[PATCH] 02/05: update ioscheds to use generic dispatch queue

This patch updates all four ioscheds to use generic dispatch
queue.  There's one behavior change in as-iosched.

* In as-iosched, when force dispatching
  (ELEVATOR_INSERT_BACK), batch_data_dir is reset to REQ_SYNC
  and changed_batch and new_batch are cleared to zero.  This
  prevernts AS from doing incorrect update_write_batch after
  the forced dispatched requests are finished.

* In cfq-iosched, cfqd->rq_in_driver currently counts the
  number of activated (removed) requests to determine
  whether queue-kicking is needed and cfq_max_depth has been
  reached.  With generic dispatch queue, I think counting
  the number of dispatched requests would be more appropriate.

* cfq_max_depth can be lowered to 1 again.

Original from Tejun Heo, modified version applied.

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

4 files changed, 187 insertions, 555 deletions

diff --git a/drivers/block/as-iosched.c b/drivers/block/as-iosched.c
index 95c0a3690b0f..1775ffe9edc7 100644
--- a/drivers/block/as-iosched.c
+++ b/drivers/block/as-iosched.c
@@ -98,7 +98,6 @@ struct as_data {
 
         struct as_rq *next_arq[2];      /* next in sort order */
         sector_t last_sector[2];        /* last REQ_SYNC & REQ_ASYNC sectors */
-        struct list_head *dispatch;     /* driver dispatch queue */
         struct list_head *hash;         /* request hash */
 
         unsigned long exit_prob;        /* probability a task will exit while
@@ -239,6 +238,25 @@ static struct io_context *as_get_io_context(void)
         return ioc;
 }
 
+static void as_put_io_context(struct as_rq *arq)
+{
+        struct as_io_context *aic;
+
+        if (unlikely(!arq->io_context))
+                return;
+
+        aic = arq->io_context->aic;
+
+        if (arq->is_sync == REQ_SYNC && aic) {
+                spin_lock(&aic->lock);
+                set_bit(AS_TASK_IORUNNING, &aic->state);
+                aic->last_end_request = jiffies;
+                spin_unlock(&aic->lock);
+        }
+
+        put_io_context(arq->io_context);
+}
+
 /*
  * the back merge hash support functions
  */
@@ -950,23 +968,12 @@ static void as_completed_request(request_queue_t *q, struct request *rq)
 
         WARN_ON(!list_empty(&rq->queuelist));
 
-        if (arq->state == AS_RQ_PRESCHED) {
-                WARN_ON(arq->io_context);
-                goto out;
-        }
-
-        if (arq->state == AS_RQ_MERGED)
-                goto out_ioc;
-
         if (arq->state != AS_RQ_REMOVED) {
                 printk("arq->state %d\n", arq->state);
                 WARN_ON(1);
                 goto out;
         }
 
-        if (!blk_fs_request(rq))
-                goto out;
-
         if (ad->changed_batch && ad->nr_dispatched == 1) {
                 kblockd_schedule_work(&ad->antic_work);
                 ad->changed_batch = 0;
@@ -1001,21 +1008,7 @@ static void as_completed_request(request_queue_t *q, struct request *rq)
                 }
         }
 
-out_ioc:
-        if (!arq->io_context)
-                goto out;
-
-        if (arq->is_sync == REQ_SYNC) {
-                struct as_io_context *aic = arq->io_context->aic;
-                if (aic) {
-                        spin_lock(&aic->lock);
-                        set_bit(AS_TASK_IORUNNING, &aic->state);
-                        aic->last_end_request = jiffies;
-                        spin_unlock(&aic->lock);
-                }
-        }
-
-        put_io_context(arq->io_context);
+        as_put_io_context(arq);
 out:
         arq->state = AS_RQ_POSTSCHED;
 }
@@ -1052,68 +1045,6 @@ static void as_remove_queued_request(request_queue_t *q, struct request *rq)
 }
 
 /*
- * as_remove_dispatched_request is called to remove a request which has gone
- * to the dispatch list.
- */
-static void as_remove_dispatched_request(request_queue_t *q, struct request *rq)
-{
-        struct as_rq *arq = RQ_DATA(rq);
-        struct as_io_context *aic;
-
-        if (!arq) {
-                WARN_ON(1);
-                return;
-        }
-
-        WARN_ON(arq->state != AS_RQ_DISPATCHED);
-        WARN_ON(ON_RB(&arq->rb_node));
-        if (arq->io_context && arq->io_context->aic) {
-                aic = arq->io_context->aic;
-                if (aic) {
-                        WARN_ON(!atomic_read(&aic->nr_dispatched));
-                        atomic_dec(&aic->nr_dispatched);
-                }
-        }
-}
-
-/*
- * as_remove_request is called when a driver has finished with a request.
- * This should be only called for dispatched requests, but for some reason
- * a POWER4 box running hwscan it does not.
- */
-static void as_remove_request(request_queue_t *q, struct request *rq)
-{
-        struct as_rq *arq = RQ_DATA(rq);
-
-        if (unlikely(arq->state == AS_RQ_NEW))
-                goto out;
-
-        if (ON_RB(&arq->rb_node)) {
-                if (arq->state != AS_RQ_QUEUED) {
-                        printk("arq->state %d\n", arq->state);
-                        WARN_ON(1);
-                        goto out;
-                }
-                /*
-                 * We'll lose the aliased request(s) here. I don't think this
-                 * will ever happen, but if it does, hopefully someone will
-                 * report it.
-                 */
-                WARN_ON(!list_empty(&rq->queuelist));
-                as_remove_queued_request(q, rq);
-        } else {
-                if (arq->state != AS_RQ_DISPATCHED) {
-                        printk("arq->state %d\n", arq->state);
-                        WARN_ON(1);
-                        goto out;
-                }
-                as_remove_dispatched_request(q, rq);
-        }
-out:
-        arq->state = AS_RQ_REMOVED;
-}
-
-/*
  * as_fifo_expired returns 0 if there are no expired reads on the fifo,
  * 1 otherwise.  It is ratelimited so that we only perform the check once per
  * `fifo_expire' interval.  Otherwise a large number of expired requests
@@ -1165,7 +1096,6 @@ static inline int as_batch_expired(struct as_data *ad)
 static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
 {
         struct request *rq = arq->request;
-        struct list_head *insert;
         const int data_dir = arq->is_sync;
 
