5.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Filipe Manana fdmanana@suse.com
commit 4ea748e1d2c9f8a27332b949e8210dbbf392987e upstream.
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: Zygo Blaxell ce3g8jdj@umail.furryterror.org Fixes: 416161db9b63e3 ("btrfs: offline dedupe") CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/ioctl.c | 21 +++------------------ 1 file changed, 3 insertions(+), 18 deletions(-)
--- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -3206,21 +3206,6 @@ out: return ret; }
-static void btrfs_double_inode_unlock(struct inode *inode1, struct inode *inode2) -{ - inode_unlock(inode1); - inode_unlock(inode2); -} - -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); -} - static void btrfs_double_extent_unlock(struct inode *inode1, u64 loff1, struct inode *inode2, u64 loff2, u64 len) { @@ -3989,7 +3974,7 @@ static int btrfs_remap_file_range_prep(s if (same_inode) inode_lock(inode_in); else - btrfs_double_inode_lock(inode_in, inode_out); + lock_two_nondirectories(inode_in, inode_out);
/* * Now that the inodes are locked, we need to start writeback ourselves @@ -4039,7 +4024,7 @@ static int btrfs_remap_file_range_prep(s if (same_inode) inode_unlock(inode_in); else - btrfs_double_inode_unlock(inode_in, inode_out); + unlock_two_nondirectories(inode_in, inode_out);
return ret; } @@ -4069,7 +4054,7 @@ loff_t btrfs_remap_file_range(struct fil if (same_inode) inode_unlock(src_inode); else - btrfs_double_inode_unlock(src_inode, dst_inode); + unlock_two_nondirectories(src_inode, dst_inode);
return ret < 0 ? ret : len; }