* [PATCH 1/9] writeback: move dirty inodes from super_block to backing_dev_info
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
@ 2009-07-30 21:23 ` Jens Axboe
2009-08-06 21:35 ` Christoph Hellwig
2009-07-30 21:23 ` [PATCH 2/9] writeback: switch to per-bdi threads for flushing data Jens Axboe
` (8 subsequent siblings)
9 siblings, 1 reply; 30+ messages in thread
From: Jens Axboe @ 2009-07-30 21:23 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: chris.mason, david, hch, akpm, jack, yanmin_zhang, richard,
damien.wyart, fweisbec, Alan.Brunelle, Jens Axboe
This is a first step at introducing per-bdi flusher threads. We should
have no change in behaviour, although sb_has_dirty_inodes() is now
ridiculously expensive, as there's no easy way to answer that question.
Not a huge problem, since it'll be deleted in subsequent patches.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
fs/fs-writeback.c | 194 +++++++++++++++++++++++++++---------------
fs/super.c | 3 -
include/linux/backing-dev.h | 9 ++
include/linux/fs.h | 5 +-
mm/backing-dev.c | 24 ++++++
mm/page-writeback.c | 11 +--
6 files changed, 163 insertions(+), 83 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index c54226b..021f442 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -25,6 +25,7 @@
#include <linux/buffer_head.h>
#include "internal.h"
+#define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
/**
* writeback_acquire - attempt to get exclusive writeback access to a device
@@ -165,12 +166,13 @@ void __mark_inode_dirty(struct inode *inode, int flags)
goto out;
/*
- * If the inode was already on s_dirty/s_io/s_more_io, don't
- * reposition it (that would break s_dirty time-ordering).
+ * If the inode was already on b_dirty/b_io/b_more_io, don't
+ * reposition it (that would break b_dirty time-ordering).
*/
if (!was_dirty) {
inode->dirtied_when = jiffies;
- list_move(&inode->i_list, &sb->s_dirty);
+ list_move(&inode->i_list,
+ &inode_to_bdi(inode)->b_dirty);
}
}
out:
@@ -191,31 +193,30 @@ static int write_inode(struct inode *inode, int sync)
* furthest end of its superblock's dirty-inode list.
*
* Before stamping the inode's ->dirtied_when, we check to see whether it is
- * already the most-recently-dirtied inode on the s_dirty list. If that is
+ * already the most-recently-dirtied inode on the b_dirty list. If that is
* the case then the inode must have been redirtied while it was being written
* out and we don't reset its dirtied_when.
*/
static void redirty_tail(struct inode *inode)
{
- struct super_block *sb = inode->i_sb;
+ struct backing_dev_info *bdi = inode_to_bdi(inode);
- if (!list_empty(&sb->s_dirty)) {
- struct inode *tail_inode;
+ if (!list_empty(&bdi->b_dirty)) {
+ struct inode *tail;
- tail_inode = list_entry(sb->s_dirty.next, struct inode, i_list);
- if (time_before(inode->dirtied_when,
- tail_inode->dirtied_when))
+ tail = list_entry(bdi->b_dirty.next, struct inode, i_list);
+ if (time_before(inode->dirtied_when, tail->dirtied_when))
inode->dirtied_when = jiffies;
}
- list_move(&inode->i_list, &sb->s_dirty);
+ list_move(&inode->i_list, &bdi->b_dirty);
}
/*
- * requeue inode for re-scanning after sb->s_io list is exhausted.
+ * requeue inode for re-scanning after bdi->b_io list is exhausted.
*/
static void requeue_io(struct inode *inode)
{
- list_move(&inode->i_list, &inode->i_sb->s_more_io);
+ list_move(&inode->i_list, &inode_to_bdi(inode)->b_more_io);
}
static void inode_sync_complete(struct inode *inode)
@@ -262,18 +263,50 @@ static void move_expired_inodes(struct list_head *delaying_queue,
/*
* Queue all expired dirty inodes for io, eldest first.
*/
-static void queue_io(struct super_block *sb,
- unsigned long *older_than_this)
+static void queue_io(struct backing_dev_info *bdi,
+ unsigned long *older_than_this)
+{
+ list_splice_init(&bdi->b_more_io, bdi->b_io.prev);
+ move_expired_inodes(&bdi->b_dirty, &bdi->b_io, older_than_this);
+}
+
+static int sb_on_inode_list(struct super_block *sb, struct list_head *list)
{
- list_splice_init(&sb->s_more_io, sb->s_io.prev);
- move_expired_inodes(&sb->s_dirty, &sb->s_io, older_than_this);
+ struct inode *inode;
+ int ret = 0;
+
+ spin_lock(&inode_lock);
+ list_for_each_entry(inode, list, i_list) {
+ if (inode->i_sb == sb) {
+ ret = 1;
+ break;
+ }
+ }
+ spin_unlock(&inode_lock);
+ return ret;
}
int sb_has_dirty_inodes(struct super_block *sb)
{
- return !list_empty(&sb->s_dirty) ||
- !list_empty(&sb->s_io) ||
- !list_empty(&sb->s_more_io);
+ struct backing_dev_info *bdi;
+ int ret = 0;
+
+ /*
+ * This is REALLY expensive right now, but it'll go away
+ * when the bdi writeback is introduced
+ */
+ mutex_lock(&bdi_lock);
+ list_for_each_entry(bdi, &bdi_list, bdi_list) {
+ if (sb_on_inode_list(sb, &bdi->b_dirty) ||
+ sb_on_inode_list(sb, &bdi->b_io) ||
+ sb_on_inode_list(sb, &bdi->b_more_io)) {
+ ret = 1;
+ break;
+ }
+ }
+ mutex_unlock(&bdi_lock);
+
+ return ret;
}
EXPORT_SYMBOL(sb_has_dirty_inodes);
@@ -322,11 +355,11 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
if (inode->i_state & I_SYNC) {
/*
* If this inode is locked for writeback and we are not doing
- * writeback-for-data-integrity, move it to s_more_io so that
+ * writeback-for-data-integrity, move it to b_more_io so that
* writeback can proceed with the other inodes on s_io.
*
* We'll have another go at writing back this inode when we
- * completed a full scan of s_io.
+ * completed a full scan of b_io.
*/
if (!wait) {
requeue_io(inode);
@@ -371,11 +404,11 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
/*
* We didn't write back all the pages. nfs_writepages()
* sometimes bales out without doing anything. Redirty
- * the inode; Move it from s_io onto s_more_io/s_dirty.
+ * the inode; Move it from b_io onto b_more_io/b_dirty.
*/
/*
* akpm: if the caller was the kupdate function we put
- * this inode at the head of s_dirty so it gets first
+ * this inode at the head of b_dirty so it gets first
* consideration. Otherwise, move it to the tail, for
* the reasons described there. I'm not really sure
* how much sense this makes. Presumably I had a good
@@ -385,7 +418,7 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
if (wbc->for_kupdate) {
/*
* For the kupdate function we move the inode
- * to s_more_io so it will get more writeout as
+ * to b_more_io so it will get more writeout as
* soon as the queue becomes uncongested.
*/
inode->i_state |= I_DIRTY_PAGES;
@@ -433,51 +466,34 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
return ret;
}
-/*
- * Write out a superblock's list of dirty inodes. A wait will be performed
- * upon no inodes, all inodes or the final one, depending upon sync_mode.
- *
- * If older_than_this is non-NULL, then only write out inodes which
- * had their first dirtying at a time earlier than *older_than_this.
- *
- * If we're a pdflush thread, then implement pdflush collision avoidance
- * against the entire list.
- *
- * If `bdi' is non-zero then we're being asked to writeback a specific queue.
- * This function assumes that the blockdev superblock's inodes are backed by
- * a variety of queues, so all inodes are searched. For other superblocks,
- * assume that all inodes are backed by the same queue.
- *
- * FIXME: this linear search could get expensive with many fileystems. But
- * how to fix? We need to go from an address_space to all inodes which share
- * a queue with that address_space. (Easy: have a global "dirty superblocks"
- * list).
- *
- * The inodes to be written are parked on sb->s_io. They are moved back onto
- * sb->s_dirty as they are selected for writing. This way, none can be missed
- * on the writer throttling path, and we get decent balancing between many
- * throttled threads: we don't want them all piling up on inode_sync_wait.
- */
-void generic_sync_sb_inodes(struct super_block *sb,
- struct writeback_control *wbc)
+static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
+ struct writeback_control *wbc,
+ struct super_block *sb,
+ int is_blkdev_sb)
{
const unsigned long start = jiffies; /* livelock avoidance */
- int sync = wbc->sync_mode == WB_SYNC_ALL;
spin_lock(&inode_lock);
- if (!wbc->for_kupdate || list_empty(&sb->s_io))
- queue_io(sb, wbc->older_than_this);
- while (!list_empty(&sb->s_io)) {
- struct inode *inode = list_entry(sb->s_io.prev,
+ if (!wbc->for_kupdate || list_empty(&bdi->b_io))
+ queue_io(bdi, wbc->older_than_this);
+
+ while (!list_empty(&bdi->b_io)) {
+ struct inode *inode = list_entry(bdi->b_io.prev,
struct inode, i_list);
- struct address_space *mapping = inode->i_mapping;
- struct backing_dev_info *bdi = mapping->backing_dev_info;
long pages_skipped;
+ /*
+ * super block given and doesn't match, skip this inode
+ */
+ if (sb && sb != inode->i_sb) {
+ redirty_tail(inode);
+ continue;
+ }
+
if (!bdi_cap_writeback_dirty(bdi)) {
redirty_tail(inode);
- if (sb_is_blkdev_sb(sb)) {
+ if (is_blkdev_sb) {
/*
* Dirty memory-backed blockdev: the ramdisk
* driver does this. Skip just this inode
@@ -499,14 +515,14 @@ void generic_sync_sb_inodes(struct super_block *sb,
if (wbc->nonblocking && bdi_write_congested(bdi)) {
wbc->encountered_congestion = 1;
- if (!sb_is_blkdev_sb(sb))
+ if (!is_blkdev_sb)
break; /* Skip a congested fs */
requeue_io(inode);
continue; /* Skip a congested blockdev */
}
if (wbc->bdi && bdi != wbc->bdi) {
- if (!sb_is_blkdev_sb(sb))
+ if (!is_blkdev_sb)
break; /* fs has the wrong queue */
requeue_io(inode);
continue; /* blockdev has wrong queue */
@@ -544,13 +560,55 @@ void generic_sync_sb_inodes(struct super_block *sb,
wbc->more_io = 1;
break;
}
- if (!list_empty(&sb->s_more_io))
+ if (!list_empty(&bdi->b_more_io))
wbc->more_io = 1;
}
- if (sync) {
+ spin_unlock(&inode_lock);
+ /* Leave any unwritten inodes on b_io */
+}
+
+/*
+ * Write out a superblock's list of dirty inodes. A wait will be performed
+ * upon no inodes, all inodes or the final one, depending upon sync_mode.
+ *
+ * If older_than_this is non-NULL, then only write out inodes which
+ * had their first dirtying at a time earlier than *older_than_this.
+ *
+ * If we're a pdlfush thread, then implement pdflush collision avoidance
+ * against the entire list.
+ *
+ * If `bdi' is non-zero then we're being asked to writeback a specific queue.
+ * This function assumes that the blockdev superblock's inodes are backed by
+ * a variety of queues, so all inodes are searched. For other superblocks,
+ * assume that all inodes are backed by the same queue.
+ *
+ * FIXME: this linear search could get expensive with many fileystems. But
+ * how to fix? We need to go from an address_space to all inodes which share
+ * a queue with that address_space. (Easy: have a global "dirty superblocks"
+ * list).
+ *
+ * The inodes to be written are parked on bdi->b_io. They are moved back onto
+ * bdi->b_dirty as they are selected for writing. This way, none can be missed
+ * on the writer throttling path, and we get decent balancing between many
+ * throttled threads: we don't want them all piling up on inode_sync_wait.
+ */
+void generic_sync_sb_inodes(struct super_block *sb,
+ struct writeback_control *wbc)
+{
+ const int is_blkdev_sb = sb_is_blkdev_sb(sb);
+ struct backing_dev_info *bdi;
+
+ mutex_lock(&bdi_lock);
+ list_for_each_entry(bdi, &bdi_list, bdi_list)
+ generic_sync_bdi_inodes(bdi, wbc, sb, is_blkdev_sb);
+ mutex_unlock(&bdi_lock);
+
+ if (wbc->sync_mode == WB_SYNC_ALL) {
struct inode *inode, *old_inode = NULL;
+ spin_lock(&inode_lock);
+
/*
* Data integrity sync. Must wait for all pages under writeback,
* because there may have been pages dirtied before our sync
@@ -588,10 +646,8 @@ void generic_sync_sb_inodes(struct super_block *sb,
}
spin_unlock(&inode_lock);
iput(old_inode);
- } else
- spin_unlock(&inode_lock);
+ }
- return; /* Leave any unwritten inodes on s_io */
}
EXPORT_SYMBOL_GPL(generic_sync_sb_inodes);
@@ -606,8 +662,8 @@ static void sync_sb_inodes(struct super_block *sb,
*
* Note:
* We don't need to grab a reference to superblock here. If it has non-empty
- * ->s_dirty it's hadn't been killed yet and kill_super() won't proceed
- * past sync_inodes_sb() until the ->s_dirty/s_io/s_more_io lists are all
+ * ->b_dirty it's hadn't been killed yet and kill_super() won't proceed
+ * past sync_inodes_sb() until the ->b_dirty/b_io/b_more_io lists are all
* empty. Since __sync_single_inode() regains inode_lock before it finally moves
* inode from superblock lists we are OK.
*
diff --git a/fs/super.c b/fs/super.c
index 2761d3e..0d22ce3 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -62,9 +62,6 @@ static struct super_block *alloc_super(struct file_system_type *type)
s = NULL;
goto out;
}
- INIT_LIST_HEAD(&s->s_dirty);
- INIT_LIST_HEAD(&s->s_io);
- INIT_LIST_HEAD(&s->s_more_io);
INIT_LIST_HEAD(&s->s_files);
INIT_LIST_HEAD(&s->s_instances);
INIT_HLIST_HEAD(&s->s_anon);
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 1d52425..928cd54 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -40,6 +40,8 @@ enum bdi_stat_item {
#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
struct backing_dev_info {
+ struct list_head bdi_list;
+
unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
unsigned long state; /* Always use atomic bitops on this */
unsigned int capabilities; /* Device capabilities */
@@ -58,6 +60,10 @@ struct backing_dev_info {
struct device *dev;
+ struct list_head b_dirty; /* dirty inodes */
+ struct list_head b_io; /* parked for writeback */
+ struct list_head b_more_io; /* parked for more writeback */
+
#ifdef CONFIG_DEBUG_FS
struct dentry *debug_dir;
struct dentry *debug_stats;
@@ -72,6 +78,9 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
void bdi_unregister(struct backing_dev_info *bdi);
+extern struct mutex bdi_lock;
+extern struct list_head bdi_list;
+
static inline void __add_bdi_stat(struct backing_dev_info *bdi,
enum bdi_stat_item item, s64 amount)
{
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a36ffa5..1aea79b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -715,7 +715,7 @@ struct posix_acl;
struct inode {
struct hlist_node i_hash;
- struct list_head i_list;
+ struct list_head i_list; /* backing dev IO list */
struct list_head i_sb_list;
struct list_head i_dentry;
unsigned long i_ino;
@@ -1336,9 +1336,6 @@ struct super_block {
struct xattr_handler **s_xattr;
struct list_head s_inodes; /* all inodes */
- struct list_head s_dirty; /* dirty inodes */
- struct list_head s_io; /* parked for writeback */
- struct list_head s_more_io; /* parked for more writeback */
struct hlist_head s_anon; /* anonymous dentries for (nfs) exporting */
struct list_head s_files;
/* s_dentry_lru and s_nr_dentry_unused are protected by dcache_lock */
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index c86edd2..6f163e0 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -22,6 +22,8 @@ struct backing_dev_info default_backing_dev_info = {
EXPORT_SYMBOL_GPL(default_backing_dev_info);
static struct class *bdi_class;
+DEFINE_MUTEX(bdi_lock);
+LIST_HEAD(bdi_list);
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
@@ -211,6 +213,10 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
goto exit;
}
+ mutex_lock(&bdi_lock);
+ list_add_tail(&bdi->bdi_list, &bdi_list);
+ mutex_unlock(&bdi_lock);
+
bdi->dev = dev;
bdi_debug_register(bdi, dev_name(dev));
@@ -225,9 +231,17 @@ int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
}
EXPORT_SYMBOL(bdi_register_dev);
+static void bdi_remove_from_list(struct backing_dev_info *bdi)
+{
+ mutex_lock(&bdi_lock);
+ list_del(&bdi->bdi_list);
+ mutex_unlock(&bdi_lock);
+}
+
void bdi_unregister(struct backing_dev_info *bdi)
{
if (bdi->dev) {
+ bdi_remove_from_list(bdi);
bdi_debug_unregister(bdi);
device_unregister(bdi->dev);
bdi->dev = NULL;
@@ -245,6 +259,10 @@ int bdi_init(struct backing_dev_info *bdi)
bdi->min_ratio = 0;
bdi->max_ratio = 100;
bdi->max_prop_frac = PROP_FRAC_BASE;
+ INIT_LIST_HEAD(&bdi->bdi_list);
+ INIT_LIST_HEAD(&bdi->b_io);
+ INIT_LIST_HEAD(&bdi->b_dirty);
+ INIT_LIST_HEAD(&bdi->b_more_io);
for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
err = percpu_counter_init(&bdi->bdi_stat[i], 0);
@@ -259,6 +277,8 @@ int bdi_init(struct backing_dev_info *bdi)
err:
while (i--)
percpu_counter_destroy(&bdi->bdi_stat[i]);
+
+ bdi_remove_from_list(bdi);
}
return err;
@@ -269,6 +289,10 @@ void bdi_destroy(struct backing_dev_info *bdi)
{
int i;
+ WARN_ON(!list_empty(&bdi->b_dirty));
+ WARN_ON(!list_empty(&bdi->b_io));
+ WARN_ON(!list_empty(&bdi->b_more_io));
+
bdi_unregister(bdi);
for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 81627eb..f8341b6 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -320,15 +320,13 @@ static void task_dirty_limit(struct task_struct *tsk, unsigned long *pdirty)
/*
*
*/
-static DEFINE_SPINLOCK(bdi_lock);
static unsigned int bdi_min_ratio;
int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
{
int ret = 0;
- unsigned long flags;
- spin_lock_irqsave(&bdi_lock, flags);
+ mutex_lock(&bdi_lock);
if (min_ratio > bdi->max_ratio) {
ret = -EINVAL;
} else {
@@ -340,27 +338,26 @@ int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
ret = -EINVAL;
}
}
- spin_unlock_irqrestore(&bdi_lock, flags);
+ mutex_unlock(&bdi_lock);
return ret;
}
int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
{
- unsigned long flags;
int ret = 0;
if (max_ratio > 100)
return -EINVAL;
- spin_lock_irqsave(&bdi_lock, flags);
+ mutex_lock(&bdi_lock);
if (bdi->min_ratio > max_ratio) {
ret = -EINVAL;
} else {
bdi->max_ratio = max_ratio;
bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
}
- spin_unlock_irqrestore(&bdi_lock, flags);
+ mutex_unlock(&bdi_lock);
return ret;
}
--
1.6.3.2.306.g4f4fa
^ permalink raw reply related [flat|nested] 30+ messages in thread* Re: [PATCH 1/9] writeback: move dirty inodes from super_block to backing_dev_info
2009-07-30 21:23 ` [PATCH 1/9] writeback: move dirty inodes from super_block to backing_dev_info Jens Axboe
@ 2009-08-06 21:35 ` Christoph Hellwig
2009-08-12 16:12 ` Jens Axboe
0 siblings, 1 reply; 30+ messages in thread
From: Christoph Hellwig @ 2009-08-06 21:35 UTC (permalink / raw)
To: Jens Axboe
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm, jack,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Thu, Jul 30, 2009 at 11:23:56PM +0200, Jens Axboe wrote:
> This is a first step at introducing per-bdi flusher threads. We should
> have no change in behaviour, although sb_has_dirty_inodes() is now
> ridiculously expensive, as there's no easy way to answer that question.
> Not a huge problem, since it'll be deleted in subsequent patches.
Looking at this again and again I don't really like this at all. What
is the problem with having per-bdi flushing threads that just iterate
a list of superblocks per-bdi and then the inodes from there? That
would keep a lot of the calling conventions much more logical, as we
have to writeback data per-sb for all data integrity and some other
writes.
^ permalink raw reply [flat|nested] 30+ messages in thread
* Re: [PATCH 1/9] writeback: move dirty inodes from super_block to backing_dev_info
2009-08-06 21:35 ` Christoph Hellwig
@ 2009-08-12 16:12 ` Jens Axboe
2009-08-12 16:18 ` Jens Axboe
2009-08-28 20:29 ` Christoph Hellwig
0 siblings, 2 replies; 30+ messages in thread
From: Jens Axboe @ 2009-08-12 16:12 UTC (permalink / raw)
To: Christoph Hellwig
Cc: linux-kernel, linux-fsdevel, chris.mason, david, akpm, jack,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Thu, Aug 06 2009, Christoph Hellwig wrote:
> On Thu, Jul 30, 2009 at 11:23:56PM +0200, Jens Axboe wrote:
> > This is a first step at introducing per-bdi flusher threads. We should
> > have no change in behaviour, although sb_has_dirty_inodes() is now
> > ridiculously expensive, as there's no easy way to answer that question.
> > Not a huge problem, since it'll be deleted in subsequent patches.
>
> Looking at this again and again I don't really like this at all. What
> is the problem with having per-bdi flushing threads that just iterate
> a list of superblocks per-bdi and then the inodes from there? That
> would keep a lot of the calling conventions much more logical, as we
> have to writeback data per-sb for all data integrity and some other
> writes.
OK, so you'd prefer leaving the super block lists in place and rather
have the super blocks hanging off the bdi? What about file systems that
support more than one block device per mount, like btrfs? Can we assume
that they will forever provide a single bdi backing? btrfs currently has
this, just wondering about future implications.
--
Jens Axboe
^ permalink raw reply [flat|nested] 30+ messages in thread
* Re: [PATCH 1/9] writeback: move dirty inodes from super_block to backing_dev_info
2009-08-12 16:12 ` Jens Axboe
@ 2009-08-12 16:18 ` Jens Axboe
2009-08-28 20:29 ` Christoph Hellwig
1 sibling, 0 replies; 30+ messages in thread
From: Jens Axboe @ 2009-08-12 16:18 UTC (permalink / raw)
To: Christoph Hellwig
Cc: linux-kernel, linux-fsdevel, chris.mason, david, akpm, jack,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Wed, Aug 12 2009, Jens Axboe wrote:
> On Thu, Aug 06 2009, Christoph Hellwig wrote:
> > On Thu, Jul 30, 2009 at 11:23:56PM +0200, Jens Axboe wrote:
> > > This is a first step at introducing per-bdi flusher threads. We should
> > > have no change in behaviour, although sb_has_dirty_inodes() is now
> > > ridiculously expensive, as there's no easy way to answer that question.
> > > Not a huge problem, since it'll be deleted in subsequent patches.
> >
> > Looking at this again and again I don't really like this at all. What
> > is the problem with having per-bdi flushing threads that just iterate
> > a list of superblocks per-bdi and then the inodes from there? That
> > would keep a lot of the calling conventions much more logical, as we
> > have to writeback data per-sb for all data integrity and some other
> > writes.
>
> OK, so you'd prefer leaving the super block lists in place and rather
> have the super blocks hanging off the bdi? What about file systems that
> support more than one block device per mount, like btrfs? Can we assume
> that they will forever provide a single bdi backing? btrfs currently has
> this, just wondering about future implications.
Another issue with that approach is that you then need some logic to
decide which lists to do first, how much, etc. A single list is nicely
time ordered and retains our current approach, at least on a per-sb per
device level.
--
Jens Axboe
^ permalink raw reply [flat|nested] 30+ messages in thread
* Re: [PATCH 1/9] writeback: move dirty inodes from super_block to backing_dev_info
2009-08-12 16:12 ` Jens Axboe
2009-08-12 16:18 ` Jens Axboe
@ 2009-08-28 20:29 ` Christoph Hellwig
1 sibling, 0 replies; 30+ messages in thread
From: Christoph Hellwig @ 2009-08-28 20:29 UTC (permalink / raw)
To: Jens Axboe
Cc: Christoph Hellwig, linux-kernel, linux-fsdevel, chris.mason,
david, akpm, jack, yanmin_zhang, richard, damien.wyart, fweisbec,
Alan.Brunelle
On Wed, Aug 12, 2009 at 06:12:50PM +0200, Jens Axboe wrote:
> OK, so you'd prefer leaving the super block lists in place and rather
> have the super blocks hanging off the bdi?
That would solve the above problem. It would also implicitly provide
increased locality by always writing batches of dirty inodes per fs.
> What about file systems that
> support more than one block device per mount, like btrfs?
Or XFS :)
> Can we assume
> that they will forever provide a single bdi backing? btrfs currently has
> this, just wondering about future implications.
I don't see any point to assume things are forever. For making progress
on this and getting it merged in .32 making that assumption is a good
one IMHO.
Now the question about that to do with a filesystem on multiple actual
backing device is an interesting one. What about the case of having
btrfs just one half of two disks each? Or same with a "normal" fs
ontop of LVM/MD? Maybe in the end one thread(-pool) per filesystem
and not just per backing dev is the way forward, with the threads
schedule so that they don't interfer if they operate on the same
backing dev?
>
> --
> Jens Axboe
>
---end quoted text---
^ permalink raw reply [flat|nested] 30+ messages in thread
* [PATCH 2/9] writeback: switch to per-bdi threads for flushing data
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
2009-07-30 21:23 ` [PATCH 1/9] writeback: move dirty inodes from super_block to backing_dev_info Jens Axboe
@ 2009-07-30 21:23 ` Jens Axboe
2009-08-05 16:35 ` Jan Kara
2009-07-30 21:23 ` [PATCH 3/9] writeback: get rid of pdflush completely Jens Axboe
` (7 subsequent siblings)
9 siblings, 1 reply; 30+ messages in thread
From: Jens Axboe @ 2009-07-30 21:23 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: chris.mason, david, hch, akpm, jack, yanmin_zhang, richard,
damien.wyart, fweisbec, Alan.Brunelle, Jens Axboe
This gets rid of pdflush for bdi writeout and kupdated style cleaning.
