2567 	INIT_LIST_HEAD(&node->upper);
2590  * upper edges and any uncached nodes in the path.
2598 	struct btrfs_backref_node *upper;  local
2605 	while (!list_empty(&node->upper)) {
2606 		edge = list_entry(node->upper.next, struct btrfs_backref_edge,
2608 		upper = edge->node[UPPER];
2610 		list_del(&edge->list[UPPER]);
2617 		if (list_empty(&upper->lower)) {
2618 			list_add_tail(&upper->lower, &cache->leaves);
2619 			upper->lowest = 1;
2676 	struct btrfs_backref_node *upper;  local
2709 		upper = btrfs_backref_alloc_node(cache, ref_key->offset,
2711 		if (!upper) {
2717 		 *  Backrefs for the upper level block isn't cached, add the
2720 		list_add_tail(&edge->list[UPPER], &cache->pending_edge);
2723 		upper = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
2724 		ASSERT(upper->checked);
2725 		INIT_LIST_HEAD(&edge->list[UPPER]);
2727 	btrfs_backref_link_edge(edge, cur, upper, LINK_LOWER);
2750 	struct btrfs_backref_node *upper;  local
2841 			upper = btrfs_backref_alloc_node(cache, eb->start,
2843 			if (!upper) {
2849 			upper->owner = btrfs_header_owner(eb);
2851 				upper->cowonly = 1;
2858 				upper->checked = 0;
2860 				upper->checked = 1;
2867 			if (!upper->checked && need_check) {
2869 				list_add_tail(&edge->list[UPPER],
2872 				if (upper->checked)
2874 				INIT_LIST_HEAD(&edge->list[UPPER]);
2877 			upper = rb_entry(rb_node, struct btrfs_backref_node,
2879 			ASSERT(upper->checked);
2880 			INIT_LIST_HEAD(&edge->list[UPPER]);
2881 			if (!upper->owner)
2882 				upper->owner = btrfs_header_owner(eb);
2884 		btrfs_backref_link_edge(edge, lower, upper, LINK_LOWER);
2890 		lower = upper;
2891 		upper = NULL;
2901  * NOTE: Even if the function returned 0, @cur is not yet cached as its upper
2938 	if (!list_empty(&cur->upper)) {
2943 		ASSERT(list_is_singular(&cur->upper));
2944 		edge = list_entry(cur->upper.next, struct btrfs_backref_edge,
2946 		ASSERT(list_empty(&edge->list[UPPER]));
2947 		exist = edge->node[UPPER];
2949 		 * Add the upper level block to pending list if we need check
2953 			list_add_tail(&edge->list[UPPER], &cache->pending_edge);
3060 	list_for_each_entry(edge, &start->upper, list[LOWER])
3061 		list_add_tail(&edge->list[UPPER], &pending_edge);
3064 		struct btrfs_backref_node *upper;  local
3068 				struct btrfs_backref_edge, list[UPPER]);
3069 		list_del_init(&edge->list[UPPER]);
3070 		upper = edge->node[UPPER];
3074 		if (upper->detached) {
3079 			if (list_empty(&lower->upper))
3087 		 * So if we have upper->rb_node populated, this means a cache
3088 		 * hit. We only need to link the edge, as @upper and all its
3091 		if (!RB_EMPTY_NODE(&upper->rb_node)) {
3092 			if (upper->lowest) {
3093 				list_del_init(&upper->lower);
3094 				upper->lowest = 0;
3097 			list_add_tail(&edge->list[UPPER], &upper->lower);
3102 		if (!upper->checked) {
3108 		if (start->cowonly != upper->cowonly) {
3114 		if (!upper->cowonly) {
3115 			rb_node = rb_simple_insert(&cache->rb_root, upper->bytenr,
3116 						   &upper->rb_node);
3119 						upper->bytenr, -EEXIST);
3124 		list_add_tail(&edge->list[UPPER], &upper->lower);
3128 		 * to finish the upper linkage
3130 		list_for_each_entry(edge, &upper->upper, list[LOWER])
3131 			list_add_tail(&edge->list[UPPER], &pending_edge);
3140 	struct btrfs_backref_node *upper;  local
3150 				struct btrfs_backref_edge, list[UPPER]);
3151 		list_del(&edge->list[UPPER]);
3154 		upper = edge->node[UPPER];
3158 		 * Lower is no longer linked to any upper backref nodes and
3161 		if (list_empty(&lower->upper) &&
3165 		if (!RB_EMPTY_NODE(&upper->rb_node))
3168 		/* Add this guy's upper edges to the list to process */
3169 		list_for_each_entry(edge, &upper->upper, list[LOWER])
3170 			list_add_tail(&edge->list[UPPER],
3172 		if (list_empty(&upper->upper))
3173 			list_add(&upper->list, &cache->useless_node);