HMD_FORCE_CHILD
nd = __rb_hierarchy_next(nd, HMD_FORCE_CHILD);
nd = __rb_hierarchy_next(nd, HMD_FORCE_CHILD);
nd = __rb_hierarchy_next(nd, HMD_FORCE_CHILD)) {
if (he->unfolded || hmd == HMD_FORCE_CHILD)
nd = __rb_hierarchy_next(&h->rb_node, HMD_FORCE_CHILD);