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writeback: fix writeback_inodes_wb from writeback_inodes_sb 

When we call writeback_inodes_wb from writeback_inodes_sb we always have
s_umount held, which currently makes the whole operation a no-op.

But if we are called to write out inodes for a specific superblock we always
have s_umount held, so replace the incorrect logic checking for WB_SYNC_ALL
which only worked by coincidence with the proper check for an explicit
superblock argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Christoph Hellwig 2010-06-08 18:14:58 +02:00 committed by Jens Axboe
parent cf37e97247
commit d19de7edf5
1 changed files with 24 additions and 39 deletions
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63
fs/fs-writeback.c
View File

@ -518,39 +518,19 @@ writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
return ret;
}
static void unpin_sb_for_writeback(struct super_block *sb)
{
up_read(&sb->s_umount);
put_super(sb);
}
enum sb_pin_state {
SB_PINNED,
SB_NOT_PINNED,
SB_PIN_FAILED
};
/*
* For WB_SYNC_NONE writeback, the caller does not have the sb pinned
* For background writeback the caller does not have the sb pinned
* before calling writeback. So make sure that we do pin it, so it doesn't
* go away while we are writing inodes from it.
*/
static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc,
struct super_block *sb)
static bool pin_sb_for_writeback(struct super_block *sb)
{
/*
* Caller must already hold the ref for this
*/
if (wbc->sync_mode == WB_SYNC_ALL) {
WARN_ON(!rwsem_is_locked(&sb->s_umount));
return SB_NOT_PINNED;
}
spin_lock(&sb_lock);
sb->s_count++;
if (down_read_trylock(&sb->s_umount)) {
if (sb->s_root) {
spin_unlock(&sb_lock);
return SB_PINNED;
return true;
}
/*
* umounted, drop rwsem again and fall through to failure
@ -559,7 +539,7 @@ static enum sb_pin_state pin_sb_for_writeback(struct writeback_control *wbc,
}
sb->s_count--;
spin_unlock(&sb_lock);
return SB_PIN_FAILED;
return false;
}
/*
@ -638,24 +618,29 @@ static void writeback_inodes_wb(struct bdi_writeback *wb,
struct inode *inode = list_entry(wb->b_io.prev,
struct inode, i_list);
struct super_block *sb = inode->i_sb;
enum sb_pin_state state;
if (wbc->sb && sb != wbc->sb) {
/* super block given and doesn't
match, skip this inode */
redirty_tail(inode);
continue;
if (wbc->sb) {
/*
* We are requested to write out inodes for a specific
* superblock. This means we already have s_umount
* taken by the caller which also waits for us to
* complete the writeout.
*/
if (sb != wbc->sb) {
redirty_tail(inode);
continue;
}
WARN_ON(!rwsem_is_locked(&sb->s_umount));
ret = writeback_sb_inodes(sb, wb, wbc);
} else {
if (!pin_sb_for_writeback(sb))
continue;
ret = writeback_sb_inodes(sb, wb, wbc);
drop_super(sb);
}
state = pin_sb_for_writeback(wbc, sb);
if (state == SB_PIN_FAILED) {
requeue_io(inode);
continue;
}
ret = writeback_sb_inodes(sb, wb, wbc);
if (state == SB_PINNED)
unpin_sb_for_writeback(sb);
if (ret)
break;
}