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, 1 insertions, 0 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 6804fdf27eff..3c26c7f48703 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -497,6 +497,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
                     laptop_mode_timer_fn, (unsigned long) q);
         setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
         INIT_LIST_HEAD(&q->timeout_list);
+        INIT_LIST_HEAD(&q->icq_list);
         INIT_LIST_HEAD(&q->flush_queue[0]);
         INIT_LIST_HEAD(&q->flush_queue[1]);
         INIT_LIST_HEAD(&q->flush_data_in_flight);