58 	struct list_head lower;  member
231 				  struct backref_node, lower);  in backref_cache_cleanup()
254 		INIT_LIST_HEAD(&node->lower);  in alloc_backref_node()
371 	struct backref_node *lower;  in walk_down_backref()  local
376 		lower = edge->node[LOWER];  in walk_down_backref()
377 		if (list_is_last(&edge->list[LOWER], &lower->upper)) {  in walk_down_backref()
415 	list_del(&node->lower);  in drop_backref_node()
453 		if (list_empty(&upper->lower)) {  in remove_backref_node()
454 			list_add_tail(&upper->lower, &cache->leaves);  in remove_backref_node()
690 	struct backref_node *lower;  local
927 		lower = cur;
932 				       lower->bytenr);
934 					list_add(&lower->list, &useless);
936 					lower->root = root;
957 				upper->level = lower->level + 1;
994 			list_add_tail(&edge->list[LOWER], &lower->upper);
995 			edge->node[LOWER] = lower;
1000 			lower = upper;
1040 		list_add_tail(&node->lower, &cache->leaves);
1052 			lower = edge->node[LOWER];
1054 			if (list_empty(&lower->upper))
1055 				list_add(&lower->list, &useless);
1061 				list_del_init(&upper->lower);
1065 			list_add_tail(&edge->list[UPPER], &upper->lower);
1092 		list_add_tail(&edge->list[UPPER], &upper->lower);
1110 			list_del_init(&upper->lower);
1113 		while (!list_empty(&upper->lower)) {
1114 			edge = list_entry(upper->lower.next,
1118 			lower = edge->node[LOWER];
1121 			if (list_empty(&lower->upper))
1122 				list_add(&lower->list, &useless);
1138 			lower = list_entry(useless.next,
1140 			list_del_init(&lower->list);
1147 			lower = edge->node[LOWER];
1155 			if (list_empty(&lower->upper) &&
1156 			    RB_EMPTY_NODE(&lower->rb_node))
1157 				list_add(&lower->list, &useless);
1170 			lower = list_entry(useless.next,
1172 			list_del_init(&lower->list);
1173 			free_backref_node(cache, lower);
1235 		list_for_each_entry(edge, &node->lower, list[UPPER]) {
1243 				      &new_node->lower);
1246 		list_add_tail(&new_node->lower, &cache->leaves);
1255 		list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
1262 	while (!list_empty(&new_node->lower)) {
1263 		new_edge = list_entry(new_node->lower.next,