Commit d92ca9d8 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

blk-mq: don't handle non-flush requests in blk_insert_flush 



Return to the normal blk_mq_submit_bio flow if the bio did not end up
actually being a flush because the device didn't support it.  Note that
this is basically impossible to hit without special instrumentation given
that submit_bio_checks already clears these flags usually, so we'd need a
tight race to actually hit this code path.

With this the call to blk_mq_run_hw_queue for the flush requests can be
removed given that the actual flush requests are always issued via the
requeue workqueue which runs the queue unconditionally.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211019122553.2467817-1-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent dc5fc361

block/blk-flush.c

+6 −6
Original line number Diff line number Diff line
@@ -379,7 +379,7 @@ static void mq_flush_data_end_io(struct request *rq, blk_status_t error) 
 * @rq is being submitted.  Analyze what needs to be done and put it on the

 * right queue.

 */

void blk_insert_flush(struct request *rq)

bool blk_insert_flush(struct request *rq)

{

	struct request_queue *q = rq->q;

	unsigned long fflags = q->queue_flags;	/* may change, cache */
@@ -409,7 +409,7 @@ void blk_insert_flush(struct request *rq) 
	 */

	if (!policy) {

		blk_mq_end_request(rq, 0);

		return;

		return true;

	}



	BUG_ON(rq->bio != rq->biotail); /*assumes zero or single bio rq */
@@ -420,10 +420,8 @@ void blk_insert_flush(struct request *rq) 
	 * for normal execution.

	 */

	if ((policy & REQ_FSEQ_DATA) &&

	    !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {

		blk_mq_request_bypass_insert(rq, false, false);

		return;

	}

	    !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH)))

		return false;



	/*

	 * @rq should go through flush machinery.  Mark it part of flush
@@ -439,6 +437,8 @@ void blk_insert_flush(struct request *rq) 
	spin_lock_irq(&fq->mq_flush_lock);

	blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0);

	spin_unlock_irq(&fq->mq_flush_lock);



	return true;

}



/**

block/blk-mq.c

+6 −8
Original line number Diff line number Diff line
@@ -2532,12 +2532,10 @@ void blk_mq_submit_bio(struct bio *bio) 
		return;

	}



	if (unlikely(is_flush_fua)) {

		struct blk_mq_hw_ctx *hctx = rq->mq_hctx;

		/* Bypass scheduler for flush requests */

		blk_insert_flush(rq);

		blk_mq_run_hw_queue(hctx, true);

	} else if (plug && (q->nr_hw_queues == 1 ||

	if (is_flush_fua && blk_insert_flush(rq))

		return;



	if (plug && (q->nr_hw_queues == 1 ||

	    blk_mq_is_shared_tags(rq->mq_hctx->flags) ||

	    q->mq_ops->commit_rqs || !blk_queue_nonrot(q))) {

		/*

block/blk.h

+1 −1
Original line number Diff line number Diff line
@@ -236,7 +236,7 @@ void __blk_account_io_done(struct request *req, u64 now); 
 */

#define ELV_ON_HASH(rq) ((rq)->rq_flags & RQF_HASHED)



void blk_insert_flush(struct request *rq);

bool blk_insert_flush(struct request *rq);



int elevator_switch_mq(struct request_queue *q,

			      struct elevator_type *new_e);