       struct request_queue *q = efqd->queue;
> +
> +       if (!elv_iosched_fair_queuing_enabled(e))
> +               return;
> +
> +       elv_shutdown_timer_wq(e);
> +
> +       spin_lock_irq(q->queue_lock);
> +       /* This should drop all the idle tree references of ioq */
> +       elv_free_idle_ioq_list(e);
> +       spin_unlock_irq(q->queue_lock);
> +
> +       elv_shutdown_timer_wq(e);
> +
> +       BUG_ON(timer_pending(&efqd->idle_slice_timer));
> +       io_free_root_group(e);
> +}
> +
> +/*
> + * This is called after the io scheduler has cleaned up its data structres.
> + * I don't think that this function is required. Right now just keeping it
> + * because cfq cleans up timer and work queue again after freeing up
> + * io contexts. To me io scheduler has already been drained out, and all
> + * the active queue have already been expired so time and work queue should
> + * not been activated during cleanup process.
> + *
> + * Keeping it here for the time being. Will get rid of it later.
> + */
> +void elv_exit_fq_data_post(struct elevator_queue *e)
> +{
> +       struct elv_fq_data *efqd = &e->efqd;
> +
> +       if (!elv_iosched_fair_queuing_enabled(e))
> +               return;
> +
> +       elv_shutdown_timer_wq(e);
> +       BUG_ON(timer_pending(&efqd->idle_slice_timer));
> +}
> +
> +
> +static int __init elv_fq_init(void)
> +{
> +       if (elv_slab_setup())
> +               return -ENOMEM;
> +
> +       /* could be 0 on HZ < 1000 setups */
> +
> +       if (!elv_slice_async)
> +               elv_slice_async = 1;
> +
> +       if (!elv_slice_idle)
> +               elv_slice_idle = 1;
> +
> +       return 0;
> +}
> +
> +module_init(elv_fq_init);
> diff --git a/block/elevator-fq.h b/block/elevator-fq.h
> new file mode 100644
> index 0000000..3bea279
> --- /dev/null
> +++ b/block/elevator-fq.h
> @@ -0,0 +1,488 @@
> +/*
> + * BFQ: data structures and common functions prototypes.
> + *
> + * Based on ideas and code from CFQ:
> + * Copyright (C) 2003 Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>
> + *
> + * Copyright (C) 2008 Fabio Checconi <fabio-f9ZlEuEWxVeACYmtYXMKmw@public.gmane.org>
> + *                   Paolo Valente <paolo.valente@unimore.it>
> + */
> +
> +#include <linux/blkdev.h>
> +
> +#ifndef _BFQ_SCHED_H
> +#define _BFQ_SCHED_H
> +
> +#define IO_IOPRIO_CLASSES      3
> +
> +typedef u64 bfq_timestamp_t;
> +typedef unsigned long bfq_weight_t;
> +typedef unsigned long bfq_service_t;
> +struct io_entity;
> +struct io_queue;
> +
> +#ifdef CONFIG_ELV_FAIR_QUEUING
> +
> +/**
> + * struct bfq_service_tree - per ioprio_class service tree.
> + * @active: tree for active entities (i.e., those backlogged).
> + * @idle: tree for idle entities (i.e., those not backlogged, with V <= F_i).
> + * @first_idle: idle entity with minimum F_i.
> + * @last_idle: idle entity with maximum F_i.
> + * @vtime: scheduler virtual time.
> + * @wsum: scheduler weight sum; active and idle entities contribute to it.
> + *
> + * Each service tree represents a B-WF2Q+ scheduler on its own.  Each
> + * ioprio_class has its own independent scheduler, and so its own
> + * bfq_service_tree.  All the fields are protected by the queue lock
> + * of the containing efqd.
> + */
> +struct io_service_tree {
> +       struct rb_root active;
> +       struct rb_root idle;
> +
> +       struct io_entity *first_idle;
> +       struct io_entity *last_idle;
> +
> +       bfq_timestamp_t vtime;
> +       bfq_weight_t wsum;
> +};
> +
> +/**
> + * struct bfq_sched_data - multi-class scheduler.
> + * @active_entity: entity under service.
> + * @next_active: head-of-the-line entity in the scheduler.
> + * @service_tree: array of service trees, one per ioprio_class.
> + *
> + * bfq_sched_data is the basic scheduler queue.  It supports three
> + * ioprio_classes, and can be used either as a toplevel queue or as
> + * an intermediate queue on a hierarchical setup.
> + * @next_active points to the active entity of the sched_data service
> + * trees that will be scheduled next.
> + *
> + * The supported ioprio_classes are the same as in CFQ, in descending
> + * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
> + * Requests from higher priority queues are served before all the
> + * requests from lower priority queues; among requests of the same
> + * queue requests are served according to B-WF2Q+.
> + * All the fields are protected by the queue lock of the containing bfqd.
> + */
> +struct io_sched_data {
> +       struct io_entity *active_entity;
> +       struct io_service_tree service_tree[IO_IOPRIO_CLASSES];
> +};
> +
> +/**
> + * struct bfq_entity - schedulable entity.
> + * @rb_node: service_tree member.
> + * @on_st: flag, true if the entity is on a tree (either the active or
> + *         the idle one of its service_tree).
> + * @finish: B-WF2Q+ finish timestamp (aka F_i).
> + * @start: B-WF2Q+ start timestamp (aka S_i).
> + * @tree: tree the entity is enqueued into; %NULL if not on a tree.
> + * @min_start: minimum start time of the (active) subtree rooted at
> + *             this entity; used for O(log N) lookups into active trees.
> + * @service: service received during the last round of service.
> + * @budget: budget used to calculate F_i; F_i = S_i + @budget / @weight.
> + * @weight: weight of the queue, calculated as IOPRIO_BE_NR - @ioprio.
> + * @parent: parent entity, for hierarchical scheduling.
> + * @my_sched_data: for non-leaf nodes in the cgroup hierarchy, the
> + *                 associated scheduler queue, %NULL on leaf nodes.
> + * @sched_data: the scheduler queue this entity belongs to.
> + * @ioprio: the ioprio in use.
> + * @new_ioprio: when an ioprio change is requested, the new ioprio value
> + * @ioprio_class: the ioprio_class in use.
> + * @new_ioprio_class: when an ioprio_class change is requested, the new
> + *                    ioprio_class value.
> + * @ioprio_changed: flag, true when the user requested an ioprio or
> + *                  ioprio_class change.
> + *
> + * A bfq_entity is used to represent either a bfq_queue (leaf node in the
> + * cgroup hierarchy) or a bfq_group into the upper level scheduler.  Each
> + * entity belongs to the sched_data of the parent group in the cgroup
> + * hierarchy.  Non-leaf entities have also their own sched_data, stored
> + * in @my_sched_data.
> + *
> + * Each entity stores independently its priority values; this would allow
> + * different weights on different devices, but this functionality is not
> + * exported to userspace by now.  Priorities are updated lazily, first
> + * storing the new values into the new_* fields, then setting the
> + * @ioprio_changed flag.  As soon as there is a transition in the entity
> + * state that allows the priority update to take place the effective and
> + * the requested priority values are synchronized.
> + *
> + * The weight value is calculated from the ioprio to export the same
> + * interface as CFQ.  When dealing with ``well-behaved'' queues (i.e.,
> + * queues that do not spend too much time to consume their budget and
> + * have true sequential behavior, and when there are no external factors
> + * breaking anticipation) the relative weights at each level of the
> + * cgroups hierarchy should be guaranteed.
> + * All the fields are protected by the queue lock of the containing bfqd.
> + */
> +struct io_entity {
> +       struct rb_node rb_node;
> +
> +       int on_st;
> +
> +       bfq_timestamp_t finish;
> +       bfq_timestamp_t start;
> +
> +       struct rb_root *tree;
> +
> +       bfq_timestamp_t min_start;
> +
> +       bfq_service_t service, budget;
> +       bfq_weight_t weight;
> +
> +       struct io_entity *parent;
> +
> +       struct io_sched_data *my_sched_data;
> +       struct io_sched_data *sched_data;
> +
> +       unsigned short ioprio, new_ioprio;
> +       unsigned short ioprio_class, new_ioprio_class;
> +
> +       int ioprio_changed;
> +};
> +
> +/*
> + * A common structure embedded by every io scheduler into their respective
> + * queue structure.
> + */
> +struct io_queue {
> +       struct io_entity entity;
> +       atomic_t ref;
> +       unsigned int flags;
> +
> +       /* Pointer to generic elevator data structure */
> +       struct elv_fq_data *efqd;
> +       struct list_head queue_list;
> +       pid_t pid;
> +
> +       /* Number of requests queued on this io queue */
> +       unsigned long nr_queued;
> +
> +       /* Requests dispatched from this queue */
> +       int dispatched;
> +
> +       /* Keep a track of think time of processes in this queue */
> +       unsigned long last_end_request;
> +       unsigned long ttime_total;
> +       unsigned long ttime_samples;
> +       unsigned long ttime_mean;
> +
> +       unsigned long slice_end;
> +
> +       /* Pointer to io scheduler's queue */
> +       void *sched_queue;
> +};
> +
> +struct io_group {
> +       struct io_sched_data sched_data;
> +
> +       /* async_queue and idle_queue are used only for cfq */
> +       struct io_queue *async_queue[2][IOPRIO_BE_NR];
> +       struct io_queue *async_idle_queue;
> +};
> +
> +struct elv_fq_data {
> +       struct io_group *root_group;
> +
> +       /* List of io queues on idle tree. */
> +       struct list_head idle_list;
> +
> +       struct request_queue *queue;
> +       unsigned int busy_queues;
> +       /*
> +        * Used to track any pending rt requests so we can pre-empt current
> +        * non-RT cfqq in service when this value is non-zero.
> +        */
> +       unsigned int busy_rt_queues;
> +
> +       /* Number of requests queued */
> +       int rq_queued;
> +
> +       /* Pointer to the ioscheduler queue being served */
> +       void *active_queue;
> +
> +       int rq_in_driver;
> +       int hw_tag;
> +       int hw_tag_samples;
> +       int rq_in_driver_peak;
> +
> +       /*
> +        * elevator fair queuing layer has the capability to provide idling
> +        * for ensuring fairness for processes doing dependent reads.
> +        * This might be needed to ensure fairness among two processes doing
> +        * synchronous reads in two different cgroups. noop and deadline don't
> +        * have any notion of anticipation/idling. As of now, these are the
> +        * users of this functionality.
> +        */
> +       unsigned int elv_slice_idle;
> +       struct timer_list idle_slice_timer;
> +       struct work_struct unplug_work;
> +
> +       unsigned int elv_slice[2];
> +};
> +
> +extern int elv_slice_idle;
> +extern int elv_slice_async;
> +
> +/* Logging facilities. */
> +#define elv_log_ioq(efqd, ioq, fmt, args...) \
> +       blk_add_trace_msg((efqd)->queue, "elv%d%c " fmt, (ioq)->pid,    \
> +                               elv_ioq_sync(ioq) ? 'S' : 'A', ##args)
> +
> +#define elv_log(efqd, fmt, args...) \
> +       blk_add_trace_msg((efqd)->queue, "elv " fmt, ##args)
> +
> +#define ioq_sample_valid(samples)   ((samples) > 80)
> +
> +/* Some shared queue flag manipulation functions among elevators */
> +
> +enum elv_queue_state_flags {
> +       ELV_QUEUE_FLAG_busy = 0,          /* has requests or is under service */
> +       ELV_QUEUE_FLAG_sync,              /* synchronous queue */
> +       ELV_QUEUE_FLAG_idle_window,       /* elevator slice idling enabled */
> +       ELV_QUEUE_FLAG_wait_request,      /* waiting for a request */
> +       ELV_QUEUE_FLAG_must_dispatch,     /* must be allowed a dispatch */
> +       ELV_QUEUE_FLAG_slice_new,         /* no requests dispatched in slice */
> +       ELV_QUEUE_FLAG_NR,
> +};
> +
> +#define ELV_IO_QUEUE_FLAG_FNS(name)                                    \
> +static inline void elv_mark_ioq_##name(struct io_queue *ioq)           \
> +{                                                                       \
> +       (ioq)->flags |= (1 << ELV_QUEUE_FLAG_##name);                   \
> +}                                                                       \
> +static inline void elv_clear_ioq_##name(struct io_queue *ioq)          \
> +{                                                                       \
> +       (ioq)->flags &= ~(1 << ELV_QUEUE_FLAG_##name);                  \
> +}                                                                       \
> +static inline int elv_ioq_##name(struct io_queue *ioq)                         \
> +{                                                                       \
> +       return ((ioq)->flags & (1 << ELV_QUEUE_FLAG_##name)) != 0;      \
> +}
> +
> +ELV_IO_QUEUE_FLAG_FNS(busy)
> +ELV_IO_QUEUE_FLAG_FNS(sync)
> +ELV_IO_QUEUE_FLAG_FNS(wait_request)
> +ELV_IO_QUEUE_FLAG_FNS(must_dispatch)
> +ELV_IO_QUEUE_FLAG_FNS(idle_window)
> +ELV_IO_QUEUE_FLAG_FNS(slice_new)
> +
> +static inline struct io_service_tree *
> +io_entity_service_tree(struct io_entity *entity)
> +{
> +       struct io_sched_data *sched_data = entity->sched_data;
> +       unsigned int idx = entity->ioprio_class - 1;
> +
> +       BUG_ON(idx >= IO_IOPRIO_CLASSES);
> +       BUG_ON(sched_data == NULL);
> +
> +       return sched_data->service_tree + idx;
> +}
> +
> +/* A request got dispatched from the io_queue. Do the accounting. */
> +static inline void elv_ioq_request_dispatched(struct io_queue *ioq)
> +{
> +       ioq->dispatched++;
> +}
> +
> +static inline int elv_ioq_slice_used(struct io_queue *ioq)
> +{
> +       if (elv_ioq_slice_new(ioq))
> +               return 0;
> +       if (time_before(jiffies, ioq->slice_end))
> +               return 0;
> +
> +       return 1;
> +}
> +
> +/* How many request are currently dispatched from the queue */
> +static inline int elv_ioq_nr_dispatched(struct io_queue *ioq)
> +{
> +       return ioq->dispatched;
> +}
> +
> +/* How many request are currently queued in the queue */
> +static inline int elv_ioq_nr_queued(struct io_queue *ioq)
> +{
> +       return ioq->nr_queued;
> +}
> +
> +static inline pid_t elv_ioq_pid(struct io_queue *ioq)
> +{
> +       return ioq->pid;
> +}
> +
> +static inline unsigned long elv_ioq_ttime_mean(struct io_queue *ioq)
> +{
> +       return ioq->ttime_mean;
> +}
> +
> +static inline unsigned long elv_ioq_sample_valid(struct io_queue *ioq)
> +{
> +       return ioq_sample_valid(ioq->ttime_samples);
> +}
> +
> +static inline void elv_get_ioq(struct io_queue *ioq)
> +{
> +       atomic_inc(&ioq->ref);
> +}
> +
> +static inline void elv_ioq_set_slice_end(struct io_queue *ioq,
> +                                               unsigned long slice_end)
> +{
> +       ioq->slice_end = slice_end;
> +}
> +
> +static inline int elv_ioq_class_idle(struct io_queue *ioq)
> +{
> +       return ioq->entity.ioprio_class == IOPRIO_CLASS_IDLE;
> +}
> +
> +static inline int elv_ioq_class_rt(struct io_queue *ioq)
> +{
> +       return ioq->entity.ioprio_class == IOPRIO_CLASS_RT;
> +}
> +
> +static inline int elv_ioq_ioprio_class(struct io_queue *ioq)
> +{
> +       return ioq->entity.new_ioprio_class;
> +}
> +
> +static inline int elv_ioq_ioprio(struct io_queue *ioq)
> +{
> +       return ioq->entity.new_ioprio;
> +}
> +
> +static inline void elv_ioq_set_ioprio_class(struct io_queue *ioq,
> +                                               int ioprio_class)
> +{
> +       ioq->entity.new_ioprio_class = ioprio_class;
> +       ioq->entity.ioprio_changed = 1;
> +}
> +
> +static inline void elv_ioq_set_ioprio(struct io_queue *ioq, int ioprio)
> +{
> +       ioq->entity.new_ioprio = ioprio;
> +       ioq->entity.ioprio_changed = 1;
> +}
> +
> +static inline void *ioq_sched_queue(struct io_queue *ioq)
> +{
> +       if (ioq)
> +               return ioq->sched_queue;
> +       return NULL;
> +}
> +
> +static inline struct io_group *ioq_to_io_group(struct io_queue *ioq)
> +{
> +       return container_of(ioq->entity.sched_data, struct io_group,
> +                                               sched_data);
> +}
> +
> +/* Functions used by blksysfs.c */
> +extern ssize_t elv_slice_idle_show(struct request_queue *q, char *name);
> +extern ssize_t elv_slice_idle_store(struct request_queue *q, const char *name,
> +                                               size_t count);
> +extern ssize_t elv_slice_sync_show(struct request_queue *q, char *name);
> +extern ssize_t elv_slice_sync_store(struct request_queue *q, const char *name,
> +                                               size_t count);
> +extern ssize_t elv_slice_async_show(struct request_queue *q, char *name);
> +extern ssize_t elv_slice_async_store(struct request_queue *q, const char *name,
> +                                               size_t count);
> +
> +/* Functions used by elevator.c */
> +extern int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e);
> +extern void elv_exit_fq_data(struct elevator_queue *e);
> +extern void elv_exit_fq_data_post(struct elevator_queue *e);
> +
> +extern void elv_ioq_request_add(struct request_queue *q, struct request *rq);
> +extern void elv_ioq_request_removed(struct elevator_queue *e,
> +                                       struct request *rq);
> +extern void elv_fq_dispatched_request(struct elevator_queue *e,
> +                                       struct request *rq);
> +
> +extern void elv_fq_activate_rq(struct request_queue *q, struct request *rq);
> +extern void elv_fq_deactivate_rq(struct request_queue *q, struct request *rq);
> +
> +extern void elv_ioq_completed_request(struct request_queue *q,
> +                               struct request *rq);
> +
> +extern void *elv_fq_select_ioq(struct request_queue *q, int force);
> +extern struct io_queue *rq_ioq(struct request *rq);
> +
> +/* Functions used by io schedulers */
> +extern void elv_put_ioq(struct io_queue *ioq);
> +extern void __elv_ioq_slice_expired(struct request_queue *q,
> +                                       struct io_queue *ioq);
> +extern int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq,
> +               void *sched_queue, int ioprio_class, int ioprio, int is_sync);
> +extern void elv_schedule_dispatch(struct request_queue *q);
> +extern int elv_hw_tag(struct elevator_queue *e);
> +extern void *elv_active_sched_queue(struct elevator_queue *e);
> +extern int elv_mod_idle_slice_timer(struct elevator_queue *eq,
> +                                       unsigned long expires);
> +extern int elv_del_idle_slice_timer(struct elevator_queue *eq);
> +extern unsigned int elv_get_slice_idle(struct elevator_queue *eq);
> +extern void *io_group_async_queue_prio(struct io_group *iog, int ioprio_class,
> +                                       int ioprio);
> +extern void io_group_set_async_queue(struct io_group *iog, int ioprio_class,
> +                                       int ioprio, struct io_queue *ioq);
> +extern struct io_group *io_lookup_io_group_current(struct request_queue *q);
> +extern int elv_nr_busy_ioq(struct elevator_queue *e);
> +extern int elv_nr_busy_rt_ioq(struct elevator_queue *e);
> +extern struct io_queue *elv_alloc_ioq(struct request_queue *q, gfp_t gfp_mask);
> +extern void elv_free_ioq(struct io_queue *ioq);
> +
> +#else /* CONFIG_ELV_FAIR_QUEUING */
> +
> +static inline int elv_init_fq_data(struct request_queue *q,
> +                                       struct elevator_queue *e)
> +{
> +       return 0;
> +}
> +
> +static inline void elv_exit_fq_data(struct elevator_queue *e) {}
> +static inline void elv_exit_fq_data_post(struct elevator_queue *e) {}
> +
> +static inline void elv_fq_activate_rq(struct request_queue *q,
> +                                       struct request *rq)
> +{
> +}
> +
> +static inline void elv_fq_deactivate_rq(struct request_queue *q,
> +                                       struct request *rq)
> +{
> +}
> +
> +static inline void elv_fq_dispatched_request(struct elevator_queue *e,
> +                                               struct request *rq)
> +{
> +}
> +
> +static inline void elv_ioq_request_removed(struct elevator_queue *e,
> +                                               struct request *rq)
> +{
> +}
> +
> +static inline void elv_ioq_request_add(struct request_queue *q,
> +                                       struct request *rq)
> +{
> +}
> +
> +static inline void elv_ioq_completed_request(struct request_queue *q,
> +                                               struct request *rq)
> +{
> +}
> +
> +static inline void *ioq_sched_queue(struct io_queue *ioq) { return NULL; }
> +static inline struct io_queue *rq_ioq(struct request *rq) { return NULL; }
> +static inline void *elv_fq_select_ioq(struct request_queue *q, int force)
> +{
> +       return NULL;
> +}
> +#endif /* CONFIG_ELV_FAIR_QUEUING */
> +#endif /* _BFQ_SCHED_H */
> diff --git a/block/elevator.c b/block/elevator.c
> index 7073a90..c2f07f5 100644
> --- a/block/elevator.c
> +++ b/block/elevator.c
> @@ -231,6 +231,9 @@ static struct elevator_queue *elevator_alloc(struct request_queue *q,
>        for (i = 0; i < ELV_HASH_ENTRIES; i++)
>                INIT_HLIST_HEAD(&eq->hash[i]);
>
> +       if (elv_init_fq_data(q, eq))
> +               goto err;
> +
>        return eq;
>  err:
>        kfree(eq);
> @@ -301,9 +304,11 @@ EXPORT_SYMBOL(elevator_init);
>  void elevator_exit(struct elevator_queue *e)
>  {
>        mutex_lock(&e->sysfs_lock);
> +       elv_exit_fq_data(e);
>        if (e->ops->elevator_exit_fn)
>                e->ops->elevator_exit_fn(e);
>        e->ops = NULL;
> +       elv_exit_fq_data_post(e);
>        mutex_unlock(&e->sysfs_lock);
>
>        kobject_put(&e->kobj);
> @@ -314,6 +319,8 @@ static void elv_activate_rq(struct request_queue *q, struct request *rq)
>  {
>        struct elevator_queue *e = q->elevator;
>
> +       elv_fq_activate_rq(q, rq);
> +
>        if (e->ops->elevator_activate_req_fn)
>                e->ops->elevator_activate_req_fn(q, rq);
>  }
> @@ -322,6 +329,8 @@ static void elv_deactivate_rq(struct request_queue *q, struct request *rq)
>  {
>        struct elevator_queue *e = q->elevator;
>
> +       elv_fq_deactivate_rq(q, rq);
> +
>        if (e->ops->elevator_deactivate_req_fn)
>                e->ops->elevator_deactivate_req_fn(q, rq);
>  }
> @@ -446,6 +455,7 @@ void elv_dispatch_sort(struct request_queue *q, struct request *rq)
>        elv_rqhash_del(q, rq);
>
>        q->nr_sorted--;
> +       elv_fq_dispatched_request(q->elevator, rq);
>
>        boundary = q->end_sector;
>        stop_flags = REQ_SOFTBARRIER | REQ_HARDBARRIER | REQ_STARTED;
> @@ -486,6 +496,7 @@ void elv_dispatch_add_tail(struct request_queue *q, struct request *rq)
>        elv_rqhash_del(q, rq);
>
>        q->nr_sorted--;
> +       elv_fq_dispatched_request(q->elevator, rq);
>
>        q->end_sector = rq_end_sector(rq);
>        q->boundary_rq = rq;
> @@ -553,6 +564,7 @@ void elv_merge_requests(struct request_queue *q, struct request *rq,
>        elv_rqhash_del(q, next);
>
>        q->nr_sorted--;
> +       elv_ioq_request_removed(e, next);
>        q->last_merge = rq;
>  }
>
> @@ -657,12 +669,8 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
>                                q->last_merge = rq;
>                }
>
> -               /*
> -                * Some ioscheds (cfq) run q->request_fn directly, so
> -                * rq cannot be accessed after calling
> -                * elevator_add_req_fn.
> -                */
>                q->elevator->ops->elevator_add_req_fn(q, rq);
> +               elv_ioq_request_add(q, rq);
>                break;
>
>        case ELEVATOR_INSERT_REQUEUE:
> @@ -872,13 +880,12 @@ void elv_dequeue_request(struct request_queue *q, struct request *rq)
>
>  int elv_queue_empty(struct request_queue *q)
>  {
> -       struct elevator_queue *e = q->elevator;
> -
>        if (!list_empty(&q->queue_head))
>                return 0;
>
> -       if (e->ops->elevator_queue_empty_fn)
> -               return e->ops->elevator_queue_empty_fn(q);
> +       /* Hopefully nr_sorted works and no need to call queue_empty_fn */
> +       if (q->nr_sorted)
> +               return 0;
>
>        return 1;
>  }
> @@ -953,8 +960,11 @@ void elv_completed_request(struct request_queue *q, struct request *rq)
>         */
>        if (blk_account_rq(rq)) {
>                q->in_flight--;
> -               if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
> -                       e->ops->elevator_completed_req_fn(q, rq);
> +               if (blk_sorted_rq(rq)) {
> +                       if (e->ops->elevator_completed_req_fn)
> +                               e->ops->elevator_completed_req_fn(q, rq);
> +                       elv_ioq_completed_request(q, rq);
> +               }
>        }
>
>        /*
> @@ -1242,3 +1252,17 @@ struct request *elv_rb_latter_request(struct request_queue *q,
>        return NULL;
>  }
>  EXPORT_SYMBOL(elv_rb_latter_request);
> +
> +/* Get the io scheduler queue pointer. For cfq, it is stored in rq->ioq*/
> +void *elv_get_sched_queue(struct request_queue *q, struct request *rq)
> +{
> +       return ioq_sched_queue(rq_ioq(rq));
> +}
> +EXPORT_SYMBOL(elv_get_sched_queue);
> +
> +/* Select an ioscheduler queue to dispatch request from. */
> +void *elv_select_sched_queue(struct request_queue *q, int force)
> +{
> +       return ioq_sched_queue(elv_fq_select_ioq(q, force));
> +}
> +EXPORT_SYMBOL(elv_select_sched_queue);
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index b4f71f1..96a94c9 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -245,6 +245,11 @@ struct request {
>
>        /* for bidi */
>        struct request *next_rq;
> +
> +#ifdef CONFIG_ELV_FAIR_QUEUING
> +       /* io queue request belongs to */
> +       struct io_queue *ioq;
> +#endif
>  };
>
>  static inline unsigned short req_get_ioprio(struct request *req)
> diff --git a/include/linux/elevator.h b/include/linux/elevator.h
> index c59b769..679c149 100644
> --- a/include/linux/elevator.h
> +++ b/include/linux/elevator.h
> @@ -2,6 +2,7 @@
>  #define _LINUX_ELEVATOR_H
>
>  #include <linux/percpu.h>
> +#include "../../block/elevator-fq.h"
>
>  #ifdef CONFIG_BLOCK
>
> @@ -29,6 +30,18 @@ typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct reques
>
>  typedef void *(elevator_init_fn) (struct request_queue *);
>  typedef void (elevator_exit_fn) (struct elevator_queue *);
> +#ifdef CONFIG_ELV_FAIR_QUEUING
> +typedef void (elevator_free_sched_queue_fn) (struct elevator_queue*, void *);
> +typedef void (elevator_active_ioq_set_fn) (struct request_queue*, void *, int);
> +typedef void (elevator_active_ioq_reset_fn) (struct request_queue *, void*);
> +typedef void (elevator_arm_slice_timer_fn) (struct request_queue*, void*);
> +typedef int (elevator_should_preempt_fn) (struct request_queue*, void*,
> +                                               struct request*);
> +typedef int (elevator_update_idle_window_fn) (struct elevator_queue*, void*,
> +                                               struct request*);
> +typedef struct io_queue* (elevator_close_cooperator_fn) (struct request_queue*,
> +                                               void*, int probe);
> +#endif
>
>  struct elevator_ops
>  {
> @@ -56,6 +69,17 @@ struct elevator_ops
>        elevator_init_fn *elevator_init_fn;
>        elevator_exit_fn *elevator_exit_fn;
>        void (*trim)(struct io_context *);
> +
> +#ifdef CONFIG_ELV_FAIR_QUEUING
> +       elevator_free_sched_queue_fn *elevator_free_sched_queue_fn;
> +       elevator_active_ioq_set_fn *elevator_active_ioq_set_fn;
> +       elevator_active_ioq_reset_fn *elevator_active_ioq_reset_fn;
> +
> +       elevator_arm_slice_timer_fn *elevator_arm_slice_timer_fn;
> +       elevator_should_preempt_fn *elevator_should_preempt_fn;
> +       elevator_update_idle_window_fn *elevator_update_idle_window_fn;
> +       elevator_close_cooperator_fn *elevator_close_cooperator_fn;
> +#endif
>  };
>
>  #define ELV_NAME_MAX   (16)
> @@ -76,6 +100,9 @@ struct elevator_type
>        struct elv_fs_entry *elevator_attrs;
>        char elevator_name[ELV_NAME_MAX];
>        struct module *elevator_owner;
> +#ifdef CONFIG_ELV_FAIR_QUEUING
> +       int elevator_features;
> +#endif
>  };
>
>  /*
> @@ -89,6 +116,10 @@ struct elevator_queue
>        struct elevator_type *elevator_type;
>        struct mutex sysfs_lock;
>        struct hlist_head *hash;
> +#ifdef CONFIG_ELV_FAIR_QUEUING
> +       /* fair queuing data */
> +       struct elv_fq_data efqd;
> +#endif
>  };
>
>  /*
> @@ -209,5 +240,25 @@ enum {
>        __val;                                                  \
>  })
>
> +/* iosched can let elevator know their feature set/capability */
> +#ifdef CONFIG_ELV_FAIR_QUEUING
> +
> +/* iosched wants to use fq logic of elevator layer */
> +#define        ELV_IOSCHED_NEED_FQ     1
> +
> +static inline int elv_iosched_fair_queuing_enabled(struct elevator_queue *e)
> +{
> +       return (e->elevator_type->elevator_features) & ELV_IOSCHED_NEED_FQ;
> +}
> +
> +#else /* ELV_IOSCHED_FAIR_QUEUING */
> +
> +static inline int elv_iosched_fair_queuing_enabled(struct elevator_queue *e)
> +{
> +       return 0;
> +}
> +#endif /* ELV_IOSCHED_FAIR_QUEUING */
> +extern void *elv_get_sched_queue(struct request_queue *q, struct request *rq);
> +extern void *elv_select_sched_queue(struct request_queue *q, int force);
>  #endif /* CONFIG_BLOCK */
>  #endif
> --
> 1.6.0.1
>
>

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Gui Jianfeng]

Vivek Goyal wrote:
...
> +
> +/* Get next queue for service. */
> +struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
> +{
> +	struct elv_fq_data *efqd = &q->elevator->efqd;
> +	struct io_entity *entity = NULL;
> +	struct io_queue *ioq = NULL;
> +	struct io_sched_data *sd;
> +
> +	/*
> +	 * one can check for which queue will be selected next while having
> +	 * one queue active. preempt logic uses it.
> +	 */
> +	BUG_ON(extract && efqd->active_queue != NULL);
> +
> +	if (!efqd->busy_queues)
> +		return NULL;
> +
> +	sd = &efqd->root_group->sched_data;
> +	if (extract)
> +		entity = bfq_lookup_next_entity(sd, 1);
> +	else
> +		entity = bfq_lookup_next_entity(sd, 0);

This if and else branch is not needed.

Signed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
---
 block/elevator-fq.c |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 3c5f9da..655162b 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -3069,10 +3069,7 @@ struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
 
 	sd = &efqd->root_group->sched_data;
 	for (; sd != NULL; sd = entity->my_sched_data) {
-		if (extract)
-			entity = bfq_lookup_next_entity(sd, 1);
-		else
-			entity = bfq_lookup_next_entity(sd, 0);
+		entity = bfq_lookup_next_entity(sd, extract);
 
 		/*
 		 * entity can be null despite the fact that there are busy
-- 
1.5.4.rc3

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Gui Jianfeng]

Vivek Goyal wrote:
...
> +
> +static inline pid_t elv_ioq_pid(struct io_queue *ioq)
> +{
> +	return ioq->pid;
> +}
> +
> +static inline unsigned long elv_ioq_ttime_mean(struct io_queue *ioq)
> +{
> +	return ioq->ttime_mean;
> +}
> +
> +static inline unsigned long elv_ioq_sample_valid(struct io_queue *ioq)
> +{
> +	return ioq_sample_valid(ioq->ttime_samples);
> +}
> +

These three functions are dead now, just remove them.

Signed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
---
 block/elevator-fq.h |   15 ---------------
 1 files changed, 0 insertions(+), 15 deletions(-)

diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 24a3af9..b2bb11a 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -452,21 +452,6 @@ static inline int elv_ioq_nr_queued(struct io_queue *ioq)
 	return ioq->nr_queued;
 }
 
-static inline pid_t elv_ioq_pid(struct io_queue *ioq)
-{
-	return ioq->pid;
-}
-
-static inline unsigned long elv_ioq_ttime_mean(struct io_queue *ioq)
-{
-	return ioq->ttime_mean;
-}
-
-static inline unsigned long elv_ioq_sample_valid(struct io_queue *ioq)
-{
-	return ioq_sample_valid(ioq->ttime_samples);
-}
-
 static inline void elv_get_ioq(struct io_queue *ioq)
 {
 	atomic_inc(&ioq->ref);
-- 
1.5.4.rc3

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Vivek Goyal]

On Mon, Jun 08, 2009 at 03:44:31PM +0800, Gui Jianfeng wrote:
> Vivek Goyal wrote:
> ...
> > +
> > +static inline pid_t elv_ioq_pid(struct io_queue *ioq)
> > +{
> > +	return ioq->pid;
> > +}
> > +
> > +static inline unsigned long elv_ioq_ttime_mean(struct io_queue *ioq)
> > +{
> > +	return ioq->ttime_mean;
> > +}
> > +
> > +static inline unsigned long elv_ioq_sample_valid(struct io_queue *ioq)
> > +{
> > +	return ioq_sample_valid(ioq->ttime_samples);
> > +}
> > +
> 
> These three functions are dead now, just remove them.
> 

Thanks Gui. queued up for next posting.

Thanks
Vivek

> Signed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  block/elevator-fq.h |   15 ---------------
>  1 files changed, 0 insertions(+), 15 deletions(-)
> 
> diff --git a/block/elevator-fq.h b/block/elevator-fq.h
> index 24a3af9..b2bb11a 100644
> --- a/block/elevator-fq.h
> +++ b/block/elevator-fq.h
> @@ -452,21 +452,6 @@ static inline int elv_ioq_nr_queued(struct io_queue *ioq)
>  	return ioq->nr_queued;
>  }
>  
> -static inline pid_t elv_ioq_pid(struct io_queue *ioq)
> -{
> -	return ioq->pid;
> -}
> -
> -static inline unsigned long elv_ioq_ttime_mean(struct io_queue *ioq)
> -{
> -	return ioq->ttime_mean;
> -}
> -
> -static inline unsigned long elv_ioq_sample_valid(struct io_queue *ioq)
> -{
> -	return ioq_sample_valid(ioq->ttime_samples);
> -}
> -
>  static inline void elv_get_ioq(struct io_queue *ioq)
>  {
>  	atomic_inc(&ioq->ref);
> -- 
> 1.5.4.rc3

Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

[Vivek Goyal]

On Mon, Jun 08, 2009 at 09:08:44AM +0800, Gui Jianfeng wrote:
> Vivek Goyal wrote:
> ...
> > +
> > +/* Get next queue for service. */
> > +struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
> > +{
> > +	struct elv_fq_data *efqd = &q->elevator->efqd;
> > +	struct io_entity *entity = NULL;
> > +	struct io_queue *ioq = NULL;
> > +	struct io_sched_data *sd;
> > +
> > +	/*
> > +	 * one can check for which queue will be selected next while having
> > +	 * one queue active. preempt logic uses it.
> > +	 */
> > +	BUG_ON(extract && efqd->active_queue != NULL);
> > +
> > +	if (!efqd->busy_queues)
> > +		return NULL;
> > +
> > +	sd = &efqd->root_group->sched_data;
> > +	if (extract)
> > +		entity = bfq_lookup_next_entity(sd, 1);
> > +	else
> > +		entity = bfq_lookup_next_entity(sd, 0);
> 
> This if and else branch is not needed.
> 
> Signed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  block/elevator-fq.c |    5 +----
>  1 files changed, 1 insertions(+), 4 deletions(-)
> 
> diff --git a/block/elevator-fq.c b/block/elevator-fq.c
> index 3c5f9da..655162b 100644
> --- a/block/elevator-fq.c
> +++ b/block/elevator-fq.c
> @@ -3069,10 +3069,7 @@ struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
>  
>  	sd = &efqd->root_group->sched_data;
>  	for (; sd != NULL; sd = entity->my_sched_data) {
> -		if (extract)
> -			entity = bfq_lookup_next_entity(sd, 1);
> -		else
> -			entity = bfq_lookup_next_entity(sd, 0);
> +		entity = bfq_lookup_next_entity(sd, extract);
>  
>  		/*
>  		 * entity can be null despite the fact that there are busy

Thanks Gui. Queued for next posting.

Thanks
Vivek

[PATCH 03/20] io-controller: Charge for time slice based on average disk rate

[Vivek Goyal]

o There are situations where a queue gets expired very soon and it looks
  as if time slice used by that queue is zero. For example, If an async
  queue dispatches a bunch of requests and queue is expired before first
  request completes. Another example is where a queue is expired as soon
  as first request completes and queue has no more requests (sync queues
  on SSD).

o Currently we just charge 25% of slice length in such cases. This patch tries
  to improve on that approximation by keeping a track of average disk rate
  and charging for time by nr_sectors/disk_rate.

o This is still experimental, not very sure if it gives measurable improvement
  or not.

Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/elevator-fq.c |   85 +++++++++++++++++++++++++++++++++++++++++++++++++-
 block/elevator-fq.h |   11 ++++++
 2 files changed, 94 insertions(+), 2 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index c5cc080..73b997a 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -19,6 +19,9 @@ const int elv_slice_async_rq = 2;
 int elv_slice_idle = HZ / 125;
 static struct kmem_cache *elv_ioq_pool;
 
+/* Maximum Window length for updating average disk rate */
+static int elv_rate_sampling_window = HZ / 10;
+
 #define ELV_SLICE_SCALE		(5)
 #define ELV_HW_QUEUE_MIN	(5)
 #define IO_SERVICE_TREE_INIT   ((struct io_service_tree)		\
@@ -1022,6 +1025,47 @@ static void elv_ioq_update_io_thinktime(struct io_queue *ioq)
 	ioq->ttime_mean = (ioq->ttime_total + 128) / ioq->ttime_samples;
 }
 
+static void elv_update_io_rate(struct elv_fq_data *efqd, struct request *rq)
+{
+	long elapsed = jiffies - efqd->rate_sampling_start;
+	unsigned long total;
+
+	/* sampling window is off */
+	if (!efqd->rate_sampling_start)
+		return;
+
+	efqd->rate_sectors_current += rq->nr_sectors;
+
+	if (efqd->rq_in_driver && (elapsed < elv_rate_sampling_window))
+		return;
+
+	efqd->rate_sectors = (7*efqd->rate_sectors +
+				256*efqd->rate_sectors_current) / 8;
+
+	if (!elapsed) {
+		/*
+		 * updating rate before a jiffy could complete. Could be a
+		 * problem with fast queuing/non-queuing hardware. Should we
+		 * look at higher resolution time source?
+		 *
+		 * In case of non-queuing hardware we will probably not try to
+		 * dispatch from multiple queues and will be able to account
+		 * for disk time used and will not need this approximation
+		 * anyway?
+		 */
+		elapsed = 1;
+	}
+
+	efqd->rate_time = (7*efqd->rate_time + 256*elapsed) / 8;
+	total = efqd->rate_sectors + (efqd->rate_time/2);
+	efqd->mean_rate = total/efqd->rate_time;
+
+	elv_log(efqd, "mean_rate=%d, t=%d s=%d", efqd->mean_rate,
+			elapsed, efqd->rate_sectors_current);
+	efqd->rate_sampling_start = 0;
+	efqd->rate_sectors_current = 0;
+}
+
 /*
  * Disable idle window if the process thinks too long.
  * This idle flag can also be updated by io scheduler.
@@ -1312,6 +1356,34 @@ void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
 }
 
 /*
+ * Calculate the effective disk time used by the queue based on how many
+ * sectors queue has dispatched and what is the average disk rate
+ * Returns disk time in ms.
+ */
+static inline unsigned long elv_disk_time_used(struct request_queue *q,
+					struct io_queue *ioq)
+{
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+	struct io_entity *entity = &ioq->entity;
+	unsigned long jiffies_used = 0;
+
+	if (!efqd->mean_rate)
+		return entity->budget/4;
+
+	/* Charge the queue based on average disk rate */
+	jiffies_used = ioq->nr_sectors/efqd->mean_rate;
+
+	if (!jiffies_used)
+		jiffies_used = 1;
+
+	elv_log_ioq(efqd, ioq, "disk time=%ldms sect=%ld rate=%ld",
+				jiffies_to_msecs(jiffies_used),
+				ioq->nr_sectors, efqd->mean_rate);
+
+	return jiffies_used;
+}
+
+/*
  * Do the accounting. Determine how much service (in terms of time slices)
  * current queue used and adjust the start, finish time of queue and vtime
  * of the tree accordingly.
@@ -1363,7 +1435,7 @@ void __elv_ioq_slice_expired(struct request_queue *q, struct io_queue *ioq)
 	 * the requests to finish. But this will reduce throughput.
 	 */
 	if (!ioq->slice_end)
-		slice_used = entity->budget/4;
+		slice_used = elv_disk_time_used(q, ioq);
 	else {
 		if (time_after(ioq->slice_end, jiffies)) {
 			slice_unused = ioq->slice_end - jiffies;
@@ -1373,7 +1445,7 @@ void __elv_ioq_slice_expired(struct request_queue *q, struct io_queue *ioq)
 				 * completing first request. Charge 25% of
 				 * slice.
 				 */
-				slice_used = entity->budget/4;
+				slice_used = elv_disk_time_used(q, ioq);
 			} else
 				slice_used = entity->budget - slice_unused;
 		} else {
@@ -1391,6 +1463,8 @@ void __elv_ioq_slice_expired(struct request_queue *q, struct io_queue *ioq)
 	BUG_ON(ioq != efqd->active_queue);
 	elv_reset_active_ioq(efqd);
 
+	/* Queue is being expired. Reset number of secotrs dispatched */
+	ioq->nr_sectors = 0;
 	if (!ioq->nr_queued)
 		elv_del_ioq_busy(q->elevator, ioq, 1);
 	else
@@ -1725,6 +1799,7 @@ void elv_fq_dispatched_request(struct elevator_queue *e, struct request *rq)
 
 	BUG_ON(!ioq);
 	elv_ioq_request_dispatched(ioq);
+	ioq->nr_sectors += rq->nr_sectors;
 	elv_ioq_request_removed(e, rq);
 	elv_clear_ioq_must_dispatch(ioq);
 }
@@ -1737,6 +1812,10 @@ void elv_fq_activate_rq(struct request_queue *q, struct request *rq)
 		return;
 
 	efqd->rq_in_driver++;
+
+	if (!efqd->rate_sampling_start)
+		efqd->rate_sampling_start = jiffies;
+
 	elv_log_ioq(efqd, rq_ioq(rq), "activate rq, drv=%d",
 						efqd->rq_in_driver);
 }
@@ -1828,6 +1907,8 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
 	efqd->rq_in_driver--;
 	ioq->dispatched--;
 
+	elv_update_io_rate(efqd, rq);
+
 	if (sync)
 		ioq->last_end_request = jiffies;
 
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 3bea279..ce2d671 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -165,6 +165,9 @@ struct io_queue {
 	/* Requests dispatched from this queue */
 	int dispatched;
 
+	/* Number of sectors dispatched in current dispatch round */
+	int nr_sectors;
+
 	/* Keep a track of think time of processes in this queue */
 	unsigned long last_end_request;
 	unsigned long ttime_total;
@@ -223,6 +226,14 @@ struct elv_fq_data {
 	struct work_struct unplug_work;
 
 	unsigned int elv_slice[2];
+
+	/* Fields for keeping track of average disk rate */
+	unsigned long rate_sectors; /* number of sectors finished */
+	unsigned long rate_time;   /* jiffies elapsed */
+	unsigned long mean_rate; /* sectors per jiffy */
+	unsigned long long rate_sampling_start; /*sampling window start jifies*/
+	/* number of sectors finished io during current sampling window */
+	unsigned long rate_sectors_current;
 };
 
 extern int elv_slice_idle;
-- 
1.6.0.1

[PATCH 04/20] io-controller: Modify cfq to make use of flat elevator fair queuing

[Vivek Goyal]

This patch changes cfq to use fair queuing code from elevator layer.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Fabio Checconi <fabio-f9ZlEuEWxVeACYmtYXMKmw@public.gmane.org>
Signed-off-by: Paolo Valente <paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org>
Signed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/Kconfig.iosched     |    3 +-
 block/cfq-iosched.c       | 1097 +++++++++------------------------------------
 include/linux/iocontext.h |    4 -
 3 files changed, 219 insertions(+), 885 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 3398134..dd5224d 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -3,7 +3,7 @@ if BLOCK
 menu "IO Schedulers"
 
 config ELV_FAIR_QUEUING
-	bool "Elevator Fair Queuing Support"
+	bool
 	default n
 	---help---
 	  Traditionally only cfq had notion of multiple queues and it did
@@ -46,6 +46,7 @@ config IOSCHED_DEADLINE
 
 config IOSCHED_CFQ
 	tristate "CFQ I/O scheduler"
+	select ELV_FAIR_QUEUING
 	default y
 	---help---
 	  The CFQ I/O scheduler tries to distribute bandwidth equally
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index a55a9bd..f90c534 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -12,7 +12,6 @@
 #include <linux/rbtree.h>
 #include <linux/ioprio.h>
 #include <linux/blktrace_api.h>
-
 /*
  * tunables
  */
@@ -23,15 +22,7 @@ static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
 static const int cfq_back_max = 16 * 1024;
 /* penalty of a backwards seek */
 static const int cfq_back_penalty = 2;
-static const int cfq_slice_sync = HZ / 10;
-static int cfq_slice_async = HZ / 25;
 static const int cfq_slice_async_rq = 2;
-static int cfq_slice_idle = HZ / 125;
-
-/*
- * offset from end of service tree
- */
-#define CFQ_IDLE_DELAY		(HZ / 5)
 
 /*
  * below this threshold, we consider thinktime immediate
@@ -43,7 +34,7 @@ static int cfq_slice_idle = HZ / 125;
 
 #define RQ_CIC(rq)		\
 	((struct cfq_io_context *) (rq)->elevator_private)
-#define RQ_CFQQ(rq)		(struct cfq_queue *) ((rq)->elevator_private2)
+#define RQ_CFQQ(rq)	(struct cfq_queue *) (ioq_sched_queue((rq)->ioq))
 
 static struct kmem_cache *cfq_pool;
 static struct kmem_cache *cfq_ioc_pool;
@@ -53,8 +44,6 @@ static struct completion *ioc_gone;
 static DEFINE_SPINLOCK(ioc_gone_lock);
 
 #define CFQ_PRIO_LISTS		IOPRIO_BE_NR
-#define cfq_class_idle(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
-#define cfq_class_rt(cfqq)	((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
 
 #define sample_valid(samples)	((samples) > 80)
 
@@ -75,12 +64,6 @@ struct cfq_rb_root {
  */
 struct cfq_data {
 	struct request_queue *queue;
-
-	/*
-	 * rr list of queues with requests and the count of them
-	 */
-	struct cfq_rb_root service_tree;
-
 	/*
 	 * Each priority tree is sorted by next_request position.  These
 	 * trees are used when determining if two or more queues are
@@ -88,39 +71,10 @@ struct cfq_data {
 	 */
 	struct rb_root prio_trees[CFQ_PRIO_LISTS];
 
-	unsigned int busy_queues;
-	/*
-	 * Used to track any pending rt requests so we can pre-empt current
-	 * non-RT cfqq in service when this value is non-zero.
-	 */
-	unsigned int busy_rt_queues;
-
-	int rq_in_driver;
 	int sync_flight;
 
-	/*
-	 * queue-depth detection
-	 */
-	int rq_queued;
-	int hw_tag;
-	int hw_tag_samples;
-	int rq_in_driver_peak;
-
-	/*
-	 * idle window management
-	 */
-	struct timer_list idle_slice_timer;
-	struct work_struct unplug_work;
-
-	struct cfq_queue *active_queue;
 	struct cfq_io_context *active_cic;
 
-	/*
-	 * async queue for each priority case
-	 */
-	struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
-	struct cfq_queue *async_idle_cfqq;
-
 	sector_t last_position;
 	unsigned long last_end_request;
 
@@ -131,9 +85,7 @@ struct cfq_data {
 	unsigned int cfq_fifo_expire[2];
 	unsigned int cfq_back_penalty;
 	unsigned int cfq_back_max;
-	unsigned int cfq_slice[2];
 	unsigned int cfq_slice_async_rq;
-	unsigned int cfq_slice_idle;
 
 	struct list_head cic_list;
 };
@@ -142,16 +94,11 @@ struct cfq_data {
  * Per process-grouping structure
  */
 struct cfq_queue {
-	/* reference count */
-	atomic_t ref;
+	struct io_queue *ioq;
 	/* various state flags, see below */
 	unsigned int flags;
 	/* parent cfq_data */
 	struct cfq_data *cfqd;
-	/* service_tree member */
-	struct rb_node rb_node;
-	/* service_tree key */
-	unsigned long rb_key;
 	/* prio tree member */
 	struct rb_node p_node;
 	/* prio tree root we belong to, if any */
@@ -167,33 +114,23 @@ struct cfq_queue {
 	/* fifo list of requests in sort_list */
 	struct list_head fifo;
 
-	unsigned long slice_end;
-	long slice_resid;
 	unsigned int slice_dispatch;
 
 	/* pending metadata requests */
 	int meta_pending;
-	/* number of requests that are on the dispatch list or inside driver */
-	int dispatched;
 
 	/* io prio of this group */
-	unsigned short ioprio, org_ioprio;
-	unsigned short ioprio_class, org_ioprio_class;
+	unsigned short org_ioprio;
+	unsigned short org_ioprio_class;
 
 	pid_t pid;
 };
 
 enum cfqq_state_flags {
-	CFQ_CFQQ_FLAG_on_rr = 0,	/* on round-robin busy list */
-	CFQ_CFQQ_FLAG_wait_request,	/* waiting for a request */
-	CFQ_CFQQ_FLAG_must_dispatch,	/* must be allowed a dispatch */
 	CFQ_CFQQ_FLAG_must_alloc,	/* must be allowed rq alloc */
 	CFQ_CFQQ_FLAG_must_alloc_slice,	/* per-slice must_alloc flag */
 	CFQ_CFQQ_FLAG_fifo_expire,	/* FIFO checked in this slice */
-	CFQ_CFQQ_FLAG_idle_window,	/* slice idling enabled */
 	CFQ_CFQQ_FLAG_prio_changed,	/* task priority has changed */
-	CFQ_CFQQ_FLAG_slice_new,	/* no requests dispatched in slice */
-	CFQ_CFQQ_FLAG_sync,		/* synchronous queue */
 	CFQ_CFQQ_FLAG_coop,		/* has done a coop jump of the queue */
 };
 
@@ -211,16 +148,10 @@ static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq)		\
 	return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0;	\
 }
 
-CFQ_CFQQ_FNS(on_rr);
-CFQ_CFQQ_FNS(wait_request);
-CFQ_CFQQ_FNS(must_dispatch);
 CFQ_CFQQ_FNS(must_alloc);
 CFQ_CFQQ_FNS(must_alloc_slice);
 CFQ_CFQQ_FNS(fifo_expire);
-CFQ_CFQQ_FNS(idle_window);
 CFQ_CFQQ_FNS(prio_changed);
-CFQ_CFQQ_FNS(slice_new);
-CFQ_CFQQ_FNS(sync);
 CFQ_CFQQ_FNS(coop);
 #undef CFQ_CFQQ_FNS
 
@@ -259,66 +190,32 @@ static inline int cfq_bio_sync(struct bio *bio)
 	return 0;
 }
 
-/*
- * scheduler run of queue, if there are requests pending and no one in the
- * driver that will restart queueing
- */
-static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
+static inline struct io_group *cfqq_to_io_group(struct cfq_queue *cfqq)
 {
-	if (cfqd->busy_queues) {
-		cfq_log(cfqd, "schedule dispatch");
-		kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
-	}
+	return ioq_to_io_group(cfqq->ioq);
 }
 
-static int cfq_queue_empty(struct request_queue *q)
+static inline int cfq_class_idle(struct cfq_queue *cfqq)
 {
-	struct cfq_data *cfqd = q->elevator->elevator_data;
-
-	return !cfqd->busy_queues;
+	return elv_ioq_class_idle(cfqq->ioq);
 }
 
-/*
- * Scale schedule slice based on io priority. Use the sync time slice only
- * if a queue is marked sync and has sync io queued. A sync queue with async
- * io only, should not get full sync slice length.
- */
-static inline int cfq_prio_slice(struct cfq_data *cfqd, int sync,
-				 unsigned short prio)
-{
-	const int base_slice = cfqd->cfq_slice[sync];
-
-	WARN_ON(prio >= IOPRIO_BE_NR);
-
-	return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
-}
-
-static inline int
-cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+static inline int cfq_class_rt(struct cfq_queue *cfqq)
 {
-	return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
+	return elv_ioq_class_rt(cfqq->ioq);
 }
 
-static inline void
-cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+static inline int cfq_cfqq_sync(struct cfq_queue *cfqq)
 {
-	cfqq->slice_end = cfq_prio_to_slice(cfqd, cfqq) + jiffies;
-	cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
+	return elv_ioq_sync(cfqq->ioq);
 }
 
-/*
- * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
- * isn't valid until the first request from the dispatch is activated
- * and the slice time set.
- */
-static inline int cfq_slice_used(struct cfq_queue *cfqq)
+static inline int cfqq_is_active_queue(struct cfq_queue *cfqq)
 {
-	if (cfq_cfqq_slice_new(cfqq))
-		return 0;
-	if (time_before(jiffies, cfqq->slice_end))
-		return 0;
+	struct cfq_data *cfqd = cfqq->cfqd;
+	struct elevator_queue *e = cfqd->queue->elevator;
 
-	return 1;
+	return (elv_active_sched_queue(e) == cfqq);
 }
 
 /*
@@ -417,33 +314,6 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2)
 }
 
 /*
- * The below is leftmost cache rbtree addon
- */
-static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
-{
-	if (!root->left)
-		root->left = rb_first(&root->rb);
-
-	if (root->left)
-		return rb_entry(root->left, struct cfq_queue, rb_node);
-
-	return NULL;
-}
-
-static void rb_erase_init(struct rb_node *n, struct rb_root *root)
-{
-	rb_erase(n, root);
-	RB_CLEAR_NODE(n);
-}
-
-static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
-{
-	if (root->left == n)
-		root->left = NULL;
-	rb_erase_init(n, &root->rb);
-}
-
-/*
  * would be nice to take fifo expire time into account as well
  */
 static struct request *
@@ -456,10 +326,10 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 
 	BUG_ON(RB_EMPTY_NODE(&last->rb_node));
 
-	if (rbprev)
+	if (rbprev != NULL)
 		prev = rb_entry_rq(rbprev);
 
-	if (rbnext)
+	if (rbnext != NULL)
 		next = rb_entry_rq(rbnext);
 	else {
 		rbnext = rb_first(&cfqq->sort_list);
@@ -470,95 +340,6 @@ cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 	return cfq_choose_req(cfqd, next, prev);
 }
 
