* [PATCH v1 1/5] btrfs: add READAHEAD extent state
2011-05-23 12:59 [PATCH v1 0/5] btrfs: generic readeahead interface Arne Jansen
@ 2011-05-23 12:59 ` Arne Jansen
2011-05-23 12:59 ` [PATCH v1 2/5] btrfs: state information for readahead Arne Jansen
` (3 subsequent siblings)
4 siblings, 0 replies; 11+ messages in thread
From: Arne Jansen @ 2011-05-23 12:59 UTC (permalink / raw)
To: chris.mason, linux-btrfs
Add a READAHEAD extent state flag.
Add a function to trigger a read with this flag set.
Reset the flag in the end_io hook
Signed-off-by: Arne Jansen <sensille@gmx.net>
---
fs/btrfs/disk-io.c | 36 ++++++++++++++++++++++++++++++++++++
fs/btrfs/disk-io.h | 2 ++
fs/btrfs/extent_io.c | 10 +++++++++-
fs/btrfs/extent_io.h | 1 +
4 files changed, 48 insertions(+), 1 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index fe5aec9..7753eb9 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -958,6 +958,42 @@ int readahead_tree_block(struct btrfs_root *root, u64 bytenr, u32 blocksize,
return ret;
}
+int reada_tree_block_flagged(struct btrfs_root *root, u64 bytenr, u32 blocksize,
+ int mirror_num, struct extent_buffer **eb)
+{
+ struct extent_buffer *buf = NULL;
+ struct inode *btree_inode = root->fs_info->btree_inode;
+ int ret;
+
+ buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
+ if (!buf)
+ return 0;
+
+ ret = set_extent_bits(&BTRFS_I(btree_inode)->io_tree,
+ bytenr, bytenr+blocksize-1,
+ EXTENT_READAHEAD, GFP_NOFS);
+ if (ret) {
+ printk(KERN_ERR "set_extent_bits failed with %d\n", ret);
+ free_extent_buffer(buf);
+ return ret;
+ }
+
+ read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree,
+ buf, 0, 0, btree_get_extent, mirror_num);
+
+ if (test_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags)) {
+ *eb = buf;
+ ret = -EIO;
+ } else if (extent_buffer_uptodate(
+ &BTRFS_I(buf->first_page->mapping->host)->io_tree,
+ buf, NULL)) {
+ *eb = buf;
+ } else {
+ free_extent_buffer(buf);
+ }
+ return ret;
+}
+
struct extent_buffer *btrfs_find_tree_block(struct btrfs_root *root,
u64 bytenr, u32 blocksize)
{
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 07b20dc..0c47d57 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -40,6 +40,8 @@ struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
u32 blocksize, u64 parent_transid);
int readahead_tree_block(struct btrfs_root *root, u64 bytenr, u32 blocksize,
u64 parent_transid);
+int reada_tree_block_flagged(struct btrfs_root *root, u64 bytenr, u32 blocksize,
+ int mirror_num, struct extent_buffer **eb);
struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root,
u64 bytenr, u32 blocksize);
int clean_tree_block(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 0d1196d..df0bc46 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1021,6 +1021,14 @@ int unlock_extent_cached(struct extent_io_tree *tree, u64 start, u64 end,
mask);
}
+int unlock_ra_extent_cached(struct extent_io_tree *tree, u64 start, u64 end,
+ struct extent_state **cached, gfp_t mask)
+{
+ return clear_extent_bit(tree, start, end,
+ EXTENT_READAHEAD | EXTENT_LOCKED, 1, 0, cached,
+ mask);
+}
+
int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask)
{
return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, NULL,
@@ -1795,7 +1803,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
set_extent_uptodate(tree, start, end, &cached,
GFP_ATOMIC);
}
- unlock_extent_cached(tree, start, end, &cached, GFP_ATOMIC);
+ unlock_ra_extent_cached(tree, start, end, &cached, GFP_ATOMIC);
if (whole_page) {
if (uptodate) {
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index af2d717..6317c78 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -17,6 +17,7 @@
#define EXTENT_NODATASUM (1 << 10)
#define EXTENT_DO_ACCOUNTING (1 << 11)
#define EXTENT_FIRST_DELALLOC (1 << 12)
+#define EXTENT_READAHEAD (1 << 13)
#define EXTENT_IOBITS (EXTENT_LOCKED | EXTENT_WRITEBACK)
#define EXTENT_CTLBITS (EXTENT_DO_ACCOUNTING | EXTENT_FIRST_DELALLOC)
--
1.7.3.4
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v1 3/5] btrfs: initial readahead code and prototypes
2011-05-23 12:59 [PATCH v1 0/5] btrfs: generic readeahead interface Arne Jansen
2011-05-23 12:59 ` [PATCH v1 1/5] btrfs: add READAHEAD extent state Arne Jansen
2011-05-23 12:59 ` [PATCH v1 2/5] btrfs: state information for readahead Arne Jansen
@ 2011-05-23 12:59 ` Arne Jansen
2011-05-26 10:14 ` David Sterba
2011-05-23 12:59 ` [PATCH v1 4/5] btrfs: hooks for readahead Arne Jansen
2011-05-23 12:59 ` [PATCH v1 5/5] btrfs: test ioctl " Arne Jansen
4 siblings, 1 reply; 11+ messages in thread
From: Arne Jansen @ 2011-05-23 12:59 UTC (permalink / raw)
To: chris.mason, linux-btrfs
This is the implementation for the generic read ahead framework.
