2505 	INIT_LIST_HEAD(&node->upper);
2528  * upper edges and any uncached nodes in the path.
2536 	struct btrfs_backref_node *upper;  local
2543 	while (!list_empty(&node->upper)) {
2544 		edge = list_entry(node->upper.next, struct btrfs_backref_edge,
2546 		upper = edge->node[UPPER];
2548 		list_del(&edge->list[UPPER]);
2555 		if (list_empty(&upper->lower)) {
2556 			list_add_tail(&upper->lower, &cache->leaves);
2557 			upper->lowest = 1;
2614 	struct btrfs_backref_node *upper;  local
2647 		upper = btrfs_backref_alloc_node(cache, ref_key->offset,
2649 		if (!upper) {
2655 		 *  Backrefs for the upper level block isn't cached, add the
2658 		list_add_tail(&edge->list[UPPER], &cache->pending_edge);
2661 		upper = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
2662 		ASSERT(upper->checked);
2663 		INIT_LIST_HEAD(&edge->list[UPPER]);
2665 	btrfs_backref_link_edge(edge, cur, upper, LINK_LOWER);
2688 	struct btrfs_backref_node *upper;  local
2779 			upper = btrfs_backref_alloc_node(cache, eb->start,
2781 			if (!upper) {
2787 			upper->owner = btrfs_header_owner(eb);
2789 				upper->cowonly = 1;
2796 				upper->checked = 0;
2798 				upper->checked = 1;
2805 			if (!upper->checked && need_check) {
2807 				list_add_tail(&edge->list[UPPER],
2810 				if (upper->checked)
2812 				INIT_LIST_HEAD(&edge->list[UPPER]);
2815 			upper = rb_entry(rb_node, struct btrfs_backref_node,
2817 			ASSERT(upper->checked);
2818 			INIT_LIST_HEAD(&edge->list[UPPER]);
2819 			if (!upper->owner)
2820 				upper->owner = btrfs_header_owner(eb);
2822 		btrfs_backref_link_edge(edge, lower, upper, LINK_LOWER);
2828 		lower = upper;
2829 		upper = NULL;
2839  * NOTE: Even if the function returned 0, @cur is not yet cached as its upper
2876 	if (!list_empty(&cur->upper)) {
2881 		ASSERT(list_is_singular(&cur->upper));
2882 		edge = list_entry(cur->upper.next, struct btrfs_backref_edge,
2884 		ASSERT(list_empty(&edge->list[UPPER]));
2885 		exist = edge->node[UPPER];
2887 		 * Add the upper level block to pending list if we need check
2891 			list_add_tail(&edge->list[UPPER], &cache->pending_edge);
2998 	list_for_each_entry(edge, &start->upper, list[LOWER])
2999 		list_add_tail(&edge->list[UPPER], &pending_edge);
3002 		struct btrfs_backref_node *upper;  local
3006 				struct btrfs_backref_edge, list[UPPER]);
3007 		list_del_init(&edge->list[UPPER]);
3008 		upper = edge->node[UPPER];
3012 		if (upper->detached) {
3017 			if (list_empty(&lower->upper))
3025 		 * So if we have upper->rb_node populated, this means a cache
3026 		 * hit. We only need to link the edge, as @upper and all its
3029 		if (!RB_EMPTY_NODE(&upper->rb_node)) {
3030 			if (upper->lowest) {
3031 				list_del_init(&upper->lower);
3032 				upper->lowest = 0;
3035 			list_add_tail(&edge->list[UPPER], &upper->lower);
3040 		if (!upper->checked) {
3046 		if (start->cowonly != upper->cowonly) {
3052 		if (!upper->cowonly) {
3053 			rb_node = rb_simple_insert(&cache->rb_root, upper->bytenr,
3054 						   &upper->rb_node);
3057 						upper->bytenr, -EEXIST);
3062 		list_add_tail(&edge->list[UPPER], &upper->lower);
3066 		 * to finish the upper linkage
3068 		list_for_each_entry(edge, &upper->upper, list[LOWER])
3069 			list_add_tail(&edge->list[UPPER], &pending_edge);
3078 	struct btrfs_backref_node *upper;  local
3088 				struct btrfs_backref_edge, list[UPPER]);
3089 		list_del(&edge->list[UPPER]);
3092 		upper = edge->node[UPPER];
3096 		 * Lower is no longer linked to any upper backref nodes and
3099 		if (list_empty(&lower->upper) &&
3103 		if (!RB_EMPTY_NODE(&upper->rb_node))
3106 		/* Add this guy's upper edges to the list to process */
3107 		list_for_each_entry(edge, &upper->upper, list[LOWER])
3108 			list_add_tail(&edge->list[UPPER],
3110 		if (list_empty(&upper->upper))
3111 			list_add(&upper->list, &cache->useless_node);