Btrfs: fix deadlock between clone/dedupe and rename
Reflinking (clone/dedupe) and rename are operations that operate on two inodes and therefore need to lock them in the same order to avoid ABBA deadlocks. It happens that Btrfs' reflink implementation always locked them in a different order from VFS's lock_two_nondirectories() helper, which is used by the rename code in VFS, resulting in ABBA type deadlocks. Btrfs' locking order: static void btrfs_double_inode_lock(struct inode *inode1, struct inode *inode2) { if (inode1 < inode2) swap(inode1, inode2); inode_lock_nested(inode1, I_MUTEX_PARENT); inode_lock_nested(inode2, I_MUTEX_CHILD); } VFS's locking order: void lock_two_nondirectories(struct inode *inode1, struct inode *inode2) { if (inode1 > inode2) swap(inode1, inode2); if (inode1 && !S_ISDIR(inode1->i_mode)) inode_lock(inode1); if (inode2 && !S_ISDIR(inode2->i_mode) && inode2 != inode1) inode_lock_nested(inode2, I_MUTEX_NONDIR2); } Fix this by killing the btrfs helper function that does the double inode locking and replace it with VFS's helper lock_two_nondirectories(). Reported-by: NZygo Blaxell <ce3g8jdj@umail.furryterror.org> Fixes: 416161db ("btrfs: offline dedupe") CC: stable@vger.kernel.org # 4.4+ Signed-off-by: NFilipe Manana <fdmanana@suse.com> Signed-off-by: NDavid Sterba <dsterba@suse.com>
Showing
想要评论请 注册 或 登录