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Commit 0b182d61 authored by Jens Axboe's avatar Jens Axboe
Browse files

cfq-iosched: abstract out the 'may this cfqq dispatch' logic 



Makes the whole thing easier to read, cfq_dispatch_requests() was
a bit messy before.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 1b59dd51

block/cfq-iosched.c

+67 −54
Original line number Diff line number Diff line
@@ -1247,67 +1247,21 @@ static int cfq_forced_dispatch(struct cfq_data *cfqd) 
	return dispatched;

}



/*

 * Dispatch a request from cfqq, moving them to the request queue

 * dispatch list.

 */

static void cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)

{

	struct request *rq;



	BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));



	/*

	 * follow expired path, else get first next available

	 */

	rq = cfq_check_fifo(cfqq);

	if (!rq)

		rq = cfqq->next_rq;



	/*

	 * insert request into driver dispatch list

	 */

	cfq_dispatch_insert(cfqd->queue, rq);



	if (!cfqd->active_cic) {

		struct cfq_io_context *cic = RQ_CIC(rq);



		atomic_long_inc(&cic->ioc->refcount);

		cfqd->active_cic = cic;

	}

}



/*

 * Find the cfqq that we need to service and move a request from that to the

 * dispatch list

 */

static int cfq_dispatch_requests(struct request_queue *q, int force)

static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)

{

	struct cfq_data *cfqd = q->elevator->elevator_data;

	struct cfq_queue *cfqq;

	unsigned int max_dispatch;



	if (!cfqd->busy_queues)

		return 0;



	if (unlikely(force))

		return cfq_forced_dispatch(cfqd);



	cfqq = cfq_select_queue(cfqd);

	if (!cfqq)

		return 0;



	/*

	 * Drain async requests before we start sync IO

	 */

	if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])

		return 0;

		return false;



	/*

	 * If this is an async queue and we have sync IO in flight, let it wait

	 */

	if (cfqd->sync_flight && !cfq_cfqq_sync(cfqq))

		return 0;

		return false;



	max_dispatch = cfqd->cfq_quantum;

	if (cfq_class_idle(cfqq))
@@ -1321,13 +1275,13 @@ static int cfq_dispatch_requests(struct request_queue *q, int force) 
		 * idle queue must always only have a single IO in flight

		 */

		if (cfq_class_idle(cfqq))

			return 0;

			return false;



		/*

		 * We have other queues, don't allow more IO from this one

		 */

		if (cfqd->busy_queues > 1)

			return 0;

			return false;



		/*

		 * Sole queue user, allow bigger slice
@@ -1351,13 +1305,72 @@ static int cfq_dispatch_requests(struct request_queue *q, int force) 
			max_dispatch = depth;

	}



	if (cfqq->dispatched >= max_dispatch)

	/*

	 * If we're below the current max, allow a dispatch

	 */

	return cfqq->dispatched < max_dispatch;

}



/*

 * Dispatch a request from cfqq, moving them to the request queue

 * dispatch list.

 */

static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)

{

	struct request *rq;



	BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));



	if (!cfq_may_dispatch(cfqd, cfqq))

		return false;



	/*

	 * follow expired path, else get first next available

	 */

	rq = cfq_check_fifo(cfqq);

	if (!rq)

		rq = cfqq->next_rq;



	/*

	 * insert request into driver dispatch list

	 */

	cfq_dispatch_insert(cfqd->queue, rq);



	if (!cfqd->active_cic) {

		struct cfq_io_context *cic = RQ_CIC(rq);



		atomic_long_inc(&cic->ioc->refcount);

		cfqd->active_cic = cic;

	}



	return true;

}



/*

 * Find the cfqq that we need to service and move a request from that to the

 * dispatch list

 */

static int cfq_dispatch_requests(struct request_queue *q, int force)

{

	struct cfq_data *cfqd = q->elevator->elevator_data;

	struct cfq_queue *cfqq;



	if (!cfqd->busy_queues)

		return 0;



	if (unlikely(force))

		return cfq_forced_dispatch(cfqd);



	cfqq = cfq_select_queue(cfqd);

	if (!cfqq)

		return 0;



	/*

	 * Dispatch a request from this cfqq

	 * Dispatch a request from this cfqq, if it is allowed

	 */

	cfq_dispatch_request(cfqd, cfqq);

	if (!cfq_dispatch_request(cfqd, cfqq))

		return 0;



	cfqq->slice_dispatch++;

	cfq_clear_cfqq_must_dispatch(cfqq);