btrfs: abort transaction at balance_level() when left child is missing

At balance_level() we are calling btrfs_handle_fs_error() when the middle
child only has 1 item and the left child is missing, however we can simply
use btrfs_abort_transaction(), which achieves the same purposes: to turn
the fs to error state, abort the current transaction and turn the fs to
RO mode. Besides that, btrfs_abort_transaction() also prints a stack trace
which makes it more useful.

Also, as this is a highly unexpected case and it's about a b+tree
inconsistency, change the error code from -EROFS to -EUCLEAN, tag the if
branch as 'unlikely' and log an explicit error message.

Reviewed-by: Qu Wenruo <wqu@suse.com>
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/ctree.c b/fs/btrfs/ctree.c
index 4dcdcf2..00eea29 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1164,9 +1164,13 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
                 * otherwise we would have pulled some pointers from the
                 * right
                 */
-               if (!left) {
-                       ret = -EROFS;
-                       btrfs_handle_fs_error(fs_info, ret, NULL);
+               if (unlikely(!left)) {
+                       btrfs_crit(fs_info,
+"missing left child when middle child only has 1 item, parent bytenr %llu level %d mid bytenr %llu root %llu",
+                                  parent->start, btrfs_header_level(parent),
+                                  mid->start, btrfs_root_id(root));
+                       ret = -EUCLEAN;
+                       btrfs_abort_transaction(trans, ret);
                        goto out;
                }
                wret = balance_node_right(trans, mid, left);