cfq-iosched: removing unnecessary think time checking

Removing think time checking. A high thinktime queue might means the queue
dispatches several requests and then do away. Limitting such queue seems
meaningless. And also this can simplify code. This is suggested by Vivek.
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

block/cfq-iosched.c

@@ -2417,19 +2417,14 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 			return false;
 
 		/*
-		 * If there is only one sync queue, and its think time is
-		 * small, we can ignore async queue here and give the sync
+		 * If there is only one sync queue
+		 * we can ignore async queue here and give the sync
 		 * queue no dispatch limit. The reason is a sync queue can
 		 * preempt async queue, limiting the sync queue doesn't make
 		 * sense. This is useful for aiostress test.
 		 */
-		if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1) {
-			struct cfq_io_context *cic = RQ_CIC(cfqq->next_rq);
-
-			if (sample_valid(cic->ttime_samples) &&
-				cic->ttime_mean < cfqd->cfq_slice_idle)
-				promote_sync = true;
-		}
+		if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1)
+			promote_sync = true;
 
 		/*
 		 * We have other queues, don't allow more IO from this one