Btrfs: delayed-inode: use rb_first_cached for ins_root and del_root

rb_first_cached() trades an extra pointer "leftmost" for doing the same job as
rb_first() but in O(1).

Functions manipulating delayed_item need to get the first entry, this converts
it to use rb_first_cached().

For more details about the optimization see patch "Btrfs: delayed-refs:
use rb_first_cached for href_root".
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/delayed-inode.c

@@ -42,8 +42,8 @@ static inline void btrfs_init_delayed_node(
 	delayed_node->root = root;
 	delayed_node->inode_id = inode_id;
 	refcount_set(&delayed_node->refs, 0);
-	delayed_node->ins_root = RB_ROOT;
-	delayed_node->del_root = RB_ROOT;
+	delayed_node->ins_root = RB_ROOT_CACHED;
+	delayed_node->del_root = RB_ROOT_CACHED;
 	mutex_init(&delayed_node->mutex);
 	INIT_LIST_HEAD(&delayed_node->n_list);
 	INIT_LIST_HEAD(&delayed_node->p_list);
@@ -390,7 +390,7 @@ static struct btrfs_delayed_item *__btrfs_lookup_delayed_insertion_item(
 					struct btrfs_delayed_node *delayed_node,
 					struct btrfs_key *key)
 {
-	return __btrfs_lookup_delayed_item(&delayed_node->ins_root, key,
+	return __btrfs_lookup_delayed_item(&delayed_node->ins_root.rb_root, key,
 					   NULL, NULL);
 }
 
@@ -400,9 +400,10 @@ static int __btrfs_add_delayed_item(struct btrfs_delayed_node *delayed_node,
 {
 	struct rb_node **p, *node;
 	struct rb_node *parent_node = NULL;
-	struct rb_root *root;
+	struct rb_root_cached *root;
 	struct btrfs_delayed_item *item;
 	int cmp;
+	bool leftmost = true;
 
 	if (action == BTRFS_DELAYED_INSERTION_ITEM)
 		root = &delayed_node->ins_root;
@@ -410,7 +411,7 @@ static int __btrfs_add_delayed_item(struct btrfs_delayed_node *delayed_node,
 		root = &delayed_node->del_root;
 	else
 		BUG();
-	p = &root->rb_node;
+	p = &root->rb_root.rb_node;
 	node = &ins->rb_node;
 
 	while (*p) {
@@ -419,16 +420,18 @@ static int __btrfs_add_delayed_item(struct btrfs_delayed_node *delayed_node,
 				 rb_node);
 
 		cmp = btrfs_comp_cpu_keys(&item->key, &ins->key);
-		if (cmp < 0)
+		if (cmp < 0) {
 			p = &(*p)->rb_right;
-		else if (cmp > 0)
+			leftmost = false;
+		} else if (cmp > 0) {
 			p = &(*p)->rb_left;
-		else
+		} else {
 			return -EEXIST;
+		}
 	}
 
 	rb_link_node(node, parent_node, p);
-	rb_insert_color(node, root);
+	rb_insert_color_cached(node, root, leftmost);
 	ins->delayed_node = delayed_node;
 	ins->ins_or_del = action;
 
@@ -468,7 +471,7 @@ static void finish_one_item(struct btrfs_delayed_root *delayed_root)
 
 static void __btrfs_remove_delayed_item(struct btrfs_delayed_item *delayed_item)
 {
-	struct rb_root *root;
+	struct rb_root_cached *root;
 	struct btrfs_delayed_root *delayed_root;
 
 	delayed_root = delayed_item->delayed_node->root->fs_info->delayed_root;
@@ -482,7 +485,7 @@ static void __btrfs_remove_delayed_item(struct btrfs_delayed_item *delayed_item)
 	else
 		root = &delayed_item->delayed_node->del_root;
 
-	rb_erase(&delayed_item->rb_node, root);
+	rb_erase_cached(&delayed_item->rb_node, root);
 	delayed_item->delayed_node->count--;
 
 	finish_one_item(delayed_root);
@@ -503,7 +506,7 @@ static struct btrfs_delayed_item *__btrfs_first_delayed_insertion_item(
 	struct rb_node *p;
 	struct btrfs_delayed_item *item = NULL;
 
-	p = rb_first(&delayed_node->ins_root);
+	p = rb_first_cached(&delayed_node->ins_root);
 	if (p)
 		item = rb_entry(p, struct btrfs_delayed_item, rb_node);
 
@@ -516,7 +519,7 @@ static struct btrfs_delayed_item *__btrfs_first_delayed_deletion_item(
 	struct rb_node *p;
 	struct btrfs_delayed_item *item = NULL;
 
-	p = rb_first(&delayed_node->del_root);
+	p = rb_first_cached(&delayed_node->del_root);
 	if (p)
 		item = rb_entry(p, struct btrfs_delayed_item, rb_node);
 

fs/btrfs/delayed-inode.h

@@ -50,8 +50,8 @@ struct btrfs_delayed_node {
 	 * is waiting to be dealt with by the async worker.
 	 */
 	struct list_head p_list;
-	struct rb_root ins_root;
-	struct rb_root del_root;
+	struct rb_root_cached ins_root;
+	struct rb_root_cached del_root;
 	struct mutex mutex;
 	struct btrfs_inode_item inode_item;
 	refcount_t refs;