[PATCH v3 1/4] block: Add concurrent positioning ranges support

Damien Le Moal
2021-07-26T01:38:20Z

The Concurrent Positioning Ranges VPD page (for SCSI) and Log (for ATA)
contain parameters describing the number of sets of contiguous LBAs that
can be served independently by a single LUN multi-actuator disk. This
patch provides the blk_queue_set_cranges() function allowing a device
driver to signal to the block layer that a disk has multiple actuators,
each one serving a contiguous range of sectors. To describe the set
of sector ranges representing the different actuators of a device, the
data type struct blk_cranges is introduced.

For a device with multiple actuators, a struct blk_cranges is attached
to the device request queue by the blk_queue_set_cranges() function. The
function blk_alloc_cranges() is provided for drivers to allocate this
structure.

The blk_cranges structure contains kobjects (struct kobject) to register
with sysfs the set of sector ranges defined by a device. On initial
device scan, this registration is done from blk_register_queue() using
the block layer internal function blk_register_cranges(). If a driver
calls blk_queue_set_cranges() for a registered queue, e.g. when a device
is revalidated, blk_queue_set_cranges() will execute
blk_register_cranges() to update the queue sysfs attribute files.

The sysfs file structure created starts from the cranges sub-directory
and contains the start sector and number of sectors served by an
actuator, with the information for each actuator grouped in one
directory per actuator. E.g. for a dual actuator drive, we have:

$ tree /sys/block/sdk/queue/cranges/
/sys/block/sdk/queue/cranges/
|-- 0
| |-- nr_sectors
| `-- sector
`-- 1
|-- nr_sectors
`-- sector

For a regular single actuator device, the cranges directory does not
exist.

Device revalidation may lead to changes to this structure and to the
attribute values. When manipulated, the queue sysfs_lock and
sysfs_dir_lock are held for atomicity, similarly to how the blk-mq and
elevator sysfs queue sub-directories are protected.

The code related to the management of cranges is added in the new
file block/blk-cranges.c.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
block/Makefile | 2 +-
block/blk-cranges.c | 295 +++++++++++++++++++++++++++++++++++++++++
block/blk-sysfs.c | 13 ++
block/blk.h | 3 +
include/linux/blkdev.h | 29 ++++
5 files changed, 341 insertions(+), 1 deletion(-)
create mode 100644 block/blk-cranges.c

diff --git a/block/Makefile b/block/Makefile
index bfbe4e13ca1e..e477e6ca9ea6 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -9,7 +9,7 @@ obj-$(CONFIG_BLOCK) := bio.o elevator.o blk-core.o blk-sysfs.o \
blk-lib.o blk-mq.o blk-mq-tag.o blk-stat.o \
blk-mq-sysfs.o blk-mq-cpumap.o blk-mq-sched.o ioctl.o \
genhd.o ioprio.o badblocks.o partitions/ blk-rq-qos.o \
- disk-events.o
+ disk-events.o blk-cranges.o

