rb_find_add_cached
exist = rb_find_add_cached(&newref->rbnode, root, prelim_ref_rb_add_cmp);
exist = rb_find_add_cached(&block_group->cache_node,
exist = rb_find_add_cached(&ins->rb_node, root, btrfs_delayed_item_cmp);
struct rb_node *exist = rb_find_add_cached(node, root, cmp_refs_node);
exist = rb_find_add_cached(&map->rb_node, &fs_info->mapping_tree,