         BUG_ON(!ON_RB(&arq->rb_node));
@@ -1198,13 +1128,13 @@ static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
         /*
          * take it off the sort and fifo list, add to dispatch queue
          */
-        insert = ad->dispatch->prev;
-
         while (!list_empty(&rq->queuelist)) {
                 struct request *__rq = list_entry_rq(rq->queuelist.next);
                 struct as_rq *__arq = RQ_DATA(__rq);
 
-                list_move_tail(&__rq->queuelist, ad->dispatch);
+                list_del(&__rq->queuelist);
+
+                elv_dispatch_add_tail(ad->q, __rq);
 
                 if (__arq->io_context && __arq->io_context->aic)
                         atomic_inc(&__arq->io_context->aic->nr_dispatched);
@@ -1218,7 +1148,8 @@ static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
         as_remove_queued_request(ad->q, rq);
         WARN_ON(arq->state != AS_RQ_QUEUED);
 
-        list_add(&rq->queuelist, insert);
+        elv_dispatch_sort(ad->q, rq);
+
         arq->state = AS_RQ_DISPATCHED;
         if (arq->io_context && arq->io_context->aic)
                 atomic_inc(&arq->io_context->aic->nr_dispatched);
@@ -1230,12 +1161,42 @@ static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
  * read/write expire, batch expire, etc, and moves it to the dispatch
  * queue. Returns 1 if a request was found, 0 otherwise.
  */
-static int as_dispatch_request(struct as_data *ad)
+static int as_dispatch_request(request_queue_t *q, int force)
 {
+        struct as_data *ad = q->elevator->elevator_data;
         struct as_rq *arq;
         const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]);
         const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]);
 
+        if (unlikely(force)) {
+                /*
+                 * Forced dispatch, accounting is useless.  Reset
+                 * accounting states and dump fifo_lists.  Note that
+                 * batch_data_dir is reset to REQ_SYNC to avoid
+                 * screwing write batch accounting as write batch
+                 * accounting occurs on W->R transition.
+                 */
+                int dispatched = 0;
+
+                ad->batch_data_dir = REQ_SYNC;
+                ad->changed_batch = 0;
+                ad->new_batch = 0;
+
+                while (ad->next_arq[REQ_SYNC]) {
+                        as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
+                        dispatched++;
+                }
+                ad->last_check_fifo[REQ_SYNC] = jiffies;
+
+                while (ad->next_arq[REQ_ASYNC]) {
+                        as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
+                        dispatched++;
+                }
+                ad->last_check_fifo[REQ_ASYNC] = jiffies;
+
+                return dispatched;
+        }
+
         /* Signal that the write batch was uncontended, so we can't time it */
         if (ad->batch_data_dir == REQ_ASYNC && !reads) {
                 if (ad->current_write_count == 0 || !writes)
@@ -1359,20 +1320,6 @@ fifo_expired:
         return 1;
 }
 
-static struct request *as_next_request(request_queue_t *q)
-{
-        struct as_data *ad = q->elevator->elevator_data;
-        struct request *rq = NULL;
-
-        /*
-         * if there are still requests on the dispatch queue, grab the first
-         */
-        if (!list_empty(ad->dispatch) || as_dispatch_request(ad))
-                rq = list_entry_rq(ad->dispatch->next);
-
-        return rq;
-}
-
 /*
  * Add arq to a list behind alias
  */
@@ -1410,11 +1357,19 @@ as_add_aliased_request(struct as_data *ad, struct as_rq *arq, struct as_rq *alia
 /*
  * add arq to rbtree and fifo
  */
-static void as_add_request(struct as_data *ad, struct as_rq *arq)
+static void as_add_request(request_queue_t *q, struct request *rq)
 {
+        struct as_data *ad = q->elevator->elevator_data;
+        struct as_rq *arq = RQ_DATA(rq);
         struct as_rq *alias;
         int data_dir;
 
+        if (arq->state != AS_RQ_PRESCHED) {
+                printk("arq->state: %d\n", arq->state);
+                WARN_ON(1);
+        }
+        arq->state = AS_RQ_NEW;
+
         if (rq_data_dir(arq->request) == READ
                         || current->flags&PF_SYNCWRITE)
                 arq->is_sync = 1;
@@ -1463,96 +1418,24 @@ static void as_add_request(struct as_data *ad, struct as_rq *arq)
         arq->state = AS_RQ_QUEUED;
 }
 
-static void as_deactivate_request(request_queue_t *q, struct request *rq)
+static void as_activate_request(request_queue_t *q, struct request *rq)
 {
-        struct as_data *ad = q->elevator->elevator_data;
         struct as_rq *arq = RQ_DATA(rq);
 
-        if (arq) {
-                if (arq->state == AS_RQ_REMOVED) {
-                        arq->state = AS_RQ_DISPATCHED;
-                        if (arq->io_context && arq->io_context->aic)
-                                atomic_inc(&arq->io_context->aic->nr_dispatched);
-                }
-        } else
-                WARN_ON(blk_fs_request(rq)
-                        && (!(rq->flags & (REQ_HARDBARRIER|REQ_SOFTBARRIER))) );
-
-        /* Stop anticipating - let this request get through */
-        as_antic_stop(ad);
-}
-
-/*
- * requeue the request. The request has not been completed, nor is it a
- * new request, so don't touch accounting.
- */
-static void as_requeue_request(request_queue_t *q, struct request *rq)
-{
-        as_deactivate_request(q, rq);
-        list_add(&rq->queuelist, &q->queue_head);
-}
-
-/*
- * Account a request that is inserted directly onto the dispatch queue.
- * arq->io_context->aic->nr_dispatched should not need to be incremented
- * because only new requests should come through here: requeues go through
- * our explicit requeue handler.
- */
-static void as_account_queued_request(struct as_data *ad, struct request *rq)
-{
-        if (blk_fs_request(rq)) {
-                struct as_rq *arq = RQ_DATA(rq);
-                arq->state = AS_RQ_DISPATCHED;
-                ad->nr_dispatched++;
-        }
+        WARN_ON(arq->state != AS_RQ_DISPATCHED);
+        arq->state = AS_RQ_REMOVED;
+        if (arq->io_context && arq->io_context->aic)
+                atomic_dec(&arq->io_context->aic->nr_dispatched);
 }
 
