cfq-iosched: fix think time allowed for seekers

CFQ enables idle only for processes that think less than the allowed
idle time. Since idle time is lower for seeky queues, we should use the
correct value in the comparison.
Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/cfq-iosched.c

@@ -1995,7 +1995,10 @@ cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 	    (!cfqd->cfq_latency && cfqd->hw_tag && CIC_SEEKY(cic)))
 		enable_idle = 0;
 	else if (sample_valid(cic->ttime_samples)) {
-		if (cic->ttime_mean > cfqd->cfq_slice_idle)
+		unsigned int slice_idle = cfqd->cfq_slice_idle;
+		if (sample_valid(cic->seek_samples) && CIC_SEEKY(cic))
+			slice_idle = msecs_to_jiffies(CFQ_MIN_TT);
+		if (cic->ttime_mean > slice_idle)
 			enable_idle = 0;
 		else
 			enable_idle = 1;