tree 0a1f7bfe1f829f2ba99c938ab0ffb03eb27fa6ac
parent 5c9d028b3b174e5cf3678a7b0c14e21e51665793
author Liu Bo <bo.liu@linux.alibaba.com> 1534967510 +0800
committer David Sterba <dsterba@suse.com> 1539617013 +0200

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>