tree 3e4a910cd136c1b6666d3be7e33b826dbd016db6
parent 03a1d4c891634dd5b98da865fb783e8b22d4d027
author Liu Bo <bo.liu@linux.alibaba.com> 1534967512 +0800
committer David Sterba <dsterba@suse.com> 1539617013 +0200

Btrfs: extent_map: use rb_first_cached

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

As evict_inode_truncate_pages() removes all extent mapping by always
looking for the first rb entry, it's helpful to use rb_first_cached
instead.

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>