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Commit e00c54c3 authored by Jens Axboe's avatar Jens Axboe
Browse files

cfq-iosched: don't delay async queue if it hasn't dispatched at all 



We cannot delay for the first dispatch of the async queue if it
hasn't dispatched at all, since that could present a local user
DoS attack vector using an app that just did slow timed sync reads
while filling memory.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent ac481c20

block/cfq-iosched.c

+2 −9
Original line number Diff line number Diff line
@@ -1345,16 +1345,9 @@ static int cfq_dispatch_requests(struct request_queue *q, int force) 
		unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;

		unsigned int depth;



		/*

		 * must wait a bit longer

		 */

		if (last_sync < cfqd->cfq_slice[1]) {

			cfq_schedule_dispatch(cfqd,

						cfqd->cfq_slice[1] - last_sync);

			return 0;

		}



		depth = last_sync / cfqd->cfq_slice[1];

		if (!depth && !cfqq->dispatched)

			depth = 1;

		if (depth < max_dispatch)

			max_dispatch = depth;

	}