map_id_down
return VFSGIDT_INIT_RAW(map_id_down(&idmap->gid_map, gid));
return VFSUIDT_INIT_RAW(map_id_down(&idmap->uid_map, uid));
u32 map_id_down(struct uid_gid_map *map, u32 id);
return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));