-static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
-				      struct cfq_queue *cfqq)
-{
-	/*
-	 * just an approximation, should be ok.
-	 */
-	return (cfqd->busy_queues - 1) * (cfq_prio_slice(cfqd, 1, 0) -
-		       cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
-}
-
-/*
- * The cfqd->service_tree holds all pending cfq_queue's that have
- * requests waiting to be processed. It is sorted in the order that
- * we will service the queues.
- */
-static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
-				 int add_front)
-{
-	struct rb_node **p, *parent;
-	struct cfq_queue *__cfqq;
-	unsigned long rb_key;
-	int left;
-
-	if (cfq_class_idle(cfqq)) {
-		rb_key = CFQ_IDLE_DELAY;
-		parent = rb_last(&cfqd->service_tree.rb);
-		if (parent && parent != &cfqq->rb_node) {
-			__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
-			rb_key += __cfqq->rb_key;
-		} else
-			rb_key += jiffies;
-	} else if (!add_front) {
-		rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
-		rb_key += cfqq->slice_resid;
-		cfqq->slice_resid = 0;
-	} else
-		rb_key = 0;
-
-	if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
-		/*
-		 * same position, nothing more to do
-		 */
-		if (rb_key == cfqq->rb_key)
-			return;
-
-		cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
-	}
-
-	left = 1;
-	parent = NULL;
-	p = &cfqd->service_tree.rb.rb_node;
-	while (*p) {
-		struct rb_node **n;
-
-		parent = *p;
-		__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
-
-		/*
-		 * sort RT queues first, we always want to give
-		 * preference to them. IDLE queues goes to the back.
-		 * after that, sort on the next service time.
-		 */
-		if (cfq_class_rt(cfqq) > cfq_class_rt(__cfqq))
-			n = &(*p)->rb_left;
-		else if (cfq_class_rt(cfqq) < cfq_class_rt(__cfqq))
-			n = &(*p)->rb_right;
-		else if (cfq_class_idle(cfqq) < cfq_class_idle(__cfqq))
-			n = &(*p)->rb_left;
-		else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
-			n = &(*p)->rb_right;
-		else if (rb_key < __cfqq->rb_key)
-			n = &(*p)->rb_left;
-		else
-			n = &(*p)->rb_right;
-
-		if (n == &(*p)->rb_right)
-			left = 0;
-
-		p = n;
-	}
-
-	if (left)
-		cfqd->service_tree.left = &cfqq->rb_node;
-
-	cfqq->rb_key = rb_key;
-	rb_link_node(&cfqq->rb_node, parent, p);
-	rb_insert_color(&cfqq->rb_node, &cfqd->service_tree.rb);
-}
-
 static struct cfq_queue *
 cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
 		     sector_t sector, struct rb_node **ret_parent,
@@ -620,57 +401,34 @@ static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 		cfqq->p_root = NULL;
 }
 
-/*
- * Update cfqq's position in the service tree.
- */
-static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+/* An active ioq is being reset. A chance to do cic related stuff. */
+static void cfq_active_ioq_reset(struct request_queue *q, void *sched_queue)
 {
-	/*
-	 * Resorting requires the cfqq to be on the RR list already.
-	 */
-	if (cfq_cfqq_on_rr(cfqq)) {
-		cfq_service_tree_add(cfqd, cfqq, 0);
-		cfq_prio_tree_add(cfqd, cfqq);
-	}
-}
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_queue *cfqq = sched_queue;
 
-/*
- * add to busy list of queues for service, trying to be fair in ordering
- * the pending list according to last request service
- */
-static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
-{
-	cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
-	BUG_ON(cfq_cfqq_on_rr(cfqq));
-	cfq_mark_cfqq_on_rr(cfqq);
-	cfqd->busy_queues++;
-	if (cfq_class_rt(cfqq))
-		cfqd->busy_rt_queues++;
+	if (cfqd->active_cic) {
+		put_io_context(cfqd->active_cic->ioc);
+		cfqd->active_cic = NULL;
+	}
 
-	cfq_resort_rr_list(cfqd, cfqq);
+	/* Resort the cfqq in prio tree */
+	if (cfqq)
+		cfq_prio_tree_add(cfqd, cfqq);
 }
 
-/*
- * Called when the cfqq no longer has requests pending, remove it from
- * the service tree.
- */
-static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+/* An ioq has been set as active one. */
+static void cfq_active_ioq_set(struct request_queue *q, void *sched_queue,
+				int coop)
 {
-	cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
-	BUG_ON(!cfq_cfqq_on_rr(cfqq));
-	cfq_clear_cfqq_on_rr(cfqq);
+	struct cfq_queue *cfqq = sched_queue;
 
-	if (!RB_EMPTY_NODE(&cfqq->rb_node))
-		cfq_rb_erase(&cfqq->rb_node, &cfqd->service_tree);
-	if (cfqq->p_root) {
-		rb_erase(&cfqq->p_node, cfqq->p_root);
-		cfqq->p_root = NULL;
-	}
+	cfqq->slice_dispatch = 0;
 
-	BUG_ON(!cfqd->busy_queues);
-	cfqd->busy_queues--;
-	if (cfq_class_rt(cfqq))
-		cfqd->busy_rt_queues--;
+	cfq_clear_cfqq_must_alloc_slice(cfqq);
+	cfq_clear_cfqq_fifo_expire(cfqq);
+	if (!coop)
+		cfq_clear_cfqq_coop(cfqq);
 }
 
 /*
@@ -679,7 +437,6 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 static void cfq_del_rq_rb(struct request *rq)
 {
 	struct cfq_queue *cfqq = RQ_CFQQ(rq);
-	struct cfq_data *cfqd = cfqq->cfqd;
 	const int sync = rq_is_sync(rq);
 
 	BUG_ON(!cfqq->queued[sync]);
@@ -687,8 +444,17 @@ static void cfq_del_rq_rb(struct request *rq)
 
 	elv_rb_del(&cfqq->sort_list, rq);
 
-	if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
-		cfq_del_cfqq_rr(cfqd, cfqq);
+	/*
+	 * If this was last request in the queue, remove this queue from
+	 * prio trees. For last request nr_queued count will still be 1 as
+	 * elevator fair queuing layer is yet to do the accounting.
+	 */
+	if (elv_ioq_nr_queued(cfqq->ioq) == 1) {
+		if (cfqq->p_root) {
+			rb_erase(&cfqq->p_node, cfqq->p_root);
+			cfqq->p_root = NULL;
+		}
+	}
 }
 
 static void cfq_add_rq_rb(struct request *rq)
@@ -706,9 +472,6 @@ static void cfq_add_rq_rb(struct request *rq)
 	while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
 		cfq_dispatch_insert(cfqd->queue, __alias);
 
-	if (!cfq_cfqq_on_rr(cfqq))
-		cfq_add_cfqq_rr(cfqd, cfqq);
-
 	/*
 	 * check if this request is a better next-serve candidate
 	 */
@@ -756,23 +519,9 @@ static void cfq_activate_request(struct request_queue *q, struct request *rq)
 {
 	struct cfq_data *cfqd = q->elevator->elevator_data;
 
-	cfqd->rq_in_driver++;
-	cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
-						cfqd->rq_in_driver);
-
 	cfqd->last_position = rq->hard_sector + rq->hard_nr_sectors;
 }
 
-static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
-{
-	struct cfq_data *cfqd = q->elevator->elevator_data;
-
-	WARN_ON(!cfqd->rq_in_driver);
-	cfqd->rq_in_driver--;
-	cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
-						cfqd->rq_in_driver);
-}
-
 static void cfq_remove_request(struct request *rq)
 {
 	struct cfq_queue *cfqq = RQ_CFQQ(rq);
@@ -783,7 +532,6 @@ static void cfq_remove_request(struct request *rq)
 	list_del_init(&rq->queuelist);
 	cfq_del_rq_rb(rq);
 
-	cfqq->cfqd->rq_queued--;
 	if (rq_is_meta(rq)) {
 		WARN_ON(!cfqq->meta_pending);
 		cfqq->meta_pending--;
@@ -857,93 +605,21 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
 	return 0;
 }
 
-static void __cfq_set_active_queue(struct cfq_data *cfqd,
-				   struct cfq_queue *cfqq)
-{
-	if (cfqq) {
-		cfq_log_cfqq(cfqd, cfqq, "set_active");
-		cfqq->slice_end = 0;
-		cfqq->slice_dispatch = 0;
-
-		cfq_clear_cfqq_wait_request(cfqq);
-		cfq_clear_cfqq_must_dispatch(cfqq);
-		cfq_clear_cfqq_must_alloc_slice(cfqq);
-		cfq_clear_cfqq_fifo_expire(cfqq);
-		cfq_mark_cfqq_slice_new(cfqq);
-
-		del_timer(&cfqd->idle_slice_timer);
-	}
-
-	cfqd->active_queue = cfqq;
-}
-
 /*
  * current cfqq expired its slice (or was too idle), select new one
  */
 static void
-__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
-		    int timed_out)
+__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
-	cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
-
-	if (cfq_cfqq_wait_request(cfqq))
-		del_timer(&cfqd->idle_slice_timer);
-
-	cfq_clear_cfqq_wait_request(cfqq);
-
-	/*
-	 * store what was left of this slice, if the queue idled/timed out
-	 */
-	if (timed_out && !cfq_cfqq_slice_new(cfqq)) {
-		cfqq->slice_resid = cfqq->slice_end - jiffies;
-		cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
-	}
-
-	cfq_resort_rr_list(cfqd, cfqq);
-
-	if (cfqq == cfqd->active_queue)
-		cfqd->active_queue = NULL;
-
-	if (cfqd->active_cic) {
-		put_io_context(cfqd->active_cic->ioc);
-		cfqd->active_cic = NULL;
-	}
+	__elv_ioq_slice_expired(cfqd->queue, cfqq->ioq);
 }
 
-static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out)
+static inline void cfq_slice_expired(struct cfq_data *cfqd)
 {
-	struct cfq_queue *cfqq = cfqd->active_queue;
+	struct cfq_queue *cfqq = elv_active_sched_queue(cfqd->queue->elevator);
 
 	if (cfqq)
-		__cfq_slice_expired(cfqd, cfqq, timed_out);
-}
-
-/*
- * Get next queue for service. Unless we have a queue preemption,
- * we'll simply select the first cfqq in the service tree.
- */
-static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
-{
-	if (RB_EMPTY_ROOT(&cfqd->service_tree.rb))
-		return NULL;
-
-	return cfq_rb_first(&cfqd->service_tree);
-}
-
-/*
- * Get and set a new active queue for service.
- */
-static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
-					      struct cfq_queue *cfqq)
-{
-	if (!cfqq) {
-		cfqq = cfq_get_next_queue(cfqd);
-		if (cfqq)
-			cfq_clear_cfqq_coop(cfqq);
-	}
-
-	__cfq_set_active_queue(cfqd, cfqq);
-	return cfqq;
+		__cfq_slice_expired(cfqd, cfqq);
 }
 
 static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
@@ -1020,11 +696,12 @@ static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
  * associated with the I/O issued by cur_cfqq.  I'm not sure this is a valid
  * assumption.
  */
-static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
-					      struct cfq_queue *cur_cfqq,
+static struct io_queue *cfq_close_cooperator(struct request_queue *q,
+					      void *cur_sched_queue,
 					      int probe)
 {
-	struct cfq_queue *cfqq;
+	struct cfq_queue *cur_cfqq = cur_sched_queue, *cfqq;
+	struct cfq_data *cfqd = q->elevator->elevator_data;
 
 	/*
 	 * A valid cfq_io_context is necessary to compare requests against
@@ -1047,38 +724,18 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
 
 	if (!probe)
 		cfq_mark_cfqq_coop(cfqq);
-	return cfqq;
+	return cfqq->ioq;
 }
 
-static void cfq_arm_slice_timer(struct cfq_data *cfqd)
+static void cfq_arm_slice_timer(struct request_queue *q, void *sched_queue)
 {
-	struct cfq_queue *cfqq = cfqd->active_queue;
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_queue *cfqq = sched_queue;
 	struct cfq_io_context *cic;
 	unsigned long sl;
 
-	/*
-	 * SSD device without seek penalty, disable idling. But only do so
-	 * for devices that support queuing, otherwise we still have a problem
-	 * with sync vs async workloads.
-	 */
-	if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
-		return;
-
 	WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
-	WARN_ON(cfq_cfqq_slice_new(cfqq));
-
-	/*
-	 * idle is disabled, either manually or by past process history
-	 */
-	if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
-		return;
-
-	/*
-	 * still requests with the driver, don't idle
-	 */
-	if (cfqd->rq_in_driver)
-		return;
-
+	WARN_ON(elv_ioq_slice_new(cfqq->ioq));
 	/*
 	 * task has exited, don't wait
 	 */
@@ -1086,18 +743,18 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 	if (!cic || !atomic_read(&cic->ioc->nr_tasks))
 		return;
 
-	cfq_mark_cfqq_wait_request(cfqq);
 
+	elv_mark_ioq_wait_request(cfqq->ioq);
 	/*
 	 * we don't want to idle for seeks, but we do want to allow
 	 * fair distribution of slice time for a process doing back-to-back
 	 * seeks. so allow a little bit of time for him to submit a new rq
 	 */
-	sl = cfqd->cfq_slice_idle;
+	sl = elv_get_slice_idle(q->elevator);
 	if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
 		sl = min(sl, msecs_to_jiffies(CFQ_MIN_TT));
 
-	mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
+	elv_mod_idle_slice_timer(q->elevator, jiffies + sl);
 	cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu", sl);
 }
 
@@ -1106,13 +763,12 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
  */
 static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
 {
-	struct cfq_data *cfqd = q->elevator->elevator_data;
 	struct cfq_queue *cfqq = RQ_CFQQ(rq);
+	struct cfq_data *cfqd = q->elevator->elevator_data;
 
-	cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
+	cfq_log_cfqq(cfqd, cfqq, "dispatch_insert sect=%d", rq->nr_sectors);
 
 	cfq_remove_request(rq);
-	cfqq->dispatched++;
 	elv_dispatch_sort(q, rq);
 
 	if (cfq_cfqq_sync(cfqq))
@@ -1150,78 +806,11 @@ static inline int
 cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
 	const int base_rq = cfqd->cfq_slice_async_rq;
+	unsigned short ioprio = elv_ioq_ioprio(cfqq->ioq);
 
-	WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
-
-	return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
-}
-
-/*
- * Select a queue for service. If we have a current active queue,
- * check whether to continue servicing it, or retrieve and set a new one.
- */
-static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
-{
-	struct cfq_queue *cfqq, *new_cfqq = NULL;
-
-	cfqq = cfqd->active_queue;
-	if (!cfqq)
-		goto new_queue;
-
-	/*
-	 * The active queue has run out of time, expire it and select new.
-	 */
-	if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq))
-		goto expire;
-
-	/*
-	 * If we have a RT cfqq waiting, then we pre-empt the current non-rt
-	 * cfqq.
-	 */
-	if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) {
-		/*
-		 * We simulate this as cfqq timed out so that it gets to bank
-		 * the remaining of its time slice.
-		 */
-		cfq_log_cfqq(cfqd, cfqq, "preempt");
-		cfq_slice_expired(cfqd, 1);
-		goto new_queue;
-	}
-
-	/*
-	 * The active queue has requests and isn't expired, allow it to
-	 * dispatch.
-	 */
-	if (!RB_EMPTY_ROOT(&cfqq->sort_list))
-		goto keep_queue;
-
-	/*
-	 * If another queue has a request waiting within our mean seek
-	 * distance, let it run.  The expire code will check for close
-	 * cooperators and put the close queue at the front of the service
-	 * tree.
-	 */
-	new_cfqq = cfq_close_cooperator(cfqd, cfqq, 0);
-	if (new_cfqq)
-		goto expire;
+	WARN_ON(ioprio >= IOPRIO_BE_NR);
 
-	/*
-	 * No requests pending. If the active queue still has requests in
-	 * flight or is idling for a new request, allow either of these
-	 * conditions to happen (or time out) before selecting a new queue.
-	 */
-	if (timer_pending(&cfqd->idle_slice_timer) ||
-	    (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
-		cfqq = NULL;
-		goto keep_queue;
-	}
-
-expire:
-	cfq_slice_expired(cfqd, 0);
-new_queue:
-	cfqq = cfq_set_active_queue(cfqd, new_cfqq);
-keep_queue:
-	return cfqq;
+	return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - ioprio));
 }
 
 static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
@@ -1246,12 +835,14 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd)
 	struct cfq_queue *cfqq;
 	int dispatched = 0;
 
-	while ((cfqq = cfq_rb_first(&cfqd->service_tree)) != NULL)
+	while ((cfqq = elv_select_sched_queue(cfqd->queue, 1)) != NULL)
 		dispatched += __cfq_forced_dispatch_cfqq(cfqq);
 
-	cfq_slice_expired(cfqd, 0);
+	/* This probably is redundant now. above loop will should make sure
+	 * that all the busy queues have expired */
+	cfq_slice_expired(cfqd);
 
-	BUG_ON(cfqd->busy_queues);
+	BUG_ON(elv_nr_busy_ioq(cfqd->queue->elevator));
 
 	cfq_log(cfqd, "forced_dispatch=%d\n", dispatched);
 	return dispatched;
@@ -1297,13 +888,10 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
 	struct cfq_queue *cfqq;
 	unsigned int max_dispatch;
 
-	if (!cfqd->busy_queues)
-		return 0;
-
 	if (unlikely(force))
 		return cfq_forced_dispatch(cfqd);
 
-	cfqq = cfq_select_queue(cfqd);
+	cfqq = elv_select_sched_queue(q, 0);
 	if (!cfqq)
 		return 0;
 
@@ -1320,7 +908,7 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
 	/*
 	 * Does this cfqq already have too much IO in flight?
 	 */
-	if (cfqq->dispatched >= max_dispatch) {
+	if (elv_ioq_nr_dispatched(cfqq->ioq) >= max_dispatch) {
 		/*
 		 * idle queue must always only have a single IO in flight
 		 */
@@ -1330,13 +918,13 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
 		/*
 		 * We have other queues, don't allow more IO from this one
 		 */
-		if (cfqd->busy_queues > 1)
+		if (elv_nr_busy_ioq(q->elevator) > 1)
 			return 0;
 
 		/*
 		 * we are the only queue, allow up to 4 times of 'quantum'
 		 */
-		if (cfqq->dispatched >= 4 * max_dispatch)
+		if (elv_ioq_nr_dispatched(cfqq->ioq) >= 4 * max_dispatch)
 			return 0;
 	}
 
@@ -1345,51 +933,45 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
 	 */
 	cfq_dispatch_request(cfqd, cfqq);
 	cfqq->slice_dispatch++;
-	cfq_clear_cfqq_must_dispatch(cfqq);
 
 	/*
 	 * expire an async queue immediately if it has used up its slice. idle
 	 * queue always expire after 1 dispatch round.
 	 */
-	if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
+	if (elv_nr_busy_ioq(q->elevator) > 1 && ((!cfq_cfqq_sync(cfqq) &&
 	    cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
 	    cfq_class_idle(cfqq))) {
-		cfqq->slice_end = jiffies + 1;
-		cfq_slice_expired(cfqd, 0);
+		cfq_slice_expired(cfqd);
 	}
 
 	cfq_log(cfqd, "dispatched a request");
 	return 1;
 }
 
-/*
- * task holds one reference to the queue, dropped when task exits. each rq
- * in-flight on this queue also holds a reference, dropped when rq is freed.
- *
- * queue lock must be held here.
- */
-static void cfq_put_queue(struct cfq_queue *cfqq)
+static void cfq_free_cfq_queue(struct elevator_queue *e, void *sched_queue)
 {
+	struct cfq_queue *cfqq = sched_queue;
 	struct cfq_data *cfqd = cfqq->cfqd;
 
-	BUG_ON(atomic_read(&cfqq->ref) <= 0);
+	BUG_ON(!cfqq);
 
-	if (!atomic_dec_and_test(&cfqq->ref))
-		return;
-
-	cfq_log_cfqq(cfqd, cfqq, "put_queue");
+	cfq_log_cfqq(cfqd, cfqq, "free_queue");
 	BUG_ON(rb_first(&cfqq->sort_list));
 	BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
-	BUG_ON(cfq_cfqq_on_rr(cfqq));
 
-	if (unlikely(cfqd->active_queue == cfqq)) {
-		__cfq_slice_expired(cfqd, cfqq, 0);
-		cfq_schedule_dispatch(cfqd);
+	if (unlikely(cfqq_is_active_queue(cfqq))) {
+		__cfq_slice_expired(cfqd, cfqq);
+		elv_schedule_dispatch(cfqd->queue);
 	}
 
 	kmem_cache_free(cfq_pool, cfqq);
 }
 
+static inline void cfq_put_queue(struct cfq_queue *cfqq)
+{
+	elv_put_ioq(cfqq->ioq);
+}
+
 /*
  * Must always be called with the rcu_read_lock() held
  */
@@ -1477,9 +1059,9 @@ static void cfq_free_io_context(struct io_context *ioc)
 
 static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
-	if (unlikely(cfqq == cfqd->active_queue)) {
-		__cfq_slice_expired(cfqd, cfqq, 0);
-		cfq_schedule_dispatch(cfqd);
+	if (unlikely(cfqq == elv_active_sched_queue(cfqd->queue->elevator))) {
+		__cfq_slice_expired(cfqd, cfqq);
+		elv_schedule_dispatch(cfqd->queue);
 	}
 
 	cfq_put_queue(cfqq);
@@ -1549,9 +1131,10 @@ static struct cfq_io_context *
 cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
 {
 	struct cfq_io_context *cic;
+	struct request_queue *q = cfqd->queue;
 
 	cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
-							cfqd->queue->node);
+							q->node);
 	if (cic) {
 		cic->last_end_request = jiffies;
 		INIT_LIST_HEAD(&cic->queue_list);
@@ -1567,7 +1150,7 @@ cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
 static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
 {
 	struct task_struct *tsk = current;
-	int ioprio_class;
+	int ioprio_class, ioprio;
 
 	if (!cfq_cfqq_prio_changed(cfqq))
 		return;
@@ -1580,30 +1163,33 @@ static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
 		/*
 		 * no prio set, inherit CPU scheduling settings
 		 */
-		cfqq->ioprio = task_nice_ioprio(tsk);
-		cfqq->ioprio_class = task_nice_ioclass(tsk);
+		ioprio = task_nice_ioprio(tsk);
+		ioprio_class = task_nice_ioclass(tsk);
 		break;
 	case IOPRIO_CLASS_RT:
-		cfqq->ioprio = task_ioprio(ioc);
-		cfqq->ioprio_class = IOPRIO_CLASS_RT;
+		ioprio = task_ioprio(ioc);
+		ioprio_class = IOPRIO_CLASS_RT;
 		break;
 	case IOPRIO_CLASS_BE:
-		cfqq->ioprio = task_ioprio(ioc);
-		cfqq->ioprio_class = IOPRIO_CLASS_BE;
+		ioprio = task_ioprio(ioc);
+		ioprio_class = IOPRIO_CLASS_BE;
 		break;
 	case IOPRIO_CLASS_IDLE:
-		cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
-		cfqq->ioprio = 7;
-		cfq_clear_cfqq_idle_window(cfqq);
+		ioprio_class = IOPRIO_CLASS_IDLE;
+		ioprio = 7;
+		elv_clear_ioq_idle_window(cfqq->ioq);
 		break;
 	}
 
+	elv_ioq_set_ioprio_class(cfqq->ioq, ioprio_class);
+	elv_ioq_set_ioprio(cfqq->ioq, ioprio);
+
 	/*
 	 * keep track of original prio settings in case we have to temporarily
 	 * elevate the priority of this queue
 	 */
-	cfqq->org_ioprio = cfqq->ioprio;
-	cfqq->org_ioprio_class = cfqq->ioprio_class;
+	cfqq->org_ioprio = ioprio;
+	cfqq->org_ioprio_class = ioprio_class;
 	cfq_clear_cfqq_prio_changed(cfqq);
 }
 
@@ -1612,11 +1198,12 @@ static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
 	struct cfq_data *cfqd = cic->key;
 	struct cfq_queue *cfqq;
 	unsigned long flags;
+	struct request_queue *q = cfqd->queue;
 
 	if (unlikely(!cfqd))
 		return;
 
-	spin_lock_irqsave(cfqd->queue->queue_lock, flags);
+	spin_lock_irqsave(q->queue_lock, flags);
 
 	cfqq = cic->cfqq[BLK_RW_ASYNC];
 	if (cfqq) {
@@ -1633,7 +1220,7 @@ static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
 	if (cfqq)
 		cfq_mark_cfqq_prio_changed(cfqq);
 
-	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+	spin_unlock_irqrestore(q->queue_lock, flags);
 }
 
 static void cfq_ioc_set_ioprio(struct io_context *ioc)
@@ -1644,11 +1231,12 @@ static void cfq_ioc_set_ioprio(struct io_context *ioc)
 
 static struct cfq_queue *
 cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
-		     struct io_context *ioc, gfp_t gfp_mask)
+				struct io_context *ioc, gfp_t gfp_mask)
 {
 	struct cfq_queue *cfqq, *new_cfqq = NULL;
 	struct cfq_io_context *cic;
-
+	struct request_queue *q = cfqd->queue;
+	struct io_queue *ioq = NULL, *new_ioq = NULL;
 retry:
 	cic = cfq_cic_lookup(cfqd, ioc);
 	/* cic always exists here */
@@ -1656,8 +1244,7 @@ retry:
 
 	if (!cfqq) {
 		if (new_cfqq) {
-			cfqq = new_cfqq;
-			new_cfqq = NULL;
+			goto alloc_ioq;
 		} else if (gfp_mask & __GFP_WAIT) {
 			/*
 			 * Inform the allocator of the fact that we will
@@ -1678,22 +1265,52 @@ retry:
 			if (!cfqq)
 				goto out;
 		}
+alloc_ioq:
+		if (new_ioq) {
+			ioq = new_ioq;
+			new_ioq = NULL;
+			cfqq = new_cfqq;
+			new_cfqq = NULL;
+		} else if (gfp_mask & __GFP_WAIT) {
+			/*
+			 * Inform the allocator of the fact that we will
+			 * just repeat this allocation if it fails, to allow
+			 * the allocator to do whatever it needs to attempt to
+			 * free memory.
+			 */
+			spin_unlock_irq(q->queue_lock);
+			new_ioq = elv_alloc_ioq(q,
+					gfp_mask | __GFP_NOFAIL | __GFP_ZERO);
+			spin_lock_irq(q->queue_lock);
+			goto retry;
+		} else {
+			ioq = elv_alloc_ioq(q, gfp_mask | __GFP_ZERO);
+			if (!ioq) {
+				kmem_cache_free(cfq_pool, cfqq);
+				cfqq = NULL;
+				goto out;
+			}
+		}
 
-		RB_CLEAR_NODE(&cfqq->rb_node);
+		/*
+		 * Both cfqq and ioq objects allocated. Do the initializations
+		 * now.
+		 */
 		RB_CLEAR_NODE(&cfqq->p_node);
 		INIT_LIST_HEAD(&cfqq->fifo);
-
-		atomic_set(&cfqq->ref, 0);
 		cfqq->cfqd = cfqd;
 
 		cfq_mark_cfqq_prio_changed(cfqq);
 
+		cfqq->ioq = ioq;
 		cfq_init_prio_data(cfqq, ioc);
+		elv_init_ioq(q->elevator, ioq, cfqq, cfqq->org_ioprio_class,
+				cfqq->org_ioprio, is_sync);
 
 		if (is_sync) {
 			if (!cfq_class_idle(cfqq))
-				cfq_mark_cfqq_idle_window(cfqq);
-			cfq_mark_cfqq_sync(cfqq);
+				elv_mark_ioq_idle_window(cfqq->ioq);
+			elv_mark_ioq_sync(cfqq->ioq);
 		}
 		cfqq->pid = current->pid;
 		cfq_log_cfqq(cfqd, cfqq, "alloced");
@@ -1702,38 +1319,28 @@ retry:
 	if (new_cfqq)
 		kmem_cache_free(cfq_pool, new_cfqq);
 
+	if (new_ioq)
+		elv_free_ioq(new_ioq);
+
 out:
 	WARN_ON((gfp_mask & __GFP_WAIT) && !cfqq);
 	return cfqq;
 }
 
-static struct cfq_queue **
-cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
-{
-	switch (ioprio_class) {
-	case IOPRIO_CLASS_RT:
-		return &cfqd->async_cfqq[0][ioprio];
-	case IOPRIO_CLASS_BE:
-		return &cfqd->async_cfqq[1][ioprio];
-	case IOPRIO_CLASS_IDLE:
-		return &cfqd->async_idle_cfqq;
-	default:
-		BUG();
-	}
-}
-
 static struct cfq_queue *
 cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
-	      gfp_t gfp_mask)
+					gfp_t gfp_mask)
 {
 	const int ioprio = task_ioprio(ioc);
 	const int ioprio_class = task_ioprio_class(ioc);
-	struct cfq_queue **async_cfqq = NULL;
+	struct cfq_queue *async_cfqq = NULL;
 	struct cfq_queue *cfqq = NULL;
+	struct io_group *iog = io_lookup_io_group_current(cfqd->queue);
 
 	if (!is_sync) {
-		async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
-		cfqq = *async_cfqq;
+		async_cfqq = io_group_async_queue_prio(iog, ioprio_class,
+								ioprio);
+		cfqq = async_cfqq;
 	}
 
 	if (!cfqq) {
@@ -1742,15 +1349,11 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
 			return NULL;
 	}
 
-	/*
-	 * pin the queue now that it's allocated, scheduler exit will prune it
-	 */
-	if (!is_sync && !(*async_cfqq)) {
-		atomic_inc(&cfqq->ref);
-		*async_cfqq = cfqq;
-	}
+	if (!is_sync && !async_cfqq)
+		io_group_set_async_queue(iog, ioprio_class, ioprio, cfqq->ioq);
 
-	atomic_inc(&cfqq->ref);
+	/* ioc reference */
+	elv_get_ioq(cfqq->ioq);
 	return cfqq;
 }
 
@@ -1829,6 +1432,7 @@ static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
 {
 	unsigned long flags;
 	int ret;
+	struct request_queue *q = cfqd->queue;
 
 	ret = radix_tree_preload(gfp_mask);
 	if (!ret) {
@@ -1845,9 +1449,9 @@ static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
 		radix_tree_preload_end();
 
 		if (!ret) {
-			spin_lock_irqsave(cfqd->queue->queue_lock, flags);
+			spin_lock_irqsave(q->queue_lock, flags);
 			list_add(&cic->queue_list, &cfqd->cic_list);
-			spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
+			spin_unlock_irqrestore(q->queue_lock, flags);
 		}
 	}
 
@@ -1867,10 +1471,11 @@ cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
 {
 	struct io_context *ioc = NULL;
 	struct cfq_io_context *cic;
+	struct request_queue *q = cfqd->queue;
 
 	might_sleep_if(gfp_mask & __GFP_WAIT);
 
-	ioc = get_io_context(gfp_mask, cfqd->queue->node);
+	ioc = get_io_context(gfp_mask, q->node);
 	if (!ioc)
 		return NULL;
 
@@ -1889,7 +1494,6 @@ out:
 	smp_read_barrier_depends();
 	if (unlikely(ioc->ioprio_changed))
 		cfq_ioc_set_ioprio(ioc);
-
 	return cic;
 err_free:
 	cfq_cic_free(cic);
@@ -1899,17 +1503,6 @@ err:
 }
 
 static void
-cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
-{
-	unsigned long elapsed = jiffies - cic->last_end_request;
-	unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
-
-	cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
-	cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
-	cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
-}
-
-static void
 cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
 		       struct request *rq)
 {
@@ -1940,65 +1533,40 @@ cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
 }
 
 /*
- * Disable idle window if the process thinks too long or seeks so much that
- * it doesn't matter
+ * Disable idle window if the process seeks so much that it doesn't matter
  */
-static void
-cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
-		       struct cfq_io_context *cic)
+static int
+cfq_update_idle_window(struct elevator_queue *eq, void *cfqq,
+					struct request *rq)
 {
-	int old_idle, enable_idle;
+	struct cfq_io_context *cic = RQ_CIC(rq);
 
 	/*
-	 * Don't idle for async or idle io prio class
+	 * Enabling/Disabling idling based on thinktime has been moved
+	 * in common layer.
 	 */
-	if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
-		return;
-
-	enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
-
-	if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
-	    (cfqd->hw_tag && CIC_SEEKY(cic)))
-		enable_idle = 0;
-	else if (sample_valid(cic->ttime_samples)) {
-		if (cic->ttime_mean > cfqd->cfq_slice_idle)
-			enable_idle = 0;
-		else
-			enable_idle = 1;
-	}
+	if (!atomic_read(&cic->ioc->nr_tasks) ||
+	    (elv_hw_tag(eq) && CIC_SEEKY(cic)))
+		return 0;
 
-	if (old_idle != enable_idle) {
-		cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
-		if (enable_idle)
-			cfq_mark_cfqq_idle_window(cfqq);
-		else
-			cfq_clear_cfqq_idle_window(cfqq);
-	}
+	return 1;
 }
 
 /*
  * Check if new_cfqq should preempt the currently active queue. Return 0 for
- * no or if we aren't sure, a 1 will cause a preempt.
+ * no or if we aren't sure, a 1 will cause a preemption attempt.
+ * Some of the preemption logic has been moved to common layer. Only cfq
+ * specific parts are left here.
  */
 static int
-cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
-		   struct request *rq)
+cfq_should_preempt(struct request_queue *q, void *new_cfqq, struct request *rq)
 {
-	struct cfq_queue *cfqq;
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	struct cfq_queue *cfqq = elv_active_sched_queue(q->elevator);
 
-	cfqq = cfqd->active_queue;
 	if (!cfqq)
 		return 0;
 
-	if (cfq_slice_used(cfqq))
-		return 1;
-
-	if (cfq_class_idle(new_cfqq))
-		return 0;
-
-	if (cfq_class_idle(cfqq))
-		return 1;
-
 	/*
 	 * if the new request is sync, but the currently running queue is
 	 * not, let the sync request have priority.
@@ -2013,13 +1581,7 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
 	if (rq_is_meta(rq) && !cfqq->meta_pending)
 		return 1;
 
-	/*
-	 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
-	 */
-	if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
-		return 1;
-
-	if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
+	if (!cfqd->active_cic || !elv_ioq_wait_request(cfqq->ioq))
 		return 0;
 
 	/*
@@ -2033,29 +1595,10 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
 }
 
 /*
- * cfqq preempts the active queue. if we allowed preempt with no slice left,
- * let it have half of its nominal slice.
- */
-static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
-{
-	cfq_log_cfqq(cfqd, cfqq, "preempt");
-	cfq_slice_expired(cfqd, 1);
-
-	/*
-	 * Put the new queue at the front of the of the current list,
-	 * so we know that it will be selected next.
-	 */
-	BUG_ON(!cfq_cfqq_on_rr(cfqq));
-
-	cfq_service_tree_add(cfqd, cfqq, 1);
-
-	cfqq->slice_end = 0;
-	cfq_mark_cfqq_slice_new(cfqq);
-}
-
-/*
  * Called when a new fs request (rq) is added (to cfqq). Check if there's
  * something we should do about it
+ * After enqueuing the request whether queue should be preempted or kicked
+ * decision is taken by common layer.
  */
 static void
 cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
@@ -2063,45 +1606,12 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 {
 	struct cfq_io_context *cic = RQ_CIC(rq);
 
-	cfqd->rq_queued++;
 	if (rq_is_meta(rq))
 		cfqq->meta_pending++;
 
-	cfq_update_io_thinktime(cfqd, cic);
 	cfq_update_io_seektime(cfqd, cic, rq);
-	cfq_update_idle_window(cfqd, cfqq, cic);
 
 	cic->last_request_pos = rq->sector + rq->nr_sectors;
-
-	if (cfqq == cfqd->active_queue) {
-		/*
-		 * Remember that we saw a request from this process, but
-		 * don't start queuing just yet. Otherwise we risk seeing lots
-		 * of tiny requests, because we disrupt the normal plugging
-		 * and merging. If the request is already larger than a single
-		 * page, let it rip immediately. For that case we assume that
-		 * merging is already done. Ditto for a busy system that
-		 * has other work pending, don't risk delaying until the
-		 * idle timer unplug to continue working.
-		 */
-		if (cfq_cfqq_wait_request(cfqq)) {
-			if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
-			    cfqd->busy_queues > 1) {
-				del_timer(&cfqd->idle_slice_timer);
-				blk_start_queueing(cfqd->queue);
-			}
-			cfq_mark_cfqq_must_dispatch(cfqq);
-		}
-	} else if (cfq_should_preempt(cfqd, cfqq, rq)) {
-		/*
-		 * not the active queue - expire current slice if it is
-		 * idle and has expired it's mean thinktime or this new queue
-		 * has some old slice time left and is of higher priority or
-		 * this new queue is RT and the current one is BE
-		 */
-		cfq_preempt_queue(cfqd, cfqq);
-		blk_start_queueing(cfqd->queue);
-	}
 }
 
 static void cfq_insert_request(struct request_queue *q, struct request *rq)
@@ -2119,31 +1629,6 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
 	cfq_rq_enqueued(cfqd, cfqq, rq);
 }
 
-/*
- * Update hw_tag based on peak queue depth over 50 samples under
- * sufficient load.
- */
-static void cfq_update_hw_tag(struct cfq_data *cfqd)
-{
-	if (cfqd->rq_in_driver > cfqd->rq_in_driver_peak)
-		cfqd->rq_in_driver_peak = cfqd->rq_in_driver;
-
-	if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
-	    cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
-		return;
-
-	if (cfqd->hw_tag_samples++ < 50)
-		return;
-
-	if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN)
-		cfqd->hw_tag = 1;
-	else
-		cfqd->hw_tag = 0;
-
-	cfqd->hw_tag_samples = 0;
-	cfqd->rq_in_driver_peak = 0;
-}
-
 static void cfq_completed_request(struct request_queue *q, struct request *rq)
 {
 	struct cfq_queue *cfqq = RQ_CFQQ(rq);
@@ -2154,13 +1639,6 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
 	now = jiffies;
 	cfq_log_cfqq(cfqd, cfqq, "complete");
 
-	cfq_update_hw_tag(cfqd);
-
-	WARN_ON(!cfqd->rq_in_driver);
-	WARN_ON(!cfqq->dispatched);
-	cfqd->rq_in_driver--;
-	cfqq->dispatched--;
-
 	if (cfq_cfqq_sync(cfqq))
 		cfqd->sync_flight--;
 
@@ -2169,34 +1647,6 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
 
 	if (sync)
 		RQ_CIC(rq)->last_end_request = now;
-
-	/*
-	 * If this is the active queue, check if it needs to be expired,
-	 * or if we want to idle in case it has no pending requests.
-	 */
-	if (cfqd->active_queue == cfqq) {
-		const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
-
-		if (cfq_cfqq_slice_new(cfqq)) {
-			cfq_set_prio_slice(cfqd, cfqq);
-			cfq_clear_cfqq_slice_new(cfqq);
-		}
-		/*
-		 * If there are no requests waiting in this queue, and
-		 * there are other queues ready to issue requests, AND
-		 * those other queues are issuing requests within our
-		 * mean seek distance, give them a chance to run instead
-		 * of idling.
-		 */
-		if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
-			cfq_slice_expired(cfqd, 1);
-		else if (cfqq_empty && !cfq_close_cooperator(cfqd, cfqq, 1) &&
-			 sync && !rq_noidle(rq))
-			cfq_arm_slice_timer(cfqd);
-	}
-
-	if (!cfqd->rq_in_driver)
-		cfq_schedule_dispatch(cfqd);
 }
 
 /*
@@ -2205,30 +1655,33 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
  */
 static void cfq_prio_boost(struct cfq_queue *cfqq)
 {
+	struct io_queue *ioq = cfqq->ioq;
+
 	if (has_fs_excl()) {
 		/*
 		 * boost idle prio on transactions that would lock out other
 		 * users of the filesystem
 		 */
 		if (cfq_class_idle(cfqq))
-			cfqq->ioprio_class = IOPRIO_CLASS_BE;
-		if (cfqq->ioprio > IOPRIO_NORM)
-			cfqq->ioprio = IOPRIO_NORM;
+			elv_ioq_set_ioprio_class(ioq, IOPRIO_CLASS_BE);
+		if (elv_ioq_ioprio(ioq) > IOPRIO_NORM)
+			elv_ioq_set_ioprio(ioq, IOPRIO_NORM);
+
 	} else {
 		/*
 		 * check if we need to unboost the queue
 		 */
-		if (cfqq->ioprio_class != cfqq->org_ioprio_class)
-			cfqq->ioprio_class = cfqq->org_ioprio_class;
-		if (cfqq->ioprio != cfqq->org_ioprio)
-			cfqq->ioprio = cfqq->org_ioprio;
+		if (elv_ioq_ioprio_class(ioq) != cfqq->org_ioprio_class)
+			elv_ioq_set_ioprio_class(ioq, cfqq->org_ioprio_class);
+		if (elv_ioq_ioprio(ioq) != cfqq->org_ioprio)
+			elv_ioq_set_ioprio(ioq, cfqq->org_ioprio);
 	}
 }
 
 static inline int __cfq_may_queue(struct cfq_queue *cfqq)
 {
-	if ((cfq_cfqq_wait_request(cfqq) || cfq_cfqq_must_alloc(cfqq)) &&
-	    !cfq_cfqq_must_alloc_slice(cfqq)) {
+	if ((elv_ioq_wait_request(cfqq->ioq) ||
+	   cfq_cfqq_must_alloc(cfqq)) && !cfq_cfqq_must_alloc_slice(cfqq)) {
 		cfq_mark_cfqq_must_alloc_slice(cfqq);
 		return ELV_MQUEUE_MUST;
 	}
@@ -2320,119 +1773,31 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 
 	cfqq->allocated[rw]++;
 	cfq_clear_cfqq_must_alloc(cfqq);
-	atomic_inc(&cfqq->ref);
+	elv_get_ioq(cfqq->ioq);
 
 	spin_unlock_irqrestore(q->queue_lock, flags);
 
 	rq->elevator_private = cic;
-	rq->elevator_private2 = cfqq;
+	rq->ioq = cfqq->ioq;
 	return 0;
 
 queue_fail:
 	if (cic)
 		put_io_context(cic->ioc);
 
-	cfq_schedule_dispatch(cfqd);
+	elv_schedule_dispatch(cfqd->queue);
 	spin_unlock_irqrestore(q->queue_lock, flags);
 	cfq_log(cfqd, "set_request fail");
 	return 1;
 }
 
-static void cfq_kick_queue(struct work_struct *work)
-{
-	struct cfq_data *cfqd =
-		container_of(work, struct cfq_data, unplug_work);
-	struct request_queue *q = cfqd->queue;
-
-	spin_lock_irq(q->queue_lock);
-	blk_start_queueing(q);
-	spin_unlock_irq(q->queue_lock);
-}
-
-/*
- * Timer running if the active_queue is currently idling inside its time slice
- */
-static void cfq_idle_slice_timer(unsigned long data)
-{
-	struct cfq_data *cfqd = (struct cfq_data *) data;
-	struct cfq_queue *cfqq;
-	unsigned long flags;
-	int timed_out = 1;
-
-	cfq_log(cfqd, "idle timer fired");
-
-	spin_lock_irqsave(cfqd->queue->queue_lock, flags);
-
-	cfqq = cfqd->active_queue;
-	if (cfqq) {
-		timed_out = 0;
-
-		/*
-		 * We saw a request before the queue expired, let it through
-		 */
-		if (cfq_cfqq_must_dispatch(cfqq))
-			goto out_kick;
-
-		/*
-		 * expired
-		 */
-		if (cfq_slice_used(cfqq))
-			goto expire;
-
-		/*
-		 * only expire and reinvoke request handler, if there are
-		 * other queues with pending requests
-		 */
-		if (!cfqd->busy_queues)
-			goto out_cont;
-
-		/*
-		 * not expired and it has a request pending, let it dispatch
-		 */
-		if (!RB_EMPTY_ROOT(&cfqq->sort_list))
-			goto out_kick;
-	}
-expire:
-	cfq_slice_expired(cfqd, timed_out);
-out_kick:
-	cfq_schedule_dispatch(cfqd);
-out_cont:
-	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
-}
-
-static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
-{
-	del_timer_sync(&cfqd->idle_slice_timer);
-	cancel_work_sync(&cfqd->unplug_work);
-}
-
-static void cfq_put_async_queues(struct cfq_data *cfqd)
-{
-	int i;
-
-	for (i = 0; i < IOPRIO_BE_NR; i++) {
-		if (cfqd->async_cfqq[0][i])
-			cfq_put_queue(cfqd->async_cfqq[0][i]);
-		if (cfqd->async_cfqq[1][i])
-			cfq_put_queue(cfqd->async_cfqq[1][i]);
-	}
-
-	if (cfqd->async_idle_cfqq)
-		cfq_put_queue(cfqd->async_idle_cfqq);
-}
-
 static void cfq_exit_queue(struct elevator_queue *e)
 {
 	struct cfq_data *cfqd = e->elevator_data;
 	struct request_queue *q = cfqd->queue;
 
-	cfq_shutdown_timer_wq(cfqd);
-
 	spin_lock_irq(q->queue_lock);
 
-	if (cfqd->active_queue)
-		__cfq_slice_expired(cfqd, cfqd->active_queue, 0);
-
 	while (!list_empty(&cfqd->cic_list)) {
 		struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
 							struct cfq_io_context,
@@ -2441,12 +1806,7 @@ static void cfq_exit_queue(struct elevator_queue *e)
 		__cfq_exit_single_io_context(cfqd, cic);
 	}
 
-	cfq_put_async_queues(cfqd);
-
 	spin_unlock_irq(q->queue_lock);
-
-	cfq_shutdown_timer_wq(cfqd);
-
 	kfree(cfqd);
 }
 
@@ -2459,8 +1819,6 @@ static void *cfq_init_queue(struct request_queue *q)
 	if (!cfqd)
 		return NULL;
 
-	cfqd->service_tree = CFQ_RB_ROOT;
-
 	/*
 	 * Not strictly needed (since RB_ROOT just clears the node and we
 	 * zeroed cfqd on alloc), but better be safe in case someone decides
@@ -2473,23 +1831,13 @@ static void *cfq_init_queue(struct request_queue *q)
 
 	cfqd->queue = q;
 
-	init_timer(&cfqd->idle_slice_timer);
-	cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
-	cfqd->idle_slice_timer.data = (unsigned long) cfqd;
-
-	INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
-
 	cfqd->last_end_request = jiffies;
 	cfqd->cfq_quantum = cfq_quantum;
 	cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
 	cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
 	cfqd->cfq_back_max = cfq_back_max;
 	cfqd->cfq_back_penalty = cfq_back_penalty;
-	cfqd->cfq_slice[0] = cfq_slice_async;
-	cfqd->cfq_slice[1] = cfq_slice_sync;
 	cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
-	cfqd->cfq_slice_idle = cfq_slice_idle;
-	cfqd->hw_tag = 1;
 
 	return cfqd;
 }
@@ -2554,9 +1902,6 @@ SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
 SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
 SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
 SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
-SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
-SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
-SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
 SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
 #undef SHOW_FUNCTION
 
@@ -2584,9 +1929,6 @@ STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
 STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
 STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
 		UINT_MAX, 0);
-STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
-STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
-STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
 STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
 		UINT_MAX, 0);
 #undef STORE_FUNCTION
@@ -2600,10 +1942,7 @@ static struct elv_fs_entry cfq_attrs[] = {
 	CFQ_ATTR(fifo_expire_async),
 	CFQ_ATTR(back_seek_max),
 	CFQ_ATTR(back_seek_penalty),
-	CFQ_ATTR(slice_sync),
-	CFQ_ATTR(slice_async),
 	CFQ_ATTR(slice_async_rq),
-	CFQ_ATTR(slice_idle),
 	__ATTR_NULL
 };
 
@@ -2616,8 +1955,6 @@ static struct elevator_type iosched_cfq = {
 		.elevator_dispatch_fn =		cfq_dispatch_requests,
 		.elevator_add_req_fn =		cfq_insert_request,
 		.elevator_activate_req_fn =	cfq_activate_request,
-		.elevator_deactivate_req_fn =	cfq_deactivate_request,
-		.elevator_queue_empty_fn =	cfq_queue_empty,
 		.elevator_completed_req_fn =	cfq_completed_request,
 		.elevator_former_req_fn =	elv_rb_former_request,
 		.elevator_latter_req_fn =	elv_rb_latter_request,
@@ -2627,7 +1964,15 @@ static struct elevator_type iosched_cfq = {
 		.elevator_init_fn =		cfq_init_queue,
 		.elevator_exit_fn =		cfq_exit_queue,
 		.trim =				cfq_free_io_context,
+		.elevator_free_sched_queue_fn =	cfq_free_cfq_queue,
+		.elevator_active_ioq_set_fn = 	cfq_active_ioq_set,
+		.elevator_active_ioq_reset_fn =	cfq_active_ioq_reset,
+		.elevator_arm_slice_timer_fn = 	cfq_arm_slice_timer,
+		.elevator_should_preempt_fn = 	cfq_should_preempt,
+		.elevator_update_idle_window_fn = cfq_update_idle_window,
+		.elevator_close_cooperator_fn = cfq_close_cooperator,
 	},
+	.elevator_features =    ELV_IOSCHED_NEED_FQ,
 	.elevator_attrs =	cfq_attrs,
 	.elevator_name =	"cfq",
 	.elevator_owner =	THIS_MODULE,
@@ -2635,14 +1980,6 @@ static struct elevator_type iosched_cfq = {
 
 static int __init cfq_init(void)
 {
-	/*
-	 * could be 0 on HZ < 1000 setups
-	 */
-	if (!cfq_slice_async)
-		cfq_slice_async = 1;
-	if (!cfq_slice_idle)
-		cfq_slice_idle = 1;
-
 	if (cfq_slab_setup())
 		return -ENOMEM;
 
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 08b987b..0a2815d 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -42,10 +42,6 @@ struct cfq_io_context {
 	unsigned long last_end_request;
 	sector_t last_request_pos;
 
-	unsigned long ttime_total;
-	unsigned long ttime_samples;
-	unsigned long ttime_mean;
-
 	unsigned int seek_samples;
 	u64 seek_total;
 	sector_t seek_mean;
-- 
1.6.0.1

[PATCH 05/20] io-controller: Common hierarchical fair queuing code in elevaotor layer

[Vivek Goyal]

This patch enables hierarchical fair queuing in common layer. It is
controlled by config option CONFIG_GROUP_IOSCHED.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Fabio Checconi <fabio-f9ZlEuEWxVeACYmtYXMKmw@public.gmane.org>
Signed-off-by: Paolo Valente <paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org>
Signed-off-by: Aristeu Rozanski <aris-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/blk-ioc.c               |    3 +
 block/elevator-fq.c           | 1004 +++++++++++++++++++++++++++++++++++++----
 block/elevator-fq.h           |  142 ++++++-
 block/elevator.c              |    4 +
 include/linux/blkdev.h        |    2 +-
 include/linux/cgroup_subsys.h |    7 +
 include/linux/iocontext.h     |    5 +
 init/Kconfig                  |    8 +
 8 files changed, 1073 insertions(+), 102 deletions(-)

diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 012f065..8f0f6cf 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -95,6 +95,9 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
 		spin_lock_init(&ret->lock);
 		ret->ioprio_changed = 0;
 		ret->ioprio = 0;
+#ifdef CONFIG_GROUP_IOSCHED
+		ret->cgroup_changed = 0;
+#endif
 		ret->last_waited = jiffies; /* doesn't matter... */
 		ret->nr_batch_requests = 0; /* because this is 0 */
 		ret->aic = NULL;
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 73b997a..2ba6e92 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -24,6 +24,10 @@ static int elv_rate_sampling_window = HZ / 10;
 
 #define ELV_SLICE_SCALE		(5)
 #define ELV_HW_QUEUE_MIN	(5)
+
+#define IO_DEFAULT_GRP_WEIGHT  500
+#define IO_DEFAULT_GRP_CLASS   IOPRIO_CLASS_BE
+
 #define IO_SERVICE_TREE_INIT   ((struct io_service_tree)		\
 				{ RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
 
@@ -31,6 +35,7 @@ static inline struct io_queue *elv_close_cooperator(struct request_queue *q,
 					struct io_queue *ioq, int probe);
 struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
 						 int extract);
+void elv_release_ioq(struct elevator_queue *eq, struct io_queue **ioq_ptr);
 
 static inline int elv_prio_slice(struct elv_fq_data *efqd, int sync,
 					unsigned short prio)
@@ -49,6 +54,73 @@ elv_prio_to_slice(struct elv_fq_data *efqd, struct io_queue *ioq)
 }
 
 /* Mainly the BFQ scheduling code Follows */
+#ifdef CONFIG_GROUP_IOSCHED
+#define for_each_entity(entity)	\
+	for (; entity != NULL; entity = entity->parent)
+
+#define for_each_entity_safe(entity, parent) \
+	for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
+
+
+struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
+						 int extract);
+void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
+					int requeue);
+void elv_activate_ioq(struct io_queue *ioq, int add_front);
+void elv_deactivate_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
+					int requeue);
+
+static int bfq_update_next_active(struct io_sched_data *sd)
+{
+	struct io_group *iog;
+	struct io_entity *entity, *next_active;
+
+	if (sd->active_entity != NULL)
+		/* will update/requeue at the end of service */
+		return 0;
+
+	/*
+	 * NOTE: this can be improved in may ways, such as returning
+	 * 1 (and thus propagating upwards the update) only when the
+	 * budget changes, or caching the bfqq that will be scheduled
+	 * next from this subtree.  By now we worry more about
+	 * correctness than about performance...
+	 */
+	next_active = bfq_lookup_next_entity(sd, 0);
+	sd->next_active = next_active;
+
+	if (next_active != NULL) {
+		iog = container_of(sd, struct io_group, sched_data);
+		entity = iog->my_entity;
+		if (entity != NULL)
+			entity->budget = next_active->budget;
+	}
+
+	return 1;
+}
+
+static inline void bfq_check_next_active(struct io_sched_data *sd,
+					 struct io_entity *entity)
+{
+	BUG_ON(sd->next_active != entity);
+}
+#else /* GROUP_IOSCHED */
+#define for_each_entity(entity)	\
+	for (; entity != NULL; entity = NULL)
+
+#define for_each_entity_safe(entity, parent) \
+	for (parent = NULL; entity != NULL; entity = parent)
+
+static inline int bfq_update_next_active(struct io_sched_data *sd)
+{
+	return 0;
+}
+
+static inline void bfq_check_next_active(struct io_sched_data *sd,
+					 struct io_entity *entity)
+{
+}
+#endif
 
 /*
  * Shift for timestamp calculations.  This actually limits the maximum
@@ -286,7 +358,6 @@ static void bfq_active_insert(struct io_service_tree *st,
 	struct rb_node *node = &entity->rb_node;
 
 	bfq_insert(&st->active, entity);
-
 	if (node->rb_left != NULL)
 		node = node->rb_left;
 	else if (node->rb_right != NULL)
@@ -295,16 +366,6 @@ static void bfq_active_insert(struct io_service_tree *st,
 	bfq_update_active_tree(node);
 }
 
-/**
- * bfq_ioprio_to_weight - calc a weight from an ioprio.
- * @ioprio: the ioprio value to convert.
- */
-static bfq_weight_t bfq_ioprio_to_weight(int ioprio)
-{
-	WARN_ON(ioprio < 0 || ioprio >= IOPRIO_BE_NR);
-	return IOPRIO_BE_NR - ioprio;
-}
-
 void bfq_get_entity(struct io_entity *entity)
 {
 	struct io_queue *ioq = io_entity_to_ioq(entity);
@@ -313,13 +374,6 @@ void bfq_get_entity(struct io_entity *entity)
 		elv_get_ioq(ioq);
 }
 
-void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
-{
-	entity->ioprio = entity->new_ioprio;
-	entity->ioprio_class = entity->new_ioprio_class;
-	entity->sched_data = &iog->sched_data;
-}
-
 /**
  * bfq_find_deepest - find the deepest node that an extraction can modify.
  * @node: the node being removed.
@@ -362,7 +416,6 @@ static void bfq_active_extract(struct io_service_tree *st,
 
 	node = bfq_find_deepest(&entity->rb_node);
 	bfq_extract(&st->active, entity);
-
 	if (node != NULL)
 		bfq_update_active_tree(node);
 }
@@ -462,8 +515,10 @@ __bfq_entity_update_prio(struct io_service_tree *old_st,
 	struct io_queue *ioq = io_entity_to_ioq(entity);
 
 	if (entity->ioprio_changed) {
+		old_st->wsum -= entity->weight;
 		entity->ioprio = entity->new_ioprio;
 		entity->ioprio_class = entity->new_ioprio_class;
+		entity->weight = entity->new_weight;
 		entity->ioprio_changed = 0;
 
 		/*
@@ -475,9 +530,6 @@ __bfq_entity_update_prio(struct io_service_tree *old_st,
 			entity->budget = elv_prio_to_slice(efqd, ioq);
 		}
 
-		old_st->wsum -= entity->weight;
-		entity->weight = bfq_ioprio_to_weight(entity->ioprio);
-
 		/*
 		 * NOTE: here we may be changing the weight too early,
 		 * this will cause unfairness.  The correct approach
@@ -559,11 +611,8 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
 	if (add_front) {
 		struct io_entity *next_entity;
 
-		/*
-		 * Determine the entity which will be dispatched next
-		 * Use sd->next_active once hierarchical patch is applied
-		 */
-		next_entity = bfq_lookup_next_entity(sd, 0);
+		/* Determine the entity which will be dispatched next */
+		next_entity = sd->next_active;
 
 		if (next_entity && next_entity != entity) {
 			struct io_service_tree *new_st;
@@ -590,12 +639,27 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
 }
 
 /**
- * bfq_activate_entity - activate an entity.
+ * bfq_activate_entity - activate an entity and its ancestors if necessary.
  * @entity: the entity to activate.
+ * Activate @entity and all the entities on the path from it to the root.
  */
 void bfq_activate_entity(struct io_entity *entity, int add_front)
 {
-	__bfq_activate_entity(entity, add_front);
+	struct io_sched_data *sd;
+
+	for_each_entity(entity) {
+		__bfq_activate_entity(entity, add_front);
+
+		add_front = 0;
+		sd = entity->sched_data;
+		if (!bfq_update_next_active(sd))
+			/*
+			 * No need to propagate the activation to the
+			 * upper entities, as they will be updated when
+			 * the active entity is rescheduled.
+			 */
+			break;
+	}
 }
 
