interval_tree_for_each_span
interval_tree_for_each_span(&allowed_span, &iopt->allowed_itree,
interval_tree_for_each_span(&span, &ioas->iopt.reserved_itree, 0,
interval_tree_for_each_span(&span, &ioas->iopt.reserved_itree, 0,
interval_tree_for_each_span(&span, &root, start, last) {