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Commit 30996f40 authored by Jens Axboe's avatar Jens Axboe
Browse files

cfq-iosched: fix issue with rq-rq merging and fifo list ordering 



cfq uses rq->start_time as the fifo indicator, but that field may
get modified prior to cfq doing it's fifo list adjustment when
a request gets merged with another request. This can cause the
fifo list to become unordered.

Reported-by: default avatarCorrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 374576a8

block/cfq-iosched.c

+7 −8
Original line number Original line Diff line number Diff line
@@ -827,8 +827,10 @@ cfq_merged_requests(struct request_queue *q, struct request *rq, 
	 * reposition in fifo if next is older than rq

	 * reposition in fifo if next is older than rq

	 */

	 */

	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&

	if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&

	    time_before(next->start_time, rq->start_time))

	    time_before(rq_fifo_time(next), rq_fifo_time(rq))) {

		list_move(&rq->queuelist, &next->queuelist);

		list_move(&rq->queuelist, &next->queuelist);

		rq_set_fifo_time(rq, rq_fifo_time(next));

	}





	cfq_remove_request(next);

	cfq_remove_request(next);

}

}
@@ -1129,9 +1131,7 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq) 
 */

 */

static struct request *cfq_check_fifo(struct cfq_queue *cfqq)

static struct request *cfq_check_fifo(struct cfq_queue *cfqq)

{

{

	struct cfq_data *cfqd = cfqq->cfqd;

	struct request *rq = NULL;

	struct request *rq;

	int fifo;





	if (cfq_cfqq_fifo_expire(cfqq))

	if (cfq_cfqq_fifo_expire(cfqq))

		return NULL;

		return NULL;
@@ -1141,13 +1141,11 @@ static struct request *cfq_check_fifo(struct cfq_queue *cfqq) 
	if (list_empty(&cfqq->fifo))

	if (list_empty(&cfqq->fifo))

		return NULL;

		return NULL;





	fifo = cfq_cfqq_sync(cfqq);

	rq = rq_entry_fifo(cfqq->fifo.next);

	rq = rq_entry_fifo(cfqq->fifo.next);



	if (time_before(jiffies, rq_fifo_time(rq)))

	if (time_before(jiffies, rq->start_time + cfqd->cfq_fifo_expire[fifo]))

		rq = NULL;

		rq = NULL;





	cfq_log_cfqq(cfqd, cfqq, "fifo=%p", rq);

	cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);

	return rq;

	return rq;

}

}
@@ -2130,6 +2128,7 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq) 




	cfq_add_rq_rb(rq);

	cfq_add_rq_rb(rq);





	rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);

	list_add_tail(&rq->queuelist, &cfqq->fifo);

	list_add_tail(&rq->queuelist, &cfqq->fifo);





	cfq_rq_enqueued(cfqd, cfqq, rq);

	cfq_rq_enqueued(cfqd, cfqq, rq);