-static void
-as_insert_request(request_queue_t *q, struct request *rq, int where)
+static void as_deactivate_request(request_queue_t *q, struct request *rq)
 {
-        struct as_data *ad = q->elevator->elevator_data;
         struct as_rq *arq = RQ_DATA(rq);
 
-        if (arq) {
-                if (arq->state != AS_RQ_PRESCHED) {
-                        printk("arq->state: %d\n", arq->state);
-                        WARN_ON(1);
-                }
-                arq->state = AS_RQ_NEW;
-        }
-
-        /* barriers must flush the reorder queue */
-        if (unlikely(rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)
-                        && where == ELEVATOR_INSERT_SORT)) {
-                WARN_ON(1);
-                where = ELEVATOR_INSERT_BACK;
-        }
-
-        switch (where) {
-                case ELEVATOR_INSERT_BACK:
-                        while (ad->next_arq[REQ_SYNC])
-                                as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
-
-                        while (ad->next_arq[REQ_ASYNC])
-                                as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
-
-                        list_add_tail(&rq->queuelist, ad->dispatch);
-                        as_account_queued_request(ad, rq);
-                        as_antic_stop(ad);
-                        break;
-                case ELEVATOR_INSERT_FRONT:
-                        list_add(&rq->queuelist, ad->dispatch);
-                        as_account_queued_request(ad, rq);
-                        as_antic_stop(ad);
-                        break;
-                case ELEVATOR_INSERT_SORT:
-                        BUG_ON(!blk_fs_request(rq));
-                        as_add_request(ad, arq);
-                        break;
-                default:
-                        BUG();
-                        return;
-        }
+        WARN_ON(arq->state != AS_RQ_REMOVED);
+        arq->state = AS_RQ_DISPATCHED;
+        if (arq->io_context && arq->io_context->aic)
+                atomic_inc(&arq->io_context->aic->nr_dispatched);
 }
 
 /*
@@ -1565,12 +1448,8 @@ static int as_queue_empty(request_queue_t *q)
 {
         struct as_data *ad = q->elevator->elevator_data;
 
-        if (!list_empty(&ad->fifo_list[REQ_ASYNC])
-                || !list_empty(&ad->fifo_list[REQ_SYNC])
-                || !list_empty(ad->dispatch))
-                        return 0;
-
-        return 1;
+        return list_empty(&ad->fifo_list[REQ_ASYNC])
+                && list_empty(&ad->fifo_list[REQ_SYNC]);
 }
 
 static struct request *
@@ -1763,6 +1642,7 @@ as_merged_requests(request_queue_t *q, struct request *req,
          * kill knowledge of next, this one is a goner
          */
         as_remove_queued_request(q, next);
+        as_put_io_context(anext);
 
         anext->state = AS_RQ_MERGED;
 }
@@ -1782,7 +1662,7 @@ static void as_work_handler(void *data)
         unsigned long flags;
 
         spin_lock_irqsave(q->queue_lock, flags);
-        if (as_next_request(q))
+        if (!as_queue_empty(q))
                 q->request_fn(q);
         spin_unlock_irqrestore(q->queue_lock, flags);
 }
@@ -1797,7 +1677,9 @@ static void as_put_request(request_queue_t *q, struct request *rq)
                 return;
         }
 
-        if (arq->state != AS_RQ_POSTSCHED && arq->state != AS_RQ_PRESCHED) {
+        if (unlikely(arq->state != AS_RQ_POSTSCHED &&
+                     arq->state != AS_RQ_PRESCHED &&
+                     arq->state != AS_RQ_MERGED)) {
                 printk("arq->state %d\n", arq->state);
                 WARN_ON(1);
         }
@@ -1907,7 +1789,6 @@ static int as_init_queue(request_queue_t *q, elevator_t *e)
         INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]);
         ad->sort_list[REQ_SYNC] = RB_ROOT;
         ad->sort_list[REQ_ASYNC] = RB_ROOT;
-        ad->dispatch = &q->queue_head;
         ad->fifo_expire[REQ_SYNC] = default_read_expire;
         ad->fifo_expire[REQ_ASYNC] = default_write_expire;
         ad->antic_expire = default_antic_expire;
@@ -2072,10 +1953,9 @@ static struct elevator_type iosched_as = {
                 .elevator_merge_fn =            as_merge,
                 .elevator_merged_fn =           as_merged_request,
                 .elevator_merge_req_fn =        as_merged_requests,
-                .elevator_next_req_fn =         as_next_request,
-                .elevator_add_req_fn =          as_insert_request,
-                .elevator_remove_req_fn =       as_remove_request,
-                .elevator_requeue_req_fn =      as_requeue_request,
+                .elevator_dispatch_fn =         as_dispatch_request,
+                .elevator_add_req_fn =          as_add_request,
+                .elevator_activate_req_fn =     as_activate_request,
                 .elevator_deactivate_req_fn =   as_deactivate_request,
                 .elevator_queue_empty_fn =      as_queue_empty,
                 .elevator_completed_req_fn =    as_completed_request,
diff --git a/drivers/block/cfq-iosched.c b/drivers/block/cfq-iosched.c
index cd056e7e64ec..7b14160e0798 100644
--- a/drivers/block/cfq-iosched.c
+++ b/drivers/block/cfq-iosched.c
@@ -84,7 +84,6 @@ static int cfq_max_depth = 2;
         (node)->rb_left = NULL;         \
 } while (0)
 #define RB_CLEAR_ROOT(root)     ((root)->rb_node = NULL)
-#define ON_RB(node)             ((node)->rb_color != RB_NONE)
 #define rb_entry_crq(node)      rb_entry((node), struct cfq_rq, rb_node)
 #define rq_rb_key(rq)           (rq)->sector
 
