[PATCH] elevator: abstract out the rbtree sort handling

The rbtree sort/lookup/reposition logic is mostly duplicated in
cfq/deadline/as, so move it to the elevator core. The io schedulers
still provide the actual rb root, as we don't want to impose any sort
of specific handling on the schedulers.

Introduce the helpers and rb_node in struct request to help migrate the
IO schedulers.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8f5486964671..a905c4934a55 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -230,6 +230,7 @@ struct request {
         struct bio *biotail;
 
         struct hlist_node hash; /* merge hash */
+        struct rb_node rb_node; /* sort/lookup */
 
         void *elevator_private;
         void *completion_data;