 /**
@@ -631,12 +695,16 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
 	else if (entity->tree != NULL)
 		BUG();
 
+	if (was_active || sd->next_active == entity)
+		ret = bfq_update_next_active(sd);
+
 	if (!requeue || !bfq_gt(entity->finish, st->vtime))
 		bfq_forget_entity(st, entity);
 	else
 		bfq_idle_insert(st, entity);
 
 	BUG_ON(sd->active_entity == entity);
+	BUG_ON(sd->next_active == entity);
 
 	return ret;
 }
@@ -648,7 +716,46 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
  */
 void bfq_deactivate_entity(struct io_entity *entity, int requeue)
 {
-	__bfq_deactivate_entity(entity, requeue);
+	struct io_sched_data *sd;
+	struct io_entity *parent;
+
+	for_each_entity_safe(entity, parent) {
+		sd = entity->sched_data;
+
+		if (!__bfq_deactivate_entity(entity, requeue))
+			/*
+			 * The parent entity is still backlogged, and
+			 * we don't need to update it as it is still
+			 * under service.
+			 */
+			break;
+
+		if (sd->next_active != NULL)
+			/*
+			 * The parent entity is still backlogged and
+			 * the budgets on the path towards the root
+			 * need to be updated.
+			 */
+			goto update;
+
+		/*
+		 * If we reach there the parent is no more backlogged and
+		 * we want to propagate the dequeue upwards.
+		 */
+		requeue = 1;
+	}
+
+	return;
+
+update:
+	entity = parent;
+	for_each_entity(entity) {
+		__bfq_activate_entity(entity, 0);
+
+		sd = entity->sched_data;
+		if (!bfq_update_next_active(sd))
+			break;
+	}
 }
 
 /**
@@ -765,8 +872,10 @@ struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
 		entity = __bfq_lookup_next_entity(st);
 		if (entity != NULL) {
 			if (extract) {
+				bfq_check_next_active(sd, entity);
 				bfq_active_extract(st, entity);
 				sd->active_entity = entity;
+				sd->next_active = NULL;
 			}
 			break;
 		}
@@ -779,13 +888,728 @@ void entity_served(struct io_entity *entity, bfq_service_t served)
 {
 	struct io_service_tree *st;
 
-	st = io_entity_service_tree(entity);
-	entity->service += served;
-	BUG_ON(st->wsum == 0);
-	st->vtime += bfq_delta(served, st->wsum);
-	bfq_forget_idle(st);
+	for_each_entity(entity) {
+		st = io_entity_service_tree(entity);
+		entity->service += served;
+		BUG_ON(st->wsum == 0);
+		st->vtime += bfq_delta(served, st->wsum);
+		bfq_forget_idle(st);
+	}
+}
+
+/*
+ * Release all the io group references to its async queues.
+ */
+void io_put_io_group_queues(struct elevator_queue *e, struct io_group *iog)
+{
+	int i, j;
+
+	for (i = 0; i < 2; i++)
+		for (j = 0; j < IOPRIO_BE_NR; j++)
+			elv_release_ioq(e, &iog->async_queue[i][j]);
+
+	/* Free up async idle queue */
+	elv_release_ioq(e, &iog->async_idle_queue);
+}
+
+
+/* Mainly hierarchical grouping code */
+#ifdef CONFIG_GROUP_IOSCHED
+
+struct io_cgroup io_root_cgroup = {
+	.weight = IO_DEFAULT_GRP_WEIGHT,
+	.ioprio_class = IO_DEFAULT_GRP_CLASS,
+};
+
+void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
+{
+	entity->ioprio = entity->new_ioprio;
+	entity->weight = entity->new_weight;
+	entity->ioprio_class = entity->new_ioprio_class;
+	entity->parent = iog->my_entity;
+	entity->sched_data = &iog->sched_data;
+}
+
+struct io_cgroup *cgroup_to_io_cgroup(struct cgroup *cgroup)
+{
+	return container_of(cgroup_subsys_state(cgroup, io_subsys_id),
+			    struct io_cgroup, css);
+}
+
+/*
+ * Search the bfq_group for bfqd into the hash table (by now only a list)
+ * of bgrp.  Must be called under rcu_read_lock().
+ */
+struct io_group *io_cgroup_lookup_group(struct io_cgroup *iocg, void *key)
+{
+	struct io_group *iog;
+	struct hlist_node *n;
+	void *__key;
+
+	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
+		__key = rcu_dereference(iog->key);
+		if (__key == key)
+			return iog;
+	}
+
+	return NULL;
+}
+
+void io_group_init_entity(struct io_cgroup *iocg, struct io_group *iog)
+{
+	struct io_entity *entity = &iog->entity;
+
+	entity->weight = entity->new_weight = iocg->weight;
+	entity->ioprio_class = entity->new_ioprio_class = iocg->ioprio_class;
+	entity->ioprio_changed = 1;
+	entity->my_sched_data = &iog->sched_data;
+}
+
+void io_group_set_parent(struct io_group *iog, struct io_group *parent)
+{
+	struct io_entity *entity;
+
+	BUG_ON(parent == NULL);
+	BUG_ON(iog == NULL);
+
+	entity = &iog->entity;
+	entity->parent = parent->my_entity;
+	entity->sched_data = &parent->sched_data;
+}
+
+/**
+ * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st.
+ * @st: the service tree being flushed.
+ */
+void io_flush_idle_tree(struct io_service_tree *st)
+{
+	struct io_entity *entity = st->first_idle;
+
+	for (; entity != NULL; entity = st->first_idle)
+		__bfq_deactivate_entity(entity, 0);
+}
+
+#define SHOW_FUNCTION(__VAR)						\
+static u64 io_cgroup_##__VAR##_read(struct cgroup *cgroup,		\
+				       struct cftype *cftype)		\
+{									\
+	struct io_cgroup *iocg;					\
+	u64 ret;							\
+									\
+	if (!cgroup_lock_live_group(cgroup))				\
+		return -ENODEV;						\
+									\
+	iocg = cgroup_to_io_cgroup(cgroup);				\
+	spin_lock_irq(&iocg->lock);					\
+	ret = iocg->__VAR;						\
+	spin_unlock_irq(&iocg->lock);					\
+									\
+	cgroup_unlock();						\
+									\
+	return ret;							\
+}
+
+SHOW_FUNCTION(weight);
+SHOW_FUNCTION(ioprio_class);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__VAR, __MIN, __MAX)				\
+static int io_cgroup_##__VAR##_write(struct cgroup *cgroup,		\
+					struct cftype *cftype,		\
+					u64 val)			\
+{									\
+	struct io_cgroup *iocg;					\
+	struct io_group *iog;						\
+	struct hlist_node *n;						\
+									\
+	if (val < (__MIN) || val > (__MAX))				\
+		return -EINVAL;						\
+									\
+	if (!cgroup_lock_live_group(cgroup))				\
+		return -ENODEV;						\
+									\
+	iocg = cgroup_to_io_cgroup(cgroup);				\
+									\
+	spin_lock_irq(&iocg->lock);					\
+	iocg->__VAR = (unsigned long)val;				\
+	hlist_for_each_entry(iog, n, &iocg->group_data, group_node) {	\
+		iog->entity.new_##__VAR = (unsigned long)val;		\
+		smp_wmb();						\
+		iog->entity.ioprio_changed = 1;				\
+	}								\
+	spin_unlock_irq(&iocg->lock);					\
+									\
+	cgroup_unlock();						\
+									\
+	return 0;							\
+}
+
+STORE_FUNCTION(weight, 1, WEIGHT_MAX);
+STORE_FUNCTION(ioprio_class, IOPRIO_CLASS_RT, IOPRIO_CLASS_IDLE);
+#undef STORE_FUNCTION
+
+/**
+ * bfq_group_chain_alloc - allocate a chain of groups.
+ * @bfqd: queue descriptor.
+ * @cgroup: the leaf cgroup this chain starts from.
+ *
+ * Allocate a chain of groups starting from the one belonging to
+ * @cgroup up to the root cgroup.  Stop if a cgroup on the chain
+ * to the root has already an allocated group on @bfqd.
+ */
+struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
+					struct cgroup *cgroup)
+{
+	struct io_cgroup *iocg;
+	struct io_group *iog, *leaf = NULL, *prev = NULL;
+	gfp_t flags = GFP_ATOMIC |  __GFP_ZERO;
+
+	for (; cgroup != NULL; cgroup = cgroup->parent) {
+		iocg = cgroup_to_io_cgroup(cgroup);
+
+		iog = io_cgroup_lookup_group(iocg, key);
+		if (iog != NULL) {
+			/*
+			 * All the cgroups in the path from there to the
+			 * root must have a bfq_group for bfqd, so we don't
+			 * need any more allocations.
+			 */
+			break;
+		}
+
+		iog = kzalloc_node(sizeof(*iog), flags, q->node);
+		if (!iog)
+			goto cleanup;
+
+		io_group_init_entity(iocg, iog);
+		iog->my_entity = &iog->entity;
+
+		if (leaf == NULL) {
+			leaf = iog;
+			prev = leaf;
+		} else {
+			io_group_set_parent(prev, iog);
+			/*
+			 * Build a list of allocated nodes using the bfqd
+			 * filed, that is still unused and will be initialized
+			 * only after the node will be connected.
+			 */
+			prev->key = iog;
+			prev = iog;
+		}
+	}
+
+	return leaf;
+
+cleanup:
+	while (leaf != NULL) {
+		prev = leaf;
+		leaf = leaf->key;
+		kfree(prev);
+	}
+
+	return NULL;
+}
+
+/**
+ * bfq_group_chain_link - link an allocatd group chain to a cgroup hierarchy.
+ * @bfqd: the queue descriptor.
+ * @cgroup: the leaf cgroup to start from.
+ * @leaf: the leaf group (to be associated to @cgroup).
+ *
+ * Try to link a chain of groups to a cgroup hierarchy, connecting the
+ * nodes bottom-up, so we can be sure that when we find a cgroup in the
+ * hierarchy that already as a group associated to @bfqd all the nodes
+ * in the path to the root cgroup have one too.
+ *
+ * On locking: the queue lock protects the hierarchy (there is a hierarchy
+ * per device) while the bfqio_cgroup lock protects the list of groups
+ * belonging to the same cgroup.
+ */
+void io_group_chain_link(struct request_queue *q, void *key,
+				struct cgroup *cgroup,
+				struct io_group *leaf,
+				struct elv_fq_data *efqd)
+{
+	struct io_cgroup *iocg;
+	struct io_group *iog, *next, *prev = NULL;
+	unsigned long flags;
+
+	assert_spin_locked(q->queue_lock);
+
+	for (; cgroup != NULL && leaf != NULL; cgroup = cgroup->parent) {
+		iocg = cgroup_to_io_cgroup(cgroup);
+		next = leaf->key;
+
+		iog = io_cgroup_lookup_group(iocg, key);
+		BUG_ON(iog != NULL);
+
+		spin_lock_irqsave(&iocg->lock, flags);
+
+		rcu_assign_pointer(leaf->key, key);
+		hlist_add_head_rcu(&leaf->group_node, &iocg->group_data);
+		hlist_add_head(&leaf->elv_data_node, &efqd->group_list);
+
+		spin_unlock_irqrestore(&iocg->lock, flags);
+
+		prev = leaf;
+		leaf = next;
+	}
+
+	BUG_ON(cgroup == NULL && leaf != NULL);
+
+	if (cgroup != NULL && prev != NULL) {
+		iocg = cgroup_to_io_cgroup(cgroup);
+		iog = io_cgroup_lookup_group(iocg, key);
+		io_group_set_parent(prev, iog);
+	}
+}
+
+/**
+ * bfq_find_alloc_group - return the group associated to @bfqd in @cgroup.
+ * @bfqd: queue descriptor.
+ * @cgroup: cgroup being searched for.
+ * @create: if set to 1, create the io group if it has not been created yet.
+ *
+ * Return a group associated to @bfqd in @cgroup, allocating one if
+ * necessary.  When a group is returned all the cgroups in the path
+ * to the root have a group associated to @bfqd.
+ *
+ * If the allocation fails, return the root group: this breaks guarantees
+ * but is a safe fallbak.  If this loss becames a problem it can be
+ * mitigated using the equivalent weight (given by the product of the
+ * weights of the groups in the path from @group to the root) in the
+ * root scheduler.
+ *
+ * We allocate all the missing nodes in the path from the leaf cgroup
+ * to the root and we connect the nodes only after all the allocations
+ * have been successful.
+ */
+struct io_group *io_find_alloc_group(struct request_queue *q,
+			struct cgroup *cgroup, struct elv_fq_data *efqd,
+			int create)
+{
+	struct io_cgroup *iocg = cgroup_to_io_cgroup(cgroup);
+	struct io_group *iog = NULL;
+	/* Note: Use efqd as key */
+	void *key = efqd;
+
+	iog = io_cgroup_lookup_group(iocg, key);
+	if (iog != NULL || !create)
+		return iog;
+
+	iog = io_group_chain_alloc(q, key, cgroup);
+	if (iog != NULL)
+		io_group_chain_link(q, key, cgroup, iog, efqd);
+
+	return iog;
+}
+
+/*
+ * Search for the io group current task belongs to. If create=1, then also
+ * create the io group if it is not already there.
+ */
+struct io_group *io_get_io_group(struct request_queue *q, int create)
+{
+	struct cgroup *cgroup;
+	struct io_group *iog;
+	struct elv_fq_data *efqd = &q->elevator->efqd;
+
+	rcu_read_lock();
+	cgroup = task_cgroup(current, io_subsys_id);
+	iog = io_find_alloc_group(q, cgroup, efqd, create);
+	if (!iog) {
+		if (create)
+			iog = efqd->root_group;
+		else
+			/*
+			 * bio merge functions doing lookup don't want to
+			 * map bio to root group by default
+			 */
+			iog = NULL;
+	}
+	rcu_read_unlock();
+	return iog;
+}
+EXPORT_SYMBOL(io_get_io_group);
+
+void io_free_root_group(struct elevator_queue *e)
+{
+	struct io_cgroup *iocg = &io_root_cgroup;
+	struct elv_fq_data *efqd = &e->efqd;
+	struct io_group *iog = efqd->root_group;
+
+	BUG_ON(!iog);
+	spin_lock_irq(&iocg->lock);
+	hlist_del_rcu(&iog->group_node);
+	spin_unlock_irq(&iocg->lock);
+	io_put_io_group_queues(e, iog);
+	kfree(iog);
+}
+
+struct io_group *io_alloc_root_group(struct request_queue *q,
+					struct elevator_queue *e, void *key)
+{
+	struct io_group *iog;
+	struct io_cgroup *iocg;
+	int i;
+
+	iog = kmalloc_node(sizeof(*iog), GFP_KERNEL | __GFP_ZERO, q->node);
+	if (iog == NULL)
+		return NULL;
+
+	iog->entity.parent = NULL;
+	for (i = 0; i < IO_IOPRIO_CLASSES; i++)
+		iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
+
+	iocg = &io_root_cgroup;
+	spin_lock_irq(&iocg->lock);
+	rcu_assign_pointer(iog->key, key);
+	hlist_add_head_rcu(&iog->group_node, &iocg->group_data);
+	spin_unlock_irq(&iocg->lock);
+
+	return iog;
+}
+
+struct cftype bfqio_files[] = {
+	{
+		.name = "weight",
+		.read_u64 = io_cgroup_weight_read,
+		.write_u64 = io_cgroup_weight_write,
+	},
+	{
+		.name = "ioprio_class",
+		.read_u64 = io_cgroup_ioprio_class_read,
+		.write_u64 = io_cgroup_ioprio_class_write,
+	},
+};
+
+int iocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
+{
+	return cgroup_add_files(cgroup, subsys, bfqio_files,
+				ARRAY_SIZE(bfqio_files));
+}
+
+struct cgroup_subsys_state *iocg_create(struct cgroup_subsys *subsys,
+						struct cgroup *cgroup)
+{
+	struct io_cgroup *iocg;
+
+	if (cgroup->parent != NULL) {
+		iocg = kzalloc(sizeof(*iocg), GFP_KERNEL);
+		if (iocg == NULL)
+			return ERR_PTR(-ENOMEM);
+	} else
+		iocg = &io_root_cgroup;
+
+	spin_lock_init(&iocg->lock);
+	INIT_HLIST_HEAD(&iocg->group_data);
+	iocg->weight = IO_DEFAULT_GRP_WEIGHT;
+	iocg->ioprio_class = IO_DEFAULT_GRP_CLASS;
+
+	return &iocg->css;
+}
+
+/*
+ * We cannot support shared io contexts, as we have no mean to support
+ * two tasks with the same ioc in two different groups without major rework
+ * of the main cic/bfqq data structures.  By now we allow a task to change
+ * its cgroup only if it's the only owner of its ioc; the drawback of this
+ * behavior is that a group containing a task that forked using CLONE_IO
+ * will not be destroyed until the tasks sharing the ioc die.
+ */
+int iocg_can_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
+			    struct task_struct *tsk)
+{
+	struct io_context *ioc;
+	int ret = 0;
+
+	/* task_lock() is needed to avoid races with exit_io_context() */
+	task_lock(tsk);
+	ioc = tsk->io_context;
+	if (ioc != NULL && atomic_read(&ioc->nr_tasks) > 1)
+		/*
+		 * ioc == NULL means that the task is either too young or
+		 * exiting: if it has still no ioc the ioc can't be shared,
+		 * if the task is exiting the attach will fail anyway, no
+		 * matter what we return here.
+		 */
+		ret = -EINVAL;
+	task_unlock(tsk);
+
+	return ret;
+}
+
+void iocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
+			 struct cgroup *prev, struct task_struct *tsk)
+{
+	struct io_context *ioc;
+
+	task_lock(tsk);
+	ioc = tsk->io_context;
+	if (ioc != NULL)
+		ioc->cgroup_changed = 1;
+	task_unlock(tsk);
+}
+
+/*
+ * Move the queue to the root group if it is active. This is needed when
+ * a cgroup is being deleted and all the IO is not done yet. This is not
+ * very good scheme as a user might get unfair share. This needs to be
+ * fixed.
+ */
+void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
+				struct io_group *iog)
+{
+	int busy, resume;
+	struct io_entity *entity = &ioq->entity;
+	struct elv_fq_data *efqd = &e->efqd;
+	struct io_service_tree *st = io_entity_service_tree(entity);
+
+	busy = elv_ioq_busy(ioq);
+	resume = !!ioq->nr_queued;
+
+	BUG_ON(resume && !entity->on_st);
+	BUG_ON(busy && !resume && entity->on_st && ioq != efqd->active_queue);
+
+	/*
+	 * We could be moving an queue which is on idle tree of previous group
+	 * What to do? I guess anyway this queue does not have any requests.
+	 * just forget the entity and free up from idle tree.
+	 *
+	 * This needs cleanup. Hackish.
+	 */
+	if (entity->tree == &st->idle) {
+		BUG_ON(atomic_read(&ioq->ref) < 2);
+		bfq_put_idle_entity(st, entity);
+	}
+
+	if (busy) {
+		BUG_ON(atomic_read(&ioq->ref) < 2);
+
+		if (!resume)
+			elv_del_ioq_busy(e, ioq, 0);
+		else
+			elv_deactivate_ioq(efqd, ioq, 0);
+	}
+
+	/*
+	 * Here we use a reference to bfqg.  We don't need a refcounter
+	 * as the cgroup reference will not be dropped, so that its
+	 * destroy() callback will not be invoked.
+	 */
+	entity->parent = iog->my_entity;
+	entity->sched_data = &iog->sched_data;
+
+	if (busy && resume)
+		elv_activate_ioq(ioq, 0);
+}
+EXPORT_SYMBOL(io_ioq_move);
+
+static void __io_destroy_group(struct elv_fq_data *efqd, struct io_group *iog)
+{
+	struct elevator_queue *eq;
+	struct io_entity *entity = iog->my_entity;
+	struct io_service_tree *st;
+	int i;
+
+	eq = container_of(efqd, struct elevator_queue, efqd);
+	hlist_del(&iog->elv_data_node);
+	__bfq_deactivate_entity(entity, 0);
+	io_put_io_group_queues(eq, iog);
+
+	for (i = 0; i < IO_IOPRIO_CLASSES; i++) {
+		st = iog->sched_data.service_tree + i;
+
+		/*
+		 * The idle tree may still contain bfq_queues belonging
+		 * to exited task because they never migrated to a different
+		 * cgroup from the one being destroyed now.  Noone else
+		 * can access them so it's safe to act without any lock.
+		 */
+		io_flush_idle_tree(st);
+
+		BUG_ON(!RB_EMPTY_ROOT(&st->active));
+		BUG_ON(!RB_EMPTY_ROOT(&st->idle));
+	}
+
+	BUG_ON(iog->sched_data.next_active != NULL);
+	BUG_ON(iog->sched_data.active_entity != NULL);
+	BUG_ON(entity->tree != NULL);
+}
+
+/**
+ * bfq_destroy_group - destroy @bfqg.
+ * @bgrp: the bfqio_cgroup containing @bfqg.
+ * @bfqg: the group being destroyed.
+ *
+ * Destroy @bfqg, making sure that it is not referenced from its parent.
+ */
+static void io_destroy_group(struct io_cgroup *iocg, struct io_group *iog)
+{
+	struct elv_fq_data *efqd = NULL;
+	unsigned long uninitialized_var(flags);
+
+	/* Remove io group from cgroup list */
+	hlist_del(&iog->group_node);
+
+	/*
+	 * io groups are linked in two lists. One list is maintained
+	 * in elevator (efqd->group_list) and other is maintained
+	 * per cgroup structure (iocg->group_data).
+	 *
+	 * While a cgroup is being deleted, elevator also might be
+	 * exiting and both might try to cleanup the same io group
+	 * so need to be little careful.
+	 *
+	 * Following code first accesses efqd under RCU to make sure
+	 * iog->key is pointing to valid efqd and then takes the
+	 * associated queue lock. After gettting the queue lock it
+	 * again checks whether elevator exit path had alreday got
+	 * hold of io group (iog->key == NULL). If yes, it does not
+	 * try to free up async queues again or flush the idle tree.
+	 */
+
+	rcu_read_lock();
+	efqd = rcu_dereference(iog->key);
+	if (efqd != NULL) {
+		spin_lock_irqsave(efqd->queue->queue_lock, flags);
+		if (iog->key == efqd)
+			__io_destroy_group(efqd, iog);
+		spin_unlock_irqrestore(efqd->queue->queue_lock, flags);
+	}
+	rcu_read_unlock();
+
+	/*
+	 * No need to defer the kfree() to the end of the RCU grace
+	 * period: we are called from the destroy() callback of our
+	 * cgroup, so we can be sure that noone is a) still using
+	 * this cgroup or b) doing lookups in it.
+	 */
+	kfree(iog);
+}
+
+void iocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
+{
+	struct io_cgroup *iocg = cgroup_to_io_cgroup(cgroup);
+	struct hlist_node *n, *tmp;
+	struct io_group *iog;
+
+	/*
+	 * Since we are destroying the cgroup, there are no more tasks
+	 * referencing it, and all the RCU grace periods that may have
+	 * referenced it are ended (as the destruction of the parent
+	 * cgroup is RCU-safe); bgrp->group_data will not be accessed by
+	 * anything else and we don't need any synchronization.
+	 */
+	hlist_for_each_entry_safe(iog, n, tmp, &iocg->group_data, group_node)
+		io_destroy_group(iocg, iog);
+
+	BUG_ON(!hlist_empty(&iocg->group_data));
+
+	kfree(iocg);
+}
+
+void io_disconnect_groups(struct elevator_queue *e)
+{
+	struct hlist_node *pos, *n;
+	struct io_group *iog;
+	struct elv_fq_data *efqd = &e->efqd;
+
+	hlist_for_each_entry_safe(iog, pos, n, &efqd->group_list,
+					elv_data_node) {
+		hlist_del(&iog->elv_data_node);
+
+		__bfq_deactivate_entity(iog->my_entity, 0);
+
+		/*
+		 * Don't remove from the group hash, just set an
+		 * invalid key.  No lookups can race with the
+		 * assignment as bfqd is being destroyed; this
+		 * implies also that new elements cannot be added
+		 * to the list.
+		 */
+		rcu_assign_pointer(iog->key, NULL);
+		io_put_io_group_queues(e, iog);
+	}
+}
+
+struct cgroup_subsys io_subsys = {
+	.name = "io",
+	.create = iocg_create,
+	.can_attach = iocg_can_attach,
+	.attach = iocg_attach,
+	.destroy = iocg_destroy,
+	.populate = iocg_populate,
+	.subsys_id = io_subsys_id,
+};
+
+/*
+ * if bio sumbmitting task and rq don't belong to same io_group, it can't
+ * be merged
+ */
+int io_group_allow_merge(struct request *rq, struct bio *bio)
+{
+	struct request_queue *q = rq->q;
+	struct io_queue *ioq = rq->ioq;
+	struct io_group *iog, *__iog;
+
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return 1;
+
+	/* Determine the io group of the bio submitting task */
+	iog = io_get_io_group(q, 0);
+	if (!iog) {
+		/* May be task belongs to a differet cgroup for which io
+		 * group has not been setup yet. */
+		return 0;
+	}
+
+	/* Determine the io group of the ioq, rq belongs to*/
+	__iog = ioq_to_io_group(ioq);
+
+	return (iog == __iog);
+}
+
+#else /* GROUP_IOSCHED */
+void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
+{
+	entity->ioprio = entity->new_ioprio;
+	entity->weight = entity->new_weight;
+	entity->ioprio_class = entity->new_ioprio_class;
+	entity->sched_data = &iog->sched_data;
 }
 
+struct io_group *io_alloc_root_group(struct request_queue *q,
+					struct elevator_queue *e, void *key)
+{
+	struct io_group *iog;
+	int i;
+
+	iog = kmalloc_node(sizeof(*iog), GFP_KERNEL | __GFP_ZERO, q->node);
+	if (iog == NULL)
+		return NULL;
+
+	for (i = 0; i < IO_IOPRIO_CLASSES; i++)
+		iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
+
+	return iog;
+}
+
+void io_free_root_group(struct elevator_queue *e)
+{
+	struct io_group *iog = e->efqd.root_group;
+	io_put_io_group_queues(e, iog);
+	kfree(iog);
+}
+
+struct io_group *io_get_io_group(struct request_queue *q, int create)
+{
+	return q->elevator->efqd.root_group;
+}
+EXPORT_SYMBOL(io_get_io_group);
+#endif /* CONFIG_GROUP_IOSCHED*/
+
 /* Elevator fair queuing function */
 struct io_queue *rq_ioq(struct request *rq)
 {
@@ -1131,11 +1955,10 @@ void elv_free_ioq(struct io_queue *ioq)
 EXPORT_SYMBOL(elv_free_ioq);
 
 int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq,
-			void *sched_queue, int ioprio_class, int ioprio,
-			int is_sync)
+		struct io_group *iog, void *sched_queue, int ioprio_class,
+		int ioprio, int is_sync)
 {
 	struct elv_fq_data *efqd = &eq->efqd;
-	struct io_group *iog = io_lookup_io_group_current(efqd->queue);
 
 	RB_CLEAR_NODE(&ioq->entity.rb_node);
 	atomic_set(&ioq->ref, 0);
@@ -1177,9 +2000,11 @@ EXPORT_SYMBOL(elv_put_ioq);
 
 void elv_release_ioq(struct elevator_queue *e, struct io_queue **ioq_ptr)
 {
+	struct io_group *root_group = e->efqd.root_group;
 	struct io_queue *ioq = *ioq_ptr;
 
 	if (ioq != NULL) {
+		io_ioq_move(e, ioq, root_group);
 		/* Drop the reference taken by the io group */
 		elv_put_ioq(ioq);
 		*ioq_ptr = NULL;
@@ -1233,14 +2058,27 @@ struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
 		return NULL;
 
 	sd = &efqd->root_group->sched_data;
-	if (extract)
-		entity = bfq_lookup_next_entity(sd, 1);
-	else
-		entity = bfq_lookup_next_entity(sd, 0);
+	for (; sd != NULL; sd = entity->my_sched_data) {
+		if (extract)
+			entity = bfq_lookup_next_entity(sd, 1);
+		else
+			entity = bfq_lookup_next_entity(sd, 0);
+
+		/*
+		 * entity can be null despite the fact that there are busy
+		 * queues. if all the busy queues are under a group which is
+		 * currently under service.
+		 * So if we are just looking for next ioq while something is
+		 * being served, null entity is not an error.
+		 */
+		BUG_ON(!entity && extract);
 
-	BUG_ON(!entity);
-	if (extract)
-		entity->service = 0;
+		if (extract)
+			entity->service = 0;
+
+		if (!entity)
+			return NULL;
+	}
 	ioq = io_entity_to_ioq(entity);
 
 	return ioq;
@@ -1256,8 +2094,12 @@ static void __elv_set_active_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
 	struct request_queue *q = efqd->queue;
 
 	if (ioq) {
-		elv_log_ioq(efqd, ioq, "set_active, busy=%d",
-							efqd->busy_queues);
+		struct io_group *iog = ioq_to_io_group(ioq);
+		elv_log_ioq(efqd, ioq, "set_active, busy=%d ioprio=%d"
+				" weight=%ld group_weight=%ld",
+				efqd->busy_queues,
+				ioq->entity.ioprio, ioq->entity.weight,
+				iog_weight(iog));
 		ioq->slice_end = 0;
 
 		elv_clear_ioq_wait_request(ioq);
@@ -1492,6 +2334,7 @@ int elv_should_preempt(struct request_queue *q, struct io_queue *new_ioq,
 {
 	struct io_queue *ioq;
 	struct elevator_queue *eq = q->elevator;
+	struct io_group *iog = NULL, *new_iog = NULL;
 
 	ioq = elv_active_ioq(eq);
 
@@ -1509,14 +2352,26 @@ int elv_should_preempt(struct request_queue *q, struct io_queue *new_ioq,
 
 	/*
 	 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
+	 *
+	 * TODO: In hierarchical setup, one need to traverse up the hier
+	 * till both the queues are children of same parent to make a
+	 * decision whether to do the preemption or not. Something like
+	 * what cfs has done for cpu scheduler. Will do it little later.
 	 */
 	if (elv_ioq_class_rt(new_ioq) && !elv_ioq_class_rt(ioq))
 		return 1;
 
+	iog = ioq_to_io_group(ioq);
+	new_iog = ioq_to_io_group(new_ioq);
+
 	/*
-	 * Check with io scheduler if it has additional criterion based on
-	 * which it wants to preempt existing queue.
+	 * If both the queues belong to same group, check with io scheduler
+	 * if it has additional criterion based on which it wants to
+	 * preempt existing queue.
 	 */
+	if (iog != new_iog)
+		return 0;
+
 	if (eq->ops->elevator_should_preempt_fn)
 		return eq->ops->elevator_should_preempt_fn(q, new_ioq, rq);
 
@@ -1940,14 +2795,6 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
 		elv_schedule_dispatch(q);
 }
 
-struct io_group *io_lookup_io_group_current(struct request_queue *q)
-{
-	struct elv_fq_data *efqd = &q->elevator->efqd;
-
-	return efqd->root_group;
-}
-EXPORT_SYMBOL(io_lookup_io_group_current);
-
 void *io_group_async_queue_prio(struct io_group *iog, int ioprio_class,
 					int ioprio)
 {
@@ -1998,44 +2845,6 @@ void io_group_set_async_queue(struct io_group *iog, int ioprio_class,
 }
 EXPORT_SYMBOL(io_group_set_async_queue);
 
-/*
- * Release all the io group references to its async queues.
- */
-void io_put_io_group_queues(struct elevator_queue *e, struct io_group *iog)
-{
-	int i, j;
-
-	for (i = 0; i < 2; i++)
-		for (j = 0; j < IOPRIO_BE_NR; j++)
-			elv_release_ioq(e, &iog->async_queue[i][j]);
-
-	/* Free up async idle queue */
-	elv_release_ioq(e, &iog->async_idle_queue);
-}
-
-struct io_group *io_alloc_root_group(struct request_queue *q,
-					struct elevator_queue *e, void *key)
-{
-	struct io_group *iog;
-	int i;
-
-	iog = kmalloc_node(sizeof(*iog), GFP_KERNEL | __GFP_ZERO, q->node);
-	if (iog == NULL)
-		return NULL;
-
-	for (i = 0; i < IO_IOPRIO_CLASSES; i++)
-		iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
-
-	return iog;
-}
-
-void io_free_root_group(struct elevator_queue *e)
-{
-	struct io_group *iog = e->efqd.root_group;
-	io_put_io_group_queues(e, iog);
-	kfree(iog);
-}
-
 static void elv_slab_kill(void)
 {
 	/*
@@ -2081,6 +2890,7 @@ int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e)
 	INIT_WORK(&efqd->unplug_work, elv_kick_queue);
 
 	INIT_LIST_HEAD(&efqd->idle_list);
+	INIT_HLIST_HEAD(&efqd->group_list);
 
 	efqd->elv_slice[0] = elv_slice_async;
 	efqd->elv_slice[1] = elv_slice_sync;
@@ -2110,10 +2920,14 @@ void elv_exit_fq_data(struct elevator_queue *e)
 	spin_lock_irq(q->queue_lock);
 	/* This should drop all the idle tree references of ioq */
 	elv_free_idle_ioq_list(e);
+	/* This should drop all the io group references of async queues */
+	io_disconnect_groups(e);
 	spin_unlock_irq(q->queue_lock);
 
 	elv_shutdown_timer_wq(e);
 
+	/* Wait for iog->key accessors to exit their grace periods. */
+	synchronize_rcu();
 	BUG_ON(timer_pending(&efqd->idle_slice_timer));
 	io_free_root_group(e);
 }
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index ce2d671..1e49f08 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -9,11 +9,13 @@
  */
 
 #include <linux/blkdev.h>
+#include <linux/cgroup.h>
 
 #ifndef _BFQ_SCHED_H
 #define _BFQ_SCHED_H
 
 #define IO_IOPRIO_CLASSES	3
+#define WEIGHT_MAX 		1000
 
 typedef u64 bfq_timestamp_t;
 typedef unsigned long bfq_weight_t;
@@ -69,6 +71,7 @@ struct io_service_tree {
  */
 struct io_sched_data {
 	struct io_entity *active_entity;
+	struct io_entity *next_active;
 	struct io_service_tree service_tree[IO_IOPRIO_CLASSES];
 };
 
@@ -84,13 +87,12 @@ struct io_sched_data {
  *             this entity; used for O(log N) lookups into active trees.
  * @service: service received during the last round of service.
  * @budget: budget used to calculate F_i; F_i = S_i + @budget / @weight.
- * @weight: weight of the queue, calculated as IOPRIO_BE_NR - @ioprio.
  * @parent: parent entity, for hierarchical scheduling.
  * @my_sched_data: for non-leaf nodes in the cgroup hierarchy, the
  *                 associated scheduler queue, %NULL on leaf nodes.
  * @sched_data: the scheduler queue this entity belongs to.
- * @ioprio: the ioprio in use.
- * @new_ioprio: when an ioprio change is requested, the new ioprio value
+ * @weight: the weight in use.
+ * @new_weight: when a weight change is requested, the new weight value
  * @ioprio_class: the ioprio_class in use.
  * @new_ioprio_class: when an ioprio_class change is requested, the new
  *                    ioprio_class value.
@@ -132,13 +134,13 @@ struct io_entity {
 	bfq_timestamp_t min_start;
 
 	bfq_service_t service, budget;
-	bfq_weight_t weight;
 
 	struct io_entity *parent;
 
 	struct io_sched_data *my_sched_data;
 	struct io_sched_data *sched_data;
 
+	bfq_weight_t weight, new_weight;
 	unsigned short ioprio, new_ioprio;
 	unsigned short ioprio_class, new_ioprio_class;
 
@@ -180,6 +182,75 @@ struct io_queue {
 	void *sched_queue;
 };
 
+#ifdef CONFIG_GROUP_IOSCHED
+/**
+ * struct bfq_group - per (device, cgroup) data structure.
+ * @entity: schedulable entity to insert into the parent group sched_data.
+ * @sched_data: own sched_data, to contain child entities (they may be
+ *              both bfq_queues and bfq_groups).
+ * @group_node: node to be inserted into the bfqio_cgroup->group_data
+ *              list of the containing cgroup's bfqio_cgroup.
+ * @bfqd_node: node to be inserted into the @bfqd->group_list list
+ *             of the groups active on the same device; used for cleanup.
+ * @bfqd: the bfq_data for the device this group acts upon.
+ * @async_bfqq: array of async queues for all the tasks belonging to
+ *              the group, one queue per ioprio value per ioprio_class,
+ *              except for the idle class that has only one queue.
+ * @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
+ * @my_entity: pointer to @entity, %NULL for the toplevel group; used
+ *             to avoid too many special cases during group creation/migration.
+ *
+ * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
+ * there is a set of bfq_groups, each one collecting the lower-level
+ * entities belonging to the group that are acting on the same device.
+ *
+ * Locking works as follows:
+ *    o @group_node is protected by the bfqio_cgroup lock, and is accessed
+ *      via RCU from its readers.
+ *    o @bfqd is protected by the queue lock, RCU is used to access it
+ *      from the readers.
+ *    o All the other fields are protected by the @bfqd queue lock.
+ */
+struct io_group {
+	struct io_entity entity;
+	struct hlist_node elv_data_node;
+	struct hlist_node group_node;
+	struct io_sched_data sched_data;
+
+	struct io_entity *my_entity;
+
+	/*
+	 * A cgroup has multiple io_groups, one for each request queue.
+	 * to find io group belonging to a particular queue, elv_fq_data
+	 * pointer is stored as a key.
+	 */
+	void *key;
+
+	/* async_queue and idle_queue are used only for cfq */
+	struct io_queue *async_queue[2][IOPRIO_BE_NR];
+	struct io_queue *async_idle_queue;
+};
+
+/**
+ * struct bfqio_cgroup - bfq cgroup data structure.
+ * @css: subsystem state for bfq in the containing cgroup.
+ * @weight: cgroup weight.
+ * @ioprio_class: cgroup ioprio_class.
+ * @lock: spinlock that protects @weight, @ioprio_class and @group_data.
+ * @group_data: list containing the bfq_group belonging to this cgroup.
+ *
+ * @group_data is accessed using RCU, with @lock protecting the updates,
+ * @weight and @ioprio_class are protected by @lock.
+ */
+struct io_cgroup {
+	struct cgroup_subsys_state css;
+
+	unsigned long weight, ioprio_class;
+
+	spinlock_t lock;
+	struct hlist_head group_data;
+};
+#else
 struct io_group {
 	struct io_sched_data sched_data;
 
@@ -187,10 +258,14 @@ struct io_group {
 	struct io_queue *async_queue[2][IOPRIO_BE_NR];
 	struct io_queue *async_idle_queue;
 };
+#endif
 
 struct elv_fq_data {
 	struct io_group *root_group;
 
+	/* List of io groups hanging on this elevator */
+	struct hlist_head group_list;
+
 	/* List of io queues on idle tree. */
 	struct list_head idle_list;
 
@@ -375,9 +450,20 @@ static inline void elv_ioq_set_ioprio_class(struct io_queue *ioq,
 	ioq->entity.ioprio_changed = 1;
 }
 
+/**
+ * bfq_ioprio_to_weight - calc a weight from an ioprio.
+ * @ioprio: the ioprio value to convert.
+ */
+static inline bfq_weight_t bfq_ioprio_to_weight(int ioprio)
+{
+	WARN_ON(ioprio < 0 || ioprio >= IOPRIO_BE_NR);
+	return ((IOPRIO_BE_NR - ioprio) * WEIGHT_MAX)/IOPRIO_BE_NR;
+}
+
 static inline void elv_ioq_set_ioprio(struct io_queue *ioq, int ioprio)
 {
 	ioq->entity.new_ioprio = ioprio;
+	ioq->entity.new_weight = bfq_ioprio_to_weight(ioprio);
 	ioq->entity.ioprio_changed = 1;
 }
 
@@ -394,6 +480,43 @@ static inline struct io_group *ioq_to_io_group(struct io_queue *ioq)
 						sched_data);
 }
 
+#ifdef CONFIG_GROUP_IOSCHED
+extern int io_group_allow_merge(struct request *rq, struct bio *bio);
+extern void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
+					struct io_group *iog);
+static inline bfq_weight_t iog_weight(struct io_group *iog)
+{
+	return iog->entity.weight;
+}
+
+#else /* !GROUP_IOSCHED */
+/*
+ * No ioq movement is needed in case of flat setup. root io group gets cleaned
+ * up upon elevator exit and before that it has been made sure that both
+ * active and idle tree are empty.
+ */
+static inline void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
+					struct io_group *iog)
+{
+}
+
+static inline int io_group_allow_merge(struct request *rq, struct bio *bio)
+{
+	return 1;
+}
+/*
+ * Currently root group is not part of elevator group list and freed
+ * separately. Hence in case of non-hierarchical setup, nothing todo.
+ */
+static inline void io_disconnect_groups(struct elevator_queue *e) {}
+static inline bfq_weight_t iog_weight(struct io_group *iog)
+{
+	/* Just root group is present and weight is immaterial. */
+	return 0;
+}
+
+#endif /* GROUP_IOSCHED */
+
 /* Functions used by blksysfs.c */
 extern ssize_t elv_slice_idle_show(struct request_queue *q, char *name);
 extern ssize_t elv_slice_idle_store(struct request_queue *q, const char *name,
@@ -430,7 +553,8 @@ extern void elv_put_ioq(struct io_queue *ioq);
 extern void __elv_ioq_slice_expired(struct request_queue *q,
 					struct io_queue *ioq);
 extern int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq,
-		void *sched_queue, int ioprio_class, int ioprio, int is_sync);
+		struct io_group *iog, void *sched_queue, int ioprio_class,
+		int ioprio, int is_sync);
 extern void elv_schedule_dispatch(struct request_queue *q);
 extern int elv_hw_tag(struct elevator_queue *e);
 extern void *elv_active_sched_queue(struct elevator_queue *e);
@@ -442,7 +566,7 @@ extern void *io_group_async_queue_prio(struct io_group *iog, int ioprio_class,
 					int ioprio);
 extern void io_group_set_async_queue(struct io_group *iog, int ioprio_class,
 					int ioprio, struct io_queue *ioq);
-extern struct io_group *io_lookup_io_group_current(struct request_queue *q);
+extern struct io_group *io_get_io_group(struct request_queue *q, int create);
 extern int elv_nr_busy_ioq(struct elevator_queue *e);
 extern int elv_nr_busy_rt_ioq(struct elevator_queue *e);
 extern struct io_queue *elv_alloc_ioq(struct request_queue *q, gfp_t gfp_mask);
@@ -495,5 +619,11 @@ static inline void *elv_fq_select_ioq(struct request_queue *q, int force)
 {
 	return NULL;
 }
+
+static inline int io_group_allow_merge(struct request *rq, struct bio *bio)
+
+{
+	return 1;
+}
 #endif /* CONFIG_ELV_FAIR_QUEUING */
 #endif /* _BFQ_SCHED_H */
diff --git a/block/elevator.c b/block/elevator.c
index c2f07f5..3944385 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -105,6 +105,10 @@ int elv_rq_merge_ok(struct request *rq, struct bio *bio)
 	if (bio_integrity(bio) != blk_integrity_rq(rq))
 		return 0;
 
+	/* If rq and bio belongs to different groups, dont allow merging */
+	if (!io_group_allow_merge(rq, bio))
+		return 0;
+
 	if (!elv_iosched_allow_merge(rq, bio))
 		return 0;
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 96a94c9..539cb9d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -249,7 +249,7 @@ struct request {
 #ifdef CONFIG_ELV_FAIR_QUEUING
 	/* io queue request belongs to */
 	struct io_queue *ioq;
-#endif
+#endif /* ELV_FAIR_QUEUING */
 };
 
 static inline unsigned short req_get_ioprio(struct request *req)
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index 9c8d31b..68ea6bd 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -60,3 +60,10 @@ SUBSYS(net_cls)
 #endif
 
 /* */
+
+#ifdef CONFIG_GROUP_IOSCHED
+SUBSYS(io)
+#endif
+
+/* */
+
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 0a2815d..271187f 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -69,6 +69,11 @@ struct io_context {
 	unsigned short ioprio;
 	unsigned short ioprio_changed;
 
+#ifdef CONFIG_GROUP_IOSCHED
+	/* If task changes the cgroup, elevator processes it asynchronously */
+	unsigned short cgroup_changed;
+#endif
+
 	/*
 	 * For request batching
 	 */
diff --git a/init/Kconfig b/init/Kconfig
index 7be4d38..ab76477 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -606,6 +606,14 @@ config CGROUP_MEM_RES_CTLR_SWAP
 	  Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 	  size is 4096bytes, 512k per 1Gbytes of swap.
 
+config GROUP_IOSCHED
+	bool "Group IO Scheduler"
+	depends on CGROUPS && ELV_FAIR_QUEUING
+	default n
+	---help---
+	  This feature lets IO scheduler recognize task groups and control
+	  disk bandwidth allocation to such task groups.
+
 endif # CGROUPS
 
 config MM_OWNER
-- 
1.6.0.1

[PATCH 06/20] io-controller: cfq changes to use hierarchical fair queuing code in elevaotor layer

[Vivek Goyal]

Make cfq hierarhical.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Fabio Checconi <fabio-f9ZlEuEWxVeACYmtYXMKmw@public.gmane.org>
Signed-off-by: Paolo Valente <paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org>
Signed-off-by: Aristeu Rozanski <aris-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/Kconfig.iosched |    8 ++++++
 block/cfq-iosched.c   |   58 ++++++++++++++++++++++++++++++++++++++++++++++--
 init/Kconfig          |    2 +-
 3 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index dd5224d..a91a807 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -54,6 +54,14 @@ config IOSCHED_CFQ
 	  working environment, suitable for desktop systems.
 	  This is the default I/O scheduler.
 
+config IOSCHED_CFQ_HIER
+	bool "CFQ Hierarchical Scheduling support"
+	depends on IOSCHED_CFQ && CGROUPS
+	select GROUP_IOSCHED
+	default n
+	---help---
+	  Enable hierarhical scheduling in cfq.
+
 choice
 	prompt "Default I/O scheduler"
 	default DEFAULT_CFQ
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f90c534..f00110e 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1229,6 +1229,50 @@ static void cfq_ioc_set_ioprio(struct io_context *ioc)
 	ioc->ioprio_changed = 0;
 }
 
+#ifdef CONFIG_IOSCHED_CFQ_HIER
+static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
+{
+	struct cfq_queue *async_cfqq = cic_to_cfqq(cic, 0);
+	struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
+	struct cfq_data *cfqd = cic->key;
+	struct io_group *iog, *__iog;
+	unsigned long flags;
+	struct request_queue *q;
+
+	if (unlikely(!cfqd))
+		return;
+
+	q = cfqd->queue;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+
+	iog = io_get_io_group(q, 0);
+
+	if (async_cfqq != NULL) {
+		__iog = cfqq_to_io_group(async_cfqq);
+
+		if (iog != __iog) {
+			cic_set_cfqq(cic, NULL, 0);
+			cfq_put_queue(async_cfqq);
+		}
+	}
+
+	if (sync_cfqq != NULL) {
+		__iog = cfqq_to_io_group(sync_cfqq);
+		if (iog != __iog)
+			io_ioq_move(q->elevator, sync_cfqq->ioq, iog);
+	}
+
+	spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+static void cfq_ioc_set_cgroup(struct io_context *ioc)
+{
+	call_for_each_cic(ioc, changed_cgroup);
+	ioc->cgroup_changed = 0;
+}
+#endif  /* CONFIG_IOSCHED_CFQ_HIER */
+
 static struct cfq_queue *
 cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
 				struct io_context *ioc, gfp_t gfp_mask)
@@ -1237,7 +1281,10 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
 	struct cfq_io_context *cic;
 	struct request_queue *q = cfqd->queue;
 	struct io_queue *ioq = NULL, *new_ioq = NULL;
+	struct io_group *iog = NULL;
 retry:
+	iog = io_get_io_group(q, 1);
+
 	cic = cfq_cic_lookup(cfqd, ioc);
 	/* cic always exists here */
 	cfqq = cic_to_cfqq(cic, is_sync);
@@ -1304,8 +1351,9 @@ alloc_ioq:
 
 		cfqq->ioq = ioq;
 		cfq_init_prio_data(cfqq, ioc);
-		elv_init_ioq(q->elevator, ioq, cfqq, cfqq->org_ioprio_class,
-				cfqq->org_ioprio, is_sync);
+		elv_init_ioq(q->elevator, ioq, iog, cfqq,
+				cfqq->org_ioprio_class, cfqq->org_ioprio,
+				is_sync);
 
 		if (is_sync) {
 			if (!cfq_class_idle(cfqq))
@@ -1335,7 +1383,7 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
 	const int ioprio_class = task_ioprio_class(ioc);
 	struct cfq_queue *async_cfqq = NULL;
 	struct cfq_queue *cfqq = NULL;
-	struct io_group *iog = io_lookup_io_group_current(cfqd->queue);
+	struct io_group *iog = io_get_io_group(cfqd->queue, 1);
 
 	if (!is_sync) {
 		async_cfqq = io_group_async_queue_prio(iog, ioprio_class,
@@ -1494,6 +1542,10 @@ out:
 	smp_read_barrier_depends();
 	if (unlikely(ioc->ioprio_changed))
 		cfq_ioc_set_ioprio(ioc);
+#ifdef CONFIG_IOSCHED_CFQ_HIER
+	if (unlikely(ioc->cgroup_changed))
+		cfq_ioc_set_cgroup(ioc);
+#endif
 	return cic;
 err_free:
 	cfq_cic_free(cic);
diff --git a/init/Kconfig b/init/Kconfig
index ab76477..1a4686d 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -607,7 +607,7 @@ config CGROUP_MEM_RES_CTLR_SWAP
 	  size is 4096bytes, 512k per 1Gbytes of swap.
 
 config GROUP_IOSCHED
-	bool "Group IO Scheduler"
+	bool
 	depends on CGROUPS && ELV_FAIR_QUEUING
 	default n
 	---help---
-- 
1.6.0.1

[PATCH 07/20] io-controller: Export disk time used and nr sectors dipatched through cgroups

[Vivek Goyal]

o This patch exports some statistics through cgroup interface. Two of the
  statistics currently exported are actual disk time assigned to the cgroup
  and actual number of sectors dispatched to disk on behalf of this cgroup.

Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/elevator-fq.c |   89 +++++++++++++++++++++++++++++++++++++++++++++++---
 block/elevator-fq.h |   11 ++++++
 2 files changed, 94 insertions(+), 6 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 2ba6e92..0a99047 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -11,6 +11,7 @@
 #include <linux/blkdev.h>
 #include "elevator-fq.h"
 #include <linux/blktrace_api.h>
+#include <linux/seq_file.h>
 
 /* Values taken from cfq */
 const int elv_slice_sync = HZ / 10;
@@ -884,13 +885,16 @@ struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
 	return entity;
 }
 
-void entity_served(struct io_entity *entity, bfq_service_t served)
+void entity_served(struct io_entity *entity, bfq_service_t served,
+					bfq_service_t nr_sectors)
 {
 	struct io_service_tree *st;
 
 	for_each_entity(entity) {
 		st = io_entity_service_tree(entity);
 		entity->service += served;
+		entity->total_service += served;
+		entity->total_sector_service += nr_sectors;
 		BUG_ON(st->wsum == 0);
 		st->vtime += bfq_delta(served, st->wsum);
 		bfq_forget_idle(st);
@@ -1048,6 +1052,66 @@ STORE_FUNCTION(weight, 1, WEIGHT_MAX);
 STORE_FUNCTION(ioprio_class, IOPRIO_CLASS_RT, IOPRIO_CLASS_IDLE);
 #undef STORE_FUNCTION
 
+static int io_cgroup_disk_time_read(struct cgroup *cgroup,
+				struct cftype *cftype, struct seq_file *m)
+{
+	struct io_cgroup *iocg;
+	struct io_group *iog;
+	struct hlist_node *n;
+
+	if (!cgroup_lock_live_group(cgroup))
+		return -ENODEV;
+
+	iocg = cgroup_to_io_cgroup(cgroup);
+
+	spin_lock_irq(&iocg->lock);
+	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
+		/*
+		 * There might be groups which are not functional and
+		 * waiting to be reclaimed upon cgoup deletion.
+		 */
+		if (iog->key) {
+			seq_printf(m, "%u %u %lu\n", MAJOR(iog->dev),
+					MINOR(iog->dev),
+					iog->entity.total_service);
+		}
+	}
+	spin_unlock_irq(&iocg->lock);
+	cgroup_unlock();
+
+	return 0;
+}
+
+static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,
+				struct cftype *cftype, struct seq_file *m)
+{
+	struct io_cgroup *iocg;
+	struct io_group *iog;
+	struct hlist_node *n;
+
+	if (!cgroup_lock_live_group(cgroup))
+		return -ENODEV;
+
+	iocg = cgroup_to_io_cgroup(cgroup);
+
+	spin_lock_irq(&iocg->lock);
+	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
+		/*
+		 * There might be groups which are not functional and
+		 * waiting to be reclaimed upon cgoup deletion.
+		 */
+		if (iog->key) {
+			seq_printf(m, "%u %u %lu\n", MAJOR(iog->dev),
+					MINOR(iog->dev),
+					iog->entity.total_sector_service);
+		}
+	}
+	spin_unlock_irq(&iocg->lock);
+	cgroup_unlock();
+
+	return 0;
+}
+
 /**
  * bfq_group_chain_alloc - allocate a chain of groups.
  * @bfqd: queue descriptor.
@@ -1058,7 +1122,7 @@ STORE_FUNCTION(ioprio_class, IOPRIO_CLASS_RT, IOPRIO_CLASS_IDLE);
  * to the root has already an allocated group on @bfqd.
  */
 struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
-					struct cgroup *cgroup)
+					struct cgroup *cgroup, struct bio *bio)
 {
 	struct io_cgroup *iocg;
 	struct io_group *iog, *leaf = NULL, *prev = NULL;
@@ -1084,6 +1148,11 @@ struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
 		io_group_init_entity(iocg, iog);
 		iog->my_entity = &iog->entity;
 
+		if (bio) {
+			struct gendisk *disk = bio->bi_bdev->bd_disk;
+			iog->dev = MKDEV(disk->major, disk->first_minor);
+		}
+
 		if (leaf == NULL) {
 			leaf = iog;
 			prev = leaf;
@@ -1187,7 +1256,7 @@ void io_group_chain_link(struct request_queue *q, void *key,
  */
 struct io_group *io_find_alloc_group(struct request_queue *q,
 			struct cgroup *cgroup, struct elv_fq_data *efqd,
-			int create)
+			int create, struct bio *bio)
 {
 	struct io_cgroup *iocg = cgroup_to_io_cgroup(cgroup);
 	struct io_group *iog = NULL;
@@ -1198,7 +1267,7 @@ struct io_group *io_find_alloc_group(struct request_queue *q,
 	if (iog != NULL || !create)
 		return iog;
 
-	iog = io_group_chain_alloc(q, key, cgroup);
+	iog = io_group_chain_alloc(q, key, cgroup, bio);
 	if (iog != NULL)
 		io_group_chain_link(q, key, cgroup, iog, efqd);
 
@@ -1217,7 +1286,7 @@ struct io_group *io_get_io_group(struct request_queue *q, int create)
 
 	rcu_read_lock();
 	cgroup = task_cgroup(current, io_subsys_id);
-	iog = io_find_alloc_group(q, cgroup, efqd, create);
+	iog = io_find_alloc_group(q, cgroup, efqd, create, NULL);
 	if (!iog) {
 		if (create)
 			iog = efqd->root_group;
@@ -1282,6 +1351,14 @@ struct cftype bfqio_files[] = {
 		.read_u64 = io_cgroup_ioprio_class_read,
 		.write_u64 = io_cgroup_ioprio_class_write,
 	},
+	{
+		.name = "disk_time",
+		.read_seq_string = io_cgroup_disk_time_read,
+	},
+	{
+		.name = "disk_sectors",
+		.read_seq_string = io_cgroup_disk_sectors_read,
+	},
 };
 
 int iocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
@@ -1670,7 +1747,7 @@ EXPORT_SYMBOL(elv_get_slice_idle);
 
 void elv_ioq_served(struct io_queue *ioq, bfq_service_t served)
 {
-	entity_served(&ioq->entity, served);
+	entity_served(&ioq->entity, served, ioq->nr_sectors);
 }
 
 /* Tells whether ioq is queued in root group or not */
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 1e49f08..3dbcf73 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -145,6 +145,13 @@ struct io_entity {
 	unsigned short ioprio_class, new_ioprio_class;
 
 	int ioprio_changed;
+
+	/*
+	 * Keep track of total service received by this entity. Keep the
+	 * stats both for time slices and number of sectors dispatched
+	 */
+	unsigned long total_service;
+	unsigned long total_sector_service;
 };
 
 /*
@@ -229,6 +236,10 @@ struct io_group {
 	/* async_queue and idle_queue are used only for cfq */
 	struct io_queue *async_queue[2][IOPRIO_BE_NR];
 	struct io_queue *async_idle_queue;
+
+	/* The device MKDEV(major, minor), this group has been created for */
+	dev_t	dev;
+
 };
 
 /**
-- 
1.6.0.1

[PATCH 08/20] io-controller: idle for sometime on sync queue before expiring it

[Vivek Goyal]

o When a sync queue expires, in many cases it might be empty and then
  it will be deleted from the active tree. This will lead to a scenario
  where out of two competing queues, only one is on the tree and when a
  new queue is selected, vtime jump takes place and we don't see services
  provided in proportion to weight.

o In general this is a fundamental problem with fairness of sync queues
  where queues are not continuously backlogged. Looks like idling is
  only solution to make sure such kind of queues can get some decent amount
  of disk bandwidth in the face of competion from continusouly backlogged
  queues. But excessive idling has potential to reduce performance on SSD
  and disks with commnad queuing.

o This patch experiments with waiting for next request to come before a
  queue is expired after it has consumed its time slice. This can ensure
  more accurate fairness numbers in some cases.

o Introduced a tunable "fairness". If set, io-controller will put more
  focus on getting fairness right than getting throughput right.

Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/blk-sysfs.c   |    7 ++
 block/elevator-fq.c |  165 ++++++++++++++++++++++++++++++++++++++++++++++-----
 block/elevator-fq.h |   15 +++++
 3 files changed, 171 insertions(+), 16 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 082a273..c942ddc 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -294,6 +294,12 @@ static struct queue_sysfs_entry queue_slice_async_entry = {
 	.show = elv_slice_async_show,
 	.store = elv_slice_async_store,
 };
+
+static struct queue_sysfs_entry queue_fairness_entry = {
+	.attr = {.name = "fairness", .mode = S_IRUGO | S_IWUSR },
+	.show = elv_fairness_show,
+	.store = elv_fairness_store,
+};
 #endif
 
 static struct attribute *default_attrs[] = {
@@ -311,6 +317,7 @@ static struct attribute *default_attrs[] = {
 	&queue_slice_idle_entry.attr,
 	&queue_slice_sync_entry.attr,
 	&queue_slice_async_entry.attr,
+	&queue_fairness_entry.attr,
 #endif
 	NULL,
 };
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 0a99047..201785e 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -359,6 +359,7 @@ static void bfq_active_insert(struct io_service_tree *st,
 	struct rb_node *node = &entity->rb_node;
 
 	bfq_insert(&st->active, entity);
+	entity->sched_data->nr_active++;
 	if (node->rb_left != NULL)
 		node = node->rb_left;
 	else if (node->rb_right != NULL)
@@ -417,6 +418,7 @@ static void bfq_active_extract(struct io_service_tree *st,
 
 	node = bfq_find_deepest(&entity->rb_node);
 	bfq_extract(&st->active, entity);
+	entity->sched_data->nr_active--;
 	if (node != NULL)
 		bfq_update_active_tree(node);
 }
@@ -916,6 +918,21 @@ void io_put_io_group_queues(struct elevator_queue *e, struct io_group *iog)
 	elv_release_ioq(e, &iog->async_idle_queue);
 }
 
+/*
+ * Returns the number of active entities a particular io group has. This
+ * includes number of active entities on service tree as well as the active
+ * entity which is being served currently, if any.
+ */
+
+static inline int elv_iog_nr_active(struct io_group *iog)
+{
+	struct io_sched_data *sd = &iog->sched_data;
+
+	if (sd->active_entity)
+		return sd->nr_active + 1;
+	else
+		return sd->nr_active;
+}
 
 /* Mainly hierarchical grouping code */
 #ifdef CONFIG_GROUP_IOSCHED
@@ -1759,6 +1776,44 @@ static inline int is_root_group_ioq(struct request_queue *q,
 	return (ioq->entity.sched_data == &efqd->root_group->sched_data);
 }
 
+/* Functions to show and store fairness value through sysfs */
+ssize_t elv_fairness_show(struct request_queue *q, char *name)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	data = efqd->fairness;
+	spin_unlock_irqrestore(q->queue_lock, flags);
+	return sprintf(name, "%d\n", data);
+}
+
+ssize_t elv_fairness_store(struct request_queue *q, const char *name,
+			  size_t count)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	char *p = (char *)name;
+
+	data = simple_strtoul(p, &p, 10);
+
+	if (data < 0)
+		data = 0;
+	else if (data > INT_MAX)
+		data = INT_MAX;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	efqd->fairness = data;
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	return count;
+}
+
 /* Functions to show and store elv_idle_slice value through sysfs */
 ssize_t elv_slice_idle_show(struct request_queue *q, char *name)
 {
@@ -1999,7 +2054,7 @@ static void elv_ioq_update_idle_window(struct elevator_queue *eq,
 	 * io scheduler if it wants to disable idling based on additional
 	 * considrations like seek pattern.
 	 */
-	if (enable_idle) {
+	if (enable_idle && !efqd->fairness) {
 		if (eq->ops->elevator_update_idle_window_fn)
 			enable_idle = eq->ops->elevator_update_idle_window_fn(
 						eq, ioq->sched_queue, rq);
@@ -2181,6 +2236,7 @@ static void __elv_set_active_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
 
 		elv_clear_ioq_wait_request(ioq);
 		elv_clear_ioq_must_dispatch(ioq);
+		elv_clear_ioq_wait_busy_done(ioq);
 		elv_mark_ioq_slice_new(ioq);
 
 		del_timer(&efqd->idle_slice_timer);
@@ -2332,10 +2388,12 @@ void __elv_ioq_slice_expired(struct request_queue *q, struct io_queue *ioq)
 	assert_spin_locked(q->queue_lock);
 	elv_log_ioq(efqd, ioq, "slice expired");
 
-	if (elv_ioq_wait_request(ioq))
+	if (elv_ioq_wait_request(ioq) || elv_ioq_wait_busy(ioq))
 		del_timer(&efqd->idle_slice_timer);
 
 	elv_clear_ioq_wait_request(ioq);
+	elv_clear_ioq_wait_busy(ioq);
+	elv_clear_ioq_wait_busy_done(ioq);
 
 	/*
 	 * if ioq->slice_end = 0, that means a queue was expired before first
@@ -2500,7 +2558,7 @@ void elv_ioq_request_add(struct request_queue *q, struct request *rq)
 		 * has other work pending, don't risk delaying until the
 		 * idle timer unplug to continue working.
 		 */
-		if (elv_ioq_wait_request(ioq)) {
+		if (elv_ioq_wait_request(ioq) && !elv_ioq_wait_busy(ioq)) {
 			if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
 			    efqd->busy_queues > 1) {
 				del_timer(&efqd->idle_slice_timer);
@@ -2508,6 +2566,18 @@ void elv_ioq_request_add(struct request_queue *q, struct request *rq)
 			}
 			elv_mark_ioq_must_dispatch(ioq);
 		}
+
+		/*
+		 * If we were waiting for a request on this queue, wait is
+		 * done. Schedule the next dispatch
+		 */
+		if (elv_ioq_wait_busy(ioq)) {
+			del_timer(&efqd->idle_slice_timer);
+			elv_clear_ioq_wait_busy(ioq);
+			elv_mark_ioq_wait_busy_done(ioq);
+			elv_clear_ioq_must_dispatch(ioq);
+			elv_schedule_dispatch(q);
+		}
 	} else if (elv_should_preempt(q, ioq, rq)) {
 		/*
 		 * not the active queue - expire current slice if it is
@@ -2535,6 +2605,9 @@ void elv_idle_slice_timer(unsigned long data)
 
 	if (ioq) {
 
+		if (elv_ioq_wait_busy(ioq))
+			goto expire;
+
 		/*
 		 * We saw a request before the queue expired, let it through
 		 */
@@ -2568,7 +2641,7 @@ out_cont:
 	spin_unlock_irqrestore(q->queue_lock, flags);
 }
 
-void elv_ioq_arm_slice_timer(struct request_queue *q)
+void elv_ioq_arm_slice_timer(struct request_queue *q, int wait_for_busy)
 {
 	struct elv_fq_data *efqd = &q->elevator->efqd;
 	struct io_queue *ioq = elv_active_ioq(q->elevator);
@@ -2581,26 +2654,38 @@ void elv_ioq_arm_slice_timer(struct request_queue *q)
 	 * for devices that support queuing, otherwise we still have a problem
 	 * with sync vs async workloads.
 	 */
-	if (blk_queue_nonrot(q) && efqd->hw_tag)
+	if (blk_queue_nonrot(q) && efqd->hw_tag && !efqd->fairness)
 		return;
 
 	/*
-	 * still requests with the driver, don't idle
+	 * idle is disabled, either manually or by past process history
 	 */
-	if (efqd->rq_in_driver)
+	if (!efqd->elv_slice_idle || !elv_ioq_idle_window(ioq))
 		return;
 
 	/*
-	 * idle is disabled, either manually or by past process history
+	 * This queue has consumed its time slice. We are waiting only for
+	 * it to become busy before we select next queue for dispatch.
 	 */
-	if (!efqd->elv_slice_idle || !elv_ioq_idle_window(ioq))
+	if (wait_for_busy) {
+		elv_mark_ioq_wait_busy(ioq);
+		sl = efqd->elv_slice_idle;
+		mod_timer(&efqd->idle_slice_timer, jiffies + sl);
+		elv_log_ioq(efqd, ioq, "arm idle: %lu wait busy=1", sl);
+		return;
+	}
+
+	/*
+	 * still requests with the driver, don't idle
+	 */
+	if (efqd->rq_in_driver && !efqd->fairness)
 		return;
 
 	/*
 	 * may be iosched got its own idling logic. In that case io
 	 * schduler will take care of arming the timer, if need be.
 	 */
-	if (q->elevator->ops->elevator_arm_slice_timer_fn) {
+	if (q->elevator->ops->elevator_arm_slice_timer_fn && !efqd->fairness) {
 		q->elevator->ops->elevator_arm_slice_timer_fn(q,
 						ioq->sched_queue);
 	} else {
@@ -2643,11 +2728,38 @@ void *elv_fq_select_ioq(struct request_queue *q, int force)
 			goto expire;
 	}
 
+	/* We are waiting for this queue to become busy before it expires.*/
+	if (efqd->fairness && elv_ioq_wait_busy(ioq)) {
+		ioq = NULL;
+		goto keep_queue;
+	}
+
 	/*
 	 * The active queue has run out of time, expire it and select new.
 	 */
-	if (elv_ioq_slice_used(ioq) && !elv_ioq_must_dispatch(ioq))
-		goto expire;
+	if (elv_ioq_slice_used(ioq) && !elv_ioq_must_dispatch(ioq)) {
+		/*
+		 * Queue has used up its slice. Wait busy is not on otherwise
+		 * we wouldn't have been here. There is a chance that after
+		 * slice expiry no request from the queue completed hence
+		 * wait busy timer could not be turned on. If that's the case
+		 * don't expire the queue yet. Next request completion from
+		 * the queue will arm the wait busy timer.
+		 *
+		 * Don't wait if this group has other active queues. This
+		 * will make sure that we don't loose fairness at group level
+		 * at the same time in root group we will not see cfq
+		 * regressions.
+		 */
+		if (elv_ioq_sync(ioq) && !ioq->nr_queued
+		    && elv_ioq_nr_dispatched(ioq)
+		    && (elv_iog_nr_active(ioq_to_io_group(ioq)) <= 1)
+		    && !elv_ioq_wait_busy_done(ioq)) {
+			ioq = NULL;
+			goto keep_queue;
+		} else
+			goto expire;
+	}
 
 	/*
 	 * If we have a RT cfqq waiting, then we pre-empt the current non-rt
@@ -2824,11 +2936,13 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
 	const int sync = rq_is_sync(rq);
 	struct io_queue *ioq;
 	struct elv_fq_data *efqd = &q->elevator->efqd;
+	struct io_group *iog;
 
 	if (!elv_iosched_fair_queuing_enabled(q->elevator))
 		return;
 
 	ioq = rq->ioq;
+	iog = ioq_to_io_group(ioq);
 
 	elv_log_ioq(efqd, ioq, "complete");
 
@@ -2854,6 +2968,12 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
 			elv_ioq_set_prio_slice(q, ioq);
 			elv_clear_ioq_slice_new(ioq);
 		}
+
+		if (elv_ioq_class_idle(ioq)) {
+			elv_ioq_slice_expired(q);
+			goto done;
+		}
+
 		/*
 		 * If there are no requests waiting in this queue, and
 		 * there are other queues ready to issue requests, AND
@@ -2861,13 +2981,24 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
 		 * mean seek distance, give them a chance to run instead
 		 * of idling.
 		 */
-		if (elv_ioq_slice_used(ioq) || elv_ioq_class_idle(ioq))
-			elv_ioq_slice_expired(q);
-		else if (!ioq->nr_queued && !elv_close_cooperator(q, ioq, 1)
+		if (elv_ioq_slice_used(ioq)) {
+			if (sync && !ioq->nr_queued
+			    && (elv_iog_nr_active(iog) <= 1)) {
+				/*
+				 * Idle for one extra period in hierarchical
+				 * setup
+				 */
+				elv_ioq_arm_slice_timer(q, 1);
+			} else {
+				/* Expire the queue */
+				elv_ioq_slice_expired(q);
+			}
+		} else if (!ioq->nr_queued && !elv_close_cooperator(q, ioq, 1)
 			 && sync && !rq_noidle(rq))
-			elv_ioq_arm_slice_timer(q);
+			elv_ioq_arm_slice_timer(q, 0);
 	}
 
+done:
 	if (!efqd->rq_in_driver)
 		elv_schedule_dispatch(q);
 }
@@ -2974,6 +3105,8 @@ int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e)
 	efqd->elv_slice_idle = elv_slice_idle;
 	efqd->hw_tag = 1;
 
+	/* For the time being keep fairness enabled by default */
+	efqd->fairness = 1;
 	return 0;
 }
 
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 3dbcf73..4f11be3 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -72,6 +72,7 @@ struct io_service_tree {
 struct io_sched_data {
 	struct io_entity *active_entity;
 	struct io_entity *next_active;
+	int nr_active;
 	struct io_service_tree service_tree[IO_IOPRIO_CLASSES];
 };
 
@@ -320,6 +321,13 @@ struct elv_fq_data {
 	unsigned long long rate_sampling_start; /*sampling window start jifies*/
 	/* number of sectors finished io during current sampling window */
 	unsigned long rate_sectors_current;
+
+	/*
+	 * If set to 1, will disable many optimizations done for boost
+	 * throughput and focus more on providing fairness for sync
+	 * queues.
+	 */
+	int fairness;
 };
 
 extern int elv_slice_idle;
@@ -344,6 +352,8 @@ enum elv_queue_state_flags {
 	ELV_QUEUE_FLAG_wait_request,	  /* waiting for a request */
 	ELV_QUEUE_FLAG_must_dispatch,	  /* must be allowed a dispatch */
 	ELV_QUEUE_FLAG_slice_new,	  /* no requests dispatched in slice */
+	ELV_QUEUE_FLAG_wait_busy,	  /* wait for this queue to get busy */
+	ELV_QUEUE_FLAG_wait_busy_done,	  /* Have already waited on this queue*/
 	ELV_QUEUE_FLAG_NR,
 };
 
@@ -367,6 +377,8 @@ ELV_IO_QUEUE_FLAG_FNS(wait_request)
 ELV_IO_QUEUE_FLAG_FNS(must_dispatch)
 ELV_IO_QUEUE_FLAG_FNS(idle_window)
 ELV_IO_QUEUE_FLAG_FNS(slice_new)
+ELV_IO_QUEUE_FLAG_FNS(wait_busy)
+ELV_IO_QUEUE_FLAG_FNS(wait_busy_done)
 
 static inline struct io_service_tree *
 io_entity_service_tree(struct io_entity *entity)
@@ -538,6 +550,9 @@ extern ssize_t elv_slice_sync_store(struct request_queue *q, const char *name,
 extern ssize_t elv_slice_async_show(struct request_queue *q, char *name);
 extern ssize_t elv_slice_async_store(struct request_queue *q, const char *name,
 						size_t count);
+extern ssize_t elv_fairness_show(struct request_queue *q, char *name);
+extern ssize_t elv_fairness_store(struct request_queue *q, const char *name,
+						size_t count);
 
 /* Functions used by elevator.c */
 extern int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e);
-- 
1.6.0.1

[PATCH 09/20] io-controller: Separate out queue and data

[Vivek Goyal]

o So far noop, deadline and AS had one common structure called *_data which
  contained both the queue information where requests are queued and also
  common data used for scheduling. This patch breaks down this common
  structure in two parts, *_queue and *_data. This is along the lines of
  cfq where all the reuquests are queued in queue and common data and tunables
  are part of data.

o It does not change the functionality but this re-organization helps once
  noop, deadline and AS are changed to use hierarchical fair queuing.

o looks like queue_empty function is not required and we can check for
  q->nr_sorted in elevator layer to see if ioscheduler queues are empty or
  not.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/as-iosched.c       |  208 ++++++++++++++++++++++++++--------------------
 block/deadline-iosched.c |  117 ++++++++++++++++----------
 block/elevator.c         |  111 +++++++++++++++++++++----
 block/noop-iosched.c     |   59 ++++++-------
 include/linux/elevator.h |    8 ++-
 5 files changed, 319 insertions(+), 184 deletions(-)

diff --git a/block/as-iosched.c b/block/as-iosched.c
index c48fa67..7158e13 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -76,13 +76,7 @@ enum anticipation_status {
 				 * or timed out */
 };
 
-struct as_data {
-	/*
-	 * run time data
-	 */
-
-	struct request_queue *q;	/* the "owner" queue */
-
+struct as_queue {
 	/*
 	 * requests (as_rq s) are present on both sort_list and fifo_list
 	 */
@@ -90,6 +84,14 @@ struct as_data {
 	struct list_head fifo_list[2];
 
 	struct request *next_rq[2];	/* next in sort order */
+	unsigned long last_check_fifo[2];
+	int write_batch_count;		/* max # of reqs in a write batch */
+	int current_write_count;	/* how many requests left this batch */
+	int write_batch_idled;		/* has the write batch gone idle? */
+};
+
+struct as_data {
+	struct request_queue *q;	/* the "owner" queue */
 	sector_t last_sector[2];	/* last SYNC & ASYNC sectors */
 
 	unsigned long exit_prob;	/* probability a task will exit while
@@ -103,21 +105,17 @@ struct as_data {
 	sector_t new_seek_mean;
 
 	unsigned long current_batch_expires;
-	unsigned long last_check_fifo[2];
 	int changed_batch;		/* 1: waiting for old batch to end */
 	int new_batch;			/* 1: waiting on first read complete */
-	int batch_data_dir;		/* current batch SYNC / ASYNC */
-	int write_batch_count;		/* max # of reqs in a write batch */
-	int current_write_count;	/* how many requests left this batch */
-	int write_batch_idled;		/* has the write batch gone idle? */
 
 	enum anticipation_status antic_status;
 	unsigned long antic_start;	/* jiffies: when it started */
 	struct timer_list antic_timer;	/* anticipatory scheduling timer */
-	struct work_struct antic_work;	/* Deferred unplugging */
+	struct work_struct antic_work;  /* Deferred unplugging */
 	struct io_context *io_context;	/* Identify the expected process */
 	int ioc_finished; /* IO associated with io_context is finished */
 	int nr_dispatched;
+	int batch_data_dir;		/* current batch SYNC / ASYNC */
 
 	/*
 	 * settings that change how the i/o scheduler behaves
@@ -258,13 +256,14 @@ static void as_put_io_context(struct request *rq)
 /*
  * rb tree support functions
  */
-#define RQ_RB_ROOT(ad, rq)	(&(ad)->sort_list[rq_is_sync((rq))])
+#define RQ_RB_ROOT(asq, rq)	(&(asq)->sort_list[rq_is_sync((rq))])
 
 static void as_add_rq_rb(struct as_data *ad, struct request *rq)
 {
 	struct request *alias;
+	struct as_queue *asq = elv_get_sched_queue(ad->q, rq);
 
-	while ((unlikely(alias = elv_rb_add(RQ_RB_ROOT(ad, rq), rq)))) {
+	while ((unlikely(alias = elv_rb_add(RQ_RB_ROOT(asq, rq), rq)))) {
 		as_move_to_dispatch(ad, alias);
 		as_antic_stop(ad);
 	}
@@ -272,7 +271,9 @@ static void as_add_rq_rb(struct as_data *ad, struct request *rq)
 
 static inline void as_del_rq_rb(struct as_data *ad, struct request *rq)
 {
-	elv_rb_del(RQ_RB_ROOT(ad, rq), rq);
+	struct as_queue *asq = elv_get_sched_queue(ad->q, rq);
+
+	elv_rb_del(RQ_RB_ROOT(asq, rq), rq);
 }
 
 /*
@@ -366,7 +367,7 @@ as_choose_req(struct as_data *ad, struct request *rq1, struct request *rq2)
  * what request to process next. Anticipation works on top of this.
  */
 static struct request *
-as_find_next_rq(struct as_data *ad, struct request *last)
+as_find_next_rq(struct as_data *ad, struct as_queue *asq, struct request *last)
 {
 	struct rb_node *rbnext = rb_next(&last->rb_node);
 	struct rb_node *rbprev = rb_prev(&last->rb_node);
@@ -382,7 +383,7 @@ as_find_next_rq(struct as_data *ad, struct request *last)
 	else {
 		const int data_dir = rq_is_sync(last);
 
-		rbnext = rb_first(&ad->sort_list[data_dir]);
+		rbnext = rb_first(&asq->sort_list[data_dir]);
 		if (rbnext && rbnext != &last->rb_node)
 			next = rb_entry_rq(rbnext);
 	}
@@ -787,9 +788,10 @@ static int as_can_anticipate(struct as_data *ad, struct request *rq)
 static void as_update_rq(struct as_data *ad, struct request *rq)
 {
 	const int data_dir = rq_is_sync(rq);
+	struct as_queue *asq = elv_get_sched_queue(ad->q, rq);
 
 	/* keep the next_rq cache up to date */
-	ad->next_rq[data_dir] = as_choose_req(ad, rq, ad->next_rq[data_dir]);
+	asq->next_rq[data_dir] = as_choose_req(ad, rq, asq->next_rq[data_dir]);
 
 	/*
 	 * have we been anticipating this request?
@@ -810,25 +812,26 @@ static void update_write_batch(struct as_data *ad)
 {
 	unsigned long batch = ad->batch_expire[BLK_RW_ASYNC];
 	long write_time;
+	struct as_queue *asq = elv_get_sched_queue(ad->q, NULL);
 
 	write_time = (jiffies - ad->current_batch_expires) + batch;
 	if (write_time < 0)
 		write_time = 0;
 
-	if (write_time > batch && !ad->write_batch_idled) {
+	if (write_time > batch && !asq->write_batch_idled) {
 		if (write_time > batch * 3)
-			ad->write_batch_count /= 2;
+			asq->write_batch_count /= 2;
 		else
-			ad->write_batch_count--;
-	} else if (write_time < batch && ad->current_write_count == 0) {
+			asq->write_batch_count--;
+	} else if (write_time < batch && asq->current_write_count == 0) {
 		if (batch > write_time * 3)
-			ad->write_batch_count *= 2;
+			asq->write_batch_count *= 2;
 		else
-			ad->write_batch_count++;
+			asq->write_batch_count++;
 	}
 
-	if (ad->write_batch_count < 1)
-		ad->write_batch_count = 1;
+	if (asq->write_batch_count < 1)
+		asq->write_batch_count = 1;
 }
 
 /*
@@ -899,6 +902,7 @@ static void as_remove_queued_request(struct request_queue *q,
 	const int data_dir = rq_is_sync(rq);
 	struct as_data *ad = q->elevator->elevator_data;
 	struct io_context *ioc;
+	struct as_queue *asq = elv_get_sched_queue(q, rq);
 
 	WARN_ON(RQ_STATE(rq) != AS_RQ_QUEUED);
 
@@ -912,8 +916,8 @@ static void as_remove_queued_request(struct request_queue *q,
 	 * Update the "next_rq" cache if we are about to remove its
 	 * entry
 	 */
-	if (ad->next_rq[data_dir] == rq)
-		ad->next_rq[data_dir] = as_find_next_rq(ad, rq);
+	if (asq->next_rq[data_dir] == rq)
+		asq->next_rq[data_dir] = as_find_next_rq(ad, asq, rq);
 
 	rq_fifo_clear(rq);
 	as_del_rq_rb(ad, rq);
@@ -927,23 +931,23 @@ static void as_remove_queued_request(struct request_queue *q,
  *
  * See as_antic_expired comment.
  */
-static int as_fifo_expired(struct as_data *ad, int adir)
+static int as_fifo_expired(struct as_data *ad, struct as_queue *asq, int adir)
 {
 	struct request *rq;
 	long delta_jif;
 
-	delta_jif = jiffies - ad->last_check_fifo[adir];
+	delta_jif = jiffies - asq->last_check_fifo[adir];
 	if (unlikely(delta_jif < 0))
 		delta_jif = -delta_jif;
 	if (delta_jif < ad->fifo_expire[adir])
 		return 0;
 
-	ad->last_check_fifo[adir] = jiffies;
+	asq->last_check_fifo[adir] = jiffies;
 
-	if (list_empty(&ad->fifo_list[adir]))
+	if (list_empty(&asq->fifo_list[adir]))
 		return 0;
 
-	rq = rq_entry_fifo(ad->fifo_list[adir].next);
+	rq = rq_entry_fifo(asq->fifo_list[adir].next);
 
 	return time_after(jiffies, rq_fifo_time(rq));
 }
@@ -952,7 +956,7 @@ static int as_fifo_expired(struct as_data *ad, int adir)
  * as_batch_expired returns true if the current batch has expired. A batch
  * is a set of reads or a set of writes.
  */
-static inline int as_batch_expired(struct as_data *ad)
+static inline int as_batch_expired(struct as_data *ad, struct as_queue *asq)
 {
 	if (ad->changed_batch || ad->new_batch)
 		return 0;
@@ -962,7 +966,7 @@ static inline int as_batch_expired(struct as_data *ad)
 		return time_after(jiffies, ad->current_batch_expires);
 
 	return time_after(jiffies, ad->current_batch_expires)
-		|| ad->current_write_count == 0;
+		|| asq->current_write_count == 0;
 }
 
 /*
@@ -971,6 +975,7 @@ static inline int as_batch_expired(struct as_data *ad)
 static void as_move_to_dispatch(struct as_data *ad, struct request *rq)
 {
 	const int data_dir = rq_is_sync(rq);
+	struct as_queue *asq = elv_get_sched_queue(ad->q, rq);
 
 	BUG_ON(RB_EMPTY_NODE(&rq->rb_node));
 
@@ -993,12 +998,12 @@ static void as_move_to_dispatch(struct as_data *ad, struct request *rq)
 			ad->io_context = NULL;
 		}
 
-		if (ad->current_write_count != 0)
-			ad->current_write_count--;
+		if (asq->current_write_count != 0)
+			asq->current_write_count--;
 	}
 	ad->ioc_finished = 0;
 
-	ad->next_rq[data_dir] = as_find_next_rq(ad, rq);
+	asq->next_rq[data_dir] = as_find_next_rq(ad, asq, rq);
 
 	/*
 	 * take it off the sort and fifo list, add to dispatch queue
@@ -1022,9 +1027,16 @@ static void as_move_to_dispatch(struct as_data *ad, struct request *rq)
 static int as_dispatch_request(struct request_queue *q, int force)
 {
 	struct as_data *ad = q->elevator->elevator_data;
-	const int reads = !list_empty(&ad->fifo_list[BLK_RW_SYNC]);
-	const int writes = !list_empty(&ad->fifo_list[BLK_RW_ASYNC]);
 	struct request *rq;
+	struct as_queue *asq = elv_select_sched_queue(q, force);
+	int reads, writes;
+
+	if (!asq)
+		return 0;
+
+	reads = !list_empty(&asq->fifo_list[BLK_RW_SYNC]);
+	writes = !list_empty(&asq->fifo_list[BLK_RW_ASYNC]);
+
 
 	if (unlikely(force)) {
 		/*
@@ -1040,25 +1052,25 @@ static int as_dispatch_request(struct request_queue *q, int force)
 		ad->changed_batch = 0;
 		ad->new_batch = 0;
 
-		while (ad->next_rq[BLK_RW_SYNC]) {
-			as_move_to_dispatch(ad, ad->next_rq[BLK_RW_SYNC]);
+		while (asq->next_rq[BLK_RW_SYNC]) {
+			as_move_to_dispatch(ad, asq->next_rq[BLK_RW_SYNC]);
 			dispatched++;
 		}
-		ad->last_check_fifo[BLK_RW_SYNC] = jiffies;
+		asq->last_check_fifo[BLK_RW_SYNC] = jiffies;
 
-		while (ad->next_rq[BLK_RW_ASYNC]) {
-			as_move_to_dispatch(ad, ad->next_rq[BLK_RW_ASYNC]);
+		while (asq->next_rq[BLK_RW_ASYNC]) {
+			as_move_to_dispatch(ad, asq->next_rq[BLK_RW_ASYNC]);
 			dispatched++;
 		}
-		ad->last_check_fifo[BLK_RW_ASYNC] = jiffies;
+		asq->last_check_fifo[BLK_RW_ASYNC] = jiffies;
 
 		return dispatched;
 	}
 
 	/* Signal that the write batch was uncontended, so we can't time it */
 	if (ad->batch_data_dir == BLK_RW_ASYNC && !reads) {
-		if (ad->current_write_count == 0 || !writes)
-			ad->write_batch_idled = 1;
+		if (asq->current_write_count == 0 || !writes)
+			asq->write_batch_idled = 1;
 	}
 
 	if (!(reads || writes)
@@ -1067,14 +1079,14 @@ static int as_dispatch_request(struct request_queue *q, int force)
 		|| ad->changed_batch)
 		return 0;
 
-	if (!(reads && writes && as_batch_expired(ad))) {
+	if (!(reads && writes && as_batch_expired(ad, asq))) {
 		/*
 		 * batch is still running or no reads or no writes
 		 */
-		rq = ad->next_rq[ad->batch_data_dir];
+		rq = asq->next_rq[ad->batch_data_dir];
 
 		if (ad->batch_data_dir == BLK_RW_SYNC && ad->antic_expire) {
-			if (as_fifo_expired(ad, BLK_RW_SYNC))
+			if (as_fifo_expired(ad, asq, BLK_RW_SYNC))
 				goto fifo_expired;
 
 			if (as_can_anticipate(ad, rq)) {
@@ -1098,7 +1110,7 @@ static int as_dispatch_request(struct request_queue *q, int force)
 	 */
 
 	if (reads) {
-		BUG_ON(RB_EMPTY_ROOT(&ad->sort_list[BLK_RW_SYNC]));
+		BUG_ON(RB_EMPTY_ROOT(&asq->sort_list[BLK_RW_SYNC]));
 
 		if (writes && ad->batch_data_dir == BLK_RW_SYNC)
 			/*
@@ -1111,8 +1123,8 @@ static int as_dispatch_request(struct request_queue *q, int force)
 			ad->changed_batch = 1;
 		}
 		ad->batch_data_dir = BLK_RW_SYNC;
-		rq = rq_entry_fifo(ad->fifo_list[BLK_RW_SYNC].next);
-		ad->last_check_fifo[ad->batch_data_dir] = jiffies;
+		rq = rq_entry_fifo(asq->fifo_list[BLK_RW_SYNC].next);
+		asq->last_check_fifo[ad->batch_data_dir] = jiffies;
 		goto dispatch_request;
 	}
 
@@ -1122,7 +1134,7 @@ static int as_dispatch_request(struct request_queue *q, int force)
 
 	if (writes) {
 dispatch_writes:
-		BUG_ON(RB_EMPTY_ROOT(&ad->sort_list[BLK_RW_ASYNC]));
+		BUG_ON(RB_EMPTY_ROOT(&asq->sort_list[BLK_RW_ASYNC]));
 
 		if (ad->batch_data_dir == BLK_RW_SYNC) {
 			ad->changed_batch = 1;
@@ -1135,10 +1147,10 @@ dispatch_writes:
 			ad->new_batch = 0;
 		}
 		ad->batch_data_dir = BLK_RW_ASYNC;
-		ad->current_write_count = ad->write_batch_count;
-		ad->write_batch_idled = 0;
-		rq = rq_entry_fifo(ad->fifo_list[BLK_RW_ASYNC].next);
-		ad->last_check_fifo[BLK_RW_ASYNC] = jiffies;
+		asq->current_write_count = asq->write_batch_count;
+		asq->write_batch_idled = 0;
+		rq = rq_entry_fifo(asq->fifo_list[BLK_RW_ASYNC].next);
+		asq->last_check_fifo[BLK_RW_ASYNC] = jiffies;
 		goto dispatch_request;
 	}
 
@@ -1150,9 +1162,9 @@ dispatch_request:
 	 * If a request has expired, service it.
 	 */
 
-	if (as_fifo_expired(ad, ad->batch_data_dir)) {
+	if (as_fifo_expired(ad, asq, ad->batch_data_dir)) {
 fifo_expired:
-		rq = rq_entry_fifo(ad->fifo_list[ad->batch_data_dir].next);
+		rq = rq_entry_fifo(asq->fifo_list[ad->batch_data_dir].next);
 	}
 
 	if (ad->changed_batch) {
@@ -1185,6 +1197,7 @@ static void as_add_request(struct request_queue *q, struct request *rq)
 {
 	struct as_data *ad = q->elevator->elevator_data;
 	int data_dir;
+	struct as_queue *asq = elv_get_sched_queue(q, rq);
 
 	RQ_SET_STATE(rq, AS_RQ_NEW);
 
@@ -1203,7 +1216,7 @@ static void as_add_request(struct request_queue *q, struct request *rq)
 	 * set expire time and add to fifo list
 	 */
 	rq_set_fifo_time(rq, jiffies + ad->fifo_expire[data_dir]);
-	list_add_tail(&rq->queuelist, &ad->fifo_list[data_dir]);
+	list_add_tail(&rq->queuelist, &asq->fifo_list[data_dir]);
 
 	as_update_rq(ad, rq); /* keep state machine up to date */
 	RQ_SET_STATE(rq, AS_RQ_QUEUED);
@@ -1225,31 +1238,20 @@ static void as_deactivate_request(struct request_queue *q, struct request *rq)
 		atomic_inc(&RQ_IOC(rq)->aic->nr_dispatched);
 }
 
-/*
- * as_queue_empty tells us if there are requests left in the device. It may
- * not be the case that a driver can get the next request even if the queue
- * is not empty - it is used in the block layer to check for plugging and
- * merging opportunities
- */
-static int as_queue_empty(struct request_queue *q)
-{
-	struct as_data *ad = q->elevator->elevator_data;
-
-	return list_empty(&ad->fifo_list[BLK_RW_ASYNC])
-		&& list_empty(&ad->fifo_list[BLK_RW_SYNC]);
-}
-
 static int
 as_merge(struct request_queue *q, struct request **req, struct bio *bio)
 {
-	struct as_data *ad = q->elevator->elevator_data;
 	sector_t rb_key = bio->bi_sector + bio_sectors(bio);
 	struct request *__rq;
+	struct as_queue *asq = elv_get_sched_queue_current(q);
+
+	if (!asq)
+		return ELEVATOR_NO_MERGE;
 
 	/*
 	 * check for front merge
 	 */
-	__rq = elv_rb_find(&ad->sort_list[bio_data_dir(bio)], rb_key);
+	__rq = elv_rb_find(&asq->sort_list[bio_data_dir(bio)], rb_key);
 	if (__rq && elv_rq_merge_ok(__rq, bio)) {
 		*req = __rq;
 		return ELEVATOR_FRONT_MERGE;
@@ -1336,6 +1338,41 @@ static int as_may_queue(struct request_queue *q, int rw)
 	return ret;
 }
 
+/* Called with queue lock held */
+static void *as_alloc_as_queue(struct request_queue *q,
+				struct elevator_queue *eq, gfp_t gfp_mask)
+{
+	struct as_queue *asq;
+	struct as_data *ad = eq->elevator_data;
+
+	asq = kmalloc_node(sizeof(*asq), gfp_mask | __GFP_ZERO, q->node);
+	if (asq == NULL)
+		goto out;
+
+	INIT_LIST_HEAD(&asq->fifo_list[BLK_RW_SYNC]);
+	INIT_LIST_HEAD(&asq->fifo_list[BLK_RW_ASYNC]);
+	asq->sort_list[BLK_RW_SYNC] = RB_ROOT;
+	asq->sort_list[BLK_RW_ASYNC] = RB_ROOT;
+	if (ad)
+		asq->write_batch_count = ad->batch_expire[BLK_RW_ASYNC] / 10;
+	else
+		asq->write_batch_count = default_write_batch_expire / 10;
+
+	if (asq->write_batch_count < 2)
+		asq->write_batch_count = 2;
+out:
+	return asq;
+}
+
+static void as_free_as_queue(struct elevator_queue *e, void *sched_queue)
+{
+	struct as_queue *asq = sched_queue;
+
+	BUG_ON(!list_empty(&asq->fifo_list[BLK_RW_SYNC]));
+	BUG_ON(!list_empty(&asq->fifo_list[BLK_RW_ASYNC]));
+	kfree(asq);
+}
+
 static void as_exit_queue(struct elevator_queue *e)
 {
 	struct as_data *ad = e->elevator_data;
@@ -1343,9 +1380,6 @@ static void as_exit_queue(struct elevator_queue *e)
 	del_timer_sync(&ad->antic_timer);
 	cancel_work_sync(&ad->antic_work);
 
-	BUG_ON(!list_empty(&ad->fifo_list[BLK_RW_SYNC]));
-	BUG_ON(!list_empty(&ad->fifo_list[BLK_RW_ASYNC]));
-
 	put_io_context(ad->io_context);
 	kfree(ad);
 }
@@ -1369,10 +1403,6 @@ static void *as_init_queue(struct request_queue *q)
 	init_timer(&ad->antic_timer);
 	INIT_WORK(&ad->antic_work, as_work_handler);
 
-	INIT_LIST_HEAD(&ad->fifo_list[BLK_RW_SYNC]);
-	INIT_LIST_HEAD(&ad->fifo_list[BLK_RW_ASYNC]);
-	ad->sort_list[BLK_RW_SYNC] = RB_ROOT;
-	ad->sort_list[BLK_RW_ASYNC] = RB_ROOT;
 	ad->fifo_expire[BLK_RW_SYNC] = default_read_expire;
 	ad->fifo_expire[BLK_RW_ASYNC] = default_write_expire;
 	ad->antic_expire = default_antic_expire;
@@ -1380,9 +1410,6 @@ static void *as_init_queue(struct request_queue *q)
 	ad->batch_expire[BLK_RW_ASYNC] = default_write_batch_expire;
 
 	ad->current_batch_expires = jiffies + ad->batch_expire[BLK_RW_SYNC];
-	ad->write_batch_count = ad->batch_expire[BLK_RW_ASYNC] / 10;
-	if (ad->write_batch_count < 2)
-		ad->write_batch_count = 2;
 
 	return ad;
 }
@@ -1480,7 +1507,6 @@ static struct elevator_type iosched_as = {
 		.elevator_add_req_fn =		as_add_request,
 		.elevator_activate_req_fn =	as_activate_request,
 		.elevator_deactivate_req_fn = 	as_deactivate_request,
-		.elevator_queue_empty_fn =	as_queue_empty,
 		.elevator_completed_req_fn =	as_completed_request,
 		.elevator_former_req_fn =	elv_rb_former_request,
 		.elevator_latter_req_fn =	elv_rb_latter_request,
@@ -1488,6 +1514,8 @@ static struct elevator_type iosched_as = {
 		.elevator_init_fn =		as_init_queue,
 		.elevator_exit_fn =		as_exit_queue,
 		.trim =				as_trim,
+		.elevator_alloc_sched_queue_fn = as_alloc_as_queue,
+		.elevator_free_sched_queue_fn = as_free_as_queue,
 	},
 
 	.elevator_attrs = as_attrs,
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index c4d991d..5e65041 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -23,25 +23,23 @@ static const int writes_starved = 2;    /* max times reads can starve a write */
 static const int fifo_batch = 16;       /* # of sequential requests treated as one
 				     by the above parameters. For throughput. */
 
-struct deadline_data {
-	/*
-	 * run time data
-	 */
-
+struct deadline_queue {
 	/*
 	 * requests (deadline_rq s) are present on both sort_list and fifo_list
 	 */
-	struct rb_root sort_list[2];	
+	struct rb_root sort_list[2];
 	struct list_head fifo_list[2];
-
 	/*
 	 * next in sort order. read, write or both are NULL
 	 */
 	struct request *next_rq[2];
 	unsigned int batching;		/* number of sequential requests made */
-	sector_t last_sector;		/* head position */
 	unsigned int starved;		/* times reads have starved writes */
+};
 
+struct deadline_data {
+	struct request_queue *q;
+	sector_t last_sector;		/* head position */
 	/*
 	 * settings that change how the i/o scheduler behaves
 	 */
@@ -56,7 +54,9 @@ static void deadline_move_request(struct deadline_data *, struct request *);
 static inline struct rb_root *
 deadline_rb_root(struct deadline_data *dd, struct request *rq)
 {
-	return &dd->sort_list[rq_data_dir(rq)];
+	struct deadline_queue *dq = elv_get_sched_queue(dd->q, rq);
+
+	return &dq->sort_list[rq_data_dir(rq)];
 }
 
 /*
@@ -87,9 +87,10 @@ static inline void
 deadline_del_rq_rb(struct deadline_data *dd, struct request *rq)
 {
 	const int data_dir = rq_data_dir(rq);
+	struct deadline_queue *dq = elv_get_sched_queue(dd->q, rq);
 
-	if (dd->next_rq[data_dir] == rq)
-		dd->next_rq[data_dir] = deadline_latter_request(rq);
+	if (dq->next_rq[data_dir] == rq)
+		dq->next_rq[data_dir] = deadline_latter_request(rq);
 
 	elv_rb_del(deadline_rb_root(dd, rq), rq);
 }
@@ -102,6 +103,7 @@ deadline_add_request(struct request_queue *q, struct request *rq)
 {
 	struct deadline_data *dd = q->elevator->elevator_data;
 	const int data_dir = rq_data_dir(rq);
+	struct deadline_queue *dq = elv_get_sched_queue(q, rq);
 
 	deadline_add_rq_rb(dd, rq);
 
@@ -109,7 +111,7 @@ deadline_add_request(struct request_queue *q, struct request *rq)
 	 * set expire time and add to fifo list
 	 */
 	rq_set_fifo_time(rq, jiffies + dd->fifo_expire[data_dir]);
-	list_add_tail(&rq->queuelist, &dd->fifo_list[data_dir]);
+	list_add_tail(&rq->queuelist, &dq->fifo_list[data_dir]);
 }
 
 /*
@@ -129,6 +131,11 @@ deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
 	struct deadline_data *dd = q->elevator->elevator_data;
 	struct request *__rq;
 	int ret;
+	struct deadline_queue *dq;
+
+	dq = elv_get_sched_queue_current(q);
+	if (!dq)
+		return ELEVATOR_NO_MERGE;
 
 	/*
 	 * check for front merge
@@ -136,7 +143,7 @@ deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
 	if (dd->front_merges) {
 		sector_t sector = bio->bi_sector + bio_sectors(bio);
 
-		__rq = elv_rb_find(&dd->sort_list[bio_data_dir(bio)], sector);
+		__rq = elv_rb_find(&dq->sort_list[bio_data_dir(bio)], sector);
 		if (__rq) {
 			BUG_ON(sector != __rq->sector);
 
@@ -207,10 +214,11 @@ static void
 deadline_move_request(struct deadline_data *dd, struct request *rq)
 {
 	const int data_dir = rq_data_dir(rq);
+	struct deadline_queue *dq = elv_get_sched_queue(dd->q, rq);
 
-	dd->next_rq[READ] = NULL;
-	dd->next_rq[WRITE] = NULL;
-	dd->next_rq[data_dir] = deadline_latter_request(rq);
+	dq->next_rq[READ] = NULL;
+	dq->next_rq[WRITE] = NULL;
+	dq->next_rq[data_dir] = deadline_latter_request(rq);
 
 	dd->last_sector = rq_end_sector(rq);
 
@@ -225,9 +233,9 @@ deadline_move_request(struct deadline_data *dd, struct request *rq)
  * deadline_check_fifo returns 0 if there are no expired requests on the fifo,
  * 1 otherwise. Requires !list_empty(&dd->fifo_list[data_dir])
  */
-static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
+static inline int deadline_check_fifo(struct deadline_queue *dq, int ddir)
 {
-	struct request *rq = rq_entry_fifo(dd->fifo_list[ddir].next);
+	struct request *rq = rq_entry_fifo(dq->fifo_list[ddir].next);
 
 	/*
 	 * rq is expired!
@@ -245,20 +253,26 @@ static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
 static int deadline_dispatch_requests(struct request_queue *q, int force)
 {
 	struct deadline_data *dd = q->elevator->elevator_data;
-	const int reads = !list_empty(&dd->fifo_list[READ]);
-	const int writes = !list_empty(&dd->fifo_list[WRITE]);
+	struct deadline_queue *dq = elv_select_sched_queue(q, force);
+	int reads, writes;
 	struct request *rq;
 	int data_dir;
 
+	if (!dq)
+		return 0;
+
+	reads = !list_empty(&dq->fifo_list[READ]);
+	writes = !list_empty(&dq->fifo_list[WRITE]);
+
 	/*
 	 * batches are currently reads XOR writes
 	 */
-	if (dd->next_rq[WRITE])
-		rq = dd->next_rq[WRITE];
+	if (dq->next_rq[WRITE])
+		rq = dq->next_rq[WRITE];
 	else
-		rq = dd->next_rq[READ];
+		rq = dq->next_rq[READ];
 
-	if (rq && dd->batching < dd->fifo_batch)
+	if (rq && dq->batching < dd->fifo_batch)
 		/* we have a next request are still entitled to batch */
 		goto dispatch_request;
 
@@ -268,9 +282,9 @@ static int deadline_dispatch_requests(struct request_queue *q, int force)
 	 */
 
 	if (reads) {
-		BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[READ]));
+		BUG_ON(RB_EMPTY_ROOT(&dq->sort_list[READ]));
 
-		if (writes && (dd->starved++ >= dd->writes_starved))
+		if (writes && (dq->starved++ >= dd->writes_starved))
 			goto dispatch_writes;
 
 		data_dir = READ;
@@ -284,9 +298,9 @@ static int deadline_dispatch_requests(struct request_queue *q, int force)
 
 	if (writes) {
 dispatch_writes:
-		BUG_ON(RB_EMPTY_ROOT(&dd->sort_list[WRITE]));
+		BUG_ON(RB_EMPTY_ROOT(&dq->sort_list[WRITE]));
 
-		dd->starved = 0;
+		dq->starved = 0;
 
 		data_dir = WRITE;
 
@@ -299,48 +313,62 @@ dispatch_find_request:
 	/*
 	 * we are not running a batch, find best request for selected data_dir
 	 */
-	if (deadline_check_fifo(dd, data_dir) || !dd->next_rq[data_dir]) {
+	if (deadline_check_fifo(dq, data_dir) || !dq->next_rq[data_dir]) {
 		/*
 		 * A deadline has expired, the last request was in the other
 		 * direction, or we have run out of higher-sectored requests.
 		 * Start again from the request with the earliest expiry time.
 		 */
-		rq = rq_entry_fifo(dd->fifo_list[data_dir].next);
+		rq = rq_entry_fifo(dq->fifo_list[data_dir].next);
 	} else {
 		/*
 		 * The last req was the same dir and we have a next request in
 		 * sort order. No expired requests so continue on from here.
 		 */
-		rq = dd->next_rq[data_dir];
+		rq = dq->next_rq[data_dir];
 	}
 
-	dd->batching = 0;
+	dq->batching = 0;
 
 dispatch_request:
 	/*
 	 * rq is the selected appropriate request.
 	 */
-	dd->batching++;
+	dq->batching++;
 	deadline_move_request(dd, rq);
 
 	return 1;
 }
 
-static int deadline_queue_empty(struct request_queue *q)
+static void *deadline_alloc_deadline_queue(struct request_queue *q,
+				struct elevator_queue *eq, gfp_t gfp_mask)
 {
-	struct deadline_data *dd = q->elevator->elevator_data;
+	struct deadline_queue *dq;
 
-	return list_empty(&dd->fifo_list[WRITE])
-		&& list_empty(&dd->fifo_list[READ]);
+	dq = kmalloc_node(sizeof(*dq), gfp_mask | __GFP_ZERO, q->node);
+	if (dq == NULL)
+		goto out;
+
+	INIT_LIST_HEAD(&dq->fifo_list[READ]);
+	INIT_LIST_HEAD(&dq->fifo_list[WRITE]);
+	dq->sort_list[READ] = RB_ROOT;
+	dq->sort_list[WRITE] = RB_ROOT;
+out:
+	return dq;
+}
+
+static void deadline_free_deadline_queue(struct elevator_queue *e,
+						void *sched_queue)
+{
+	struct deadline_queue *dq = sched_queue;
+
+	kfree(dq);
 }
 
 static void deadline_exit_queue(struct elevator_queue *e)
 {
 	struct deadline_data *dd = e->elevator_data;
 
-	BUG_ON(!list_empty(&dd->fifo_list[READ]));
-	BUG_ON(!list_empty(&dd->fifo_list[WRITE]));
-
 	kfree(dd);
 }
 
@@ -355,10 +383,7 @@ static void *deadline_init_queue(struct request_queue *q)
 	if (!dd)
 		return NULL;
 
-	INIT_LIST_HEAD(&dd->fifo_list[READ]);
-	INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
-	dd->sort_list[READ] = RB_ROOT;
-	dd->sort_list[WRITE] = RB_ROOT;
+	dd->q = q;
 	dd->fifo_expire[READ] = read_expire;
 	dd->fifo_expire[WRITE] = write_expire;
 	dd->writes_starved = writes_starved;
@@ -445,13 +470,13 @@ static struct elevator_type iosched_deadline = {
 		.elevator_merge_req_fn =	deadline_merged_requests,
 		.elevator_dispatch_fn =		deadline_dispatch_requests,
 		.elevator_add_req_fn =		deadline_add_request,
-		.elevator_queue_empty_fn =	deadline_queue_empty,
 		.elevator_former_req_fn =	elv_rb_former_request,
 		.elevator_latter_req_fn =	elv_rb_latter_request,
 		.elevator_init_fn =		deadline_init_queue,
 		.elevator_exit_fn =		deadline_exit_queue,
+		.elevator_alloc_sched_queue_fn = deadline_alloc_deadline_queue,
+		.elevator_free_sched_queue_fn = deadline_free_deadline_queue,
 	},
-
 	.elevator_attrs = deadline_attrs,
 	.elevator_name = "deadline",
 	.elevator_owner = THIS_MODULE,
diff --git a/block/elevator.c b/block/elevator.c
index 3944385..67a0601 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -180,17 +180,54 @@ static struct elevator_type *elevator_get(const char *name)
 	return e;
 }
 
-static void *elevator_init_queue(struct request_queue *q,
-				 struct elevator_queue *eq)
+static void *elevator_init_data(struct request_queue *q,
+					struct elevator_queue *eq)
 {
-	return eq->ops->elevator_init_fn(q);
+	void *data = NULL;
+
+	if (eq->ops->elevator_init_fn) {
+		data = eq->ops->elevator_init_fn(q);
+		if (data)
+			return data;
+		else
+			return ERR_PTR(-ENOMEM);
+	}
+
+	/* IO scheduler does not instanciate data (noop), it is not an error */
+	return NULL;
+}
+
+static void elevator_free_sched_queue(struct elevator_queue *eq,
+						void *sched_queue)
+{
+	/* Not all io schedulers (cfq) strore sched_queue */
+	if (!sched_queue)
+		return;
+	eq->ops->elevator_free_sched_queue_fn(eq, sched_queue);
+}
+
+static void *elevator_alloc_sched_queue(struct request_queue *q,
+					struct elevator_queue *eq)
+{
+	void *sched_queue = NULL;
+
+	if (eq->ops->elevator_alloc_sched_queue_fn) {
+		sched_queue = eq->ops->elevator_alloc_sched_queue_fn(q, eq,
+								GFP_KERNEL);
+		if (!sched_queue)
+			return ERR_PTR(-ENOMEM);
+
+	}
+
+	return sched_queue;
 }
 
 static void elevator_attach(struct request_queue *q, struct elevator_queue *eq,
-			   void *data)
+			   void *data, void *sched_queue)
 {
 	q->elevator = eq;
 	eq->elevator_data = data;
+	eq->sched_queue = sched_queue;
 }
 
 static char chosen_elevator[16];
@@ -260,7 +297,7 @@ int elevator_init(struct request_queue *q, char *name)
 	struct elevator_type *e = NULL;
 	struct elevator_queue *eq;
 	int ret = 0;
-	void *data;
+	void *data = NULL, *sched_queue = NULL;
 
 	INIT_LIST_HEAD(&q->queue_head);
 	q->last_merge = NULL;
@@ -294,13 +331,21 @@ int elevator_init(struct request_queue *q, char *name)
 	if (!eq)
 		return -ENOMEM;
 
-	data = elevator_init_queue(q, eq);
-	if (!data) {
+	data = elevator_init_data(q, eq);
+
+	if (IS_ERR(data)) {
+		kobject_put(&eq->kobj);
+		return -ENOMEM;
+	}
+
+	sched_queue = elevator_alloc_sched_queue(q, eq);
+
+	if (IS_ERR(sched_queue)) {
 		kobject_put(&eq->kobj);
 		return -ENOMEM;
 	}
 
-	elevator_attach(q, eq, data);
+	elevator_attach(q, eq, data, sched_queue);
 	return ret;
 }
 EXPORT_SYMBOL(elevator_init);
@@ -308,6 +353,7 @@ EXPORT_SYMBOL(elevator_init);
 void elevator_exit(struct elevator_queue *e)
 {
 	mutex_lock(&e->sysfs_lock);
+	elevator_free_sched_queue(e, e->sched_queue);
 	elv_exit_fq_data(e);
 	if (e->ops->elevator_exit_fn)
 		e->ops->elevator_exit_fn(e);
@@ -1121,7 +1167,7 @@ EXPORT_SYMBOL_GPL(elv_unregister);
 static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 {
 	struct elevator_queue *old_elevator, *e;
-	void *data;
+	void *data = NULL, *sched_queue = NULL;
 
 	/*
 	 * Allocate new elevator
@@ -1130,10 +1176,18 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 	if (!e)
 		return 0;
 
-	data = elevator_init_queue(q, e);
-	if (!data) {
+	data = elevator_init_data(q, e);
+
+	if (IS_ERR(data)) {
 		kobject_put(&e->kobj);
-		return 0;
+		return -ENOMEM;
+	}
+
+	sched_queue = elevator_alloc_sched_queue(q, e);
+
+	if (IS_ERR(sched_queue)) {
+		kobject_put(&e->kobj);
+		return -ENOMEM;
 	}
 
 	/*
@@ -1150,7 +1204,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 	/*
 	 * attach and start new elevator
 	 */
-	elevator_attach(q, e, data);
+	elevator_attach(q, e, data, sched_queue);
 
 	spin_unlock_irq(q->queue_lock);
 
@@ -1257,16 +1311,43 @@ struct request *elv_rb_latter_request(struct request_queue *q,
 }
 EXPORT_SYMBOL(elv_rb_latter_request);
 
-/* Get the io scheduler queue pointer. For cfq, it is stored in rq->ioq*/
+/* Get the io scheduler queue pointer. */
 void *elv_get_sched_queue(struct request_queue *q, struct request *rq)
 {
-	return ioq_sched_queue(rq_ioq(rq));
+	/*
+	 * io scheduler is not using fair queuing. Return sched_queue
+	 * pointer stored in elevator_queue. It will be null if io
+	 * scheduler never stored anything there to begin with (cfq)
+	 */
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return q->elevator->sched_queue;
+
+	/*
+	 * IO schedueler is using fair queuing infrasture. If io scheduler
+	 * has passed a non null rq, retrieve sched_queue pointer from
+	 * there. */
+	if (rq)
+		return ioq_sched_queue(rq_ioq(rq));
+
+	return NULL;
 }
 EXPORT_SYMBOL(elv_get_sched_queue);
 
 /* Select an ioscheduler queue to dispatch request from. */
 void *elv_select_sched_queue(struct request_queue *q, int force)
 {
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return q->elevator->sched_queue;
+
 	return ioq_sched_queue(elv_fq_select_ioq(q, force));
 }
 EXPORT_SYMBOL(elv_select_sched_queue);
+
+/*
+ * Get the io scheduler queue pointer for current task.
+ */
+void *elv_get_sched_queue_current(struct request_queue *q)
+{
+	return q->elevator->sched_queue;
+}
+EXPORT_SYMBOL(elv_get_sched_queue_current);
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
index 3a0d369..d587832 100644
--- a/block/noop-iosched.c
+++ b/block/noop-iosched.c
@@ -7,7 +7,7 @@
 #include <linux/module.h>
 #include <linux/init.h>
 
-struct noop_data {
+struct noop_queue {
 	struct list_head queue;
 };
 
@@ -19,11 +19,14 @@ static void noop_merged_requests(struct request_queue *q, struct request *rq,
 
 static int noop_dispatch(struct request_queue *q, int force)
 {
-	struct noop_data *nd = q->elevator->elevator_data;
+	struct noop_queue *nq = elv_select_sched_queue(q, force);
 
-	if (!list_empty(&nd->queue)) {
+	if (!nq)
+		return 0;
+
+	if (!list_empty(&nq->queue)) {
 		struct request *rq;
-		rq = list_entry(nd->queue.next, struct request, queuelist);
+		rq = list_entry(nq->queue.next, struct request, queuelist);
 		list_del_init(&rq->queuelist);
 		elv_dispatch_sort(q, rq);
 		return 1;
@@ -33,24 +36,17 @@ static int noop_dispatch(struct request_queue *q, int force)
 
 static void noop_add_request(struct request_queue *q, struct request *rq)
 {
-	struct noop_data *nd = q->elevator->elevator_data;
+	struct noop_queue *nq = elv_get_sched_queue(q, rq);
 
-	list_add_tail(&rq->queuelist, &nd->queue);
-}
-
-static int noop_queue_empty(struct request_queue *q)
-{
-	struct noop_data *nd = q->elevator->elevator_data;
-
-	return list_empty(&nd->queue);
+	list_add_tail(&rq->queuelist, &nq->queue);
 }
 
 static struct request *
 noop_former_request(struct request_queue *q, struct request *rq)
 {
-	struct noop_data *nd = q->elevator->elevator_data;
+	struct noop_queue *nq = elv_get_sched_queue(q, rq);
 
-	if (rq->queuelist.prev == &nd->queue)
+	if (rq->queuelist.prev == &nq->queue)
 		return NULL;
 	return list_entry(rq->queuelist.prev, struct request, queuelist);
 }
@@ -58,30 +54,32 @@ noop_former_request(struct request_queue *q, struct request *rq)
 static struct request *
 noop_latter_request(struct request_queue *q, struct request *rq)
 {
-	struct noop_data *nd = q->elevator->elevator_data;
+	struct noop_queue *nq = elv_get_sched_queue(q, rq);
 
-	if (rq->queuelist.next == &nd->queue)
+	if (rq->queuelist.next == &nq->queue)
 		return NULL;
 	return list_entry(rq->queuelist.next, struct request, queuelist);
 }
 
-static void *noop_init_queue(struct request_queue *q)
+static void *noop_alloc_noop_queue(struct request_queue *q,
+				struct elevator_queue *eq, gfp_t gfp_mask)
 {
-	struct noop_data *nd;
+	struct noop_queue *nq;
 
-	nd = kmalloc_node(sizeof(*nd), GFP_KERNEL, q->node);
-	if (!nd)
-		return NULL;
-	INIT_LIST_HEAD(&nd->queue);
-	return nd;
+	nq = kmalloc_node(sizeof(*nq), gfp_mask | __GFP_ZERO, q->node);
+	if (nq == NULL)
+		goto out;
+
+	INIT_LIST_HEAD(&nq->queue);
+out:
+	return nq;
 }
 
-static void noop_exit_queue(struct elevator_queue *e)
+static void noop_free_noop_queue(struct elevator_queue *e, void *sched_queue)
 {
-	struct noop_data *nd = e->elevator_data;
+	struct noop_queue *nq = sched_queue;
 
-	BUG_ON(!list_empty(&nd->queue));
-	kfree(nd);
+	kfree(nq);
 }
 
 static struct elevator_type elevator_noop = {
@@ -89,11 +87,10 @@ static struct elevator_type elevator_noop = {
 		.elevator_merge_req_fn		= noop_merged_requests,
 		.elevator_dispatch_fn		= noop_dispatch,
 		.elevator_add_req_fn		= noop_add_request,
-		.elevator_queue_empty_fn	= noop_queue_empty,
 		.elevator_former_req_fn		= noop_former_request,
 		.elevator_latter_req_fn		= noop_latter_request,
-		.elevator_init_fn		= noop_init_queue,
-		.elevator_exit_fn		= noop_exit_queue,
+		.elevator_alloc_sched_queue_fn	= noop_alloc_noop_queue,
+		.elevator_free_sched_queue_fn	= noop_free_noop_queue,
 	},
 	.elevator_name = "noop",
 	.elevator_owner = THIS_MODULE,
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 679c149..3729a2f 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -30,8 +30,9 @@ typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct reques
 
 typedef void *(elevator_init_fn) (struct request_queue *);
 typedef void (elevator_exit_fn) (struct elevator_queue *);
-#ifdef CONFIG_ELV_FAIR_QUEUING
+typedef void* (elevator_alloc_sched_queue_fn) (struct request_queue *q, struct elevator_queue *eq, gfp_t);
 typedef void (elevator_free_sched_queue_fn) (struct elevator_queue*, void *);
+#ifdef CONFIG_ELV_FAIR_QUEUING
 typedef void (elevator_active_ioq_set_fn) (struct request_queue*, void *, int);
 typedef void (elevator_active_ioq_reset_fn) (struct request_queue *, void*);
 typedef void (elevator_arm_slice_timer_fn) (struct request_queue*, void*);
@@ -70,8 +71,9 @@ struct elevator_ops
 	elevator_exit_fn *elevator_exit_fn;
 	void (*trim)(struct io_context *);
 
-#ifdef CONFIG_ELV_FAIR_QUEUING
+	elevator_alloc_sched_queue_fn *elevator_alloc_sched_queue_fn;
 	elevator_free_sched_queue_fn *elevator_free_sched_queue_fn;
+#ifdef CONFIG_ELV_FAIR_QUEUING
 	elevator_active_ioq_set_fn *elevator_active_ioq_set_fn;
 	elevator_active_ioq_reset_fn *elevator_active_ioq_reset_fn;
 
@@ -112,6 +114,7 @@ struct elevator_queue
 {
 	struct elevator_ops *ops;
 	void *elevator_data;
+	void *sched_queue;
 	struct kobject kobj;
 	struct elevator_type *elevator_type;
 	struct mutex sysfs_lock;
@@ -260,5 +263,6 @@ static inline int elv_iosched_fair_queuing_enabled(struct elevator_queue *e)
 #endif /* ELV_IOSCHED_FAIR_QUEUING */
 extern void *elv_get_sched_queue(struct request_queue *q, struct request *rq);
 extern void *elv_select_sched_queue(struct request_queue *q, int force);
+extern void *elv_get_sched_queue_current(struct request_queue *q);
 #endif /* CONFIG_BLOCK */
 #endif
-- 
1.6.0.1

[PATCH 10/20] io-conroller: Prepare elevator layer for single queue schedulers

[Vivek Goyal]

Elevator layer now has support for hierarchical fair queuing. cfq has
been migrated to make use of it and now it is time to do groundwork for
noop, deadline and AS.

noop deadline and AS don't maintain separate queues for different processes.
There is only one single queue. Effectively one can think that in hierarchical
setup, there will be one queue per cgroup where requests from all the
processes in the cgroup will be queued.

