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Commit 21c6e939 authored by Jens Axboe's avatar Jens Axboe
Browse files

blk-mq: unify hctx delay_work and run_work 



The only difference between ->run_work and ->delay_work, is that
the latter is used to defer running a queue. This is done by
marking the queue stopped, and scheduling ->delay_work to run
sometime in the future. While the queue is stopped, direct runs
or runs through ->run_work will not run the queue.

If we combine the handlers, then we need to handle two things:

1) If a delayed/stopped run is scheduled, then we should not run
   the queue before that has been completed.
2) If a queue is delayed/stopped, the handler needs to restart
   the queue. Normally a run of a queue with the stopped bit set
   would be a no-op.

Case 1 is handled by modifying a currently pending queue run
to the deadline set by the caller of blk_mq_delay_queue().
Subsequent attempts to queue a queue run will find the work
item already pending, and direct runs will see a stopped queue
as before.

Case 2 is handled by adding a new bit, BLK_MQ_S_START_ON_RUN,
that tells the work handler that it should clear a stopped
queue and run the handler.

Reviewed-by: default avatarBart Van Assche <Bart.VanAssche@sandisk.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 818cd1cb

block/blk-core.c

+1 −3
Original line number Diff line number Diff line
@@ -268,10 +268,8 @@ void blk_sync_queue(struct request_queue *q) 
		struct blk_mq_hw_ctx *hctx;

		int i;



		queue_for_each_hw_ctx(q, hctx, i) {

		queue_for_each_hw_ctx(q, hctx, i)

			cancel_delayed_work_sync(&hctx->run_work);

			cancel_delayed_work_sync(&hctx->delay_work);

		}

	} else {

		cancel_delayed_work_sync(&q->delay_work);

	}

block/blk-mq.c

+22 −12
Original line number Diff line number Diff line
@@ -1221,7 +1221,6 @@ EXPORT_SYMBOL(blk_mq_queue_stopped); 
void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)

{

	cancel_delayed_work_sync(&hctx->run_work);

	cancel_delayed_work(&hctx->delay_work);

	set_bit(BLK_MQ_S_STOPPED, &hctx->state);

}

EXPORT_SYMBOL(blk_mq_stop_hw_queue);
@@ -1279,27 +1278,39 @@ static void blk_mq_run_work_fn(struct work_struct *work) 
	struct blk_mq_hw_ctx *hctx;



	hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);

	__blk_mq_run_hw_queue(hctx);

}



static void blk_mq_delay_work_fn(struct work_struct *work)

{

	struct blk_mq_hw_ctx *hctx;

	/*

	 * If we are stopped, don't run the queue. The exception is if

	 * BLK_MQ_S_START_ON_RUN is set. For that case, we auto-clear

	 * the STOPPED bit and run it.

	 */

	if (test_bit(BLK_MQ_S_STOPPED, &hctx->state)) {

		if (!test_bit(BLK_MQ_S_START_ON_RUN, &hctx->state))

			return;



	hctx = container_of(work, struct blk_mq_hw_ctx, delay_work.work);

		clear_bit(BLK_MQ_S_START_ON_RUN, &hctx->state);

		clear_bit(BLK_MQ_S_STOPPED, &hctx->state);

	}



	if (test_and_clear_bit(BLK_MQ_S_STOPPED, &hctx->state))

	__blk_mq_run_hw_queue(hctx);

}





void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)

{

	if (unlikely(!blk_mq_hw_queue_mapped(hctx)))

		return;



	/*

	 * Stop the hw queue, then modify currently delayed work.

	 * This should prevent us from running the queue prematurely.

	 * Mark the queue as auto-clearing STOPPED when it runs.

	 */

	blk_mq_stop_hw_queue(hctx);

	kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),

			&hctx->delay_work, msecs_to_jiffies(msecs));

	set_bit(BLK_MQ_S_START_ON_RUN, &hctx->state);

	kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx),

					&hctx->run_work,

					msecs_to_jiffies(msecs));

}

EXPORT_SYMBOL(blk_mq_delay_queue);
@@ -1885,7 +1896,6 @@ static int blk_mq_init_hctx(struct request_queue *q, 
		node = hctx->numa_node = set->numa_node;



	INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);

	INIT_DELAYED_WORK(&hctx->delay_work, blk_mq_delay_work_fn);

	spin_lock_init(&hctx->lock);

	INIT_LIST_HEAD(&hctx->dispatch);

	hctx->queue = q;

include/linux/blk-mq.h

+1 −2
Original line number Diff line number Diff line
@@ -51,8 +51,6 @@ struct blk_mq_hw_ctx { 


	atomic_t		nr_active;



	struct delayed_work	delay_work;



	struct hlist_node	cpuhp_dead;

	struct kobject		kobj;
@@ -168,6 +166,7 @@ enum { 
	BLK_MQ_S_TAG_ACTIVE	= 1,

	BLK_MQ_S_SCHED_RESTART	= 2,

	BLK_MQ_S_TAG_WAITING	= 3,

	BLK_MQ_S_START_ON_RUN	= 4,



	BLK_MQ_MAX_DEPTH	= 10240,