obj-$(CONFIG_BOUNCE) += bounce.o
obj-$(CONFIG_BLK_SCSI_REQUEST) += scsi_ioctl.o
diff --git a/block/blk-cranges.c b/block/blk-cranges.c
new file mode 100644
index 000000000000..deaa09e564f7
--- /dev/null
+++ b/block/blk-cranges.c
@@ -0,0 +1,295 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Block device concurrent positioning ranges.
+ *
+ * Copyright (C) 2021 Western Digital Corporation or its Affiliates.
+ */
+#include <linux/kernel.h>
+#include <linux/blkdev.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+
+#include "blk.h"
+
+static ssize_t blk_crange_sector_show(struct blk_crange *cr, char *page)
+{
+ return sprintf(page, "%llu\n", cr->sector);
+}
+
+static ssize_t blk_crange_nr_sectors_show(struct blk_crange *cr, char *page)
+{
+ return sprintf(page, "%llu\n", cr->nr_sectors);
+}
+
+struct blk_crange_sysfs_entry {
+ struct attribute attr;
+ ssize_t (*show)(struct blk_crange *cr, char *page);
+};
+
+static struct blk_crange_sysfs_entry blk_crange_sector_entry = {
+ .attr = { .name = "sector", .mode = 0444 },
+ .show = blk_crange_sector_show,
+};
+
+static struct blk_crange_sysfs_entry blk_crange_nr_sectors_entry = {
+ .attr = { .name = "nr_sectors", .mode = 0444 },
+ .show = blk_crange_nr_sectors_show,
+};
+
+static struct attribute *blk_crange_attrs[] = {
+ &blk_crange_sector_entry.attr,
+ &blk_crange_nr_sectors_entry.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(blk_crange);
+
+static ssize_t blk_crange_sysfs_show(struct kobject *kobj,
+ struct attribute *attr, char *page)
+{
+ struct blk_crange_sysfs_entry *entry;
+ struct blk_crange *cr;
+ struct request_queue *q;
+ ssize_t ret;
+
+ entry = container_of(attr, struct blk_crange_sysfs_entry, attr);
+ cr = container_of(kobj, struct blk_crange, kobj);
+ q = cr->queue;
+
+ mutex_lock(&q->sysfs_lock);
+ ret = entry->show(cr, page);
+ mutex_unlock(&q->sysfs_lock);
+
+ return ret;
+}
+
+static const struct sysfs_ops blk_crange_sysfs_ops = {
+ .show = blk_crange_sysfs_show,
+};
+
+/*
+ * Dummy release function to make kobj happy.
+ */
+static void blk_cranges_sysfs_nop_release(struct kobject *kobj)
+{
+}
+
+static struct kobj_type blk_crange_ktype = {
+ .sysfs_ops = &blk_crange_sysfs_ops,
+ .default_groups = blk_crange_groups,
+ .release = blk_cranges_sysfs_nop_release,
+};
+
+static struct kobj_type blk_cranges_ktype = {
+ .release = blk_cranges_sysfs_nop_release,
+};
+
+/**
+ * blk_register_cranges - register with sysfs a set of concurrent ranges
+ * @disk: Target disk
+ * @new_cranges: New set of concurrent ranges
+ *
+ * Register with sysfs a set of concurrent ranges for @disk. If @new_cranges
+ * is not NULL, this set of concurrent ranges is registered and the
+ * old set specified by q->cranges is unregistered. Otherwise, q->cranges
+ * is registered if it is not already.
+ */
+int blk_register_cranges(struct gendisk *disk, struct blk_cranges *new_cranges)
+{
+ struct request_queue *q = disk->queue;
+ struct blk_cranges *cranges;
+ int i, ret;
+
+ lockdep_assert_held(&q->sysfs_dir_lock);
+ lockdep_assert_held(&q->sysfs_lock);
+
+ /* If a new range set is specified, unregister the old one */
+ if (new_cranges) {
+ if (q->cranges)
+ blk_unregister_cranges(disk);
+ q->cranges = new_cranges;
+ }
+
+ cranges = q->cranges;
+ if (!cranges)
+ return 0;
+
+ /*
+ * At this point, q->cranges is the new set of sector ranges that needs
+ * to be registered with sysfs.
+ */
+ WARN_ON(cranges->sysfs_registered);
+ ret = kobject_init_and_add(&cranges->kobj, &blk_cranges_ktype,
+ &q->kobj, "%s", "cranges");
+ if (ret)
+ goto free;
+
+ for (i = 0; i < cranges->nr_ranges; i++) {
+ cranges->ranges[i].queue = q;
+ ret = kobject_init_and_add(&cranges->ranges[i].kobj,
+ &blk_crange_ktype, &cranges->kobj,
+ "%d", i);
+ if (ret)
+ goto delete_obj;
+ }
+
+ cranges->sysfs_registered = true;
+
+ return 0;
+
+delete_obj:
+ while (--i >= 0)
+ kobject_del(&cranges->ranges[i].kobj);
+ kobject_del(&cranges->kobj);