To trigger a readahead, btrfs_reada_add must be called. It will start
a read ahead for the given range [start, end) on tree root. The returned
handle can either be used to wait on the readahead to finish
(btrfs_reada_wait), or to send it to the background (btrfs_reada_detach).
The read ahead works as follows:
On btrfs_reada_add, the root of the tree is inserted into a radix_tree.
reada_start_machine will then search for extents to prefetch and trigger
some reads. When a read finishes for a node, all contained node/leaf
pointers that lie in the given range will also be enqueued. The reads will
be triggered in sequential order, thus giving a big win over a naive
enumeration. It will also make use of multi-device layouts. Each disk
will have its on read pointer and all disks will by utilized in parallel.
Also will no two disks read both sides of a mirror simultaneously, as this
would waste seeking capacity. Instead both disks will read different parts
of the filesystem.
Any number of readaheads can be started in parallel. The read order will be
determined globally, i.e. 2 parallel readaheads will normally finish faster
than the 2 started one after another.
Signed-off-by: Arne Jansen <sensille@gmx.net>
---
fs/btrfs/Makefile | 2 +-
fs/btrfs/ctree.h | 9 +
fs/btrfs/reada.c | 963 +++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 973 insertions(+), 1 deletions(-)
diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 31610ea..3e9ed71 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -7,4 +7,4 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
extent_map.o sysfs.o struct-funcs.o xattr.o ordered-data.o \
extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
export.o tree-log.o acl.o free-space-cache.o zlib.o lzo.o \
- compression.o delayed-ref.o relocation.o
+ compression.o delayed-ref.o relocation.o reada.o
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 4a33e30..0de44a5 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2641,4 +2641,13 @@ void btrfs_reloc_pre_snapshot(struct btrfs_trans_handle *trans,
u64 *bytes_to_reserve);
void btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
struct btrfs_pending_snapshot *pending);
+
+/* reada.c */
+void *btrfs_reada_add(struct btrfs_root *root, struct btrfs_key *start,
+ struct btrfs_key *end);
+int btrfs_reada_wait(void *handle);
+void btrfs_reada_detach(void *handle);
+int btree_readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
+ u64 start, int err);
+
#endif
diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
new file mode 100644
index 0000000..1801dd3
--- /dev/null
+++ b/fs/btrfs/reada.c
@@ -0,0 +1,963 @@
+/*
+ * Copyright (C) 2011 STRATO. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/sched.h>
+#include <linux/pagemap.h>
+#include <linux/writeback.h>
+#include <linux/blkdev.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include "ctree.h"
+#include "volumes.h"
+#include "disk-io.h"
+
+/*
+ * This is the implementation for the generic read ahead framework.
+ *
+ * To trigger a readahead, btrfs_reada_add must be called. It will start
+ * a read ahead for the given range [start, end) on tree root. The returned
+ * handle can either be used to wait on the readahead to finish
+ * (btrfs_reada_wait), or to send it to the background (btrfs_reada_detach).
+ *
+ * The read ahead works as follows:
+ * On btrfs_reada_add, the root of the tree is inserted into a radix_tree.
+ * reada_start_machine will then search for extents to prefetch and trigger
+ * some reads. When a read finishes for a node, all contained node/leaf
+ * pointers that lie in the given range will also be enqueued. The reads will
+ * be triggered in sequential order, thus giving a big win over a naive
+ * enumeration. It will also make use of multi-device layouts. Each disk
+ * will have its on read pointer and all disks will by utilized in parallel.
+ * Also will no two disks read both sides of a mirror simultaneously, as this
+ * would waste seeking capacity. Instead both disks will read different parts
+ * of the filesystem.
+ * Any number of readaheads can be started in parallel. The read order will be
+ * determined globally, i.e. 2 parallel readaheads will normally finish faster
+ * than the 2 started one after another.
+ */
+
+#define MAX_MIRRORS 2
+#define MAX_IN_FLIGHT 6
+
+struct reada_control {
+ struct btrfs_root *root; /* tree to prefetch */
+ struct btrfs_key key_start;
+ struct btrfs_key key_end; /* exclusive */
+ spinlock_t lock;
+ u64 elems;
+ u64 read_total;
