From: Mike Snitzer Date: Thu, 13 Jan 2011 19:53:46 +0000 (+0000) Subject: dm: dont take i_mutex to change device size X-Git-Tag: v2.6.32.29~41 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=67c39be22dd4201f827f85863787ad9569c2940c;p=karo-tx-linux.git dm: dont take i_mutex to change device size commit c217649bf2d60ac119afd71d938278cffd55962b upstream. No longer needlessly hold md->bdev->bd_inode->i_mutex when changing the size of a DM device. This additional locking is unnecessary because i_size_write() is already protected by the existing critical section in dm_swap_table(). DM already has a reference on md->bdev so the associated bd_inode may be changed without lifetime concerns. A negative side-effect of having held md->bdev->bd_inode->i_mutex was that a concurrent DM device resize and flush (via fsync) would deadlock. Dropping md->bdev->bd_inode->i_mutex eliminates this potential for deadlock. The following reproducer no longer deadlocks: https://www.redhat.com/archives/dm-devel/2009-July/msg00284.html Signed-off-by: Mike Snitzer Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/md/dm.c b/drivers/md/dm.c index d7786e3514cd..d1866878a814 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1925,13 +1925,14 @@ static void event_callback(void *context) wake_up(&md->eventq); } +/* + * Protected by md->suspend_lock obtained by dm_swap_table(). + */ static void __set_size(struct mapped_device *md, sector_t size) { set_capacity(md->disk, size); - mutex_lock(&md->bdev->bd_inode->i_mutex); i_size_write(md->bdev->bd_inode, (loff_t)size << SECTOR_SHIFT); - mutex_unlock(&md->bdev->bd_inode->i_mutex); } static int __bind(struct mapped_device *md, struct dm_table *t,