+free:
+ kfree(cranges);
+ q->cranges = NULL;
+ return ret;
+}
+
+void blk_unregister_cranges(struct gendisk *disk)
+{
+ struct request_queue *q = disk->queue;
+ struct blk_cranges *cranges = q->cranges;
+ int i;
+
+ lockdep_assert_held(&q->sysfs_dir_lock);
+ lockdep_assert_held(&q->sysfs_lock);
+
+ if (!cranges)
+ return;
+
+ if (cranges->sysfs_registered) {
+ for (i = 0; i < cranges->nr_ranges; i++)
+ kobject_del(&cranges->ranges[i].kobj);
+ kobject_del(&cranges->kobj);
+ }
+
+ kfree(cranges);
+ q->cranges = NULL;
+}
+
+static bool blk_check_ranges(struct gendisk *disk, struct blk_cranges *cr)
+{
+ sector_t capacity = get_capacity(disk);
+ sector_t min_sector = (sector_t)-1;
+ sector_t max_sector = 0;
+ int i;
+
+ /*
+ * Sector ranges may overlap but should overall contain all sectors
+ * within the disk capacity.
+ */
+ for (i = 0; i < cr->nr_ranges; i++) {
+ min_sector = min(min_sector, cr->ranges[i].sector);
+ max_sector = max(max_sector, cr->ranges[i].sector +
+ cr->ranges[i].nr_sectors);
+ }
+
+ if (min_sector != 0 || max_sector < capacity) {
+ pr_warn("Invalid concurrent ranges: missing sectors\n");
+ return false;
+ }
+
+ if (max_sector > capacity) {
+ pr_warn("Invalid concurrent ranges: beyond capacity\n");
+ return false;
+ }
+
+ return true;
+}
+
+static bool blk_cranges_changed(struct gendisk *disk, struct blk_cranges *new)
+{
+ struct blk_cranges *old = disk->queue->cranges;
+ int i;
+
+ if (!old)
+ return true;
+
+ if (old->nr_ranges != new->nr_ranges)
+ return true;
+
+ for (i = 0; i < old->nr_ranges; i++) {
+ if (new->ranges[i].sector != old->ranges[i].sector ||
+ new->ranges[i].nr_sectors != old->ranges[i].nr_sectors)
+ return true;
+ }
+
+ return false;
+}
+
+/**
+ * blk_alloc_cranges - Allocate a concurrent positioning range structure
+ * @disk: target disk
+ * @nr_ranges: Number of concurrent ranges
+ *
+ * Allocate a struct blk_cranges structure with @nr_ranges range descriptors.
+ */
+struct blk_cranges *blk_alloc_cranges(struct gendisk *disk, int nr_ranges)
+{
+ struct blk_cranges *cr;
+
+ cr = kzalloc_node(struct_size(cr, ranges, nr_ranges), GFP_KERNEL,
+ disk->queue->node);
+ if (cr)
+ cr->nr_ranges = nr_ranges;
+ return cr;
+}
+EXPORT_SYMBOL_GPL(blk_alloc_cranges);
+
+/**
+ * blk_queue_set_cranges - Set a disk concurrent positioning ranges
+ * @disk: target disk
+ * @cr: concurrent ranges structure
+ *
+ * Set the concurrant positioning ranges information of the request queue
+ * of @disk to @cr. If @cr is NULL and the concurrent ranges structure
+ * already set, if any, is cleared. If there are no differences between
+ * @cr and the concurrent ranges structure already set, @cr is freed.
+ */
+void blk_queue_set_cranges(struct gendisk *disk, struct blk_cranges *cr)
+{
+ struct request_queue *q = disk->queue;
+
+ if (WARN_ON_ONCE(cr && !cr->nr_ranges)) {
+ kfree(cr);
+ cr = NULL;
+ }
+
+ mutex_lock(&q->sysfs_dir_lock);
+ mutex_lock(&q->sysfs_lock);
+
+ if (cr) {
+ if (!blk_check_ranges(disk, cr)) {
+ kfree(cr);
+ cr = NULL;
+ goto reg;
+ }
+
+ if (!blk_cranges_changed(disk, cr)) {
+ kfree(cr);
+ goto unlock;
+ }
+ }
+
+ /*
+ * This may be called for a registered queue. E.g. during a device
+ * revalidation. If that is the case, we need to unregister the old
+ * set of concurrent ranges and register the new set. If the queue
+ * is not registered, the device request queue registration will
+ * register the ranges, so only swap in the new set and free the
+ * old one.
+ */
+reg:
+ if (blk_queue_registered(q)) {
+ blk_register_cranges(disk, cr);
+ } else {
+ swap(q->cranges, cr);
+ kfree(cr);
+ }
+
+unlock:
+ mutex_unlock(&q->sysfs_lock);
+ mutex_unlock(&q->sysfs_dir_lock);
+}
+EXPORT_SYMBOL_GPL(blk_queue_set_cranges);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 370d83c18057..aeac98ecc5a0 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -899,9 +899,21 @@ int blk_register_queue(struct gendisk *disk)
}