This is an experiment to see if we get better writeout behaviour with
per-bdi flushing. Some initial tests look pretty encouraging. A sample
ffsb workload that does random writes to files is about 8% faster here
on a simple SATA drive during the benchmark phase. File layout also seems
a LOT more smooth in vmstat:
r b swpd free buff cache si so bi bo in cs us sy id wa
0 1 0 608848 2652 375372 0 0 0 71024 604 24 1 10 48 42
0 1 0 549644 2712 433736 0 0 0 60692 505 27 1 8 48 44
1 0 0 476928 2784 505192 0 0 4 29540 553 24 0 9 53 37
0 1 0 457972 2808 524008 0 0 0 54876 331 16 0 4 38 58
0 1 0 366128 2928 614284 0 0 4 92168 710 58 0 13 53 34
0 1 0 295092 3000 684140 0 0 0 62924 572 23 0 9 53 37
0 1 0 236592 3064 741704 0 0 4 58256 523 17 0 8 48 44
0 1 0 165608 3132 811464 0 0 0 57460 560 21 0 8 54 38
0 1 0 102952 3200 873164 0 0 4 74748 540 29 1 10 48 41
0 1 0 48604 3252 926472 0 0 0 53248 469 29 0 7 47 45
where vanilla tends to fluctuate a lot in the creation phase:
r b swpd free buff cache si so bi bo in cs us sy id wa
1 1 0 678716 5792 303380 0 0 0 74064 565 50 1 11 52 36
1 0 0 662488 5864 319396 0 0 4 352 302 329 0 2 47 51
0 1 0 599312 5924 381468 0 0 0 78164 516 55 0 9 51 40
0 1 0 519952 6008 459516 0 0 4 78156 622 56 1 11 52 37
1 1 0 436640 6092 541632 0 0 0 82244 622 54 0 11 48 41
0 1 0 436640 6092 541660 0 0 0 8 152 39 0 0 51 49
0 1 0 332224 6200 644252 0 0 4 102800 728 46 1 13 49 36
1 0 0 274492 6260 701056 0 0 4 12328 459 49 0 7 50 43
0 1 0 211220 6324 763356 0 0 0 106940 515 37 1 10 51 39
1 0 0 160412 6376 813468 0 0 0 8224 415 43 0 6 49 45
1 1 0 85980 6452 886556 0 0 4 113516 575 39 1 11 54 34
0 2 0 85968 6452 886620 0 0 0 1640 158 211 0 0 46 54
So apart from seemingly behaving better for buffered writeout, this also
allows us to potentially have more than one bdi thread flushing out data.
This may be useful for NUMA type setups.
A 10 disk test with btrfs performs 26% faster with per-bdi flushing. Other
tests pending. mmap heavy writing also improves considerably.
A separate thread is added to sync the super blocks. In the long term,
adding sync_supers_bdi() functionality could get rid of this thread again.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
fs/buffer.c | 2 +-
fs/fs-writeback.c | 293 +++++++++++++++++++++++++------------------
include/linux/backing-dev.h | 28 ++++-
include/linux/fs.h | 3 +-
include/linux/writeback.h | 2 +-
mm/backing-dev.c | 260 ++++++++++++++++++++++++++++++++++++--
mm/page-writeback.c | 154 +++-------------------
mm/vmscan.c | 2 +-
8 files changed, 472 insertions(+), 272 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index a3ef091..2a01b2b 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -281,7 +281,7 @@ static void free_more_memory(void)
struct zone *zone;
int nid;
- wakeup_pdflush(1024);
+ wakeup_flusher_threads(1024);
yield();
for_each_online_node(nid) {
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 021f442..f3e4105 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -19,6 +19,8 @@
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/mm.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
#include <linux/writeback.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
@@ -61,10 +63,170 @@ int writeback_in_progress(struct backing_dev_info *bdi)
*/
static void writeback_release(struct backing_dev_info *bdi)
{
- BUG_ON(!writeback_in_progress(bdi));
+ WARN_ON_ONCE(!writeback_in_progress(bdi));
+ bdi->wb_arg.nr_pages = 0;
+ bdi->wb_arg.sb = NULL;
clear_bit(BDI_pdflush, &bdi->state);
}
+void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
+ long nr_pages, enum writeback_sync_modes sync_mode)
+{
+ /*
+ * This only happens the first time someone kicks this bdi, so put
+ * it out-of-line.
+ */
+ if (unlikely(!bdi->task))
+ wake_up_process(default_backing_dev_info.task);
+
+ if (writeback_acquire(bdi)) {
+ bdi->wb_arg.nr_pages = nr_pages;
+ bdi->wb_arg.sb = sb;
+ bdi->wb_arg.sync_mode = sync_mode;
+
+ if (bdi->task)
+ wake_up_process(bdi->task);
+ }
+}
+
+/*
+ * The maximum number of pages to writeout in a single bdi flush/kupdate
+ * operation. We do this so we don't hold I_SYNC against an inode for
+ * enormous amounts of time, which would block a userspace task which has
+ * been forced to throttle against that inode. Also, the code reevaluates
+ * the dirty each time it has written this many pages.
+ */
+#define MAX_WRITEBACK_PAGES 1024
+
+static inline bool over_bground_thresh(void)
+{
+ unsigned long background_thresh, dirty_thresh;
+
+ get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
+
+ return (global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
+}
+
+/*
+ * Explicit flushing or periodic writeback of "old" data.
+ *
+ * Define "old": the first time one of an inode's pages is dirtied, we mark the
+ * dirtying-time in the inode's address_space. So this periodic writeback code
+ * just walks the superblock inode list, writing back any inodes which are
+ * older than a specific point in time.
+ *
+ * Try to run once per dirty_writeback_interval. But if a writeback event
+ * takes longer than a dirty_writeback_interval interval, then leave a
+ * one-second gap.
+ *
+ * older_than_this takes precedence over nr_to_write. So we'll only write back
+ * all dirty pages if they are all attached to "old" mappings.
+ */
+static void bdi_flush(struct backing_dev_info *bdi, int for_kupdate)
+{
+ struct writeback_control wbc = {
+ .bdi = bdi,
+ .sync_mode = bdi->wb_arg.sync_mode,
+ .older_than_this = NULL,
+ .for_kupdate = for_kupdate,
+ .range_cyclic = 1,
+ };
+ unsigned long oldest_jif;
+ long nr_pages = bdi->wb_arg.nr_pages;
+
+ if (wbc.for_kupdate) {
+ wbc.older_than_this = &oldest_jif;
+ oldest_jif = jiffies -
+ msecs_to_jiffies(dirty_expire_interval * 10);
+ }
+
+ for (;;) {
+ if (wbc.sync_mode == WB_SYNC_NONE && nr_pages <= 0 &&
+ !over_bground_thresh())
+ break;
+
+ wbc.more_io = 0;
+ wbc.encountered_congestion = 0;
+ wbc.nr_to_write = MAX_WRITEBACK_PAGES;
+ wbc.pages_skipped = 0;
+ generic_sync_bdi_inodes(bdi->wb_arg.sb, &wbc);
+ nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
+ /*
+ * If we ran out of stuff to write, bail unless more_io got set
+ */
+ if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
+ if (wbc.more_io && !wbc.for_kupdate)
+ continue;
+ break;
+ }
+ }
+}
+
+/*
+ * Handle writeback of dirty data for the device backed by this bdi. Also
+ * wakes up periodically and does kupdated style flushing.
+ */
+int bdi_writeback_task(struct backing_dev_info *bdi)
+{
+ while (!kthread_should_stop()) {
+ unsigned long wait_jiffies;
+ int for_kupdate;
+
+ wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(wait_jiffies);
+ try_to_freeze();
+
+ /*
+ * We get here in two cases:
+ *
+ * schedule_timeout() returned because the dirty writeback
+ * interval has elapsed. If that happens, we will be able
+ * to acquire the writeback lock and will proceed to do
+ * kupdated style writeout.
+ *
+ * Someone called bdi_start_writeback(), which will acquire
+ * the writeback lock. This means our writeback_acquire()
+ * below will fail and we call into bdi_pdflush() for
+ * pdflush style writeout.
+ *
+ */
+ for_kupdate = writeback_acquire(bdi);
+ if (for_kupdate) {
+ long nr;
+
+ nr = global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS) +
+ (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+
+ bdi->wb_arg.nr_pages = nr;
+ bdi->wb_arg.sb = NULL;
+ bdi->wb_arg.sync_mode = WB_SYNC_NONE;
+ }
+
+ bdi_flush(bdi, for_kupdate);
+ writeback_release(bdi);
+ }
+
+ return 0;
+}
+
+void bdi_writeback_all(struct super_block *sb, struct writeback_control *wbc)
+{
+ struct backing_dev_info *bdi;
+
+ spin_lock(&bdi_lock);
+
+ list_for_each_entry(bdi, &bdi_list, bdi_list) {
+ if (!bdi_has_dirty_io(bdi))
+ continue;
+ bdi_start_writeback(bdi, sb, wbc->nr_to_write, wbc->sync_mode);
+ }
+
+ spin_unlock(&bdi_lock);
+}
+
static noinline void block_dump___mark_inode_dirty(struct inode *inode)
{
if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
@@ -270,46 +432,6 @@ static void queue_io(struct backing_dev_info *bdi,
move_expired_inodes(&bdi->b_dirty, &bdi->b_io, older_than_this);
}
-static int sb_on_inode_list(struct super_block *sb, struct list_head *list)
-{
- struct inode *inode;
- int ret = 0;
-
- spin_lock(&inode_lock);
- list_for_each_entry(inode, list, i_list) {
- if (inode->i_sb == sb) {
- ret = 1;
- break;
- }
- }
- spin_unlock(&inode_lock);
- return ret;
-}
-
-int sb_has_dirty_inodes(struct super_block *sb)
-{
- struct backing_dev_info *bdi;
- int ret = 0;
-
- /*
- * This is REALLY expensive right now, but it'll go away
- * when the bdi writeback is introduced
- */
- mutex_lock(&bdi_lock);
- list_for_each_entry(bdi, &bdi_list, bdi_list) {
- if (sb_on_inode_list(sb, &bdi->b_dirty) ||
- sb_on_inode_list(sb, &bdi->b_io) ||
- sb_on_inode_list(sb, &bdi->b_more_io)) {
- ret = 1;
- break;
- }
- }
- mutex_unlock(&bdi_lock);
-
- return ret;
-}
-EXPORT_SYMBOL(sb_has_dirty_inodes);
-
/*
* Wait for writeback on an inode to complete.
*/
@@ -466,11 +588,11 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
return ret;
}
-static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
- struct writeback_control *wbc,
- struct super_block *sb,
- int is_blkdev_sb)
+void generic_sync_bdi_inodes(struct super_block *sb,
+ struct writeback_control *wbc)
{
+ const int is_blkdev_sb = sb_is_blkdev_sb(sb);
+ struct backing_dev_info *bdi = wbc->bdi;
const unsigned long start = jiffies; /* livelock avoidance */
spin_lock(&inode_lock);
@@ -521,13 +643,6 @@ static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
continue; /* Skip a congested blockdev */
}
- if (wbc->bdi && bdi != wbc->bdi) {
- if (!is_blkdev_sb)
- break; /* fs has the wrong queue */
- requeue_io(inode);
- continue; /* blockdev has wrong queue */
- }
-
/*
* Was this inode dirtied after sync_sb_inodes was called?
* This keeps sync from extra jobs and livelock.
@@ -535,16 +650,10 @@ static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
if (inode_dirtied_after(inode, start))
break;
- /* Is another pdflush already flushing this queue? */
- if (current_is_pdflush() && !writeback_acquire(bdi))
- break;
-
BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
__iget(inode);
pages_skipped = wbc->pages_skipped;
writeback_single_inode(inode, wbc);
- if (current_is_pdflush())
- writeback_release(bdi);
if (wbc->pages_skipped != pages_skipped) {
/*
* writeback is not making progress due to locked
@@ -583,11 +692,6 @@ static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
* a variety of queues, so all inodes are searched. For other superblocks,
* assume that all inodes are backed by the same queue.
*
- * FIXME: this linear search could get expensive with many fileystems. But
- * how to fix? We need to go from an address_space to all inodes which share
- * a queue with that address_space. (Easy: have a global "dirty superblocks"
- * list).
- *
* The inodes to be written are parked on bdi->b_io. They are moved back onto
* bdi->b_dirty as they are selected for writing. This way, none can be missed
* on the writer throttling path, and we get decent balancing between many
@@ -596,13 +700,10 @@ static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
void generic_sync_sb_inodes(struct super_block *sb,
struct writeback_control *wbc)
{
- const int is_blkdev_sb = sb_is_blkdev_sb(sb);
- struct backing_dev_info *bdi;
-
- mutex_lock(&bdi_lock);
- list_for_each_entry(bdi, &bdi_list, bdi_list)
- generic_sync_bdi_inodes(bdi, wbc, sb, is_blkdev_sb);
- mutex_unlock(&bdi_lock);
+ if (wbc->bdi)
+ generic_sync_bdi_inodes(sb, wbc);
+ else
+ bdi_writeback_all(sb, wbc);
if (wbc->sync_mode == WB_SYNC_ALL) {
struct inode *inode, *old_inode = NULL;
@@ -658,58 +759,6 @@ static void sync_sb_inodes(struct super_block *sb,
}
/*
- * Start writeback of dirty pagecache data against all unlocked inodes.
- *
- * Note:
- * We don't need to grab a reference to superblock here. If it has non-empty
- * ->b_dirty it's hadn't been killed yet and kill_super() won't proceed
- * past sync_inodes_sb() until the ->b_dirty/b_io/b_more_io lists are all
- * empty. Since __sync_single_inode() regains inode_lock before it finally moves
- * inode from superblock lists we are OK.
- *
- * If `older_than_this' is non-zero then only flush inodes which have a
- * flushtime older than *older_than_this.
- *
- * If `bdi' is non-zero then we will scan the first inode against each
- * superblock until we find the matching ones. One group will be the dirty
- * inodes against a filesystem. Then when we hit the dummy blockdev superblock,
- * sync_sb_inodes will seekout the blockdev which matches `bdi'. Maybe not
- * super-efficient but we're about to do a ton of I/O...
- */
-void
-writeback_inodes(struct writeback_control *wbc)
-{
- struct super_block *sb;
-
- might_sleep();
- spin_lock(&sb_lock);
-restart:
- list_for_each_entry_reverse(sb, &super_blocks, s_list) {
- if (sb_has_dirty_inodes(sb)) {
- /* we're making our own get_super here */
- sb->s_count++;
- spin_unlock(&sb_lock);
- /*
- * If we can't get the readlock, there's no sense in
- * waiting around, most of the time the FS is going to
- * be unmounted by the time it is released.
- */
- if (down_read_trylock(&sb->s_umount)) {
- if (sb->s_root)
- sync_sb_inodes(sb, wbc);
- up_read(&sb->s_umount);
- }
- spin_lock(&sb_lock);
- if (__put_super_and_need_restart(sb))
- goto restart;
- }
- if (wbc->nr_to_write <= 0)
- break;
- }
- spin_unlock(&sb_lock);
-}
-
-/*
* writeback and wait upon the filesystem's dirty inodes. The caller will
* do this in two passes - one to write, and one to wait.
*
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 928cd54..8860264 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -13,6 +13,7 @@
#include <linux/proportions.h>
#include <linux/kernel.h>
#include <linux/fs.h>
+#include <linux/writeback.h>
#include <asm/atomic.h>
struct page;
@@ -24,6 +25,7 @@ struct dentry;
*/
enum bdi_state {
BDI_pdflush, /* A pdflush thread is working this device */
+ BDI_pending, /* On its way to being activated */
BDI_async_congested, /* The async (write) queue is getting full */
BDI_sync_congested, /* The sync queue is getting full */
BDI_unused, /* Available bits start here */
@@ -39,6 +41,12 @@ enum bdi_stat_item {
#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
+struct bdi_writeback_arg {
+ unsigned long nr_pages;
+ struct super_block *sb;
+ enum writeback_sync_modes sync_mode;
+};
+
struct backing_dev_info {
struct list_head bdi_list;
@@ -60,6 +68,8 @@ struct backing_dev_info {
struct device *dev;
+ struct task_struct *task; /* writeback task */
+ struct bdi_writeback_arg wb_arg; /* protected by BDI_pdflush */
struct list_head b_dirty; /* dirty inodes */
struct list_head b_io; /* parked for writeback */
struct list_head b_more_io; /* parked for more writeback */
@@ -77,10 +87,21 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
const char *fmt, ...);
int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
void bdi_unregister(struct backing_dev_info *bdi);
+void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
+ long nr_pages, enum writeback_sync_modes sync_mode);
+int bdi_writeback_task(struct backing_dev_info *bdi);
+void bdi_writeback_all(struct super_block *sb, struct writeback_control *wbc);
-extern struct mutex bdi_lock;
+extern spinlock_t bdi_lock;
extern struct list_head bdi_list;
+static inline int bdi_has_dirty_io(struct backing_dev_info *bdi)
+{
+ return !list_empty(&bdi->b_dirty) ||
+ !list_empty(&bdi->b_io) ||
+ !list_empty(&bdi->b_more_io);
+}
+
static inline void __add_bdi_stat(struct backing_dev_info *bdi,
enum bdi_stat_item item, s64 amount)
{
@@ -270,6 +291,11 @@ static inline bool bdi_cap_swap_backed(struct backing_dev_info *bdi)
return bdi->capabilities & BDI_CAP_SWAP_BACKED;
}
+static inline bool bdi_cap_flush_forker(struct backing_dev_info *bdi)
+{
+ return bdi == &default_backing_dev_info;
+}
+
static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
{
return bdi_cap_writeback_dirty(mapping->backing_dev_info);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1aea79b..b8d98e5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2069,6 +2069,8 @@ extern int invalidate_inode_pages2_range(struct address_space *mapping,
pgoff_t start, pgoff_t end);
extern void generic_sync_sb_inodes(struct super_block *sb,
struct writeback_control *wbc);
+extern void generic_sync_bdi_inodes(struct super_block *sb,
+ struct writeback_control *);
extern int write_inode_now(struct inode *, int);
extern int filemap_fdatawrite(struct address_space *);
extern int filemap_flush(struct address_space *);
@@ -2182,7 +2184,6 @@ extern int bdev_read_only(struct block_device *);
extern int set_blocksize(struct block_device *, int);
extern int sb_set_blocksize(struct super_block *, int);
extern int sb_min_blocksize(struct super_block *, int);
-extern int sb_has_dirty_inodes(struct super_block *);
extern int generic_file_mmap(struct file *, struct vm_area_struct *);
extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 3224820..6999882 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -98,7 +98,7 @@ static inline void inode_sync_wait(struct inode *inode)
/*
* mm/page-writeback.c
*/
-int wakeup_pdflush(long nr_pages);
+void wakeup_flusher_threads(long nr_pages);
void laptop_io_completion(void);
void laptop_sync_completion(void);
void throttle_vm_writeout(gfp_t gfp_mask);
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 6f163e0..b44f793 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -1,8 +1,11 @@
#include <linux/wait.h>
#include <linux/backing-dev.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
+#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/writeback.h>
@@ -22,8 +25,18 @@ struct backing_dev_info default_backing_dev_info = {
EXPORT_SYMBOL_GPL(default_backing_dev_info);
static struct class *bdi_class;
-DEFINE_MUTEX(bdi_lock);
+DEFINE_SPINLOCK(bdi_lock);
LIST_HEAD(bdi_list);
+LIST_HEAD(bdi_pending_list);
+
+static struct task_struct *sync_supers_tsk;
+static struct timer_list sync_supers_timer;
+
+static int bdi_sync_supers(void *);
+static void sync_supers_timer_fn(unsigned long);
+static void arm_supers_timer(void);
+
+static void bdi_add_default_flusher_task(struct backing_dev_info *bdi);
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
@@ -187,6 +200,13 @@ static int __init default_bdi_init(void)
{
int err;
+ sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
+ BUG_ON(IS_ERR(sync_supers_tsk));
+
+ init_timer(&sync_supers_timer);
+ setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
+ arm_supers_timer();
+
err = bdi_init(&default_backing_dev_info);
if (!err)
bdi_register(&default_backing_dev_info, NULL, "default");
@@ -195,6 +215,184 @@ static int __init default_bdi_init(void)
}
subsys_initcall(default_bdi_init);
+static int bdi_start_fn(void *ptr)
+{
+ struct backing_dev_info *bdi = ptr;
+ struct task_struct *tsk = current;
+
+ /*
+ * Add us to the active bdi_list
+ */
+ spin_lock(&bdi_lock);
+ list_add(&bdi->bdi_list, &bdi_list);
+ spin_unlock(&bdi_lock);
+
+ tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;
+ set_freezable();
+
+ /*
+ * Our parent may run at a different priority, just set us to normal
+ */
+ set_user_nice(tsk, 0);
+
+ /*
+ * Clear pending bit and wakeup anybody waiting to tear us down
+ */
+ clear_bit(BDI_pending, &bdi->state);
+ smp_mb__after_clear_bit();
+ wake_up_bit(&bdi->state, BDI_pending);
+
+ return bdi_writeback_task(bdi);
+}
+
+static void bdi_flush_io(struct backing_dev_info *bdi)
+{
+ struct writeback_control wbc = {
+ .bdi = bdi,
+ .sync_mode = WB_SYNC_NONE,
+ .older_than_this = NULL,
+ .range_cyclic = 1,
+ .nr_to_write = 1024,
+ };
+
+ generic_sync_bdi_inodes(NULL, &wbc);
+}
+
+/*
+ * kupdated() used to do this. We cannot do it from the bdi_forker_task()
+ * or we risk deadlocking on ->s_umount. The longer term solution would be
+ * to implement sync_supers_bdi() or similar and simply do it from the
+ * bdi writeback tasks individually.
+ */
+static int bdi_sync_supers(void *unused)
+{
+ set_user_nice(current, 0);
+
+ while (!kthread_should_stop()) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule();
+
+ /*
+ * Do this periodically, like kupdated() did before.
+ */
+ sync_supers();
+ }
+
+ return 0;
+}
+
+static void arm_supers_timer(void)
+{
+ unsigned long next;
+
+ next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
+ mod_timer(&sync_supers_timer, round_jiffies_up(next));
+}
+
+static void sync_supers_timer_fn(unsigned long unused)
+{
+ wake_up_process(sync_supers_tsk);
+ arm_supers_timer();
+}
+
+static int bdi_forker_task(void *ptr)
+{
+ struct backing_dev_info *me = ptr;
+
+ for (;;) {
+ struct backing_dev_info *bdi, *tmp;
+
+ /*
+ * Temporary measure, we want to make sure we don't see
+ * dirty data on the default backing_dev_info
+ */
+ if (bdi_has_dirty_io(me))
+ bdi_flush_io(me);
+
+ spin_lock(&bdi_lock);
+
+ /*
+ * Check if any existing bdi's have dirty data without
+ * a thread registered. If so, set that up.
+ */
+ list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
+ if (bdi->task || !bdi_has_dirty_io(bdi))
+ continue;
+
+ bdi_add_default_flusher_task(bdi);
+ }
+
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ if (list_empty(&bdi_pending_list)) {
+ unsigned long wait;
+
+ spin_unlock(&bdi_lock);
+ wait = msecs_to_jiffies(dirty_writeback_interval * 10);
+ schedule_timeout(wait);
+ try_to_freeze();
+ continue;
+ }
+
+ __set_current_state(TASK_RUNNING);
+
+ /*
+ * This is our real job - check for pending entries in
+ * bdi_pending_list, and create the tasks that got added
+ */
+ bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
+ bdi_list);
+ list_del_init(&bdi->bdi_list);
+ spin_unlock(&bdi_lock);
+
+ BUG_ON(bdi->task);
+
+ bdi->task = kthread_run(bdi_start_fn, bdi, "flush-%s",
+ dev_name(bdi->dev));
+ /*
+ * If task creation fails, then readd the bdi to
+ * the pending list and force writeout of the bdi
+ * from this forker thread. That will free some memory
+ * and we can try again.
+ */
+ if (IS_ERR(bdi->task)) {
+ bdi->task = NULL;
+
+ /*
+ * Add this 'bdi' to the back, so we get
+ * a chance to flush other bdi's to free
+ * memory.
+ */
+ spin_lock(&bdi_lock);
+ list_add_tail(&bdi->bdi_list, &bdi_pending_list);
+ spin_unlock(&bdi_lock);
+
+ bdi_flush_io(bdi);
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Add a new flusher task that gets created for any bdi
+ * that has dirty data pending writeout
+ */
+static void bdi_add_default_flusher_task(struct backing_dev_info *bdi)
+{
+ /*
+ * Someone already marked this pending for task creation
+ */
+ if (test_and_set_bit(BDI_pending, &bdi->state))
+ return;
+
+ spin_lock(&bdi_lock);
+ list_move_tail(&bdi->bdi_list, &bdi_pending_list);
+ spin_unlock(&bdi_lock);
+
+ wake_up_process(default_backing_dev_info.task);
+}
+
int bdi_register(struct backing_dev_info *bdi, struct device *parent,
const char *fmt, ...)
{
@@ -213,13 +411,31 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
goto exit;
}
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
list_add_tail(&bdi->bdi_list, &bdi_list);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
bdi->dev = dev;
- bdi_debug_register(bdi, dev_name(dev));
+ /*
+ * Just start the forker thread for our default backing_dev_info,
+ * and add other bdi's to the list. They will get a thread created
+ * on-demand when they need it.
