Btrfs: delayed-refs: use rb_first_cached for ref_tree
rb_first_cached() trades an extra pointer "leftmost" for doing the same
job as rb_first() but in O(1).
Functions manipulating href->ref_tree need to get the first entry, this
converts href->ref_tree 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>
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 84006e3..1854835 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -769,7 +769,7 @@ static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
btrfs_disk_key_to_cpu(&tmp_op_key, &extent_op->key);
spin_lock(&head->lock);
- for (n = rb_first(&head->ref_tree); n; n = rb_next(n)) {
+ for (n = rb_first_cached(&head->ref_tree); n; n = rb_next(n)) {
node = rb_entry(n, struct btrfs_delayed_ref_node,
ref_node);
if (node->seq > seq)