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writeback: fix pin_sb_for_writeback 

We need to check for s_instances to make sure we don't bother working
against a filesystem that is beeing unmounted, and we need to call
put_super to make sure a superblock is freed when we race against
umount.  Also no need to keep sb_lock after we got a reference on it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Christoph Hellwig 2010-06-09 15:31:01 +02:00 committed by Jens Axboe
parent 334132ae92
commit 29cb48594b
1 changed files with 10 additions and 8 deletions
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18
fs/fs-writeback.c
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@ -534,19 +534,21 @@ select_queue:
static bool pin_sb_for_writeback(struct super_block *sb)
{
spin_lock(&sb_lock);
if (list_empty(&sb->s_instances)) {
spin_unlock(&sb_lock);
return false;
}
sb->s_count++;
spin_unlock(&sb_lock);
if (down_read_trylock(&sb->s_umount)) {
if (sb->s_root) {
spin_unlock(&sb_lock);
if (sb->s_root)
return true;
}
/*
* umounted, drop rwsem again and fall through to failure
*/
up_read(&sb->s_umount);
}
sb->s_count--;
spin_unlock(&sb_lock);
put_super(sb);
return false;
}