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Commit ca11f209 authored by Jens Axboe's avatar Jens Axboe
Browse files

mq-deadline: make it clear that __dd_dispatch_request() works on all hw queues 



Don't pass in the hardware queue to __dd_dispatch_request(), since it
leads the reader to believe that we are returning a request for that
specific hardware queue. That's not how mq-deadline works, the state
for determining which request to serve next is shared across all
hardware queues for a device.

Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 14db4917

block/mq-deadline.c

+8 −3
Original line number Diff line number Diff line
@@ -267,9 +267,8 @@ deadline_next_request(struct deadline_data *dd, int data_dir) 
 * deadline_dispatch_requests selects the best request according to

 * read/write expire, fifo_batch, etc

 */

static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx)

static struct request *__dd_dispatch_request(struct deadline_data *dd)

{

	struct deadline_data *dd = hctx->queue->elevator->elevator_data;

	struct request *rq, *next_rq;

	bool reads, writes;

	int data_dir;
@@ -372,13 +371,19 @@ static struct request *__dd_dispatch_request(struct blk_mq_hw_ctx *hctx) 
	return rq;

}



/*

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

 * hardware queue, but we return a request that may not be for a

 * different hardware queue. This is because mq-deadline has shared

 * state for all hardware queues, in terms of sorting, FIFOs, etc.

 */

static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx)

{

	struct deadline_data *dd = hctx->queue->elevator->elevator_data;

	struct request *rq;



	spin_lock(&dd->lock);

	rq = __dd_dispatch_request(hctx);

	rq = __dd_dispatch_request(dd);

	spin_unlock(&dd->lock);



	return rq;