@@ -271,10 +270,7 @@ CFQ_CFQQ_FNS(expired);
 #undef CFQ_CFQQ_FNS
 
 enum cfq_rq_state_flags {
-        CFQ_CRQ_FLAG_in_flight = 0,
-        CFQ_CRQ_FLAG_in_driver,
-        CFQ_CRQ_FLAG_is_sync,
-        CFQ_CRQ_FLAG_requeued,
+        CFQ_CRQ_FLAG_is_sync = 0,
 };
 
 #define CFQ_CRQ_FNS(name)                                               \
@@ -291,14 +287,11 @@ static inline int cfq_crq_##name(const struct cfq_rq *crq)		\
         return (crq->crq_flags & (1 << CFQ_CRQ_FLAG_##name)) != 0;      \
 }
 
-CFQ_CRQ_FNS(in_flight);
-CFQ_CRQ_FNS(in_driver);
 CFQ_CRQ_FNS(is_sync);
-CFQ_CRQ_FNS(requeued);
 #undef CFQ_CRQ_FNS
 
 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned int, unsigned short);
-static void cfq_dispatch_sort(request_queue_t *, struct cfq_rq *);
+static void cfq_dispatch_insert(request_queue_t *, struct cfq_rq *);
 static void cfq_put_cfqd(struct cfq_data *cfqd);
 
 #define process_sync(tsk)       ((tsk)->flags & PF_SYNCWRITE)
@@ -347,18 +340,13 @@ static struct request *cfq_find_rq_hash(struct cfq_data *cfqd, sector_t offset)
         return NULL;
 }
 
-static inline int cfq_pending_requests(struct cfq_data *cfqd)
-{
-        return !list_empty(&cfqd->queue->queue_head) || cfqd->busy_queues;
-}
-
 /*
  * scheduler run of queue, if there are requests pending and no one in the
  * driver that will restart queueing
  */
 static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
 {
-        if (!cfqd->rq_in_driver && cfq_pending_requests(cfqd))
+        if (!cfqd->rq_in_driver && cfqd->busy_queues)
                 kblockd_schedule_work(&cfqd->unplug_work);
 }
 
@@ -366,7 +354,7 @@ static int cfq_queue_empty(request_queue_t *q)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
 
-        return !cfq_pending_requests(cfqd);
+        return !cfqd->busy_queues;
 }
 
 /*
@@ -386,11 +374,6 @@ cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2)
         if (crq2 == NULL)
                 return crq1;
 
-        if (cfq_crq_requeued(crq1) && !cfq_crq_requeued(crq2))
-                return crq1;
-        else if (cfq_crq_requeued(crq2) && !cfq_crq_requeued(crq1))
-                return crq2;
-
         if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))
                 return crq1;
         else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
@@ -461,10 +444,7 @@ cfq_find_next_crq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         struct cfq_rq *crq_next = NULL, *crq_prev = NULL;
         struct rb_node *rbnext, *rbprev;
 
-        rbnext = NULL;
-        if (ON_RB(&last->rb_node))
-                rbnext = rb_next(&last->rb_node);
-        if (!rbnext) {
+        if (!(rbnext = rb_next(&last->rb_node))) {
                 rbnext = rb_first(&cfqq->sort_list);
                 if (rbnext == &last->rb_node)
                         rbnext = NULL;
@@ -545,13 +525,13 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
  * the pending list according to last request service
  */
 static inline void
-cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq, int requeue)
+cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
         BUG_ON(cfq_cfqq_on_rr(cfqq));
         cfq_mark_cfqq_on_rr(cfqq);
         cfqd->busy_queues++;
 
-        cfq_resort_rr_list(cfqq, requeue);
+        cfq_resort_rr_list(cfqq, 0);
 }
 
 static inline void
@@ -571,22 +551,19 @@ cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 static inline void cfq_del_crq_rb(struct cfq_rq *crq)
 {
         struct cfq_queue *cfqq = crq->cfq_queue;
+        struct cfq_data *cfqd = cfqq->cfqd;
+        const int sync = cfq_crq_is_sync(crq);
 
-        if (ON_RB(&crq->rb_node)) {
-                struct cfq_data *cfqd = cfqq->cfqd;
-                const int sync = cfq_crq_is_sync(crq);
-
-                BUG_ON(!cfqq->queued[sync]);
-                cfqq->queued[sync]--;
+        BUG_ON(!cfqq->queued[sync]);
+        cfqq->queued[sync]--;
 
-                cfq_update_next_crq(crq);
+        cfq_update_next_crq(crq);
 
-                rb_erase(&crq->rb_node, &cfqq->sort_list);
-                RB_CLEAR_COLOR(&crq->rb_node);
+        rb_erase(&crq->rb_node, &cfqq->sort_list);
+        RB_CLEAR_COLOR(&crq->rb_node);
 
-                if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list))
-                        cfq_del_cfqq_rr(cfqd, cfqq);
-        }
+        if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY(&cfqq->sort_list))
+                cfq_del_cfqq_rr(cfqd, cfqq);
 }
 
 static struct cfq_rq *
@@ -627,12 +604,12 @@ static void cfq_add_crq_rb(struct cfq_rq *crq)
          * if that happens, put the alias on the dispatch list
          */
         while ((__alias = __cfq_add_crq_rb(crq)) != NULL)
-                cfq_dispatch_sort(cfqd->queue, __alias);
+                cfq_dispatch_insert(cfqd->queue, __alias);
 
         rb_insert_color(&crq->rb_node, &cfqq->sort_list);
 
         if (!cfq_cfqq_on_rr(cfqq))
-                cfq_add_cfqq_rr(cfqd, cfqq, cfq_crq_requeued(crq));
+                cfq_add_cfqq_rr(cfqd, cfqq);
 