Generally io scheduler takes care of creating queues. Because there is
only one queue here, we have modified common layer to take care of queue
creation and some other functionality. This special casing helps in keeping
the changes to noop, deadline and AS to the minimum.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/elevator-fq.c      |  160 +++++++++++++++++++++++++++++++++++++++++++++-
 block/elevator-fq.h      |   67 +++++++++++++++++++
 block/elevator.c         |   35 ++++++++++-
 include/linux/elevator.h |   14 ++++
 4 files changed, 274 insertions(+), 2 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 201785e..10787fd 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -916,6 +916,12 @@ void io_put_io_group_queues(struct elevator_queue *e, struct io_group *iog)
 
 	/* Free up async idle queue */
 	elv_release_ioq(e, &iog->async_idle_queue);
+
+#ifdef CONFIG_GROUP_IOSCHED
+	/* Optimization for io schedulers having single ioq */
+	if (elv_iosched_single_ioq(e))
+		elv_release_ioq(e, &iog->ioq);
+#endif
 }
 
 /*
@@ -1665,6 +1671,153 @@ int io_group_allow_merge(struct request *rq, struct bio *bio)
 	return (iog == __iog);
 }
 
+/*
+ * Find/Create the io queue the rq should go in. This is an optimization
+ * for the io schedulers (noop, deadline and AS) which maintain only single
+ * io queue per cgroup. In this case common layer can just maintain a
+ * pointer in group data structure and keeps track of it.
+ *
+ * For the io schdulers like cfq, which maintain multiple io queues per
+ * cgroup, and decide the io queue  of request based on process, this
+ * function is not invoked.
+ */
+int elv_fq_set_request_ioq(struct request_queue *q, struct request *rq,
+					gfp_t gfp_mask)
+{
+	struct elevator_queue *e = q->elevator;
+	unsigned long flags;
+	struct io_queue *ioq = NULL, *new_ioq = NULL;
+	struct io_group *iog;
+	void *sched_q = NULL, *new_sched_q = NULL;
+
+	if (!elv_iosched_fair_queuing_enabled(e))
+		return 0;
+
+	might_sleep_if(gfp_mask & __GFP_WAIT);
+	spin_lock_irqsave(q->queue_lock, flags);
+
+retry:
+	/* Determine the io group request belongs to */
+	iog = io_get_io_group(q, 1);
+	BUG_ON(!iog);
+
+	/* Get the iosched queue */
+	ioq = io_group_ioq(iog);
+	if (!ioq) {
+		/* io queue and sched_queue needs to be allocated */
+		BUG_ON(!e->ops->elevator_alloc_sched_queue_fn);
+
+		if (new_sched_q) {
+			goto alloc_ioq;
+		} else if (gfp_mask & __GFP_WAIT) {
+			/*
+			 * Inform the allocator of the fact that we will
+			 * just repeat this allocation if it fails, to allow
+			 * the allocator to do whatever it needs to attempt to
+			 * free memory.
+			 */
+			spin_unlock_irq(q->queue_lock);
+			/* Call io scheduer to create scheduler queue */
+			new_sched_q = e->ops->elevator_alloc_sched_queue_fn(q,
+					e, gfp_mask | __GFP_NOFAIL
+					| __GFP_ZERO);
+			spin_lock_irq(q->queue_lock);
+			goto retry;
+		} else {
+			sched_q = e->ops->elevator_alloc_sched_queue_fn(q, e,
+						gfp_mask | __GFP_ZERO);
+			if (!sched_q)
+				goto queue_fail;
+		}
+
+alloc_ioq:
+		if (new_ioq) {
+			ioq = new_ioq;
+			new_ioq = NULL;
+			sched_q = new_sched_q;
+			new_sched_q = NULL;
+		} else if (gfp_mask & __GFP_WAIT) {
+			/*
+			 * Inform the allocator of the fact that we will
+			 * just repeat this allocation if it fails, to allow
+			 * the allocator to do whatever it needs to attempt to
+			 * free memory.
+			 */
+			spin_unlock_irq(q->queue_lock);
+			new_ioq = elv_alloc_ioq(q, gfp_mask | __GFP_NOFAIL
+							| __GFP_ZERO);
+			spin_lock_irq(q->queue_lock);
+			goto retry;
+		} else {
+			ioq = elv_alloc_ioq(q, gfp_mask | __GFP_ZERO);
+			if (!ioq) {
+				e->ops->elevator_free_sched_queue_fn(e,
+							sched_q);
+				sched_q = NULL;
+				goto queue_fail;
+			}
+		}
+
+		elv_init_ioq(e, ioq, iog, sched_q, IOPRIO_CLASS_BE, 4, 1);
+		io_group_set_ioq(iog, ioq);
+		elv_mark_ioq_sync(ioq);
+	}
+
+	if (new_sched_q)
+		e->ops->elevator_free_sched_queue_fn(q->elevator, sched_q);
+
+	if (new_ioq)
+		elv_free_ioq(new_ioq);
+
+	/* Request reference */
+	elv_get_ioq(ioq);
+	rq->ioq = ioq;
+	spin_unlock_irqrestore(q->queue_lock, flags);
+	return 0;
+
+queue_fail:
+	WARN_ON((gfp_mask & __GFP_WAIT) && !ioq);
+	elv_schedule_dispatch(q);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+	return 1;
+}
+
+/*
+ * Find out the io queue of current task. Optimization for single ioq
+ * per io group io schedulers.
+ */
+struct io_queue *elv_lookup_ioq_current(struct request_queue *q)
+{
+	struct io_group *iog;
+
+	/* Determine the io group and io queue of the bio submitting task */
+	iog = io_get_io_group(q, 0);
+	if (!iog) {
+		/* May be task belongs to a cgroup for which io group has
+		 * not been setup yet. */
+		return NULL;
+	}
+	return io_group_ioq(iog);
+}
+
+/*
+ * This request has been serviced. Clean up ioq info and drop the reference.
+ * Again this is called only for single queue per cgroup schedulers (noop,
+ * deadline, AS).
+ */
+void elv_fq_unset_request_ioq(struct request_queue *q, struct request *rq)
+{
+	struct io_queue *ioq = rq->ioq;
+
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return;
+
+	if (ioq) {
+		rq->ioq = NULL;
+		elv_put_ioq(ioq);
+	}
+}
+
 #else /* GROUP_IOSCHED */
 void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
 {
@@ -2097,7 +2250,12 @@ int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq,
 	ioq->efqd = efqd;
 	elv_ioq_set_ioprio_class(ioq, ioprio_class);
 	elv_ioq_set_ioprio(ioq, ioprio);
-	ioq->pid = current->pid;
+
+	if (elv_iosched_single_ioq(eq))
+		ioq->pid = 0;
+	else
+		ioq->pid = current->pid;
+
 	ioq->sched_queue = sched_queue;
 	if (is_sync && !elv_ioq_class_idle(ioq))
 		elv_mark_ioq_idle_window(ioq);
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 4f11be3..d79dad7 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -241,6 +241,9 @@ struct io_group {
 	/* The device MKDEV(major, minor), this group has been created for */
 	dev_t	dev;
 
+	/* Single ioq per group, used for noop, deadline, anticipatory */
+	struct io_queue *ioq;
+
 };
 
 /**
@@ -512,6 +515,28 @@ static inline bfq_weight_t iog_weight(struct io_group *iog)
 	return iog->entity.weight;
 }
 
+extern int elv_fq_set_request_ioq(struct request_queue *q, struct request *rq,
+					gfp_t gfp_mask);
+extern void elv_fq_unset_request_ioq(struct request_queue *q,
+					struct request *rq);
+extern struct io_queue *elv_lookup_ioq_current(struct request_queue *q);
+
+/* Returns single ioq associated with the io group. */
+static inline struct io_queue *io_group_ioq(struct io_group *iog)
+{
+	BUG_ON(!iog);
+	return iog->ioq;
+}
+
+/* Sets the single ioq associated with the io group. (noop, deadline, AS) */
+static inline void io_group_set_ioq(struct io_group *iog, struct io_queue *ioq)
+{
+	BUG_ON(!iog);
+	/* io group reference. Will be dropped when group is destroyed. */
+	elv_get_ioq(ioq);
+	iog->ioq = ioq;
+}
+
 #else /* !GROUP_IOSCHED */
 /*
  * No ioq movement is needed in case of flat setup. root io group gets cleaned
@@ -538,6 +563,32 @@ static inline bfq_weight_t iog_weight(struct io_group *iog)
 	return 0;
 }
 
+/* Returns single ioq associated with the io group. */
+static inline struct io_queue *io_group_ioq(struct io_group *iog)
+{
+	return NULL;
+}
+
+static inline void io_group_set_ioq(struct io_group *iog, struct io_queue *ioq)
+{
+}
+
+static inline int elv_fq_set_request_ioq(struct request_queue *q,
+					struct request *rq, gfp_t gfp_mask)
+{
+	return 0;
+}
+
+static inline void elv_fq_unset_request_ioq(struct request_queue *q,
+						struct request *rq)
+{
+}
+
+static inline struct io_queue *elv_lookup_ioq_current(struct request_queue *q)
+{
+	return NULL;
+}
+
 #endif /* GROUP_IOSCHED */
 
 /* Functions used by blksysfs.c */
@@ -651,5 +702,21 @@ static inline int io_group_allow_merge(struct request *rq, struct bio *bio)
 {
 	return 1;
 }
+static inline int elv_fq_set_request_ioq(struct request_queue *q,
+					struct request *rq, gfp_t gfp_mask)
+{
+	return 0;
+}
+
+static inline void elv_fq_unset_request_ioq(struct request_queue *q,
+						struct request *rq)
+{
+}
+
+static inline struct io_queue *elv_lookup_ioq_current(struct request_queue *q)
+{
+	return NULL;
+}
+
 #endif /* CONFIG_ELV_FAIR_QUEUING */
 #endif /* _BFQ_SCHED_H */
diff --git a/block/elevator.c b/block/elevator.c
index 67a0601..8b2206f 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -211,6 +211,14 @@ static void *elevator_alloc_sched_queue(struct request_queue *q,
 {
 	void *sched_queue = NULL;
 
+	/*
+	 * If fair queuing is enabled, then queue allocation takes place
+	 * during set_request() functions when request actually comes
+	 * in.
+	 */
+	if (elv_iosched_fair_queuing_enabled(eq))
+		return NULL;
+
 	if (eq->ops->elevator_alloc_sched_queue_fn) {
 		sched_queue = eq->ops->elevator_alloc_sched_queue_fn(q, eq,
 								GFP_KERNEL);
@@ -963,6 +971,13 @@ int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 {
 	struct elevator_queue *e = q->elevator;
 
+	/*
+	 * Optimization for noop, deadline and AS which maintain only single
+	 * ioq per io group
+	 */
+	if (elv_iosched_single_ioq(e))
+		return elv_fq_set_request_ioq(q, rq, gfp_mask);
+
 	if (e->ops->elevator_set_req_fn)
 		return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
 
@@ -974,6 +989,15 @@ void elv_put_request(struct request_queue *q, struct request *rq)
 {
 	struct elevator_queue *e = q->elevator;
 
+	/*
+	 * Optimization for noop, deadline and AS which maintain only single
+	 * ioq per io group
+	 */
+	if (elv_iosched_single_ioq(e)) {
+		elv_fq_unset_request_ioq(q, rq);
+		return;
+	}
+
 	if (e->ops->elevator_put_req_fn)
 		e->ops->elevator_put_req_fn(rq);
 }
@@ -1345,9 +1369,18 @@ EXPORT_SYMBOL(elv_select_sched_queue);
 
 /*
  * Get the io scheduler queue pointer for current task.
+ *
+ * If fair queuing is enabled, determine the io group of task and retrieve
+ * the ioq pointer from that. This is used by only single queue ioschedulers
+ * for retrieving the queue associated with the group to decide whether the
+ * new bio can do a front merge or not.
  */
 void *elv_get_sched_queue_current(struct request_queue *q)
 {
-	return q->elevator->sched_queue;
+	/* Fair queuing is not enabled. There is only one queue. */
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return q->elevator->sched_queue;
+
+	return ioq_sched_queue(elv_lookup_ioq_current(q));
 }
 EXPORT_SYMBOL(elv_get_sched_queue_current);
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 3729a2f..ee38d08 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -249,17 +249,31 @@ enum {
 /* iosched wants to use fq logic of elevator layer */
 #define	ELV_IOSCHED_NEED_FQ	1
 
+/* iosched maintains only single ioq per group.*/
+#define ELV_IOSCHED_SINGLE_IOQ        2
+
 static inline int elv_iosched_fair_queuing_enabled(struct elevator_queue *e)
 {
 	return (e->elevator_type->elevator_features) & ELV_IOSCHED_NEED_FQ;
 }
 
+static inline int elv_iosched_single_ioq(struct elevator_queue *e)
+{
+	return (e->elevator_type->elevator_features) & ELV_IOSCHED_SINGLE_IOQ;
+}
+
 #else /* ELV_IOSCHED_FAIR_QUEUING */
 
 static inline int elv_iosched_fair_queuing_enabled(struct elevator_queue *e)
 {
 	return 0;
 }
+
+static inline int elv_iosched_single_ioq(struct elevator_queue *e)
+{
+	return 0;
+}
+
 #endif /* ELV_IOSCHED_FAIR_QUEUING */
 extern void *elv_get_sched_queue(struct request_queue *q, struct request *rq);
 extern void *elv_select_sched_queue(struct request_queue *q, int force);
-- 
1.6.0.1

[PATCH 11/20] io-controller: noop changes for hierarchical fair queuing

[Vivek Goyal]

This patch changes noop to use queue scheduling code from elevator layer.
One can go back to old noop by deselecting CONFIG_IOSCHED_NOOP_HIER.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/Kconfig.iosched |   11 +++++++++++
 block/noop-iosched.c  |    3 +++
 2 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index a91a807..9da6657 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -25,6 +25,17 @@ config IOSCHED_NOOP
 	  that do their own scheduling and require only minimal assistance from
 	  the kernel.
 
+config IOSCHED_NOOP_HIER
+	bool "Noop Hierarchical Scheduling support"
+	depends on IOSCHED_NOOP && CGROUPS
+	select ELV_FAIR_QUEUING
+	select GROUP_IOSCHED
+	default n
+	---help---
+	  Enable hierarhical scheduling in noop. In this mode noop keeps
+	  one IO queue per cgroup instead of a global queue. Elevator
+	  fair queuing logic ensures fairness among various queues.
+
 config IOSCHED_AS
 	tristate "Anticipatory I/O scheduler"
 	default y
diff --git a/block/noop-iosched.c b/block/noop-iosched.c
index d587832..73e571d 100644
--- a/block/noop-iosched.c
+++ b/block/noop-iosched.c
@@ -92,6 +92,9 @@ static struct elevator_type elevator_noop = {
 		.elevator_alloc_sched_queue_fn	= noop_alloc_noop_queue,
 		.elevator_free_sched_queue_fn	= noop_free_noop_queue,
 	},
+#ifdef CONFIG_IOSCHED_NOOP_HIER
+	.elevator_features = ELV_IOSCHED_NEED_FQ | ELV_IOSCHED_SINGLE_IOQ,
+#endif
 	.elevator_name = "noop",
 	.elevator_owner = THIS_MODULE,
 };
-- 
1.6.0.1

[PATCH 12/20] io-controller: deadline changes for hierarchical fair queuing

[Vivek Goyal]

This patch changes deadline to use queue scheduling code from elevator layer.
One can go back to old deadline by selecting CONFIG_IOSCHED_DEADLINE_HIER.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/Kconfig.iosched    |   11 +++++++++++
 block/deadline-iosched.c |    3 +++
 2 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 9da6657..3a9e7d7 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -55,6 +55,17 @@ config IOSCHED_DEADLINE
 	  a disk at any one time, its behaviour is almost identical to the
 	  anticipatory I/O scheduler and so is a good choice.
 
+config IOSCHED_DEADLINE_HIER
+	bool "Deadline Hierarchical Scheduling support"
+	depends on IOSCHED_DEADLINE && CGROUPS
+	select ELV_FAIR_QUEUING
+	select GROUP_IOSCHED
+	default n
+	---help---
+	  Enable hierarhical scheduling in deadline. In this mode deadline keeps
+	  one IO queue per cgroup instead of a global queue. Elevator
+	  fair queuing logic ensures fairness among various queues.
+
 config IOSCHED_CFQ
 	tristate "CFQ I/O scheduler"
 	select ELV_FAIR_QUEUING
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index 5e65041..27b77b9 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -477,6 +477,9 @@ static struct elevator_type iosched_deadline = {
 		.elevator_alloc_sched_queue_fn = deadline_alloc_deadline_queue,
 		.elevator_free_sched_queue_fn = deadline_free_deadline_queue,
 	},
+#ifdef CONFIG_IOSCHED_DEADLINE_HIER
+	.elevator_features = ELV_IOSCHED_NEED_FQ | ELV_IOSCHED_SINGLE_IOQ,
+#endif
 	.elevator_attrs = deadline_attrs,
 	.elevator_name = "deadline",
 	.elevator_owner = THIS_MODULE,
-- 
1.6.0.1

[PATCH 13/20] io-controller: anticipatory changes for hierarchical fair queuing

[Vivek Goyal]

This patch changes anticipatory scheduler to use queue scheduling code from
elevator layer.  One can go back to old as by deselecting
CONFIG_IOSCHED_AS_HIER.

TODO/Issues
===========
- AS anticipation logic does not seem to be sufficient to provide BW difference
  if two "dd" are going in two different cgroups. Needs to be looked into.

- AS write batch number of request adjustment happens upon every W->R batch
  direction switch. This automatic adjustment depends on how much time a
  read is taking after a W->R switch.

  This does not gel very well when hierarhical scheduling is enabled and
  every io group can have its separate read/write batch. Now if io group
  switching takes place it creates issues.

  Currently I have disabled write batch length adjustment in hierarchical
  mode.

- Currently performance seems to be very bad in hierarhical mode. Needs
  to be looked into.

- I think the whole idea of common layer doing time slice switching between
  queues and then queue in turn running timed batches is not very good. May
  be AS can maintain two queues (one for READS and other for WRITES) and let
  common layer do the time slice switching between these two queues.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/Kconfig.iosched    |   12 +++
 block/as-iosched.c       |  177 +++++++++++++++++++++++++++++++++++++++++++++-
 block/elevator-fq.c      |   72 ++++++++++++++++---
 include/linux/elevator.h |   16 ++++
 4 files changed, 264 insertions(+), 13 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 3a9e7d7..77fc786 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -45,6 +45,18 @@ config IOSCHED_AS
 	  deadline I/O scheduler, it can also be slower in some cases
 	  especially some database loads.
 
+config IOSCHED_AS_HIER
+	bool "Anticipatory Hierarchical Scheduling support"
+	depends on IOSCHED_AS && CGROUPS
+	select ELV_FAIR_QUEUING
+	select GROUP_IOSCHED
+	default n
+	---help---
+	  Enable hierarhical scheduling in anticipatory. In this mode
+	  anticipatory keeps one IO queue per cgroup instead of a global
+	  queue. Elevator fair queuing logic ensures fairness among various
+	  queues.
+
 config IOSCHED_DEADLINE
 	tristate "Deadline I/O scheduler"
 	default y
diff --git a/block/as-iosched.c b/block/as-iosched.c
index 7158e13..12aea88 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -84,6 +84,19 @@ struct as_queue {
 	struct list_head fifo_list[2];
 
 	struct request *next_rq[2];	/* next in sort order */
+
+	/*
+	 * If an as_queue is switched while a batch is running, then we
+	 * store the time left before current batch will expire
+	 */
+	long current_batch_time_left;
+
+	/*
+	 * batch data dir when queue was scheduled out. This will be used
+	 * to setup ad->batch_data_dir when queue is scheduled in.
+	 */
+	int saved_batch_data_dir;
+
 	unsigned long last_check_fifo[2];
 	int write_batch_count;		/* max # of reqs in a write batch */
 	int current_write_count;	/* how many requests left this batch */
@@ -150,6 +163,141 @@ static DEFINE_SPINLOCK(ioc_gone_lock);
 
 static void as_move_to_dispatch(struct as_data *ad, struct request *rq);
 static void as_antic_stop(struct as_data *ad);
+static inline int as_batch_expired(struct as_data *ad, struct as_queue *asq);
+
+#ifdef CONFIG_IOSCHED_AS_HIER
+static void as_save_batch_context(struct as_data *ad, struct as_queue *asq)
+{
+	/* Save batch data dir */
+	asq->saved_batch_data_dir = ad->batch_data_dir;
+
+	if (ad->changed_batch) {
+		/*
+		 * In case of force expire, we come here. Batch changeover
+		 * has been signalled but we are waiting for all the
+		 * request to finish from previous batch and then start
+		 * the new batch. Can't wait now. Mark that full batch time
+		 * needs to be allocated when this queue is scheduled again.
+		 */
+		asq->current_batch_time_left =
+				ad->batch_expire[ad->batch_data_dir];
+		ad->changed_batch = 0;
+		return;
+	}
+
+	if (ad->new_batch) {
+		/*
+		 * We should come here only when new_batch has been set
+		 * but no read request has been issued or if it is a forced
+		 * expiry.
+		 *
+		 * In both the cases, new batch has not started yet so
+		 * allocate full batch length for next scheduling opportunity.
+		 * We don't do write batch size adjustment in hierarchical
+		 * AS so that should not be an issue.
+		 */
+		asq->current_batch_time_left =
+				ad->batch_expire[ad->batch_data_dir];
+		ad->new_batch = 0;
+		return;
+	}
+
+	/* Save how much time is left before current batch expires */
+	if (as_batch_expired(ad, asq))
+		asq->current_batch_time_left = 0;
+	else {
+		asq->current_batch_time_left = ad->current_batch_expires
+							- jiffies;
+		BUG_ON((asq->current_batch_time_left) < 0);
+	}
+}
+
+/*
+ * FIXME: In original AS, read batch's time account started only after when
+ * first request had completed (if last batch was a write batch). But here
+ * we might be rescheduling a read batch right away irrespective of the fact
+ * of disk cache state.
+ */
+static void as_restore_batch_context(struct as_data *ad, struct as_queue *asq)
+{
+	/* Adjust the batch expire time */
+	if (asq->current_batch_time_left)
+		ad->current_batch_expires = jiffies +
+						asq->current_batch_time_left;
+	/* restore asq batch_data_dir info */
+	ad->batch_data_dir = asq->saved_batch_data_dir;
+}
+
+/* ioq has been set. */
+static void as_active_ioq_set(struct request_queue *q, void *sched_queue,
+				int coop)
+{
+	struct as_queue *asq = sched_queue;
+	struct as_data *ad = q->elevator->elevator_data;
+
+	as_restore_batch_context(ad, asq);
+}
+
+/*
+ * This is a notification from common layer that it wishes to expire this
+ * io queue. AS decides whether queue can be expired, if yes, it also
+ * saves the batch context.
+ */
+static int as_expire_ioq(struct request_queue *q, void *sched_queue,
+				int slice_expired, int force)
+{
+	struct as_data *ad = q->elevator->elevator_data;
+	int status = ad->antic_status;
+	struct as_queue *asq = sched_queue;
+
+	/* Forced expiry. We don't have a choice */
+	if (force) {
+		as_antic_stop(ad);
+		as_save_batch_context(ad, asq);
+		return 1;
+	}
+
+	/*
+	 * We are waiting for requests to finish from last
+	 * batch. Don't expire the queue now
+	 */
+	if (ad->changed_batch)
+		goto keep_queue;
+
+	/*
+	 * Wait for all requests from existing batch to finish before we
+	 * switch the queue. New queue might change the batch direction
+	 * and this is to be consistent with AS philosophy of not dispatching
+	 * new requests to underlying drive till requests from requests
+	 * from previous batch are completed.
+	 */
+	if (ad->nr_dispatched)
+		goto keep_queue;
+
+	/*
+	 * If AS anticipation is ON, stop it if slice expired, otherwise
+	 * keep the queue.
+	 */
+	if (status == ANTIC_WAIT_REQ || status == ANTIC_WAIT_NEXT) {
+		if (slice_expired)
+			as_antic_stop(ad);
+		else
+			/*
+			 * We are anticipating and time slice has not expired
+			 * so I would rather prefer waiting than break the
+			 * anticipation and expire the queue.
+			 */
+			goto keep_queue;
+	}
+
+	/* We are good to expire the queue. Save batch context */
+	as_save_batch_context(ad, asq);
+	return 1;
+
+keep_queue:
+	return 0;
+}
+#endif
 
 /*
  * IO Context helper functions
@@ -805,6 +953,7 @@ static void as_update_rq(struct as_data *ad, struct request *rq)
 	}
 }
 
+#ifndef CONFIG_IOSCHED_AS_HIER
 /*
  * Gathers timings and resizes the write batch automatically
  */
@@ -833,6 +982,7 @@ static void update_write_batch(struct as_data *ad)
 	if (asq->write_batch_count < 1)
 		asq->write_batch_count = 1;
 }
+#endif /* !CONFIG_IOSCHED_AS_HIER */
 
 /*
  * as_completed_request is to be called when a request has completed and
@@ -867,7 +1017,26 @@ static void as_completed_request(struct request_queue *q, struct request *rq)
 	 * and writeback caches
 	 */
 	if (ad->new_batch && ad->batch_data_dir == rq_is_sync(rq)) {
+#ifndef CONFIG_IOSCHED_AS_HIER
+		/*
+		 * Dynamic updation of write batch length is disabled
+		 * for hierarchical scheduling. It is difficult to do
+		 * accurate accounting when queue switch can take place
+		 * in the middle of the batch.
+		 *
+		 * Say, A, B are two groups. Following is the sequence of
+		 * events.
+		 *
+		 * Servicing Write batch of A.
+		 * Queue switch takes place and write batch of B starts.
+		 * Batch switch takes place and read batch of B starts.
+		 *
+		 * In above scenario, writes issued in write batch of A
+		 * might impact the write batch length of B. Which is not
+		 * good.
+		 */
 		update_write_batch(ad);
+#endif
 		ad->current_batch_expires = jiffies +
 				ad->batch_expire[BLK_RW_SYNC];
 		ad->new_batch = 0;
@@ -1516,8 +1685,14 @@ static struct elevator_type iosched_as = {
 		.trim =				as_trim,
 		.elevator_alloc_sched_queue_fn = as_alloc_as_queue,
 		.elevator_free_sched_queue_fn = as_free_as_queue,
+#ifdef CONFIG_IOSCHED_AS_HIER
+		.elevator_expire_ioq_fn =       as_expire_ioq,
+		.elevator_active_ioq_set_fn =   as_active_ioq_set,
 	},
-
+	.elevator_features = ELV_IOSCHED_NEED_FQ | ELV_IOSCHED_SINGLE_IOQ | ELV_IOSCHED_DONT_IDLE,
+#else
+	},
+#endif
 	.elevator_attrs = as_attrs,
 	.elevator_name = "anticipatory",
 	.elevator_owner = THIS_MODULE,
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 10787fd..cb38b1f 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -37,6 +37,8 @@ static inline struct io_queue *elv_close_cooperator(struct request_queue *q,
 struct io_entity *bfq_lookup_next_entity(struct io_sched_data *sd,
 						 int extract);
 void elv_release_ioq(struct elevator_queue *eq, struct io_queue **ioq_ptr);
+int elv_iosched_expire_ioq(struct request_queue *q, int slice_expired,
+					int force);
 
 static inline int elv_prio_slice(struct elv_fq_data *efqd, int sync,
 					unsigned short prio)
@@ -2185,6 +2187,9 @@ static void elv_ioq_update_idle_window(struct elevator_queue *eq,
 	int old_idle, enable_idle;
 	struct elv_fq_data *efqd = ioq->efqd;
 
+	/* If idling is disabled from ioscheduler, return */
+	if (!elv_gen_idling_enabled(eq))
+		return;
 	/*
 	 * Don't idle for async or idle io prio class
 	 */
@@ -2257,7 +2262,7 @@ int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq,
 		ioq->pid = current->pid;
 
 	ioq->sched_queue = sched_queue;
-	if (is_sync && !elv_ioq_class_idle(ioq))
+	if (elv_gen_idling_enabled(eq) && is_sync && !elv_ioq_class_idle(ioq))
 		elv_mark_ioq_idle_window(ioq);
 	bfq_init_entity(&ioq->entity, iog);
 	ioq->entity.budget = elv_prio_to_slice(efqd, ioq);
@@ -2674,16 +2679,18 @@ int elv_should_preempt(struct request_queue *q, struct io_queue *new_ioq,
 static void elv_preempt_queue(struct request_queue *q, struct io_queue *ioq)
 {
 	elv_log_ioq(&q->elevator->efqd, ioq, "preempt");
-	elv_ioq_slice_expired(q);
+	if (elv_iosched_expire_ioq(q, 0, 1)) {
+		elv_ioq_slice_expired(q);
 
-	/*
-	 * Put the new queue at the front of the of the current list,
-	 * so we know that it will be selected next.
-	 */
+		/*
+		 * Put the new queue at the front of the of the current list,
+		 * so we know that it will be selected next.
+		 */
 
-	elv_activate_ioq(ioq, 1);
-	elv_ioq_set_slice_end(ioq, 0);
-	elv_mark_ioq_slice_new(ioq);
+		elv_activate_ioq(ioq, 1);
+		elv_ioq_set_slice_end(ioq, 0);
+		elv_mark_ioq_slice_new(ioq);
+	}
 }
 
 void elv_ioq_request_add(struct request_queue *q, struct request *rq)
@@ -2863,11 +2870,44 @@ void elv_free_idle_ioq_list(struct elevator_queue *e)
 		elv_deactivate_ioq(efqd, ioq, 0);
 }
 
+/*
+ * Call iosched to let that elevator wants to expire the queue. This gives
+ * iosched like AS to say no (if it is in the middle of batch changeover or
+ * it is anticipating). it also allows iosched to do some house keeping
+ *
+ * force--> it is force dispatch and iosched must clean up its state. This
+ * 	     is useful when elevator wants to drain iosched and wants to
+ * 	     expire currnent active queue.
+ *
+ * slice_expired--> if 1, ioq slice expired hence elevator fair queuing logic
+ * 		    wants to switch the queue. iosched should allow that until
+ * 		    and unless necessary. Currently AS can deny the switch if
+ * 		    in the middle of batch switch.
+ *
+ * 		    if 0, time slice is still remaining. It is up to the iosched
+ * 		    whether it wants to wait on this queue or just want to
+ * 		    expire it and move on to next queue.
+ *
+ */
+int elv_iosched_expire_ioq(struct request_queue *q, int slice_expired,
+					int force)
+{
+	struct elevator_queue *e = q->elevator;
+	struct io_queue *ioq = elv_active_ioq(q->elevator);
+
+	if (e->ops->elevator_expire_ioq_fn)
+		return e->ops->elevator_expire_ioq_fn(q, ioq->sched_queue,
+							slice_expired, force);
+
+	return 1;
+}
+
 /* Common layer function to select the next queue to dispatch from */
 void *elv_fq_select_ioq(struct request_queue *q, int force)
 {
 	struct elv_fq_data *efqd = &q->elevator->efqd;
 	struct io_queue *new_ioq = NULL, *ioq = elv_active_ioq(q->elevator);
+	int slice_expired = 1;
 
 	if (!elv_nr_busy_ioq(q->elevator))
 		return NULL;
@@ -2962,8 +3002,14 @@ void *elv_fq_select_ioq(struct request_queue *q, int force)
 		goto keep_queue;
 	}
 
+	slice_expired = 0;
 expire:
-	elv_ioq_slice_expired(q);
+	if (elv_iosched_expire_ioq(q, slice_expired, force))
+		elv_ioq_slice_expired(q);
+	else {
+		ioq = NULL;
+		goto keep_queue;
+	}
 new_queue:
 	ioq = elv_set_active_ioq(q, new_ioq);
 keep_queue:
@@ -3128,7 +3174,8 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
 		}
 
 		if (elv_ioq_class_idle(ioq)) {
-			elv_ioq_slice_expired(q);
+			if (elv_iosched_expire_ioq(q, 1, 0))
+				elv_ioq_slice_expired(q);
 			goto done;
 		}
 
@@ -3149,7 +3196,8 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
 				elv_ioq_arm_slice_timer(q, 1);
 			} else {
 				/* Expire the queue */
-				elv_ioq_slice_expired(q);
+				if (elv_iosched_expire_ioq(q, 1, 0))
+					elv_ioq_slice_expired(q);
 			}
 		} else if (!ioq->nr_queued && !elv_close_cooperator(q, ioq, 1)
 			 && sync && !rq_noidle(rq))
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index ee38d08..cbfce0b 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -42,6 +42,7 @@ typedef int (elevator_update_idle_window_fn) (struct elevator_queue*, void*,
 						struct request*);
 typedef struct io_queue* (elevator_close_cooperator_fn) (struct request_queue*,
 						void*, int probe);
+typedef int (elevator_expire_ioq_fn) (struct request_queue*, void *, int, int);
 #endif
 
 struct elevator_ops
@@ -81,6 +82,7 @@ struct elevator_ops
 	elevator_should_preempt_fn *elevator_should_preempt_fn;
 	elevator_update_idle_window_fn *elevator_update_idle_window_fn;
 	elevator_close_cooperator_fn *elevator_close_cooperator_fn;
+	elevator_expire_ioq_fn  *elevator_expire_ioq_fn;
 #endif
 };
 
@@ -252,6 +254,9 @@ enum {
 /* iosched maintains only single ioq per group.*/
 #define ELV_IOSCHED_SINGLE_IOQ        2
 
+/* iosched does not need anticipation/idling logic support from common layer */
+#define ELV_IOSCHED_DONT_IDLE	4
+
 static inline int elv_iosched_fair_queuing_enabled(struct elevator_queue *e)
 {
 	return (e->elevator_type->elevator_features) & ELV_IOSCHED_NEED_FQ;
@@ -262,6 +267,12 @@ static inline int elv_iosched_single_ioq(struct elevator_queue *e)
 	return (e->elevator_type->elevator_features) & ELV_IOSCHED_SINGLE_IOQ;
 }
 
+/* returns 1 if elevator layer should enable its idling logic, 0 otherwise */
+static inline int elv_gen_idling_enabled(struct elevator_queue *e)
+{
+	return !((e->elevator_type->elevator_features) & ELV_IOSCHED_DONT_IDLE);
+}
+
 #else /* ELV_IOSCHED_FAIR_QUEUING */
 
 static inline int elv_iosched_fair_queuing_enabled(struct elevator_queue *e)
@@ -274,6 +285,11 @@ static inline int elv_iosched_single_ioq(struct elevator_queue *e)
 	return 0;
 }
 
+static inline int elv_gen_idling_enabled(struct elevator_queue *e)
+{
+	return 0;
+}
+
 #endif /* ELV_IOSCHED_FAIR_QUEUING */
 extern void *elv_get_sched_queue(struct request_queue *q, struct request *rq);
 extern void *elv_select_sched_queue(struct request_queue *q, int force);
-- 
1.6.0.1

[PATCH 14/20] blkio_cgroup patches from Ryo to track async bios.

[Vivek Goyal]

o blkio_cgroup patches from Ryo to track async bios.

o Fernando is also working on another IO tracking mechanism. We are not
  particular about any IO tracking mechanism. This patchset can make use
  of any mechanism which makes it to upstream. For the time being making
  use of Ryo's posting.

Based on 2.6.30-rc3-git3
Signed-off-by: Hirokazu Takahashi <taka-jCdQPDEk3idL9jVzuh4AOg@public.gmane.org>
Signed-off-by: Ryo Tsuruta <ryov-jCdQPDEk3idL9jVzuh4AOg@public.gmane.org>
---
 block/blk-ioc.c               |   37 +++---
 fs/buffer.c                   |    2 +
 fs/direct-io.c                |    2 +
 include/linux/biotrack.h      |   97 +++++++++++++
 include/linux/cgroup_subsys.h |    6 +
 include/linux/iocontext.h     |    1 +
 include/linux/memcontrol.h    |    6 +
 include/linux/mmzone.h        |    4 +-
 include/linux/page_cgroup.h   |   31 ++++-
 init/Kconfig                  |   15 ++
 mm/Makefile                   |    4 +-
 mm/biotrack.c                 |  300 +++++++++++++++++++++++++++++++++++++++++
 mm/bounce.c                   |    2 +
 mm/filemap.c                  |    2 +
 mm/memcontrol.c               |    6 +
 mm/memory.c                   |    5 +
 mm/page-writeback.c           |    2 +
 mm/page_cgroup.c              |   17 ++-
 mm/swap_state.c               |    2 +
 19 files changed, 511 insertions(+), 30 deletions(-)
 create mode 100644 include/linux/biotrack.h
 create mode 100644 mm/biotrack.c

diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 8f0f6cf..ccde40e 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -84,27 +84,32 @@ void exit_io_context(void)
 	}
 }
 
+void init_io_context(struct io_context *ioc)
+{
+	atomic_set(&ioc->refcount, 1);
+	atomic_set(&ioc->nr_tasks, 1);
+	spin_lock_init(&ioc->lock);
+	ioc->ioprio_changed = 0;
+	ioc->ioprio = 0;
+#ifdef CONFIG_GROUP_IOSCHED
+	ioc->cgroup_changed = 0;
+#endif
+	ioc->last_waited = jiffies; /* doesn't matter... */
+	ioc->nr_batch_requests = 0; /* because this is 0 */
+	ioc->aic = NULL;
+	INIT_RADIX_TREE(&ioc->radix_root, GFP_ATOMIC | __GFP_HIGH);
+	INIT_HLIST_HEAD(&ioc->cic_list);
+	ioc->ioc_data = NULL;
+}
+
+
 struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
 {
 	struct io_context *ret;
 
 	ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
-	if (ret) {
-		atomic_set(&ret->refcount, 1);
-		atomic_set(&ret->nr_tasks, 1);
-		spin_lock_init(&ret->lock);
-		ret->ioprio_changed = 0;
-		ret->ioprio = 0;
-#ifdef CONFIG_GROUP_IOSCHED
-		ret->cgroup_changed = 0;
-#endif
-		ret->last_waited = jiffies; /* doesn't matter... */
-		ret->nr_batch_requests = 0; /* because this is 0 */
-		ret->aic = NULL;
-		INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
-		INIT_HLIST_HEAD(&ret->cic_list);
-		ret->ioc_data = NULL;
-	}
+	if (ret)
+		init_io_context(ret);
 
 	return ret;
 }
diff --git a/fs/buffer.c b/fs/buffer.c
index aed2977..cae634d 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -36,6 +36,7 @@
 #include <linux/buffer_head.h>
 #include <linux/task_io_accounting_ops.h>
 #include <linux/bio.h>
+#include <linux/biotrack.h>
 #include <linux/notifier.h>
 #include <linux/cpu.h>
 #include <linux/bitops.h>
@@ -668,6 +669,7 @@ static void __set_page_dirty(struct page *page,
 	if (page->mapping) {	/* Race with truncate? */
 		WARN_ON_ONCE(warn && !PageUptodate(page));
 		account_page_dirtied(page, mapping);
+		blkio_cgroup_reset_owner_pagedirty(page, current->mm);
 		radix_tree_tag_set(&mapping->page_tree,
 				page_index(page), PAGECACHE_TAG_DIRTY);
 	}
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 05763bb..60b1a99 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -33,6 +33,7 @@
 #include <linux/err.h>
 #include <linux/blkdev.h>
 #include <linux/buffer_head.h>
+#include <linux/biotrack.h>
 #include <linux/rwsem.h>
 #include <linux/uio.h>
 #include <asm/atomic.h>
@@ -797,6 +798,7 @@ static int do_direct_IO(struct dio *dio)
 			ret = PTR_ERR(page);
 			goto out;
 		}
+		blkio_cgroup_reset_owner(page, current->mm);
 
 		while (block_in_page < blocks_per_page) {
 			unsigned offset_in_page = block_in_page << blkbits;
diff --git a/include/linux/biotrack.h b/include/linux/biotrack.h
new file mode 100644
index 0000000..741a8b5
--- /dev/null
+++ b/include/linux/biotrack.h
@@ -0,0 +1,97 @@
+#include <linux/cgroup.h>
+#include <linux/mm.h>
+#include <linux/page_cgroup.h>
+
+#ifndef _LINUX_BIOTRACK_H
+#define _LINUX_BIOTRACK_H
+
+#ifdef	CONFIG_CGROUP_BLKIO
+
+struct io_context;
+struct block_device;
+
+struct blkio_cgroup {
+	struct cgroup_subsys_state css;
+	struct io_context *io_context;	/* default io_context */
+/*	struct radix_tree_root io_context_root; per device io_context */
+};
+
+/**
+ * __init_blkio_page_cgroup() - initialize a blkio_page_cgroup
+ * @pc:		page_cgroup of the page
+ *
+ * Reset the owner ID of a page.
+ */
+static inline void __init_blkio_page_cgroup(struct page_cgroup *pc)
+{
+	lock_page_cgroup(pc);
+	page_cgroup_set_id(pc, 0);
+	unlock_page_cgroup(pc);
+}
+
+/**
+ * blkio_cgroup_disabled - check whether blkio_cgroup is disabled
+ *
+ * Returns true if disabled, false if not.
+ */
+static inline bool blkio_cgroup_disabled(void)
+{
+	if (blkio_cgroup_subsys.disabled)
+		return true;
+	return false;
+}
+
+extern void blkio_cgroup_set_owner(struct page *page, struct mm_struct *mm);
+extern void blkio_cgroup_reset_owner(struct page *page, struct mm_struct *mm);
+extern void blkio_cgroup_reset_owner_pagedirty(struct page *page,
+						 struct mm_struct *mm);
+extern void blkio_cgroup_copy_owner(struct page *page, struct page *opage);
+
+extern struct io_context *get_blkio_cgroup_iocontext(struct bio *bio);
+extern unsigned long get_blkio_cgroup_id(struct bio *bio);
+extern struct cgroup *blkio_cgroup_lookup(int id);
+
+#else	/* CONFIG_CGROUP_BIO */
+
+struct blkio_cgroup;
+
+static inline void __init_blkio_page_cgroup(struct page_cgroup *pc)
+{
+}
+
+static inline bool blkio_cgroup_disabled(void)
+{
+	return true;
+}
+
+static inline void blkio_cgroup_set_owner(struct page *page, struct mm_struct *mm)
+{
+}
+
+static inline void blkio_cgroup_reset_owner(struct page *page,
+						struct mm_struct *mm)
+{
+}
+
+static inline void blkio_cgroup_reset_owner_pagedirty(struct page *page,
+						struct mm_struct *mm)
+{
+}
+
+static inline void blkio_cgroup_copy_owner(struct page *page, struct page *opage)
+{
+}
+
+static inline struct io_context *get_blkio_cgroup_iocontext(struct bio *bio)
+{
+	return NULL;
+}
+
+static inline unsigned long get_blkio_cgroup_id(struct bio *bio)
+{
+	return 0;
+}
+
+#endif	/* CONFIG_CGROUP_BLKIO */
+
+#endif /* _LINUX_BIOTRACK_H */
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index 68ea6bd..f214e6e 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -43,6 +43,12 @@ SUBSYS(mem_cgroup)
 
 /* */
 
+#ifdef CONFIG_CGROUP_BLKIO
+SUBSYS(blkio_cgroup)
+#endif
+
+/* */
+
 #ifdef CONFIG_CGROUP_DEVICE
 SUBSYS(devices)
 #endif
diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h
index 271187f..1fe9d78 100644
--- a/include/linux/iocontext.h
+++ b/include/linux/iocontext.h
@@ -105,6 +105,7 @@ int put_io_context(struct io_context *ioc);
 void exit_io_context(void);
 struct io_context *get_io_context(gfp_t gfp_flags, int node);
 struct io_context *alloc_io_context(gfp_t gfp_flags, int node);
+void init_io_context(struct io_context *ioc);
 void copy_io_context(struct io_context **pdst, struct io_context **psrc);
 #else
 static inline void exit_io_context(void)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 25b9ca9..d74b462 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -37,6 +37,8 @@ struct mm_struct;
  * (Of course, if memcg does memory allocation in future, GFP_KERNEL is sane.)
  */
 
+extern void __init_mem_page_cgroup(struct page_cgroup *pc);
+
 extern int mem_cgroup_newpage_charge(struct page *page, struct mm_struct *mm,
 				gfp_t gfp_mask);
 /* for swap handling */
@@ -120,6 +122,10 @@ extern bool mem_cgroup_oom_called(struct task_struct *task);
 #else /* CONFIG_CGROUP_MEM_RES_CTLR */
 struct mem_cgroup;
 
+static inline void __init_mem_page_cgroup(struct page_cgroup *pc)
+{
+}
+
 static inline int mem_cgroup_newpage_charge(struct page *page,
 					struct mm_struct *mm, gfp_t gfp_mask)
 {
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index a47c879..14477cb 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -607,7 +607,7 @@ typedef struct pglist_data {
 	int nr_zones;
 #ifdef CONFIG_FLAT_NODE_MEM_MAP	/* means !SPARSEMEM */
 	struct page *node_mem_map;
-#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+#ifdef CONFIG_CGROUP_PAGE
 	struct page_cgroup *node_page_cgroup;
 #endif
 #endif
@@ -958,7 +958,7 @@ struct mem_section {
 
 	/* See declaration of similar field in struct zone */
 	unsigned long *pageblock_flags;
-#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+#ifdef CONFIG_CGROUP_PAGE
 	/*
 	 * If !SPARSEMEM, pgdat doesn't have page_cgroup pointer. We use
 	 * section. (see memcontrol.h/page_cgroup.h about this.)
diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
index 7339c7b..dd7f71c 100644
--- a/include/linux/page_cgroup.h
+++ b/include/linux/page_cgroup.h
@@ -1,7 +1,7 @@
 #ifndef __LINUX_PAGE_CGROUP_H
 #define __LINUX_PAGE_CGROUP_H
 
-#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+#ifdef CONFIG_CGROUP_PAGE
 #include <linux/bit_spinlock.h>
 /*
  * Page Cgroup can be considered as an extended mem_map.
@@ -12,9 +12,11 @@
  */
 struct page_cgroup {
 	unsigned long flags;
-	struct mem_cgroup *mem_cgroup;
 	struct page *page;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+	struct mem_cgroup *mem_cgroup;
 	struct list_head lru;		/* per cgroup LRU list */
+#endif
 };
 
 void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat);
@@ -71,7 +73,7 @@ static inline void unlock_page_cgroup(struct page_cgroup *pc)
 	bit_spin_unlock(PCG_LOCK, &pc->flags);
 }
 
-#else /* CONFIG_CGROUP_MEM_RES_CTLR */
+#else /* CONFIG_CGROUP_PAGE */
 struct page_cgroup;
 
 static inline void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)
@@ -122,4 +124,27 @@ static inline void swap_cgroup_swapoff(int type)
 }
 
