btrfs: handle ENOENT in btrfs_uuid_tree_iterate

If we get an -ENOENT back from btrfs_uuid_iter_rem when iterating the
uuid tree we'll just continue and do btrfs_next_item().  However we've
done a btrfs_release_path() at this point and no longer have a valid
path.  So increment the key and go back and do a normal search.

CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
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/uuid-tree.c

@@ -324,6 +324,8 @@ int btrfs_uuid_tree_iterate(struct btrfs_fs_info *fs_info,
 				}
 				if (ret < 0 && ret != -ENOENT)
 					goto out;
+				key.offset++;
+				goto again_search_slot;
 			}
 			item_size -= sizeof(subid_le);
 			offset += sizeof(subid_le);