Commit 360f2648 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

blk-mq: defer to the normal submission path for non-flush flush commands 



If blk_insert_flush decides that a command does not need to use the
flush state machine, return false and let blk_mq_submit_bio handle
it the normal way (including using an I/O scheduler) instead of doing
a bypass insert.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarDamien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230519044050.107790-4-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent c1075e54

block/blk-flush.c

+8 −14
Original line number Diff line number Diff line
@@ -385,22 +385,17 @@ static void blk_rq_init_flush(struct request *rq) 
	rq->end_io = mq_flush_data_end_io;

}



/**

 * blk_insert_flush - insert a new PREFLUSH/FUA request

 * @rq: request to insert

 *

 * To be called from __elv_add_request() for %ELEVATOR_INSERT_FLUSH insertions.

 * or __blk_mq_run_hw_queue() to dispatch request.

 * @rq is being submitted.  Analyze what needs to be done and put it on the

 * right queue.

/*

 * Insert a PREFLUSH/FUA request into the flush state machine.

 * Returns true if the request has been consumed by the flush state machine,

 * or false if the caller should continue to process it.

 */

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 */

	unsigned int policy = blk_flush_policy(fflags, rq);

	struct blk_flush_queue *fq = blk_get_flush_queue(q, rq->mq_ctx);

	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;



	/* FLUSH/FUA request must never be merged */

	WARN_ON_ONCE(rq->bio != rq->biotail);
@@ -429,16 +424,14 @@ void blk_insert_flush(struct request *rq) 
		 * complete the request.

		 */

		blk_mq_end_request(rq, 0);

		return;

		return true;

	case REQ_FSEQ_DATA:

		/*

		 * If there's data, but no flush is necessary, the request can

		 * be processed directly without going through flush machinery.

		 * Queue for normal execution.

		 */

		blk_mq_request_bypass_insert(rq, 0);

		blk_mq_run_hw_queue(hctx, false);

		return;

		return false;

	default:

		/*

		 * Mark the request as part of a flush sequence and submit it
@@ -448,6 +441,7 @@ 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

+4 −4
Original line number Diff line number Diff line
@@ -45,6 +45,8 @@ 
static DEFINE_PER_CPU(struct llist_head, blk_cpu_done);



static void blk_mq_insert_request(struct request *rq, blk_insert_t flags);

static void blk_mq_request_bypass_insert(struct request *rq,

		blk_insert_t flags);

static void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,

		struct list_head *list);
@@ -2430,7 +2432,7 @@ static void blk_mq_run_work_fn(struct work_struct *work) 
 * Should only be used carefully, when the caller knows we want to

 * bypass a potential IO scheduler on the target device.

 */

void blk_mq_request_bypass_insert(struct request *rq, blk_insert_t flags)

static void blk_mq_request_bypass_insert(struct request *rq, blk_insert_t flags)

{

	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
@@ -2977,10 +2979,8 @@ void blk_mq_submit_bio(struct bio *bio) 
		return;

	}



	if (op_is_flush(bio->bi_opf)) {

		blk_insert_flush(rq);

	if (op_is_flush(bio->bi_opf) && blk_insert_flush(rq))

		return;

	}



	if (plug) {

		blk_add_rq_to_plug(plug, rq);

block/blk-mq.h

+0 −4
Original line number Diff line number Diff line
@@ -64,10 +64,6 @@ struct blk_mq_tags *blk_mq_alloc_map_and_rqs(struct blk_mq_tag_set *set, 
void blk_mq_free_map_and_rqs(struct blk_mq_tag_set *set,

			     struct blk_mq_tags *tags,

			     unsigned int hctx_idx);

/*

 * Internal helpers for request insertion into sw queues

 */

void blk_mq_request_bypass_insert(struct request *rq, blk_insert_t flags);



/*

 * CPU -> queue mappings

block/blk.h

+1 −1
Original line number Diff line number Diff line
@@ -269,7 +269,7 @@ bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, 
 */

#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(struct request_queue *q, struct elevator_type *new_e);

void elevator_disable(struct request_queue *q);