+ struct kref refcnt;
+ wait_queue_head_t wait;
+};
+
+struct reada_extctl {
+ struct list_head list;
+ struct reada_control *rc;
+ u64 generation;
+};
+
+struct reada_extent {
+ u64 logical;
+ u32 blocksize;
+ int err;
+ struct list_head extctl;
+ struct kref refcnt;
+ spinlock_t lock;
+ struct reada_zone *zones[MAX_MIRRORS];
+ int nzones;
+ struct btrfs_device *scheduled_for;
+};
+
+struct reada_zone {
+ u64 start;
+ u64 end;
+ u64 elems;
+ struct list_head list;
+ spinlock_t lock;
+ int locked;
+ struct btrfs_device *device;
+ struct btrfs_device *devs[MAX_MIRRORS]; /* full list, incl self */
+ int ndevs;
+ struct kref refcnt;
+};
+
+struct reada_machine_work {
+ struct btrfs_work work;
+ struct btrfs_fs_info *fs_info;
+};
+
+static void reada_extent_put(struct btrfs_fs_info *, struct reada_extent *);
+static void reada_zone_put(struct reada_zone *);
+static void reada_control_put(struct reada_control *rc);
+static void reada_start_machine(struct btrfs_fs_info *fs_info);
+
+static int reada_key_cmp(struct btrfs_key *a, struct btrfs_key *b)
+{
+ if (a->objectid > b->objectid)
+ return 1;
+ if (a->objectid < b->objectid)
+ return -1;
+ if (a->type > b->type)
+ return 1;
+ if (a->type < b->type)
+ return -1;
+ if (a->offset > b->offset)
+ return 1;
+ if (a->offset < b->offset)
+ return -1;
+ return 0;
+}
+
+static int reada_add_block(struct reada_control *rc, u64 logical,
+ int level, u64 generation);
+
+/* recurses */
+/* in case of err, eb might be NULL */
+static int __readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
+ u64 start, int err)
+{
+ int level = 0;
+ int nritems;
+ int i;
+ struct btrfs_key key;
+ u64 bytenr;
+ u64 generation;
+ struct reada_extent *re;
+ struct btrfs_fs_info *fs_info = root->fs_info;
+ struct list_head list;
+ unsigned long index = start >> PAGE_CACHE_SHIFT;
+ struct btrfs_device *for_dev;
+
+ if (eb)
+ level = btrfs_header_level(eb);
+
+ /* find extent */
+ spin_lock(&fs_info->reada_lock);
+ re = radix_tree_lookup(&fs_info->reada_tree, index);
+ if (re)
+ kref_get(&re->refcnt);
+ spin_unlock(&fs_info->reada_lock);
+
+ if (!re)
+ return -1;
+
+ spin_lock(&re->lock);
+ /*
+ * just take the full list from the extent. afterwards we
+ * don't need the lock anymore
+ */
+ list_replace_init(&re->extctl, &list);
+ for_dev = re->scheduled_for;
+ re->scheduled_for = NULL;
+ spin_unlock(&re->lock);
+
+ if (err == 0) {
+ nritems = level ? btrfs_header_nritems(eb) : 0;
+ generation = btrfs_header_generation(eb);
+ /*
+ * FIXME: currently we just set nritems to 0 if this is a leaf,
+ * effectively ignoring the content. In a next step we could
+ * trigger more readahead depending from the content, e.g.
+ * fetch the checksums for the extents in the leaf.
+ */
+ } else {
+ /*
+ * this is the error case, the extent buffer has not been
+ * read correctly. We won't access anything from it and
+ * just cleanup our data structures. Effectively this will
+ * cut the branch below this node from read ahead.
+ */
+ nritems = 0;
+ generation = 0;
+ }
+
+ for (i = 0; i < nritems; i++) {
+ struct reada_extctl *rec;
+ u64 n_gen;
+
+ btrfs_node_key_to_cpu(eb, &key, i);
+ bytenr = btrfs_node_blockptr(eb, i);
+ n_gen = btrfs_node_ptr_generation(eb, i);
+
+ list_for_each_entry(rec, &list, list) {
+ struct reada_control *rc = rec->rc;
+
+ /*
+ * if the generation doesn't match, just ignore this
+ * extctl. This will probably cut off a branch from
+ * prefetch. Alternatively one could start a new (sub-)
+ * prefetch for this branch, starting again from root.
+ * FIXME: move the generation check out of this loop
+ */
+ if (rec->generation == generation &&
+ reada_key_cmp(&key, &rc->key_start) >= 0 &&
+ reada_key_cmp(&key, &rc->key_end) < 0) {
+ reada_add_block(rc, bytenr, level - 1, n_gen);
+ }
+ }
+ }
+ /*
+ * free extctl records
+ */
+ while (!list_empty(&list)) {
+ struct reada_control *rc;
+ struct reada_extctl *rec;
+
+ rec = list_first_entry(&list, struct reada_extctl,
+ list);
+ list_del(&rec->list);
+ rc = rec->rc;
+ kfree(rec);
+
+ kref_get(&rc->refcnt);
+ spin_lock(&rc->lock);
+ --rc->elems;
+ if (rc->elems == 0) {
+ reada_control_put(rc);
+ wake_up(&rc->wait);
+ }
+ spin_unlock(&rc->lock);
+ reada_control_put(rc);
+
+ reada_extent_put(fs_info, re); /* one ref for each entry */
+ }
+ reada_extent_put(fs_info, re); /* our ref */
+ if (for_dev)
+ atomic_dec(&for_dev->reada_in_flight);
+
+ return 0;
+}
+
+/*
+ * start is passed separately in case eb in NULL, which may be the case with
+ * failed I/O
+ */