         /*
          * check if this request is a better next-serve candidate
@@ -643,10 +620,8 @@ static void cfq_add_crq_rb(struct cfq_rq *crq)
 static inline void
 cfq_reposition_crq_rb(struct cfq_queue *cfqq, struct cfq_rq *crq)
 {
-        if (ON_RB(&crq->rb_node)) {
-                rb_erase(&crq->rb_node, &cfqq->sort_list);
-                cfqq->queued[cfq_crq_is_sync(crq)]--;
-        }
+        rb_erase(&crq->rb_node, &cfqq->sort_list);
+        cfqq->queued[cfq_crq_is_sync(crq)]--;
 
         cfq_add_crq_rb(crq);
 }
@@ -676,49 +651,28 @@ out:
         return NULL;
 }
 
-static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
+static void cfq_activate_request(request_queue_t *q, struct request *rq)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
-        struct cfq_rq *crq = RQ_DATA(rq);
-
-        if (crq) {
-                struct cfq_queue *cfqq = crq->cfq_queue;
 
-                if (cfq_crq_in_driver(crq)) {
-                        cfq_clear_crq_in_driver(crq);
-                        WARN_ON(!cfqd->rq_in_driver);
-                        cfqd->rq_in_driver--;
-                }
-                if (cfq_crq_in_flight(crq)) {
-                        const int sync = cfq_crq_is_sync(crq);
-
-                        cfq_clear_crq_in_flight(crq);
-                        WARN_ON(!cfqq->on_dispatch[sync]);
-                        cfqq->on_dispatch[sync]--;
-                }
-                cfq_mark_crq_requeued(crq);
-        }
+        cfqd->rq_in_driver++;
 }
 
-/*
- * make sure the service time gets corrected on reissue of this request
- */
-static void cfq_requeue_request(request_queue_t *q, struct request *rq)
+static void cfq_deactivate_request(request_queue_t *q, struct request *rq)
 {
-        cfq_deactivate_request(q, rq);
-        list_add(&rq->queuelist, &q->queue_head);
+        struct cfq_data *cfqd = q->elevator->elevator_data;
+
+        WARN_ON(!cfqd->rq_in_driver);
+        cfqd->rq_in_driver--;
 }
 
-static void cfq_remove_request(request_queue_t *q, struct request *rq)
+static void cfq_remove_request(struct request *rq)
 {
         struct cfq_rq *crq = RQ_DATA(rq);
 
-        if (crq) {
-                list_del_init(&rq->queuelist);
-                cfq_del_crq_rb(crq);
-                cfq_remove_merge_hints(q, crq);
-
-        }
+        list_del_init(&rq->queuelist);
+        cfq_del_crq_rb(crq);
+        cfq_remove_merge_hints(rq->q, crq);
 }
 
 static int
@@ -762,7 +716,7 @@ static void cfq_merged_request(request_queue_t *q, struct request *req)
         cfq_del_crq_hash(crq);
         cfq_add_crq_hash(cfqd, crq);
 
-        if (ON_RB(&crq->rb_node) && (rq_rb_key(req) != crq->rb_key)) {
+        if (rq_rb_key(req) != crq->rb_key) {
                 struct cfq_queue *cfqq = crq->cfq_queue;
 
                 cfq_update_next_crq(crq);
@@ -785,7 +739,7 @@ cfq_merged_requests(request_queue_t *q, struct request *rq,
             time_before(next->start_time, rq->start_time))
                 list_move(&rq->queuelist, &next->queuelist);
 
-        cfq_remove_request(q, next);
+        cfq_remove_request(next);
 }
 
 static inline void
@@ -992,53 +946,15 @@ static int cfq_arm_slice_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
         return 1;
 }
 
-/*
- * we dispatch cfqd->cfq_quantum requests in total from the rr_list queues,
- * this function sector sorts the selected request to minimize seeks. we start
- * at cfqd->last_sector, not 0.
- */
-static void cfq_dispatch_sort(request_queue_t *q, struct cfq_rq *crq)
+static void cfq_dispatch_insert(request_queue_t *q, struct cfq_rq *crq)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct cfq_queue *cfqq = crq->cfq_queue;
-        struct list_head *head = &q->queue_head, *entry = head;
-        struct request *__rq;
-        sector_t last;
-
-        list_del(&crq->request->queuelist);
-
-        last = cfqd->last_sector;
-        list_for_each_entry_reverse(__rq, head, queuelist) {
-                struct cfq_rq *__crq = RQ_DATA(__rq);
-
-                if (blk_barrier_rq(__rq))
-                        break;
-                if (!blk_fs_request(__rq))
-                        break;
-                if (cfq_crq_requeued(__crq))
-                        break;
-
-                if (__rq->sector <= crq->request->sector)
-                        break;
-                if (__rq->sector > last && crq->request->sector < last) {
-                        last = crq->request->sector + crq->request->nr_sectors;
-                        break;
-                }
-                entry = &__rq->queuelist;
-        }
-
-        cfqd->last_sector = last;
 
         cfqq->next_crq = cfq_find_next_crq(cfqd, cfqq, crq);
-
-        cfq_del_crq_rb(crq);
-        cfq_remove_merge_hints(q, crq);
-
-        cfq_mark_crq_in_flight(crq);
-        cfq_clear_crq_requeued(crq);
-
+        cfq_remove_request(crq->request);
         cfqq->on_dispatch[cfq_crq_is_sync(crq)]++;
-        list_add_tail(&crq->request->queuelist, entry);
+        elv_dispatch_sort(q, crq->request);
 }
 
 /*
@@ -1159,7 +1075,7 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
                 /*
                  * finally, insert request into driver dispatch list
                  */
-                cfq_dispatch_sort(cfqd->queue, crq);
+                cfq_dispatch_insert(cfqd->queue, crq);
 
                 cfqd->dispatch_slice++;
                 dispatched++;
@@ -1194,7 +1110,7 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 }
 
 static int
-cfq_dispatch_requests(request_queue_t *q, int max_dispatch, int force)
+cfq_dispatch_requests(request_queue_t *q, int force)
 {
         struct cfq_data *cfqd = q->elevator->elevator_data;
         struct cfq_queue *cfqq;
@@ -1204,12 +1120,25 @@ cfq_dispatch_requests(request_queue_t *q, int max_dispatch, int force)
 
         cfqq = cfq_select_queue(cfqd, force);
         if (cfqq) {
+                int max_dispatch;
+
+                /*
+                 * if idle window is disabled, allow queue buildup
+                 */
+                if (!cfq_cfqq_idle_window(cfqq) &&
+                    cfqd->rq_in_driver >= cfqd->cfq_max_depth)
+                        return 0;
+
                 cfq_clear_cfqq_must_dispatch(cfqq);
                 cfq_clear_cfqq_wait_request(cfqq);
                 del_timer(&cfqd->idle_slice_timer);
 