 #endif
+
+#ifdef CONFIG_CGROUP_BLKIO
+/*
+ * use lower 16 bits for flags and reserve the rest for the page tracking id
+ */
+#define PCG_TRACKING_ID_SHIFT	(16)
+#define PCG_TRACKING_ID_BITS \
+	(8 * sizeof(unsigned long) - PCG_TRACKING_ID_SHIFT)
+
+/* NOTE: must be called with page_cgroup() held */
+static inline unsigned long page_cgroup_get_id(struct page_cgroup *pc)
+{
+	return pc->flags >> PCG_TRACKING_ID_SHIFT;
+}
+
+/* NOTE: must be called with page_cgroup() held */
+static inline void page_cgroup_set_id(struct page_cgroup *pc, unsigned long id)
+{
+	WARN_ON(id >= (1UL << PCG_TRACKING_ID_BITS));
+	pc->flags &= (1UL << PCG_TRACKING_ID_SHIFT) - 1;
+	pc->flags |= (unsigned long)(id << PCG_TRACKING_ID_SHIFT);
+}
+#endif
 #endif
diff --git a/init/Kconfig b/init/Kconfig
index 1a4686d..ee16d6f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -616,6 +616,21 @@ config GROUP_IOSCHED
 
 endif # CGROUPS
 
+config CGROUP_BLKIO
+	bool "Block I/O cgroup subsystem"
+	depends on CGROUPS && BLOCK
+	select MM_OWNER
+	help
+	  Provides a Resource Controller which enables to track the onwner
+	  of every Block I/O requests.
+	  The information this subsystem provides can be used from any
+	  kind of module such as dm-ioband device mapper modules or
+	  the cfq-scheduler.
+
+config CGROUP_PAGE
+	def_bool y
+	depends on CGROUP_MEM_RES_CTLR || CGROUP_BLKIO
+
 config MM_OWNER
 	bool
 
diff --git a/mm/Makefile b/mm/Makefile
index ec73c68..76c3436 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -37,4 +37,6 @@ else
 obj-$(CONFIG_SMP) += allocpercpu.o
 endif
 obj-$(CONFIG_QUICKLIST) += quicklist.o
-obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
+obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o
+obj-$(CONFIG_CGROUP_PAGE) += page_cgroup.o
+obj-$(CONFIG_CGROUP_BLKIO) += biotrack.o
diff --git a/mm/biotrack.c b/mm/biotrack.c
new file mode 100644
index 0000000..2baf1f0
--- /dev/null
+++ b/mm/biotrack.c
@@ -0,0 +1,300 @@
+/* biotrack.c - Block I/O Tracking
+ *
+ * Copyright (C) VA Linux Systems Japan, 2008-2009
+ * Developed by Hirokazu Takahashi <taka-jCdQPDEk3idL9jVzuh4AOg@public.gmane.org>
+ *
+ * Copyright (C) 2008 Andrea Righi <righi.andrea-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
+ * Use part of page_cgroup->flags to store blkio-cgroup ID.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/smp.h>
+#include <linux/bit_spinlock.h>
+#include <linux/blkdev.h>
+#include <linux/biotrack.h>
+#include <linux/mm_inline.h>
+
+/*
+ * The block I/O tracking mechanism is implemented on the cgroup memory
+ * controller framework. It helps to find the the owner of an I/O request
+ * because every I/O request has a target page and the owner of the page
+ * can be easily determined on the framework.
+ */
+
+/* Return the blkio_cgroup that associates with a cgroup. */
+static inline struct blkio_cgroup *cgroup_blkio(struct cgroup *cgrp)
+{
+	return container_of(cgroup_subsys_state(cgrp, blkio_cgroup_subsys_id),
+					struct blkio_cgroup, css);
+}
+
+/* Return the blkio_cgroup that associates with a process. */
+static inline struct blkio_cgroup *blkio_cgroup_from_task(struct task_struct *p)
+{
+	return container_of(task_subsys_state(p, blkio_cgroup_subsys_id),
+					struct blkio_cgroup, css);
+}
+
+static struct io_context default_blkio_io_context;
+static struct blkio_cgroup default_blkio_cgroup = {
+	.io_context	= &default_blkio_io_context,
+};
+
+/**
+ * blkio_cgroup_set_owner() - set the owner ID of a page.
+ * @page:	the page we want to tag
+ * @mm:		the mm_struct of a page owner
+ *
+ * Make a given page have the blkio-cgroup ID of the owner of this page.
+ */
+void blkio_cgroup_set_owner(struct page *page, struct mm_struct *mm)
+{
+	struct blkio_cgroup *biog;
+	struct page_cgroup *pc;
+	unsigned long id;
+
+	if (blkio_cgroup_disabled())
+		return;
+	pc = lookup_page_cgroup(page);
+	if (unlikely(!pc))
+		return;
+
+	lock_page_cgroup(pc);
+	page_cgroup_set_id(pc, 0);	/* 0: default blkio_cgroup id */
+	unlock_page_cgroup(pc);
+	if (!mm)
+		return;
+
+	rcu_read_lock();
+	biog = blkio_cgroup_from_task(rcu_dereference(mm->owner));
+	if (unlikely(!biog)) {
+		rcu_read_unlock();
+		return;
+	}
+	/*
+	 * css_get(&bio->css) isn't called to increment the reference
+	 * count of this blkio_cgroup "biog" so the css_id might turn
+	 * invalid even if this page is still active.
+	 * This approach is chosen to minimize the overhead.
+	 */
+	id = css_id(&biog->css);
+	rcu_read_unlock();
+	lock_page_cgroup(pc);
+	page_cgroup_set_id(pc, id);
+	unlock_page_cgroup(pc);
+}
+
+/**
+ * blkio_cgroup_reset_owner() - reset the owner ID of a page
+ * @page:	the page we want to tag
+ * @mm:		the mm_struct of a page owner
+ *
+ * Change the owner of a given page if necessary.
+ */
+void blkio_cgroup_reset_owner(struct page *page, struct mm_struct *mm)
+{
+	blkio_cgroup_set_owner(page, mm);
+}
+
+/**
+ * blkio_cgroup_reset_owner_pagedirty() - reset the owner ID of a pagecache page
+ * @page:	the page we want to tag
+ * @mm:		the mm_struct of a page owner
+ *
+ * Change the owner of a given page if the page is in the pagecache.
+ */
+void blkio_cgroup_reset_owner_pagedirty(struct page *page, struct mm_struct *mm)
+{
+	if (!page_is_file_cache(page))
+		return;
+	if (current->flags & PF_MEMALLOC)
+		return;
+
+	blkio_cgroup_reset_owner(page, mm);
+}
+
+/**
+ * blkio_cgroup_copy_owner() - copy the owner ID of a page into another page
+ * @npage:	the page where we want to copy the owner
+ * @opage:	the page from which we want to copy the ID
+ *
+ * Copy the owner ID of @opage into @npage.
+ */
+void blkio_cgroup_copy_owner(struct page *npage, struct page *opage)
+{
+	struct page_cgroup *npc, *opc;
+	unsigned long id;
+
+	if (blkio_cgroup_disabled())
+		return;
+	npc = lookup_page_cgroup(npage);
+	if (unlikely(!npc))
+		return;
+	opc = lookup_page_cgroup(opage);
+	if (unlikely(!opc))
+		return;
+
+	lock_page_cgroup(opc);
+	lock_page_cgroup(npc);
+	id = page_cgroup_get_id(opc);
+	page_cgroup_set_id(npc, id);
+	unlock_page_cgroup(npc);
+	unlock_page_cgroup(opc);
+}
+
+/* Create a new blkio-cgroup. */
+static struct cgroup_subsys_state *
+blkio_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cgrp)
+{
+	struct blkio_cgroup *biog;
+	struct io_context *ioc;
+
+	if (!cgrp->parent) {
+		biog = &default_blkio_cgroup;
+		init_io_context(biog->io_context);
+		/* Increment the referrence count not to be released ever. */
+		atomic_inc(&biog->io_context->refcount);
+		return &biog->css;
+	}
+
+	biog = kzalloc(sizeof(*biog), GFP_KERNEL);
+	if (!biog)
+		return ERR_PTR(-ENOMEM);
+	ioc = alloc_io_context(GFP_KERNEL, -1);
+	if (!ioc) {
+		kfree(biog);
+		return ERR_PTR(-ENOMEM);
+	}
+	biog->io_context = ioc;
+	return &biog->css;
+}
+
+/* Delete the blkio-cgroup. */
+static void blkio_cgroup_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
+{
+	struct blkio_cgroup *biog = cgroup_blkio(cgrp);
+
+	put_io_context(biog->io_context);
+	free_css_id(&blkio_cgroup_subsys, &biog->css);
+	kfree(biog);
+}
+
+/**
+ * get_blkio_cgroup_id() - determine the blkio-cgroup ID
+ * @bio:	the &struct bio which describes the I/O
+ *
+ * Returns the blkio-cgroup ID of a given bio. A return value zero
+ * means that the page associated with the bio belongs to default_blkio_cgroup.
+ */
+unsigned long get_blkio_cgroup_id(struct bio *bio)
+{
+	struct page_cgroup *pc;
+	struct page *page = bio_iovec_idx(bio, 0)->bv_page;
+	unsigned long id = 0;
+
+	pc = lookup_page_cgroup(page);
+	if (pc) {
+		lock_page_cgroup(pc);
+		id = page_cgroup_get_id(pc);
+		unlock_page_cgroup(pc);
+	}
+	return id;
+}
+
+/**
+ * get_blkio_cgroup_iocontext() - determine the blkio-cgroup iocontext
+ * @bio:	the &struct bio which describe the I/O
+ *
+ * Returns the iocontext of blkio-cgroup that issued a given bio.
+ */
+struct io_context *get_blkio_cgroup_iocontext(struct bio *bio)
+{
+	struct cgroup_subsys_state *css;
+	struct blkio_cgroup *biog;
+	struct io_context *ioc;
+	unsigned long id;
+
+	id = get_blkio_cgroup_id(bio);
+	rcu_read_lock();
+	css = css_lookup(&blkio_cgroup_subsys, id);
+	if (css)
+		biog = container_of(css, struct blkio_cgroup, css);
+	else
+		biog = &default_blkio_cgroup;
+	ioc = biog->io_context;	/* default io_context for this cgroup */
+	atomic_inc(&ioc->refcount);
+	rcu_read_unlock();
+	return ioc;
+}
+
+/**
+ * blkio_cgroup_lookup() - lookup a cgroup by blkio-cgroup ID
+ * @id:		blkio-cgroup ID
+ *
+ * Returns the cgroup associated with the specified ID, or NULL if lookup
+ * fails.
+ *
+ * Note:
+ * This function should be called under rcu_read_lock().
+ */
+struct cgroup *blkio_cgroup_lookup(int id)
+{
+	struct cgroup *cgrp;
+	struct cgroup_subsys_state *css;
+
+	if (blkio_cgroup_disabled())
+		return NULL;
+
+	css = css_lookup(&blkio_cgroup_subsys, id);
+	if (!css)
+		return NULL;
+	cgrp = css->cgroup;
+	return cgrp;
+}
+EXPORT_SYMBOL(get_blkio_cgroup_iocontext);
+EXPORT_SYMBOL(get_blkio_cgroup_id);
+EXPORT_SYMBOL(blkio_cgroup_lookup);
+
+static u64 blkio_id_read(struct cgroup *cgrp, struct cftype *cft)
+{
+	struct blkio_cgroup *biog = cgroup_blkio(cgrp);
+	unsigned long id;
+
+	rcu_read_lock();
+	id = css_id(&biog->css);
+	rcu_read_unlock();
+	return (u64)id;
+}
+
+
+static struct cftype blkio_files[] = {
+	{
+		.name = "id",
+		.read_u64 = blkio_id_read,
+	},
+};
+
+static int blkio_cgroup_populate(struct cgroup_subsys *ss, struct cgroup *cgrp)
+{
+	return cgroup_add_files(cgrp, ss, blkio_files,
+					ARRAY_SIZE(blkio_files));
+}
+
+struct cgroup_subsys blkio_cgroup_subsys = {
+	.name		= "blkio",
+	.create		= blkio_cgroup_create,
+	.destroy	= blkio_cgroup_destroy,
+	.populate	= blkio_cgroup_populate,
+	.subsys_id	= blkio_cgroup_subsys_id,
+	.use_id		= 1,
+};
diff --git a/mm/bounce.c b/mm/bounce.c
index e590272..875380c 100644
--- a/mm/bounce.c
+++ b/mm/bounce.c
@@ -14,6 +14,7 @@
 #include <linux/hash.h>
 #include <linux/highmem.h>
 #include <linux/blktrace_api.h>
+#include <linux/biotrack.h>
 #include <trace/block.h>
 #include <asm/tlbflush.h>
 
@@ -212,6 +213,7 @@ static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,
 		to->bv_len = from->bv_len;
 		to->bv_offset = from->bv_offset;
 		inc_zone_page_state(to->bv_page, NR_BOUNCE);
+		blkio_cgroup_copy_owner(to->bv_page, page);
 
 		if (rw == WRITE) {
 			char *vto, *vfrom;
diff --git a/mm/filemap.c b/mm/filemap.c
index 379ff0b..cee1438 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -33,6 +33,7 @@
 #include <linux/cpuset.h>
 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
 #include <linux/memcontrol.h>
+#include <linux/biotrack.h>
 #include <linux/mm_inline.h> /* for page_is_file_cache() */
 #include "internal.h"
 
@@ -464,6 +465,7 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 					gfp_mask & GFP_RECLAIM_MASK);
 	if (error)
 		goto out;
+	blkio_cgroup_set_owner(page, current->mm);
 
 	error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 	if (error == 0) {
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 01c2d8f..fa82121 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -128,6 +128,12 @@ struct mem_cgroup_lru_info {
 	struct mem_cgroup_per_node *nodeinfo[MAX_NUMNODES];
 };
 
+void __meminit __init_mem_page_cgroup(struct page_cgroup *pc)
+{
+	pc->mem_cgroup = NULL;
+	INIT_LIST_HEAD(&pc->lru);
+}
+
 /*
  * The memory controller data structure. The memory controller controls both
  * page cache and RSS per cgroup. We would eventually like to provide
diff --git a/mm/memory.c b/mm/memory.c
index 4126dd1..0da0e70 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -51,6 +51,7 @@
 #include <linux/init.h>
 #include <linux/writeback.h>
 #include <linux/memcontrol.h>
+#include <linux/biotrack.h>
 #include <linux/mmu_notifier.h>
 #include <linux/kallsyms.h>
 #include <linux/swapops.h>
@@ -2064,6 +2065,7 @@ gotten:
 		 */
 		ptep_clear_flush_notify(vma, address, page_table);
 		page_add_new_anon_rmap(new_page, vma, address);
+		blkio_cgroup_set_owner(new_page, mm);
 		set_pte_at(mm, address, page_table, entry);
 		update_mmu_cache(vma, address, entry);
 		if (old_page) {
@@ -2529,6 +2531,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	flush_icache_page(vma, page);
 	set_pte_at(mm, address, page_table, pte);
 	page_add_anon_rmap(page, vma, address);
+	blkio_cgroup_reset_owner(page, mm);
 	/* It's better to call commit-charge after rmap is established */
 	mem_cgroup_commit_charge_swapin(page, ptr);
 
@@ -2593,6 +2596,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		goto release;
 	inc_mm_counter(mm, anon_rss);
 	page_add_new_anon_rmap(page, vma, address);
+	blkio_cgroup_set_owner(page, mm);
 	set_pte_at(mm, address, page_table, entry);
 
 	/* No need to invalidate - it was non-present before */
@@ -2740,6 +2744,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		if (anon) {
 			inc_mm_counter(mm, anon_rss);
 			page_add_new_anon_rmap(page, vma, address);
+			blkio_cgroup_set_owner(page, mm);
 		} else {
 			inc_mm_counter(mm, file_rss);
 			page_add_file_rmap(page);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index bb553c3..3604c35 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -23,6 +23,7 @@
 #include <linux/init.h>
 #include <linux/backing-dev.h>
 #include <linux/task_io_accounting_ops.h>
+#include <linux/biotrack.h>
 #include <linux/blkdev.h>
 #include <linux/mpage.h>
 #include <linux/rmap.h>
@@ -1243,6 +1244,7 @@ int __set_page_dirty_nobuffers(struct page *page)
 			BUG_ON(mapping2 != mapping);
 			WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
 			account_page_dirtied(page, mapping);
+			blkio_cgroup_reset_owner_pagedirty(page, current->mm);
 			radix_tree_tag_set(&mapping->page_tree,
 				page_index(page), PAGECACHE_TAG_DIRTY);
 		}
diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 791905c..e143d04 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -9,14 +9,15 @@
 #include <linux/vmalloc.h>
 #include <linux/cgroup.h>
 #include <linux/swapops.h>
+#include <linux/biotrack.h>
 
 static void __meminit
 __init_page_cgroup(struct page_cgroup *pc, unsigned long pfn)
 {
 	pc->flags = 0;
-	pc->mem_cgroup = NULL;
 	pc->page = pfn_to_page(pfn);
-	INIT_LIST_HEAD(&pc->lru);
+	__init_mem_page_cgroup(pc);
+	__init_blkio_page_cgroup(pc);
 }
 static unsigned long total_usage;
 
@@ -74,7 +75,7 @@ void __init page_cgroup_init(void)
 
 	int nid, fail;
 
-	if (mem_cgroup_disabled())
+	if (mem_cgroup_disabled() && blkio_cgroup_disabled())
 		return;
 
 	for_each_online_node(nid)  {
@@ -83,12 +84,12 @@ void __init page_cgroup_init(void)
 			goto fail;
 	}
 	printk(KERN_INFO "allocated %ld bytes of page_cgroup\n", total_usage);
-	printk(KERN_INFO "please try cgroup_disable=memory option if you"
+	printk(KERN_INFO "please try cgroup_disable=memory,blkio option if you"
 	" don't want\n");
 	return;
 fail:
 	printk(KERN_CRIT "allocation of page_cgroup was failed.\n");
-	printk(KERN_CRIT "please try cgroup_disable=memory boot option\n");
+	printk(KERN_CRIT "please try cgroup_disable=memory,blkio boot options\n");
 	panic("Out of memory");
 }
 
@@ -248,7 +249,7 @@ void __init page_cgroup_init(void)
 	unsigned long pfn;
 	int fail = 0;
 
-	if (mem_cgroup_disabled())
+	if (mem_cgroup_disabled() && blkio_cgroup_disabled())
 		return;
 
 	for (pfn = 0; !fail && pfn < max_pfn; pfn += PAGES_PER_SECTION) {
@@ -263,8 +264,8 @@ void __init page_cgroup_init(void)
 		hotplug_memory_notifier(page_cgroup_callback, 0);
 	}
 	printk(KERN_INFO "allocated %ld bytes of page_cgroup\n", total_usage);
-	printk(KERN_INFO "please try cgroup_disable=memory option if you don't"
-	" want\n");
+	printk(KERN_INFO "please try cgroup_disable=memory,blkio option"
+	" if you don't want\n");
 }
 
 void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 3ecea98..a6a40e9 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -18,6 +18,7 @@
 #include <linux/pagevec.h>
 #include <linux/migrate.h>
 #include <linux/page_cgroup.h>
+#include <linux/biotrack.h>
 
 #include <asm/pgtable.h>
 
@@ -308,6 +309,7 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
 		 */
 		__set_page_locked(new_page);
 		SetPageSwapBacked(new_page);
+		blkio_cgroup_set_owner(new_page, current->mm);
 		err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
 		if (likely(!err)) {
 			/*
-- 
1.6.0.1

[PATCH 15/20] io-controller: map async requests to appropriate cgroup

[Vivek Goyal]

o So far we were assuming that a bio/rq belongs to the task who is submitting
  it. It did not hold good in case of async writes. This patch makes use of
  blkio_cgroup pataches to attribute the aysnc writes to right group instead
  of task submitting the bio.

o For sync requests, we continue to assume that io belongs to the task
  submitting it. Only in case of async requests, we make use of io tracking
  patches to track the owner cgroup.

o So far cfq always caches the async queue pointer. With async requests now
  not necessarily being tied to submitting task io context, caching the
  pointer will not help for async queues. This patch introduces a new config
  option CONFIG_TRACK_ASYNC_CONTEXT. If this option is not set, cfq retains
  old behavior where async queue pointer is cached in task context. If it
  is not set, async queue pointer is not cached and we take help of bio
  tracking patches to determine group bio belongs to and then map it to
  async queue of that group.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/Kconfig.iosched    |   16 +++++
 block/as-iosched.c       |    2 +-
 block/blk-core.c         |    7 +-
 block/cfq-iosched.c      |  152 ++++++++++++++++++++++++++++++++++++----------
 block/deadline-iosched.c |    2 +-
 block/elevator-fq.c      |  101 ++++++++++++++++++++++++++-----
 block/elevator-fq.h      |   23 ++++++-
 block/elevator.c         |   15 +++--
 include/linux/elevator.h |   21 ++++++-
 9 files changed, 272 insertions(+), 67 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 77fc786..0677099 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -124,6 +124,22 @@ config DEFAULT_IOSCHED
 	default "cfq" if DEFAULT_CFQ
 	default "noop" if DEFAULT_NOOP
 
+config TRACK_ASYNC_CONTEXT
+	bool "Determine async request context from bio"
+	depends on GROUP_IOSCHED
+	select CGROUP_BLKIO
+	default n
+	---help---
+	  Normally async request is attributed to the task submitting the
+	  request. With group ioscheduling, for accurate accounting of
+	  async writes, one needs to map the request to original task/cgroup
+	  which originated the request and not the submitter of the request.
+
+	  Currently there are generic io tracking patches to provide facility
+	  to map bio to original owner. If this option is set, for async
+	  request, original owner of the bio is decided by using io tracking
+	  patches otherwise we continue to attribute the request to the
+	  submitting thread.
 endmenu
 
 endif
diff --git a/block/as-iosched.c b/block/as-iosched.c
index 12aea88..afa554a 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -1412,7 +1412,7 @@ as_merge(struct request_queue *q, struct request **req, struct bio *bio)
 {
 	sector_t rb_key = bio->bi_sector + bio_sectors(bio);
 	struct request *__rq;
-	struct as_queue *asq = elv_get_sched_queue_current(q);
+	struct as_queue *asq = elv_get_sched_queue_bio(q, bio);
 
 	if (!asq)
 		return ELEVATOR_NO_MERGE;
diff --git a/block/blk-core.c b/block/blk-core.c
index c89883b..c77b5b2 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -643,7 +643,8 @@ static inline void blk_free_request(struct request_queue *q, struct request *rq)
 }
 
 static struct request *
-blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
+blk_alloc_request(struct request_queue *q, struct bio *bio, int flags, int priv,
+					gfp_t gfp_mask)
 {
 	struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
 
@@ -655,7 +656,7 @@ blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
 	rq->cmd_flags = flags | REQ_ALLOCED;
 
 	if (priv) {
-		if (unlikely(elv_set_request(q, rq, gfp_mask))) {
+		if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) {
 			mempool_free(rq, q->rq.rq_pool);
 			return NULL;
 		}
@@ -796,7 +797,7 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
 		rw_flags |= REQ_IO_STAT;
 	spin_unlock_irq(q->queue_lock);
 
-	rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
+	rq = blk_alloc_request(q, bio, rw_flags, priv, gfp_mask);
 	if (unlikely(!rq)) {
 		/*
 		 * Allocation failed presumably due to memory. Undo anything
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index f00110e..75ed566 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -161,8 +161,8 @@ CFQ_CFQQ_FNS(coop);
 	blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
 
 static void cfq_dispatch_insert(struct request_queue *, struct request *);
-static struct cfq_queue *cfq_get_queue(struct cfq_data *, int,
-				       struct io_context *, gfp_t);
+static struct cfq_queue *cfq_get_queue(struct cfq_data *, struct bio *bio,
+					int, struct io_context *, gfp_t);
 static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
 						struct io_context *);
 
@@ -172,22 +172,56 @@ static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
 	return cic->cfqq[!!is_sync];
 }
 
-static inline void cic_set_cfqq(struct cfq_io_context *cic,
-				struct cfq_queue *cfqq, int is_sync)
-{
-	cic->cfqq[!!is_sync] = cfqq;
-}
-
 /*
- * We regard a request as SYNC, if it's either a read or has the SYNC bit
- * set (in which case it could also be direct WRITE).
+ * Determine the cfq queue bio should go in. This is primarily used by
+ * front merge and allow merge functions.
+ *
+ * Currently this function takes the ioprio and iprio_class from task
+ * submitting async bio. Later save the task information in the page_cgroup
+ * and retrieve task's ioprio and class from there.
  */
-static inline int cfq_bio_sync(struct bio *bio)
+static struct cfq_queue *cic_bio_to_cfqq(struct cfq_data *cfqd,
+		struct cfq_io_context *cic, struct bio *bio, int is_sync)
 {
-	if (bio_data_dir(bio) == READ || bio_sync(bio))
-		return 1;
+	struct cfq_queue *cfqq = NULL;
 
-	return 0;
+	cfqq = cic_to_cfqq(cic, is_sync);
+
+#ifdef CONFIG_TRACK_ASYNC_CONTEXT
+	if (!cfqq && !is_sync) {
+		const int ioprio = task_ioprio(cic->ioc);
+		const int ioprio_class = task_ioprio_class(cic->ioc);
+		struct io_group *iog;
+		/*
+		 * async bio tracking is enabled and we are not caching
+		 * async queue pointer in cic.
+		 */
+		iog = io_get_io_group(cfqd->queue, bio, 0);
+		if (!iog) {
+			/*
+			 * May be this is first rq/bio and io group has not
+			 * been setup yet.
+			 */
+			return NULL;
+		}
+		return io_group_async_queue_prio(iog, ioprio_class, ioprio);
+	}
+#endif
+	return cfqq;
+}
+
+static inline void cic_set_cfqq(struct cfq_io_context *cic,
+				struct cfq_queue *cfqq, int is_sync)
+{
+#ifdef CONFIG_TRACK_ASYNC_CONTEXT
+	/*
+	 * Don't cache async queue pointer as now one io context might
+	 * be submitting async io for various different async queues
+	 */
+	if (!is_sync)
+		return;
+#endif
+	cic->cfqq[!!is_sync] = cfqq;
 }
 
 static inline struct io_group *cfqq_to_io_group(struct cfq_queue *cfqq)
@@ -505,7 +539,7 @@ cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
 	if (!cic)
 		return NULL;
 
-	cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
+	cfqq = cic_bio_to_cfqq(cfqd, cic, bio, elv_bio_sync(bio));
 	if (cfqq) {
 		sector_t sector = bio->bi_sector + bio_sectors(bio);
 
@@ -587,7 +621,7 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
 	/*
 	 * Disallow merge of a sync bio into an async request.
 	 */
-	if (cfq_bio_sync(bio) && !rq_is_sync(rq))
+	if (elv_bio_sync(bio) && !rq_is_sync(rq))
 		return 0;
 
 	/*
@@ -598,7 +632,7 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
 	if (!cic)
 		return 0;
 
-	cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
+	cfqq = cic_bio_to_cfqq(cfqd, cic, bio, elv_bio_sync(bio));
 	if (cfqq == RQ_CFQQ(rq))
 		return 1;
 
@@ -1206,14 +1240,28 @@ static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
 	spin_lock_irqsave(q->queue_lock, flags);
 
 	cfqq = cic->cfqq[BLK_RW_ASYNC];
+
 	if (cfqq) {
 		struct cfq_queue *new_cfqq;
-		new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
+
+		/*
+		 * Drop the reference to old queue unconditionally. Don't
+		 * worry whether new async prio queue has been allocated
+		 * or not.
+		 */
+		cic_set_cfqq(cic, NULL, BLK_RW_ASYNC);
+		cfq_put_queue(cfqq);
+
+		/*
+		 * Why to allocate new queue now? Will it not be automatically
+		 * allocated whenever another async request from same context
+		 * comes? Keeping it for the time being because existing cfq
+		 * code allocates the new queue immediately upon prio change
+		 */
+		new_cfqq = cfq_get_queue(cfqd, NULL, BLK_RW_ASYNC, cic->ioc,
 						GFP_ATOMIC);
-		if (new_cfqq) {
-			cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
-			cfq_put_queue(cfqq);
-		}
+		if (new_cfqq)
+			cic_set_cfqq(cic, new_cfqq, BLK_RW_ASYNC);
 	}
 
 	cfqq = cic->cfqq[BLK_RW_SYNC];
@@ -1246,7 +1294,7 @@ static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
 
 	spin_lock_irqsave(q->queue_lock, flags);
 
-	iog = io_get_io_group(q, 0);
+	iog = io_get_io_group(q, NULL, 0);
 
 	if (async_cfqq != NULL) {
 		__iog = cfqq_to_io_group(async_cfqq);
@@ -1274,7 +1322,7 @@ static void cfq_ioc_set_cgroup(struct io_context *ioc)
 #endif  /* CONFIG_IOSCHED_CFQ_HIER */
 
 static struct cfq_queue *
-cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
+cfq_find_alloc_queue(struct cfq_data *cfqd, struct bio *bio, int is_sync,
 				struct io_context *ioc, gfp_t gfp_mask)
 {
 	struct cfq_queue *cfqq, *new_cfqq = NULL;
@@ -1283,12 +1331,28 @@ cfq_find_alloc_queue(struct cfq_data *cfqd, int is_sync,
 	struct io_queue *ioq = NULL, *new_ioq = NULL;
 	struct io_group *iog = NULL;
 retry:
-	iog = io_get_io_group(q, 1);
+	iog = io_get_io_group(q, bio, 1);
 
 	cic = cfq_cic_lookup(cfqd, ioc);
 	/* cic always exists here */
 	cfqq = cic_to_cfqq(cic, is_sync);
 
+#ifdef CONFIG_TRACK_ASYNC_CONTEXT
+	if (!cfqq && !is_sync) {
+		const int ioprio = task_ioprio(cic->ioc);
+		const int ioprio_class = task_ioprio_class(cic->ioc);
+
+		/*
+		 * We have not cached async queue pointer as bio tracking
+		 * is enabled. Look into group async queue array using ioc
+		 * class and prio to see if somebody already allocated the
+		 * queue.
+		 */
+
+		cfqq = io_group_async_queue_prio(iog, ioprio_class, ioprio);
+	}
+#endif
+
 	if (!cfqq) {
 		if (new_cfqq) {
 			goto alloc_ioq;
@@ -1376,14 +1440,14 @@ out:
 }
 
 static struct cfq_queue *
-cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
-					gfp_t gfp_mask)
+cfq_get_queue(struct cfq_data *cfqd, struct bio *bio, int is_sync,
+		struct io_context *ioc, gfp_t gfp_mask)
 {
 	const int ioprio = task_ioprio(ioc);
 	const int ioprio_class = task_ioprio_class(ioc);
 	struct cfq_queue *async_cfqq = NULL;
 	struct cfq_queue *cfqq = NULL;
-	struct io_group *iog = io_get_io_group(cfqd->queue, 1);
+	struct io_group *iog = io_get_io_group(cfqd->queue, bio, 1);
 
 	if (!is_sync) {
 		async_cfqq = io_group_async_queue_prio(iog, ioprio_class,
@@ -1392,7 +1456,7 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
 	}
 
 	if (!cfqq) {
-		cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
+		cfqq = cfq_find_alloc_queue(cfqd, bio, is_sync, ioc, gfp_mask);
 		if (!cfqq)
 			return NULL;
 	}
@@ -1400,8 +1464,30 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct io_context *ioc,
 	if (!is_sync && !async_cfqq)
 		io_group_set_async_queue(iog, ioprio_class, ioprio, cfqq->ioq);
 
-	/* ioc reference */
+#ifdef CONFIG_TRACK_ASYNC_CONTEXT
+	/*
+	 * ioc reference. If async request queue/group is determined from the
+	 * original task/cgroup and not from submitter task, io context can
+	 * not cache the pointer to async queue and everytime a request comes,
+	 * it will be determined by going through the async queue array.
+	 *
+	 * This comes from the fact that we might be getting async requests
+	 * which belong to a different cgroup altogether than the cgroup
+	 * iocontext belongs to. And this thread might be submitting bios
+	 * from various cgroups. So every time async queue will be different
+	 * based on the cgroup of the bio/rq. Can't cache the async cfqq
+	 * pointer in cic.
+	 */
+	if (is_sync)
+		elv_get_ioq(cfqq->ioq);
+#else
+	/*
+	 * async requests are being attributed to task submitting
+	 * it, hence cic can cache async cfqq pointer. Take the
+	 * queue reference even for async queue.
+	 */
 	elv_get_ioq(cfqq->ioq);
+#endif
 	return cfqq;
 }
 
@@ -1795,7 +1881,8 @@ static void cfq_put_request(struct request *rq)
  * Allocate cfq data structures associated with this request.
  */
 static int
-cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
+cfq_set_request(struct request_queue *q, struct request *rq, struct bio *bio,
+				gfp_t gfp_mask)
 {
 	struct cfq_data *cfqd = q->elevator->elevator_data;
 	struct cfq_io_context *cic;
@@ -1815,7 +1902,8 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 
 	cfqq = cic_to_cfqq(cic, is_sync);
 	if (!cfqq) {
-		cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
+		cfqq = cfq_get_queue(cfqd, bio, is_sync, cic->ioc,
+						gfp_mask);
 
 		if (!cfqq)
 			goto queue_fail;
diff --git a/block/deadline-iosched.c b/block/deadline-iosched.c
index 27b77b9..87a46c2 100644
--- a/block/deadline-iosched.c
+++ b/block/deadline-iosched.c
@@ -133,7 +133,7 @@ deadline_merge(struct request_queue *q, struct request **req, struct bio *bio)
 	int ret;
 	struct deadline_queue *dq;
 
-	dq = elv_get_sched_queue_current(q);
+	dq = elv_get_sched_queue_bio(q, bio);
 	if (!dq)
 		return ELEVATOR_NO_MERGE;
 
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index cb38b1f..bb959f3 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -12,6 +12,7 @@
 #include "elevator-fq.h"
 #include <linux/blktrace_api.h>
 #include <linux/seq_file.h>
+#include <linux/biotrack.h>
 
 /* Values taken from cfq */
 const int elv_slice_sync = HZ / 10;
@@ -961,6 +962,9 @@ void bfq_init_entity(struct io_entity *entity, struct io_group *iog)
 
 struct io_cgroup *cgroup_to_io_cgroup(struct cgroup *cgroup)
 {
+	if (!cgroup)
+		return &io_root_cgroup;
+
 	return container_of(cgroup_subsys_state(cgroup, io_subsys_id),
 			    struct io_cgroup, css);
 }
@@ -1299,29 +1303,83 @@ struct io_group *io_find_alloc_group(struct request_queue *q,
 	return iog;
 }
 
+/* Map a bio to respective cgroup. Null return means, map it to root cgroup */
+static inline struct cgroup *get_cgroup_from_bio(struct bio *bio)
+{
+	unsigned long bio_cgroup_id;
+	struct cgroup *cgroup;
+
+	/* blk_get_request can reach here without passing a bio */
+	if (!bio)
+		return NULL;
+
+	if (bio_barrier(bio)) {
+		/*
+		 * Map barrier requests to root group. May be more special
+		 * bio cases should come here
+		 */
+		return NULL;
+	}
+
+#ifdef CONFIG_TRACK_ASYNC_CONTEXT
+	if (elv_bio_sync(bio)) {
+		/* sync io. Determine cgroup from submitting task context. */
+		cgroup = task_cgroup(current, io_subsys_id);
+		return cgroup;
+	}
+
+	/* Async io. Determine cgroup from with cgroup id stored in page */
+	bio_cgroup_id = get_blkio_cgroup_id(bio);
+
+	if (!bio_cgroup_id)
+		return NULL;
+
+	cgroup = blkio_cgroup_lookup(bio_cgroup_id);
+#else
+	cgroup = task_cgroup(current, io_subsys_id);
+#endif
+	return cgroup;
+}
+
 /*
- * Search for the io group current task belongs to. If create=1, then also
- * create the io group if it is not already there.
+ * Find the io group bio belongs to.
+ * If "create" is set, io group is created if it is not already present.
  */
-struct io_group *io_get_io_group(struct request_queue *q, int create)
+struct io_group *io_get_io_group(struct request_queue *q, struct bio *bio,
+					int create)
 {
 	struct cgroup *cgroup;
 	struct io_group *iog;
 	struct elv_fq_data *efqd = &q->elevator->efqd;
 
 	rcu_read_lock();
-	cgroup = task_cgroup(current, io_subsys_id);
-	iog = io_find_alloc_group(q, cgroup, efqd, create, NULL);
-	if (!iog) {
+
+	if (!bio)
+		cgroup = task_cgroup(current, io_subsys_id);
+	else
+		cgroup = get_cgroup_from_bio(bio);
+
+	if (!cgroup) {
 		if (create)
 			iog = efqd->root_group;
-		else
+		else {
 			/*
 			 * bio merge functions doing lookup don't want to
 			 * map bio to root group by default
 			 */
 			iog = NULL;
+		}
+		goto out;
 	}
+
+	iog = io_find_alloc_group(q, cgroup, efqd, create, bio);
+	if (!iog) {
+		if (create)
+			iog = efqd->root_group;
+		else
+			iog = NULL;
+	}
+out:
 	rcu_read_unlock();
 	return iog;
 }
@@ -1660,7 +1718,7 @@ int io_group_allow_merge(struct request *rq, struct bio *bio)
 		return 1;
 
 	/* Determine the io group of the bio submitting task */
-	iog = io_get_io_group(q, 0);
+	iog = io_get_io_group(q, bio, 0);
 	if (!iog) {
 		/* May be task belongs to a differet cgroup for which io
 		 * group has not been setup yet. */
@@ -1684,7 +1742,7 @@ int io_group_allow_merge(struct request *rq, struct bio *bio)
  * function is not invoked.
  */
 int elv_fq_set_request_ioq(struct request_queue *q, struct request *rq,
-					gfp_t gfp_mask)
+				struct bio *bio, gfp_t gfp_mask)
 {
 	struct elevator_queue *e = q->elevator;
 	unsigned long flags;
@@ -1700,7 +1758,7 @@ int elv_fq_set_request_ioq(struct request_queue *q, struct request *rq,
 
 retry:
 	/* Determine the io group request belongs to */
-	iog = io_get_io_group(q, 1);
+	iog = io_get_io_group(q, bio, 1);
 	BUG_ON(!iog);
 
 	/* Get the iosched queue */
@@ -1785,17 +1843,17 @@ queue_fail:
 }
 
 /*
- * Find out the io queue of current task. Optimization for single ioq
+ * Find out the io queue of bio belongs to. Optimization for single ioq
  * per io group io schedulers.
  */
-struct io_queue *elv_lookup_ioq_current(struct request_queue *q)
+struct io_queue *elv_lookup_ioq_bio(struct request_queue *q, struct bio *bio)
 {
 	struct io_group *iog;
 
 	/* Determine the io group and io queue of the bio submitting task */
-	iog = io_get_io_group(q, 0);
+	iog = io_get_io_group(q, bio, 0);
 	if (!iog) {
-		/* May be task belongs to a cgroup for which io group has
+		/* May be bio belongs to a cgroup for which io group has
 		 * not been setup yet. */
 		return NULL;
 	}
@@ -1852,7 +1910,13 @@ void io_free_root_group(struct elevator_queue *e)
 	kfree(iog);
 }
 
-struct io_group *io_get_io_group(struct request_queue *q, int create)
+struct io_group *io_get_io_group(struct request_queue *q, struct bio *bio,
+						int create)
+{
+	return q->elevator->efqd.root_group;
+}
+
+struct io_group *rq_iog(struct request_queue *q, struct request *rq)
 {
 	return q->elevator->efqd.root_group;
 }
@@ -3013,6 +3077,10 @@ expire:
 new_queue:
 	ioq = elv_set_active_ioq(q, new_ioq);
 keep_queue:
+	if (ioq)
+		elv_log_ioq(efqd, ioq, "select busy=%d qued=%d disp=%d",
+				elv_nr_busy_ioq(q->elevator), ioq->nr_queued,
+				elv_ioq_nr_dispatched(ioq));
 	return ioq;
 }
 
@@ -3148,7 +3216,8 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
 	ioq = rq->ioq;
 	iog = ioq_to_io_group(ioq);
 
-	elv_log_ioq(efqd, ioq, "complete");
+	elv_log_ioq(efqd, ioq, "complete drv=%d disp=%d", efqd->rq_in_driver,
+						elv_ioq_nr_dispatched(ioq));
 
 	elv_update_hw_tag(efqd);
 
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index d79dad7..48fb8f1 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -516,10 +516,12 @@ static inline bfq_weight_t iog_weight(struct io_group *iog)
 }
 
 extern int elv_fq_set_request_ioq(struct request_queue *q, struct request *rq,
-					gfp_t gfp_mask);
+					struct bio *bio, gfp_t gfp_mask);
 extern void elv_fq_unset_request_ioq(struct request_queue *q,
 					struct request *rq);
 extern struct io_queue *elv_lookup_ioq_current(struct request_queue *q);
+extern struct io_queue *elv_lookup_ioq_bio(struct request_queue *q,
+						struct bio *bio);
 
 /* Returns single ioq associated with the io group. */
 static inline struct io_queue *io_group_ioq(struct io_group *iog)
@@ -574,7 +576,7 @@ static inline void io_group_set_ioq(struct io_group *iog, struct io_queue *ioq)
 }
 
 static inline int elv_fq_set_request_ioq(struct request_queue *q,
-					struct request *rq, gfp_t gfp_mask)
+			struct request *rq, struct bio *bio, gfp_t gfp_mask)
 {
 	return 0;
 }
@@ -589,6 +591,12 @@ static inline struct io_queue *elv_lookup_ioq_current(struct request_queue *q)
 	return NULL;
 }
 
+static inline struct io_queue *elv_lookup_ioq_bio(struct request_queue *q,
+						struct bio *bio)
+{
+	return NULL;
+}
+
 #endif /* GROUP_IOSCHED */
 
 /* Functions used by blksysfs.c */
@@ -643,7 +651,8 @@ extern void *io_group_async_queue_prio(struct io_group *iog, int ioprio_class,
 					int ioprio);
 extern void io_group_set_async_queue(struct io_group *iog, int ioprio_class,
 					int ioprio, struct io_queue *ioq);
-extern struct io_group *io_get_io_group(struct request_queue *q, int create);
+extern struct io_group *io_get_io_group(struct request_queue *q,
+					struct bio *bio, int create);
 extern int elv_nr_busy_ioq(struct elevator_queue *e);
 extern int elv_nr_busy_rt_ioq(struct elevator_queue *e);
 extern struct io_queue *elv_alloc_ioq(struct request_queue *q, gfp_t gfp_mask);
@@ -703,7 +712,7 @@ static inline int io_group_allow_merge(struct request *rq, struct bio *bio)
 	return 1;
 }
 static inline int elv_fq_set_request_ioq(struct request_queue *q,
-					struct request *rq, gfp_t gfp_mask)
+			struct request *rq, struct bio *bio, gfp_t gfp_mask)
 {
 	return 0;
 }
@@ -718,5 +727,11 @@ static inline struct io_queue *elv_lookup_ioq_current(struct request_queue *q)
 	return NULL;
 }
 
+static inline struct io_queue *elv_lookup_ioq_bio(struct request_queue *q,
+						struct bio *bio)
+{
+	return NULL;
+}
+
 #endif /* CONFIG_ELV_FAIR_QUEUING */
 #endif /* _BFQ_SCHED_H */
diff --git a/block/elevator.c b/block/elevator.c
index 8b2206f..c693ac8 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -967,7 +967,8 @@ struct request *elv_former_request(struct request_queue *q, struct request *rq)
 	return NULL;
 }
 
-int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
+int elv_set_request(struct request_queue *q, struct request *rq,
+			struct bio *bio, gfp_t gfp_mask)
 {
 	struct elevator_queue *e = q->elevator;
 
@@ -976,10 +977,10 @@ int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 	 * ioq per io group
 	 */
 	if (elv_iosched_single_ioq(e))
-		return elv_fq_set_request_ioq(q, rq, gfp_mask);
+		return elv_fq_set_request_ioq(q, rq, bio, gfp_mask);
 
 	if (e->ops->elevator_set_req_fn)
-		return e->ops->elevator_set_req_fn(q, rq, gfp_mask);
+		return e->ops->elevator_set_req_fn(q, rq, bio, gfp_mask);
 
 	rq->elevator_private = NULL;
 	return 0;
@@ -1368,19 +1369,19 @@ void *elv_select_sched_queue(struct request_queue *q, int force)
 EXPORT_SYMBOL(elv_select_sched_queue);
 
 /*
- * Get the io scheduler queue pointer for current task.
+ * Get the io scheduler queue pointer for the group bio belongs to.
  *
  * If fair queuing is enabled, determine the io group of task and retrieve
  * the ioq pointer from that. This is used by only single queue ioschedulers
  * for retrieving the queue associated with the group to decide whether the
  * new bio can do a front merge or not.
  */
-void *elv_get_sched_queue_current(struct request_queue *q)
+void *elv_get_sched_queue_bio(struct request_queue *q, struct bio *bio)
 {
 	/* Fair queuing is not enabled. There is only one queue. */
 	if (!elv_iosched_fair_queuing_enabled(q->elevator))
 		return q->elevator->sched_queue;
 
-	return ioq_sched_queue(elv_lookup_ioq_current(q));
+	return ioq_sched_queue(elv_lookup_ioq_bio(q, bio));
 }
-EXPORT_SYMBOL(elv_get_sched_queue_current);
+EXPORT_SYMBOL(elv_get_sched_queue_bio);
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index cbfce0b..71e2d80 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -23,7 +23,7 @@ typedef struct request *(elevator_request_list_fn) (struct request_queue *, stru
 typedef void (elevator_completed_req_fn) (struct request_queue *, struct request *);
 typedef int (elevator_may_queue_fn) (struct request_queue *, int);
 
-typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, gfp_t);
+typedef int (elevator_set_req_fn) (struct request_queue *, struct request *, struct bio *bio, gfp_t);
 typedef void (elevator_put_req_fn) (struct request *);
 typedef void (elevator_activate_req_fn) (struct request_queue *, struct request *);
 typedef void (elevator_deactivate_req_fn) (struct request_queue *, struct request *);
@@ -150,7 +150,8 @@ extern void elv_unregister_queue(struct request_queue *q);
 extern int elv_may_queue(struct request_queue *, int);
 extern void elv_abort_queue(struct request_queue *);
 extern void elv_completed_request(struct request_queue *, struct request *);
-extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
+extern int elv_set_request(struct request_queue *, struct request *,
+					struct bio *bio, gfp_t);
 extern void elv_put_request(struct request_queue *, struct request *);
 extern void elv_drain_elevator(struct request_queue *);
 
@@ -293,6 +294,20 @@ static inline int elv_gen_idling_enabled(struct elevator_queue *e)
 #endif /* ELV_IOSCHED_FAIR_QUEUING */
 extern void *elv_get_sched_queue(struct request_queue *q, struct request *rq);
 extern void *elv_select_sched_queue(struct request_queue *q, int force);
-extern void *elv_get_sched_queue_current(struct request_queue *q);
+extern void *elv_get_sched_queue_bio(struct request_queue *q, struct bio *bio);
+
+/*
+ * This is equivalent of rq_is_sync()/cfq_bio_sync() function where we
+ * determine whether an rq/bio is sync or not. There are cases like during
+ * merging and during * request allocation, where we don't have rq but bio
+ * and needs to find out * if this bio will be considered as sync or async by
+ * elevator/iosched. This function is useful in such cases.
+ */
+static inline int elv_bio_sync(struct bio *bio)
+{
+	if ((bio_data_dir(bio) == READ) || bio_sync(bio))
+		return 1;
+	return 0;
+}
 #endif /* CONFIG_BLOCK */
 #endif
-- 
1.6.0.1

[PATCH 16/20] io-controller: IO group refcounting support

[Vivek Goyal]

o In the original BFQ patch once a cgroup is being deleted, it will clean
  up the associated io groups immediately and if there are any active io
  queues with that group, these will be moved to root group. This movement
  of queues is not good from fairness perspective as one can then create
  a cgroup, dump lots of IO and then delete the cgroup and then potentially
  get higher share. Apart from there are more issues hence it was felt that
  we need a io group refcounting mechanism also so that io group can be
  reclaimed asynchronously.

o This is V2 of the io group refcounting patch as implemented by Nauman
  and Divyesh. Currently keeping this patch as a separate one. Once it
  stablizes, will merge it with other patches instead of being a seprate
  one.

o Reference counting for io_group solves many problems, most of which occured
  when we tried to delete the cgroup. Earlier, ioqs were being moved out of
  cgroup to root cgroup. That is problematic in many ways, First, the pending
  requests in queues might get unfair service, and will also cause unfairness
  for other cgroups at the root level. This problem can become signficant if
  cgroups are created and destroyed relatively frequently. Second, moving
  queues to root cgroups was complicated and was causing many BUG_ON's to
  trigger. Third, there is a single io queue in AS, Deadline and Noop within a
  cgroup; and it does not make sense to move it to the root cgroup. The same
  is true of async queues.

o Requests already keep a reference on ioq, so queues keep a reference
  on cgroup. For async queues in CFQ, and single ioq in other
  schedulers, io_group also keeps are reference on io_queue. This
  reference on ioq is dropped when the queue is released
  (elv_release_ioq). So the queue can be freed.

  When a queue is released, it puts the reference to io_group and the
  io_group is released after all the queues are released. Child groups
  also take reference on parent groups, and release it when they are
  destroyed.

o Also we no longer need to maintain a seprate linked list of idle
  entities, which was maintained only to help release the ioq references
  during elevator switch. The code for releasing io_groups is reused for
  elevator switch, resulting in simpler and tight code.

o Reads of iocg->group_data are not always iocg->lock; so all the operations
  on that list are still protected by RCU. All modifications to
  iocg->group_data should always done under iocg->lock.

  Whenever iocg->lock and queue_lock can both be held, queue_lock should
  be held first. This avoids all deadlocks. In order to avoid race
  between cgroup deletion and elevator switch the following algorithm is
  used:

	- Cgroup deletion path holds iocg->lock and removes iog entry
	  to iocg->group_data list. Then it drops iocg->lock, holds
	  queue_lock and destroys iog. So in this path, we never hold
	  iocg->lock and queue_lock at the same time. Also, since we
	  remove iog from iocg->group_data under iocg->lock, we can't
	  race with elevator switch.

	- Elevator switch path does not remove iog from
	  iocg->group_data list directly. It first hold iocg->lock,
	  scans iocg->group_data again to see if iog is still there;
	  it removes iog only if it finds iog there. Otherwise, cgroup
	  deletion must have removed it from the list, and cgroup
	  deletion is responsible for removing iog.

  So the path which removes iog from iocg->group_data list does
  the final removal of iog by calling __io_destroy_group()
  function.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/cfq-iosched.c |   18 ++-
 block/elevator-fq.c |  405 +++++++++++++++++++++++++++++++++------------------
 block/elevator-fq.h |   38 +++++-
 3 files changed, 312 insertions(+), 149 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 75ed566..9b3c263 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1298,8 +1298,8 @@ static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
 
 	if (async_cfqq != NULL) {
 		__iog = cfqq_to_io_group(async_cfqq);
-
 		if (iog != __iog) {
+			/* cgroup changed, drop the reference to async queue */
 			cic_set_cfqq(cic, NULL, 0);
 			cfq_put_queue(async_cfqq);
 		}
@@ -1307,8 +1307,18 @@ static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
 
 	if (sync_cfqq != NULL) {
 		__iog = cfqq_to_io_group(sync_cfqq);
-		if (iog != __iog)
-			io_ioq_move(q->elevator, sync_cfqq->ioq, iog);
+
+		/*
+		 * Drop reference to sync queue. A new sync queue will
+		 * be assigned in new group upon arrival of a fresh request.
+		 * If old queue has got requests, those reuests will be
+		 * dispatched over a period of time and queue will be freed
+		 * automatically.
+		 */
+		if (iog != __iog) {
+			cic_set_cfqq(cic, NULL, 1);
+			cfq_put_queue(sync_cfqq);
+		}
 	}
 
 	spin_unlock_irqrestore(q->queue_lock, flags);
@@ -1425,6 +1435,8 @@ alloc_ioq:
 			elv_mark_ioq_sync(cfqq->ioq);
 		}
 		cfqq->pid = current->pid;
+		/* ioq reference on iog */
+		elv_get_iog(iog);
 		cfq_log_cfqq(cfqd, cfqq, "alloced");
 	}
 
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index bb959f3..9d36227 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -108,6 +108,12 @@ static inline void bfq_check_next_active(struct io_sched_data *sd,
 {
 	BUG_ON(sd->next_active != entity);
 }
+
+static inline int iog_deleting(struct io_group *iog)
+{
+	return iog->deleting;
+}
+
 #else /* GROUP_IOSCHED */
 #define for_each_entity(entity)	\
 	for (; entity != NULL; entity = NULL)
@@ -124,6 +130,12 @@ static inline void bfq_check_next_active(struct io_sched_data *sd,
 					 struct io_entity *entity)
 {
 }
+
+static inline int iog_deleting(struct io_group *iog)
+{
+	/* In flat mode, root cgroup can't be deleted. */
+	return 0;
+}
 #endif
 
 /*
@@ -224,7 +236,6 @@ static void bfq_idle_extract(struct io_service_tree *st,
 				struct io_entity *entity)
 {
 	struct rb_node *next;
-	struct io_queue *ioq = io_entity_to_ioq(entity);
 
 	BUG_ON(entity->tree != &st->idle);
 
@@ -239,10 +250,6 @@ static void bfq_idle_extract(struct io_service_tree *st,
 	}
 
 	bfq_extract(&st->idle, entity);
-
-	/* Delete queue from idle list */
-	if (ioq)
-		list_del(&ioq->queue_list);
 }
 
 /**
@@ -436,7 +443,6 @@ static void bfq_idle_insert(struct io_service_tree *st,
 {
 	struct io_entity *first_idle = st->first_idle;
 	struct io_entity *last_idle = st->last_idle;
-	struct io_queue *ioq = io_entity_to_ioq(entity);
 
 	if (first_idle == NULL || bfq_gt(first_idle->finish, entity->finish))
 		st->first_idle = entity;
@@ -444,10 +450,6 @@ static void bfq_idle_insert(struct io_service_tree *st,
 		st->last_idle = entity;
 
 	bfq_insert(&st->idle, entity);
-
-	/* Add this queue to idle list */
-	if (ioq)
-		list_add(&ioq->queue_list, &ioq->efqd->idle_list);
 }
 
 /**
@@ -723,8 +725,26 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
 void bfq_deactivate_entity(struct io_entity *entity, int requeue)
 {
 	struct io_sched_data *sd;
+	struct io_group *iog;
 	struct io_entity *parent;
 
+	iog = container_of(entity->sched_data, struct io_group, sched_data);
+
+	/*
+	 * Hold a reference to entity's iog until we are done. This function
+	 * travels the hierarchy and we don't want to free up the group yet
+	 * while we are traversing the hiearchy. It is possible that this
+	 * group's cgroup has been removed hence cgroup reference is gone.
+	 * If this entity was active entity, then its group will not be on
+	 * any of the trees and it will be freed up the moment queue is
+	 * freed up in __bfq_deactivate_entity().
+	 *
+	 * Hence, hold a reference, deactivate the hierarhcy of entities and
+	 * then drop the reference which should free up the whole chain of
+	 * groups.
+	 */
+	elv_get_iog(iog);
+
 	for_each_entity_safe(entity, parent) {
 		sd = entity->sched_data;
 
@@ -736,21 +756,28 @@ void bfq_deactivate_entity(struct io_entity *entity, int requeue)
 			 */
 			break;
 
-		if (sd->next_active != NULL)
+		if (sd->next_active != NULL) {
 			/*
 			 * The parent entity is still backlogged and
 			 * the budgets on the path towards the root
 			 * need to be updated.
 			 */
+			elv_put_iog(iog);
 			goto update;
+		}
 
 		/*
 		 * If we reach there the parent is no more backlogged and
 		 * we want to propagate the dequeue upwards.
+		 *
+		 * If entity's group has been marked for deletion, don't
+		 * requeue the group in idle tree so that it can be freed.
 		 */
-		requeue = 1;
+		if (!iog_deleting(iog))
+			requeue = 1;
 	}
 
+	elv_put_iog(iog);
 	return;
 
 update:
@@ -1008,6 +1035,9 @@ void io_group_set_parent(struct io_group *iog, struct io_group *parent)
 	entity = &iog->entity;
 	entity->parent = parent->my_entity;
 	entity->sched_data = &parent->sched_data;
+	if (entity->parent)
+		/* Child group reference on parent group. */
+		elv_get_iog(parent);
 }
 
 /**
@@ -1176,12 +1206,24 @@ struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
 
 		io_group_init_entity(iocg, iog);
 		iog->my_entity = &iog->entity;
+		atomic_set(&iog->ref, 0);
+		iog->deleting = 0;
+
+		/*
+		 * Take the initial reference that will be released on destroy
+		 * This can be thought of a joint reference by cgroup and
+		 * elevator which will be dropped by either elevator exit
+		 * or cgroup deletion path depending on who is exiting first.
+		 */
+		elv_get_iog(iog);
 
 		if (bio) {
 			struct gendisk *disk = bio->bi_bdev->bd_disk;
 			iog->dev = MKDEV(disk->major, disk->first_minor);
 		}
 
+		iog->iocg_id = css_id(&iocg->css);
+
 		if (leaf == NULL) {
 			leaf = iog;
 			prev = leaf;
@@ -1292,14 +1334,24 @@ struct io_group *io_find_alloc_group(struct request_queue *q,
 	/* Note: Use efqd as key */
 	void *key = efqd;
 
+	/*
+	 * Take a refenrece to css object. Don't want to map a bio to
+	 * a group if it has been marked for deletion
+	 */
+
+	if (!css_tryget(&iocg->css))
+		return iog;
+
 	iog = io_cgroup_lookup_group(iocg, key);
 	if (iog != NULL || !create)
-		return iog;
+		goto end;
 
 	iog = io_group_chain_alloc(q, key, cgroup, bio);
 	if (iog != NULL)
 		io_group_chain_link(q, key, cgroup, iog, efqd);
 
+end:
+	css_put(&iocg->css);
 	return iog;
 }
 
@@ -1344,6 +1396,13 @@ static inline struct cgroup *get_cgroup_from_bio(struct bio *bio)
 /*
  * Find the io group bio belongs to.
  * If "create" is set, io group is created if it is not already present.
+ *
+ * Note: This function should be called with queue lock held. It returns
+ * a pointer to io group without taking any reference. That group will
+ * be around as long as queue lock is not dropped (as group reclaim code
+ * needs to get hold of queue lock). So if somebody needs to use group
+ * pointer even after dropping queue lock, take a reference to the group
+ * before dropping queue lock.
  */
 struct io_group *io_get_io_group(struct request_queue *q, struct bio *bio,
 					int create)
@@ -1352,6 +1411,8 @@ struct io_group *io_get_io_group(struct request_queue *q, struct bio *bio,
 	struct io_group *iog;
 	struct elv_fq_data *efqd = &q->elevator->efqd;
 
+	assert_spin_locked(q->queue_lock);
+
 	rcu_read_lock();
 
 	if (!bio)
@@ -1390,13 +1451,20 @@ void io_free_root_group(struct elevator_queue *e)
 	struct io_cgroup *iocg = &io_root_cgroup;
 	struct elv_fq_data *efqd = &e->efqd;
 	struct io_group *iog = efqd->root_group;
+	struct io_service_tree *st;
+	int i;
 
 	BUG_ON(!iog);
 	spin_lock_irq(&iocg->lock);
 	hlist_del_rcu(&iog->group_node);
 	spin_unlock_irq(&iocg->lock);
+
+	for (i = 0; i < IO_IOPRIO_CLASSES; i++) {
+		st = iog->sched_data.service_tree + i;
+		io_flush_idle_tree(st);
+	}
 	io_put_io_group_queues(e, iog);
-	kfree(iog);
+	elv_put_iog(iog);
 }
 
 struct io_group *io_alloc_root_group(struct request_queue *q,
@@ -1410,6 +1478,7 @@ struct io_group *io_alloc_root_group(struct request_queue *q,
 	if (iog == NULL)
 		return NULL;
 
+	elv_get_iog(iog);
 	iog->entity.parent = NULL;
 	for (i = 0; i < IO_IOPRIO_CLASSES; i++)
 		iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
@@ -1418,6 +1487,7 @@ struct io_group *io_alloc_root_group(struct request_queue *q,
 	spin_lock_irq(&iocg->lock);
 	rcu_assign_pointer(iog->key, key);
 	hlist_add_head_rcu(&iog->group_node, &iocg->group_data);
+	iog->iocg_id = css_id(&iocg->css);
 	spin_unlock_irq(&iocg->lock);
 
 	return iog;
@@ -1513,106 +1583,149 @@ void iocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
 }
 
