Commit af78ff7c authored by Keith Busch's avatar Keith Busch Committed by Jens Axboe
Browse files

blk-mq: Simplify request completion state 



There are no more users relying on blk-mq request states to prevent
double completions, so replace the relatively expensive cmpxchg operation
with WRITE_ONCE.

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f1342709

block/blk-mq.c

+1 −3
Original line number Diff line number Diff line
@@ -568,9 +568,7 @@ static void __blk_mq_complete_request(struct request *rq) 
	bool shared = false;

	int cpu;



	if (!blk_mq_mark_complete(rq))

		return;



	WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);

	/*

	 * Most of single queue controllers, there is only one irq vector

	 * for handling IO completion, and the only irq's affinity is set

include/linux/blk-mq.h

+0 −14
Original line number Diff line number Diff line
@@ -329,20 +329,6 @@ void blk_mq_quiesce_queue_nowait(struct request_queue *q); 


unsigned int blk_mq_rq_cpu(struct request *rq);



/**

 * blk_mq_mark_complete() - Set request state to complete

 * @rq: request to set to complete state

 *

 * Returns true if request state was successfully set to complete. If

 * successful, the caller is responsibile for seeing this request is ended, as

 * blk_mq_complete_request will not work again.

 */

static inline bool blk_mq_mark_complete(struct request *rq)

{

	return cmpxchg(&rq->state, MQ_RQ_IN_FLIGHT, MQ_RQ_COMPLETE) ==

			MQ_RQ_IN_FLIGHT;

}



/*

 * Driver command data is immediately after the request. So subtract request

 * size to get back to the original request, add request size to get the PDU.