+int btree_readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
+ u64 start, int err)
+{
+ int ret;
+
+ ret = __readahead_hook(root, eb, start, err);
+
+ reada_start_machine(root->fs_info);
+
+ return ret;
+}
+
+static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
+ struct btrfs_device *dev, u64 logical,
+ struct btrfs_multi_bio *multi)
+{
+ int ret;
+ int looped = 0;
+ struct reada_zone *zone;
+ struct btrfs_block_group_cache *cache = NULL;
+ u64 start;
+ u64 end;
+ int i;
+
+again:
+ zone = NULL;
+ spin_lock(&fs_info->reada_lock);
+ ret = radix_tree_gang_lookup(&dev->reada_zones, (void **)&zone,
+ logical >> PAGE_CACHE_SHIFT, 1);
+ if (ret == 1)
+ kref_get(&zone->refcnt);
+ spin_unlock(&fs_info->reada_lock);
+
+ if (ret == 1) {
+ if (logical >= zone->start && logical < zone->end)
+ return zone;
+ spin_lock(&fs_info->reada_lock);
+ reada_zone_put(zone);
+ spin_unlock(&fs_info->reada_lock);
+ }
+
+ if (looped)
+ return NULL;
+
+ cache = btrfs_lookup_block_group(fs_info, logical);
+ if (!cache)
+ return NULL;
+
+ start = cache->key.objectid;
+ end = start + cache->key.offset - 1;
+ btrfs_put_block_group(cache);
+
+ zone = kzalloc(sizeof(*zone), GFP_NOFS);
+ if (!zone)
+ return NULL;
+
+ zone->start = start;
+ zone->end = end;
+ INIT_LIST_HEAD(&zone->list);
+ spin_lock_init(&zone->lock);
+ zone->locked = 0;
+ kref_init(&zone->refcnt);
+ zone->elems = 0;
+ zone->device = dev; /* our device always sits at index 0 */
+ for (i = 0; i < multi->num_stripes; ++i) {
+ /* bounds have already been checked */
+ zone->devs[i] = multi->stripes[i].dev;
+ }
+ zone->ndevs = multi->num_stripes;
+
+ spin_lock(&fs_info->reada_lock);
+ ret = radix_tree_insert(&dev->reada_zones,
+ (unsigned long)zone->end >> PAGE_CACHE_SHIFT,
+ zone);
+ spin_unlock(&fs_info->reada_lock);
+
+ if (ret) {
+ kfree(zone);
+ looped = 1;
+ goto again;
+ }
+
+ return zone;
+}
+
+static struct reada_extent *reada_find_extent(struct btrfs_root *root,
+ u64 logical, int level)
+{
+ int ret;
+ int looped = 0;
+ struct reada_extent *re = NULL;
+ struct btrfs_fs_info *fs_info = root->fs_info;
+ struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
+ struct btrfs_multi_bio *multi = NULL;
+ struct btrfs_device *dev;
+ u32 blocksize;
+ u64 length;
+ int nzones = 0;
+ int i;
+ unsigned long index = logical >> PAGE_CACHE_SHIFT;
+
+again:
+ spin_lock(&fs_info->reada_lock);
+ re = radix_tree_lookup(&fs_info->reada_tree, index);
+ if (re)
+ kref_get(&re->refcnt);
+ spin_unlock(&fs_info->reada_lock);
+
+ if (re || looped)
+ return re;
+
+ re = kzalloc(sizeof(*re), GFP_NOFS);
+ if (!re)
+ return NULL;
+
+ blocksize = btrfs_level_size(root, level);
+ re->logical = logical;
+ re->blocksize = blocksize;
+ INIT_LIST_HEAD(&re->extctl);
+ spin_lock_init(&re->lock);
+ kref_init(&re->refcnt);
+
+ /*
+ * map block
+ */
+ length = blocksize;
+ ret = btrfs_map_block(map_tree, REQ_WRITE, logical, &length, &multi, 0);
+ if (ret || !multi || length < blocksize)
+ goto error;
+
+ if (multi->num_stripes > MAX_MIRRORS) {
+ printk(KERN_ERR "btrfs readahead: more than %d copies not "
+ "supported", MAX_MIRRORS);
+ goto error;
+ }
+
+ for (nzones = 0; nzones < multi->num_stripes; ++nzones) {
+ struct reada_zone *zone;
+
+ dev = multi->stripes[nzones].dev;
+ zone = reada_find_zone(fs_info, dev, logical, multi);
+ if (!zone)
+ break;
+
+ re->zones[nzones] = zone;
+ spin_lock(&zone->lock);
+ if (!zone->elems)
+ kref_get(&zone->refcnt);
+ ++zone->elems;
+ spin_unlock(&zone->lock);
+ spin_lock(&fs_info->reada_lock);
+ reada_zone_put(zone);
+ spin_unlock(&fs_info->reada_lock);
+ }
+ re->nzones = nzones;
+ if (nzones == 0) {
+ /* not a single zone found, error and out */
+ goto error;
+ }
+
+ /* insert extent in reada_tree + all per-device trees, all or nothing */
+ spin_lock(&fs_info->reada_lock);
+ ret = radix_tree_insert(&fs_info->reada_tree, index, re);
+ if (ret) {
+ spin_unlock(&fs_info->reada_lock);
+ if (ret != -ENOMEM) {
+ /* someone inserted the extent in the meantime */
+ looped = 1;
+ }
+ goto error;
+ }
+ for (i = 0; i < nzones; ++i) {
+ dev = multi->stripes[i].dev;
+ ret = radix_tree_insert(&dev->reada_extents, index, re);
+ if (ret) {
+ while (--i >= 0) {
+ dev = multi->stripes[i].dev;
+ BUG_ON(dev == NULL);
+ radix_tree_delete(&dev->reada_extents, index);
+ }
+ BUG_ON(fs_info == NULL);
+ radix_tree_delete(&fs_info->reada_tree, index);
+ spin_unlock(&fs_info->reada_lock);
+ goto error;
+ }
+ }
+ spin_unlock(&fs_info->reada_lock);
+
+ return re;
+
+error:
+ while (nzones) {
+ struct reada_zone *zone;
+