+ */
+ if (bdi_cap_flush_forker(bdi)) {
+ bdi->task = kthread_run(bdi_forker_task, bdi, "bdi-%s",
+ dev_name(dev));
+ if (IS_ERR(bdi->task)) {
+ bdi->task = NULL;
+ spin_lock(&bdi_lock);
+ list_del(&bdi->bdi_list);
+ spin_unlock(&bdi_lock);
+ ret = -ENOMEM;
+ goto exit;
+ }
+ }
+
+ bdi_debug_register(bdi, dev_name(dev));
exit:
return ret;
}
@@ -231,17 +447,40 @@ int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
}
EXPORT_SYMBOL(bdi_register_dev);
-static void bdi_remove_from_list(struct backing_dev_info *bdi)
+static int sched_wait(void *word)
{
- mutex_lock(&bdi_lock);
+ schedule();
+ return 0;
+}
+
+/*
+ * Remove bdi from the global list
+ */
+static void bdi_wb_shutdown(struct backing_dev_info *bdi)
+{
+ /*
+ * If setup is pending, wait for that to complete first
+ */
+ wait_on_bit(&bdi->state, BDI_pending, sched_wait, TASK_UNINTERRUPTIBLE);
+
+ /*
+ * Make sure nobody finds us on the bdi_list anymore
+ */
+ spin_lock(&bdi_lock);
list_del(&bdi->bdi_list);
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
}
void bdi_unregister(struct backing_dev_info *bdi)
{
if (bdi->dev) {
- bdi_remove_from_list(bdi);
+ if (!bdi_cap_flush_forker(bdi)) {
+ bdi_wb_shutdown(bdi);
+ if (bdi->task) {
+ kthread_stop(bdi->task);
+ bdi->task = NULL;
+ }
+ }
bdi_debug_unregister(bdi);
device_unregister(bdi->dev);
bdi->dev = NULL;
@@ -251,8 +490,7 @@ EXPORT_SYMBOL(bdi_unregister);
int bdi_init(struct backing_dev_info *bdi)
{
- int i;
- int err;
+ int i, err;
bdi->dev = NULL;
@@ -277,8 +515,6 @@ int bdi_init(struct backing_dev_info *bdi)
err:
while (i--)
percpu_counter_destroy(&bdi->bdi_stat[i]);
-
- bdi_remove_from_list(bdi);
}
return err;
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index f8341b6..a727af9 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -36,15 +36,6 @@
#include <linux/pagevec.h>
/*
- * The maximum number of pages to writeout in a single bdflush/kupdate
- * operation. We do this so we don't hold I_SYNC against an inode for
- * enormous amounts of time, which would block a userspace task which has
- * been forced to throttle against that inode. Also, the code reevaluates
- * the dirty each time it has written this many pages.
- */
-#define MAX_WRITEBACK_PAGES 1024
-
-/*
* After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
* will look to see if it needs to force writeback or throttling.
*/
@@ -117,8 +108,6 @@ EXPORT_SYMBOL(laptop_mode);
/* End of sysctl-exported parameters */
-static void background_writeout(unsigned long _min_pages);
-
/*
* Scale the writeback cache size proportional to the relative writeout speeds.
*
@@ -326,7 +315,7 @@ int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
{
int ret = 0;
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
if (min_ratio > bdi->max_ratio) {
ret = -EINVAL;
} else {
@@ -338,7 +327,7 @@ int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
ret = -EINVAL;
}
}
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
return ret;
}
@@ -350,14 +339,14 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
if (max_ratio > 100)
return -EINVAL;
- mutex_lock(&bdi_lock);
+ spin_lock(&bdi_lock);
if (bdi->min_ratio > max_ratio) {
ret = -EINVAL;
} else {
bdi->max_ratio = max_ratio;
bdi->max_prop_frac = (PROP_FRAC_BASE * max_ratio) / 100;
}
- mutex_unlock(&bdi_lock);
+ spin_unlock(&bdi_lock);
return ret;
}
@@ -543,7 +532,7 @@ static void balance_dirty_pages(struct address_space *mapping)
* up.
*/
if (bdi_nr_reclaimable > bdi_thresh) {
- writeback_inodes(&wbc);
+ generic_sync_bdi_inodes(NULL, &wbc);
pages_written += write_chunk - wbc.nr_to_write;
get_dirty_limits(&background_thresh, &dirty_thresh,
&bdi_thresh, bdi);
@@ -594,7 +583,7 @@ static void balance_dirty_pages(struct address_space *mapping)
(!laptop_mode && (global_page_state(NR_FILE_DIRTY)
+ global_page_state(NR_UNSTABLE_NFS)
> background_thresh)))
- pdflush_operation(background_writeout, 0);
+ bdi_start_writeback(bdi, NULL, 0, WB_SYNC_NONE);
}
void set_page_dirty_balance(struct page *page, int page_mkwrite)
@@ -679,152 +668,53 @@ void throttle_vm_writeout(gfp_t gfp_mask)
}
/*
- * writeback at least _min_pages, and keep writing until the amount of dirty
- * memory is less than the background threshold, or until we're all clean.
+ * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
+ * the whole world.
*/
-static void background_writeout(unsigned long _min_pages)
+void wakeup_flusher_threads(long nr_pages)
{
- long min_pages = _min_pages;
struct writeback_control wbc = {
- .bdi = NULL,
.sync_mode = WB_SYNC_NONE,
.older_than_this = NULL,
- .nr_to_write = 0,
- .nonblocking = 1,
.range_cyclic = 1,
};
- for ( ; ; ) {
- unsigned long background_thresh;
- unsigned long dirty_thresh;
-
- get_dirty_limits(&background_thresh, &dirty_thresh, NULL, NULL);
- if (global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) < background_thresh
- && min_pages <= 0)
- break;
- wbc.more_io = 0;
- wbc.encountered_congestion = 0;
- wbc.nr_to_write = MAX_WRITEBACK_PAGES;
- wbc.pages_skipped = 0;
- writeback_inodes(&wbc);
- min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
- if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
- /* Wrote less than expected */
- if (wbc.encountered_congestion || wbc.more_io)
- congestion_wait(BLK_RW_ASYNC, HZ/10);
- else
- break;
- }
- }
-}
-
-/*
- * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
- * the whole world. Returns 0 if a pdflush thread was dispatched. Returns
- * -1 if all pdflush threads were busy.
- */
-int wakeup_pdflush(long nr_pages)
-{
if (nr_pages == 0)
nr_pages = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS);
- return pdflush_operation(background_writeout, nr_pages);
+ wbc.nr_to_write = nr_pages;
+ bdi_writeback_all(NULL, &wbc);
}
-static void wb_timer_fn(unsigned long unused);
static void laptop_timer_fn(unsigned long unused);
-static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0);
static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0);
/*
- * Periodic writeback of "old" data.
- *
- * Define "old": the first time one of an inode's pages is dirtied, we mark the
- * dirtying-time in the inode's address_space. So this periodic writeback code
- * just walks the superblock inode list, writing back any inodes which are
- * older than a specific point in time.
- *
- * Try to run once per dirty_writeback_interval. But if a writeback event
- * takes longer than a dirty_writeback_interval interval, then leave a
- * one-second gap.
- *
- * older_than_this takes precedence over nr_to_write. So we'll only write back
- * all dirty pages if they are all attached to "old" mappings.
- */
-static void wb_kupdate(unsigned long arg)
-{
- unsigned long oldest_jif;
- unsigned long start_jif;
- unsigned long next_jif;
- long nr_to_write;
- struct writeback_control wbc = {
- .bdi = NULL,
- .sync_mode = WB_SYNC_NONE,
- .older_than_this = &oldest_jif,
- .nr_to_write = 0,
- .nonblocking = 1,
- .for_kupdate = 1,
- .range_cyclic = 1,
- };
-
- sync_supers();
-
- oldest_jif = jiffies - msecs_to_jiffies(dirty_expire_interval * 10);
- start_jif = jiffies;
- next_jif = start_jif + msecs_to_jiffies(dirty_writeback_interval * 10);
- nr_to_write = global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) +
- (inodes_stat.nr_inodes - inodes_stat.nr_unused);
- while (nr_to_write > 0) {
- wbc.more_io = 0;
- wbc.encountered_congestion = 0;
- wbc.nr_to_write = MAX_WRITEBACK_PAGES;
- writeback_inodes(&wbc);
- if (wbc.nr_to_write > 0) {
- if (wbc.encountered_congestion || wbc.more_io)
- congestion_wait(BLK_RW_ASYNC, HZ/10);
- else
- break; /* All the old data is written */
- }
- nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
- }
- if (time_before(next_jif, jiffies + HZ))
- next_jif = jiffies + HZ;
- if (dirty_writeback_interval)
- mod_timer(&wb_timer, next_jif);
-}
-
-/*
* sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
*/
int dirty_writeback_centisecs_handler(ctl_table *table, int write,
struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
{
proc_dointvec(table, write, file, buffer, length, ppos);
- if (dirty_writeback_interval)
- mod_timer(&wb_timer, jiffies +
- msecs_to_jiffies(dirty_writeback_interval * 10));
- else
- del_timer(&wb_timer);
return 0;
}
-static void wb_timer_fn(unsigned long unused)
+static void do_laptop_sync(struct work_struct *work)
{
- if (pdflush_operation(wb_kupdate, 0) < 0)
- mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */
-}
-
-static void laptop_flush(unsigned long unused)
-{
- sys_sync();
+ wakeup_flusher_threads(0);
+ kfree(work);
}
static void laptop_timer_fn(unsigned long unused)
{
- pdflush_operation(laptop_flush, 0);
+ struct work_struct *work;
+
+ work = kmalloc(sizeof(*work), GFP_ATOMIC);
+ if (work) {
+ INIT_WORK(work, do_laptop_sync);
+ schedule_work(work);
+ }
}
/*
@@ -907,8 +797,6 @@ void __init page_writeback_init(void)
{
int shift;
- mod_timer(&wb_timer,
- jiffies + msecs_to_jiffies(dirty_writeback_interval * 10));
writeback_set_ratelimit();
register_cpu_notifier(&ratelimit_nb);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index dea7abd..fe8e986 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1715,7 +1715,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
*/
if (total_scanned > sc->swap_cluster_max +
sc->swap_cluster_max / 2) {
- wakeup_pdflush(laptop_mode ? 0 : total_scanned);
+ wakeup_flusher_threads(laptop_mode ? 0 : total_scanned);
sc->may_writepage = 1;
}
--
1.6.3.2.306.g4f4fa
^ permalink raw reply related [flat|nested] 30+ messages in thread* Re: [PATCH 2/9] writeback: switch to per-bdi threads for flushing data
2009-07-30 21:23 ` [PATCH 2/9] writeback: switch to per-bdi threads for flushing data Jens Axboe
@ 2009-08-05 16:35 ` Jan Kara
2009-08-06 21:44 ` Christoph Hellwig
0 siblings, 1 reply; 30+ messages in thread
From: Jan Kara @ 2009-08-05 16:35 UTC (permalink / raw)
To: Jens Axboe
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm, jack,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Thu 30-07-09 23:23:57, Jens Axboe wrote:
> This gets rid of pdflush for bdi writeout and kupdated style cleaning.
> This is an experiment to see if we get better writeout behaviour with
> per-bdi flushing. Some initial tests look pretty encouraging. A sample
> ffsb workload that does random writes to files is about 8% faster here
> on a simple SATA drive during the benchmark phase. File layout also seems
> a LOT more smooth in vmstat:
>
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 0 1 0 608848 2652 375372 0 0 0 71024 604 24 1 10 48 42
> 0 1 0 549644 2712 433736 0 0 0 60692 505 27 1 8 48 44
> 1 0 0 476928 2784 505192 0 0 4 29540 553 24 0 9 53 37
> 0 1 0 457972 2808 524008 0 0 0 54876 331 16 0 4 38 58
> 0 1 0 366128 2928 614284 0 0 4 92168 710 58 0 13 53 34
> 0 1 0 295092 3000 684140 0 0 0 62924 572 23 0 9 53 37
> 0 1 0 236592 3064 741704 0 0 4 58256 523 17 0 8 48 44
> 0 1 0 165608 3132 811464 0 0 0 57460 560 21 0 8 54 38
> 0 1 0 102952 3200 873164 0 0 4 74748 540 29 1 10 48 41
> 0 1 0 48604 3252 926472 0 0 0 53248 469 29 0 7 47 45
>
> where vanilla tends to fluctuate a lot in the creation phase:
>
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 1 1 0 678716 5792 303380 0 0 0 74064 565 50 1 11 52 36
> 1 0 0 662488 5864 319396 0 0 4 352 302 329 0 2 47 51
> 0 1 0 599312 5924 381468 0 0 0 78164 516 55 0 9 51 40
> 0 1 0 519952 6008 459516 0 0 4 78156 622 56 1 11 52 37
> 1 1 0 436640 6092 541632 0 0 0 82244 622 54 0 11 48 41
> 0 1 0 436640 6092 541660 0 0 0 8 152 39 0 0 51 49
> 0 1 0 332224 6200 644252 0 0 4 102800 728 46 1 13 49 36
> 1 0 0 274492 6260 701056 0 0 4 12328 459 49 0 7 50 43
> 0 1 0 211220 6324 763356 0 0 0 106940 515 37 1 10 51 39
> 1 0 0 160412 6376 813468 0 0 0 8224 415 43 0 6 49 45
> 1 1 0 85980 6452 886556 0 0 4 113516 575 39 1 11 54 34
> 0 2 0 85968 6452 886620 0 0 0 1640 158 211 0 0 46 54
>
> So apart from seemingly behaving better for buffered writeout, this also
> allows us to potentially have more than one bdi thread flushing out data.
> This may be useful for NUMA type setups.
>
> A 10 disk test with btrfs performs 26% faster with per-bdi flushing. Other
> tests pending. mmap heavy writing also improves considerably.
Any update here?
> A separate thread is added to sync the super blocks. In the long term,
> adding sync_supers_bdi() functionality could get rid of this thread again.
>
> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
> ---
<snip>
> @@ -466,11 +588,11 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
> return ret;
> }
>
> -static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
> - struct writeback_control *wbc,
> - struct super_block *sb,
> - int is_blkdev_sb)
> +void generic_sync_bdi_inodes(struct super_block *sb,
> + struct writeback_control *wbc)
> {
Jens, sorry about bitching about this again but you're silently changing
substantial locking assumptions without writing it *anywhere* and without
arguing it's safe.
Originally, generic_sync_sb_inodes() from writeback path have been
called with
a) s_umount_sem held
b) sb->s_count elevated
The second still seems to be true since, if I'm right, we pass here
non-NULL sb only from sync_filesystem() and that takes care of the
superblock reference. So that is just a matter of documenting this fact
before the function.
But s_umount_sem is not held anymore so you should say why this cannot
interact badly with the umount / remount code. Looking at the code, if the
filesystem dirties some inode (usually a system file) while e.g.
invalidate_inodes() is running, you can happily start writeback on it while
put_super() is running and that is not expected. In my opinion, you should
make sure you don't touch inode in a filesystem which is currently being
remounted / umounted. Actually, it should not be too hard to do - when you
look at an inode from b_io list, you can (while still holding inode_lock
and before acquiring inode reference) do:
down_read_trylock(&inode->i_sb->s_umount)
if it fails, you just leave the inode alone, otherwise you proceed and drop
the lock when you are done.
> + const int is_blkdev_sb = sb_is_blkdev_sb(sb);
> + struct backing_dev_info *bdi = wbc->bdi;
> const unsigned long start = jiffies; /* livelock avoidance */
>
> spin_lock(&inode_lock);
> @@ -521,13 +643,6 @@ static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
> continue; /* Skip a congested blockdev */
> }
>
> - if (wbc->bdi && bdi != wbc->bdi) {
> - if (!is_blkdev_sb)
> - break; /* fs has the wrong queue */
> - requeue_io(inode);
> - continue; /* blockdev has wrong queue */
> - }
> -
> /*
> * Was this inode dirtied after sync_sb_inodes was called?
> * This keeps sync from extra jobs and livelock.
> @@ -535,16 +650,10 @@ static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
> if (inode_dirtied_after(inode, start))
> break;
>
> - /* Is another pdflush already flushing this queue? */
> - if (current_is_pdflush() && !writeback_acquire(bdi))
> - break;
> -
> BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
> __iget(inode);
> pages_skipped = wbc->pages_skipped;
> writeback_single_inode(inode, wbc);
> - if (current_is_pdflush())
> - writeback_release(bdi);
> if (wbc->pages_skipped != pages_skipped) {
> /*
> * writeback is not making progress due to locked
> @@ -583,11 +692,6 @@ static void generic_sync_bdi_inodes(struct backing_dev_info *bdi,
> * a variety of queues, so all inodes are searched. For other superblocks,
> * assume that all inodes are backed by the same queue.
> *
> - * FIXME: this linear search could get expensive with many fileystems. But
> - * how to fix? We need to go from an address_space to all inodes which share
> - * a queue with that address_space. (Easy: have a global "dirty superblocks"
> - * list).
> - *
> * The inodes to be written are parked on bdi->b_io. They are moved back onto
> * bdi->b_dirty as they are selected for writing. This way, none can be missed
> * on the writer throttling path, and we get decent balancing between many
<snip>
> diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
> index 928cd54..8860264 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
<snip>
> @@ -77,10 +87,21 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
> const char *fmt, ...);
> int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
> void bdi_unregister(struct backing_dev_info *bdi);
> +void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
> + long nr_pages, enum writeback_sync_modes sync_mode);
> +int bdi_writeback_task(struct backing_dev_info *bdi);
> +void bdi_writeback_all(struct super_block *sb, struct writeback_control *wbc);
>
> -extern struct mutex bdi_lock;
> +extern spinlock_t bdi_lock;
It's slightly strange to make mutex from this spinlock in the first patch and
then return back to spinlock in the second one...
<snip>
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index 6f163e0..b44f793 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
<snip>
> +static int bdi_forker_task(void *ptr)
> +{
> + struct backing_dev_info *me = ptr;
> +
> + for (;;) {
> + struct backing_dev_info *bdi, *tmp;
> +
> + /*
> + * Temporary measure, we want to make sure we don't see
> + * dirty data on the default backing_dev_info
> + */
> + if (bdi_has_dirty_io(me))
> + bdi_flush_io(me);
> +
> + spin_lock(&bdi_lock);
> +
> + /*
> + * Check if any existing bdi's have dirty data without
> + * a thread registered. If so, set that up.
> + */
> + list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
> + if (bdi->task || !bdi_has_dirty_io(bdi))
> + continue;
> +
> + bdi_add_default_flusher_task(bdi);
> + }
> +
> + set_current_state(TASK_INTERRUPTIBLE);
> +
> + if (list_empty(&bdi_pending_list)) {
> + unsigned long wait;
> +
> + spin_unlock(&bdi_lock);
> + wait = msecs_to_jiffies(dirty_writeback_interval * 10);
> + schedule_timeout(wait);
> + try_to_freeze();
> + continue;
> + }
> +
> + __set_current_state(TASK_RUNNING);
> +
> + /*
> + * This is our real job - check for pending entries in
> + * bdi_pending_list, and create the tasks that got added
> + */
> + bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
> + bdi_list);
> + list_del_init(&bdi->bdi_list);
> + spin_unlock(&bdi_lock);
> +
> + BUG_ON(bdi->task);
> +
> + bdi->task = kthread_run(bdi_start_fn, bdi, "flush-%s",
> + dev_name(bdi->dev));
> + /*
> + * If task creation fails, then readd the bdi to
> + * the pending list and force writeout of the bdi
> + * from this forker thread. That will free some memory
> + * and we can try again.
> + */
> + if (IS_ERR(bdi->task)) {
> + bdi->task = NULL;
> +
> + /*
> + * Add this 'bdi' to the back, so we get
> + * a chance to flush other bdi's to free
> + * memory.
> + */
> + spin_lock(&bdi_lock);
> + list_add_tail(&bdi->bdi_list, &bdi_pending_list);
> + spin_unlock(&bdi_lock);
> +
> + bdi_flush_io(bdi);
> + }
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * Add a new flusher task that gets created for any bdi
> + * that has dirty data pending writeout
> + */
> +static void bdi_add_default_flusher_task(struct backing_dev_info *bdi)
> +{
This function seems to be called with bdi_lock already held so taking
bdi_lock in it does not look healthy ;) Also why not move it above the
bdi_forker_task() to save a forward declaration?
> + /*
> + * Someone already marked this pending for task creation
> + */
> + if (test_and_set_bit(BDI_pending, &bdi->state))
> + return;
> +
> + spin_lock(&bdi_lock);
> + list_move_tail(&bdi->bdi_list, &bdi_pending_list);
> + spin_unlock(&bdi_lock);
> +
> + wake_up_process(default_backing_dev_info.task);
> +}
> +
> int bdi_register(struct backing_dev_info *bdi, struct device *parent,
> const char *fmt, ...)
> {
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 30+ messages in thread* Re: [PATCH 2/9] writeback: switch to per-bdi threads for flushing data
2009-08-05 16:35 ` Jan Kara
@ 2009-08-06 21:44 ` Christoph Hellwig
0 siblings, 0 replies; 30+ messages in thread
From: Christoph Hellwig @ 2009-08-06 21:44 UTC (permalink / raw)
To: Jan Kara
Cc: Jens Axboe, linux-kernel, linux-fsdevel, chris.mason, david, hch,
akpm, yanmin_zhang, richard, damien.wyart, fweisbec,
Alan.Brunelle
On Wed, Aug 05, 2009 at 06:35:32PM +0200, Jan Kara wrote:
> Jens, sorry about bitching about this again but you're silently changing
> substantial locking assumptions without writing it *anywhere* and without
> arguing it's safe.
> Originally, generic_sync_sb_inodes() from writeback path have been
> called with
> a) s_umount_sem held
> b) sb->s_count elevated
> The second still seems to be true since, if I'm right, we pass here
> non-NULL sb only from sync_filesystem() and that takes care of the
> superblock reference. So that is just a matter of documenting this fact
> before the function.
We'll defintively need to keep both to prevent races vs unmount. And
with a NULL superblock passed I'm not even sure how we can take care of
it.
^ permalink raw reply [flat|nested] 30+ messages in thread
* [PATCH 3/9] writeback: get rid of pdflush completely
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
2009-07-30 21:23 ` [PATCH 1/9] writeback: move dirty inodes from super_block to backing_dev_info Jens Axboe
2009-07-30 21:23 ` [PATCH 2/9] writeback: switch to per-bdi threads for flushing data Jens Axboe
@ 2009-07-30 21:23 ` Jens Axboe
2009-07-30 21:23 ` [PATCH 4/9] writeback: separate the flushing state/task from the bdi Jens Axboe
` (6 subsequent siblings)
9 siblings, 0 replies; 30+ messages in thread
From: Jens Axboe @ 2009-07-30 21:23 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: chris.mason, david, hch, akpm, jack, yanmin_zhang, richard,
damien.wyart, fweisbec, Alan.Brunelle, Jens Axboe
It is now unused, so kill it off.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
fs/fs-writeback.c | 5 +
include/linux/writeback.h | 12 --
mm/Makefile | 2 +-
mm/pdflush.c | 269 ---------------------------------------------
4 files changed, 6 insertions(+), 282 deletions(-)
delete mode 100644 mm/pdflush.c
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f3e4105..7b49d90 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -29,6 +29,11 @@
#define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
+/*
+ * We don't actually have pdflush, but this one is exported though /proc...
+ */
+int nr_pdflush_threads;
+
/**
* writeback_acquire - attempt to get exclusive writeback access to a device
* @bdi: the device's backing_dev_info structure
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 6999882..6e416a9 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -14,17 +14,6 @@ extern struct list_head inode_in_use;
extern struct list_head inode_unused;
/*
- * Yes, writeback.h requires sched.h
- * No, sched.h is not included from here.
- */
-static inline int task_is_pdflush(struct task_struct *task)
-{
- return task->flags & PF_FLUSHER;
-}
-
-#define current_is_pdflush() task_is_pdflush(current)
-
-/*
* fs/fs-writeback.c
*/
enum writeback_sync_modes {
@@ -150,7 +139,6 @@ balance_dirty_pages_ratelimited(struct address_space *mapping)
typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
void *data);
-int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0);
int generic_writepages(struct address_space *mapping,
struct writeback_control *wbc);
int write_cache_pages(struct address_space *mapping,
diff --git a/mm/Makefile b/mm/Makefile
index 5e0bd64..147a7a7 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -8,7 +8,7 @@ mmu-$(CONFIG_MMU) := fremap.o highmem.o madvise.o memory.o mincore.o \
vmalloc.o
obj-y := bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
- maccess.o page_alloc.o page-writeback.o pdflush.o \
+ maccess.o page_alloc.o page-writeback.o \
readahead.o swap.o truncate.o vmscan.o shmem.o \
prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
page_isolation.o mm_init.o $(mmu-y)
diff --git a/mm/pdflush.c b/mm/pdflush.c
deleted file mode 100644
index 235ac44..0000000
--- a/mm/pdflush.c
+++ /dev/null
@@ -1,269 +0,0 @@
-/*
- * mm/pdflush.c - worker threads for writing back filesystem data
- *
- * Copyright (C) 2002, Linus Torvalds.
- *
- * 09Apr2002 Andrew Morton
- * Initial version
- * 29Feb2004 kaos@sgi.com
- * Move worker thread creation to kthread to avoid chewing
- * up stack space with nested calls to kernel_thread.
- */
-
-#include <linux/sched.h>
-#include <linux/list.h>
-#include <linux/signal.h>
-#include <linux/spinlock.h>
-#include <linux/gfp.h>
-#include <linux/init.h>
-#include <linux/module.h>
-#include <linux/fs.h> /* Needed by writeback.h */
-#include <linux/writeback.h> /* Prototypes pdflush_operation() */
-#include <linux/kthread.h>
-#include <linux/cpuset.h>
-#include <linux/freezer.h>
-
-
-/*
- * Minimum and maximum number of pdflush instances
- */
-#define MIN_PDFLUSH_THREADS 2
-#define MAX_PDFLUSH_THREADS 8
-
-static void start_one_pdflush_thread(void);
-
-
-/*
- * The pdflush threads are worker threads for writing back dirty data.
- * Ideally, we'd like one thread per active disk spindle. But the disk
- * topology is very hard to divine at this level. Instead, we take
- * care in various places to prevent more than one pdflush thread from
- * performing writeback against a single filesystem. pdflush threads
- * have the PF_FLUSHER flag set in current->flags to aid in this.
- */
-
-/*
- * All the pdflush threads. Protected by pdflush_lock
- */
-static LIST_HEAD(pdflush_list);
-static DEFINE_SPINLOCK(pdflush_lock);
-
-/*
- * The count of currently-running pdflush threads. Protected
- * by pdflush_lock.
- *
- * Readable by sysctl, but not writable. Published to userspace at
- * /proc/sys/vm/nr_pdflush_threads.
- */
-int nr_pdflush_threads = 0;
-
-/*
- * The time at which the pdflush thread pool last went empty
- */
-static unsigned long last_empty_jifs;
-
-/*
- * The pdflush thread.
