193 	/* List of upper level edges, which link this node to its parents */
194 	struct list_head upper;  member
215 	 * 1 if corresponding block has been COWed but some upper level block
230 #define UPPER	1  macro
233  * Represent an edge connecting upper and lower backref nodes.
237 	 * list[LOWER] is linked to btrfs_backref_node::upper of lower level
238 	 * node, and list[UPPER] is linked to btrfs_backref_node::lower of
239 	 * upper level node.
241 	 * Also, build_backref_tree() uses list[UPPER] for pending edges, before
242 	 * linking list[UPPER] to its upper level nodes.
256 	 * List of blocks that have been COWed but some block pointers in upper
300 					   struct btrfs_backref_node *upper,  in btrfs_backref_link_edge()  argument
303 	ASSERT(upper && lower && upper->level == lower->level + 1);  in btrfs_backref_link_edge()
305 	edge->node[UPPER] = upper;  in btrfs_backref_link_edge()
307 		list_add_tail(&edge->list[LOWER], &lower->upper);  in btrfs_backref_link_edge()
309 		list_add_tail(&edge->list[UPPER], &upper->lower);  in btrfs_backref_link_edge()
363 	ASSERT(list_empty(&node->upper));  in btrfs_backref_drop_node()