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writeback: make the super_block pinning more efficient

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Currently we pin the inode->i_sb for every single inode. This
increases cache traffic on sb->s_umount sem. Lets instead
cache the inode sb pin state and keep the super_block pinned
for as long as keep writing out inodes from the same
super_block.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2009-09-24 15:25:11 +02:00
parent cf137307cd
commit 9ecc2738ac
1 changed files with 29 additions and 17 deletions
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46
fs/fs-writeback.c
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@ -540,6 +540,17 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
return ret;
}
static void unpin_sb_for_writeback(struct super_block **psb)
{
struct super_block *sb = *psb;
if (sb) {
up_read(&sb->s_umount);
put_super(sb);
*psb = NULL;
}
}
/*
* For WB_SYNC_NONE writeback, the caller does not have the sb pinned
* before calling writeback. So make sure that we do pin it, so it doesn't
@ -549,10 +560,19 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
* 1 if we failed.
*/
static int pin_sb_for_writeback(struct writeback_control *wbc,
struct inode *inode)
struct inode *inode, struct super_block **psb)
{
struct super_block *sb = inode->i_sb;
/*
* If this sb is already pinned, nothing more to do. If not and
* *psb is non-NULL, unpin the old one first
*/
if (sb == *psb)
return 0;
else if (*psb)
unpin_sb_for_writeback(psb);
/*
* Caller must already hold the ref for this
*/
@ -566,7 +586,7 @@ static int pin_sb_for_writeback(struct writeback_control *wbc,
if (down_read_trylock(&sb->s_umount)) {
if (sb->s_root) {
spin_unlock(&sb_lock);
return 0;
goto pinned;
}
/*
* umounted, drop rwsem again and fall through to failure
@ -577,24 +597,15 @@ static int pin_sb_for_writeback(struct writeback_control *wbc,
sb->s_count--;
spin_unlock(&sb_lock);
return 1;
}
static void unpin_sb_for_writeback(struct writeback_control *wbc,
struct inode *inode)
{
struct super_block *sb = inode->i_sb;
if (wbc->sync_mode == WB_SYNC_ALL)
return;
up_read(&sb->s_umount);
put_super(sb);
pinned:
*psb = sb;
return 0;
}
static void writeback_inodes_wb(struct bdi_writeback *wb,
struct writeback_control *wbc)
{
struct super_block *sb = wbc->sb;
struct super_block *sb = wbc->sb, *pin_sb = NULL;
const int is_blkdev_sb = sb_is_blkdev_sb(sb);
const unsigned long start = jiffies; /* livelock avoidance */
@ -653,7 +664,7 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
if (inode_dirtied_after(inode, start))
break;
if (pin_sb_for_writeback(wbc, inode)) {
if (pin_sb_for_writeback(wbc, inode, &pin_sb)) {
requeue_io(inode);
continue;
}
@ -662,7 +673,6 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
__iget(inode);
pages_skipped = wbc->pages_skipped;
writeback_single_inode(inode, wbc);
unpin_sb_for_writeback(wbc, inode);
if (wbc->pages_skipped != pages_skipped) {
/*
* writeback is not making progress due to locked
@ -682,6 +692,8 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
wbc->more_io = 1;
}
unpin_sb_for_writeback(&pin_sb);
spin_unlock(&inode_lock);
/* Leave any unwritten inodes on b_io */
}