mutex_lock(&q->sysfs_lock);
+
+ ret = blk_register_cranges(disk, NULL);
+ if (ret) {
+ mutex_unlock(&q->sysfs_lock);
+ mutex_unlock(&q->sysfs_dir_lock);
+ kobject_del(&q->kobj);
+ blk_trace_remove_sysfs(dev);
+ kobject_put(&dev->kobj);
+ return ret;
+ }
+
if (q->elevator) {
ret = elv_register_queue(q, false);
if (ret) {
+ blk_unregister_cranges(disk);
mutex_unlock(&q->sysfs_lock);
mutex_unlock(&q->sysfs_dir_lock);
kobject_del(&q->kobj);
@@ -985,6 +997,7 @@ void blk_unregister_queue(struct gendisk *disk)
mutex_lock(&q->sysfs_lock);
if (q->elevator)
elv_unregister_queue(q);
+ blk_unregister_cranges(disk);
mutex_unlock(&q->sysfs_lock);
mutex_unlock(&q->sysfs_dir_lock);

diff --git a/block/blk.h b/block/blk.h
index 4b885c0f6708..650c0d87987c 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -368,4 +368,7 @@ extern struct device_attribute dev_attr_events;
extern struct device_attribute dev_attr_events_async;
extern struct device_attribute dev_attr_events_poll_msecs;

+int blk_register_cranges(struct gendisk *disk, struct blk_cranges *new_cranges);
+void blk_unregister_cranges(struct gendisk *disk);
+
#endif /* BLK_INTERNAL_H */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d3afea47ade6..d10352674d20 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -378,6 +378,29 @@ static inline int blkdev_zone_mgmt_ioctl(struct block_device *bdev,

#endif /* CONFIG_BLK_DEV_ZONED */

+/*
+ * Concurrent sector ranges: struct blk_crange describes range of
+ * contiguous sectors that can be served by independent resources on the
+ * device. The set of ranges defined in struct blk_cranges must overall
+ * include all sectors within the device capacity.
+ * For a device with multiple ranges, e.g. a single LUN multi-actuator HDD,
+ * requests targeting sectors in different ranges can be executed in parallel.
+ * A request can straddle a range boundary.
+ */
+struct blk_crange {
+ struct kobject kobj;
+ struct request_queue *queue;
+ sector_t sector;
+ sector_t nr_sectors;
+};
+
+struct blk_cranges {
+ struct kobject kobj;
+ bool sysfs_registered;
+ unsigned int nr_ranges;
+ struct blk_crange ranges[];
+};
+
struct request_queue {
struct request *last_merge;
struct elevator_queue *elevator;
@@ -570,6 +593,9 @@ struct request_queue {

#define BLK_MAX_WRITE_HINTS 5
u64 write_hints[BLK_MAX_WRITE_HINTS];
+
+ /* Concurrent sector ranges */
+ struct blk_cranges *cranges;
};

/* Keep blk_queue_flag_name[] in sync with the definitions below */
@@ -1163,6 +1189,9 @@ extern void blk_queue_required_elevator_features(struct request_queue *q,
extern bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
struct device *dev);

+struct blk_cranges *blk_alloc_cranges(struct gendisk *disk, int nr_ranges);
+void blk_queue_set_cranges(struct gendisk *disk, struct blk_cranges *cr);
+
/*
* Number of physical segments as sent to the device.
*
--
2.31.1