block, cfq: move cfqd->icq_list to request_queue and add request->elv.icq

Most of icq management is about to be moved out of cfq into blk-ioc.
This patch prepares for it.

* Move cfqd->icq_list to request_queue->icq_list

* Make request explicitly point to icq instead of through elevator
  private data.  ->elevator_private[3] is replaced with sub struct elv
  which contains icq pointer and priv[2].  cfq is updated accordingly.

* Meaningless clearing of ->elevator_private[0] removed from
  elv_set_request().  At that point in code, the field was guaranteed
  to be %NULL anyway.

This patch doesn't introduce any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 8 insertions, 2 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 65c2f8c70089..8bca04873f53 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -111,10 +111,14 @@ struct request {
          * Three pointers are available for the IO schedulers, if they need
          * more they have to dynamically allocate it.  Flush requests are
          * never put on the IO scheduler. So let the flush fields share
-         * space with the three elevator_private pointers.
+         * space with the elevator data.
          */
         union {
-                void *elevator_private[3];
+                struct {
+                        struct io_cq            *icq;
+                        void                    *priv[2];
+                } elv;
+
                 struct {
                         unsigned int            seq;
                         struct list_head        list;
@@ -357,6 +361,8 @@ struct request_queue {
         struct timer_list       timeout;
         struct list_head        timeout_list;
 
+        struct list_head        icq_list;
+
         struct queue_limits     limits;
 
         /*