-                if (cfq_class_idle(cfqq))
-                        max_dispatch = 1;
+                if (!force) {
+                        max_dispatch = cfqd->cfq_quantum;
+                        if (cfq_class_idle(cfqq))
+                                max_dispatch = 1;
+                } else
+                        max_dispatch = INT_MAX;
 
                 return __cfq_dispatch_requests(cfqd, cfqq, max_dispatch);
         }
@@ -1217,93 +1146,6 @@ cfq_dispatch_requests(request_queue_t *q, int max_dispatch, int force)
         return 0;
 }
 
-static inline void cfq_account_dispatch(struct cfq_rq *crq)
-{
-        struct cfq_queue *cfqq = crq->cfq_queue;
-        struct cfq_data *cfqd = cfqq->cfqd;
-
-        if (unlikely(!blk_fs_request(crq->request)))
-                return;
-
-        /*
-         * accounted bit is necessary since some drivers will call
-         * elv_next_request() many times for the same request (eg ide)
-         */
-        if (cfq_crq_in_driver(crq))
-                return;
-
-        cfq_mark_crq_in_driver(crq);
-        cfqd->rq_in_driver++;
-}
-
-static inline void
-cfq_account_completion(struct cfq_queue *cfqq, struct cfq_rq *crq)
-{
-        struct cfq_data *cfqd = cfqq->cfqd;
-        unsigned long now;
-
-        if (!cfq_crq_in_driver(crq))
-                return;
-
-        now = jiffies;
-
-        WARN_ON(!cfqd->rq_in_driver);
-        cfqd->rq_in_driver--;
-
-        if (!cfq_class_idle(cfqq))
-                cfqd->last_end_request = now;
-
-        if (!cfq_cfqq_dispatched(cfqq)) {
-                if (cfq_cfqq_on_rr(cfqq)) {
-                        cfqq->service_last = now;
-                        cfq_resort_rr_list(cfqq, 0);
-                }
-                if (cfq_cfqq_expired(cfqq)) {
-                        __cfq_slice_expired(cfqd, cfqq, 0);
-                        cfq_schedule_dispatch(cfqd);
-                }
-        }
-
-        if (cfq_crq_is_sync(crq))
-                crq->io_context->last_end_request = now;
-}
-
-static struct request *cfq_next_request(request_queue_t *q)
-{
-        struct cfq_data *cfqd = q->elevator->elevator_data;
-        struct request *rq;
-
-        if (!list_empty(&q->queue_head)) {
-                struct cfq_rq *crq;
-dispatch:
-                rq = list_entry_rq(q->queue_head.next);
-
-                crq = RQ_DATA(rq);
-                if (crq) {
-                        struct cfq_queue *cfqq = crq->cfq_queue;
-
-                        /*
-                         * if idle window is disabled, allow queue buildup
-                         */
-                        if (!cfq_crq_in_driver(crq) &&
-                            !cfq_cfqq_idle_window(cfqq) &&
-                            !blk_barrier_rq(rq) &&
-                            cfqd->rq_in_driver >= cfqd->cfq_max_depth)
-                                return NULL;
-
-                        cfq_remove_merge_hints(q, crq);
-                        cfq_account_dispatch(crq);
-                }
-
-                return rq;
-        }
-
-        if (cfq_dispatch_requests(q, cfqd->cfq_quantum, 0))
-                goto dispatch;
-
-        return NULL;
-}
-
 /*
  * task holds one reference to the queue, dropped when task exits. each crq
  * in-flight on this queue also holds a reference, dropped when crq is freed.
@@ -1816,8 +1658,9 @@ cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         }
 }
 
-static void cfq_enqueue(struct cfq_data *cfqd, struct request *rq)
+static void cfq_insert_request(request_queue_t *q, struct request *rq)
 {
+        struct cfq_data *cfqd = q->elevator->elevator_data;
         struct cfq_rq *crq = RQ_DATA(rq);
         struct cfq_queue *cfqq = crq->cfq_queue;
 
@@ -1837,56 +1680,37 @@ static void cfq_enqueue(struct cfq_data *cfqd, struct request *rq)
         cfq_crq_enqueued(cfqd, cfqq, crq);
 }
 
-static void
-cfq_insert_request(request_queue_t *q, struct request *rq, int where)
-{
-        struct cfq_data *cfqd = q->elevator->elevator_data;
-
-        switch (where) {
-                case ELEVATOR_INSERT_BACK:
-                        while (cfq_dispatch_requests(q, INT_MAX, 1))
-                                ;
-                        list_add_tail(&rq->queuelist, &q->queue_head);
-                        /*
-                         * If we were idling with pending requests on
-                         * inactive cfqqs, force dispatching will
-                         * remove the idle timer and the queue won't
-                         * be kicked by __make_request() afterward.
-                         * Kick it here.
-                         */
-                        cfq_schedule_dispatch(cfqd);
-                        break;
-                case ELEVATOR_INSERT_FRONT:
-                        list_add(&rq->queuelist, &q->queue_head);
-                        break;
-                case ELEVATOR_INSERT_SORT:
-                        BUG_ON(!blk_fs_request(rq));
-                        cfq_enqueue(cfqd, rq);
-                        break;
-                default:
-                        printk("%s: bad insert point %d\n", __FUNCTION__,where);
-                        return;
-        }
-}
-
 static void cfq_completed_request(request_queue_t *q, struct request *rq)
 {
         struct cfq_rq *crq = RQ_DATA(rq);
-        struct cfq_queue *cfqq;
+        struct cfq_queue *cfqq = crq->cfq_queue;
+        struct cfq_data *cfqd = cfqq->cfqd;
+        const int sync = cfq_crq_is_sync(crq);
+        unsigned long now;
 