- *
- * Thread pool management algorithm:
- *
- * - The minimum and maximum number of pdflush instances are bound
- * by MIN_PDFLUSH_THREADS and MAX_PDFLUSH_THREADS.
- *
- * - If there have been no idle pdflush instances for 1 second, create
- * a new one.
- *
- * - If the least-recently-went-to-sleep pdflush thread has been asleep
- * for more than one second, terminate a thread.
- */
-
-/*
- * A structure for passing work to a pdflush thread. Also for passing
- * state information between pdflush threads. Protected by pdflush_lock.
- */
-struct pdflush_work {
- struct task_struct *who; /* The thread */
- void (*fn)(unsigned long); /* A callback function */
- unsigned long arg0; /* An argument to the callback */
- struct list_head list; /* On pdflush_list, when idle */
- unsigned long when_i_went_to_sleep;
-};
-
-static int __pdflush(struct pdflush_work *my_work)
-{
- current->flags |= PF_FLUSHER | PF_SWAPWRITE;
- set_freezable();
- my_work->fn = NULL;
- my_work->who = current;
- INIT_LIST_HEAD(&my_work->list);
-
- spin_lock_irq(&pdflush_lock);
- for ( ; ; ) {
- struct pdflush_work *pdf;
-
- set_current_state(TASK_INTERRUPTIBLE);
- list_move(&my_work->list, &pdflush_list);
- my_work->when_i_went_to_sleep = jiffies;
- spin_unlock_irq(&pdflush_lock);
- schedule();
- try_to_freeze();
- spin_lock_irq(&pdflush_lock);
- if (!list_empty(&my_work->list)) {
- /*
- * Someone woke us up, but without removing our control
- * structure from the global list. swsusp will do this
- * in try_to_freeze()->refrigerator(). Handle it.
- */
- my_work->fn = NULL;
- continue;
- }
- if (my_work->fn == NULL) {
- printk("pdflush: bogus wakeup\n");
- continue;
- }
- spin_unlock_irq(&pdflush_lock);
-
- (*my_work->fn)(my_work->arg0);
-
- spin_lock_irq(&pdflush_lock);
-
- /*
- * Thread creation: For how long have there been zero
- * available threads?
- *
- * To throttle creation, we reset last_empty_jifs.
- */
- if (time_after(jiffies, last_empty_jifs + 1 * HZ)) {
- if (list_empty(&pdflush_list)) {
- if (nr_pdflush_threads < MAX_PDFLUSH_THREADS) {
- last_empty_jifs = jiffies;
- nr_pdflush_threads++;
- spin_unlock_irq(&pdflush_lock);
- start_one_pdflush_thread();
- spin_lock_irq(&pdflush_lock);
- }
- }
- }
-
- my_work->fn = NULL;
-
- /*
- * Thread destruction: For how long has the sleepiest
- * thread slept?
- */
- if (list_empty(&pdflush_list))
- continue;
- if (nr_pdflush_threads <= MIN_PDFLUSH_THREADS)
- continue;
- pdf = list_entry(pdflush_list.prev, struct pdflush_work, list);
- if (time_after(jiffies, pdf->when_i_went_to_sleep + 1 * HZ)) {
- /* Limit exit rate */
- pdf->when_i_went_to_sleep = jiffies;
- break; /* exeunt */
- }
- }
- nr_pdflush_threads--;
- spin_unlock_irq(&pdflush_lock);
- return 0;
-}
-
-/*
- * Of course, my_work wants to be just a local in __pdflush(). It is
- * separated out in this manner to hopefully prevent the compiler from
- * performing unfortunate optimisations against the auto variables. Because
- * these are visible to other tasks and CPUs. (No problem has actually
- * been observed. This is just paranoia).
- */
-static int pdflush(void *dummy)
-{
- struct pdflush_work my_work;
- cpumask_var_t cpus_allowed;
-
- /*
- * Since the caller doesn't even check kthread_run() worked, let's not
- * freak out too much if this fails.
- */
- if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
- printk(KERN_WARNING "pdflush failed to allocate cpumask\n");
- return 0;
- }
-
- /*
- * pdflush can spend a lot of time doing encryption via dm-crypt. We
- * don't want to do that at keventd's priority.
- */
- set_user_nice(current, 0);
-
- /*
- * Some configs put our parent kthread in a limited cpuset,
- * which kthread() overrides, forcing cpus_allowed == cpu_all_mask.
- * Our needs are more modest - cut back to our cpusets cpus_allowed.
- * This is needed as pdflush's are dynamically created and destroyed.
- * The boottime pdflush's are easily placed w/o these 2 lines.
- */
- cpuset_cpus_allowed(current, cpus_allowed);
- set_cpus_allowed_ptr(current, cpus_allowed);
- free_cpumask_var(cpus_allowed);
-
- return __pdflush(&my_work);
-}
-
-/*
- * Attempt to wake up a pdflush thread, and get it to do some work for you.
- * Returns zero if it indeed managed to find a worker thread, and passed your
- * payload to it.
- */
-int pdflush_operation(void (*fn)(unsigned long), unsigned long arg0)
-{
- unsigned long flags;
- int ret = 0;
-
- BUG_ON(fn == NULL); /* Hard to diagnose if it's deferred */
-
- spin_lock_irqsave(&pdflush_lock, flags);
- if (list_empty(&pdflush_list)) {
- ret = -1;
- } else {
- struct pdflush_work *pdf;
-
- pdf = list_entry(pdflush_list.next, struct pdflush_work, list);
- list_del_init(&pdf->list);
- if (list_empty(&pdflush_list))
- last_empty_jifs = jiffies;
- pdf->fn = fn;
- pdf->arg0 = arg0;
- wake_up_process(pdf->who);
- }
- spin_unlock_irqrestore(&pdflush_lock, flags);
-
- return ret;
-}
-
-static void start_one_pdflush_thread(void)
-{
- struct task_struct *k;
-
- k = kthread_run(pdflush, NULL, "pdflush");
- if (unlikely(IS_ERR(k))) {
- spin_lock_irq(&pdflush_lock);
- nr_pdflush_threads--;
- spin_unlock_irq(&pdflush_lock);
- }
-}
-
-static int __init pdflush_init(void)
-{
- int i;
-
- /*
- * Pre-set nr_pdflush_threads... If we fail to create,
- * the count will be decremented.
- */
- nr_pdflush_threads = MIN_PDFLUSH_THREADS;
-
- for (i = 0; i < MIN_PDFLUSH_THREADS; i++)
- start_one_pdflush_thread();
- return 0;
-}
-
-module_init(pdflush_init);
--
1.6.3.2.306.g4f4fa
^ permalink raw reply related [flat|nested] 30+ messages in thread* [PATCH 4/9] writeback: separate the flushing state/task from the bdi
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
` (2 preceding siblings ...)
2009-07-30 21:23 ` [PATCH 3/9] writeback: get rid of pdflush completely Jens Axboe
@ 2009-07-30 21:23 ` Jens Axboe
2009-07-30 21:24 ` [PATCH 5/9] writeback: support > 1 flusher thread per bdi Jens Axboe
` (5 subsequent siblings)
9 siblings, 0 replies; 30+ messages in thread
From: Jens Axboe @ 2009-07-30 21:23 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: chris.mason, david, hch, akpm, jack, yanmin_zhang, richard,
damien.wyart, fweisbec, Alan.Brunelle, Jens Axboe
Add a struct bdi_writeback for tracking and handling dirty IO. This
is in preparation for adding > 1 flusher task per bdi.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
fs/fs-writeback.c | 147 ++++++++++++++++++++++++++----------------
include/linux/backing-dev.h | 38 +++++++-----
mm/backing-dev.c | 120 ++++++++++++++++++++++++++---------
3 files changed, 204 insertions(+), 101 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 7b49d90..86fb2a9 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -29,6 +29,10 @@
#define inode_to_bdi(inode) ((inode)->i_mapping->backing_dev_info)
+static void generic_sync_wb_inodes(struct bdi_writeback *wb,
+ struct super_block *sb,
+ struct writeback_control *wbc);
+
/*
* We don't actually have pdflush, but this one is exported though /proc...
*/
@@ -46,9 +50,11 @@ int nr_pdflush_threads;
* unless they implement their own. Which is somewhat inefficient, as this
* may prevent concurrent writeback against multiple devices.
*/
-static int writeback_acquire(struct backing_dev_info *bdi)
+static int writeback_acquire(struct bdi_writeback *wb)
{
- return !test_and_set_bit(BDI_pdflush, &bdi->state);
+ struct backing_dev_info *bdi = wb->bdi;
+
+ return !test_and_set_bit(wb->nr, &bdi->wb_active);
}
/**
@@ -59,19 +65,37 @@ static int writeback_acquire(struct backing_dev_info *bdi)
*/
int writeback_in_progress(struct backing_dev_info *bdi)
{
- return test_bit(BDI_pdflush, &bdi->state);
+ return bdi->wb_active != 0;
}
/**
* writeback_release - relinquish exclusive writeback access against a device.
* @bdi: the device's backing_dev_info structure
*/
-static void writeback_release(struct backing_dev_info *bdi)
+static void writeback_release(struct bdi_writeback *wb)
+{
+ struct backing_dev_info *bdi = wb->bdi;
+
+ wb->nr_pages = 0;
+ wb->sb = NULL;
+ clear_bit(wb->nr, &bdi->wb_active);
+}
+
+static void wb_start_writeback(struct bdi_writeback *wb, struct super_block *sb,
+ long nr_pages,
+ enum writeback_sync_modes sync_mode)
{
- WARN_ON_ONCE(!writeback_in_progress(bdi));
- bdi->wb_arg.nr_pages = 0;
- bdi->wb_arg.sb = NULL;
- clear_bit(BDI_pdflush, &bdi->state);
+ if (!wb_has_dirty_io(wb))
+ return;
+
+ if (writeback_acquire(wb)) {
+ wb->nr_pages = nr_pages;
+ wb->sb = sb;
+ wb->sync_mode = sync_mode;
+
+ if (wb->task)
+ wake_up_process(wb->task);
+ }
}
void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
@@ -81,17 +105,10 @@ void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
* This only happens the first time someone kicks this bdi, so put
* it out-of-line.
*/
- if (unlikely(!bdi->task))
- wake_up_process(default_backing_dev_info.task);
+ if (unlikely(!bdi->wb.task))
+ wake_up_process(default_backing_dev_info.wb.task);
- if (writeback_acquire(bdi)) {
- bdi->wb_arg.nr_pages = nr_pages;
- bdi->wb_arg.sb = sb;
- bdi->wb_arg.sync_mode = sync_mode;
-
- if (bdi->task)
- wake_up_process(bdi->task);
- }
+ wb_start_writeback(&bdi->wb, sb, nr_pages, sync_mode);
}
/*
@@ -128,17 +145,17 @@ static inline bool over_bground_thresh(void)
* older_than_this takes precedence over nr_to_write. So we'll only write back
* all dirty pages if they are all attached to "old" mappings.
*/
-static void bdi_flush(struct backing_dev_info *bdi, int for_kupdate)
+static void wb_writeback(struct bdi_writeback *wb, int for_kupdate)
{
struct writeback_control wbc = {
- .bdi = bdi,
- .sync_mode = bdi->wb_arg.sync_mode,
+ .bdi = wb->bdi,
+ .sync_mode = wb->sync_mode,
.older_than_this = NULL,
.for_kupdate = for_kupdate,
.range_cyclic = 1,
};
unsigned long oldest_jif;
- long nr_pages = bdi->wb_arg.nr_pages;
+ long nr_pages = wb->nr_pages;
if (wbc.for_kupdate) {
wbc.older_than_this = &oldest_jif;
@@ -155,7 +172,7 @@ static void bdi_flush(struct backing_dev_info *bdi, int for_kupdate)
wbc.encountered_congestion = 0;
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
wbc.pages_skipped = 0;
- generic_sync_bdi_inodes(bdi->wb_arg.sb, &wbc);
+ generic_sync_wb_inodes(wb, wb->sb, &wbc);
nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
/*
* If we ran out of stuff to write, bail unless more_io got set
@@ -172,17 +189,12 @@ static void bdi_flush(struct backing_dev_info *bdi, int for_kupdate)
* Handle writeback of dirty data for the device backed by this bdi. Also
* wakes up periodically and does kupdated style flushing.
*/
-int bdi_writeback_task(struct backing_dev_info *bdi)
+int bdi_writeback_task(struct bdi_writeback *wb)
{
while (!kthread_should_stop()) {
unsigned long wait_jiffies;
int for_kupdate;
- wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
- set_current_state(TASK_INTERRUPTIBLE);
- schedule_timeout(wait_jiffies);
- try_to_freeze();
-
/*
* We get here in two cases:
*
@@ -197,7 +209,7 @@ int bdi_writeback_task(struct backing_dev_info *bdi)
* pdflush style writeout.
*
*/
- for_kupdate = writeback_acquire(bdi);
+ for_kupdate = writeback_acquire(wb);
if (for_kupdate) {
long nr;
@@ -205,13 +217,18 @@ int bdi_writeback_task(struct backing_dev_info *bdi)
global_page_state(NR_UNSTABLE_NFS) +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
- bdi->wb_arg.nr_pages = nr;
- bdi->wb_arg.sb = NULL;
- bdi->wb_arg.sync_mode = WB_SYNC_NONE;
+ wb->nr_pages = nr;
+ wb->sb = NULL;
+ wb->sync_mode = WB_SYNC_NONE;
}
- bdi_flush(bdi, for_kupdate);
- writeback_release(bdi);
+ wb_writeback(wb, for_kupdate);
+ writeback_release(wb);
+
+ wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(wait_jiffies);
+ try_to_freeze();
}
return 0;
@@ -254,6 +271,14 @@ static noinline void block_dump___mark_inode_dirty(struct inode *inode)
}
}
+/*
+ * We have only a single wb per bdi, so just return that.
+ */
+static inline struct bdi_writeback *inode_get_wb(struct inode *inode)
+{
+ return &inode_to_bdi(inode)->wb;
+}
+
/**
* __mark_inode_dirty - internal function
* @inode: inode to mark
@@ -337,9 +362,10 @@ void __mark_inode_dirty(struct inode *inode, int flags)
* reposition it (that would break b_dirty time-ordering).
*/
if (!was_dirty) {
+ struct bdi_writeback *wb = inode_get_wb(inode);
+
inode->dirtied_when = jiffies;
- list_move(&inode->i_list,
- &inode_to_bdi(inode)->b_dirty);
+ list_move(&inode->i_list, &wb->b_dirty);
}
}
out:
@@ -366,16 +392,16 @@ static int write_inode(struct inode *inode, int sync)
*/
static void redirty_tail(struct inode *inode)
{
- struct backing_dev_info *bdi = inode_to_bdi(inode);
+ struct bdi_writeback *wb = inode_get_wb(inode);
- if (!list_empty(&bdi->b_dirty)) {
+ if (!list_empty(&wb->b_dirty)) {
struct inode *tail;
- tail = list_entry(bdi->b_dirty.next, struct inode, i_list);
+ tail = list_entry(wb->b_dirty.next, struct inode, i_list);
if (time_before(inode->dirtied_when, tail->dirtied_when))
inode->dirtied_when = jiffies;
}
- list_move(&inode->i_list, &bdi->b_dirty);
+ list_move(&inode->i_list, &wb->b_dirty);
}
/*
@@ -383,7 +409,9 @@ static void redirty_tail(struct inode *inode)
*/
static void requeue_io(struct inode *inode)
{
- list_move(&inode->i_list, &inode_to_bdi(inode)->b_more_io);
+ struct bdi_writeback *wb = inode_get_wb(inode);
+
+ list_move(&inode->i_list, &wb->b_more_io);
}
static void inode_sync_complete(struct inode *inode)
@@ -430,11 +458,10 @@ static void move_expired_inodes(struct list_head *delaying_queue,
/*
* Queue all expired dirty inodes for io, eldest first.
*/
-static void queue_io(struct backing_dev_info *bdi,
- unsigned long *older_than_this)
+static void queue_io(struct bdi_writeback *wb, unsigned long *older_than_this)
{
- list_splice_init(&bdi->b_more_io, bdi->b_io.prev);
- move_expired_inodes(&bdi->b_dirty, &bdi->b_io, older_than_this);
+ list_splice_init(&wb->b_more_io, wb->b_io.prev);
+ move_expired_inodes(&wb->b_dirty, &wb->b_io, older_than_this);
}
/*
@@ -593,20 +620,20 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
return ret;
}
-void generic_sync_bdi_inodes(struct super_block *sb,
- struct writeback_control *wbc)
+static void generic_sync_wb_inodes(struct bdi_writeback *wb,
+ struct super_block *sb,
+ struct writeback_control *wbc)
{
const int is_blkdev_sb = sb_is_blkdev_sb(sb);
- struct backing_dev_info *bdi = wbc->bdi;
const unsigned long start = jiffies; /* livelock avoidance */
spin_lock(&inode_lock);
- if (!wbc->for_kupdate || list_empty(&bdi->b_io))
- queue_io(bdi, wbc->older_than_this);
+ if (!wbc->for_kupdate || list_empty(&wb->b_io))
+ queue_io(wb, wbc->older_than_this);
- while (!list_empty(&bdi->b_io)) {
- struct inode *inode = list_entry(bdi->b_io.prev,
+ while (!list_empty(&wb->b_io)) {
+ struct inode *inode = list_entry(wb->b_io.prev,
struct inode, i_list);
long pages_skipped;
@@ -618,7 +645,7 @@ void generic_sync_bdi_inodes(struct super_block *sb,
continue;
}
- if (!bdi_cap_writeback_dirty(bdi)) {
+ if (!bdi_cap_writeback_dirty(wb->bdi)) {
redirty_tail(inode);
if (is_blkdev_sb) {
/*
@@ -640,7 +667,7 @@ void generic_sync_bdi_inodes(struct super_block *sb,
continue;
}
- if (wbc->nonblocking && bdi_write_congested(bdi)) {
+ if (wbc->nonblocking && bdi_write_congested(wb->bdi)) {
wbc->encountered_congestion = 1;
if (!is_blkdev_sb)
break; /* Skip a congested fs */
@@ -674,7 +701,7 @@ void generic_sync_bdi_inodes(struct super_block *sb,
wbc->more_io = 1;
break;
}
- if (!list_empty(&bdi->b_more_io))
+ if (!list_empty(&wb->b_more_io))
wbc->more_io = 1;
}
@@ -682,6 +709,14 @@ void generic_sync_bdi_inodes(struct super_block *sb,
/* Leave any unwritten inodes on b_io */
}
+void generic_sync_bdi_inodes(struct super_block *sb,
+ struct writeback_control *wbc)
+{
+ struct backing_dev_info *bdi = wbc->bdi;
+
+ generic_sync_wb_inodes(&bdi->wb, sb, wbc);
+}
+
/*
* Write out a superblock's list of dirty inodes. A wait will be performed
* upon no inodes, all inodes or the final one, depending upon sync_mode.
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 8860264..d2055fd 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -24,8 +24,8 @@ struct dentry;
* Bits in backing_dev_info.state
*/
enum bdi_state {
- BDI_pdflush, /* A pdflush thread is working this device */
BDI_pending, /* On its way to being activated */
+ BDI_wb_alloc, /* Default embedded wb allocated */
BDI_async_congested, /* The async (write) queue is getting full */
BDI_sync_congested, /* The sync queue is getting full */
BDI_unused, /* Available bits start here */
@@ -41,15 +41,22 @@ enum bdi_stat_item {
#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
-struct bdi_writeback_arg {
- unsigned long nr_pages;
- struct super_block *sb;
+struct bdi_writeback {
+ struct backing_dev_info *bdi; /* our parent bdi */
+ unsigned int nr;
+
+ struct task_struct *task; /* writeback task */
+ struct list_head b_dirty; /* dirty inodes */
+ struct list_head b_io; /* parked for writeback */
+ struct list_head b_more_io; /* parked for more writeback */
+
+ unsigned long nr_pages;
+ struct super_block *sb;
enum writeback_sync_modes sync_mode;
};
struct backing_dev_info {
struct list_head bdi_list;
-
unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
unsigned long state; /* Always use atomic bitops on this */
unsigned int capabilities; /* Device capabilities */
@@ -66,13 +73,11 @@ struct backing_dev_info {
unsigned int min_ratio;
unsigned int max_ratio, max_prop_frac;
- struct device *dev;
+ struct bdi_writeback wb; /* default writeback info for this bdi */
+ unsigned long wb_active; /* bitmap of active tasks */
+ unsigned long wb_mask; /* number of registered tasks */
- struct task_struct *task; /* writeback task */
- struct bdi_writeback_arg wb_arg; /* protected by BDI_pdflush */
- struct list_head b_dirty; /* dirty inodes */
- struct list_head b_io; /* parked for writeback */
- struct list_head b_more_io; /* parked for more writeback */
+ struct device *dev;
#ifdef CONFIG_DEBUG_FS
struct dentry *debug_dir;
@@ -89,17 +94,18 @@ int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
void bdi_unregister(struct backing_dev_info *bdi);
void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
long nr_pages, enum writeback_sync_modes sync_mode);
-int bdi_writeback_task(struct backing_dev_info *bdi);
+int bdi_writeback_task(struct bdi_writeback *wb);
void bdi_writeback_all(struct super_block *sb, struct writeback_control *wbc);
+int bdi_has_dirty_io(struct backing_dev_info *bdi);
extern spinlock_t bdi_lock;
extern struct list_head bdi_list;
-static inline int bdi_has_dirty_io(struct backing_dev_info *bdi)
+static inline int wb_has_dirty_io(struct bdi_writeback *wb)
{
- return !list_empty(&bdi->b_dirty) ||
- !list_empty(&bdi->b_io) ||
- !list_empty(&bdi->b_more_io);
+ return !list_empty(&wb->b_dirty) ||
+ !list_empty(&wb->b_io) ||
+ !list_empty(&wb->b_more_io);
}
static inline void __add_bdi_stat(struct backing_dev_info *bdi,
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index b44f793..2b72b08 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -215,10 +215,45 @@ static int __init default_bdi_init(void)
}
subsys_initcall(default_bdi_init);
+static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
+{
+ memset(wb, 0, sizeof(*wb));
+
+ wb->bdi = bdi;
+ INIT_LIST_HEAD(&wb->b_dirty);
+ INIT_LIST_HEAD(&wb->b_io);
+ INIT_LIST_HEAD(&wb->b_more_io);
+}
+
+static int wb_assign_nr(struct backing_dev_info *bdi, struct bdi_writeback *wb)
+{
+ set_bit(0, &bdi->wb_mask);
+ wb->nr = 0;
+ return 0;
+}
+
+static void bdi_put_wb(struct backing_dev_info *bdi, struct bdi_writeback *wb)
+{
+ clear_bit(wb->nr, &bdi->wb_mask);
+ clear_bit(BDI_wb_alloc, &bdi->state);
+}
+
+static struct bdi_writeback *bdi_new_wb(struct backing_dev_info *bdi)
+{
+ struct bdi_writeback *wb;
+
+ set_bit(BDI_wb_alloc, &bdi->state);
+ wb = &bdi->wb;
+ wb_assign_nr(bdi, wb);
+ return wb;
+}
+
static int bdi_start_fn(void *ptr)
{
- struct backing_dev_info *bdi = ptr;
+ struct bdi_writeback *wb = ptr;
+ struct backing_dev_info *bdi = wb->bdi;
struct task_struct *tsk = current;
+ int ret;
/*
* Add us to the active bdi_list
@@ -242,7 +277,16 @@ static int bdi_start_fn(void *ptr)
smp_mb__after_clear_bit();
wake_up_bit(&bdi->state, BDI_pending);
- return bdi_writeback_task(bdi);
+ ret = bdi_writeback_task(wb);
+
+ wb->task = NULL;
+ bdi_put_wb(bdi, wb);
+ return ret;
+}
+
+int bdi_has_dirty_io(struct backing_dev_info *bdi)
+{
+ return wb_has_dirty_io(&bdi->wb);
}
static void bdi_flush_io(struct backing_dev_info *bdi)
@@ -297,17 +341,18 @@ static void sync_supers_timer_fn(unsigned long unused)
static int bdi_forker_task(void *ptr)
{
- struct backing_dev_info *me = ptr;
+ struct bdi_writeback *me = ptr;
for (;;) {
struct backing_dev_info *bdi, *tmp;
+ struct bdi_writeback *wb;
/*
* Temporary measure, we want to make sure we don't see
* dirty data on the default backing_dev_info
*/
- if (bdi_has_dirty_io(me))
- bdi_flush_io(me);
+ if (wb_has_dirty_io(me))
+ bdi_flush_io(me->bdi);
spin_lock(&bdi_lock);
@@ -316,7 +361,7 @@ static int bdi_forker_task(void *ptr)
* a thread registered. If so, set that up.
*/
list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
- if (bdi->task || !bdi_has_dirty_io(bdi))
+ if (bdi->wb.task || !bdi_has_dirty_io(bdi))
continue;
bdi_add_default_flusher_task(bdi);
@@ -345,9 +390,11 @@ static int bdi_forker_task(void *ptr)
list_del_init(&bdi->bdi_list);
spin_unlock(&bdi_lock);
- BUG_ON(bdi->task);
+ wb = bdi_new_wb(bdi);
+ if (!wb)
+ goto readd_flush;
- bdi->task = kthread_run(bdi_start_fn, bdi, "flush-%s",
+ wb->task = kthread_run(bdi_start_fn, wb, "flush-%s",
dev_name(bdi->dev));
/*
* If task creation fails, then readd the bdi to
@@ -355,9 +402,10 @@ static int bdi_forker_task(void *ptr)
* from this forker thread. That will free some memory
* and we can try again.
*/
- if (IS_ERR(bdi->task)) {
- bdi->task = NULL;
-
+ if (IS_ERR(wb->task)) {
+ wb->task = NULL;
+ bdi_put_wb(bdi, wb);
+readd_flush:
/*
* Add this 'bdi' to the back, so we get
* a chance to flush other bdi's to free
@@ -380,6 +428,9 @@ static int bdi_forker_task(void *ptr)
*/
static void bdi_add_default_flusher_task(struct backing_dev_info *bdi)
{
+ if (!bdi_cap_writeback_dirty(bdi))
+ return;
+
/*
* Someone already marked this pending for task creation
*/
@@ -390,7 +441,7 @@ static void bdi_add_default_flusher_task(struct backing_dev_info *bdi)
list_move_tail(&bdi->bdi_list, &bdi_pending_list);
spin_unlock(&bdi_lock);
- wake_up_process(default_backing_dev_info.task);
+ wake_up_process(default_backing_dev_info.wb.task);
}
int bdi_register(struct backing_dev_info *bdi, struct device *parent,
@@ -423,14 +474,24 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
* on-demand when they need it.