 /*
- * Move the queue to the root group if it is active. This is needed when
- * a cgroup is being deleted and all the IO is not done yet. This is not
- * very good scheme as a user might get unfair share. This needs to be
- * fixed.
+ * This cleanup function does the last bit of things to destroy cgroup.
+ * It should only get called after io_destroy_group has been invoked.
  */
-void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
-				struct io_group *iog)
+void io_group_cleanup(struct io_group *iog)
 {
-	int busy, resume;
-	struct io_entity *entity = &ioq->entity;
-	struct elv_fq_data *efqd = &e->efqd;
-	struct io_service_tree *st = io_entity_service_tree(entity);
-
-	busy = elv_ioq_busy(ioq);
-	resume = !!ioq->nr_queued;
+	struct io_service_tree *st;
+	struct io_entity *entity = iog->my_entity;
+	int i;
 
-	BUG_ON(resume && !entity->on_st);
-	BUG_ON(busy && !resume && entity->on_st && ioq != efqd->active_queue);
+	for (i = 0; i < IO_IOPRIO_CLASSES; i++) {
+		st = iog->sched_data.service_tree + i;
 
-	/*
-	 * We could be moving an queue which is on idle tree of previous group
-	 * What to do? I guess anyway this queue does not have any requests.
-	 * just forget the entity and free up from idle tree.
-	 *
-	 * This needs cleanup. Hackish.
-	 */
-	if (entity->tree == &st->idle) {
-		BUG_ON(atomic_read(&ioq->ref) < 2);
-		bfq_put_idle_entity(st, entity);
+		BUG_ON(!RB_EMPTY_ROOT(&st->active));
+		BUG_ON(!RB_EMPTY_ROOT(&st->idle));
+		BUG_ON(st->wsum != 0);
 	}
 
-	if (busy) {
-		BUG_ON(atomic_read(&ioq->ref) < 2);
+	BUG_ON(iog->sched_data.next_active != NULL);
+	BUG_ON(iog->sched_data.active_entity != NULL);
+	BUG_ON(entity != NULL && entity->tree != NULL);
 
-		if (!resume)
-			elv_del_ioq_busy(e, ioq, 0);
-		else
-			elv_deactivate_ioq(efqd, ioq, 0);
+	iog->iocg_id = 0;
+	kfree(iog);
+}
+
+void elv_put_iog(struct io_group *iog)
+{
+	struct io_group *parent = NULL;
+	struct io_entity *entity;
+
+	BUG_ON(!iog);
+
+	entity = iog->my_entity;
+
+	BUG_ON(atomic_read(&iog->ref) <= 0);
+	if (!atomic_dec_and_test(&iog->ref))
+		return;
+
+	if (entity)
+		parent = container_of(iog->my_entity->parent,
+					struct io_group, entity);
+
+	io_group_cleanup(iog);
+
+	if (parent)
+		elv_put_iog(parent);
+}
+EXPORT_SYMBOL(elv_put_iog);
+
+/*
+ * check whether a given group has got any active entities on any of the
+ * service tree.
+ */
+static inline int io_group_has_active_entities(struct io_group *iog)
+{
+	int i;
+	struct io_service_tree *st;
+
+	for (i = 0; i < IO_IOPRIO_CLASSES; i++) {
+		st = iog->sched_data.service_tree + i;
+		if (!RB_EMPTY_ROOT(&st->active))
+			return 1;
 	}
 
 	/*
-	 * Here we use a reference to bfqg.  We don't need a refcounter
-	 * as the cgroup reference will not be dropped, so that its
-	 * destroy() callback will not be invoked.
+	 * Also check there are no active entities being served which are
+	 * not on active tree
 	 */
-	entity->parent = iog->my_entity;
-	entity->sched_data = &iog->sched_data;
 
-	if (busy && resume)
-		elv_activate_ioq(ioq, 0);
+	if (iog->sched_data.active_entity)
+		return 1;
+
+	return 0;
 }
-EXPORT_SYMBOL(io_ioq_move);
 
+/*
+ * After the group is destroyed, no new sync IO should come to the group.
+ * It might still have pending IOs in some busy queues. It should be able to
+ * send those IOs down to the disk. The async IOs (due to dirty page writeback)
+ * would go in the root group queues after this, as the group does not exist
+ * anymore.
+ */
 static void __io_destroy_group(struct elv_fq_data *efqd, struct io_group *iog)
 {
 	struct elevator_queue *eq;
-	struct io_entity *entity = iog->my_entity;
 	struct io_service_tree *st;
 	int i;
 
+	BUG_ON(iog->my_entity == NULL);
+
+	/*
+	 * Mark io group for deletion so that no new entry goes in
+	 * idle tree. Any active queue will be removed from active
+	 * tree and not put in to idle tree.
+	 */
+	iog->deleting = 1;
+
+	/* We flush idle tree now, and don't put things in there any more. */
+	for (i = 0; i < IO_IOPRIO_CLASSES; i++) {
+		st = iog->sched_data.service_tree + i;
+
+		io_flush_idle_tree(st);
+	}
+
 	eq = container_of(efqd, struct elevator_queue, efqd);
 	hlist_del(&iog->elv_data_node);
-	__bfq_deactivate_entity(entity, 0);
 	io_put_io_group_queues(eq, iog);
 
-	for (i = 0; i < IO_IOPRIO_CLASSES; i++) {
-		st = iog->sched_data.service_tree + i;
+	/*
+	 * We can come here either through cgroup deletion path or through
+	 * elevator exit path. If we come here through cgroup deletion path
+	 * check if io group has any active entities or not. If not, then
+	 * deactivate this io group to make sure it is removed from idle
+	 * tree it might have been on. If this group was on idle tree, then
+	 * this probably will be the last reference and group will be
+	 * freed upon putting the reference down.
+	 */
 
+	if (!io_group_has_active_entities(iog)) {
 		/*
-		 * The idle tree may still contain bfq_queues belonging
-		 * to exited task because they never migrated to a different
-		 * cgroup from the one being destroyed now.  Noone else
-		 * can access them so it's safe to act without any lock.
+		 * io group does not have any active entites. Because this
+		 * group has been decoupled from io_cgroup list and this
+		 * cgroup is being deleted, this group should not receive
+		 * any new IO. Hence it should be safe to deactivate this
+		 * io group and remove from the scheduling tree.
 		 */
-		io_flush_idle_tree(st);
-
-		BUG_ON(!RB_EMPTY_ROOT(&st->active));
-		BUG_ON(!RB_EMPTY_ROOT(&st->idle));
+		__bfq_deactivate_entity(iog->my_entity, 0);
 	}
 
-	BUG_ON(iog->sched_data.next_active != NULL);
-	BUG_ON(iog->sched_data.active_entity != NULL);
-	BUG_ON(entity->tree != NULL);
+	/*
+	 * Put the reference taken at the time of creation so that when all
+	 * queues are gone, cgroup can be destroyed.
+	 */
+	elv_put_iog(iog);
 }
 
-/**
- * bfq_destroy_group - destroy @bfqg.
- * @bgrp: the bfqio_cgroup containing @bfqg.
- * @bfqg: the group being destroyed.
- *
- * Destroy @bfqg, making sure that it is not referenced from its parent.
- */
-static void io_destroy_group(struct io_cgroup *iocg, struct io_group *iog)
+void iocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 {
-	struct elv_fq_data *efqd = NULL;
+	struct io_cgroup *iocg = cgroup_to_io_cgroup(cgroup);
+	struct io_group *iog;
+	struct elv_fq_data *efqd;
 	unsigned long uninitialized_var(flags);
 
-	/* Remove io group from cgroup list */
-	hlist_del(&iog->group_node);
-
 	/*
 	 * io groups are linked in two lists. One list is maintained
 	 * in elevator (efqd->group_list) and other is maintained
@@ -1622,52 +1735,78 @@ static void io_destroy_group(struct io_cgroup *iocg, struct io_group *iog)
 	 * exiting and both might try to cleanup the same io group
 	 * so need to be little careful.
 	 *
-	 * Following code first accesses efqd under RCU to make sure
-	 * iog->key is pointing to valid efqd and then takes the
-	 * associated queue lock. After gettting the queue lock it
-	 * again checks whether elevator exit path had alreday got
-	 * hold of io group (iog->key == NULL). If yes, it does not
-	 * try to free up async queues again or flush the idle tree.
+	 * (iocg->group_data) is protected by iocg->lock. To avoid deadlock,
+	 * we can't hold the queue lock while holding iocg->lock. So we first
+	 * remove iog from iocg->group_data under iocg->lock. Whoever removes
+	 * iog from iocg->group_data should call __io_destroy_group to remove
+	 * iog.
 	 */
 
 	rcu_read_lock();
-	efqd = rcu_dereference(iog->key);
-	if (efqd != NULL) {
-		spin_lock_irqsave(efqd->queue->queue_lock, flags);
-		if (iog->key == efqd)
-			__io_destroy_group(efqd, iog);
-		spin_unlock_irqrestore(efqd->queue->queue_lock, flags);
+
+remove_entry:
+	spin_lock_irqsave(&iocg->lock, flags);
+
+	if (hlist_empty(&iocg->group_data)) {
+		spin_unlock_irqrestore(&iocg->lock, flags);
+		goto done;
 	}
-	rcu_read_unlock();
+	iog = hlist_entry(iocg->group_data.first, struct io_group,
+			  group_node);
+	efqd = rcu_dereference(iog->key);
+	hlist_del_rcu(&iog->group_node);
+	spin_unlock_irqrestore(&iocg->lock, flags);
 
-	/*
-	 * No need to defer the kfree() to the end of the RCU grace
-	 * period: we are called from the destroy() callback of our
-	 * cgroup, so we can be sure that noone is a) still using
-	 * this cgroup or b) doing lookups in it.
-	 */
-	kfree(iog);
+	spin_lock_irqsave(efqd->queue->queue_lock, flags);
+	__io_destroy_group(efqd, iog);
+	spin_unlock_irqrestore(efqd->queue->queue_lock, flags);
+	goto remove_entry;
+
+done:
+	free_css_id(&io_subsys, &iocg->css);
+	rcu_read_unlock();
+	BUG_ON(!hlist_empty(&iocg->group_data));
+	kfree(iocg);
 }
 
-void iocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
+/*
+ * This functions checks if iog is still in iocg->group_data, and removes it.
+ * If iog is not in that list, then cgroup destroy path has removed it, and
+ * we do not need to remove it.
+ */
+void io_group_check_and_destroy(struct elv_fq_data *efqd, struct io_group *iog)
 {
-	struct io_cgroup *iocg = cgroup_to_io_cgroup(cgroup);
-	struct hlist_node *n, *tmp;
-	struct io_group *iog;
+	struct io_cgroup *iocg;
+	unsigned short id = iog->iocg_id;
+	struct hlist_node *n;
+	struct io_group *__iog;
+	unsigned long flags;
+	struct cgroup_subsys_state *css;
 
-	/*
-	 * Since we are destroying the cgroup, there are no more tasks
-	 * referencing it, and all the RCU grace periods that may have
-	 * referenced it are ended (as the destruction of the parent
-	 * cgroup is RCU-safe); bgrp->group_data will not be accessed by
-	 * anything else and we don't need any synchronization.
-	 */
-	hlist_for_each_entry_safe(iog, n, tmp, &iocg->group_data, group_node)
-		io_destroy_group(iocg, iog);
+	rcu_read_lock();
 
-	BUG_ON(!hlist_empty(&iocg->group_data));
+	BUG_ON(!id);
+	css = css_lookup(&io_subsys, id);
 
-	kfree(iocg);
+	/* css can't go away as associated io group is still around */
+	BUG_ON(!css);
+
+	iocg = container_of(css, struct io_cgroup, css);
+
+	spin_lock_irqsave(&iocg->lock, flags);
+	hlist_for_each_entry_rcu(__iog, n, &iocg->group_data, group_node) {
+		/*
+		 * Remove iog only if it is still in iocg list. Cgroup
+		 * deletion could have deleted it already.
+		 */
+		if (__iog == iog) {
+			hlist_del_rcu(&iog->group_node);
+			__io_destroy_group(efqd, iog);
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&iocg->lock, flags);
+	rcu_read_unlock();
 }
 
 void io_disconnect_groups(struct elevator_queue *e)
@@ -1678,19 +1817,7 @@ void io_disconnect_groups(struct elevator_queue *e)
 
 	hlist_for_each_entry_safe(iog, pos, n, &efqd->group_list,
 					elv_data_node) {
-		hlist_del(&iog->elv_data_node);
-
-		__bfq_deactivate_entity(iog->my_entity, 0);
-
-		/*
-		 * Don't remove from the group hash, just set an
-		 * invalid key.  No lookups can race with the
-		 * assignment as bfqd is being destroyed; this
-		 * implies also that new elements cannot be added
-		 * to the list.
-		 */
-		rcu_assign_pointer(iog->key, NULL);
-		io_put_io_group_queues(e, iog);
+		io_group_check_and_destroy(efqd, iog);
 	}
 }
 
@@ -1821,6 +1948,7 @@ alloc_ioq:
 		elv_init_ioq(e, ioq, iog, sched_q, IOPRIO_CLASS_BE, 4, 1);
 		io_group_set_ioq(iog, ioq);
 		elv_mark_ioq_sync(ioq);
+		elv_get_iog(iog);
 	}
 
 	if (new_sched_q)
@@ -2339,10 +2467,14 @@ void elv_put_ioq(struct io_queue *ioq)
 	struct elv_fq_data *efqd = ioq->efqd;
 	struct elevator_queue *e = container_of(efqd, struct elevator_queue,
 						efqd);
+	struct io_group *iog;
 
 	BUG_ON(atomic_read(&ioq->ref) <= 0);
 	if (!atomic_dec_and_test(&ioq->ref))
 		return;
+
+	iog = ioq_to_io_group(ioq);
+
 	BUG_ON(ioq->nr_queued);
 	BUG_ON(ioq->entity.tree != NULL);
 	BUG_ON(elv_ioq_busy(ioq));
@@ -2354,16 +2486,15 @@ void elv_put_ioq(struct io_queue *ioq)
 	e->ops->elevator_free_sched_queue_fn(e, ioq->sched_queue);
 	elv_log_ioq(efqd, ioq, "put_queue");
 	elv_free_ioq(ioq);
+	elv_put_iog(iog);
 }
 EXPORT_SYMBOL(elv_put_ioq);
 
 void elv_release_ioq(struct elevator_queue *e, struct io_queue **ioq_ptr)
 {
-	struct io_group *root_group = e->efqd.root_group;
 	struct io_queue *ioq = *ioq_ptr;
 
 	if (ioq != NULL) {
-		io_ioq_move(e, ioq, root_group);
 		/* Drop the reference taken by the io group */
 		elv_put_ioq(ioq);
 		*ioq_ptr = NULL;
@@ -2524,6 +2655,8 @@ void elv_deactivate_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
 	if (ioq == efqd->active_queue)
 		elv_reset_active_ioq(efqd);
 
+	requeue = update_requeue(ioq, requeue);
+
 	bfq_deactivate_entity(&ioq->entity, requeue);
 }
 
@@ -2925,15 +3058,6 @@ void elv_ioq_arm_slice_timer(struct request_queue *q, int wait_for_busy)
 	}
 }
 
-void elv_free_idle_ioq_list(struct elevator_queue *e)
-{
-	struct io_queue *ioq, *n;
-	struct elv_fq_data *efqd = &e->efqd;
-
-	list_for_each_entry_safe(ioq, n, &efqd->idle_list, queue_list)
-		elv_deactivate_ioq(efqd, ioq, 0);
-}
-
 /*
  * Call iosched to let that elevator wants to expire the queue. This gives
  * iosched like AS to say no (if it is in the middle of batch changeover or
@@ -3372,7 +3496,6 @@ int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e)
 
 	INIT_WORK(&efqd->unplug_work, elv_kick_queue);
 
-	INIT_LIST_HEAD(&efqd->idle_list);
 	INIT_HLIST_HEAD(&efqd->group_list);
 
 	efqd->elv_slice[0] = elv_slice_async;
@@ -3403,8 +3526,6 @@ void elv_exit_fq_data(struct elevator_queue *e)
 	elv_shutdown_timer_wq(e);
 
 	spin_lock_irq(q->queue_lock);
-	/* This should drop all the idle tree references of ioq */
-	elv_free_idle_ioq_list(e);
 	/* This should drop all the io group references of async queues */
 	io_disconnect_groups(e);
 	spin_unlock_irq(q->queue_lock);
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 48fb8f1..def533b 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -166,7 +166,6 @@ struct io_queue {
 
 	/* Pointer to generic elevator data structure */
 	struct elv_fq_data *efqd;
-	struct list_head queue_list;
 	pid_t pid;
 
 	/* Number of requests queued on this io queue */
@@ -224,6 +223,7 @@ struct io_group {
 	struct hlist_node elv_data_node;
 	struct hlist_node group_node;
 	struct io_sched_data sched_data;
+	atomic_t ref;
 
 	struct io_entity *my_entity;
 
@@ -244,6 +244,9 @@ struct io_group {
 	/* Single ioq per group, used for noop, deadline, anticipatory */
 	struct io_queue *ioq;
 
+	int deleting;
+	unsigned short iocg_id;
+
 };
 
 /**
@@ -281,9 +284,6 @@ struct elv_fq_data {
 	/* List of io groups hanging on this elevator */
 	struct hlist_head group_list;
 
-	/* List of io queues on idle tree. */
-	struct list_head idle_list;
-
 	struct request_queue *queue;
 	unsigned int busy_queues;
 	/*
@@ -519,6 +519,8 @@ extern int elv_fq_set_request_ioq(struct request_queue *q, struct request *rq,
 					struct bio *bio, gfp_t gfp_mask);
 extern void elv_fq_unset_request_ioq(struct request_queue *q,
 					struct request *rq);
+extern void elv_put_iog(struct io_group *iog);
+
 extern struct io_queue *elv_lookup_ioq_current(struct request_queue *q);
 extern struct io_queue *elv_lookup_ioq_bio(struct request_queue *q,
 						struct bio *bio);
@@ -539,6 +541,21 @@ static inline void io_group_set_ioq(struct io_group *iog, struct io_queue *ioq)
 	iog->ioq = ioq;
 }
 
+static inline void elv_get_iog(struct io_group *iog)
+{
+	atomic_inc(&iog->ref);
+}
+
+static inline int update_requeue(struct io_queue *ioq, int requeue)
+{
+	struct io_group *iog = ioq_to_io_group(ioq);
+
+	if (iog->deleting == 1)
+		return 0;
+
+	return requeue;
+}
+
 #else /* !GROUP_IOSCHED */
 /*
  * No ioq movement is needed in case of flat setup. root io group gets cleaned
@@ -597,6 +614,19 @@ static inline struct io_queue *elv_lookup_ioq_bio(struct request_queue *q,
 	return NULL;
 }
 
+static inline void elv_get_iog(struct io_group *iog)
+{
+}
+
+static inline void elv_put_iog(struct io_group *iog)
+{
+}
+
+static inline int update_requeue(struct io_queue *ioq, int requeue)
+{
+	return requeue;
+}
+
 #endif /* GROUP_IOSCHED */
 
 /* Functions used by blksysfs.c */
-- 
1.6.0.1

[PATCH 17/20] io-controller: Per cgroup request descriptor support

[Vivek Goyal]

o Currently a request queue has got fixed number of request descriptors for
  sync and async requests. Once the request descriptors are consumed, new
  processes are put to sleep and they effectively become serialized. Because
  sync and async queues are separate, async requests don't impact sync ones
  but if one is looking for fairness between async requests, that is not
  achievable if request queue descriptors become bottleneck.

o Make request descriptor's per io group so that if there is lots of IO
  going on in one cgroup, it does not impact the IO of other group.

o This is just one relatively simple way of doing things. This patch will
  probably change after the feedback. Folks have raised concerns that in
  hierchical setup, child's request descriptors should be capped by parent's
  request descriptors. May be we need to have per cgroup per device files
  in cgroups where one can specify the upper limit of request descriptors
  and whenever a cgroup is created one needs to assign request descritor
  limit making sure total sum of child's request descriptor is not more than
  of parent.

  I guess something like memory controller. Anyway, that would be the next
  step. For the time being, we have implemented something simpler as follows.

o This patch implements the per cgroup request descriptors. request pool per
  queue is still common but every group will have its own wait list and its
  own count of request descriptors allocated to that group for sync and async
  queues. So effectively request_list becomes per io group property and not a
  global request queue feature.

o Currently one can define q->nr_requests to limit request descriptors
  allocated for the queue. Now there is another tunable q->nr_group_requests
  which controls the requests descriptr limit per group. q->nr_requests
  supercedes q->nr_group_requests to make sure if there are lots of groups
  present, we don't end up allocating too many request descriptors on the
  queue.

o Issues: Currently notion of congestion is per queue. With per group request
  descriptor it is possible that queue is not congested but the group bio
  will go into is congested.

Signed-off-by: Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/blk-core.c       |  305 +++++++++++++++++++++++++++++++++++++----------
 block/blk-settings.c   |    1 +
 block/blk-sysfs.c      |   57 +++++++--
 block/elevator-fq.c    |   14 +++
 block/elevator-fq.h    |    4 +
 block/elevator.c       |    6 +-
 include/linux/blkdev.h |   87 +++++++++++++-
 7 files changed, 392 insertions(+), 82 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index c77b5b2..35e3725 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -480,20 +480,30 @@ void blk_cleanup_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_cleanup_queue);
 
-static int blk_init_free_list(struct request_queue *q)
+void blk_init_request_list(struct request_list *rl)
 {
-	struct request_list *rl = &q->rq;
 
 	rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
-	rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
-	rl->elvpriv = 0;
 	init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
 	init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
+}
 
-	rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
-				mempool_free_slab, request_cachep, q->node);
+static int blk_init_free_list(struct request_queue *q)
+{
+	/*
+	 * Initialize the queue request list in case there are non-hiearchical
+	 * io schedulers not making use of fair queuing infrastructure.
+	 *
+	 * For ioschedulers making use of fair queuing infrastructure, request
+	 * list is inside the associated group and when that group is
+	 * instanciated, it takes care of initializing the request list also.
+	 */
+	blk_init_request_list(&q->rq);
+	q->rq_data.rq_pool = mempool_create_node(BLKDEV_MIN_RQ,
+				mempool_alloc_slab, mempool_free_slab,
+				request_cachep, q->node);
 
-	if (!rl->rq_pool)
+	if (!q->rq_data.rq_pool)
 		return -ENOMEM;
 
 	return 0;
@@ -590,6 +600,9 @@ blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
 		return NULL;
 	}
 
+	/* init starved waiter wait queue */
+	init_waitqueue_head(&q->rq_data.starved_wait);
+
 	/*
 	 * if caller didn't supply a lock, they get per-queue locking with
 	 * our embedded lock
@@ -639,14 +652,14 @@ static inline void blk_free_request(struct request_queue *q, struct request *rq)
 {
 	if (rq->cmd_flags & REQ_ELVPRIV)
 		elv_put_request(q, rq);
-	mempool_free(rq, q->rq.rq_pool);
+	mempool_free(rq, q->rq_data.rq_pool);
 }
 
 static struct request *
 blk_alloc_request(struct request_queue *q, struct bio *bio, int flags, int priv,
 					gfp_t gfp_mask)
 {
-	struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
+	struct request *rq = mempool_alloc(q->rq_data.rq_pool, gfp_mask);
 
 	if (!rq)
 		return NULL;
@@ -657,7 +670,7 @@ blk_alloc_request(struct request_queue *q, struct bio *bio, int flags, int priv,
 
 	if (priv) {
 		if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) {
-			mempool_free(rq, q->rq.rq_pool);
+			mempool_free(rq, q->rq_data.rq_pool);
 			return NULL;
 		}
 		rq->cmd_flags |= REQ_ELVPRIV;
@@ -700,18 +713,18 @@ static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
 	ioc->last_waited = jiffies;
 }
 
-static void __freed_request(struct request_queue *q, int sync)
+static void __freed_request(struct request_queue *q, int sync,
+					struct request_list *rl)
 {
-	struct request_list *rl = &q->rq;
-
-	if (rl->count[sync] < queue_congestion_off_threshold(q))
+	if (q->rq_data.count[sync] < queue_congestion_off_threshold(q))
 		blk_clear_queue_congested(q, sync);
 
-	if (rl->count[sync] + 1 <= q->nr_requests) {
+	if (q->rq_data.count[sync] + 1 <= q->nr_requests)
+		blk_clear_queue_full(q, sync);
+
+	if (rl->count[sync] + 1 <= q->nr_group_requests) {
 		if (waitqueue_active(&rl->wait[sync]))
 			wake_up(&rl->wait[sync]);
-
-		blk_clear_queue_full(q, sync);
 	}
 }
 
@@ -719,63 +732,133 @@ static void __freed_request(struct request_queue *q, int sync)
  * A request has just been released.  Account for it, update the full and
  * congestion status, wake up any waiters.   Called under q->queue_lock.
  */
-static void freed_request(struct request_queue *q, int sync, int priv)
-{
-	struct request_list *rl = &q->rq;
+static void freed_request(struct request_queue *q, int sync, int priv,
+					struct request_list *rl)
+{
+	/* There is a window during request allocation where request is
+	 * mapped to one group but by the time a queue for the group is
+	 * allocated, it is possible that original cgroup/io group has been
+	 * deleted and now io queue is allocated in a different group (root)
+	 * altogether.
+	 *
+	 * One solution to the problem is that rq should take io group
+	 * reference. But it looks too much to do that to solve this issue.
+	 * The only side affect to the hard to hit issue seems to be that
+	 * we will try to decrement the rl->count for a request list which
+	 * did not allocate that request. Chcek for rl->count going less than
+	 * zero and do not decrement it if that's the case.
+	 */
+
+	if (priv && rl->count[sync] > 0)
+		rl->count[sync]--;
+
+	BUG_ON(!q->rq_data.count[sync]);
+	q->rq_data.count[sync]--;
 
-	rl->count[sync]--;
 	if (priv)
-		rl->elvpriv--;
+		q->rq_data.elvpriv--;
 
-	__freed_request(q, sync);
+	__freed_request(q, sync, rl);
 
 	if (unlikely(rl->starved[sync ^ 1]))
-		__freed_request(q, sync ^ 1);
+		__freed_request(q, sync ^ 1, rl);
+
+	/* Wake up the starved process on global list, if any */
+	if (unlikely(q->rq_data.starved)) {
+		if (waitqueue_active(&q->rq_data.starved_wait))
+			wake_up(&q->rq_data.starved_wait);
+		q->rq_data.starved--;
+	}
+}
+
+/*
+ * Returns whether one can sleep on this request list or not. There are
+ * cases (elevator switch) where request list might not have allocated
+ * any request descriptor but we deny request allocation due to gloabl
+ * limits. In that case one should sleep on global list as on this request
+ * list no wakeup will take place.
+ *
+ * Also sets the request list starved flag if there are no requests pending
+ * in the direction of rq.
+ *
+ * Return 1 --> sleep on request list, 0 --> sleep on global list
+ */
+static int can_sleep_on_request_list(struct request_list *rl, int is_sync)
+{
+	if (unlikely(rl->count[is_sync] == 0)) {
+		/*
+		 * If there is a request pending in other direction
+		 * in same io group, then set the starved flag of
+		 * the group request list. Otherwise, we need to
+		 * make this process sleep in global starved list
+		 * to make sure it will not sleep indefinitely.
+		 */
+		if (rl->count[is_sync ^ 1] != 0) {
+			rl->starved[is_sync] = 1;
+			return 1;
+		} else
+			return 0;
+	}
+
+	return 1;
 }
 
 /*
  * Get a free request, queue_lock must be held.
- * Returns NULL on failure, with queue_lock held.
+ * Returns NULL on failure, with queue_lock held. Also sets the "reason" field
+ * in case of failure. This reason field helps caller decide to whether sleep
+ * on per group list or global per queue list.
+ * reason = 0 sleep on per group list
+ * reason = 1 sleep on global list
+ *
  * Returns !NULL on success, with queue_lock *not held*.
  */
 static struct request *get_request(struct request_queue *q, int rw_flags,
-				   struct bio *bio, gfp_t gfp_mask)
+					struct bio *bio, gfp_t gfp_mask,
+					struct request_list *rl, int *reason)
 {
 	struct request *rq = NULL;
-	struct request_list *rl = &q->rq;
 	struct io_context *ioc = NULL;
 	const bool is_sync = rw_is_sync(rw_flags) != 0;
 	int may_queue, priv;
+	int sleep_on_global = 0;
 
 	may_queue = elv_may_queue(q, rw_flags);
 	if (may_queue == ELV_MQUEUE_NO)
 		goto rq_starved;
 
-	if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
-		if (rl->count[is_sync]+1 >= q->nr_requests) {
-			ioc = current_io_context(GFP_ATOMIC, q->node);
-			/*
-			 * The queue will fill after this allocation, so set
-			 * it as full, and mark this process as "batching".
-			 * This process will be allowed to complete a batch of
-			 * requests, others will be blocked.
-			 */
-			if (!blk_queue_full(q, is_sync)) {
-				ioc_set_batching(q, ioc);
-				blk_set_queue_full(q, is_sync);
-			} else {
-				if (may_queue != ELV_MQUEUE_MUST
-						&& !ioc_batching(q, ioc)) {
-					/*
-					 * The queue is full and the allocating
-					 * process is not a "batcher", and not
-					 * exempted by the IO scheduler
-					 */
-					goto out;
-				}
+	if (q->rq_data.count[is_sync]+1 >= queue_congestion_on_threshold(q))
+		blk_set_queue_congested(q, is_sync);
+
+	/*
+	 * Looks like there is no user of queue full now.
+	 * Keeping it for time being.
+	 */
+	if (q->rq_data.count[is_sync]+1 >= q->nr_requests)
+		blk_set_queue_full(q, is_sync);
+
+	if (rl->count[is_sync]+1 >= q->nr_group_requests) {
+		ioc = current_io_context(GFP_ATOMIC, q->node);
+		/*
+		 * The queue request descriptor group will fill after this
+		 * allocation, so set
+		 * it as full, and mark this process as "batching".
+		 * This process will be allowed to complete a batch of
+		 * requests, others will be blocked.
+		 */
+		if (rl->count[is_sync] <= q->nr_group_requests)
+			ioc_set_batching(q, ioc);
+		else {
+			if (may_queue != ELV_MQUEUE_MUST
+					&& !ioc_batching(q, ioc)) {
+				/*
+				 * The queue is full and the allocating
+				 * process is not a "batcher", and not
+				 * exempted by the IO scheduler
+				 */
+				goto out;
 			}
 		}
-		blk_set_queue_congested(q, is_sync);
 	}
 
 	/*
@@ -783,21 +866,60 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
 	 * limit of requests, otherwise we could have thousands of requests
 	 * allocated with any setting of ->nr_requests
 	 */
-	if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
+
+	if (q->rq_data.count[is_sync] >= (3 * q->nr_requests / 2)) {
+		/*
+		 * Queue is too full for allocation. On which request queue
+		 * the task should sleep? Generally it should sleep on its
+		 * request list but if elevator switch is happening, in that
+		 * window, request descriptors are allocated from global
+		 * pool and are not accounted against any particular request
+		 * list as group is going away.
+		 *
+		 * So it might happen that request list does not have any
+		 * requests allocated at all and if process sleeps on per
+		 * group request list, it will not be woken up. In such case,
+		 * make it sleep on global starved list.
+		 */
+		if (test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags)
+		    || !can_sleep_on_request_list(rl, is_sync))
+			sleep_on_global = 1;
+		goto out;
+	}
+
+	/*
+	 * Allocation of request is allowed from queue perspective. Now check
+	 * from per group request list
+	 */
+
+	if (rl->count[is_sync] >= (3 * q->nr_group_requests / 2))
 		goto out;
 
-	rl->count[is_sync]++;
 	rl->starved[is_sync] = 0;
 
+	q->rq_data.count[is_sync]++;
+
 	priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
-	if (priv)
-		rl->elvpriv++;
+	if (priv) {
+		q->rq_data.elvpriv++;
+		/*
+		 * Account the request to request list only if request is
+		 * going to elevator. During elevator switch, there will
+		 * be small window where group is going away and new group
+		 * will not be allocated till elevator switch is complete.
+		 * So till then instead of slowing down the application,
+		 * we will continue to allocate request from total common
+		 * pool instead of per group limit
+		 */
+		rl->count[is_sync]++;
+	}
 
 	if (blk_queue_io_stat(q))
 		rw_flags |= REQ_IO_STAT;
 	spin_unlock_irq(q->queue_lock);
 
 	rq = blk_alloc_request(q, bio, rw_flags, priv, gfp_mask);
+
 	if (unlikely(!rq)) {
 		/*
 		 * Allocation failed presumably due to memory. Undo anything
@@ -807,7 +929,7 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
 		 * wait queue, but this is pretty rare.
 		 */
 		spin_lock_irq(q->queue_lock);
-		freed_request(q, is_sync, priv);
+		freed_request(q, is_sync, priv, rl);
 
 		/*
 		 * in the very unlikely event that allocation failed and no
@@ -817,9 +939,8 @@ static struct request *get_request(struct request_queue *q, int rw_flags,
 		 * rq mempool into READ and WRITE
 		 */
 rq_starved:
-		if (unlikely(rl->count[is_sync] == 0))
-			rl->starved[is_sync] = 1;
-
+		if (!can_sleep_on_request_list(rl, is_sync))
+			sleep_on_global = 1;
 		goto out;
 	}
 
@@ -834,6 +955,8 @@ rq_starved:
 
 	trace_block_getrq(q, bio, rw_flags & 1);
 out:
+	if (reason && sleep_on_global)
+		*reason = 1;
 	return rq;
 }
 
@@ -847,16 +970,44 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
 					struct bio *bio)
 {
 	const bool is_sync = rw_is_sync(rw_flags) != 0;
+	int sleep_on_global = 0;
 	struct request *rq;
+	struct request_list *rl = blk_get_request_list(q, bio);
+	struct io_group *iog = NULL;
 
-	rq = get_request(q, rw_flags, bio, GFP_NOIO);
+	rq = get_request(q, rw_flags, bio, GFP_NOIO, rl, &sleep_on_global);
 	while (!rq) {
 		DEFINE_WAIT(wait);
 		struct io_context *ioc;
-		struct request_list *rl = &q->rq;
 
-		prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
-				TASK_UNINTERRUPTIBLE);
+		if (sleep_on_global) {
+			/*
+			 * Task failed allocation and needs to wait and
+			 * try again. There are no requests pending from
+			 * the io group hence need to sleep on global
+			 * wait queue. Most likely the allocation failed
+			 * because of memory issues.
+			 */
+
+			q->rq_data.starved++;
+			prepare_to_wait_exclusive(&q->rq_data.starved_wait,
+					&wait, TASK_UNINTERRUPTIBLE);
+		} else {
+			/*
+			 * We are about to sleep on a request list and we
+			 * drop queue lock. After waking up, we will do
+			 * finish_wait() on request list and in the mean
+			 * time group might be gone. Take a reference to
+			 * the group now.
+			 */
+			prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
+					TASK_UNINTERRUPTIBLE);
+#ifdef CONFIG_GROUP_IOSCHED
+			iog = rl_iog(rl);
+			if (iog)
+				elv_get_iog(iog);
+#endif
+		}
 
 		trace_block_sleeprq(q, bio, rw_flags & 1);
 
@@ -874,9 +1025,30 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
 		ioc_set_batching(q, ioc);
 
 		spin_lock_irq(q->queue_lock);
-		finish_wait(&rl->wait[is_sync], &wait);
 
-		rq = get_request(q, rw_flags, bio, GFP_NOIO);
+		if (sleep_on_global) {
+			finish_wait(&q->rq_data.starved_wait, &wait);
+			sleep_on_global = 0;
+		} else {
+			finish_wait(&rl->wait[is_sync], &wait);
+#ifdef CONFIG_GROUP_IOSCHED
+			/*
+			 * We had taken a reference to the rl/iog.
+			 * Put that now
+			 */
+			iog = rl_iog(rl);
+			if (iog)
+				elv_put_iog(iog);
+#endif
+		}
+
+		/*
+		 * After the sleep check the rl again in case cgrop bio
+		 * belonged to is gone and it is mapped to root group now
+		 */
+		rl = blk_get_request_list(q, bio);
+		rq = get_request(q, rw_flags, bio, GFP_NOIO, rl,
+					&sleep_on_global);
 	};
 
 	return rq;
@@ -885,14 +1057,16 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
 {
 	struct request *rq;
+	struct request_list *rl;
 
 	BUG_ON(rw != READ && rw != WRITE);
 
 	spin_lock_irq(q->queue_lock);
+	rl = blk_get_request_list(q, NULL);
 	if (gfp_mask & __GFP_WAIT) {
 		rq = get_request_wait(q, rw, NULL);
 	} else {
-		rq = get_request(q, rw, NULL, gfp_mask);
+		rq = get_request(q, rw, NULL, gfp_mask, rl, NULL);
 		if (!rq)
 			spin_unlock_irq(q->queue_lock);
 	}
@@ -1075,12 +1249,13 @@ void __blk_put_request(struct request_queue *q, struct request *req)
 	if (req->cmd_flags & REQ_ALLOCED) {
 		int is_sync = rq_is_sync(req) != 0;
 		int priv = req->cmd_flags & REQ_ELVPRIV;
+		struct request_list *rl = rq_rl(q, req);
 
 		BUG_ON(!list_empty(&req->queuelist));
 		BUG_ON(!hlist_unhashed(&req->hash));
 
 		blk_free_request(q, req);
-		freed_request(q, is_sync, priv);
+		freed_request(q, is_sync, priv, rl);
 	}
 }
 EXPORT_SYMBOL_GPL(__blk_put_request);
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 57af728..3230d1f 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -123,6 +123,7 @@ void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn)
 	 * set defaults
 	 */
 	q->nr_requests = BLKDEV_MAX_RQ;
+	q->nr_group_requests = BLKDEV_MAX_GROUP_RQ;
 	blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
 	blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS);
 	blk_queue_segment_boundary(q, BLK_SEG_BOUNDARY_MASK);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index c942ddc..b60b76e 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -38,7 +38,7 @@ static ssize_t queue_requests_show(struct request_queue *q, char *page)
 static ssize_t
 queue_requests_store(struct request_queue *q, const char *page, size_t count)
 {
-	struct request_list *rl = &q->rq;
+	struct request_list *rl = blk_get_request_list(q, NULL);
 	unsigned long nr;
 	int ret = queue_var_store(&nr, page, count);
 	if (nr < BLKDEV_MIN_RQ)
@@ -48,32 +48,55 @@ queue_requests_store(struct request_queue *q, const char *page, size_t count)
 	q->nr_requests = nr;
 	blk_queue_congestion_threshold(q);
 
-	if (rl->count[BLK_RW_SYNC] >= queue_congestion_on_threshold(q))
+	if (q->rq_data.count[BLK_RW_SYNC] >= queue_congestion_on_threshold(q))
 		blk_set_queue_congested(q, BLK_RW_SYNC);
-	else if (rl->count[BLK_RW_SYNC] < queue_congestion_off_threshold(q))
+	else if (q->rq_data.count[BLK_RW_SYNC] <
+				queue_congestion_off_threshold(q))
 		blk_clear_queue_congested(q, BLK_RW_SYNC);
 
-	if (rl->count[BLK_RW_ASYNC] >= queue_congestion_on_threshold(q))
+	if (q->rq_data.count[BLK_RW_ASYNC] >= queue_congestion_on_threshold(q))
 		blk_set_queue_congested(q, BLK_RW_ASYNC);
-	else if (rl->count[BLK_RW_ASYNC] < queue_congestion_off_threshold(q))
+	else if (q->rq_data.count[BLK_RW_ASYNC] <
+				queue_congestion_off_threshold(q))
 		blk_clear_queue_congested(q, BLK_RW_ASYNC);
 
-	if (rl->count[BLK_RW_SYNC] >= q->nr_requests) {
+	if (q->rq_data.count[BLK_RW_SYNC] >= q->nr_requests) {
 		blk_set_queue_full(q, BLK_RW_SYNC);
-	} else if (rl->count[BLK_RW_SYNC]+1 <= q->nr_requests) {
+	} else if (q->rq_data.count[BLK_RW_SYNC]+1 <= q->nr_requests) {
 		blk_clear_queue_full(q, BLK_RW_SYNC);
 		wake_up(&rl->wait[BLK_RW_SYNC]);
 	}
 
-	if (rl->count[BLK_RW_ASYNC] >= q->nr_requests) {
+	if (q->rq_data.count[BLK_RW_ASYNC] >= q->nr_requests) {
 		blk_set_queue_full(q, BLK_RW_ASYNC);
-	} else if (rl->count[BLK_RW_ASYNC]+1 <= q->nr_requests) {
+	} else if (q->rq_data.count[BLK_RW_ASYNC]+1 <= q->nr_requests) {
 		blk_clear_queue_full(q, BLK_RW_ASYNC);
 		wake_up(&rl->wait[BLK_RW_ASYNC]);
 	}
 	spin_unlock_irq(q->queue_lock);
 	return ret;
 }
+#ifdef CONFIG_GROUP_IOSCHED
+static ssize_t queue_group_requests_show(struct request_queue *q, char *page)
+{
+	return queue_var_show(q->nr_group_requests, (page));
+}
+
+static ssize_t
+queue_group_requests_store(struct request_queue *q, const char *page,
+					size_t count)
+{
+	unsigned long nr;
+	int ret = queue_var_store(&nr, page, count);
+	if (nr < BLKDEV_MIN_RQ)
+		nr = BLKDEV_MIN_RQ;
+
+	spin_lock_irq(q->queue_lock);
+	q->nr_group_requests = nr;
+	spin_unlock_irq(q->queue_lock);
+	return ret;
+}
+#endif
 
 static ssize_t queue_ra_show(struct request_queue *q, char *page)
 {
@@ -224,6 +247,14 @@ static struct queue_sysfs_entry queue_requests_entry = {
 	.store = queue_requests_store,
 };
 
+#ifdef CONFIG_GROUP_IOSCHED
+static struct queue_sysfs_entry queue_group_requests_entry = {
+	.attr = {.name = "nr_group_requests", .mode = S_IRUGO | S_IWUSR },
+	.show = queue_group_requests_show,
+	.store = queue_group_requests_store,
+};
+#endif
+
 static struct queue_sysfs_entry queue_ra_entry = {
 	.attr = {.name = "read_ahead_kb", .mode = S_IRUGO | S_IWUSR },
 	.show = queue_ra_show,
@@ -304,6 +335,9 @@ static struct queue_sysfs_entry queue_fairness_entry = {
 
 static struct attribute *default_attrs[] = {
 	&queue_requests_entry.attr,
+#ifdef CONFIG_GROUP_IOSCHED
+	&queue_group_requests_entry.attr,
+#endif
 	&queue_ra_entry.attr,
 	&queue_max_hw_sectors_entry.attr,
 	&queue_max_sectors_entry.attr,
@@ -385,12 +419,11 @@ static void blk_release_queue(struct kobject *kobj)
 {
 	struct request_queue *q =
 		container_of(kobj, struct request_queue, kobj);
-	struct request_list *rl = &q->rq;
 
 	blk_sync_queue(q);
 
-	if (rl->rq_pool)
-		mempool_destroy(rl->rq_pool);
+	if (q->rq_data.rq_pool)
+		mempool_destroy(q->rq_data.rq_pool);
 
 	if (q->queue_tags)
 		__blk_queue_free_tags(q);
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 9d36227..0650e03 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -996,6 +996,16 @@ struct io_cgroup *cgroup_to_io_cgroup(struct cgroup *cgroup)
 			    struct io_cgroup, css);
 }
 
+struct request_list *io_group_get_request_list(struct request_queue *q,
+						struct bio *bio)
+{
+	struct io_group *iog;
+
+	iog = io_get_io_group(q, bio, 1);
+	BUG_ON(!iog);
+	return &iog->rl;
+}
+
 /*
  * Search the bfq_group for bfqd into the hash table (by now only a list)
  * of bgrp.  Must be called under rcu_read_lock().
@@ -1224,6 +1234,8 @@ struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
 
 		iog->iocg_id = css_id(&iocg->css);
 
+		blk_init_request_list(&iog->rl);
+
 		if (leaf == NULL) {
 			leaf = iog;
 			prev = leaf;
@@ -1483,6 +1495,8 @@ struct io_group *io_alloc_root_group(struct request_queue *q,
 	for (i = 0; i < IO_IOPRIO_CLASSES; i++)
 		iog->sched_data.service_tree[i] = IO_SERVICE_TREE_INIT;
 
+	blk_init_request_list(&iog->rl);
+
 	iocg = &io_root_cgroup;
 	spin_lock_irq(&iocg->lock);
 	rcu_assign_pointer(iog->key, key);
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index def533b..5783f33 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -247,6 +247,8 @@ struct io_group {
 	int deleting;
 	unsigned short iocg_id;
 
+	/* request list associated with the group */
+	struct request_list rl;
 };
 
 /**
@@ -524,6 +526,8 @@ extern void elv_put_iog(struct io_group *iog);
 extern struct io_queue *elv_lookup_ioq_current(struct request_queue *q);
 extern struct io_queue *elv_lookup_ioq_bio(struct request_queue *q,
 						struct bio *bio);
+extern struct request_list *io_group_get_request_list(struct request_queue *q,
+						struct bio *bio);
 
 /* Returns single ioq associated with the io group. */
 static inline struct io_queue *io_group_ioq(struct io_group *iog)
diff --git a/block/elevator.c b/block/elevator.c
index c693ac8..7c6826a 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -668,7 +668,7 @@ void elv_quiesce_start(struct request_queue *q)
 	 * make sure we don't have any requests in flight
 	 */
 	elv_drain_elevator(q);
-	while (q->rq.elvpriv) {
+	while (q->rq_data.elvpriv) {
 		blk_start_queueing(q);
 		spin_unlock_irq(q->queue_lock);
 		msleep(10);
@@ -768,8 +768,8 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
 	}
 
 	if (unplug_it && blk_queue_plugged(q)) {
-		int nrq = q->rq.count[BLK_RW_SYNC] + q->rq.count[BLK_RW_ASYNC]
-			- q->in_flight;
+		int nrq = q->rq_data.count[BLK_RW_SYNC] +
+				q->rq_data.count[BLK_RW_ASYNC] - q->in_flight;
 
 		if (nrq >= q->unplug_thresh)
 			__generic_unplug_device(q);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 539cb9d..23b1d6c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -32,21 +32,51 @@ struct request;
 struct sg_io_hdr;
 
 #define BLKDEV_MIN_RQ	4
+
+#ifdef CONFIG_GROUP_IOSCHED
+#define BLKDEV_MAX_RQ	256	/* Default maximum */
+#define BLKDEV_MAX_GROUP_RQ    64      /* Default maximum */
+#else
 #define BLKDEV_MAX_RQ	128	/* Default maximum */
+/*
+ * This is eqivalent to case of only one group present (root group). Let
+ * it consume all the request descriptors available on the queue .
+ */
+#define BLKDEV_MAX_GROUP_RQ    BLKDEV_MAX_RQ      /* Default maximum */
+#endif
 
 struct request;
 typedef void (rq_end_io_fn)(struct request *, int);
 
 struct request_list {
 	/*
-	 * count[], starved[], and wait[] are indexed by
+	 * count[], starved and wait[] are indexed by
 	 * BLK_RW_SYNC/BLK_RW_ASYNC
 	 */
 	int count[2];
 	int starved[2];
+	wait_queue_head_t wait[2];
+};
+
+/*
+ * This data structures keeps track of mempool of requests for the queue
+ * and some overall statistics.
+ */
+struct request_data {
+	/*
+	 * Per queue request descriptor count. This is in addition to per
+	 * cgroup count
+	 */
+	int count[2];
 	int elvpriv;
 	mempool_t *rq_pool;
-	wait_queue_head_t wait[2];
+	int starved;
+	/*
+	 * Global list for starved tasks. A task will be queued here if
+	 * it could not allocate request descriptor and the associated
+	 * group request list does not have any requests pending.
+	 */
+	wait_queue_head_t starved_wait;
 };
 
 /*
@@ -337,6 +367,9 @@ struct request_queue
 	 */
 	struct request_list	rq;
 
+	/* Contains request pool and other data like starved data */
+	struct request_data	rq_data;
+
 	request_fn_proc		*request_fn;
 	make_request_fn		*make_request_fn;
 	prep_rq_fn		*prep_rq_fn;
@@ -399,6 +432,8 @@ struct request_queue
 	 * queue settings
 	 */
 	unsigned long		nr_requests;	/* Max # of requests */
+	/* Max # of per io group requests */
+	unsigned long		nr_group_requests;
 	unsigned int		nr_congestion_on;
 	unsigned int		nr_congestion_off;
 	unsigned int		nr_batching;
@@ -772,6 +807,54 @@ extern int scsi_cmd_ioctl(struct request_queue *, struct gendisk *, fmode_t,
 extern int sg_scsi_ioctl(struct request_queue *, struct gendisk *, fmode_t,
 			 struct scsi_ioctl_command __user *);
 
+extern void blk_init_request_list(struct request_list *rl);
+
+static inline struct request_list *blk_get_request_list(struct request_queue *q,
+						struct bio *bio)
+{
+#ifdef CONFIG_GROUP_IOSCHED
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return &q->rq;
+
+	return io_group_get_request_list(q, bio);
+#else
+	return &q->rq;
+#endif
+}
+
+static inline struct request_list *rq_rl(struct request_queue *q,
+						struct request *rq)
+{
+#ifdef CONFIG_GROUP_IOSCHED
+	struct io_group *iog;
+	int priv = rq->cmd_flags & REQ_ELVPRIV;
+
+	if (!elv_iosched_fair_queuing_enabled(q->elevator))
+		return &q->rq;
+
+	BUG_ON(priv && !rq->ioq);
+
+	if (priv)
+		iog = ioq_to_io_group(rq->ioq);
+	else
+		iog = q->elevator->efqd.root_group;
+
+	BUG_ON(!iog);
+	return &iog->rl;
+#else
+	return &q->rq;
+#endif
+}
+
+static inline struct io_group *rl_iog(struct request_list *rl)
+{
+#ifdef CONFIG_GROUP_IOSCHED
+	return container_of(rl, struct io_group, rl);
+#else
+	return NULL;
+#endif
+}
+
 /*
  * Temporary export, until SCSI gets fixed up.
  */
-- 
1.6.0.1

[PATCH 18/20] io-controller: Support per cgroup per device weights and io class

[Vivek Goyal]

This patch enables per-cgroup per-device weight and ioprio_class handling.
A new cgroup interface "policy" is introduced. You can make use of this
file to configure weight and ioprio_class for each device in a given cgroup.
The original "weight" and "ioprio_class" files are still available. If you
don't do special configuration for a particular device, "weight" and
"ioprio_class" are used as default values in this device.

You can use the following format to play with the new interface.
#echo DEV:weight:ioprio_class > /patch/to/cgroup/policy
weight=0 means removing the policy for DEV.

Examples:
Configure weight=300 ioprio_class=2 on /dev/hdb in this cgroup
# echo /dev/hdb:300:2 > io.policy
# cat io.policy
dev weight class
/dev/hdb 300 2

Configure weight=500 ioprio_class=1 on /dev/hda in this cgroup
# echo /dev/hda:500:1 > io.policy
# cat io.policy
dev weight class
/dev/hda 500 1
/dev/hdb 300 2

Remove the policy for /dev/hda in this cgroup
# echo /dev/hda:0:1 > io.policy
# cat io.policy
dev weight class
/dev/hdb 300 2

Changelog (v1 -> v2)
- Rename some structures
- Use spin_lock_irqsave() and spin_lock_irqrestore() version to prevent
  from enabling the interrupts unconditionally.
- Fix policy setup bug when switching to another io scheduler.
- If a policy is available for a specific device, don't update weight and
  io class when writing "weight" and "iprio_class".
- Fix a bug when parsing policy string.

