Commit 3d106fba authored Nov 06, 2012 by Shaohua Li Committed by Jens Axboe Nov 06, 2012

block CFQ: avoid moving request to different queue



request is queued in cfqq->fifo list. Looks it's possible we are moving a
request from one cfqq to another in request merge case. In such case, adjusting
the fifo list order doesn't make sense and is impossible if we don't iterate
the whole fifo list.

My test does hit one case the two cfqq are different, but didn't cause kernel
crash, maybe it's because fifo list isn't used frequently. Anyway, from the
code logic, this is buggy.

I thought we can re-enable the recusive merge logic after this is fixed.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 3d70f8c6

block/cfq-iosched.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -1973,7 +1973,8 @@ cfq_merged_requests(struct request_queue q, struct request rq,
		* reposition in fifo if next is older than rq
		*/
		if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
		time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
		time_before(rq_fifo_time(next), rq_fifo_time(rq)) &&
		cfqq == RQ_CFQQ(next)) {
		list_move(&rq->queuelist, &next->queuelist);
		rq_set_fifo_time(rq, rq_fifo_time(next));
		}

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