btrfs: delayed-ref: Use list to replace the ref_root in ref_head.

This patch replace the rbtree used in ref_head to list.
This has the following advantage:
1) Easier merge logic.
With the new list implement, we only need to care merging the tail
ref_node with the new ref_node.
And this can be done quite easy at insert time, no need to do a
indicated merge at run_delayed_refs().

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 2 insertions, 7 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index a3316f1707e6..49bc5a41c1f8 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -574,8 +574,8 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
 			      struct list_head *prefs, u64 *total_refs,
 			      u64 inum)
 {
+	struct btrfs_delayed_ref_node *node;
 	struct btrfs_delayed_extent_op *extent_op = head->extent_op;
-	struct rb_node *n = &head->node.rb_node;
 	struct btrfs_key key;
 	struct btrfs_key op_key = {0};
 	int sgn;
@@ -585,12 +585,7 @@ static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
 		btrfs_disk_key_to_cpu(&op_key, &extent_op->key);
 
 	spin_lock(&head->lock);
-	n = rb_first(&head->ref_root);
-	while (n) {
-		struct btrfs_delayed_ref_node *node;
-		node = rb_entry(n, struct btrfs_delayed_ref_node,
-				rb_node);
-		n = rb_next(n);
+	list_for_each_entry(node, &head->ref_list, list) {
 		if (node->seq > seq)
 			continue;