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Commit 9d5a4e94 authored by Mike Snitzer's avatar Mike Snitzer Committed by Jens Axboe
Browse files

block: skip elevator data initialization for flush requests 



Skip elevator initialization for flush requests by passing priv=0 to
blk_alloc_request() in get_request().  As such elv_set_request() is
never called for flush requests.

Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent ae1b1539

block/blk-core.c

+25 −4
Original line number Diff line number Diff line
@@ -737,6 +737,25 @@ static void freed_request(struct request_queue *q, int sync, int priv) 
		__freed_request(q, sync ^ 1);

}



/*

 * Determine if elevator data should be initialized when allocating the

 * request associated with @bio.

 */

static bool blk_rq_should_init_elevator(struct bio *bio)

{

	if (!bio)

		return true;



	/*

	 * Flush requests do not use the elevator so skip initialization.

	 * This allows a request to share the flush and elevator data.

	 */

	if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))

		return false;



	return true;

}



/*

 * Get a free request, queue_lock must be held.

 * Returns NULL on failure, with queue_lock held.
@@ -749,7 +768,7 @@ static struct request *get_request(struct request_queue *q, int rw_flags, 
	struct request_list *rl = &q->rq;

	struct io_context *ioc = NULL;

	const bool is_sync = rw_is_sync(rw_flags) != 0;

	int may_queue, priv;

	int may_queue, priv = 0;



	may_queue = elv_may_queue(q, rw_flags);

	if (may_queue == ELV_MQUEUE_NO)
@@ -793,9 +812,11 @@ static struct request *get_request(struct request_queue *q, int rw_flags, 
	rl->count[is_sync]++;

	rl->starved[is_sync] = 0;



	if (blk_rq_should_init_elevator(bio)) {

		priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);

		if (priv)

			rl->elvpriv++;

	}



	if (blk_queue_io_stat(q))

		rw_flags |= REQ_IO_STAT;