+ --nzones;
+ zone = re->zones[nzones];
+ kref_get(&zone->refcnt);
+ spin_lock(&zone->lock);
+ --zone->elems;
+ if (zone->elems == 0) {
+ /*
+ * no fs_info->reada_lock needed, as this can't be
+ * the last ref
+ */
+ reada_zone_put(zone);
+ }
+ spin_unlock(&zone->lock);
+
+ spin_lock(&fs_info->reada_lock);
+ reada_zone_put(zone);
+ spin_unlock(&fs_info->reada_lock);
+ }
+ kfree(re);
+ if (looped)
+ goto again;
+ return NULL;
+}
+
+static void reada_kref_dummy(struct kref *kr)
+{
+}
+
+static void reada_extent_put(struct btrfs_fs_info *fs_info,
+ struct reada_extent *re)
+{
+ int i;
+ unsigned long index = re->logical >> PAGE_CACHE_SHIFT;
+
+ spin_lock(&fs_info->reada_lock);
+ if (!kref_put(&re->refcnt, reada_kref_dummy)) {
+ spin_unlock(&fs_info->reada_lock);
+ return;
+ }
+
+ radix_tree_delete(&fs_info->reada_tree, index);
+ for (i = 0; i < re->nzones; ++i) {
+ struct reada_zone *zone = re->zones[i];
+
+ radix_tree_delete(&zone->device->reada_extents, index);
+ }
+
+ spin_unlock(&fs_info->reada_lock);
+
+ for (i = 0; i < re->nzones; ++i) {
+ struct reada_zone *zone = re->zones[i];
+
+ kref_get(&zone->refcnt);
+ spin_lock(&zone->lock);
+ --zone->elems;
+ if (zone->elems == 0) {
+ /* no fs_info->reada_lock needed, as this can't be
+ * the last ref */
+ reada_zone_put(zone);
+ }
+ spin_unlock(&zone->lock);
+
+ spin_lock(&fs_info->reada_lock);
+ reada_zone_put(zone);
+ spin_unlock(&fs_info->reada_lock);
+ }
+ if (re->scheduled_for)
+ atomic_dec(&re->scheduled_for->reada_in_flight);
+
+ kfree(re);
+}
+
+/* call it with fs_info->reada_lock held */
+static void reada_zone_put(struct reada_zone *zone)
+{
+ if (!kref_put(&zone->refcnt, reada_kref_dummy))
+ return;
+
+ radix_tree_delete(&zone->device->reada_zones,
+ zone->end >> PAGE_CACHE_SHIFT);
+
+ kfree(zone);
+
+ return;
+}
+
+static void reada_control_put(struct reada_control *rc)
+{
+ if (kref_put(&rc->refcnt, reada_kref_dummy)) {
+ kfree(rc);
+ return;
+ }
+}
+
+static int reada_add_block(struct reada_control *rc, u64 logical, int level,
+ u64 generation)
+{
+ struct btrfs_root *root = rc->root;
+ struct reada_extent *re;
+ struct reada_extctl *rec;
+
+ re = reada_find_extent(root, logical, level); /* takes one ref */
+ if (!re)
+ return -1;
+
+ rec = kzalloc(sizeof(*rec), GFP_NOFS);
+ if (!rec) {
+ reada_extent_put(root->fs_info, re);
+ return -1;
+ }
+
+ rec->rc = rc;
+ rec->generation = generation;
+ spin_lock(&rc->lock);
+ ++rc->elems;
+ spin_unlock(&rc->lock);
+
+ spin_lock(&re->lock);
+ list_add_tail(&rec->list, &re->extctl);
+ spin_unlock(&re->lock);
+
+ /* leave the ref on the extent */
+
+ return 0;
+}
+
+/*
+ * called with fs_info->reada_lock held
+ */
+static void reada_peer_zones_set_lock(struct reada_zone *zone, int lock)
+{
+ int i;
+ unsigned long index = zone->end >> PAGE_CACHE_SHIFT;
+
+ for (i = 0; i < zone->ndevs; ++i) {
+ struct reada_zone *peer;
+ peer = radix_tree_lookup(&zone->devs[i]->reada_zones, index);
+ if (peer && peer->device != zone->device)
+ peer->locked = lock;
+ }
+}
+
+/*
+ * called with fs_info->reada_lock held
+ */
+static int reada_pick_zone(struct btrfs_device *dev)
+{
+ struct reada_zone *top_zone = NULL;
+ struct reada_zone *top_locked_zone = NULL;
+ u64 top_elems = 0;
+ u64 top_locked_elems = 0;
+ unsigned long index = 0;
+ int ret;
+
+ if (dev->reada_curr_zone) {
+ reada_peer_zones_set_lock(dev->reada_curr_zone, 0);
+ reada_zone_put(dev->reada_curr_zone);
+ dev->reada_curr_zone = NULL;
+ }
+ /* pick the zone with the most elements */
+ while (1) {
+ struct reada_zone *zone;
+
+ ret = radix_tree_gang_lookup(&dev->reada_zones,
+ (void **)&zone, index, 1);
+ if (ret == 0)
+ break;
+ index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
+ if (zone->locked) {
+ if (zone->elems > top_locked_elems) {
+ top_locked_elems = zone->elems;
+ top_locked_zone = zone;
+ }
+ } else {
+ if (zone->elems > top_elems) {
+ top_elems = zone->elems;
+ top_zone = zone;
+ }
+ }
+ }
+ if (top_zone)
+ dev->reada_curr_zone = top_zone;
+ else if (top_locked_zone)
+ dev->reada_curr_zone = top_locked_zone;
+ else
+ return 0;
+
+ dev->reada_next = dev->reada_curr_zone->start;
+ kref_get(&dev->reada_curr_zone->refcnt);
+ reada_peer_zones_set_lock(dev->reada_curr_zone, 1);
+
+ return 1;
+}
+
+static int reada_start_machine_dev(struct btrfs_fs_info *fs_info,
+ struct btrfs_device *dev)
+{
+ struct reada_extent *re = NULL;
+ int mirror_num = 0;
+ struct extent_buffer *eb = NULL;
+ u64 logical;
+ u32 blocksize;
+ int ret;
+ int i;
+ int need_kick = 0;
+
