Btrfs: fix some error codes in btrfs_qgroup_inherit()

These are returning zero when it should be returning a negative error
code.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

fs/btrfs/qgroup.c

@@ -1369,8 +1369,10 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
 
 	if (srcid) {
 		srcgroup = find_qgroup_rb(fs_info, srcid);
-		if (!srcgroup)
+		if (!srcgroup) {
+			ret = -EINVAL;
 			goto unlock;
+		}
 		dstgroup->rfer = srcgroup->rfer - level_size;
 		dstgroup->rfer_cmpr = srcgroup->rfer_cmpr - level_size;
 		srcgroup->excl = level_size;
@@ -1379,8 +1381,10 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
 		qgroup_dirty(fs_info, srcgroup);
 	}
 
-	if (!inherit)
+	if (!inherit) {
+		ret = -EINVAL;
 		goto unlock;
+	}
 
 	i_qgroups = (u64 *)(inherit + 1);
 	for (i = 0; i < inherit->num_qgroups; ++i) {