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 @@
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;
}