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blk-mq: Simplify request completion state

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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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Keith Busch 2018-11-26 09:54:30 -07:00 committed by Jens Axboe
parent f1342709d1
commit af78ff7c6e
2 changed files with 1 additions and 17 deletions
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4
block/blk-mq.c
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@ -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

14
include/linux/blk-mq.h
View File

@ -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.