+ spin_lock(&fs_info->reada_lock);
+ if (dev->reada_curr_zone == NULL) {
+ ret = reada_pick_zone(dev);
+ if (!ret) {
+ spin_unlock(&fs_info->reada_lock);
+ return 0;
+ }
+ }
+ /*
+ * FIXME currently we issue the reads one extent at a time. If we have
+ * a contiguous block of extents, we could also coagulate them or use
+ * plugging to speed things up
+ */
+ ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
+ dev->reada_next >> PAGE_CACHE_SHIFT, 1);
+ if (ret == 0 || re->logical >= dev->reada_curr_zone->end) {
+ ret = reada_pick_zone(dev);
+ if (!ret) {
+ spin_unlock(&fs_info->reada_lock);
+ return 0;
+ }
+ re = NULL;
+ ret = radix_tree_gang_lookup(&dev->reada_extents, (void **)&re,
+ dev->reada_next >> PAGE_CACHE_SHIFT, 1);
+ }
+ if (ret == 0) {
+ spin_unlock(&fs_info->reada_lock);
+ return 0;
+ }
+ dev->reada_next = re->logical + re->blocksize;
+ kref_get(&re->refcnt);
+
+ spin_unlock(&fs_info->reada_lock);
+
+ /*
+ * find mirror num
+ */
+ for (i = 0; i < re->nzones; ++i) {
+ if (re->zones[i]->device == dev) {
+ mirror_num = i + 1;
+ break;
+ }
+ }
+ logical = re->logical;
+ blocksize = re->blocksize;
+
+ spin_lock(&re->lock);
+ if (re->scheduled_for == NULL) {
+ re->scheduled_for = dev;
+ need_kick = 1;
+ }
+ spin_unlock(&re->lock);
+
+ reada_extent_put(fs_info, re);
+
+ if (!need_kick)
+ return 0;
+
+ atomic_inc(&dev->reada_in_flight);
+ ret = reada_tree_block_flagged(fs_info->extent_root, logical, blocksize,
+ mirror_num, &eb);
+ if (eb) {
+ __readahead_hook(fs_info->extent_root, eb, eb->start, ret);
+ free_extent_buffer(eb);
+ }
+
+ return 1;
+
+}
+
+static void reada_start_machine_worker(struct btrfs_work *work)
+{
+ struct reada_machine_work *rmw;
+ struct btrfs_fs_info *fs_info;
+
+ rmw = container_of(work, struct reada_machine_work, work);
+ fs_info = rmw->fs_info;
+
+ kfree(rmw);
+
+ reada_start_machine(fs_info);
+}
+
+static void reada_start_machine(struct btrfs_fs_info *fs_info)
+{
+ struct btrfs_device *device;
+ struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+ u64 enqueued;
+ u64 total = 0;
+ int i;
+
+again:
+ do {
+ enqueued = 0;
+ list_for_each_entry(device, &fs_devices->devices, dev_list) {
+ if (atomic_read(&device->reada_in_flight) <
+ MAX_IN_FLIGHT)
+ enqueued += reada_start_machine_dev(fs_info,
+ device);
+ }
+ total += enqueued;
+ } while (enqueued && total < 10000);
+
+ if (enqueued == 0)
+ return;
+
+ /*
+ * If everything is already in the cache, this is effectively single
+ * threaded. To a) not hold the caller for too long and b) to utilize
+ * more cores, we broke the loop above after 10000 iterations and now
+ * enqueue to workers to finish it. This will distribute the load to
+ * the cores.
+ * FIXME we might need our own workqueue here, with an idle threshold
+ * of one. Also these worker are relatively long-running.
+ */
+ for (i = 0; i < 2; ++i) {
+ struct reada_machine_work *rmw;
+
+ rmw = kzalloc(sizeof(*rmw), GFP_NOFS);
+ if (!rmw) {
+ /*
+ * no memory to kick it off to worker, so just do the
+ * rest of the work from here
+ */
+ goto again;
+ }
+ rmw->work.func = reada_start_machine_worker;
+ rmw->fs_info = fs_info;
+ btrfs_queue_worker(&fs_info->endio_meta_workers, &rmw->work);
+ }
+}
+
+static void dump_devs(struct btrfs_fs_info *fs_info, int all)
+{
+ struct btrfs_device *device;
+ struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+ unsigned long index;
+ int ret;
+ int i;
+ int j;
+ int cnt;
+
+ spin_lock(&fs_info->reada_lock);
+ list_for_each_entry(device, &fs_devices->devices, dev_list) {
+ printk(KERN_DEBUG "dev %lld has %d in flight\n", device->devid,
+ atomic_read(&device->reada_in_flight));
+ index = 0;
+ while (1) {
+ struct reada_zone *zone;
+ ret = radix_tree_gang_lookup(&device->reada_zones,
+ (void **)&zone, index, 1);
+ if (ret == 0)
+ break;
+ printk(KERN_DEBUG " zone %llu-%llu elems %llu locked "
+ "%d devs", zone->start, zone->end, zone->elems,
+ zone->locked);
+ for (j = 0; j < zone->ndevs; ++j) {
+ printk(KERN_DEBUG " %lld",
+ zone->devs[j]->devid);
+ }
+ if (device->reada_curr_zone == zone)
+ printk(KERN_DEBUG " curr off %llu",
+ device->reada_next - zone->start);
+ printk(KERN_DEBUG "\n");
+ index = (zone->end >> PAGE_CACHE_SHIFT) + 1;
+ }
+ cnt = 0;
+ index = 0;
+ while (all) {
+ struct reada_extent *re = NULL;
+
+ ret = radix_tree_gang_lookup(&device->reada_extents,
+ (void **)&re, index, 1);
+ if (ret == 0)
+ break;
+ printk(KERN_DEBUG
+ " re: logical %llu size %u empty %d for %lld",
+ re->logical, re->blocksize,
+ list_empty(&re->extctl), re->scheduled_for ?