*/
if (bdi_cap_flush_forker(bdi)) {
- bdi->task = kthread_run(bdi_forker_task, bdi, "bdi-%s",
+ struct bdi_writeback *wb;
+
+ wb = bdi_new_wb(bdi);
+ if (!wb) {
+ ret = -ENOMEM;
+ goto remove_err;
+ }
+
+ wb->task = kthread_run(bdi_forker_task, wb, "bdi-%s",
dev_name(dev));
- if (IS_ERR(bdi->task)) {
- bdi->task = NULL;
+ if (IS_ERR(wb->task)) {
+ wb->task = NULL;
+ bdi_put_wb(bdi, wb);
+ ret = -ENOMEM;
+remove_err:
spin_lock(&bdi_lock);
list_del(&bdi->bdi_list);
spin_unlock(&bdi_lock);
- ret = -ENOMEM;
goto exit;
}
}
@@ -454,10 +515,13 @@ static int sched_wait(void *word)
}
/*
- * Remove bdi from the global list
+ * Remove bdi from the global list and shutdown any threads we have running
*/
static void bdi_wb_shutdown(struct backing_dev_info *bdi)
{
+ if (!bdi_cap_writeback_dirty(bdi))
+ return;
+
/*
* If setup is pending, wait for that to complete first
*/
@@ -469,18 +533,18 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
spin_lock(&bdi_lock);
list_del(&bdi->bdi_list);
spin_unlock(&bdi_lock);
+
+ /*
+ * Finally, kill the kernel thread
+ */
+ kthread_stop(bdi->wb.task);
}
void bdi_unregister(struct backing_dev_info *bdi)
{
if (bdi->dev) {
- if (!bdi_cap_flush_forker(bdi)) {
+ if (!bdi_cap_flush_forker(bdi))
bdi_wb_shutdown(bdi);
- if (bdi->task) {
- kthread_stop(bdi->task);
- bdi->task = NULL;
- }
- }
bdi_debug_unregister(bdi);
device_unregister(bdi->dev);
bdi->dev = NULL;
@@ -498,9 +562,9 @@ int bdi_init(struct backing_dev_info *bdi)
bdi->max_ratio = 100;
bdi->max_prop_frac = PROP_FRAC_BASE;
INIT_LIST_HEAD(&bdi->bdi_list);
- INIT_LIST_HEAD(&bdi->b_io);
- INIT_LIST_HEAD(&bdi->b_dirty);
- INIT_LIST_HEAD(&bdi->b_more_io);
+ bdi->wb_mask = bdi->wb_active = 0;
+
+ bdi_wb_init(&bdi->wb, bdi);
for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
err = percpu_counter_init(&bdi->bdi_stat[i], 0);
@@ -525,9 +589,7 @@ void bdi_destroy(struct backing_dev_info *bdi)
{
int i;
- WARN_ON(!list_empty(&bdi->b_dirty));
- WARN_ON(!list_empty(&bdi->b_io));
- WARN_ON(!list_empty(&bdi->b_more_io));
+ WARN_ON(bdi_has_dirty_io(bdi));
bdi_unregister(bdi);
--
1.6.3.2.306.g4f4fa
^ permalink raw reply related [flat|nested] 30+ messages in thread* [PATCH 5/9] writeback: support > 1 flusher thread per bdi
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
` (3 preceding siblings ...)
2009-07-30 21:23 ` [PATCH 4/9] writeback: separate the flushing state/task from the bdi Jens Axboe
@ 2009-07-30 21:24 ` Jens Axboe
2009-08-05 19:55 ` Jan Kara
2009-08-06 21:33 ` Christoph Hellwig
2009-07-30 21:24 ` [PATCH 6/9] writeback: allow sleepy exit of default writeback task Jens Axboe
` (4 subsequent siblings)
9 siblings, 2 replies; 30+ messages in thread
From: Jens Axboe @ 2009-07-30 21:24 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: chris.mason, david, hch, akpm, jack, yanmin_zhang, richard,
damien.wyart, fweisbec, Alan.Brunelle, Jens Axboe
Build on the bdi_writeback support by allowing registration of
more than 1 flusher thread. File systems can call bdi_add_flusher_task(bdi)
to add more flusher threads to the device. If they do so, they must also
provide a super_operations function to return the suitable bdi_writeback
struct from any given inode.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
fs/fs-writeback.c | 436 +++++++++++++++++++++++++++++++++++--------
include/linux/backing-dev.h | 32 +++-
include/linux/fs.h | 3 +
include/linux/writeback.h | 1 +
mm/backing-dev.c | 254 ++++++++++++++++++++-----
5 files changed, 593 insertions(+), 133 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 86fb2a9..8069483 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -38,77 +38,230 @@ static void generic_sync_wb_inodes(struct bdi_writeback *wb,
*/
int nr_pdflush_threads;
-/**
- * writeback_acquire - attempt to get exclusive writeback access to a device
- * @bdi: the device's backing_dev_info structure
- *
- * It is a waste of resources to have more than one pdflush thread blocked on
- * a single request queue. Exclusion at the request_queue level is obtained
- * via a flag in the request_queue's backing_dev_info.state.
- *
- * Non-request_queue-backed address_spaces will share default_backing_dev_info,
- * unless they implement their own. Which is somewhat inefficient, as this
- * may prevent concurrent writeback against multiple devices.
+static void generic_sync_wb_inodes(struct bdi_writeback *wb,
+ struct super_block *sb,
+ struct writeback_control *wbc);
+
+/*
+ * Work items for the bdi_writeback threads
*/
-static int writeback_acquire(struct bdi_writeback *wb)
+struct bdi_work {
+ struct list_head list;
+ struct list_head wait_list;
+ struct rcu_head rcu_head;
+
+ unsigned long seen;
+ atomic_t pending;
+
+ unsigned long sb_data;
+ unsigned long nr_pages;
+ enum writeback_sync_modes sync_mode;
+
+ unsigned long state;
+};
+
+static struct super_block *bdi_work_sb(struct bdi_work *work)
{
- struct backing_dev_info *bdi = wb->bdi;
+ return (struct super_block *) (work->sb_data & ~1UL);
+}
+
+static inline bool bdi_work_on_stack(struct bdi_work *work)
+{
+ return work->sb_data & 1UL;
+}
+
+static inline void bdi_work_init(struct bdi_work *work, struct super_block *sb,
+ unsigned long nr_pages,
+ enum writeback_sync_modes sync_mode)
+{
+ INIT_RCU_HEAD(&work->rcu_head);
+ work->sb_data = (unsigned long) sb;
+ work->nr_pages = nr_pages;
+ work->sync_mode = sync_mode;
+ work->state = 1;
+}
- return !test_and_set_bit(wb->nr, &bdi->wb_active);
+static inline void bdi_work_init_on_stack(struct bdi_work *work,
+ struct super_block *sb,
+ unsigned long nr_pages,
+ enum writeback_sync_modes sync_mode)
+{
+ bdi_work_init(work, sb, nr_pages, sync_mode);
+ work->sb_data |= 1UL;
}
/**
* writeback_in_progress - determine whether there is writeback in progress
* @bdi: the device's backing_dev_info structure.
*
- * Determine whether there is writeback in progress against a backing device.
+ * Determine whether there is writeback waiting to be handled against a
+ * backing device.
*/
int writeback_in_progress(struct backing_dev_info *bdi)
{
- return bdi->wb_active != 0;
+ return !list_empty(&bdi->work_list);
}
-/**
- * writeback_release - relinquish exclusive writeback access against a device.
- * @bdi: the device's backing_dev_info structure
- */
-static void writeback_release(struct bdi_writeback *wb)
+static void bdi_work_clear(struct bdi_work *work)
{
- struct backing_dev_info *bdi = wb->bdi;
+ clear_bit(0, &work->state);
+ smp_mb__after_clear_bit();
+ wake_up_bit(&work->state, 0);
+}
+
+static void bdi_work_free(struct rcu_head *head)
+{
+ struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
- wb->nr_pages = 0;
- wb->sb = NULL;
- clear_bit(wb->nr, &bdi->wb_active);
+ if (!bdi_work_on_stack(work))
+ kfree(work);
+ else
+ bdi_work_clear(work);
}
-static void wb_start_writeback(struct bdi_writeback *wb, struct super_block *sb,
- long nr_pages,
- enum writeback_sync_modes sync_mode)
+static void wb_work_complete(struct bdi_work *work)
{
- if (!wb_has_dirty_io(wb))
- return;
+ const enum writeback_sync_modes sync_mode = work->sync_mode;
- if (writeback_acquire(wb)) {
- wb->nr_pages = nr_pages;
- wb->sb = sb;
- wb->sync_mode = sync_mode;
+ /*
+ * For allocated work, we can clear the done/seen bit right here.
+ * For on-stack work, we need to postpone both the clear and free
+ * to after the RCU grace period, since the stack could be invalidated
+ * as soon as bdi_work_clear() has done the wakeup.
+ */
+ if (!bdi_work_on_stack(work))
+ bdi_work_clear(work);
+ if (sync_mode == WB_SYNC_NONE || bdi_work_on_stack(work))
+ call_rcu(&work->rcu_head, bdi_work_free);
+}
- if (wb->task)
- wake_up_process(wb->task);
+static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
+{
+ /*
+ * The caller has retrieved the work arguments from this work,
+ * drop our reference. If this is the last ref, delete and free it
+ */
+ if (atomic_dec_and_test(&work->pending)) {
+ struct backing_dev_info *bdi = wb->bdi;
+
+ spin_lock(&bdi->wb_lock);
+ list_del_rcu(&work->list);
+ spin_unlock(&bdi->wb_lock);
+
+ wb_work_complete(work);
}
}
-void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
- long nr_pages, enum writeback_sync_modes sync_mode)
+static void wb_start_writeback(struct bdi_writeback *wb, struct bdi_work *work)
+{
+ /*
+ * If we failed allocating the bdi work item, wake up the wb thread
+ * always. As a safety precaution, it'll flush out everything
+ */
+ if (!wb_has_dirty_io(wb) && work)
+ wb_clear_pending(wb, work);
+ else if (wb->task)
+ wake_up_process(wb->task);
+}
+
+static void bdi_sched_work(struct backing_dev_info *bdi, struct bdi_work *work)
{
+ if (!bdi_wblist_needs_lock(bdi))
+ wb_start_writeback(&bdi->wb, work);
+ else {
+ struct bdi_writeback *wb;
+ int idx;
+
+ idx = srcu_read_lock(&bdi->srcu);
+
+ list_for_each_entry_rcu(wb, &bdi->wb_list, list)
+ wb_start_writeback(wb, work);
+
+ srcu_read_unlock(&bdi->srcu, idx);
+ }
+}
+
+static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
+{
+ if (work) {
+ work->seen = bdi->wb_mask;
+ BUG_ON(!work->seen);
+ atomic_set(&work->pending, bdi->wb_cnt);
+ BUG_ON(!bdi->wb_cnt);
+
+ /*
+ * Make sure stores are seen before it appears on the list
+ */
+ smp_mb();
+
+ spin_lock(&bdi->wb_lock);
+ list_add_tail_rcu(&work->list, &bdi->work_list);
+ spin_unlock(&bdi->wb_lock);
+ }
+
/*
- * This only happens the first time someone kicks this bdi, so put
- * it out-of-line.
+ * If the default thread isn't there, make sure we add it. When
+ * it gets created and wakes up, we'll run this work.
*/
- if (unlikely(!bdi->wb.task))
+ if (unlikely(list_empty_careful(&bdi->wb_list)))
wake_up_process(default_backing_dev_info.wb.task);
+ else
+ bdi_sched_work(bdi, work);
+}
+
+/*
+ * Used for on-stack allocated work items. The caller needs to wait until
+ * the wb threads have acked the work before it's safe to continue.
+ */
+static void bdi_wait_on_work_clear(struct bdi_work *work)
+{
+ wait_on_bit(&work->state, 0, bdi_sched_wait, TASK_UNINTERRUPTIBLE);
+}
+
+static struct bdi_work *bdi_alloc_work(struct super_block *sb, long nr_pages,
+ enum writeback_sync_modes sync_mode)
+{
+ struct bdi_work *work;
+
+ work = kmalloc(sizeof(*work), GFP_ATOMIC);
+ if (work)
+ bdi_work_init(work, sb, nr_pages, sync_mode);
- wb_start_writeback(&bdi->wb, sb, nr_pages, sync_mode);
+ return work;
+}
+
+void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
+ long nr_pages, enum writeback_sync_modes sync_mode)
+{
+ const bool must_wait = sync_mode == WB_SYNC_ALL;
+ struct bdi_work work_stack, *work = NULL;
+
+ if (!must_wait)
+ work = bdi_alloc_work(sb, nr_pages, sync_mode);
+
+ if (!work) {
+ work = &work_stack;
+ bdi_work_init_on_stack(work, sb, nr_pages, sync_mode);
+ }
+
+ bdi_queue_work(bdi, work);
+
+ /*
+ * If the sync mode is WB_SYNC_ALL, block waiting for the work to
+ * complete. If not, we only need to wait for the work to be started,
+ * if we allocated it on-stack. We use the same mechanism, if the
+ * wait bit is set in the bdi_work struct, then threads will not
+ * clear pending until after they are done.
+ *
+ * Note that work == &work_stack if must_wait is true, so we don't
+ * need to do call_rcu() here ever, since the completion path will
+ * have done that for us.
+ */
+ if (must_wait || work == &work_stack) {
+ bdi_wait_on_work_clear(work);
+ if (work != &work_stack)
+ call_rcu(&work->rcu_head, bdi_work_free);
+ }
}
/*
@@ -145,17 +298,19 @@ static inline bool over_bground_thresh(void)
* older_than_this takes precedence over nr_to_write. So we'll only write back
* all dirty pages if they are all attached to "old" mappings.
*/
-static void wb_writeback(struct bdi_writeback *wb, int for_kupdate)
+static long wb_writeback(struct bdi_writeback *wb, long nr_pages,
+ struct super_block *sb,
+ enum writeback_sync_modes sync_mode, int for_kupdate)
{
struct writeback_control wbc = {
.bdi = wb->bdi,
- .sync_mode = wb->sync_mode,
+ .sync_mode = sync_mode,
.older_than_this = NULL,
.for_kupdate = for_kupdate,
.range_cyclic = 1,
};
unsigned long oldest_jif;
- long nr_pages = wb->nr_pages;
+ long wrote = 0;
if (wbc.for_kupdate) {
wbc.older_than_this = &oldest_jif;
@@ -164,7 +319,7 @@ static void wb_writeback(struct bdi_writeback *wb, int for_kupdate)
}
for (;;) {
- if (wbc.sync_mode == WB_SYNC_NONE && nr_pages <= 0 &&
+ if (sync_mode == WB_SYNC_NONE && nr_pages <= 0 &&
!over_bground_thresh())
break;
@@ -172,8 +327,9 @@ static void wb_writeback(struct bdi_writeback *wb, int for_kupdate)
wbc.encountered_congestion = 0;
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
wbc.pages_skipped = 0;
- generic_sync_wb_inodes(wb, wb->sb, &wbc);
+ generic_sync_wb_inodes(wb, sb, &wbc);
nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
+ wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;
/*
* If we ran out of stuff to write, bail unless more_io got set
*/
@@ -183,47 +339,95 @@ static void wb_writeback(struct bdi_writeback *wb, int for_kupdate)
break;
}
}
+
+ return wrote;
}
/*
- * Handle writeback of dirty data for the device backed by this bdi. Also
- * wakes up periodically and does kupdated style flushing.
+ * Return the next bdi_work struct that hasn't been processed by this
+ * wb thread yet
*/
-int bdi_writeback_task(struct bdi_writeback *wb)
+static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
+ struct bdi_writeback *wb)
{
- while (!kthread_should_stop()) {
- unsigned long wait_jiffies;
- int for_kupdate;
+ struct bdi_work *work, *ret = NULL;
+
+ rcu_read_lock();
+
+ list_for_each_entry_rcu(work, &bdi->work_list, list) {
+ if (!test_and_clear_bit(wb->nr, &work->seen))
+ continue;
+
+ ret = work;
+ break;
+ }
+
+ rcu_read_unlock();
+ return ret;
+}
+
+/*
+ * Retrieve work items and do the writeback they describe
+ */
+void wb_do_writeback(struct bdi_writeback *wb, int force_wait)
+{
+ struct backing_dev_info *bdi = wb->bdi;
+ struct bdi_work *work;
+ long nr_pages, wrote = 0;
+
+ while ((work = get_next_work_item(bdi, wb)) != NULL) {
+ struct super_block *sb = bdi_work_sb(work);
+ enum writeback_sync_modes sync_mode;
+
+ nr_pages = work->nr_pages;
/*
- * We get here in two cases:
- *
- * schedule_timeout() returned because the dirty writeback
- * interval has elapsed. If that happens, we will be able
- * to acquire the writeback lock and will proceed to do
- * kupdated style writeout.
- *
- * Someone called bdi_start_writeback(), which will acquire
- * the writeback lock. This means our writeback_acquire()
- * below will fail and we call into bdi_pdflush() for
- * pdflush style writeout.
- *
+ * Override sync mode, in case we must wait for completion
*/
- for_kupdate = writeback_acquire(wb);
- if (for_kupdate) {
- long nr;
+ if (force_wait)
+ work->sync_mode = sync_mode = WB_SYNC_ALL;
+ else
+ sync_mode = work->sync_mode;
- nr = global_page_state(NR_FILE_DIRTY) +
+ /*
+ * If this isn't a data integrity operation, just notify
+ * that we have seen this work and we are now starting it.
+ */
+ if (sync_mode == WB_SYNC_NONE)
+ wb_clear_pending(wb, work);
+
+ wrote += wb_writeback(wb, nr_pages, sb, sync_mode, 0);
+
+ /*
+ * This is a data integrity writeback, so only do the
+ * notification when we have completed the work.
+ */
+ if (sync_mode == WB_SYNC_ALL)
+ wb_clear_pending(wb, work);
+ }
+
+ /*
+ * Check for periodic writeback, kupdated() style
+ */
+ if (!wrote) {
+ nr_pages = global_page_state(NR_FILE_DIRTY) +
global_page_state(NR_UNSTABLE_NFS) +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
- wb->nr_pages = nr;
- wb->sb = NULL;
- wb->sync_mode = WB_SYNC_NONE;
- }
+ wb_writeback(wb, nr_pages, NULL, WB_SYNC_NONE, 1);
+ }
+}
- wb_writeback(wb, for_kupdate);
- writeback_release(wb);
+/*
+ * Handle writeback of dirty data for the device backed by this bdi. Also
+ * wakes up periodically and does kupdated style flushing.
+ */
+int bdi_writeback_task(struct bdi_writeback *wb)
+{
+ while (!kthread_should_stop()) {
+ unsigned long wait_jiffies;
+
+ wb_do_writeback(wb, 0);
wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
set_current_state(TASK_INTERRUPTIBLE);
@@ -234,19 +438,68 @@ int bdi_writeback_task(struct bdi_writeback *wb)
return 0;
}
+/*
+ * Schedule writeback for all backing devices. Expensive! If this is a data
+ * integrity operation, writeback will be complete when this returns. If
+ * we are simply called for WB_SYNC_NONE, then writeback will merely be
+ * scheduled to run.
+ */
void bdi_writeback_all(struct super_block *sb, struct writeback_control *wbc)
{
+ const bool must_wait = wbc->sync_mode == WB_SYNC_ALL;
struct backing_dev_info *bdi;
+ struct bdi_work *work;
+ LIST_HEAD(list);
+restart:
spin_lock(&bdi_lock);
list_for_each_entry(bdi, &bdi_list, bdi_list) {
+ struct bdi_work *work;
+
if (!bdi_has_dirty_io(bdi))
continue;
- bdi_start_writeback(bdi, sb, wbc->nr_to_write, wbc->sync_mode);
+
+ /*
+ * If work allocation fails, do the writes inline. We drop
+ * the lock and restart the list writeout. This should be OK,
+ * since this happens rarely and because the writeout should
+ * eventually make more free memory available.
+ */
+ work = bdi_alloc_work(sb, wbc->nr_to_write, wbc->sync_mode);
+ if (!work) {
+ struct writeback_control __wbc = *wbc;
+
+ /*
+ * Not a data integrity writeout, just continue
+ */
+ if (!must_wait)
+ continue;
+
+ spin_unlock(&bdi_lock);
+ __wbc = *wbc;
+ __wbc.bdi = bdi;
+ generic_sync_bdi_inodes(sb, &__wbc);
+ goto restart;
+ }
+ if (must_wait)
+ list_add_tail(&work->wait_list, &list);
+
+ bdi_queue_work(bdi, work);
}
spin_unlock(&bdi_lock);
+
+ /*
+ * If this is for WB_SYNC_ALL, wait for pending work to complete
+ * before returning.
+ */
+ while (!list_empty(&list)) {
+ work = list_entry(list.next, struct bdi_work, wait_list);
+ list_del(&work->wait_list);
+ bdi_wait_on_work_clear(work);
+ call_rcu(&work->rcu_head, bdi_work_free);
+ }
}
static noinline void block_dump___mark_inode_dirty(struct inode *inode)
@@ -272,11 +525,18 @@ static noinline void block_dump___mark_inode_dirty(struct inode *inode)
}
/*
- * We have only a single wb per bdi, so just return that.
+ * If the filesystem didn't provide a way to map an inode to a dedicated
+ * flusher thread, it doesn't support more than 1 thread. So we know it's
+ * the default thread, return that.
*/
static inline struct bdi_writeback *inode_get_wb(struct inode *inode)
{
- return &inode_to_bdi(inode)->wb;
+ const struct super_operations *sop = inode->i_sb->s_op;
+
+ if (!sop->inode_get_wb)
+ return &inode_to_bdi(inode)->wb;
+
+ return sop->inode_get_wb(inode);
}
/**
@@ -713,8 +973,24 @@ void generic_sync_bdi_inodes(struct super_block *sb,
struct writeback_control *wbc)
{
struct backing_dev_info *bdi = wbc->bdi;
+ struct bdi_writeback *wb;
- generic_sync_wb_inodes(&bdi->wb, sb, wbc);
+ /*
+ * Common case is just a single wb thread and that is embedded in
+ * the bdi, so it doesn't need locking
+ */
+ if (!bdi_wblist_needs_lock(bdi))
+ generic_sync_wb_inodes(&bdi->wb, sb, wbc);
+ else {
+ int idx;
+
+ idx = srcu_read_lock(&bdi->srcu);
+
+ list_for_each_entry_rcu(wb, &bdi->wb_list, list)
+ generic_sync_wb_inodes(wb, sb, wbc);
+
+ srcu_read_unlock(&bdi->srcu, idx);
+ }
}
/*
@@ -741,7 +1017,7 @@ void generic_sync_sb_inodes(struct super_block *sb,
struct writeback_control *wbc)
{
if (wbc->bdi)
- generic_sync_bdi_inodes(sb, wbc);
+ bdi_start_writeback(wbc->bdi, sb, wbc->nr_to_write, wbc->sync_mode);
else
bdi_writeback_all(sb, wbc);
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index d2055fd..90a1910 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -13,6 +13,8 @@
#include <linux/proportions.h>
#include <linux/kernel.h>
#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/srcu.h>
#include <linux/writeback.h>
#include <asm/atomic.h>
@@ -26,6 +28,7 @@ struct dentry;
enum bdi_state {
BDI_pending, /* On its way to being activated */
BDI_wb_alloc, /* Default embedded wb allocated */
+ BDI_wblist_lock, /* bdi->wb_list now needs locking */
BDI_async_congested, /* The async (write) queue is getting full */
BDI_sync_congested, /* The sync queue is getting full */
BDI_unused, /* Available bits start here */
@@ -42,6 +45,8 @@ enum bdi_stat_item {
#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
struct bdi_writeback {
+ struct list_head list; /* hangs off the bdi */
+
struct backing_dev_info *bdi; /* our parent bdi */
unsigned int nr;
@@ -49,13 +54,12 @@ struct bdi_writeback {
struct list_head b_dirty; /* dirty inodes */
struct list_head b_io; /* parked for writeback */
struct list_head b_more_io; /* parked for more writeback */
-
- unsigned long nr_pages;
- struct super_block *sb;
- enum writeback_sync_modes sync_mode;
};
+#define BDI_MAX_FLUSHERS 32
+
struct backing_dev_info {
+ struct srcu_struct srcu; /* for wb_list read side protection */
struct list_head bdi_list;
unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
unsigned long state; /* Always use atomic bitops on this */
@@ -74,8 +78,12 @@ struct backing_dev_info {
unsigned int max_ratio, max_prop_frac;
struct bdi_writeback wb; /* default writeback info for this bdi */
- unsigned long wb_active; /* bitmap of active tasks */
- unsigned long wb_mask; /* number of registered tasks */
+ spinlock_t wb_lock; /* protects update side of wb_list */
+ struct list_head wb_list; /* the flusher threads hanging off this bdi */
+ unsigned long wb_mask; /* bitmask of registered tasks */
+ unsigned int wb_cnt; /* number of registered tasks */
+
+ struct list_head work_list;
struct device *dev;
@@ -96,11 +104,17 @@ void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
long nr_pages, enum writeback_sync_modes sync_mode);
int bdi_writeback_task(struct bdi_writeback *wb);
void bdi_writeback_all(struct super_block *sb, struct writeback_control *wbc);
+void bdi_add_flusher_task(struct backing_dev_info *bdi);
int bdi_has_dirty_io(struct backing_dev_info *bdi);
extern spinlock_t bdi_lock;
extern struct list_head bdi_list;
+static inline int bdi_wblist_needs_lock(struct backing_dev_info *bdi)
+{
+ return test_bit(BDI_wblist_lock, &bdi->state);
+}
+
static inline int wb_has_dirty_io(struct bdi_writeback *wb)
{
return !list_empty(&wb->b_dirty) ||
@@ -317,4 +331,10 @@ static inline bool mapping_cap_swap_backed(struct address_space *mapping)
return bdi_cap_swap_backed(mapping->backing_dev_info);
}
+static inline int bdi_sched_wait(void *word)
+{
+ schedule();
+ return 0;
+}
+
#endif /* _LINUX_BACKING_DEV_H */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b8d98e5..694cffd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1552,11 +1552,14 @@ extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
extern ssize_t vfs_writev(struct file *, const struct iovec __user *,
unsigned long, loff_t *);
+struct bdi_writeback;
+
struct super_operations {
struct inode *(*alloc_inode)(struct super_block *sb);
void (*destroy_inode)(struct inode *);
void (*dirty_inode) (struct inode *);
+ struct bdi_writeback *(*inode_get_wb) (struct inode *);
int (*write_inode) (struct inode *, int);
void (*drop_inode) (struct inode *);
void (*delete_inode) (struct inode *);
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 6e416a9..588a449 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -68,6 +68,7 @@ struct writeback_control {
void writeback_inodes(struct writeback_control *wbc);
int inode_wait(void *);
void sync_inodes_sb(struct super_block *, int wait);
+void wb_do_writeback(struct bdi_writeback *wb, int force_wait);
/* writeback.h requires fs.h; it, too, is not included from here. */
static inline void wait_on_inode(struct inode *inode)
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 2b72b08..45dfe51 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -215,52 +215,100 @@ static int __init default_bdi_init(void)
}
subsys_initcall(default_bdi_init);
-static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
+static int wb_assign_nr(struct backing_dev_info *bdi, struct bdi_writeback *wb)
{
- memset(wb, 0, sizeof(*wb));
+ unsigned long mask = BDI_MAX_FLUSHERS - 1;
+ unsigned int nr;
- wb->bdi = bdi;
- INIT_LIST_HEAD(&wb->b_dirty);
- INIT_LIST_HEAD(&wb->b_io);
- INIT_LIST_HEAD(&wb->b_more_io);
-}
+ do {
+ if ((bdi->wb_mask & mask) == mask)
+ return 1;
+
+ nr = find_first_zero_bit(&bdi->wb_mask, BDI_MAX_FLUSHERS);
+ } while (test_and_set_bit(nr, &bdi->wb_mask));
+
+ wb->nr = nr;
+
+ spin_lock(&bdi->wb_lock);
+ bdi->wb_cnt++;
+ spin_unlock(&bdi->wb_lock);
-static int wb_assign_nr(struct backing_dev_info *bdi, struct bdi_writeback *wb)
-{
- set_bit(0, &bdi->wb_mask);
- wb->nr = 0;
return 0;
}
static void bdi_put_wb(struct backing_dev_info *bdi, struct bdi_writeback *wb)
{
- clear_bit(wb->nr, &bdi->wb_mask);
- clear_bit(BDI_wb_alloc, &bdi->state);
+ /*
+ * If this is the default wb thread exiting, leave the bit set
+ * in the wb mask as we set that before it's created as well. This
+ * is done to make sure that assigned work with no thread has at
+ * least one receipient.
