From e00c54c36ac2024c3a8a37432e2e2698ff849594 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Sun, 4 Oct 2009 20:36:19 +0200 Subject: [PATCH] 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: Jens Axboe --- block/cfq-iosched.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index ebab60c6be9d..9c4b679908f4 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -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; }