btrfs: don't double lock the subvol_sem for rename exchange
authorJosef Bacik <josef@toxicpanda.com>
Tue, 19 Nov 2019 18:59:20 +0000 (13:59 -0500)
committerDavid Sterba <dsterba@suse.com>
Fri, 13 Dec 2019 13:09:23 +0000 (14:09 +0100)
If we're rename exchanging two subvols we'll try to lock this lock
twice, which is bad.  Just lock once if either of the ino's are subvols.

Fixes: cdd1fedf8261 ("btrfs: add support for RENAME_EXCHANGE and RENAME_WHITEOUT")
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs/btrfs/inode.c

index 5766c2d..e3c7664 100644 (file)
@@ -9554,9 +9554,8 @@ static int btrfs_rename_exchange(struct inode *old_dir,
        btrfs_init_log_ctx(&ctx_dest, new_inode);
 
        /* close the race window with snapshot create/destroy ioctl */
-       if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
-               down_read(&fs_info->subvol_sem);
-       if (new_ino == BTRFS_FIRST_FREE_OBJECTID)
+       if (old_ino == BTRFS_FIRST_FREE_OBJECTID ||
+           new_ino == BTRFS_FIRST_FREE_OBJECTID)
                down_read(&fs_info->subvol_sem);
 
        /*
@@ -9790,9 +9789,8 @@ out_fail:
                ret = ret ? ret : ret2;
        }
 out_notrans:
-       if (new_ino == BTRFS_FIRST_FREE_OBJECTID)
-               up_read(&fs_info->subvol_sem);
-       if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
+       if (new_ino == BTRFS_FIRST_FREE_OBJECTID ||
+           old_ino == BTRFS_FIRST_FREE_OBJECTID)
                up_read(&fs_info->subvol_sem);
 
        ASSERT(list_empty(&ctx_root.list));