[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>

1 files changed, 85 insertions, 205 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,