From: Jens Axboe <jens.axboe@oracle.com>
Date: Sun, 4 Oct 2009 18:36:19 +0000 (+0200)
Subject: cfq-iosched: don't delay async queue if it hasn't dispatched at all
X-Git-Tag: 2.1b_release~10711^2~1
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=e00c54c36ac2024c3a8a37432e2e2698ff849594;p=platform%2Fkernel%2Fkernel-mfld-blackbay.git

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 <jens.axboe@oracle.com>
---

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ebab60c..9c4b679 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;
 	}