Commit 80a4b58e authored by Jens Axboe's avatar Jens Axboe
Browse files

block: only call ->request_fn when the queue is not stopped 



Callers should use either blk_run_queue/__blk_run_queue, or
blk_start_queueing() to invoke request handling instead of calling
->request_fn() directly as that does not take the queue stopped
flag into account.

Also add appropriate comments on the above functions to detail
their usage.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent ee2e992c

block/blk-core.c

+17 −2
Original line number Diff line number Diff line
@@ -325,6 +325,9 @@ EXPORT_SYMBOL(blk_unplug); 


static void blk_invoke_request_fn(struct request_queue *q)

{

	if (unlikely(blk_queue_stopped(q)))

		return;



	/*

	 * one level of recursion is ok and is much faster than kicking

	 * the unplug handling
@@ -399,8 +402,13 @@ void blk_sync_queue(struct request_queue *q) 
EXPORT_SYMBOL(blk_sync_queue);



/**

 * blk_run_queue - run a single device queue

 * __blk_run_queue - run a single device queue

 * @q:	The queue to run

 *

 * Description:

 *    See @blk_run_queue. This variant must be called with the queue lock

 *    held and interrupts disabled.

 *

 */

void __blk_run_queue(struct request_queue *q)

{
@@ -418,6 +426,12 @@ EXPORT_SYMBOL(__blk_run_queue); 
/**

 * blk_run_queue - run a single device queue

 * @q: The queue to run

 *

 * Description:

 *    Invoke request handling on this queue, if it has pending work to do.

 *    May be used to restart queueing when a request has completed. Also

 *    See @blk_start_queueing.

 *

 */

void blk_run_queue(struct request_queue *q)

{
@@ -884,7 +898,8 @@ EXPORT_SYMBOL(blk_get_request); 
 *

 * This is basically a helper to remove the need to know whether a queue

 * is plugged or not if someone just wants to initiate dispatch of requests

 * for this queue.

 * for this queue. Should be used to start queueing on a device outside

 * of ->request_fn() context. Also see @blk_run_queue.

 *

 * The queue lock must be held with interrupts disabled.

 */

block/elevator.c

+3 −4
Original line number Diff line number Diff line
@@ -612,7 +612,7 @@ void elv_insert(struct request_queue *q, struct request *rq, int where) 
		 *   processing.

		 */

		blk_remove_plug(q);

		q->request_fn(q);

		blk_start_queueing(q);

		break;



	case ELEVATOR_INSERT_SORT:
@@ -950,7 +950,7 @@ void elv_completed_request(struct request_queue *q, struct request *rq) 
		    blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&

		    blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {

			blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);

			q->request_fn(q);

			blk_start_queueing(q);

		}

	}

}
@@ -1109,8 +1109,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) 
	elv_drain_elevator(q);



	while (q->rq.elvpriv) {

		blk_remove_plug(q);

		q->request_fn(q);

		blk_start_queueing(q);

		spin_unlock_irq(q->queue_lock);

		msleep(10);

		spin_lock_irq(q->queue_lock);

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