+ re->scheduled_for->devid : -1);
+
+ for (i = 0; i < re->nzones; ++i) {
+ printk(KERN_DEBUG " zone %llu-%llu devs",
+ re->zones[i]->start,
+ re->zones[i]->end);
+ for (j = 0; j < re->zones[i]->ndevs; ++j) {
+ printk(KERN_DEBUG " %lld",
+ re->zones[i]->devs[j]->devid);
+ }
+ }
+ printk(KERN_DEBUG "\n");
+ index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
+ if (++cnt > 15)
+ break;
+ }
+ }
+
+ index = 0;
+ cnt = 0;
+ while (all) {
+ struct reada_extent *re = NULL;
+
+ ret = radix_tree_gang_lookup(&fs_info->reada_tree, (void **)&re,
+ index, 1);
+ if (ret == 0)
+ break;
+ printk(KERN_DEBUG
+ "re: logical %llu size %u list empty %d for %lld",
+ re->logical, re->blocksize, list_empty(&re->extctl),
+ re->scheduled_for ? re->scheduled_for->devid : -1);
+ for (i = 0; i < re->nzones; ++i) {
+ printk(KERN_DEBUG " zone %llu-%llu devs",
+ re->zones[i]->start,
+ re->zones[i]->end);
+ for (i = 0; i < re->nzones; ++i) {
+ printk(KERN_DEBUG " zone %llu-%llu devs",
+ re->zones[i]->start,
+ re->zones[i]->end);
+ for (j = 0; j < re->zones[i]->ndevs; ++j) {
+ printk(KERN_DEBUG " %lld",
+ re->zones[i]->devs[j]->devid);
+ }
+ }
+ }
+ printk(KERN_DEBUG "\n");
+ index = (re->logical >> PAGE_CACHE_SHIFT) + 1;
+ if (!all && ++cnt > 25)
+ break;
+ }
+ spin_unlock(&fs_info->reada_lock);
+}
+
+/*
+ * interface
+ */
+void *btrfs_reada_add(struct btrfs_root *root, struct btrfs_key *key_start,
+ struct btrfs_key *key_end)
+{
+ struct reada_control *rc;
+ u64 start;
+ u64 generation;
+ int level;
+
+ rc = kzalloc(sizeof(*rc), GFP_NOFS);
+ if (!rc)
+ return ERR_PTR(-ENOMEM);
+
+ rc->root = root;
+ rc->key_start = *key_start;
+ rc->key_end = *key_end;
+ spin_lock_init(&rc->lock);
+ rc->elems = 0;
+ rc->read_total = 0;
+ init_waitqueue_head(&rc->wait);
+ kref_init(&rc->refcnt);
+ kref_get(&rc->refcnt); /* one ref for having elements */
+
+ spin_lock(&root->node_lock);
+ start = root->node->start;
+ level = btrfs_header_level(root->node);
+ generation = btrfs_header_generation(root->node);
+ spin_unlock(&root->node_lock);
+
+ reada_add_block(rc, start, level, generation);
+
+ reada_start_machine(root->fs_info);
+
+ return rc;
+}
+
+int btrfs_reada_wait(void *handle)
+{
+ struct reada_control *rc = handle;
+
+ spin_lock(&rc->lock);
+ while (rc->elems) {
+ spin_unlock(&rc->lock);
+ wait_event(rc->wait, rc->elems == 0);
+ spin_lock(&rc->lock);
+ }
+ spin_unlock(&rc->lock);
+
+ reada_control_put(rc);
+
+ return 0;
+}
+
+int btrfs_reada_wait_debug(void *handle)
+{
+ struct reada_control *rc = handle;
+
+ spin_lock(&rc->lock);
+ while (rc->elems) {
+ spin_unlock(&rc->lock);
+ wait_event_timeout(rc->wait, rc->elems == 0, 2 * HZ);
+ spin_lock(&rc->lock);
+ printk(KERN_DEBUG "timeout: elems=%lld\n", rc->elems);
+ dump_devs(rc->root->fs_info, rc->elems < 10 ? 1 : 0);
+ }
+ spin_unlock(&rc->lock);
+
+ dump_devs(rc->root->fs_info, rc->elems < 10 ? 1 : 0);
+
+ reada_control_put(rc);
+
+ return 0;
+}
+
+void btrfs_reada_detach(void *handle)
+{
+ struct reada_control *rc = handle;
+
+ reada_control_put(rc);
+}
--
1.7.3.4
^ permalink raw reply related [flat|nested] 11+ messages in thread* [PATCH v1 5/5] btrfs: test ioctl for readahead
2011-05-23 12:59 [PATCH v1 0/5] btrfs: generic readeahead interface Arne Jansen
` (3 preceding siblings ...)
