Btrfs: fix return value on rename exchange failure

If we failed during a rename exchange operation after starting/joining a
transaction, we would end up replacing the return value, stored in the
local 'ret' variable, with the return value from btrfs_end_transaction().
So this could end up returning 0 (success) to user space despite the
operation having failed and aborted the transaction, because if there are
multiple tasks having a reference on the transaction at the time
btrfs_end_transaction() is called by the rename exchange, that function
returns 0 (otherwise it returns -EIO and not the original error value).
So fix this by not overwriting the return value on error after getting
a transaction handle.

Fixes: cdd1fedf8261 ("btrfs: add support for RENAME_EXCHANGE and RENAME_WHITEOUT")
CC: stable@vger.kernel.org # 4.9+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c12b7a6..a6bf9e2 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9443,6 +9443,7 @@ static int btrfs_rename_exchange(struct inode *old_dir,
        u64 new_idx = 0;
        u64 root_objectid;
        int ret;
+       int ret2;
        bool root_log_pinned = false;
        bool dest_log_pinned = false;
 
@@ -9639,7 +9640,8 @@ out_fail:
                        dest_log_pinned = false;
                }
        }
-       ret = btrfs_end_transaction(trans);
+       ret2 = btrfs_end_transaction(trans);
+       ret = ret ? ret : ret2;
 out_notrans:
        if (new_ino == BTRFS_FIRST_FREE_OBJECTID)
                up_read(&fs_info->subvol_sem);