-        if (unlikely(!blk_fs_request(rq)))
-                return;
+        now = jiffies;
 
-        cfqq = crq->cfq_queue;
+        WARN_ON(!cfqd->rq_in_driver);
+        WARN_ON(!cfqq->on_dispatch[sync]);
+        cfqd->rq_in_driver--;
+        cfqq->on_dispatch[sync]--;
 
-        if (cfq_crq_in_flight(crq)) {
-                const int sync = cfq_crq_is_sync(crq);
+        if (!cfq_class_idle(cfqq))
+                cfqd->last_end_request = now;
 
-                WARN_ON(!cfqq->on_dispatch[sync]);
-                cfqq->on_dispatch[sync]--;
+        if (!cfq_cfqq_dispatched(cfqq)) {
+                if (cfq_cfqq_on_rr(cfqq)) {
+                        cfqq->service_last = now;
+                        cfq_resort_rr_list(cfqq, 0);
+                }
+                if (cfq_cfqq_expired(cfqq)) {
+                        __cfq_slice_expired(cfqd, cfqq, 0);
+                        cfq_schedule_dispatch(cfqd);
+                }
         }
 
-        cfq_account_completion(cfqq, crq);
+        if (cfq_crq_is_sync(crq))
+                crq->io_context->last_end_request = now;
 }
 
 static struct request *
@@ -2118,9 +1942,6 @@ cfq_set_request(request_queue_t *q, struct request *rq, struct bio *bio,
                 INIT_HLIST_NODE(&crq->hash);
                 crq->cfq_queue = cfqq;
                 crq->io_context = cic;
-                cfq_clear_crq_in_flight(crq);
-                cfq_clear_crq_in_driver(crq);
-                cfq_clear_crq_requeued(crq);
 
                 if (rw == READ || process_sync(tsk))
                         cfq_mark_crq_is_sync(crq);
@@ -2201,7 +2022,7 @@ static void cfq_idle_slice_timer(unsigned long data)
                  * only expire and reinvoke request handler, if there are
                  * other queues with pending requests
                  */
-                if (!cfq_pending_requests(cfqd)) {
+                if (!cfqd->busy_queues) {
                         cfqd->idle_slice_timer.expires = min(now + cfqd->cfq_slice_idle, cfqq->slice_end);
                         add_timer(&cfqd->idle_slice_timer);
                         goto out_cont;
@@ -2576,10 +2397,9 @@ static struct elevator_type iosched_cfq = {
                 .elevator_merge_fn =            cfq_merge,
                 .elevator_merged_fn =           cfq_merged_request,
                 .elevator_merge_req_fn =        cfq_merged_requests,
-                .elevator_next_req_fn =         cfq_next_request,
+                .elevator_dispatch_fn =         cfq_dispatch_requests,
                 .elevator_add_req_fn =          cfq_insert_request,
-                .elevator_remove_req_fn =       cfq_remove_request,
-                .elevator_requeue_req_fn =      cfq_requeue_request,
+                .elevator_activate_req_fn =     cfq_activate_request,
                 .elevator_deactivate_req_fn =   cfq_deactivate_request,
                 .elevator_queue_empty_fn =      cfq_queue_empty,
                 .elevator_completed_req_fn =    cfq_completed_request,
diff --git a/drivers/block/deadline-iosched.c b/drivers/block/deadline-iosched.c
index 52a3ae5289a0..07de4d24ddba 100644
--- a/drivers/block/deadline-iosched.c
+++ b/drivers/block/deadline-iosched.c
@@ -50,7 +50,6 @@ struct deadline_data {
          * next in sort order. read, write or both are NULL
          */
         struct deadline_rq *next_drq[2];
-        struct list_head *dispatch;     /* driver dispatch queue */
         struct list_head *hash;         /* request hash */
         unsigned int batching;          /* number of sequential requests made */
         sector_t last_sector;           /* head position */
@@ -239,10 +238,9 @@ deadline_del_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
                         dd->next_drq[data_dir] = rb_entry_drq(rbnext);
         }
 
-        if (ON_RB(&drq->rb_node)) {
-                rb_erase(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
-                RB_CLEAR(&drq->rb_node);
-        }
+        BUG_ON(!ON_RB(&drq->rb_node));
+        rb_erase(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
+        RB_CLEAR(&drq->rb_node);
 }
 
 static struct request *
@@ -286,7 +284,7 @@ deadline_find_first_drq(struct deadline_data *dd, int data_dir)
 /*
  * add drq to rbtree and fifo
  */
-static inline void
+static void
 deadline_add_request(struct request_queue *q, struct request *rq)
 {
         struct deadline_data *dd = q->elevator->elevator_data;
@@ -315,14 +313,11 @@ deadline_add_request(struct request_queue *q, struct request *rq)
 static void deadline_remove_request(request_queue_t *q, struct request *rq)
 {
         struct deadline_rq *drq = RQ_DATA(rq);
+        struct deadline_data *dd = q->elevator->elevator_data;
 
-        if (drq) {
-                struct deadline_data *dd = q->elevator->elevator_data;
-
-                list_del_init(&drq->fifo);
-                deadline_remove_merge_hints(q, drq);
-                deadline_del_drq_rb(dd, drq);
-        }
+        list_del_init(&drq->fifo);
+        deadline_remove_merge_hints(q, drq);
+        deadline_del_drq_rb(dd, drq);
 }
 
 static int
@@ -452,7 +447,7 @@ deadline_move_to_dispatch(struct deadline_data *dd, struct deadline_rq *drq)
         request_queue_t *q = drq->request->q;
 
         deadline_remove_request(q, drq->request);
-        list_add_tail(&drq->request->queuelist, dd->dispatch);
+        elv_dispatch_add_tail(q, drq->request);
 }
 
