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>

3 files changed, 12 insertions, 19 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);
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index d2f16fcdec7f..9bc5ecc1b336 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -54,9 +54,9 @@ static const int cfq_hist_divisor = 4;
 #define CFQQ_SECT_THR_NONROT    (sector_t)(2 * 32)
 #define CFQQ_SEEKY(cfqq)        (hweight32(cfqq->seek_history) > 32/8)
 
-#define RQ_CIC(rq)              icq_to_cic((rq)->elevator_private[0])
-#define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elevator_private[1])
-#define RQ_CFQG(rq)             (struct cfq_group *) ((rq)->elevator_private[2])
+#define RQ_CIC(rq)              icq_to_cic((rq)->elv.icq)
+#define RQ_CFQQ(rq)             (struct cfq_queue *) ((rq)->elv.priv[0])
+#define RQ_CFQG(rq)             (struct cfq_group *) ((rq)->elv.priv[1])
 
 static struct kmem_cache *cfq_pool;
 static struct kmem_cache *cfq_icq_pool;
@@ -297,8 +297,6 @@ struct cfq_data {
         unsigned int cfq_group_idle;
         unsigned int cfq_latency;
 
-        struct list_head icq_list;
-
         /*
          * Fallback dummy cfqq for extreme OOM conditions
          */
@@ -3053,7 +3051,7 @@ static int cfq_create_cic(struct cfq_data *cfqd, gfp_t gfp_mask)
         ret = radix_tree_insert(&ioc->icq_tree, q->id, icq);
         if (likely(!ret)) {
                 hlist_add_head(&icq->ioc_node, &ioc->icq_list);
-                list_add(&icq->q_node, &cfqd->icq_list);
+                list_add(&icq->q_node, &q->icq_list);
                 icq = NULL;
         } else if (ret == -EEXIST) {
                 /* someone else already did it */
@@ -3605,12 +3603,10 @@ static void cfq_put_request(struct request *rq)
 
                 put_io_context(RQ_CIC(rq)->icq.ioc, cfqq->cfqd->queue);
 
-                rq->elevator_private[0] = NULL;
-                rq->elevator_private[1] = NULL;
-
                 /* Put down rq reference on cfqg */
                 cfq_put_cfqg(RQ_CFQG(rq));
-                rq->elevator_private[2] = NULL;
+                rq->elv.priv[0] = NULL;
+                rq->elv.priv[1] = NULL;
 
                 cfq_put_queue(cfqq);
         }
@@ -3696,9 +3692,9 @@ new_queue:
         cfqq->allocated[rw]++;
 
         cfqq->ref++;
-        rq->elevator_private[0] = &cic->icq;
-        rq->elevator_private[1] = cfqq;
-        rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
+        rq->elv.icq = &cic->icq;
+        rq->elv.priv[0] = cfqq;
+        rq->elv.priv[1] = cfq_ref_get_cfqg(cfqq->cfqg);
         spin_unlock_irq(q->queue_lock);
         return 0;
 
@@ -3810,8 +3806,8 @@ static void cfq_exit_queue(struct elevator_queue *e)
         if (cfqd->active_queue)
                 __cfq_slice_expired(cfqd, cfqd->active_queue, 0);
 
-        while (!list_empty(&cfqd->icq_list)) {
-                struct io_cq *icq = list_entry(cfqd->icq_list.next,
+        while (!list_empty(&q->icq_list)) {
+                struct io_cq *icq = list_entry(q->icq_list.next,
                                                struct io_cq, q_node);
                 struct io_context *ioc = icq->ioc;
 
@@ -3922,8 +3918,6 @@ static void *cfq_init_queue(struct request_queue *q)
         cfqd->oom_cfqq.ref++;
         cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
 
-        INIT_LIST_HEAD(&cfqd->icq_list);
-
         cfqd->queue = q;
 
         init_timer(&cfqd->idle_slice_timer);
diff --git a/block/elevator.c b/block/elevator.c
index 31ffe76aed3d..c5c6214829cb 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -745,8 +745,6 @@ int elv_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
 
         if (e->type->ops.elevator_set_req_fn)
                 return e->type->ops.elevator_set_req_fn(q, rq, gfp_mask);
-
-        rq->elevator_private[0] = NULL;
         return 0;
 }