2011-05-23 12:59 ` [PATCH v1 4/5] btrfs: hooks for readahead Arne Jansen
@ 2011-05-23 12:59 ` Arne Jansen
4 siblings, 0 replies; 11+ messages in thread
From: Arne Jansen @ 2011-05-23 12:59 UTC (permalink / raw)
To: chris.mason, linux-btrfs
This ioctl is added to trigger a readahead from user mode. It implements
a readahead using the new interface and also a traditional tree walk.
This way it's possible to measure the two side by side.
Signed-off-by: Arne Jansen <sensille@gmx.net>
---
fs/btrfs/ioctl.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
fs/btrfs/ioctl.h | 16 ++++++++++
2 files changed, 101 insertions(+), 1 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f580a3a..13a88d7 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2465,6 +2465,89 @@ static noinline long btrfs_ioctl_wait_sync(struct file *file, void __user *argp)
return btrfs_wait_for_commit(root, transid);
}
+static noinline long btrfs_ioctl_reada_test(struct btrfs_fs_info *fs_info,
+ void __user *argp)
+{
+ struct btrfs_key start = {0, 0, 0};
+ struct btrfs_key end = {(u64)-1ll, (u8)-1, (u64)-1ll};
+ struct btrfs_ioctl_reada_args reada_args;
+ struct btrfs_key key;
+ struct btrfs_root *root = NULL;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ if (!argp)
+ return -EINVAL;
+
+ if (copy_from_user(&reada_args,
+ (struct btrfs_ioctl_reada_args __user *)argp,
+ sizeof(reada_args)))
+ return -EFAULT;
+
+ start.objectid = reada_args.start_objectid;
+ start.type = reada_args.start_type;
+ start.offset = reada_args.start_offset;
+ end.objectid = reada_args.end_objectid;
+ end.type = reada_args.end_type;
+ end.offset = reada_args.end_offset;
+
+ key.objectid = reada_args.tree;
+ key.type = BTRFS_ROOT_ITEM_KEY;
+ key.offset = (u64)-1;
+ root = btrfs_read_fs_root_no_name(fs_info, &key);
+ if (IS_ERR(root))
+ return -ENOENT;
+
+ if (!(reada_args.flags & BTRFS_READA_IOC_FLAGS_TRAD)) {
+ void *handle;
+
+ handle = btrfs_reada_add(root, &start, &end);
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);
+
+ if (reada_args.flags & BTRFS_READA_IOC_FLAGS_WAIT)
+ btrfs_reada_wait(handle);
+ else
+ btrfs_reada_detach(handle);
+ } else {
+ struct btrfs_path *path;
+ struct extent_buffer *leaf;
+ int slot;
+ int ret;
+
+ /*
+ * enumerate the tree the traditional way
+ */
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+ path->reada = 2;
+
+ ret = btrfs_search_slot(NULL, root, &start, path, 0, 0);
+ if (ret < 0)
+ goto out;
+
+ do {
+ leaf = path->nodes[0];
+ slot = path->slots[0];
+ btrfs_item_key_to_cpu(leaf, &key, slot);
+
+ if (key.objectid > end.objectid)
+ break;
+ if (key.objectid == end.objectid && key.type > end.type)
+ break;
+ if (key.objectid == end.objectid &&
+ key.type == end.type && key.offset > end.offset)
+ break;
+ } while ((ret = btrfs_next_leaf(root, path)) == 0);
+out:
+ btrfs_free_path(path);
+ return ret >= 0 ? 0 : ret;
+ }
+ return 0;
+}
+
long btrfs_ioctl(struct file *file, unsigned int
cmd, unsigned long arg)
{
@@ -2527,7 +2610,8 @@ long btrfs_ioctl(struct file *file, unsigned int
return btrfs_ioctl_start_sync(file, argp);
case BTRFS_IOC_WAIT_SYNC:
return btrfs_ioctl_wait_sync(file, argp);
+ case BTRFS_IOC_READA_TEST:
+ return btrfs_ioctl_reada_test(root->fs_info, argp);
}
-
return -ENOTTY;
}
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 8fb3821..9c744ce 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -157,6 +157,20 @@ struct btrfs_ioctl_space_args {
struct btrfs_ioctl_space_info spaces[0];
};
+#define BTRFS_READA_IOC_FLAGS_WAIT 1
+#define BTRFS_READA_IOC_FLAGS_TRAD 2
+struct btrfs_ioctl_reada_args {
+ __u64 flags;
+ __u64 tree;
+ __u64 start_objectid;
+ __u8 start_type;
+ __u64 start_offset;
+ __u64 end_objectid;
+ __u8 end_type;
+ __u64 end_offset;
+ __u64 unused[100];
+};
+
#define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \
struct btrfs_ioctl_vol_args)
#define BTRFS_IOC_DEFRAG _IOW(BTRFS_IOCTL_MAGIC, 2, \
@@ -203,4 +217,6 @@ struct btrfs_ioctl_space_args {
struct btrfs_ioctl_vol_args_v2)
#define BTRFS_IOC_SUBVOL_GETFLAGS _IOW(BTRFS_IOCTL_MAGIC, 25, __u64)
#define BTRFS_IOC_SUBVOL_SETFLAGS _IOW(BTRFS_IOCTL_MAGIC, 26, __u64)
+#define BTRFS_IOC_READA_TEST _IOW(BTRFS_IOCTL_MAGIC, 99, \
+ struct btrfs_ioctl_reada_args)
#endif
--
1.7.3.4
^ permalink raw reply related [flat|nested] 11+ messages in thread