 /*
@@ -502,8 +497,9 @@ static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
  * deadline_dispatch_requests selects the best request according to
  * read/write expire, fifo_batch, etc
  */
-static int deadline_dispatch_requests(struct deadline_data *dd)
+static int deadline_dispatch_requests(request_queue_t *q, int force)
 {
+        struct deadline_data *dd = q->elevator->elevator_data;
         const int reads = !list_empty(&dd->fifo_list[READ]);
         const int writes = !list_empty(&dd->fifo_list[WRITE]);
         struct deadline_rq *drq;
@@ -597,65 +593,12 @@ dispatch_request:
         return 1;
 }
 
-static struct request *deadline_next_request(request_queue_t *q)
-{
-        struct deadline_data *dd = q->elevator->elevator_data;
-        struct request *rq;
-
-        /*
-         * if there are still requests on the dispatch queue, grab the first one
-         */
-        if (!list_empty(dd->dispatch)) {
-dispatch:
-                rq = list_entry_rq(dd->dispatch->next);
-                return rq;
-        }
-
-        if (deadline_dispatch_requests(dd))
-                goto dispatch;
-
-        return NULL;
-}
-
-static void
-deadline_insert_request(request_queue_t *q, struct request *rq, int where)
-{
-        struct deadline_data *dd = q->elevator->elevator_data;
-
-        /* barriers must flush the reorder queue */
-        if (unlikely(rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)
-                        && where == ELEVATOR_INSERT_SORT))
-                where = ELEVATOR_INSERT_BACK;
-
-        switch (where) {
-                case ELEVATOR_INSERT_BACK:
-                        while (deadline_dispatch_requests(dd))
-                                ;
-                        list_add_tail(&rq->queuelist, dd->dispatch);
-                        break;
-                case ELEVATOR_INSERT_FRONT:
-                        list_add(&rq->queuelist, dd->dispatch);
-                        break;
-                case ELEVATOR_INSERT_SORT:
-                        BUG_ON(!blk_fs_request(rq));
-                        deadline_add_request(q, rq);
-                        break;
-                default:
-                        printk("%s: bad insert point %d\n", __FUNCTION__,where);
-                        return;
-        }
-}
-
 static int deadline_queue_empty(request_queue_t *q)
 {
         struct deadline_data *dd = q->elevator->elevator_data;
 
-        if (!list_empty(&dd->fifo_list[WRITE])
-            || !list_empty(&dd->fifo_list[READ])
-            || !list_empty(dd->dispatch))
-                return 0;
-
-        return 1;
+        return list_empty(&dd->fifo_list[WRITE])
+                && list_empty(&dd->fifo_list[READ]);
 }
 
 static struct request *
@@ -733,7 +676,6 @@ static int deadline_init_queue(request_queue_t *q, elevator_t *e)
         INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
         dd->sort_list[READ] = RB_ROOT;
         dd->sort_list[WRITE] = RB_ROOT;
-        dd->dispatch = &q->queue_head;
         dd->fifo_expire[READ] = read_expire;
         dd->fifo_expire[WRITE] = write_expire;
         dd->writes_starved = writes_starved;
@@ -748,10 +690,8 @@ static void deadline_put_request(request_queue_t *q, struct request *rq)
         struct deadline_data *dd = q->elevator->elevator_data;
         struct deadline_rq *drq = RQ_DATA(rq);
 
-        if (drq) {
-                mempool_free(drq, dd->drq_pool);
-                rq->elevator_private = NULL;
-        }
+        mempool_free(drq, dd->drq_pool);
+        rq->elevator_private = NULL;
 }
 
 static int
@@ -917,9 +857,8 @@ static struct elevator_type iosched_deadline = {
                 .elevator_merge_fn =            deadline_merge,
                 .elevator_merged_fn =           deadline_merged_request,
                 .elevator_merge_req_fn =        deadline_merged_requests,
-                .elevator_next_req_fn =         deadline_next_request,
-                .elevator_add_req_fn =          deadline_insert_request,
-                .elevator_remove_req_fn =       deadline_remove_request,
+                .elevator_dispatch_fn =         deadline_dispatch_requests,
+                .elevator_add_req_fn =          deadline_add_request,
                 .elevator_queue_empty_fn =      deadline_queue_empty,
                 .elevator_former_req_fn =       deadline_former_request,
                 .elevator_latter_req_fn =       deadline_latter_request,
diff --git a/drivers/block/noop-iosched.c b/drivers/block/noop-iosched.c
index b1730b62c37e..bc2252b6f2e5 100644
--- a/drivers/block/noop-iosched.c
+++ b/drivers/block/noop-iosched.c
@@ -28,13 +28,9 @@ static void elevator_noop_merge_requests(request_queue_t *q, struct request *req
         list_del_init(&next->queuelist);
 }
 
-static void elevator_noop_add_request(request_queue_t *q, struct request *rq,
-                                      int where)
+static void elevator_noop_add_request(request_queue_t *q, struct request *rq)
 {
-        if (where == ELEVATOR_INSERT_FRONT)
-                list_add(&rq->queuelist, &q->queue_head);
-        else
-                list_add_tail(&rq->queuelist, &q->queue_head);
+        elv_dispatch_add_tail(q, rq);
 
         /*
          * new merges must not precede this barrier
@@ -45,19 +41,16 @@ static void elevator_noop_add_request(request_queue_t *q, struct request *rq,
                 q->last_merge = rq;
 }
 
-static struct request *elevator_noop_next_request(request_queue_t *q)
+static int elevator_noop_dispatch(request_queue_t *q, int force)
 {
-        if (!list_empty(&q->queue_head))
-                return list_entry_rq(q->queue_head.next);
-
-        return NULL;
+        return 0;
 }
 
 static struct elevator_type elevator_noop = {
         .ops = {
                 .elevator_merge_fn              = elevator_noop_merge,
                 .elevator_merge_req_fn          = elevator_noop_merge_requests,
-                .elevator_next_req_fn           = elevator_noop_next_request,
+                .elevator_dispatch_fn           = elevator_noop_dispatch,
                 .elevator_add_req_fn            = elevator_noop_add_request,
         },
         .elevator_name = "noop",