176 	/* List of upper level edges, which link this node to its parents */
177 	struct list_head upper;  member
198 	 * 1 if corresponding block has been COWed but some upper level block
213 #define UPPER	1  macro
216  * Represent an edge connecting upper and lower backref nodes.
220 	 * list[LOWER] is linked to btrfs_backref_node::upper of lower level
221 	 * node, and list[UPPER] is linked to btrfs_backref_node::lower of
222 	 * upper level node.
224 	 * Also, build_backref_tree() uses list[UPPER] for pending edges, before
225 	 * linking list[UPPER] to its upper level nodes.
239 	 * List of blocks that have been COWed but some block pointers in upper
283 					   struct btrfs_backref_node *upper,  in btrfs_backref_link_edge()  argument
286 	ASSERT(upper && lower && upper->level == lower->level + 1);  in btrfs_backref_link_edge()
288 	edge->node[UPPER] = upper;  in btrfs_backref_link_edge()
290 		list_add_tail(&edge->list[LOWER], &lower->upper);  in btrfs_backref_link_edge()
292 		list_add_tail(&edge->list[UPPER], &upper->lower);  in btrfs_backref_link_edge()
343 	BUG_ON(!list_empty(&node->upper));  in btrfs_backref_drop_node()