From: Mike Snitzer DM no longer needlessly holds 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 Cc: stable@kernel.org --- drivers/md/dm.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) Index: linux-2.6.37-rc4/drivers/md/dm.c =================================================================== --- linux-2.6.37-rc4.orig/drivers/md/dm.c +++ linux-2.6.37-rc4/drivers/md/dm.c @@ -1996,9 +1996,12 @@ static void __set_size(struct mapped_dev { set_capacity(md->disk, size); - mutex_lock(&md->bdev->bd_inode->i_mutex); + /* + * Only DM is allowed to change the size of a DM device. + * i_size_write() is protected by the dm_swap_table() critical + * section that uses md->suspend_lock. + */ i_size_write(md->bdev->bd_inode, (loff_t)size << SECTOR_SHIFT); - mutex_unlock(&md->bdev->bd_inode->i_mutex); } /*