btrfs: avoid transaction commit on error in insert_balance_item()

There's no point in committing the transaction if we failed to insert the
balance item, since we haven't done anything else after we started/joined
the transaction. Also stop using two variables for tracking the return
value and use only 'ret'.

Reviewed-by: Daniel Vacek <neelx@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>

Author: fdmanana

fs/btrfs/volumes.c

@@ -3642,7 +3642,7 @@ static int insert_balance_item(struct btrfs_fs_info *fs_info,
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;
 	struct btrfs_key key;
-	int ret, err;
+	int ret;
 
 	path = btrfs_alloc_path();
 	if (!path)
@@ -3677,9 +3677,11 @@ static int insert_balance_item(struct btrfs_fs_info *fs_info,
 	btrfs_set_balance_flags(leaf, item, bctl->flags);
 out:
 	btrfs_free_path(path);
-	err = btrfs_commit_transaction(trans);
-	if (err && !ret)
-		ret = err;
+	if (ret == 0)
+		ret = btrfs_commit_transaction(trans);
+	else
+		btrfs_end_transaction(trans);
+
 	return ret;
 }