Commit 46eae2e3 authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

block/mq-deadline: Add several comments 



Make the code easier to read by adding more comments.

Reviewed-by: default avatarDamien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: default avatarHimanshu Madhani <himanshu.madhani@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210618004456.7280-6-bvanassche@acm.org


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 556910e3

block/mq-deadline.c

+18 −0
Original line number Diff line number Diff line
@@ -139,6 +139,9 @@ static void dd_request_merged(struct request_queue *q, struct request *req, 
	}

}



/*

 * Callback function that is invoked after @next has been merged into @req.

 */

static void dd_merged_requests(struct request_queue *q, struct request *req,

			       struct request *next)

{
@@ -375,6 +378,8 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd) 
}



/*

 * Called from blk_mq_run_hw_queue() -> __blk_mq_sched_dispatch_requests().

 *

 * One confusing aspect here is that we get called for a specific

 * hardware queue, but we may return a request that is for a

 * different hardware queue. This is because mq-deadline has shared
@@ -438,6 +443,10 @@ static int dd_init_queue(struct request_queue *q, struct elevator_type *e) 
	return 0;

}



/*

 * Try to merge @bio into an existing request. If @bio has been merged into

 * an existing request, store the pointer to that request into *@rq.

 */

static int dd_request_merge(struct request_queue *q, struct request **rq,

			    struct bio *bio)

{
@@ -461,6 +470,10 @@ static int dd_request_merge(struct request_queue *q, struct request **rq, 
	return ELEVATOR_NO_MERGE;

}



/*

 * Attempt to merge a bio into an existing request. This function is called

 * before @bio is associated with a request.

 */

static bool dd_bio_merge(struct request_queue *q, struct bio *bio,

		unsigned int nr_segs)

{
@@ -518,6 +531,9 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, 
	}

}



/*

 * Called from blk_mq_sched_insert_request() or blk_mq_sched_insert_requests().

 */

static void dd_insert_requests(struct blk_mq_hw_ctx *hctx,

			       struct list_head *list, bool at_head)

{
@@ -544,6 +560,8 @@ static void dd_prepare_request(struct request *rq) 
}



/*

 * Callback from inside blk_mq_free_request().

 *

 * For zoned block devices, write unlock the target zone of

 * completed write requests. Do this while holding the zone lock

 * spinlock so that the zone is never unlocked while deadline_fifo_request()