+ */
+ if (wb == &bdi->wb)
+ clear_bit(BDI_wb_alloc, &bdi->state);
+ else {
+ clear_bit(wb->nr, &bdi->wb_mask);
+ kfree(wb);
+ spin_lock(&bdi->wb_lock);
+ bdi->wb_cnt--;
+ spin_unlock(&bdi->wb_lock);
+ }
+}
+
+static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
+{
+ memset(wb, 0, sizeof(*wb));
+
+ wb->bdi = bdi;
+ INIT_LIST_HEAD(&wb->b_dirty);
+ INIT_LIST_HEAD(&wb->b_io);
+ INIT_LIST_HEAD(&wb->b_more_io);
+
+ return wb_assign_nr(bdi, wb);
}
static struct bdi_writeback *bdi_new_wb(struct backing_dev_info *bdi)
{
struct bdi_writeback *wb;
- set_bit(BDI_wb_alloc, &bdi->state);
- wb = &bdi->wb;
- wb_assign_nr(bdi, wb);
+ /*
+ * Default bdi->wb is already assigned, so just return it
+ */
+ if (!test_and_set_bit(BDI_wb_alloc, &bdi->state))
+ wb = &bdi->wb;
+ else {
+ wb = kmalloc(sizeof(struct bdi_writeback), GFP_KERNEL);
+ if (wb) {
+ if (bdi_wb_init(wb, bdi)) {
+ kfree(wb);
+ wb = NULL;
+ }
+ }
+ }
+
return wb;
}
-static int bdi_start_fn(void *ptr)
+static void bdi_task_init(struct backing_dev_info *bdi,
+ struct bdi_writeback *wb)
{
- struct bdi_writeback *wb = ptr;
- struct backing_dev_info *bdi = wb->bdi;
struct task_struct *tsk = current;
- int ret;
+ int was_empty;
/*
- * Add us to the active bdi_list
+ * Add us to the active bdi_list. If we are adding threads beyond
+ * the default embedded bdi_writeback, then we need to start using
+ * proper locking. Check the list for empty first, then set the
+ * BDI_wblist_lock flag if there's > 1 entry on the list now
*/
- spin_lock(&bdi_lock);
- list_add(&bdi->bdi_list, &bdi_list);
- spin_unlock(&bdi_lock);
+ spin_lock(&bdi->wb_lock);
+
+ was_empty = list_empty(&bdi->wb_list);
+ list_add_tail_rcu(&wb->list, &bdi->wb_list);
+ if (!was_empty)
+ set_bit(BDI_wblist_lock, &bdi->state);
+
+ spin_unlock(&bdi->wb_lock);
tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;
set_freezable();
@@ -269,6 +317,22 @@ static int bdi_start_fn(void *ptr)
* Our parent may run at a different priority, just set us to normal
*/
set_user_nice(tsk, 0);
+}
+
+static int bdi_start_fn(void *ptr)
+{
+ struct bdi_writeback *wb = ptr;
+ struct backing_dev_info *bdi = wb->bdi;
+ int ret;
+
+ /*
+ * Add us to the active bdi_list
+ */
+ spin_lock(&bdi_lock);
+ list_add(&bdi->bdi_list, &bdi_list);
+ spin_unlock(&bdi_lock);
+
+ bdi_task_init(bdi, wb);
/*
* Clear pending bit and wakeup anybody waiting to tear us down
@@ -279,6 +343,25 @@ static int bdi_start_fn(void *ptr)
ret = bdi_writeback_task(wb);
+ /*
+ * Remove us from the list
+ */
+ spin_lock(&bdi->wb_lock);
+ list_del_rcu(&wb->list);
+ spin_unlock(&bdi->wb_lock);
+
+ /*
+ * wait for rcu grace period to end, so we can free wb
+ */
+ synchronize_srcu(&bdi->srcu);
+
+ /*
+ * Flush any work that raced with us exiting. No new work
+ * will be added, since this bdi isn't discoverable anymore.
+ */
+ if (!list_empty(&bdi->work_list))
+ wb_do_writeback(wb, 1);
+
wb->task = NULL;
bdi_put_wb(bdi, wb);
return ret;
@@ -286,7 +369,26 @@ static int bdi_start_fn(void *ptr)
int bdi_has_dirty_io(struct backing_dev_info *bdi)
{
- return wb_has_dirty_io(&bdi->wb);
+ struct bdi_writeback *wb;
+ int ret = 0;
+
+ if (!bdi_wblist_needs_lock(bdi))
+ ret = wb_has_dirty_io(&bdi->wb);
+ else {
+ int idx;
+
+ idx = srcu_read_lock(&bdi->srcu);
+
+ list_for_each_entry_rcu(wb, &bdi->wb_list, list) {
+ ret = wb_has_dirty_io(wb);
+ if (ret)
+ break;
+ }
+
+ srcu_read_unlock(&bdi->srcu, idx);
+ }
+
+ return ret;
}
static void bdi_flush_io(struct backing_dev_info *bdi)
@@ -343,6 +445,8 @@ static int bdi_forker_task(void *ptr)
{
struct bdi_writeback *me = ptr;
+ bdi_task_init(me->bdi, me);
+
for (;;) {
struct backing_dev_info *bdi, *tmp;
struct bdi_writeback *wb;
@@ -351,8 +455,8 @@ static int bdi_forker_task(void *ptr)
* Temporary measure, we want to make sure we don't see
* dirty data on the default backing_dev_info
*/
- if (wb_has_dirty_io(me))
- bdi_flush_io(me->bdi);
+ if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
+ wb_do_writeback(me, 0);
spin_lock(&bdi_lock);
@@ -361,7 +465,10 @@ static int bdi_forker_task(void *ptr)
* a thread registered. If so, set that up.
*/
list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
- if (bdi->wb.task || !bdi_has_dirty_io(bdi))
+ if (bdi->wb.task)
+ continue;
+ if (list_empty(&bdi->work_list) &&
+ !bdi_has_dirty_io(bdi))
continue;
bdi_add_default_flusher_task(bdi);
@@ -423,26 +530,69 @@ readd_flush:
}
/*
- * Add a new flusher task that gets created for any bdi
- * that has dirty data pending writeout
+ * bdi_lock held on entry
*/
-static void bdi_add_default_flusher_task(struct backing_dev_info *bdi)
+static void bdi_add_one_flusher_task(struct backing_dev_info *bdi,
+ int(*func)(struct backing_dev_info *))
{
if (!bdi_cap_writeback_dirty(bdi))
return;
/*
- * Someone already marked this pending for task creation
+ * Check with the helper whether to proceed adding a task. Will only
+ * abort if we two or more simultanous calls to
+ * bdi_add_default_flusher_task() occured, further additions will block
+ * waiting for previous additions to finish.
*/
- if (test_and_set_bit(BDI_pending, &bdi->state))
- return;
+ if (!func(bdi)) {
+ list_move_tail(&bdi->bdi_list, &bdi_pending_list);
- spin_lock(&bdi_lock);
- list_move_tail(&bdi->bdi_list, &bdi_pending_list);
+ /*
+ * We are now on the pending list, wake up bdi_forker_task()
+ * to finish the job and add us back to the active bdi_list
+ */
+ wake_up_process(default_backing_dev_info.wb.task);
+ }
+}
+
+static int flusher_add_helper_block(struct backing_dev_info *bdi)
+{
spin_unlock(&bdi_lock);
+ wait_on_bit_lock(&bdi->state, BDI_pending, bdi_sched_wait,
+ TASK_UNINTERRUPTIBLE);
+ spin_lock(&bdi_lock);
+ return 0;
+}
+
+static int flusher_add_helper_test(struct backing_dev_info *bdi)
+{
+ return test_and_set_bit(BDI_pending, &bdi->state);
+}
- wake_up_process(default_backing_dev_info.wb.task);
+/*
+ * Add the default flusher task that gets created for any bdi
+ * that has dirty data pending writeout
+ */
+void static bdi_add_default_flusher_task(struct backing_dev_info *bdi)
+{
+ bdi_add_one_flusher_task(bdi, flusher_add_helper_test);
+}
+
+/**
+ * bdi_add_flusher_task - add one more flusher task to this @bdi
+ * @bdi: the bdi
+ *
+ * Add an additional flusher task to this @bdi. Will block waiting on
+ * previous additions, if any.
+ *
+ */
+void bdi_add_flusher_task(struct backing_dev_info *bdi)
+{
+ spin_lock(&bdi_lock);
+ bdi_add_one_flusher_task(bdi, flusher_add_helper_block);
+ spin_unlock(&bdi_lock);
}
+EXPORT_SYMBOL(bdi_add_flusher_task);
int bdi_register(struct backing_dev_info *bdi, struct device *parent,
const char *fmt, ...)
@@ -508,24 +658,21 @@ int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
}
EXPORT_SYMBOL(bdi_register_dev);
-static int sched_wait(void *word)
-{
- schedule();
- return 0;
-}
-
/*
* Remove bdi from the global list and shutdown any threads we have running
*/
static void bdi_wb_shutdown(struct backing_dev_info *bdi)
{
+ struct bdi_writeback *wb;
+
if (!bdi_cap_writeback_dirty(bdi))
return;
/*
* If setup is pending, wait for that to complete first
*/
- wait_on_bit(&bdi->state, BDI_pending, sched_wait, TASK_UNINTERRUPTIBLE);
+ wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
+ TASK_UNINTERRUPTIBLE);
/*
* Make sure nobody finds us on the bdi_list anymore
@@ -535,9 +682,11 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
spin_unlock(&bdi_lock);
/*
- * Finally, kill the kernel thread
+ * Finally, kill the kernel threads. We don't need to be RCU
+ * safe anymore, since the bdi is gone from visibility.
*/
- kthread_stop(bdi->wb.task);
+ list_for_each_entry(wb, &bdi->wb_list, list)
+ kthread_stop(wb->task);
}
void bdi_unregister(struct backing_dev_info *bdi)
@@ -561,8 +710,12 @@ int bdi_init(struct backing_dev_info *bdi)
bdi->min_ratio = 0;
bdi->max_ratio = 100;
bdi->max_prop_frac = PROP_FRAC_BASE;
+ spin_lock_init(&bdi->wb_lock);
+ bdi->wb_mask = 0;
+ bdi->wb_cnt = 0;
INIT_LIST_HEAD(&bdi->bdi_list);
- bdi->wb_mask = bdi->wb_active = 0;
+ INIT_LIST_HEAD(&bdi->wb_list);
+ INIT_LIST_HEAD(&bdi->work_list);
bdi_wb_init(&bdi->wb, bdi);
@@ -572,10 +725,15 @@ int bdi_init(struct backing_dev_info *bdi)
goto err;
}
+ err = init_srcu_struct(&bdi->srcu);
+ if (err)
+ goto err;
+
bdi->dirty_exceeded = 0;
err = prop_local_init_percpu(&bdi->completions);
if (err) {
+ cleanup_srcu_struct(&bdi->srcu);
err:
while (i--)
percpu_counter_destroy(&bdi->bdi_stat[i]);
@@ -593,6 +751,8 @@ void bdi_destroy(struct backing_dev_info *bdi)
bdi_unregister(bdi);
+ cleanup_srcu_struct(&bdi->srcu);
+
for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
percpu_counter_destroy(&bdi->bdi_stat[i]);
--
1.6.3.2.306.g4f4fa
^ permalink raw reply related [flat|nested] 30+ messages in thread* Re: [PATCH 5/9] writeback: support > 1 flusher thread per bdi
2009-07-30 21:24 ` [PATCH 5/9] writeback: support > 1 flusher thread per bdi Jens Axboe
@ 2009-08-05 19:55 ` Jan Kara
2009-08-06 7:05 ` Jens Axboe
2009-08-06 21:33 ` Christoph Hellwig
1 sibling, 1 reply; 30+ messages in thread
From: Jan Kara @ 2009-08-05 19:55 UTC (permalink / raw)
To: Jens Axboe
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm, jack,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Thu 30-07-09 23:24:00, Jens Axboe wrote:
> Build on the bdi_writeback support by allowing registration of
> more than 1 flusher thread. File systems can call bdi_add_flusher_task(bdi)
> to add more flusher threads to the device. If they do so, they must also
> provide a super_operations function to return the suitable bdi_writeback
> struct from any given inode.
>
> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
> ---
> fs/fs-writeback.c | 436 +++++++++++++++++++++++++++++++++++--------
> include/linux/backing-dev.h | 32 +++-
> include/linux/fs.h | 3 +
> include/linux/writeback.h | 1 +
> mm/backing-dev.c | 254 ++++++++++++++++++++-----
> 5 files changed, 593 insertions(+), 133 deletions(-)
>
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 86fb2a9..8069483 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -38,77 +38,230 @@ static void generic_sync_wb_inodes(struct bdi_writeback *wb,
> */
> int nr_pdflush_threads;
>
> -/**
> - * writeback_acquire - attempt to get exclusive writeback access to a device
> - * @bdi: the device's backing_dev_info structure
> - *
> - * It is a waste of resources to have more than one pdflush thread blocked on
> - * a single request queue. Exclusion at the request_queue level is obtained
> - * via a flag in the request_queue's backing_dev_info.state.
> - *
> - * Non-request_queue-backed address_spaces will share default_backing_dev_info,
> - * unless they implement their own. Which is somewhat inefficient, as this
> - * may prevent concurrent writeback against multiple devices.
> +static void generic_sync_wb_inodes(struct bdi_writeback *wb,
> + struct super_block *sb,
> + struct writeback_control *wbc);
> +
> +/*
> + * Work items for the bdi_writeback threads
> */
> -static int writeback_acquire(struct bdi_writeback *wb)
> +struct bdi_work {
> + struct list_head list;
> + struct list_head wait_list;
> + struct rcu_head rcu_head;
> +
> + unsigned long seen;
> + atomic_t pending;
> +
> + unsigned long sb_data;
> + unsigned long nr_pages;
> + enum writeback_sync_modes sync_mode;
> +
> + unsigned long state;
> +};
> +
> +static struct super_block *bdi_work_sb(struct bdi_work *work)
> {
> - struct backing_dev_info *bdi = wb->bdi;
> + return (struct super_block *) (work->sb_data & ~1UL);
> +}
> +
> +static inline bool bdi_work_on_stack(struct bdi_work *work)
> +{
> + return work->sb_data & 1UL;
> +}
> +
> +static inline void bdi_work_init(struct bdi_work *work, struct super_block *sb,
> + unsigned long nr_pages,
> + enum writeback_sync_modes sync_mode)
> +{
> + INIT_RCU_HEAD(&work->rcu_head);
> + work->sb_data = (unsigned long) sb;
> + work->nr_pages = nr_pages;
> + work->sync_mode = sync_mode;
> + work->state = 1;
> +}
>
> - return !test_and_set_bit(wb->nr, &bdi->wb_active);
> +static inline void bdi_work_init_on_stack(struct bdi_work *work,
> + struct super_block *sb,
> + unsigned long nr_pages,
> + enum writeback_sync_modes sync_mode)
> +{
> + bdi_work_init(work, sb, nr_pages, sync_mode);
> + work->sb_data |= 1UL;
> }
>
> /**
> * writeback_in_progress - determine whether there is writeback in progress
> * @bdi: the device's backing_dev_info structure.
> *
> - * Determine whether there is writeback in progress against a backing device.
> + * Determine whether there is writeback waiting to be handled against a
> + * backing device.
> */
> int writeback_in_progress(struct backing_dev_info *bdi)
> {
> - return bdi->wb_active != 0;
> + return !list_empty(&bdi->work_list);
> }
>
> -/**
> - * writeback_release - relinquish exclusive writeback access against a device.
> - * @bdi: the device's backing_dev_info structure
> - */
> -static void writeback_release(struct bdi_writeback *wb)
> +static void bdi_work_clear(struct bdi_work *work)
> {
> - struct backing_dev_info *bdi = wb->bdi;
> + clear_bit(0, &work->state);
> + smp_mb__after_clear_bit();
> + wake_up_bit(&work->state, 0);
> +}
> +
> +static void bdi_work_free(struct rcu_head *head)
> +{
> + struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
>
> - wb->nr_pages = 0;
> - wb->sb = NULL;
> - clear_bit(wb->nr, &bdi->wb_active);
> + if (!bdi_work_on_stack(work))
> + kfree(work);
> + else
> + bdi_work_clear(work);
> }
>
> -static void wb_start_writeback(struct bdi_writeback *wb, struct super_block *sb,
> - long nr_pages,
> - enum writeback_sync_modes sync_mode)
> +static void wb_work_complete(struct bdi_work *work)
> {
> - if (!wb_has_dirty_io(wb))
> - return;
> + const enum writeback_sync_modes sync_mode = work->sync_mode;
>
> - if (writeback_acquire(wb)) {
> - wb->nr_pages = nr_pages;
> - wb->sb = sb;
> - wb->sync_mode = sync_mode;
> + /*
> + * For allocated work, we can clear the done/seen bit right here.
> + * For on-stack work, we need to postpone both the clear and free
> + * to after the RCU grace period, since the stack could be invalidated
> + * as soon as bdi_work_clear() has done the wakeup.
> + */
> + if (!bdi_work_on_stack(work))
> + bdi_work_clear(work);
> + if (sync_mode == WB_SYNC_NONE || bdi_work_on_stack(work))
> + call_rcu(&work->rcu_head, bdi_work_free);
> +}
>
> - if (wb->task)
> - wake_up_process(wb->task);
> +static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
> +{
> + /*
> + * The caller has retrieved the work arguments from this work,
> + * drop our reference. If this is the last ref, delete and free it
> + */
> + if (atomic_dec_and_test(&work->pending)) {
> + struct backing_dev_info *bdi = wb->bdi;
> +
> + spin_lock(&bdi->wb_lock);
> + list_del_rcu(&work->list);
> + spin_unlock(&bdi->wb_lock);
> +
> + wb_work_complete(work);
> }
> }
>
> -void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
> - long nr_pages, enum writeback_sync_modes sync_mode)
> +static void wb_start_writeback(struct bdi_writeback *wb, struct bdi_work *work)
> +{
> + /*
> + * If we failed allocating the bdi work item, wake up the wb thread
> + * always. As a safety precaution, it'll flush out everything
> + */
> + if (!wb_has_dirty_io(wb) && work)
> + wb_clear_pending(wb, work);
> + else if (wb->task)
> + wake_up_process(wb->task);
> +}
> +
> +static void bdi_sched_work(struct backing_dev_info *bdi, struct bdi_work *work)
> {
> + if (!bdi_wblist_needs_lock(bdi))
> + wb_start_writeback(&bdi->wb, work);
> + else {
> + struct bdi_writeback *wb;
> + int idx;
> +
> + idx = srcu_read_lock(&bdi->srcu);
> +
> + list_for_each_entry_rcu(wb, &bdi->wb_list, list)
> + wb_start_writeback(wb, work);
> +
> + srcu_read_unlock(&bdi->srcu, idx);
> + }
> +}
> +
> +static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
> +{
> + if (work) {
> + work->seen = bdi->wb_mask;
> + BUG_ON(!work->seen);
> + atomic_set(&work->pending, bdi->wb_cnt);
I guess the idea here is that every writeback thread has to acknowledge
the work. But what if some thread decides to die after the work is queued
but before it manages to acknowledge it? We would end up waiting
indefinitely...
> + BUG_ON(!bdi->wb_cnt);
> +
> + /*
> + * Make sure stores are seen before it appears on the list
> + */
> + smp_mb();
> +
> + spin_lock(&bdi->wb_lock);
> + list_add_tail_rcu(&work->list, &bdi->work_list);
> + spin_unlock(&bdi->wb_lock);
> + }
> +
> /*
> - * This only happens the first time someone kicks this bdi, so put
> - * it out-of-line.
> + * If the default thread isn't there, make sure we add it. When
> + * it gets created and wakes up, we'll run this work.
> */
> - if (unlikely(!bdi->wb.task))
> + if (unlikely(list_empty_careful(&bdi->wb_list)))
> wake_up_process(default_backing_dev_info.wb.task);
> + else
> + bdi_sched_work(bdi, work);
> +}
> +
> +/*
> + * Used for on-stack allocated work items. The caller needs to wait until
> + * the wb threads have acked the work before it's safe to continue.
> + */
> +static void bdi_wait_on_work_clear(struct bdi_work *work)
> +{
> + wait_on_bit(&work->state, 0, bdi_sched_wait, TASK_UNINTERRUPTIBLE);
> +}
I still feel the rules for releasing / cleaning up work are too
complicated.
1) I believe we can bear one more "int" for flags in the struct bdi_work
so that you don't have to hide them in sb_data.
2) I'd introduce a flag with the meaning: free the work when you are
done. Obviusly this flag makes sence only with dynamically allocated work
structure. There would be no "on stack" flag.
3) I'd create a function:
bdi_wait_work_submitted()
which you'd have to call whenever you didn't set the flag and want to
free the work (either explicitely, or via returning from a function which
has the structure on stack).
It would do:
bdi_wait_on_work_clear(work);
call_rcu(&work->rcu_head, bdi_work_free);
wb_work_complete() would just depending on the flag setting either
completely do away with the work struct or just do bdi_work_clear().
IMO that would make the code easier to check and also less prone to
errors (currently you have to think twice when you have to wait for the rcu
period, call bdi_work_free, etc.).
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 30+ messages in thread* Re: [PATCH 5/9] writeback: support > 1 flusher thread per bdi
2009-08-05 19:55 ` Jan Kara
@ 2009-08-06 7:05 ` Jens Axboe
2009-08-06 20:56 ` Jan Kara
0 siblings, 1 reply; 30+ messages in thread
From: Jens Axboe @ 2009-08-06 7:05 UTC (permalink / raw)
To: Jan Kara
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Wed, Aug 05 2009, Jan Kara wrote:
> > +static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
> > +{
> > + if (work) {
> > + work->seen = bdi->wb_mask;
> > + BUG_ON(!work->seen);
> > + atomic_set(&work->pending, bdi->wb_cnt);
> I guess the idea here is that every writeback thread has to acknowledge
> the work. But what if some thread decides to die after the work is queued
> but before it manages to acknowledge it? We would end up waiting
> indefinitely...
The writeback thread checks for race added work on exit, so it should be
fine. Additionally, only the default thread will exit and that one will
always have it's count and mask be valid (since we auto-fork it again,
if needed).
>
> > + BUG_ON(!bdi->wb_cnt);
> > +
> > + /*
> > + * Make sure stores are seen before it appears on the list
> > + */
> > + smp_mb();
> > +
> > + spin_lock(&bdi->wb_lock);
> > + list_add_tail_rcu(&work->list, &bdi->work_list);
> > + spin_unlock(&bdi->wb_lock);
> > + }
> > +
> > /*
> > - * This only happens the first time someone kicks this bdi, so put
> > - * it out-of-line.
> > + * If the default thread isn't there, make sure we add it. When
> > + * it gets created and wakes up, we'll run this work.
> > */
> > - if (unlikely(!bdi->wb.task))
> > + if (unlikely(list_empty_careful(&bdi->wb_list)))
> > wake_up_process(default_backing_dev_info.wb.task);
> > + else
> > + bdi_sched_work(bdi, work);
> > +}
> > +
> > +/*
> > + * Used for on-stack allocated work items. The caller needs to wait until
> > + * the wb threads have acked the work before it's safe to continue.
> > + */
> > +static void bdi_wait_on_work_clear(struct bdi_work *work)
> > +{
> > + wait_on_bit(&work->state, 0, bdi_sched_wait, TASK_UNINTERRUPTIBLE);
> > +}
> I still feel the rules for releasing / cleaning up work are too
> complicated.
