Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 1f460b63 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

blk-mq: don't restart queue when .get_budget returns BLK_STS_RESOURCE 



SCSI restarts its queue in scsi_end_request() automatically, so we don't
need to handle this case in blk-mq.

Especailly any request won't be dequeued in this case, we needn't to
worry about IO hang caused by restart vs. dispatch.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 358a3a6b

block/blk-mq-sched.c

+20 −25
Original line number Diff line number Diff line
@@ -81,8 +81,12 @@ void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx) 
	}

}



/* return true if hctx need to run again */

static bool blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)

/*

 * Only SCSI implements .get_budget and .put_budget, and SCSI restarts

 * its queue by itself in its completion handler, so we don't need to

 * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE.

 */

static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)

{

	struct request_queue *q = hctx->queue;

	struct elevator_queue *e = q->elevator;
@@ -98,7 +102,7 @@ static bool blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) 


		ret = blk_mq_get_dispatch_budget(hctx);

		if (ret == BLK_STS_RESOURCE)

			return true;

			break;



		rq = e->type->ops.mq.dispatch_request(hctx);

		if (!rq) {
@@ -116,8 +120,6 @@ static bool blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) 
		 */

		list_add(&rq->queuelist, &rq_list);

	} while (blk_mq_dispatch_rq_list(q, &rq_list, true));



	return false;

}



static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx,
@@ -131,8 +133,12 @@ static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx, 
	return hctx->ctxs[idx];

}



/* return true if hctx need to run again */

static bool blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)

/*

 * Only SCSI implements .get_budget and .put_budget, and SCSI restarts

 * its queue by itself in its completion handler, so we don't need to

 * restart queue if .get_budget() returns BLK_STS_NO_RESOURCE.

 */

static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)

{

	struct request_queue *q = hctx->queue;

	LIST_HEAD(rq_list);
@@ -147,7 +153,7 @@ static bool blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) 


		ret = blk_mq_get_dispatch_budget(hctx);

		if (ret == BLK_STS_RESOURCE)

			return true;

			break;



		rq = blk_mq_dequeue_from_ctx(hctx, ctx);

		if (!rq) {
@@ -171,22 +177,19 @@ static bool blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx) 
	} while (blk_mq_dispatch_rq_list(q, &rq_list, true));



	WRITE_ONCE(hctx->dispatch_from, ctx);



	return false;

}



/* return true if hw queue need to be run again */

bool blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)

void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)

{

	struct request_queue *q = hctx->queue;

	struct elevator_queue *e = q->elevator;

	const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request;

	LIST_HEAD(rq_list);

	bool run_queue = false;



	/* RCU or SRCU read lock is needed before checking quiesced flag */

	if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)))

		return false;

		return;



	hctx->run++;
@@ -218,12 +221,12 @@ bool blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) 
		blk_mq_sched_mark_restart_hctx(hctx);

		if (blk_mq_dispatch_rq_list(q, &rq_list, false)) {

			if (has_sched_dispatch)

				run_queue = blk_mq_do_dispatch_sched(hctx);

				blk_mq_do_dispatch_sched(hctx);

			else

				run_queue = blk_mq_do_dispatch_ctx(hctx);

				blk_mq_do_dispatch_ctx(hctx);

		}

	} else if (has_sched_dispatch) {

		run_queue = blk_mq_do_dispatch_sched(hctx);

		blk_mq_do_dispatch_sched(hctx);

	} else if (q->mq_ops->get_budget) {

		/*

		 * If we need to get budget before queuing request, we
@@ -233,19 +236,11 @@ bool blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) 
		 * TODO: get more budgets, and dequeue more requests in

		 * one time.

		 */

		run_queue = blk_mq_do_dispatch_ctx(hctx);

		blk_mq_do_dispatch_ctx(hctx);

	} else {

		blk_mq_flush_busy_ctxs(hctx, &rq_list);

		blk_mq_dispatch_rq_list(q, &rq_list, false);

	}



	if (run_queue && !blk_mq_sched_needs_restart(hctx) &&

			!test_bit(BLK_MQ_S_TAG_WAITING, &hctx->state)) {

		blk_mq_sched_mark_restart_hctx(hctx);

		return true;

	}



	return false;

}



bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,

block/blk-mq-sched.h

+1 −1
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ void blk_mq_sched_insert_requests(struct request_queue *q, 
				  struct blk_mq_ctx *ctx,

				  struct list_head *list, bool run_queue_async);



bool blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx);

void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx);



int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e);

void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e);

block/blk-mq.c

+2 −6
Original line number Diff line number Diff line
@@ -1226,7 +1226,6 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list, 
static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)

{

	int srcu_idx;

	bool run_queue;



	/*

	 * We should be running this queue from one of the CPUs that
@@ -1243,18 +1242,15 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) 


	if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {

		rcu_read_lock();

		run_queue = blk_mq_sched_dispatch_requests(hctx);

		blk_mq_sched_dispatch_requests(hctx);

		rcu_read_unlock();

	} else {

		might_sleep();



		srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);

		run_queue = blk_mq_sched_dispatch_requests(hctx);

		blk_mq_sched_dispatch_requests(hctx);

		srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);

	}



	if (run_queue)

		blk_mq_run_hw_queue(hctx, true);

}



/*