btrfs: remove the ->lowest and ->leaves members from backref cache

Before we were keeping all of our nodes on various lists in order to
make sure everything got cleaned up correctly.  We used node->lowest to
indicate that node->lower was linked into the cache->leaves list.  Now
that we do cleanup based on the rb tree both the list and the flag are
useless, so delete them both.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: josefbacik

fs/btrfs/backref.c

@@ -3022,7 +3022,6 @@ void btrfs_backref_init_cache(struct btrfs_fs_info *fs_info,
 	for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 		INIT_LIST_HEAD(&cache->pending[i]);
 	INIT_LIST_HEAD(&cache->detached);
-	INIT_LIST_HEAD(&cache->leaves);
 	INIT_LIST_HEAD(&cache->pending_edge);
 	INIT_LIST_HEAD(&cache->useless_node);
 	cache->fs_info = fs_info;
@@ -3130,29 +3129,17 @@ void btrfs_backref_drop_node(struct btrfs_backref_cache *tree,
 void btrfs_backref_cleanup_node(struct btrfs_backref_cache *cache,
 				struct btrfs_backref_node *node)
 {
-	struct btrfs_backref_node *upper;
 	struct btrfs_backref_edge *edge;
 
 	if (!node)
 		return;
 
-	BUG_ON(!node->lowest && !node->detached);
 	while (!list_empty(&node->upper)) {
 		edge = list_entry(node->upper.next, struct btrfs_backref_edge,
 				  list[LOWER]);
-		upper = edge->node[UPPER];
 		list_del(&edge->list[LOWER]);
 		list_del(&edge->list[UPPER]);
 		btrfs_backref_free_edge(cache, edge);
-
-		/*
-		 * Add the node to leaf node list if no other child block
-		 * cached.
-		 */
-		if (list_empty(&upper->lower)) {
-			list_add_tail(&upper->lower, &cache->leaves);
-			upper->lowest = 1;
-		}
 	}
 
 	btrfs_backref_drop_node(cache, node);
@@ -3599,7 +3586,6 @@ int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
 	if (rb_node)
 		btrfs_backref_panic(cache->fs_info, start->bytenr,
 				    -EEXIST);
-	list_add_tail(&start->lower, &cache->leaves);
 
 	/*
 	 * Use breadth first search to iterate all related edges.
@@ -3638,11 +3624,6 @@ int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
 		 * parents have already been linked.
 		 */
 		if (!RB_EMPTY_NODE(&upper->rb_node)) {
-			if (upper->lowest) {
-				list_del_init(&upper->lower);
-				upper->lowest = 0;
-			}
-
 			list_add_tail(&edge->list[UPPER], &upper->lower);
 			continue;
 		}

fs/btrfs/backref.h

@@ -341,8 +341,6 @@ struct btrfs_backref_node {
 	struct extent_buffer *eb;
 	/* Level of the tree block */
 	unsigned int level:8;
-	/* 1 if no child node is in the cache */
-	unsigned int lowest:1;
 	/* Is the extent buffer locked */
 	unsigned int locked:1;
 	/* Has the block been processed */
@@ -395,8 +393,6 @@ struct btrfs_backref_cache {
 	 * level blocks may not reflect the new location
 	 */
 	struct list_head pending[BTRFS_MAX_LEVEL];
-	/* List of backref nodes with no child node */
-	struct list_head leaves;
 	/* List of detached backref node. */
 	struct list_head detached;
 

fs/btrfs/relocation.c

@@ -342,12 +342,6 @@ static bool handle_useless_nodes(struct reloc_control *rc,
 		if (cur == node)
 			ret = true;
 
-		/* The node is the lowest node */
-		if (cur->lowest) {
-			list_del_init(&cur->lower);
-			cur->lowest = 0;
-		}
-
 		/* Cleanup the lower edges */
 		while (!list_empty(&cur->lower)) {
 			struct btrfs_backref_edge *edge;
@@ -426,7 +420,6 @@ static noinline_for_stack struct btrfs_backref_node *build_backref_tree(
 		goto out;
 	}
 
-	node->lowest = 1;
 	cur = node;
 
 	/* Breadth-first search to build backref cache */