> 1) I believe we can bear one more "int" for flags in the struct bdi_work
> so that you don't have to hide them in sb_data.
Sure, but there's little reason to do that I think, since it's only used
internally. Let me put it another way, why add an extra int if we can
avoid it?
> 2) I'd introduce a flag with the meaning: free the work when you are
> done. Obviusly this flag makes sence only with dynamically allocated work
> structure. There would be no "on stack" flag.
> 3) I'd create a function:
> bdi_wait_work_submitted()
> which you'd have to call whenever you didn't set the flag and want to
> free the work (either explicitely, or via returning from a function which
> has the structure on stack).
> It would do:
> bdi_wait_on_work_clear(work);
> call_rcu(&work->rcu_head, bdi_work_free);
>
> wb_work_complete() would just depending on the flag setting either
> completely do away with the work struct or just do bdi_work_clear().
>
> IMO that would make the code easier to check and also less prone to
> errors (currently you have to think twice when you have to wait for the rcu
> period, call bdi_work_free, etc.).
Didn't we go over all that last time, too?
--
Jens Axboe
^ permalink raw reply [flat|nested] 30+ messages in thread* Re: [PATCH 5/9] writeback: support > 1 flusher thread per bdi
2009-08-06 7:05 ` Jens Axboe
@ 2009-08-06 20:56 ` Jan Kara
2009-08-24 11:43 ` Jens Axboe
0 siblings, 1 reply; 30+ messages in thread
From: Jan Kara @ 2009-08-06 20:56 UTC (permalink / raw)
To: Jens Axboe
Cc: Jan Kara, linux-kernel, linux-fsdevel, chris.mason, david, hch,
akpm, yanmin_zhang, richard, damien.wyart, fweisbec,
Alan.Brunelle
[-- Attachment #1: Type: text/plain, Size: 4423 bytes --]
On Thu 06-08-09 09:05:46, Jens Axboe wrote:
> On Wed, Aug 05 2009, Jan Kara wrote:
> > > +static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
> > > +{
> > > + if (work) {
> > > + work->seen = bdi->wb_mask;
> > > + BUG_ON(!work->seen);
> > > + atomic_set(&work->pending, bdi->wb_cnt);
> > I guess the idea here is that every writeback thread has to acknowledge
> > the work. But what if some thread decides to die after the work is queued
> > but before it manages to acknowledge it? We would end up waiting
> > indefinitely...
>
> The writeback thread checks for race added work on exit, so it should be
> fine.
Sorry if I'm a bit dense but I don't get it (hmm, probably I gave too few
details in my comment above). Assume there are at least two writeback
threads on bdi->wb_list:
CPU1 CPU2
bdi_writeback_task()
list_del_rcu(wb->list);
if (!list_empty(&bdi->work_list))
wb_do_writeback(wb, 1);
bdi_queue_work()
...
atomic_set(&work->pending, bdi->wb_cnt);
...
bdi->wb_list isn't empty
bdi_sched_work()
bdi_put_wb(bdi, wb); -> only now the bdi->wb_cnt is decreased...
Looking at the code more in detail, it actually gets fixed once the
forker task wakes up, notices there's some work to do and adds the default
flusher thread again but still it could have strange effects.
> Additionally, only the default thread will exit and that one will
> always have it's count and mask be valid (since we auto-fork it again,
> if needed).
Ah OK, I see.
> > > + BUG_ON(!bdi->wb_cnt);
> > > +
> > > + /*
> > > + * Make sure stores are seen before it appears on the list
> > > + */
> > > + smp_mb();
> > > +
> > > + spin_lock(&bdi->wb_lock);
> > > + list_add_tail_rcu(&work->list, &bdi->work_list);
> > > + spin_unlock(&bdi->wb_lock);
> > > + }
> > > +
> > > /*
> > > - * This only happens the first time someone kicks this bdi, so put
> > > - * it out-of-line.
> > > + * If the default thread isn't there, make sure we add it. When
> > > + * it gets created and wakes up, we'll run this work.
> > > */
> > > - if (unlikely(!bdi->wb.task))
> > > + if (unlikely(list_empty_careful(&bdi->wb_list)))
> > > wake_up_process(default_backing_dev_info.wb.task);
> > > + else
> > > + bdi_sched_work(bdi, work);
> > > +}
> > > +
> > > +/*
> > > + * Used for on-stack allocated work items. The caller needs to wait until
> > > + * the wb threads have acked the work before it's safe to continue.
> > > + */
> > > +static void bdi_wait_on_work_clear(struct bdi_work *work)
> > > +{
> > > + wait_on_bit(&work->state, 0, bdi_sched_wait, TASK_UNINTERRUPTIBLE);
> > > +}
> > I still feel the rules for releasing / cleaning up work are too
> > complicated.
> > 1) I believe we can bear one more "int" for flags in the struct bdi_work
> > so that you don't have to hide them in sb_data.
>
> Sure, but there's little reason to do that I think, since it's only used
> internally. Let me put it another way, why add an extra int if we can
> avoid it?
Actually, looking again that the work struct "state" field has lots of
free bits. I think the code looks nicer with the attached patch, what do
you think?
> > 2) I'd introduce a flag with the meaning: free the work when you are
> > done. Obviusly this flag makes sence only with dynamically allocated work
> > structure. There would be no "on stack" flag.
> > 3) I'd create a function:
> > bdi_wait_work_submitted()
> > which you'd have to call whenever you didn't set the flag and want to
> > free the work (either explicitely, or via returning from a function which
> > has the structure on stack).
> > It would do:
> > bdi_wait_on_work_clear(work);
> > call_rcu(&work->rcu_head, bdi_work_free);
> >
> > wb_work_complete() would just depending on the flag setting either
> > completely do away with the work struct or just do bdi_work_clear().
> >
> > IMO that would make the code easier to check and also less prone to
> > errors (currently you have to think twice when you have to wait for the rcu
> > period, call bdi_work_free, etc.).
>
> Didn't we go over all that last time, too?
Well, probably about something similar. But this time I have a patch ;-)
Compile tested only... IMO it looks nicer this way as it wraps up all the
details of work freeing into one function.
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
[-- Attachment #2: 0001-Cleanup-flags-handling-in-per-bdi-flusher-threads-pa.patch --]
[-- Type: text/x-patch, Size: 3261 bytes --]
>From 4a8615747d96efc5067932936c1330e17edfbd16 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 6 Aug 2009 21:35:30 +0200
Subject: [PATCH 1/2] Cleanup flags handling in per-bdi flusher threads patches.
Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/fs-writeback.c | 31 +++++++++++++++++--------------
1 files changed, 17 insertions(+), 14 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index dfb4767..fc7e4a3 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -53,21 +53,24 @@ struct bdi_work {
unsigned long seen;
atomic_t pending;
- unsigned long sb_data;
+ struct super_block *sb;
unsigned long nr_pages;
enum writeback_sync_modes sync_mode;
unsigned long state;
};
-static struct super_block *bdi_work_sb(struct bdi_work *work)
-{
- return (struct super_block *) (work->sb_data & ~1UL);
-}
+enum {
+ WS_USED_B = 0,
+ WS_ONSTACK_B,
+};
+
+#define WS_USED (1 << WS_USED_B)
+#define WS_ONSTACK (1 << WS_ONSTACK_B)
static inline bool bdi_work_on_stack(struct bdi_work *work)
{
- return work->sb_data & 1UL;
+ return test_bit(WS_ONSTACK_B, &work->state);
}
static inline void bdi_work_init(struct bdi_work *work, struct super_block *sb,
@@ -75,10 +78,10 @@ static inline void bdi_work_init(struct bdi_work *work, struct super_block *sb,
enum writeback_sync_modes sync_mode)
{
INIT_RCU_HEAD(&work->rcu_head);
- work->sb_data = (unsigned long) sb;
+ work->sb = sb;
work->nr_pages = nr_pages;
work->sync_mode = sync_mode;
- work->state = 1;
+ work->state = WS_USED;
}
static inline void bdi_work_init_on_stack(struct bdi_work *work,
@@ -87,7 +90,7 @@ static inline void bdi_work_init_on_stack(struct bdi_work *work,
enum writeback_sync_modes sync_mode)
{
bdi_work_init(work, sb, nr_pages, sync_mode);
- work->sb_data |= 1UL;
+ work->state |= WS_ONSTACK;
}
/**
@@ -104,9 +107,9 @@ int writeback_in_progress(struct backing_dev_info *bdi)
static void bdi_work_clear(struct bdi_work *work)
{
- clear_bit(0, &work->state);
+ clear_bit(WS_USED_B, &work->state);
smp_mb__after_clear_bit();
- wake_up_bit(&work->state, 0);
+ wake_up_bit(&work->state, WS_USED_B);
}
static void bdi_work_free(struct rcu_head *head)
@@ -215,7 +218,8 @@ static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
*/
static void bdi_wait_on_work_clear(struct bdi_work *work)
{
- wait_on_bit(&work->state, 0, bdi_sched_wait, TASK_UNINTERRUPTIBLE);
+ wait_on_bit(&work->state, WS_USED_B, bdi_sched_wait,
+ TASK_UNINTERRUPTIBLE);
}
static struct bdi_work *bdi_alloc_work(struct super_block *sb, long nr_pages,
@@ -376,7 +380,6 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
long nr_pages, wrote = 0;
while ((work = get_next_work_item(bdi, wb)) != NULL) {
- struct super_block *sb = bdi_work_sb(work);
enum writeback_sync_modes sync_mode;
nr_pages = work->nr_pages;
@@ -396,7 +399,7 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
if (sync_mode == WB_SYNC_NONE)
wb_clear_pending(wb, work);
- wrote += wb_writeback(wb, nr_pages, sb, sync_mode, 0);
+ wrote += wb_writeback(wb, nr_pages, work->sb, sync_mode, 0);
/*
* This is a data integrity writeback, so only do the
--
1.6.0.2
[-- Attachment #3: 0002-Cleanup-freeing-of-work-struct.patch --]
[-- Type: text/x-patch, Size: 6366 bytes --]
>From 54366b186d1e50b3453dfd2881a7eae559ab6cbc Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Thu, 6 Aug 2009 22:24:57 +0200
Subject: [PATCH 2/2] Cleanup freeing of work struct
Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/fs-writeback.c | 121 ++++++++++++++++++++++++++++++----------------------
1 files changed, 70 insertions(+), 51 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index fc7e4a3..bdc8dd5 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -61,16 +61,35 @@ struct bdi_work {
};
enum {
- WS_USED_B = 0,
- WS_ONSTACK_B,
+ WS_USED_B = 0, /* Still processed by the writeback thread */
+ WS_ALLOCATED_B, /* Work is dynamically allocated */
+ WS_ASYNC_B, /* Should be freed by the writeback thread */
};
#define WS_USED (1 << WS_USED_B)
-#define WS_ONSTACK (1 << WS_ONSTACK_B)
+#define WS_ALLOCATED (1 << WS_ALLOCATED_B)
+#define WS_ASYNC (1 << WS_ASYNC_B)
-static inline bool bdi_work_on_stack(struct bdi_work *work)
+static inline bool bdi_work_async(struct bdi_work *work)
{
- return test_bit(WS_ONSTACK_B, &work->state);
+
+ return test_bit(WS_ASYNC_B, &work->state);
+}
+
+static inline bool bdi_work_allocated(struct bdi_work *work)
+{
+ return test_bit(WS_ALLOCATED_B, &work->state);
+}
+
+static inline void bdi_set_work_async(struct bdi_work *work)
+{
+ WARN_ON(!bdi_work_allocated(work));
+ set_bit(WS_ASYNC_B, &work->state);
+}
+
+static inline void bdi_set_work_allocated(struct bdi_work *work)
+{
+ set_bit(WS_ALLOCATED_B, &work->state);
}
static inline void bdi_work_init(struct bdi_work *work, struct super_block *sb,
@@ -84,15 +103,6 @@ static inline void bdi_work_init(struct bdi_work *work, struct super_block *sb,
work->state = WS_USED;
}
-static inline void bdi_work_init_on_stack(struct bdi_work *work,
- struct super_block *sb,
- unsigned long nr_pages,
- enum writeback_sync_modes sync_mode)
-{
- bdi_work_init(work, sb, nr_pages, sync_mode);
- work->state |= WS_ONSTACK;
-}
-
/**
* writeback_in_progress - determine whether there is writeback in progress
* @bdi: the device's backing_dev_info structure.
@@ -116,26 +126,19 @@ static void bdi_work_free(struct rcu_head *head)
{
struct bdi_work *work = container_of(head, struct bdi_work, rcu_head);
- if (!bdi_work_on_stack(work))
- kfree(work);
- else
- bdi_work_clear(work);
+ kfree(work);
}
static void wb_work_complete(struct bdi_work *work)
{
- const enum writeback_sync_modes sync_mode = work->sync_mode;
-
/*
- * For allocated work, we can clear the done/seen bit right here.
- * For on-stack work, we need to postpone both the clear and free
- * to after the RCU grace period, since the stack could be invalidated
- * as soon as bdi_work_clear() has done the wakeup.
+ * Either free the work if it is ASYNC one (and thus nobody
+ * should wait on it) or mark it as done.
*/
- if (!bdi_work_on_stack(work))
- bdi_work_clear(work);
- if (sync_mode == WB_SYNC_NONE || bdi_work_on_stack(work))
+ if (bdi_work_async(work))
call_rcu(&work->rcu_head, bdi_work_free);
+ else
+ bdi_work_clear(work);
}
static void wb_clear_pending(struct bdi_writeback *wb, struct bdi_work *work)
@@ -213,8 +216,9 @@ static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
}
/*
- * Used for on-stack allocated work items. The caller needs to wait until
- * the wb threads have acked the work before it's safe to continue.
+ * Wait until the writeback thread is done with the work. For WB_SYNC_NONE
+ * work, it is the moment the thread has copied the contents of the structure,
+ * for WB_SYNC_ALL work, it is the moment the thread has submitted all the IO.
*/
static void bdi_wait_on_work_clear(struct bdi_work *work)
{
@@ -228,44 +232,58 @@ static struct bdi_work *bdi_alloc_work(struct super_block *sb, long nr_pages,
struct bdi_work *work;
work = kmalloc(sizeof(*work), GFP_ATOMIC);
- if (work)
+ if (work) {
bdi_work_init(work, sb, nr_pages, sync_mode);
+ bdi_set_work_allocated(work);
+ }
return work;
}
+/*
+ * Wait until the work is safe to be freed and free it.
+ *
+ * Note that for WB_SYNC_ALL work, this waits until all the IO is submitted
+ */
+static void bdi_wait_free_work(struct bdi_work *work)
+{
+ if (!bdi_work_async(work)) {
+ bdi_wait_on_work_clear(work);
+ if (bdi_work_allocated(work))
+ call_rcu(&work->rcu_head, bdi_work_free);
+ else {
+ /*
+ * For on-stack work, we have to wait as the structure
+ * on stack can be freed as soon as we return.
+ */
+ synchronize_rcu();
+ }
+ }
+}
+
void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
long nr_pages, enum writeback_sync_modes sync_mode)
{
const bool must_wait = sync_mode == WB_SYNC_ALL;
struct bdi_work work_stack, *work = NULL;
- if (!must_wait)
+ if (!must_wait) {
work = bdi_alloc_work(sb, nr_pages, sync_mode);
+ /*
+ * Mark that we don't want to wait on work and the writeback
+ * thread can free it.
+ */
+ if (work)
+ bdi_set_work_async(work);
+ }
if (!work) {
work = &work_stack;
- bdi_work_init_on_stack(work, sb, nr_pages, sync_mode);
+ bdi_work_init(work, sb, nr_pages, sync_mode);
}
bdi_queue_work(bdi, work);
-
- /*
- * If the sync mode is WB_SYNC_ALL, block waiting for the work to
- * complete. If not, we only need to wait for the work to be started,
- * if we allocated it on-stack. We use the same mechanism, if the
- * wait bit is set in the bdi_work struct, then threads will not
- * clear pending until after they are done.
- *
- * Note that work == &work_stack if must_wait is true, so we don't
- * need to do call_rcu() here ever, since the completion path will
- * have done that for us.
- */
- if (must_wait || work == &work_stack) {
- bdi_wait_on_work_clear(work);
- if (work != &work_stack)
- call_rcu(&work->rcu_head, bdi_work_free);
- }
+ bdi_wait_free_work(work);
}
/*
@@ -507,6 +525,8 @@ restart:
}
if (must_wait)
list_add_tail(&work->wait_list, &list);
+ else
+ bdi_set_work_async(work);
bdi_queue_work(bdi, work);
}
@@ -520,8 +540,7 @@ restart:
while (!list_empty(&list)) {
work = list_entry(list.next, struct bdi_work, wait_list);
list_del(&work->wait_list);
- bdi_wait_on_work_clear(work);
- call_rcu(&work->rcu_head, bdi_work_free);
+ bdi_wait_free_work(work);
}
}
--
1.6.0.2
^ permalink raw reply related [flat|nested] 30+ messages in thread* Re: [PATCH 5/9] writeback: support > 1 flusher thread per bdi
2009-08-06 20:56 ` Jan Kara
@ 2009-08-24 11:43 ` Jens Axboe
2009-08-24 12:36 ` Jan Kara
0 siblings, 1 reply; 30+ messages in thread
From: Jens Axboe @ 2009-08-24 11:43 UTC (permalink / raw)
To: Jan Kara
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Thu, Aug 06 2009, Jan Kara wrote:
> Actually, looking again that the work struct "state" field has lots of
> free bits. I think the code looks nicer with the attached patch, what do
> you think?
>
> > > 2) I'd introduce a flag with the meaning: free the work when you are
> > > done. Obviusly this flag makes sence only with dynamically allocated work
> > > structure. There would be no "on stack" flag.
> > > 3) I'd create a function:
> > > bdi_wait_work_submitted()
> > > which you'd have to call whenever you didn't set the flag and want to
> > > free the work (either explicitely, or via returning from a function which
> > > has the structure on stack).
> > > It would do:
> > > bdi_wait_on_work_clear(work);
> > > call_rcu(&work->rcu_head, bdi_work_free);
> > >
> > > wb_work_complete() would just depending on the flag setting either
> > > completely do away with the work struct or just do bdi_work_clear().
> > >
> > > IMO that would make the code easier to check and also less prone to
> > > errors (currently you have to think twice when you have to wait for the rcu
> > > period, call bdi_work_free, etc.).
> >
> > Didn't we go over all that last time, too?
> Well, probably about something similar. But this time I have a patch ;-)
> Compile tested only... IMO it looks nicer this way as it wraps up all the
> details of work freeing into one function.
The first patch looks nice and obvious, I'll fold that in with the
original patch if you don't mind. It's definitely cleaner, instead of
overloading the pointer.
The second one I'd rather hold off on, I've run over the existing code
many times and tested it heavily threaded and know it's safe. So I'd
rather not introduce any drastic changes there so close to 2.6.32, but
I'd be happy to revisit this soon after merge. OK?
--
Jens Axboe
^ permalink raw reply [flat|nested] 30+ messages in thread
* Re: [PATCH 5/9] writeback: support > 1 flusher thread per bdi
2009-08-24 11:43 ` Jens Axboe
@ 2009-08-24 12:36 ` Jan Kara
2009-08-24 14:09 ` Jens Axboe
0 siblings, 1 reply; 30+ messages in thread
From: Jan Kara @ 2009-08-24 12:36 UTC (permalink / raw)
To: Jens Axboe
Cc: Jan Kara, linux-kernel, linux-fsdevel, chris.mason, david, hch,
akpm, yanmin_zhang, richard, damien.wyart, fweisbec,
Alan.Brunelle
On Mon 24-08-09 13:43:26, Jens Axboe wrote:
> On Thu, Aug 06 2009, Jan Kara wrote:
> > Actually, looking again that the work struct "state" field has lots of
> > free bits. I think the code looks nicer with the attached patch, what do
> > you think?
> >
> > > > 2) I'd introduce a flag with the meaning: free the work when you are
> > > > done. Obviusly this flag makes sence only with dynamically allocated work
> > > > structure. There would be no "on stack" flag.
> > > > 3) I'd create a function:
> > > > bdi_wait_work_submitted()
> > > > which you'd have to call whenever you didn't set the flag and want to
> > > > free the work (either explicitely, or via returning from a function which
> > > > has the structure on stack).
> > > > It would do:
> > > > bdi_wait_on_work_clear(work);
> > > > call_rcu(&work->rcu_head, bdi_work_free);
> > > >
> > > > wb_work_complete() would just depending on the flag setting either
> > > > completely do away with the work struct or just do bdi_work_clear().
> > > >
> > > > IMO that would make the code easier to check and also less prone to
> > > > errors (currently you have to think twice when you have to wait for the rcu
> > > > period, call bdi_work_free, etc.).
> > >
> > > Didn't we go over all that last time, too?
> > Well, probably about something similar. But this time I have a patch ;-)
> > Compile tested only... IMO it looks nicer this way as it wraps up all the
> > details of work freeing into one function.
>
> The first patch looks nice and obvious, I'll fold that in with the
> original patch if you don't mind. It's definitely cleaner, instead of
> overloading the pointer.
Yes, that's fine.
> The second one I'd rather hold off on, I've run over the existing code
> many times and tested it heavily threaded and know it's safe. So I'd
> rather not introduce any drastic changes there so close to 2.6.32, but
> I'd be happy to revisit this soon after merge. OK?
Fine with me, I'm just not sure about the merging in 2.6.32 - the
umount_sem and sb->s_count problems (http://lkml.org/lkml/2009/8/5/322 -
BTW I didn't see a response from you) should get sorted out before the
merge. To be honest, I'm not much in favor of merging your patches before
having resolved that and I think Christoph Hellwig or Al Viro will express
their opinion even more strongly ;).
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 30+ messages in thread
* Re: [PATCH 5/9] writeback: support > 1 flusher thread per bdi
2009-08-24 12:36 ` Jan Kara
@ 2009-08-24 14:09 ` Jens Axboe
0 siblings, 0 replies; 30+ messages in thread
From: Jens Axboe @ 2009-08-24 14:09 UTC (permalink / raw)
To: Jan Kara
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Mon, Aug 24 2009, Jan Kara wrote:
> On Mon 24-08-09 13:43:26, Jens Axboe wrote:
> > On Thu, Aug 06 2009, Jan Kara wrote:
> > > Actually, looking again that the work struct "state" field has lots of
> > > free bits. I think the code looks nicer with the attached patch, what do
> > > you think?
> > >
> > > > > 2) I'd introduce a flag with the meaning: free the work when you are
> > > > > done. Obviusly this flag makes sence only with dynamically allocated work
> > > > > structure. There would be no "on stack" flag.
> > > > > 3) I'd create a function:
> > > > > bdi_wait_work_submitted()
> > > > > which you'd have to call whenever you didn't set the flag and want to
> > > > > free the work (either explicitely, or via returning from a function which
> > > > > has the structure on stack).
> > > > > It would do:
> > > > > bdi_wait_on_work_clear(work);
> > > > > call_rcu(&work->rcu_head, bdi_work_free);
> > > > >
> > > > > wb_work_complete() would just depending on the flag setting either
> > > > > completely do away with the work struct or just do bdi_work_clear().
> > > > >
> > > > > IMO that would make the code easier to check and also less prone to
> > > > > errors (currently you have to think twice when you have to wait for the rcu
> > > > > period, call bdi_work_free, etc.).
> > > >
> > > > Didn't we go over all that last time, too?
> > > Well, probably about something similar. But this time I have a patch ;-)
> > > Compile tested only... IMO it looks nicer this way as it wraps up all the
> > > details of work freeing into one function.
> >
> > The first patch looks nice and obvious, I'll fold that in with the
> > original patch if you don't mind. It's definitely cleaner, instead of
> > overloading the pointer.
> Yes, that's fine.
>
> > The second one I'd rather hold off on, I've run over the existing code
> > many times and tested it heavily threaded and know it's safe. So I'd
> > rather not introduce any drastic changes there so close to 2.6.32, but
> > I'd be happy to revisit this soon after merge. OK?
> Fine with me, I'm just not sure about the merging in 2.6.32 - the
> umount_sem and sb->s_count problems (http://lkml.org/lkml/2009/8/5/322 -
> BTW I didn't see a response from you) should get sorted out before the
> merge. To be honest, I'm not much in favor of merging your patches before
> having resolved that and I think Christoph Hellwig or Al Viro will express
> their opinion even more strongly ;).
I don't plan to merge it before we have that sorted, don't worry. I'll
be posting it soon here again!
--
Jens Axboe
^ permalink raw reply [flat|nested] 30+ messages in thread
* Re: [PATCH 5/9] writeback: support > 1 flusher thread per bdi
2009-07-30 21:24 ` [PATCH 5/9] writeback: support > 1 flusher thread per bdi Jens Axboe
2009-08-05 19:55 ` Jan Kara
@ 2009-08-06 21:33 ` Christoph Hellwig
1 sibling, 0 replies; 30+ messages in thread
From: Christoph Hellwig @ 2009-08-06 21:33 UTC (permalink / raw)
To: Jens Axboe
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm, jack,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Thu, Jul 30, 2009 at 11:24:00PM +0200, Jens Axboe wrote:
> Build on the bdi_writeback support by allowing registration of
> more than 1 flusher thread. File systems can call bdi_add_flusher_task(bdi)
> to add more flusher threads to the device. If they do so, they must also
> provide a super_operations function to return the suitable bdi_writeback
> struct from any given inode.
Please don't add a inode_get_wb method until we actually have users for it.
^ permalink raw reply [flat|nested] 30+ messages in thread
* [PATCH 6/9] writeback: allow sleepy exit of default writeback task
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
` (4 preceding siblings ...)