Signed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/elevator-fq.c |  245 +++++++++++++++++++++++++++++++++++++++++++++++++-
 block/elevator-fq.h |   11 +++
 2 files changed, 251 insertions(+), 5 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 0650e03..6d97ad9 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -13,6 +13,7 @@
 #include <linux/blktrace_api.h>
 #include <linux/seq_file.h>
 #include <linux/biotrack.h>
+#include <linux/genhd.h>
 
 /* Values taken from cfq */
 const int elv_slice_sync = HZ / 10;
@@ -1025,12 +1026,31 @@ struct io_group *io_cgroup_lookup_group(struct io_cgroup *iocg, void *key)
 	return NULL;
 }
 
-void io_group_init_entity(struct io_cgroup *iocg, struct io_group *iog)
+static struct io_policy_node *policy_search_node(const struct io_cgroup *iocg,
+						 dev_t dev);
+
+void io_group_init_entity(struct io_cgroup *iocg, struct io_group *iog,
+			  dev_t dev)
 {
 	struct io_entity *entity = &iog->entity;
+	struct io_policy_node *pn;
+	unsigned long flags;
+
+	spin_lock_irqsave(&iocg->lock, flags);
+	pn = policy_search_node(iocg, dev);
+	if (pn) {
+		entity->weight = pn->weight;
+		entity->new_weight = pn->weight;
+		entity->ioprio_class = pn->ioprio_class;
+		entity->new_ioprio_class = pn->ioprio_class;
+	} else {
+		entity->weight = iocg->weight;
+		entity->new_weight = iocg->weight;
+		entity->ioprio_class = iocg->ioprio_class;
+		entity->new_ioprio_class = iocg->ioprio_class;
+	}
+	spin_unlock_irqrestore(&iocg->lock, flags);
 
-	entity->weight = entity->new_weight = iocg->weight;
-	entity->ioprio_class = entity->new_ioprio_class = iocg->ioprio_class;
 	entity->ioprio_changed = 1;
 	entity->my_sched_data = &iog->sched_data;
 }
@@ -1094,6 +1114,7 @@ static int io_cgroup_##__VAR##_write(struct cgroup *cgroup,		\
 	struct io_cgroup *iocg;					\
 	struct io_group *iog;						\
 	struct hlist_node *n;						\
+	struct io_policy_node *pn;					\
 									\
 	if (val < (__MIN) || val > (__MAX))				\
 		return -EINVAL;						\
@@ -1106,6 +1127,9 @@ static int io_cgroup_##__VAR##_write(struct cgroup *cgroup,		\
 	spin_lock_irq(&iocg->lock);					\
 	iocg->__VAR = (unsigned long)val;				\
 	hlist_for_each_entry(iog, n, &iocg->group_data, group_node) {	\
+		pn = policy_search_node(iocg, iog->dev);		\
+		if (pn)							\
+			continue;					\
 		iog->entity.new_##__VAR = (unsigned long)val;		\
 		smp_wmb();						\
 		iog->entity.ioprio_changed = 1;				\
@@ -1214,8 +1238,6 @@ struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
 		if (!iog)
 			goto cleanup;
 
-		io_group_init_entity(iocg, iog);
-		iog->my_entity = &iog->entity;
 		atomic_set(&iog->ref, 0);
 		iog->deleting = 0;
 
@@ -1233,6 +1255,8 @@ struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,
 		}
 
 		iog->iocg_id = css_id(&iocg->css);
+		io_group_init_entity(iocg, iog, iog->dev);
+		iog->my_entity = &iog->entity;
 
 		blk_init_request_list(&iog->rl);
 
@@ -1507,8 +1531,212 @@ struct io_group *io_alloc_root_group(struct request_queue *q,
 	return iog;
 }
 
+static int io_cgroup_policy_read(struct cgroup *cgrp, struct cftype *cft,
+				  struct seq_file *m)
+{
+	struct io_cgroup *iocg;
+	struct io_policy_node *pn;
+
+	iocg = cgroup_to_io_cgroup(cgrp);
+
+	if (list_empty(&iocg->policy_list))
+		goto out;
+
+	seq_printf(m, "dev weight class\n");
+
+	spin_lock_irq(&iocg->lock);
+	list_for_each_entry(pn, &iocg->policy_list, node) {
+		seq_printf(m, "%s %lu %lu\n", pn->dev_name,
+			   pn->weight, pn->ioprio_class);
+	}
+	spin_unlock_irq(&iocg->lock);
+out:
+	return 0;
+}
+
+static inline void policy_insert_node(struct io_cgroup *iocg,
+					  struct io_policy_node *pn)
+{
+	list_add(&pn->node, &iocg->policy_list);
+}
+
+/* Must be called with iocg->lock held */
+static inline void policy_delete_node(struct io_policy_node *pn)
+{
+	list_del(&pn->node);
+}
+
+/* Must be called with iocg->lock held */
+static struct io_policy_node *policy_search_node(const struct io_cgroup *iocg,
+						 dev_t dev)
+{
+	struct io_policy_node *pn;
+
+	if (list_empty(&iocg->policy_list))
+		return NULL;
+
+	list_for_each_entry(pn, &iocg->policy_list, node) {
+		if (pn->dev == dev)
+			return pn;
+	}
+
+	return NULL;
+}
+
+static int devname_to_devnum(const char *buf, dev_t *dev)
+{
+	struct block_device *bdev;
+	struct gendisk *disk;
+	int part;
+
+	bdev = lookup_bdev(buf);
+	if (IS_ERR(bdev))
+		return -ENODEV;
+
+	disk = get_gendisk(bdev->bd_dev, &part);
+	if (part)
+		return -EINVAL;
+
+	*dev = MKDEV(disk->major, disk->first_minor);
+	bdput(bdev);
+
+	return 0;
+}
+
+static int policy_parse_and_set(char *buf, struct io_policy_node *newpn)
+{
+	char *s[3], *p;
+	int ret;
+	int i = 0;
+
+	memset(s, 0, sizeof(s));
+	while ((p = strsep(&buf, ":")) != NULL) {
+		if (!*p)
+			continue;
+		s[i++] = p;
+	}
+
+	ret = devname_to_devnum(s[0], &newpn->dev);
+	if (ret)
+		return ret;
+
+	strcpy(newpn->dev_name, s[0]);
+
+	if (s[1] == NULL)
+		return -EINVAL;
+
+	ret = strict_strtoul(s[1], 10, &newpn->weight);
+	if (ret || newpn->weight > WEIGHT_MAX)
+		return -EINVAL;
+
+	if (s[2] == NULL)
+		return -EINVAL;
+
+	ret = strict_strtoul(s[2], 10, &newpn->ioprio_class);
+	if (ret || newpn->ioprio_class < IOPRIO_CLASS_RT ||
+	    newpn->ioprio_class > IOPRIO_CLASS_IDLE)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int io_cgroup_policy_write(struct cgroup *cgrp, struct cftype *cft,
+			    const char *buffer)
+{
+	struct io_cgroup *iocg;
+	struct io_policy_node *newpn, *pn;
+	char *buf;
+	int ret = 0;
+	int keep_newpn = 0;
+	struct hlist_node *n;
+	struct io_group *iog;
+
+	buf = kstrdup(buffer, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	newpn = kzalloc(sizeof(*newpn), GFP_KERNEL);
+	if (!newpn) {
+		ret = -ENOMEM;
+		goto free_buf;
+	}
+
+	ret = policy_parse_and_set(buf, newpn);
+	if (ret)
+		goto free_newpn;
+
+	if (!cgroup_lock_live_group(cgrp)) {
+		ret = -ENODEV;
+		goto free_newpn;
+	}
+
+	iocg = cgroup_to_io_cgroup(cgrp);
+	spin_lock_irq(&iocg->lock);
+
+	pn = policy_search_node(iocg, newpn->dev);
+	if (!pn) {
+		if (newpn->weight != 0) {
+			policy_insert_node(iocg, newpn);
+			keep_newpn = 1;
+		}
+		goto update_io_group;
+	}
+
+	if (newpn->weight == 0) {
+		/* weight == 0 means deleteing a policy */
+		policy_delete_node(pn);
+		goto update_io_group;
+	}
+
+	pn->weight = newpn->weight;
+	pn->ioprio_class = newpn->ioprio_class;
+
+update_io_group:
+	hlist_for_each_entry(iog, n, &iocg->group_data, group_node) {
+		if (iog->dev == newpn->dev) {
+			if (newpn->weight) {
+				iog->entity.new_weight = newpn->weight;
+				iog->entity.new_ioprio_class =
+					newpn->ioprio_class;
+				/*
+				 * iog weight and ioprio_class updating
+				 * actually happens if ioprio_changed is set.
+				 * So ensure ioprio_changed is not set until
+				 * new weight and new ioprio_class are updated.
+				 */
+				smp_wmb();
+				iog->entity.ioprio_changed = 1;
+			} else {
+				iog->entity.new_weight = iocg->weight;
+				iog->entity.new_ioprio_class =
+					iocg->ioprio_class;
+
+				/* The same as above */
+				smp_wmb();
+				iog->entity.ioprio_changed = 1;
+			}
+		}
+	}
+	spin_unlock_irq(&iocg->lock);
+
+	cgroup_unlock();
+
+free_newpn:
+	if (!keep_newpn)
+		kfree(newpn);
+free_buf:
+	kfree(buf);
+	return ret;
+}
+
 struct cftype bfqio_files[] = {
 	{
+		.name = "policy",
+		.read_seq_string = io_cgroup_policy_read,
+		.write_string = io_cgroup_policy_write,
+		.max_write_len = 256,
+	},
+	{
 		.name = "weight",
 		.read_u64 = io_cgroup_weight_read,
 		.write_u64 = io_cgroup_weight_write,
@@ -1550,6 +1778,7 @@ struct cgroup_subsys_state *iocg_create(struct cgroup_subsys *subsys,
 	INIT_HLIST_HEAD(&iocg->group_data);
 	iocg->weight = IO_DEFAULT_GRP_WEIGHT;
 	iocg->ioprio_class = IO_DEFAULT_GRP_CLASS;
+	INIT_LIST_HEAD(&iocg->policy_list);
 
 	return &iocg->css;
 }
@@ -1739,6 +1968,7 @@ void iocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
 	struct io_group *iog;
 	struct elv_fq_data *efqd;
 	unsigned long uninitialized_var(flags);
+	struct io_policy_node *pn, *pntmp;
 
 	/*
 	 * io groups are linked in two lists. One list is maintained
@@ -1777,6 +2007,11 @@ remove_entry:
 	goto remove_entry;
 
 done:
+	list_for_each_entry_safe(pn, pntmp, &iocg->policy_list, node) {
+		policy_delete_node(pn);
+		kfree(pn);
+	}
+
 	free_css_id(&io_subsys, &iocg->css);
 	rcu_read_unlock();
 	BUG_ON(!hlist_empty(&iocg->group_data));
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 5783f33..9062bfd 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -251,6 +251,14 @@ struct io_group {
 	struct request_list rl;
 };
 
+struct io_policy_node {
+	struct list_head node;
+	char dev_name[32];
+	dev_t dev;
+	unsigned long weight;
+	unsigned long ioprio_class;
+};
+
 /**
  * struct bfqio_cgroup - bfq cgroup data structure.
  * @css: subsystem state for bfq in the containing cgroup.
@@ -267,6 +275,9 @@ struct io_cgroup {
 
 	unsigned long weight, ioprio_class;
 
+	/* list of io_policy_node */
+	struct list_head policy_list;
+
 	spinlock_t lock;
 	struct hlist_head group_data;
 };
-- 
1.6.0.1

[PATCH 19/20] io-controller: Debug hierarchical IO scheduling

[Vivek Goyal]

o Littile debugging aid for hierarchical IO scheduling.

o Enabled under CONFIG_DEBUG_GROUP_IOSCHED

o Currently it outputs more debug messages in blktrace output which helps
  a great deal in debugging in hierarchical setup. It also creates additional
  cgroup interfaces io.disk_queue and io.disk_dequeue to output some more
  debugging data.

Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/Kconfig.iosched |   10 ++-
 block/elevator-fq.c   |  298 ++++++++++++++++++++++++++++++++++++++++++++++++-
 block/elevator-fq.h   |   14 +++
 3 files changed, 318 insertions(+), 4 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 0677099..79f188c 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -140,6 +140,14 @@ config TRACK_ASYNC_CONTEXT
 	  request, original owner of the bio is decided by using io tracking
 	  patches otherwise we continue to attribute the request to the
 	  submitting thread.
-endmenu
 
+config DEBUG_GROUP_IOSCHED
+	bool "Debug Hierarchical Scheduling support"
+	depends on CGROUPS && GROUP_IOSCHED
+	default n
+	---help---
+	  Enable some debugging hooks for hierarchical scheduling support.
+	  Currently it just outputs more information in blktrace output.
+
+endmenu
 endif
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 6d97ad9..6dd8683 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -115,6 +115,126 @@ static inline int iog_deleting(struct io_group *iog)
 	return iog->deleting;
 }
 
+static inline struct io_group *io_entity_to_iog(struct io_entity *entity)
+{
+	struct io_group *iog = NULL;
+
+	BUG_ON(entity == NULL);
+	if (entity->my_sched_data != NULL)
+		iog = container_of(entity, struct io_group, entity);
+	return iog;
+}
+
+/* Returns parent group of io group */
+static inline struct io_group *iog_parent(struct io_group *iog)
+{
+	struct io_group *piog;
+
+	if (!iog->entity.sched_data)
+		return NULL;
+
+	/*
+	 * Not following entity->parent pointer as for top level groups
+	 * this pointer is NULL.
+	 */
+	piog = container_of(iog->entity.sched_data, struct io_group,
+					sched_data);
+	return piog;
+}
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+static void io_group_path(struct io_group *iog, char *buf, int buflen)
+{
+	unsigned short id = iog->iocg_id;
+	struct cgroup_subsys_state *css;
+
+	rcu_read_lock();
+
+	if (!id)
+		goto out;
+
+	css = css_lookup(&io_subsys, id);
+	if (!css)
+		goto out;
+
+	if (!css_tryget(css))
+		goto out;
+
+	cgroup_path(css->cgroup, buf, buflen);
+
+	css_put(css);
+
+	rcu_read_unlock();
+	return;
+out:
+	rcu_read_unlock();
+	buf[0] = '\0';
+	return;
+}
+
+/*
+ * An entity has been freshly added to active tree. Either it came from
+ * idle tree or it was not on any of the trees. Do the accounting.
+ */
+static inline void bfq_account_for_entity_addition(struct io_entity *entity)
+{
+	struct io_group *iog = io_entity_to_iog(entity);
+
+	if (iog) {
+		struct elv_fq_data *efqd;
+		char path[128];
+
+		/*
+		 * Keep track of how many times a group has been removed
+		 * from active tree because it did not have any active
+		 * backlogged ioq under it
+		 */
+		iog->queue++;
+		iog->queue_start = jiffies;
+
+		/* Log group addition event */
+		rcu_read_lock();
+		efqd = rcu_dereference(iog->key);
+		if (efqd) {
+			io_group_path(iog, path, sizeof(path));
+			elv_log(efqd, "add group=%s weight=%ld", path,
+					iog->entity.weight);
+		}
+		rcu_read_unlock();
+	}
+}
+
+/*
+ * An entity got removed from active tree and either went to idle tree or
+ * not is on any of the tree. Do the accouting
+ */
+static inline void bfq_account_for_entity_deletion(struct io_entity *entity)
+{
+	struct io_group *iog = io_entity_to_iog(entity);
+
+	if (iog) {
+		struct elv_fq_data *efqd;
+		char path[128];
+
+		iog->dequeue++;
+		/* Keep a track of how long group was on active tree */
+		iog->queue_duration += jiffies_to_msecs(jiffies -
+						iog->queue_start);
+		iog->queue_start = 0;
+
+		/* Log group deletion event */
+		rcu_read_lock();
+		efqd = rcu_dereference(iog->key);
+		if (efqd) {
+			io_group_path(iog, path, sizeof(path));
+			elv_log(efqd, "del group=%s weight=%ld", path,
+					iog->entity.weight);
+		}
+		rcu_read_unlock();
+	}
+}
+#endif
+
 #else /* GROUP_IOSCHED */
 #define for_each_entity(entity)	\
 	for (; entity != NULL; entity = NULL)
@@ -137,6 +257,12 @@ static inline int iog_deleting(struct io_group *iog)
 	/* In flat mode, root cgroup can't be deleted. */
 	return 0;
 }
+
+static inline struct io_group *io_entity_to_iog(struct io_entity *entity)
+{
+	return NULL;
+}
+
 #endif
 
 /*
@@ -570,6 +696,7 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
 {
 	struct io_sched_data *sd = entity->sched_data;
 	struct io_service_tree *st = io_entity_service_tree(entity);
+	int newly_added = 0;
 
 	if (entity == sd->active_entity) {
 		BUG_ON(entity->tree != NULL);
@@ -596,6 +723,7 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
 		bfq_idle_extract(st, entity);
 		entity->start = bfq_gt(st->vtime, entity->finish) ?
 				       st->vtime : entity->finish;
+		newly_added = 1;
 	} else {
 		/*
 		 * The finish time of the entity may be invalid, and
@@ -608,6 +736,7 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
 
 		BUG_ON(entity->on_st);
 		entity->on_st = 1;
+		newly_added = 1;
 	}
 
 	st = __bfq_entity_update_prio(st, entity);
@@ -645,6 +774,10 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
 		bfq_calc_finish(entity, entity->budget);
 	}
 	bfq_active_insert(st, entity);
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+	if (newly_added)
+		bfq_account_for_entity_addition(entity);
+#endif
 }
 
 /**
@@ -715,6 +848,9 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
 	BUG_ON(sd->active_entity == entity);
 	BUG_ON(sd->next_active == entity);
 
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+	bfq_account_for_entity_deletion(entity);
+#endif
 	return ret;
 }
 
@@ -1205,6 +1341,67 @@ static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,
 	return 0;
 }
 
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+static int io_cgroup_disk_queue_read(struct cgroup *cgroup,
+			struct cftype *cftype, struct seq_file *m)
+{
+	struct io_cgroup *iocg = NULL;
+	struct io_group *iog = NULL;
+	struct hlist_node *n;
+
+	if (!cgroup_lock_live_group(cgroup))
+		return -ENODEV;
+
+	iocg = cgroup_to_io_cgroup(cgroup);
+	spin_lock_irq(&iocg->lock);
+	/* Loop through all the io groups and print statistics */
+	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
+		/*
+		 * There might be groups which are not functional and
+		 * waiting to be reclaimed upon cgoup deletion.
+		 */
+		if (iog->key) {
+			seq_printf(m, "%u %u %lu %lu\n", MAJOR(iog->dev),
+					MINOR(iog->dev), iog->queue,
+					iog->queue_duration);
+		}
+	}
+	spin_unlock_irq(&iocg->lock);
+	cgroup_unlock();
+
+	return 0;
+}
+
+static int io_cgroup_disk_dequeue_read(struct cgroup *cgroup,
+			struct cftype *cftype, struct seq_file *m)
+{
+	struct io_cgroup *iocg = NULL;
+	struct io_group *iog = NULL;
+	struct hlist_node *n;
+
+	if (!cgroup_lock_live_group(cgroup))
+		return -ENODEV;
+
+	iocg = cgroup_to_io_cgroup(cgroup);
+	spin_lock_irq(&iocg->lock);
+	/* Loop through all the io groups and print statistics */
+	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
+		/*
+		 * There might be groups which are not functional and
+		 * waiting to be reclaimed upon cgoup deletion.
+		 */
+		if (iog->key) {
+			seq_printf(m, "%u %u %lu\n", MAJOR(iog->dev),
+					MINOR(iog->dev), iog->dequeue);
+		}
+	}
+	spin_unlock_irq(&iocg->lock);
+	cgroup_unlock();
+
+	return 0;
+}
+#endif
+
 /**
  * bfq_group_chain_alloc - allocate a chain of groups.
  * @bfqd: queue descriptor.
@@ -1754,6 +1951,16 @@ struct cftype bfqio_files[] = {
 		.name = "disk_sectors",
 		.read_seq_string = io_cgroup_disk_sectors_read,
 	},
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+	{
+		.name = "disk_queue",
+		.read_seq_string = io_cgroup_disk_queue_read,
+	},
+	{
+		.name = "disk_dequeue",
+		.read_seq_string = io_cgroup_disk_dequeue_read,
+	},
+#endif
 };
 
 int iocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
@@ -2078,6 +2285,7 @@ struct cgroup_subsys io_subsys = {
 	.destroy = iocg_destroy,
 	.populate = iocg_populate,
 	.subsys_id = io_subsys_id,
+	.use_id = 1,
 };
 
 /*
@@ -2361,6 +2569,25 @@ EXPORT_SYMBOL(elv_get_slice_idle);
 void elv_ioq_served(struct io_queue *ioq, bfq_service_t served)
 {
 	entity_served(&ioq->entity, served, ioq->nr_sectors);
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+		{
+			struct elv_fq_data *efqd = ioq->efqd;
+			char path[128];
+			struct io_group *iog = ioq_to_io_group(ioq);
+			io_group_path(iog, path, sizeof(path));
+			elv_log_ioq(efqd, ioq, "ioq served: QSt=0x%lx QSs=0x%lx"
+				" QTt=0x%lx QTs=0x%lx grp=%s GTt=0x%lx "
+				" GTs=0x%lx rq_queued=%d",
+				served, ioq->nr_sectors,
+				ioq->entity.total_service,
+				ioq->entity.total_sector_service,
+				path,
+				iog->entity.total_service,
+				iog->entity.total_sector_service,
+				ioq->nr_queued);
+		}
+#endif
 }
 
 /* Tells whether ioq is queued in root group or not */
@@ -2835,10 +3062,32 @@ static void __elv_set_active_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,
 	if (ioq) {
 		struct io_group *iog = ioq_to_io_group(ioq);
 		elv_log_ioq(efqd, ioq, "set_active, busy=%d ioprio=%d"
-				" weight=%ld group_weight=%ld",
+				" weight=%ld rq_queued=%d group_weight=%ld",
 				efqd->busy_queues,
 				ioq->entity.ioprio, ioq->entity.weight,
-				iog_weight(iog));
+				ioq->nr_queued, iog_weight(iog));
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+			{
+				char path[128];
+				int nr_active = 0;
+				struct io_group *parent = NULL;
+
+				parent = iog_parent(iog);
+				if (parent)
+					nr_active = elv_iog_nr_active(parent);
+
+				io_group_path(iog, path, sizeof(path));
+				elv_log_ioq(efqd, ioq, "set_active, ioq grp=%s"
+				" nrgrps=%d QTt=0x%lx QTs=0x%lx GTt=0x%lx "
+				" GTs=0x%lx rq_queued=%d", path, nr_active,
+				ioq->entity.total_service,
+				ioq->entity.total_sector_service,
+				iog->entity.total_service,
+				iog->entity.total_sector_service,
+				ioq->nr_queued);
+			}
+#endif
 		ioq->slice_end = 0;
 
 		elv_clear_ioq_wait_request(ioq);
@@ -2920,6 +3169,22 @@ void elv_add_ioq_busy(struct elv_fq_data *efqd, struct io_queue *ioq)
 	efqd->busy_queues++;
 	if (elv_ioq_class_rt(ioq))
 		efqd->busy_rt_queues++;
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+		{
+			char path[128];
+			struct io_group *iog = ioq_to_io_group(ioq);
+			io_group_path(iog, path, sizeof(path));
+			elv_log(efqd, "add to busy: QTt=0x%lx QTs=0x%lx "
+				"ioq grp=%s GTt=0x%lx GTs=0x%lx rq_queued=%d",
+				ioq->entity.total_service,
+				ioq->entity.total_sector_service,
+				path,
+				iog->entity.total_service,
+				iog->entity.total_sector_service,
+				ioq->nr_queued);
+		}
+#endif
 }
 
 void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
@@ -2929,7 +3194,24 @@ void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
 
 	BUG_ON(!elv_ioq_busy(ioq));
 	BUG_ON(ioq->nr_queued);
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+		{
+			char path[128];
+			struct io_group *iog = ioq_to_io_group(ioq);
+			io_group_path(iog, path, sizeof(path));
+			elv_log_ioq(efqd, ioq, "del from busy: QTt=0x%lx "
+				"QTs=0x%lx ioq grp=%s GTt=0x%lx GTs=0x%lx "
+				"rq_queued=%d",
+				ioq->entity.total_service,
+				ioq->entity.total_sector_service,
+				path,
+				iog->entity.total_service,
+				iog->entity.total_sector_service,
+				ioq->nr_queued);
+		}
+#else
 	elv_log_ioq(efqd, ioq, "del from busy");
+#endif
 	elv_clear_ioq_busy(ioq);
 	BUG_ON(efqd->busy_queues == 0);
 	efqd->busy_queues--;
@@ -3157,6 +3439,16 @@ void elv_ioq_request_add(struct request_queue *q, struct request *rq)
 
 	elv_ioq_update_io_thinktime(ioq);
 	elv_ioq_update_idle_window(q->elevator, ioq, rq);
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+		{
+			char path[128];
+			struct io_group *iog = ioq_to_io_group(ioq);
+
+			io_group_path(iog, path, sizeof(path));
+			elv_log_ioq(efqd, ioq, "add rq: group path=%s "
+					"rq_queued=%d", path, ioq->nr_queued);
+		}
+#endif
 
 	if (ioq == elv_active_ioq(q->elevator)) {
 		/*
@@ -3364,7 +3656,7 @@ void *elv_fq_select_ioq(struct request_queue *q, int force)
 	}
 
 	/* We are waiting for this queue to become busy before it expires.*/
-	if (efqd->fairness && elv_ioq_wait_busy(ioq)) {
+	if (elv_ioq_wait_busy(ioq)) {
 		ioq = NULL;
 		goto keep_queue;
 	}
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 9062bfd..de0f6b0 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -249,6 +249,20 @@ struct io_group {
 
 	/* request list associated with the group */
 	struct request_list rl;
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+	/* How many times this group has been added to active tree */
+	unsigned long queue;
+
+	/* How long this group remained on active tree, in ms */
+	unsigned long queue_duration;
+
+	/* When was this group added to active tree */
+	unsigned long queue_start;
+
+	/* How many times this group has been removed from active tree */
+	unsigned long dequeue;
+#endif
 };
 
 struct io_policy_node {
-- 
1.6.0.1

[PATCH 20/20] io-controller: experimental debug patch for async queue wait before expiry

[Vivek Goyal]

o A debug patch which does wait for next IO from async queue once it
  becomes empty.

o For async writes, traffic seen by IO scheduler is not in proportion to
  the weight of the cgroup task/page belongs to. So if there are two processes
  doing heavy writeouts in two cgroups with weights 1000 and 500 respectively,
  then IO scheduler does not see more traffic/IO from higher weight cgroup
  even if IO scheduler tries to give it higher disk time. Effectively, the
  async queue belonging to higher weight cgroup becomes empty, and gets out
  of contention for disk and lower weight cgroup gets to use disk giving
  an impression in user space that higher weight cgroup did not get higher
  time to disk.

o This is more of a problem at page cache level where a higher weight
  process might be writing out the pages of lower weight process etc and
  should be fixed there.

o While we fix those issues, introducing this debug patch which allows one
  to idle on async queue (tunable via /sys/blolc/<disk>/queue/async_slice_idle)  so that once a higher weight queue becomes empty, instead of expiring it
  we try to wait for next request to come from that queue hence giving it
  higher disk time. A higher value of async_slice_idle, around 300ms, helps
  me get some right numbers for my setup. Note: higher disk time would not
  necessarily translate in more IO done as higher weight group is not pushing
  enough IO to io scheduler. It is just a debugging aid to prove correctness
  of IO controller by providing higher disk times to higher weight cgroup.

Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/blk-sysfs.c   |    7 +++++
 block/elevator-fq.c |   67 +++++++++++++++++++++++++++++++++++++++++++++++---
 block/elevator-fq.h |    7 +++++
 3 files changed, 77 insertions(+), 4 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index b60b76e..f245f33 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -314,6 +314,12 @@ static struct queue_sysfs_entry queue_slice_idle_entry = {
 	.store = elv_slice_idle_store,
 };
 
+static struct queue_sysfs_entry queue_async_slice_idle_entry = {
+	.attr = {.name = "async_slice_idle", .mode = S_IRUGO | S_IWUSR },
+	.show = elv_async_slice_idle_show,
+	.store = elv_async_slice_idle_store,
+};
+
 static struct queue_sysfs_entry queue_slice_sync_entry = {
 	.attr = {.name = "slice_sync", .mode = S_IRUGO | S_IWUSR },
 	.show = elv_slice_sync_show,
@@ -349,6 +355,7 @@ static struct attribute *default_attrs[] = {
 	&queue_iostats_entry.attr,
 #ifdef CONFIG_ELV_FAIR_QUEUING
 	&queue_slice_idle_entry.attr,
+	&queue_async_slice_idle_entry.attr,
 	&queue_slice_sync_entry.attr,
 	&queue_slice_async_entry.attr,
 	&queue_fairness_entry.attr,
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 6dd8683..f1179aa 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -20,6 +20,7 @@ const int elv_slice_sync = HZ / 10;
 int elv_slice_async = HZ / 25;
 const int elv_slice_async_rq = 2;
 int elv_slice_idle = HZ / 125;
+int elv_async_slice_idle = 0;
 static struct kmem_cache *elv_ioq_pool;
 
 /* Maximum Window length for updating average disk rate */
@@ -2677,6 +2678,46 @@ ssize_t elv_slice_idle_store(struct request_queue *q, const char *name,
 	return count;
 }
 
+/* Functions to show and store elv_idle_slice value through sysfs */
+ssize_t elv_async_slice_idle_show(struct request_queue *q, char *name)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	data = jiffies_to_msecs(efqd->elv_async_slice_idle);
+	spin_unlock_irqrestore(q->queue_lock, flags);
+	return sprintf(name, "%d\n", data);
+}
+
+ssize_t elv_async_slice_idle_store(struct request_queue *q, const char *name,
+			  size_t count)
+{
+	struct elv_fq_data *efqd;
+	unsigned int data;
+	unsigned long flags;
+
+	char *p = (char *)name;
+
+	data = simple_strtoul(p, &p, 10);
+
+	if (data < 0)
+		data = 0;
+	else if (data > INT_MAX)
+		data = INT_MAX;
+
+	data = msecs_to_jiffies(data);
+
+	spin_lock_irqsave(q->queue_lock, flags);
+	efqd = &q->elevator->efqd;
+	efqd->elv_async_slice_idle = data;
+	spin_unlock_irqrestore(q->queue_lock, flags);
+
+	return count;
+}
+
 /* Functions to show and store elv_slice_sync value through sysfs */
 ssize_t elv_slice_sync_show(struct request_queue *q, char *name)
 {
@@ -2930,8 +2971,10 @@ int elv_init_ioq(struct elevator_queue *eq, struct io_queue *ioq,
 		ioq->pid = current->pid;
 
 	ioq->sched_queue = sched_queue;
-	if (elv_gen_idling_enabled(eq) && is_sync && !elv_ioq_class_idle(ioq))
-		elv_mark_ioq_idle_window(ioq);
+	if (elv_gen_idling_enabled(eq) && !elv_ioq_class_idle(ioq)) {
+		if (is_sync || efqd->fairness)
+			elv_mark_ioq_idle_window(ioq);
+	}
 	bfq_init_entity(&ioq->entity, iog);
 	ioq->entity.budget = elv_prio_to_slice(efqd, ioq);
 	return 0;
@@ -3563,7 +3606,12 @@ void elv_ioq_arm_slice_timer(struct request_queue *q, int wait_for_busy)
 	/*
 	 * idle is disabled, either manually or by past process history
 	 */
-	if (!efqd->elv_slice_idle || !elv_ioq_idle_window(ioq))
+	if ((elv_ioq_sync(ioq) && !efqd->elv_slice_idle) ||
+			!elv_ioq_idle_window(ioq))
+		return;
+
+	/* If this is async queue and async_slice_idle is disabled, return */
+	if (!elv_ioq_sync(ioq) && !efqd->elv_async_slice_idle)
 		return;
 
 	/*
@@ -3572,7 +3620,10 @@ void elv_ioq_arm_slice_timer(struct request_queue *q, int wait_for_busy)
 	 */
 	if (wait_for_busy) {
 		elv_mark_ioq_wait_busy(ioq);
-		sl = efqd->elv_slice_idle;
+		if (elv_ioq_sync(ioq))
+			sl = efqd->elv_slice_idle;
+		else
+			sl = efqd->elv_async_slice_idle;
 		mod_timer(&efqd->idle_slice_timer, jiffies + sl);
 		elv_log_ioq(efqd, ioq, "arm idle: %lu wait busy=1", sl);
 		return;
@@ -3913,6 +3964,13 @@ void elv_ioq_completed_request(struct request_queue *q, struct request *rq)
 			goto done;
 		}
 
+		/* For async queue try to do wait busy */
+		if (efqd->fairness && !elv_ioq_sync(ioq) && !ioq->nr_queued
+		    && (elv_iog_nr_active(iog) <= 1)) {
+			elv_ioq_arm_slice_timer(q, 1);
+			goto done;
+		}
+
 		/*
 		 * If there are no requests waiting in this queue, and
 		 * there are other queues ready to issue requests, AND
@@ -4042,6 +4100,7 @@ int elv_init_fq_data(struct request_queue *q, struct elevator_queue *e)
 	efqd->elv_slice[0] = elv_slice_async;
 	efqd->elv_slice[1] = elv_slice_sync;
 	efqd->elv_slice_idle = elv_slice_idle;
+	efqd->elv_async_slice_idle = elv_async_slice_idle;
 	efqd->hw_tag = 1;
 
 	/* For the time being keep fairness enabled by default */
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index de0f6b0..1c99e83 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -339,6 +339,8 @@ struct elv_fq_data {
 	 * users of this functionality.
 	 */
 	unsigned int elv_slice_idle;
+	/* idle slice for async queue */
+	unsigned int elv_async_slice_idle;
 	struct timer_list idle_slice_timer;
 	struct work_struct unplug_work;
 
@@ -665,6 +667,11 @@ extern ssize_t elv_slice_idle_store(struct request_queue *q, const char *name,
 extern ssize_t elv_slice_sync_show(struct request_queue *q, char *name);
 extern ssize_t elv_slice_sync_store(struct request_queue *q, const char *name,
 						size_t count);
+
+extern ssize_t elv_async_slice_idle_show(struct request_queue *q, char *name);
+extern ssize_t elv_async_slice_idle_store(struct request_queue *q,
+					const char *name, size_t count);
+
 extern ssize_t elv_slice_async_show(struct request_queue *q, char *name);
 extern ssize_t elv_slice_async_store(struct request_queue *q, const char *name,
 						size_t count);
-- 
1.6.0.1

Re: [PATCH 15/20] io-controller: map async requests to appropriate cgroup

[Ryo Tsuruta]

Hi Vivek,

> +#ifdef CONFIG_TRACK_ASYNC_CONTEXT
> +	if (elv_bio_sync(bio)) {
> +		/* sync io. Determine cgroup from submitting task context. */
> +		cgroup = task_cgroup(current, io_subsys_id);
> +		return cgroup;
> +	}
> +
> +	/* Async io. Determine cgroup from with cgroup id stored in page */
> +	bio_cgroup_id = get_blkio_cgroup_id(bio);
> +
> +	if (!bio_cgroup_id)
> +		return NULL;
> +
> +	cgroup = blkio_cgroup_lookup(bio_cgroup_id);
> +#else
> +	cgroup = task_cgroup(current, io_subsys_id);
> +#endif
> +	return cgroup;
> +}

There is a case where a kernel thread (such as device-mapper drivers)
submits a sync IO instead of a task which originates the IO. I think
you should always use get_blkio_cgroup_id() to determine cgroup.

Thanks,
Ryo Tsuruta

Re: [PATCH 15/20] io-controller: map async requests to appropriate cgroup

[Vivek Goyal]

On Thu, May 28, 2009 at 06:27:40PM +0900, Ryo Tsuruta wrote:
> Hi Vivek,
> 
> > +#ifdef CONFIG_TRACK_ASYNC_CONTEXT
> > +	if (elv_bio_sync(bio)) {
> > +		/* sync io. Determine cgroup from submitting task context. */
> > +		cgroup = task_cgroup(current, io_subsys_id);
> > +		return cgroup;
> > +	}
> > +
> > +	/* Async io. Determine cgroup from with cgroup id stored in page */
> > +	bio_cgroup_id = get_blkio_cgroup_id(bio);
> > +
> > +	if (!bio_cgroup_id)
> > +		return NULL;
> > +
> > +	cgroup = blkio_cgroup_lookup(bio_cgroup_id);
> > +#else
> > +	cgroup = task_cgroup(current, io_subsys_id);
> > +#endif
> > +	return cgroup;
> > +}
> 
> There is a case where a kernel thread (such as device-mapper drivers)
> submits a sync IO instead of a task which originates the IO. I think
> you should always use get_blkio_cgroup_id() to determine cgroup.
> 

Hi Ryo,

Ok. Can you give some examples of drivers which are submitting reads in
different context al-together. You mentioned in the past that dm-crypt
looks like the one. How does current CFQ takes care of that. So if a 
BE prio 7 or an RT prio 0, task is submitting a READ, CFQ will not know it
and it will put that READ in the queue of the READ submitting device
mapper thread (may be BE prio 3 or 4)? 

Always determining the cgroup from bio, will make things slower at the 
same time complicated from the CFQ point of view. Right now cfq creates
and caches the queue pointer in the io context of the bio submitting task
and assumes sync requests are coming from that task/io context. Currently
there can only be one sync queue associated with one context. So if a single
thread is submitting reads (may be a worker thread) on behalf of other
processes, then we loose the io context information. In fact currently we
don't even carry ioprio and io class information in bio.

So looks like we need to carry task io context information also in bio
to be able to associate the bio to right queue at CFQ level. This makes
it bit more complicated. For the time being I will keep it in my TODO
list and handle it once other more severe problems have been taken care
of.

Thanks
Vivek

Re: [PATCH 15/20] io-controller: map async requests to appropriate cgroup

[Ryo Tsuruta]

Hi Vivek,

Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> On Thu, May 28, 2009 at 06:27:40PM +0900, Ryo Tsuruta wrote:
> > Hi Vivek,
> > 
> > > +#ifdef CONFIG_TRACK_ASYNC_CONTEXT
> > > +	if (elv_bio_sync(bio)) {
> > > +		/* sync io. Determine cgroup from submitting task context. */
> > > +		cgroup = task_cgroup(current, io_subsys_id);
> > > +		return cgroup;
> > > +	}
> > > +
> > > +	/* Async io. Determine cgroup from with cgroup id stored in page */
> > > +	bio_cgroup_id = get_blkio_cgroup_id(bio);
> > > +
> > > +	if (!bio_cgroup_id)
> > > +		return NULL;
> > > +
> > > +	cgroup = blkio_cgroup_lookup(bio_cgroup_id);
> > > +#else
> > > +	cgroup = task_cgroup(current, io_subsys_id);
> > > +#endif
> > > +	return cgroup;
> > > +}
> > 
> > There is a case where a kernel thread (such as device-mapper drivers)
> > submits a sync IO instead of a task which originates the IO. I think
> > you should always use get_blkio_cgroup_id() to determine cgroup.
> > 
> 
> Hi Ryo,
> 
> Ok. Can you give some examples of drivers which are submitting reads in
> different context al-together. You mentioned in the past that dm-crypt
> looks like the one. How does current CFQ takes care of that. So if a 
> BE prio 7 or an RT prio 0, task is submitting a READ, CFQ will not know it
> and it will put that READ in the queue of the READ submitting device
> mapper thread (may be BE prio 3 or 4)? 

In the case of READ, dm-raid1 submits read IOs in differenct context
under some conditions. dm-ioband also does it.

> Always determining the cgroup from bio, will make things slower at the 
> same time complicated from the CFQ point of view. Right now cfq creates
> and caches the queue pointer in the io context of the bio submitting task
> and assumes sync requests are coming from that task/io context. Currently
> there can only be one sync queue associated with one context. So if a single
> thread is submitting reads (may be a worker thread) on behalf of other
> processes, then we loose the io context information. In fact currently we
> don't even carry ioprio and io class information in bio.
> 
> So looks like we need to carry task io context information also in bio
> to be able to associate the bio to right queue at CFQ level. This makes
> it bit more complicated. For the time being I will keep it in my TODO
> list and handle it once other more severe problems have been taken care
> of.

There is a patchset which makes every bio points the iocontext of the
process which is originally generated an IO request.

  Date Tue, 22 Apr 2008 22:51:31 +0900 (JST)
  Subject [RFC][PATCH 1/10] I/O context inheritance
  From Hirokazu Takahashi <>
  http://lkml.org/lkml/2008/4/22/195

Thanks,
Ryo Tsuruta

Re: [PATCH 15/20] io-controller: map async requests to appropriate cgroup

[Vivek Goyal]

On Fri, May 29, 2009 at 12:17:37PM +0900, Ryo Tsuruta wrote:
> Hi Vivek,
> 
> Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > On Thu, May 28, 2009 at 06:27:40PM +0900, Ryo Tsuruta wrote:
> > > Hi Vivek,
> > > 
> > > > +#ifdef CONFIG_TRACK_ASYNC_CONTEXT
> > > > +	if (elv_bio_sync(bio)) {
> > > > +		/* sync io. Determine cgroup from submitting task context. */
> > > > +		cgroup = task_cgroup(current, io_subsys_id);
> > > > +		return cgroup;
> > > > +	}
> > > > +
> > > > +	/* Async io. Determine cgroup from with cgroup id stored in page */
> > > > +	bio_cgroup_id = get_blkio_cgroup_id(bio);
> > > > +
> > > > +	if (!bio_cgroup_id)
> > > > +		return NULL;
> > > > +
> > > > +	cgroup = blkio_cgroup_lookup(bio_cgroup_id);
> > > > +#else
> > > > +	cgroup = task_cgroup(current, io_subsys_id);
> > > > +#endif
> > > > +	return cgroup;
> > > > +}
> > > 
> > > There is a case where a kernel thread (such as device-mapper drivers)
> > > submits a sync IO instead of a task which originates the IO. I think
> > > you should always use get_blkio_cgroup_id() to determine cgroup.
> > > 
> > 
> > Hi Ryo,
> > 
> > Ok. Can you give some examples of drivers which are submitting reads in
> > different context al-together. You mentioned in the past that dm-crypt
> > looks like the one. How does current CFQ takes care of that. So if a 
> > BE prio 7 or an RT prio 0, task is submitting a READ, CFQ will not know it
> > and it will put that READ in the queue of the READ submitting device
> > mapper thread (may be BE prio 3 or 4)? 
> 
> In the case of READ, dm-raid1 submits read IOs in differenct context
> under some conditions. dm-ioband also does it.
> 
> > Always determining the cgroup from bio, will make things slower at the 
> > same time complicated from the CFQ point of view. Right now cfq creates
> > and caches the queue pointer in the io context of the bio submitting task
> > and assumes sync requests are coming from that task/io context. Currently
> > there can only be one sync queue associated with one context. So if a single
> > thread is submitting reads (may be a worker thread) on behalf of other
> > processes, then we loose the io context information. In fact currently we
> > don't even carry ioprio and io class information in bio.
> > 
> > So looks like we need to carry task io context information also in bio
> > to be able to associate the bio to right queue at CFQ level. This makes
> > it bit more complicated. For the time being I will keep it in my TODO
> > list and handle it once other more severe problems have been taken care
> > of.
> 
> There is a patchset which makes every bio points the iocontext of the
> process which is originally generated an IO request.
> 
>   Date Tue, 22 Apr 2008 22:51:31 +0900 (JST)
>   Subject [RFC][PATCH 1/10] I/O context inheritance
>   From Hirokazu Takahashi <>
>   http://lkml.org/lkml/2008/4/22/195

Ok, Thanks. This is good. So once above patches make to upstream, I will
just forward port my patches to make use of this infrastructure.

Thanks
Vivek

Re: [PATCH 15/20] io-controller: map async requests to appropriate cgroup

[Ryo Tsuruta]

Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> On Fri, May 29, 2009 at 12:17:37PM +0900, Ryo Tsuruta wrote:
> > Hi Vivek,
> > 
> > Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> > > On Thu, May 28, 2009 at 06:27:40PM +0900, Ryo Tsuruta wrote:
> > > > Hi Vivek,
> > > > 
> > > > > +#ifdef CONFIG_TRACK_ASYNC_CONTEXT
> > > > > +	if (elv_bio_sync(bio)) {
> > > > > +		/* sync io. Determine cgroup from submitting task context. */
> > > > > +		cgroup = task_cgroup(current, io_subsys_id);
> > > > > +		return cgroup;
> > > > > +	}
> > > > > +
> > > > > +	/* Async io. Determine cgroup from with cgroup id stored in page */
> > > > > +	bio_cgroup_id = get_blkio_cgroup_id(bio);
> > > > > +
> > > > > +	if (!bio_cgroup_id)
> > > > > +		return NULL;
> > > > > +
> > > > > +	cgroup = blkio_cgroup_lookup(bio_cgroup_id);
> > > > > +#else
> > > > > +	cgroup = task_cgroup(current, io_subsys_id);
> > > > > +#endif
> > > > > +	return cgroup;
> > > > > +}
> > > > 
> > > > There is a case where a kernel thread (such as device-mapper drivers)
> > > > submits a sync IO instead of a task which originates the IO. I think
> > > > you should always use get_blkio_cgroup_id() to determine cgroup.
> > > > 
> > > 
> > > Hi Ryo,
> > > 
> > > Ok. Can you give some examples of drivers which are submitting reads in
> > > different context al-together. You mentioned in the past that dm-crypt
> > > looks like the one. How does current CFQ takes care of that. So if a 
> > > BE prio 7 or an RT prio 0, task is submitting a READ, CFQ will not know it
> > > and it will put that READ in the queue of the READ submitting device
> > > mapper thread (may be BE prio 3 or 4)? 
> > 
> > In the case of READ, dm-raid1 submits read IOs in differenct context
> > under some conditions. dm-ioband also does it.
> > 
> > > Always determining the cgroup from bio, will make things slower at the 
> > > same time complicated from the CFQ point of view. Right now cfq creates
> > > and caches the queue pointer in the io context of the bio submitting task
> > > and assumes sync requests are coming from that task/io context. Currently
> > > there can only be one sync queue associated with one context. So if a single
> > > thread is submitting reads (may be a worker thread) on behalf of other
> > > processes, then we loose the io context information. In fact currently we
> > > don't even carry ioprio and io class information in bio.
> > > 
> > > So looks like we need to carry task io context information also in bio
> > > to be able to associate the bio to right queue at CFQ level. This makes
> > > it bit more complicated. For the time being I will keep it in my TODO
> > > list and handle it once other more severe problems have been taken care
> > > of.
> > 
> > There is a patchset which makes every bio points the iocontext of the
> > process which is originally generated an IO request.
> > 
> >   Date Tue, 22 Apr 2008 22:51:31 +0900 (JST)
> >   Subject [RFC][PATCH 1/10] I/O context inheritance
> >   From Hirokazu Takahashi <>
> >   http://lkml.org/lkml/2008/4/22/195
> 
> Ok, Thanks. This is good. So once above patches make to upstream, I will
> just forward port my patches to make use of this infrastructure.

If there are other people who also need this patchset, I'll consider
to port it to the latest kernel. I would like to hear opinions from
other people. I think it is useful for CFQ users.

Thanks,
Ryo Tsuruta

Re: [PATCH 01/20] io-controller: Documentation

[Balbir Singh]

* Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> [2009-05-26 18:41:50]:

> +	mount -t cgroup -o io,blkio none /cgroup
> +
> +- Create two cgroups
> +	mkdir -p /cgroup/test1/ /cgroup/test2
> +
> +- Set weights of group test1 and test2
> +	echo 1000 > /cgroup/test1/io.ioprio
> +	echo 500 > /cgroup/test2/io.ioprio
> +

I am not sure if anyone has asked this before, but are the numbers
arbitrary like shares or are they time units?

-- 
	Balbir

Re: [PATCH 01/20] io-controller: Documentation

[Vivek Goyal]

On Fri, May 29, 2009 at 11:42:52PM +0800, Balbir Singh wrote:
> * Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> [2009-05-26 18:41:50]:
> 
> > +	mount -t cgroup -o io,blkio none /cgroup
> > +
> > +- Create two cgroups
> > +	mkdir -p /cgroup/test1/ /cgroup/test2
> > +
> > +- Set weights of group test1 and test2
> > +	echo 1000 > /cgroup/test1/io.ioprio
> > +	echo 500 > /cgroup/test2/io.ioprio
> > +
> 
> I am not sure if anyone has asked this before, but are the numbers
> arbitrary like shares or are they time units?
> 

They are arbitrary like shares. 

This documentation file is still little wrong. "io.ioprio" should be replaced
with "io.weight". Gui pointed it out last time. Will fix it right away..

Thanks
Vivek

Re: [PATCH 10/20] io-conroller: Prepare elevator layer for single queue schedulers

[Gui Jianfeng]

Vivek Goyal wrote:
> +				e->ops->elevator_free_sched_queue_fn(e,
> +							sched_q);
> +				sched_q = NULL;
> +				goto queue_fail;
> +			}
> +		}
> +
> +		elv_init_ioq(e, ioq, iog, sched_q, IOPRIO_CLASS_BE, 4, 1);

It's better to use IOPRIO_NORM here.

Signed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
---
 block/elevator-fq.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index f1179aa..3c5f9da 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -2403,7 +2403,8 @@ alloc_ioq:
 			}
 		}
 
-		elv_init_ioq(e, ioq, iog, sched_q, IOPRIO_CLASS_BE, 4, 1);
+		elv_init_ioq(e, ioq, iog, sched_q, IOPRIO_CLASS_BE,
+			     IOPRIO_NORM, 1);
 		io_group_set_ioq(iog, ioq);
 		elv_mark_ioq_sync(ioq);
 		elv_get_iog(iog);
-- 
1.5.4.rc3

Re: [PATCH 10/20] io-conroller: Prepare elevator layer for single queue schedulers

[Vivek Goyal]

On Fri, Jun 05, 2009 at 05:17:07PM +0800, Gui Jianfeng wrote:
> Vivek Goyal wrote:
> > +				e->ops->elevator_free_sched_queue_fn(e,
> > +							sched_q);
> > +				sched_q = NULL;
> > +				goto queue_fail;
> > +			}
> > +		}
> > +
> > +		elv_init_ioq(e, ioq, iog, sched_q, IOPRIO_CLASS_BE, 4, 1);
> 
> It's better to use IOPRIO_NORM here.
> 

Sure. Queued up for next posting.

Thanks
Vivek

> Signed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  block/elevator-fq.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/block/elevator-fq.c b/block/elevator-fq.c
> index f1179aa..3c5f9da 100644
> --- a/block/elevator-fq.c
> +++ b/block/elevator-fq.c
> @@ -2403,7 +2403,8 @@ alloc_ioq:
>  			}
>  		}
>  
> -		elv_init_ioq(e, ioq, iog, sched_q, IOPRIO_CLASS_BE, 4, 1);
> +		elv_init_ioq(e, ioq, iog, sched_q, IOPRIO_CLASS_BE,
> +			     IOPRIO_NORM, 1);
>  		io_group_set_ioq(iog, ioq);
>  		elv_mark_ioq_sync(ioq);
>  		elv_get_iog(iog);
> -- 
> 1.5.4.rc3

Re: [PATCH 05/20] io-controller: Common hierarchical fair queuing code in elevaotor layer

[Gui Jianfeng]

Vivek Goyal wrote:
...
> +#ifdef CONFIG_GROUP_IOSCHED
> +extern int io_group_allow_merge(struct request *rq, struct bio *bio);
> +extern void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,

io_ioq_move is not used anymore, removing the dead code.

Singed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
---
 block/elevator-fq.h |   11 -----------
 1 files changed, 0 insertions(+), 11 deletions(-)

diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 1c99e83..24a3af9 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -537,8 +537,6 @@ static inline struct io_group *ioq_to_io_group(struct io_queue *ioq)
 
 #ifdef CONFIG_GROUP_IOSCHED
 extern int io_group_allow_merge(struct request *rq, struct bio *bio);
-extern void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
-					struct io_group *iog);
 static inline bfq_weight_t iog_weight(struct io_group *iog)
 {
 	return iog->entity.weight;
@@ -588,15 +586,6 @@ static inline int update_requeue(struct io_queue *ioq, int requeue)
 }
 
 #else /* !GROUP_IOSCHED */
-/*
- * No ioq movement is needed in case of flat setup. root io group gets cleaned
- * up upon elevator exit and before that it has been made sure that both
- * active and idle tree are empty.
- */
-static inline void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
-					struct io_group *iog)
-{
-}
 
 static inline int io_group_allow_merge(struct request *rq, struct bio *bio)
 {
-- 
1.5.4.rc3

Re: [PATCH 05/20] io-controller: Common hierarchical fair queuing code in elevaotor layer

[Vivek Goyal]

On Fri, Jun 05, 2009 at 05:36:16PM +0800, Gui Jianfeng wrote:
> Vivek Goyal wrote:
> ...
> > +#ifdef CONFIG_GROUP_IOSCHED
> > +extern int io_group_allow_merge(struct request *rq, struct bio *bio);
> > +extern void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
> 
> io_ioq_move is not used anymore, removing the dead code.
> 

Thanks Gui. Will include the patch in next posting.

Vivek

> Singed-off-by: Gui Jianfeng <guijianfeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> ---
>  block/elevator-fq.h |   11 -----------
>  1 files changed, 0 insertions(+), 11 deletions(-)
> 
> diff --git a/block/elevator-fq.h b/block/elevator-fq.h
> index 1c99e83..24a3af9 100644
> --- a/block/elevator-fq.h
> +++ b/block/elevator-fq.h
> @@ -537,8 +537,6 @@ static inline struct io_group *ioq_to_io_group(struct io_queue *ioq)
>  
>  #ifdef CONFIG_GROUP_IOSCHED
>  extern int io_group_allow_merge(struct request *rq, struct bio *bio);
> -extern void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
> -					struct io_group *iog);
>  static inline bfq_weight_t iog_weight(struct io_group *iog)
>  {
>  	return iog->entity.weight;
> @@ -588,15 +586,6 @@ static inline int update_requeue(struct io_queue *ioq, int requeue)
>  }
>  
>  #else /* !GROUP_IOSCHED */
> -/*
> - * No ioq movement is needed in case of flat setup. root io group gets cleaned
> - * up upon elevator exit and before that it has been made sure that both
> - * active and idle tree are empty.
> - */
> -static inline void io_ioq_move(struct elevator_queue *e, struct io_queue *ioq,
> -					struct io_group *iog)
> -{
> -}
>  
>  static inline int io_group_allow_merge(struct request *rq, struct bio *bio)
>  {
> -- 
> 1.5.4.rc3
> 

Re: [PATCH 16/20] io-controller: IO group refcounting support

[Gui Jianfeng]

Vivek Goyal wrote:
...
>  
>  /**
> @@ -436,7 +443,6 @@ static void bfq_idle_insert(struct io_service_tree *st,
>  {
>  	struct io_entity *first_idle = st->first_idle;
>  	struct io_entity *last_idle = st->last_idle;
> -	struct io_queue *ioq = io_entity_to_ioq(entity);
>  
>  	if (first_idle == NULL || bfq_gt(first_idle->finish, entity->finish))
>  		st->first_idle = entity;
> @@ -444,10 +450,6 @@ static void bfq_idle_insert(struct io_service_tree *st,
>  		st->last_idle = entity;
>  
>  	bfq_insert(&st->idle, entity);
> -
> -	/* Add this queue to idle list */
> -	if (ioq)
> -		list_add(&ioq->queue_list, &ioq->efqd->idle_list);
>  }
>  
>  /**
> @@ -723,8 +725,26 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
>  void bfq_deactivate_entity(struct io_entity *entity, int requeue)
>  {
>  	struct io_sched_data *sd;
> +	struct io_group *iog;
>  	struct io_entity *parent;
>  
> +	iog = container_of(entity->sched_data, struct io_group, sched_data);
> +
> +	/*
> +	 * Hold a reference to entity's iog until we are done. This function
> +	 * travels the hierarchy and we don't want to free up the group yet
> +	 * while we are traversing the hiearchy. It is possible that this
> +	 * group's cgroup has been removed hence cgroup reference is gone.
> +	 * If this entity was active entity, then its group will not be on
> +	 * any of the trees and it will be freed up the moment queue is
> +	 * freed up in __bfq_deactivate_entity().
> +	 *
> +	 * Hence, hold a reference, deactivate the hierarhcy of entities and
> +	 * then drop the reference which should free up the whole chain of
> +	 * groups.
> +	 */
> +	elv_get_iog(iog);
> +
>  	for_each_entity_safe(entity, parent) {
>  		sd = entity->sched_data;
>  
> @@ -736,21 +756,28 @@ void bfq_deactivate_entity(struct io_entity *entity, int requeue)
>  			 */
>  			break;
>  
> -		if (sd->next_active != NULL)
> +		if (sd->next_active != NULL) {
>  			/*
>  			 * The parent entity is still backlogged and
>  			 * the budgets on the path towards the root
>  			 * need to be updated.
>  			 */
> +			elv_put_iog(iog);
>  			goto update;
> +		}
>  
>  		/*
>  		 * If we reach there the parent is no more backlogged and
>  		 * we want to propagate the dequeue upwards.
> +		 *
> +		 * If entity's group has been marked for deletion, don't
> +		 * requeue the group in idle tree so that it can be freed.
>  		 */
> -		requeue = 1;
> +		if (!iog_deleting(iog))
> +			requeue = 1;

  Hi Vivek,

  IIUC, if the iog is marked deleting, all iogs in the hierarchy don't have a chance 
  to be requeued into idle trees. So, I wonder why do it like this? Why the upper iogs 
  can't be requeued to the idle tree?

-- 
Regards
Gui Jianfeng

Re: [PATCH 16/20] io-controller: IO group refcounting support

[Vivek Goyal]

On Mon, Jun 08, 2009 at 10:03:24AM +0800, Gui Jianfeng wrote:
> Vivek Goyal wrote:
> ...
> >  
> >  /**
> > @@ -436,7 +443,6 @@ static void bfq_idle_insert(struct io_service_tree *st,
> >  {
> >  	struct io_entity *first_idle = st->first_idle;
> >  	struct io_entity *last_idle = st->last_idle;
> > -	struct io_queue *ioq = io_entity_to_ioq(entity);
> >  
> >  	if (first_idle == NULL || bfq_gt(first_idle->finish, entity->finish))
> >  		st->first_idle = entity;
> > @@ -444,10 +450,6 @@ static void bfq_idle_insert(struct io_service_tree *st,
> >  		st->last_idle = entity;
> >  
> >  	bfq_insert(&st->idle, entity);
> > -
> > -	/* Add this queue to idle list */
> > -	if (ioq)
> > -		list_add(&ioq->queue_list, &ioq->efqd->idle_list);
> >  }
> >  
> >  /**
> > @@ -723,8 +725,26 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
> >  void bfq_deactivate_entity(struct io_entity *entity, int requeue)
> >  {
> >  	struct io_sched_data *sd;
> > +	struct io_group *iog;
> >  	struct io_entity *parent;
> >  
> > +	iog = container_of(entity->sched_data, struct io_group, sched_data);
> > +
> > +	/*
> > +	 * Hold a reference to entity's iog until we are done. This function
> > +	 * travels the hierarchy and we don't want to free up the group yet
> > +	 * while we are traversing the hiearchy. It is possible that this
> > +	 * group's cgroup has been removed hence cgroup reference is gone.
> > +	 * If this entity was active entity, then its group will not be on
> > +	 * any of the trees and it will be freed up the moment queue is
> > +	 * freed up in __bfq_deactivate_entity().
> > +	 *
> > +	 * Hence, hold a reference, deactivate the hierarhcy of entities and
> > +	 * then drop the reference which should free up the whole chain of
> > +	 * groups.
> > +	 */
> > +	elv_get_iog(iog);
> > +
> >  	for_each_entity_safe(entity, parent) {
> >  		sd = entity->sched_data;
> >  
> > @@ -736,21 +756,28 @@ void bfq_deactivate_entity(struct io_entity *entity, int requeue)
> >  			 */
> >  			break;
> >  
> > -		if (sd->next_active != NULL)
> > +		if (sd->next_active != NULL) {
> >  			/*
> >  			 * The parent entity is still backlogged and
> >  			 * the budgets on the path towards the root
> >  			 * need to be updated.
> >  			 */
> > +			elv_put_iog(iog);
> >  			goto update;
> > +		}
> >  
> >  		/*
> >  		 * If we reach there the parent is no more backlogged and
> >  		 * we want to propagate the dequeue upwards.
> > +		 *
> > +		 * If entity's group has been marked for deletion, don't
> > +		 * requeue the group in idle tree so that it can be freed.
> >  		 */
> > -		requeue = 1;
> > +		if (!iog_deleting(iog))
> > +			requeue = 1;
> 
>   Hi Vivek,
> 
>   IIUC, if the iog is marked deleting, all iogs in the hierarchy don't have a chance 
>   to be requeued into idle trees. So, I wonder why do it like this? Why the upper iogs 
>   can't be requeued to the idle tree?
> 

I think this is a bug Gui. Good catch. I think following should fix it.

Thanks
Vivek



Signed-off-by: Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 block/elevator-fq.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Index: linux16/block/elevator-fq.c
===================================================================
--- linux16.orig/block/elevator-fq.c	2009-06-06 14:21:11.000000000 -0400
+++ linux16/block/elevator-fq.c	2009-06-08 09:40:59.000000000 -0400
@@ -863,7 +863,7 @@ int __bfq_deactivate_entity(struct io_en
 void bfq_deactivate_entity(struct io_entity *entity, int requeue)
 {
 	struct io_sched_data *sd;
-	struct io_group *iog;
+	struct io_group *iog, *__iog;
 	struct io_entity *parent;
 
 	iog = container_of(entity->sched_data, struct io_group, sched_data);
@@ -911,8 +911,11 @@ void bfq_deactivate_entity(struct io_ent
 		 * If entity's group has been marked for deletion, don't
 		 * requeue the group in idle tree so that it can be freed.
 		 */
-		if (!iog_deleting(iog))
-			requeue = 1;
+		if (parent) {
+			__iog = container_of(parent, struct io_group, entity);
+			if (!iog_deleting(__iog))
+				requeue = 1;
+		}
 	}
 
 	elv_put_iog(iog);