2009-07-30 21:24 ` [PATCH 5/9] writeback: support > 1 flusher thread per bdi Jens Axboe
@ 2009-07-30 21:24 ` Jens Axboe
2009-08-05 19:57 ` Jan Kara
2009-07-30 21:24 ` [PATCH 7/9] writeback: add some debug inode list counters to bdi stats Jens Axboe
` (3 subsequent siblings)
9 siblings, 1 reply; 30+ messages in thread
From: Jens Axboe @ 2009-07-30 21:24 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: chris.mason, david, hch, akpm, jack, yanmin_zhang, richard,
damien.wyart, fweisbec, Alan.Brunelle, Jens Axboe
Since we do lazy create of default writeback tasks for a bdi, we can
allow sleepy exit if it has been completely idle for 5 minutes.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
fs/fs-writeback.c | 30 +++++++++++++++++++++++++-----
include/linux/backing-dev.h | 5 +++++
include/linux/writeback.h | 2 +-
3 files changed, 31 insertions(+), 6 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 8069483..796b243 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -369,7 +369,7 @@ static struct bdi_work *get_next_work_item(struct backing_dev_info *bdi,
/*
* Retrieve work items and do the writeback they describe
*/
-void wb_do_writeback(struct bdi_writeback *wb, int force_wait)
+long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
{
struct backing_dev_info *bdi = wb->bdi;
struct bdi_work *work;
@@ -414,8 +414,10 @@ void wb_do_writeback(struct bdi_writeback *wb, int force_wait)
global_page_state(NR_UNSTABLE_NFS) +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
- wb_writeback(wb, nr_pages, NULL, WB_SYNC_NONE, 1);
+ wrote = wb_writeback(wb, nr_pages, NULL, WB_SYNC_NONE, 1);
}
+
+ return wrote;
}
/*
@@ -424,10 +426,28 @@ void wb_do_writeback(struct bdi_writeback *wb, int force_wait)
*/
int bdi_writeback_task(struct bdi_writeback *wb)
{
+ unsigned long last_active = jiffies;
+ unsigned long wait_jiffies = -1UL;
+ long pages_written;
+
while (!kthread_should_stop()) {
- unsigned long wait_jiffies;
+ pages_written = wb_do_writeback(wb, 0);
+
+ if (pages_written)
+ last_active = jiffies;
+ else if (wait_jiffies != -1UL) {
+ unsigned long max_idle;
- wb_do_writeback(wb, 0);
+ /*
+ * Longest period of inactivity that we tolerate. If we
+ * see dirty data again later, the task will get
+ * recreated automatically.
+ */
+ max_idle = max(5UL * 60 * HZ, wait_jiffies);
+ if (time_after(jiffies, max_idle + last_active) &&
+ wb_is_default_task(wb))
+ break;
+ }
wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
set_current_state(TASK_INTERRUPTIBLE);
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 90a1910..7a23f2f 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -110,6 +110,11 @@ int bdi_has_dirty_io(struct backing_dev_info *bdi);
extern spinlock_t bdi_lock;
extern struct list_head bdi_list;
+static inline int wb_is_default_task(struct bdi_writeback *wb)
+{
+ return wb == &wb->bdi->wb;
+}
+
static inline int bdi_wblist_needs_lock(struct backing_dev_info *bdi)
{
return test_bit(BDI_wblist_lock, &bdi->state);
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 588a449..e070b91 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -68,7 +68,7 @@ struct writeback_control {
void writeback_inodes(struct writeback_control *wbc);
int inode_wait(void *);
void sync_inodes_sb(struct super_block *, int wait);
-void wb_do_writeback(struct bdi_writeback *wb, int force_wait);
+long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
/* writeback.h requires fs.h; it, too, is not included from here. */
static inline void wait_on_inode(struct inode *inode)
--
1.6.3.2.306.g4f4fa
^ permalink raw reply related [flat|nested] 30+ messages in thread* Re: [PATCH 6/9] writeback: allow sleepy exit of default writeback task
2009-07-30 21:24 ` [PATCH 6/9] writeback: allow sleepy exit of default writeback task Jens Axboe
@ 2009-08-05 19:57 ` Jan Kara
2009-08-06 7:03 ` Jens Axboe
0 siblings, 1 reply; 30+ messages in thread
From: Jan Kara @ 2009-08-05 19:57 UTC (permalink / raw)
To: Jens Axboe
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm, jack,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Thu 30-07-09 23:24:01, Jens Axboe wrote:
> Since we do lazy create of default writeback tasks for a bdi, we can
> allow sleepy exit if it has been completely idle for 5 minutes.
Maybe there should be a sysfs tunable to this?
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 30+ messages in thread
* Re: [PATCH 6/9] writeback: allow sleepy exit of default writeback task
2009-08-05 19:57 ` Jan Kara
@ 2009-08-06 7:03 ` Jens Axboe
2009-08-06 18:55 ` Jan Kara
0 siblings, 1 reply; 30+ messages in thread
From: Jens Axboe @ 2009-08-06 7:03 UTC (permalink / raw)
To: Jan Kara
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm,
yanmin_zhang, richard, damien.wyart, fweisbec, Alan.Brunelle
On Wed, Aug 05 2009, Jan Kara wrote:
> On Thu 30-07-09 23:24:01, Jens Axboe wrote:
> > Since we do lazy create of default writeback tasks for a bdi, we can
> > allow sleepy exit if it has been completely idle for 5 minutes.
> Maybe there should be a sysfs tunable to this?
Not sure, and when in doubt I prefer not to do that. But we could easily
add one, if people think it will be useful. What would the reason for
turning it off be?
--
Jens Axboe
^ permalink raw reply [flat|nested] 30+ messages in thread
* Re: [PATCH 6/9] writeback: allow sleepy exit of default writeback task
2009-08-06 7:03 ` Jens Axboe
@ 2009-08-06 18:55 ` Jan Kara
0 siblings, 0 replies; 30+ messages in thread
From: Jan Kara @ 2009-08-06 18:55 UTC (permalink / raw)
To: Jens Axboe
Cc: Jan Kara, linux-kernel, linux-fsdevel, chris.mason, david, hch,
akpm, yanmin_zhang, richard, damien.wyart, fweisbec,
Alan.Brunelle
On Thu 06-08-09 09:03:26, Jens Axboe wrote:
> On Wed, Aug 05 2009, Jan Kara wrote:
> > On Thu 30-07-09 23:24:01, Jens Axboe wrote:
> > > Since we do lazy create of default writeback tasks for a bdi, we can
> > > allow sleepy exit if it has been completely idle for 5 minutes.
> > Maybe there should be a sysfs tunable to this?
>
> Not sure, and when in doubt I prefer not to do that. But we could easily
> add one, if people think it will be useful. What would the reason for
> turning it off be?
Well, I thought it might be useful mainly for debugging purposes, e.g. if
you want to watch the writeback thread and don't want it to be restarted
(as that changes it's pid etc.). I don't have a strong opinion on this, it
was just an idea.
Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 30+ messages in thread
* [PATCH 7/9] writeback: add some debug inode list counters to bdi stats
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
` (5 preceding siblings ...)
2009-07-30 21:24 ` [PATCH 6/9] writeback: allow sleepy exit of default writeback task Jens Axboe
@ 2009-07-30 21:24 ` Jens Axboe
2009-07-30 21:24 ` [PATCH 8/9] writeback: add name to backing_dev_info Jens Axboe
` (2 subsequent siblings)
9 siblings, 0 replies; 30+ messages in thread
From: Jens Axboe @ 2009-07-30 21:24 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: chris.mason, david, hch, akpm, jack, yanmin_zhang, richard,
damien.wyart, fweisbec, Alan.Brunelle, Jens Axboe
Add some debug entries to be able to inspect the internal state of
the writeback details.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
mm/backing-dev.c | 38 ++++++++++++++++++++++++++++++++++----
1 files changed, 34 insertions(+), 4 deletions(-)
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 45dfe51..dbaf866 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -52,9 +52,29 @@ static void bdi_debug_init(void)
static int bdi_debug_stats_show(struct seq_file *m, void *v)
{
struct backing_dev_info *bdi = m->private;
+ struct bdi_writeback *wb;
unsigned long background_thresh;
unsigned long dirty_thresh;
unsigned long bdi_thresh;
+ unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
+ struct inode *inode;
+
+ /*
+ * inode lock is enough here, the bdi->wb_list is protected by
+ * RCU on the reader side
+ */
+ nr_wb = nr_dirty = nr_io = nr_more_io = 0;
+ spin_lock(&inode_lock);
+ list_for_each_entry(wb, &bdi->wb_list, list) {
+ nr_wb++;
+ list_for_each_entry(inode, &wb->b_dirty, i_list)
+ nr_dirty++;
+ list_for_each_entry(inode, &wb->b_io, i_list)
+ nr_io++;
+ list_for_each_entry(inode, &wb->b_more_io, i_list)
+ nr_more_io++;
+ }
+ spin_unlock(&inode_lock);
get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
@@ -64,12 +84,22 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
"BdiReclaimable: %8lu kB\n"
"BdiDirtyThresh: %8lu kB\n"
"DirtyThresh: %8lu kB\n"
- "BackgroundThresh: %8lu kB\n",
+ "BackgroundThresh: %8lu kB\n"
+ "WriteBack threads:%8lu\n"
+ "b_dirty: %8lu\n"
+ "b_io: %8lu\n"
+ "b_more_io: %8lu\n"
+ "bdi_list: %8u\n"
+ "state: %8lx\n"
+ "wb_mask: %8lx\n"
+ "wb_list: %8u\n"
+ "wb_cnt: %8u\n",
(unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
(unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
- K(bdi_thresh),
- K(dirty_thresh),
- K(background_thresh));
+ K(bdi_thresh), K(dirty_thresh),
+ K(background_thresh), nr_wb, nr_dirty, nr_io, nr_more_io,
+ !list_empty(&bdi->bdi_list), bdi->state, bdi->wb_mask,
+ !list_empty(&bdi->wb_list), bdi->wb_cnt);
#undef K
return 0;
--
1.6.3.2.306.g4f4fa
^ permalink raw reply related [flat|nested] 30+ messages in thread* [PATCH 8/9] writeback: add name to backing_dev_info
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
` (6 preceding siblings ...)
2009-07-30 21:24 ` [PATCH 7/9] writeback: add some debug inode list counters to bdi stats Jens Axboe
@ 2009-07-30 21:24 ` Jens Axboe
2009-07-30 21:24 ` [PATCH 9/9] writeback: check for registered bdi in flusher add and inode dirty Jens Axboe
2009-07-31 6:30 ` [PATCH 0/9] Per-bdi writeback flusher threads v13 Damien Wyart
9 siblings, 0 replies; 30+ messages in thread
From: Jens Axboe @ 2009-07-30 21:24 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: chris.mason, david, hch, akpm, jack, yanmin_zhang, richard,
damien.wyart, fweisbec, Alan.Brunelle, Jens Axboe
This enables us to track who does what and print info. Its main use
is catching dirty inodes on the default_backing_dev_info, so we can
fix that up.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
block/blk-core.c | 1 +
drivers/block/aoe/aoeblk.c | 1 +
drivers/char/mem.c | 1 +
fs/btrfs/disk-io.c | 1 +
fs/char_dev.c | 1 +
fs/configfs/inode.c | 1 +
fs/fuse/inode.c | 1 +
fs/hugetlbfs/inode.c | 1 +
fs/nfs/client.c | 1 +
fs/ocfs2/dlm/dlmfs.c | 1 +
fs/ramfs/inode.c | 1 +
fs/sysfs/inode.c | 1 +
fs/ubifs/super.c | 1 +
include/linux/backing-dev.h | 2 ++
kernel/cgroup.c | 1 +
mm/backing-dev.c | 1 +
mm/swap_state.c | 1 +
17 files changed, 18 insertions(+), 0 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 4b45435..8f4b9e0 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -501,6 +501,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
q->backing_dev_info.state = 0;
q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
+ q->backing_dev_info.name = "block";
err = bdi_init(&q->backing_dev_info);
if (err) {
diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
index 2307a27..0efb8fc 100644
--- a/drivers/block/aoe/aoeblk.c
+++ b/drivers/block/aoe/aoeblk.c
@@ -265,6 +265,7 @@ aoeblk_gdalloc(void *vp)
}
blk_queue_make_request(&d->blkq, aoeblk_make_request);
+ d->blkq.backing_dev_info.name = "aoe";
if (bdi_init(&d->blkq.backing_dev_info))
goto err_mempool;
spin_lock_irqsave(&d->lock, flags);
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index afa8813..645237b 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -822,6 +822,7 @@ static const struct file_operations zero_fops = {
* - permits private mappings, "copies" are taken of the source of zeros
*/
static struct backing_dev_info zero_bdi = {
+ .name = "char/mem",
.capabilities = BDI_CAP_MAP_COPY,
};
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 7dcaa81..bf380e1 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1353,6 +1353,7 @@ static int setup_bdi(struct btrfs_fs_info *info, struct backing_dev_info *bdi)
{
int err;
+ bdi->name = "btrfs";
bdi->capabilities = BDI_CAP_MAP_COPY;
err = bdi_init(bdi);
if (err)
diff --git a/fs/char_dev.c b/fs/char_dev.c
index a173551..7c27a8e 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -31,6 +31,7 @@
* - no readahead or I/O queue unplugging required
*/
struct backing_dev_info directly_mappable_cdev_bdi = {
+ .name = "char",
.capabilities = (
#ifdef CONFIG_MMU
/* permit private copies of the data to be taken */
diff --git a/fs/configfs/inode.c b/fs/configfs/inode.c
index 4921e74..a2f7460 100644
--- a/fs/configfs/inode.c
+++ b/fs/configfs/inode.c
@@ -51,6 +51,7 @@ static const struct address_space_operations configfs_aops = {
};
static struct backing_dev_info configfs_backing_dev_info = {
+ .name = "configfs",
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index f91ccc4..4567db6 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -801,6 +801,7 @@ static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb)
{
int err;
+ fc->bdi.name = "fuse";
fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
fc->bdi.unplug_io_fn = default_unplug_io_fn;
/* fuse does it's own writeback accounting */
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 941c842..2d8abaf 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -44,6 +44,7 @@ static const struct inode_operations hugetlbfs_dir_inode_operations;
static const struct inode_operations hugetlbfs_inode_operations;
static struct backing_dev_info hugetlbfs_backing_dev_info = {
+ .name = "hugetlbfs",
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 8d25ccb..c6be84a 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -879,6 +879,7 @@ static void nfs_server_set_fsinfo(struct nfs_server *server, struct nfs_fsinfo *
server->rsize = NFS_MAX_FILE_IO_SIZE;
server->rpages = (server->rsize + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+ server->backing_dev_info.name = "nfs";
server->backing_dev_info.ra_pages = server->rpages * NFS_MAX_READAHEAD;
if (server->wsize > max_rpc_payload)
diff --git a/fs/ocfs2/dlm/dlmfs.c b/fs/ocfs2/dlm/dlmfs.c
index 1c9efb4..02bf178 100644
--- a/fs/ocfs2/dlm/dlmfs.c
+++ b/fs/ocfs2/dlm/dlmfs.c
@@ -325,6 +325,7 @@ clear_fields:
}
static struct backing_dev_info dlmfs_backing_dev_info = {
+ .name = "ocfs2-dlmfs",
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 0ff7566..a7f0110 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -46,6 +46,7 @@ static const struct super_operations ramfs_ops;
static const struct inode_operations ramfs_dir_inode_operations;
static struct backing_dev_info ramfs_backing_dev_info = {
+ .name = "ramfs",
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK |
BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c
index 555f0ff..e57f98e 100644
--- a/fs/sysfs/inode.c
+++ b/fs/sysfs/inode.c
@@ -29,6 +29,7 @@ static const struct address_space_operations sysfs_aops = {
};
static struct backing_dev_info sysfs_backing_dev_info = {
+ .name = "sysfs",
.ra_pages = 0, /* No readahead */
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 26d2e0d..3e2bae7 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1971,6 +1971,7 @@ static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
*
* Read-ahead will be disabled because @c->bdi.ra_pages is 0.
*/
+ c->bdi.name = "ubifs",
c->bdi.capabilities = BDI_CAP_MAP_COPY;
c->bdi.unplug_io_fn = default_unplug_io_fn;
err = bdi_init(&c->bdi);
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 7a23f2f..3e52c98 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -69,6 +69,8 @@ struct backing_dev_info {
void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
void *unplug_io_data;
+ char *name;
+
struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
struct prop_local_percpu completions;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b6eadfe..c7ece8f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -600,6 +600,7 @@ static struct inode_operations cgroup_dir_inode_operations;
static struct file_operations proc_cgroupstats_operations;
static struct backing_dev_info cgroup_backing_dev_info = {
+ .name = "cgroup",
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index dbaf866..c6a62f4 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -17,6 +17,7 @@ void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
EXPORT_SYMBOL(default_unplug_io_fn);
struct backing_dev_info default_backing_dev_info = {
+ .name = "default",
.ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
.state = 0,
.capabilities = BDI_CAP_MAP_COPY,
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 42cd38e..5ae6b8b 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -34,6 +34,7 @@ static const struct address_space_operations swap_aops = {
};
static struct backing_dev_info swap_backing_dev_info = {
+ .name = "swap",
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
.unplug_io_fn = swap_unplug_io_fn,
};
--
1.6.3.2.306.g4f4fa
^ permalink raw reply related [flat|nested] 30+ messages in thread* [PATCH 9/9] writeback: check for registered bdi in flusher add and inode dirty
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
` (7 preceding siblings ...)
2009-07-30 21:24 ` [PATCH 8/9] writeback: add name to backing_dev_info Jens Axboe
@ 2009-07-30 21:24 ` Jens Axboe
2009-07-31 6:30 ` [PATCH 0/9] Per-bdi writeback flusher threads v13 Damien Wyart
9 siblings, 0 replies; 30+ messages in thread
From: Jens Axboe @ 2009-07-30 21:24 UTC (permalink / raw)
To: linux-kernel, linux-fsdevel
Cc: chris.mason, david, hch, akpm, jack, yanmin_zhang, richard,
damien.wyart, fweisbec, Alan.Brunelle, Jens Axboe
Also a debugging aid. We want to catch dirty inodes being added to
backing devices that don't do writeback.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
fs/fs-writeback.c | 7 +++++++
include/linux/backing-dev.h | 1 +
mm/backing-dev.c | 6 ++++++
3 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 796b243..dfb4767 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -643,6 +643,13 @@ void __mark_inode_dirty(struct inode *inode, int flags)
*/
if (!was_dirty) {
struct bdi_writeback *wb = inode_get_wb(inode);
+ struct backing_dev_info *bdi = wb->bdi;
+
+ if (bdi_cap_writeback_dirty(bdi) &&
+ !test_bit(BDI_registered, &bdi->state)) {
+ WARN_ON(1);
+ printk("bdi-%s not registered\n", bdi->name);
+ }
inode->dirtied_when = jiffies;
list_move(&inode->i_list, &wb->b_dirty);
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 3e52c98..47ed0f2 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -31,6 +31,7 @@ enum bdi_state {
BDI_wblist_lock, /* bdi->wb_list now needs locking */
BDI_async_congested, /* The async (write) queue is getting full */
BDI_sync_congested, /* The sync queue is getting full */
+ BDI_registered, /* bdi_register() was done */
BDI_unused, /* Available bits start here */
};
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index c6a62f4..036b07b 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -569,6 +569,11 @@ static void bdi_add_one_flusher_task(struct backing_dev_info *bdi,
if (!bdi_cap_writeback_dirty(bdi))
return;
+ if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) {
+ printk("bdi %p/%s is not registered!\n", bdi, bdi->name);
+ return;
+ }
+
/*
* Check with the helper whether to proceed adding a task. Will only
* abort if we two or more simultanous calls to
@@ -678,6 +683,7 @@ remove_err:
}
bdi_debug_register(bdi, dev_name(dev));
+ set_bit(BDI_registered, &bdi->state);
exit:
return ret;
}
--
1.6.3.2.306.g4f4fa
^ permalink raw reply related [flat|nested] 30+ messages in thread* Re: [PATCH 0/9] Per-bdi writeback flusher threads v13
2009-07-30 21:23 [PATCH 0/9] Per-bdi writeback flusher threads v13 Jens Axboe
` (8 preceding siblings ...)
2009-07-30 21:24 ` [PATCH 9/9] writeback: check for registered bdi in flusher add and inode dirty Jens Axboe
@ 2009-07-31 6:30 ` Damien Wyart
2009-07-31 7:15 ` Jens Axboe
9 siblings, 1 reply; 30+ messages in thread
From: Damien Wyart @ 2009-07-31 6:30 UTC (permalink / raw)
To: Jens Axboe
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm, jack,
yanmin_zhang, richard, fweisbec, Alan.Brunelle
Hello,
> Here's the 13th version of the writeback patches. Changes since v12:
> - Update to 2.6.31-rc4 ('ish, it's on top of current -git, but wil apply
> to -rc4 as well).
> - Drop the last patch in the series, it was a questionable optimization
> that needs to be tested and evaluated separately.
fs/sync.c has changed some time ago and I think your patch needs this
(which I had lazyly added by hand in v12 without telling):
--- a/fs/sync.c 2009-07-31 07:32:08.927926281 +0200
+++ b/fs/sync.c.new 2009-07-31 07:31:52.499801359 +0200
@@ -118,7 +118,7 @@ restart:
*/
SYSCALL_DEFINE0(sync)
{
- wakeup_pdflush(0);
+ wakeup_flusher_threads(0);
sync_filesystems(0);
sync_filesystems(1);
if (unlikely(laptop_mode))
Best,
--
Damien Wyart
^ permalink raw reply [flat|nested] 30+ messages in thread* Re: [PATCH 0/9] Per-bdi writeback flusher threads v13
2009-07-31 6:30 ` [PATCH 0/9] Per-bdi writeback flusher threads v13 Damien Wyart
@ 2009-07-31 7:15 ` Jens Axboe
2009-08-03 19:29 ` Damien Wyart
0 siblings, 1 reply; 30+ messages in thread
From: Jens Axboe @ 2009-07-31 7:15 UTC (permalink / raw)
To: Damien Wyart
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm, jack,
yanmin_zhang, richard, fweisbec, Alan.Brunelle
On Fri, Jul 31 2009, Damien Wyart wrote:
> Hello,
>
> > Here's the 13th version of the writeback patches. Changes since v12:
>
> > - Update to 2.6.31-rc4 ('ish, it's on top of current -git, but wil apply
> > to -rc4 as well).
> > - Drop the last patch in the series, it was a questionable optimization
> > that needs to be tested and evaluated separately.
>
> fs/sync.c has changed some time ago and I think your patch needs this
> (which I had lazyly added by hand in v12 without telling):
>
> --- a/fs/sync.c 2009-07-31 07:32:08.927926281 +0200
> +++ b/fs/sync.c.new 2009-07-31 07:31:52.499801359 +0200
> @@ -118,7 +118,7 @@ restart:
> */
> SYSCALL_DEFINE0(sync)
> {
> - wakeup_pdflush(0);
> + wakeup_flusher_threads(0);
> sync_filesystems(0);
> sync_filesystems(1);
> if (unlikely(laptop_mode))
Argh, I had fixed that long ago, but a branch problem yesterday caused
it to be lost just before posting. How annoying. Thanks for the hint,
I'll update the v13 branch and patch.
--
Jens Axboe
^ permalink raw reply [flat|nested] 30+ messages in thread* Re: [PATCH 0/9] Per-bdi writeback flusher threads v13
2009-07-31 7:15 ` Jens Axboe
@ 2009-08-03 19:29 ` Damien Wyart
2009-08-03 20:28 ` Jens Axboe
0 siblings, 1 reply; 30+ messages in thread
From: Damien Wyart @ 2009-08-03 19:29 UTC (permalink / raw)
To: Jens Axboe
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm, jack,
yanmin_zhang, richard, fweisbec, Alan.Brunelle
> > fs/sync.c has changed some time ago and I think your patch needs this
> > (which I had lazyly added by hand in v12 without telling):
> > --- a/fs/sync.c 2009-07-31 07:32:08.927926281 +0200
> > +++ b/fs/sync.c 2009-07-31 07:31:52.499801359 +0200
> > @@ -118,7 +118,7 @@ restart:
> > */
> > SYSCALL_DEFINE0(sync)
> > {
> > - wakeup_pdflush(0);
> > + wakeup_flusher_threads(0);
> > sync_filesystems(0);
> > sync_filesystems(1);
> > if (unlikely(laptop_mode))
* Jens Axboe <jens.axboe@oracle.com> [2009-07-31 09:15]:
> Argh, I had fixed that long ago, but a branch problem yesterday caused
> it to be lost just before posting. How annoying. Thanks for the hint,
> I'll update the v13 branch and patch.
Mmm. I wanted to test v13 on another machine and re-downloaded the patch
this morning (Paris time) but it seems completly wrong. It applied
cleany but I did not even try to compile as the files changed seemed
completely unrelated to per-bdi writeback. I guess there has been an
error in generating it.
Best,
--
Damien Wyart
^ permalink raw reply [flat|nested] 30+ messages in thread* Re: [PATCH 0/9] Per-bdi writeback flusher threads v13
2009-08-03 19:29 ` Damien Wyart
@ 2009-08-03 20:28 ` Jens Axboe
0 siblings, 0 replies; 30+ messages in thread
From: Jens Axboe @ 2009-08-03 20:28 UTC (permalink / raw)
To: Damien Wyart
Cc: linux-kernel, linux-fsdevel, chris.mason, david, hch, akpm, jack,
yanmin_zhang, richard, fweisbec, Alan.Brunelle
On Mon, Aug 03 2009, Damien Wyart wrote:
> > > fs/sync.c has changed some time ago and I think your patch needs this
> > > (which I had lazyly added by hand in v12 without telling):
>
> > > --- a/fs/sync.c 2009-07-31 07:32:08.927926281 +0200
> > > +++ b/fs/sync.c 2009-07-31 07:31:52.499801359 +0200
> > > @@ -118,7 +118,7 @@ restart:
> > > */
> > > SYSCALL_DEFINE0(sync)
> > > {
> > > - wakeup_pdflush(0);
> > > + wakeup_flusher_threads(0);
> > > sync_filesystems(0);
> > > sync_filesystems(1);
> > > if (unlikely(laptop_mode))
>
> * Jens Axboe <jens.axboe@oracle.com> [2009-07-31 09:15]:
> > Argh, I had fixed that long ago, but a branch problem yesterday caused
> > it to be lost just before posting. How annoying. Thanks for the hint,
> > I'll update the v13 branch and patch.
>
> Mmm. I wanted to test v13 on another machine and re-downloaded the patch
> this morning (Paris time) but it seems completly wrong. It applied
> cleany but I did not even try to compile as the files changed seemed
> completely unrelated to per-bdi writeback. I guess there has been an
> error in generating it.
Probably I diffed two wrong branches when updating the patch. I've
re-uploaded a newly generated diff.
--
Jens Axboe
^ permalink raw reply [flat|nested] 30+ messages in thread