cfq-iosched: Don't set active queue in preempt

Commit "Add unaccounted time to timeslice_used" changed the behavior of
cfq_preempt_queue to set cfqq active. Vivek pointed out that other
preemption rules might get involved, so we shouldn't manually set which
queue is active.

This cleans up the code to just clear the queue stats at preemption
time.

Signed-off-by: Justin TerAvest <teravest@google.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

block/cfq-iosched.c

@@ -1620,27 +1620,33 @@ static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 	cfq_blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg);
 }
 
+static void cfq_clear_queue_stats(struct cfq_data *cfqd,
+				  struct cfq_queue *cfqq)
+{
+	cfq_blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
+	cfqq->slice_start = 0;
+	cfqq->dispatch_start = jiffies;
+	cfqq->allocated_slice = 0;
+	cfqq->slice_end = 0;
+	cfqq->slice_dispatch = 0;
+	cfqq->nr_sectors = 0;
+
+	cfq_clear_cfqq_wait_request(cfqq);
+	cfq_clear_cfqq_must_dispatch(cfqq);
+	cfq_clear_cfqq_must_alloc_slice(cfqq);
+	cfq_clear_cfqq_fifo_expire(cfqq);
+	cfq_mark_cfqq_slice_new(cfqq);
+
+	cfq_del_timer(cfqd, cfqq);
+}
+
 static void __cfq_set_active_queue(struct cfq_data *cfqd,
 				   struct cfq_queue *cfqq)
 {
 	if (cfqq) {
 		cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
 				cfqd->serving_prio, cfqd->serving_type);
-		cfq_blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
-		cfqq->slice_start = 0;
-		cfqq->dispatch_start = jiffies;
-		cfqq->allocated_slice = 0;
-		cfqq->slice_end = 0;
-		cfqq->slice_dispatch = 0;
-		cfqq->nr_sectors = 0;
-
-		cfq_clear_cfqq_wait_request(cfqq);
-		cfq_clear_cfqq_must_dispatch(cfqq);
-		cfq_clear_cfqq_must_alloc_slice(cfqq);
-		cfq_clear_cfqq_fifo_expire(cfqq);
-		cfq_mark_cfqq_slice_new(cfqq);
-
-		cfq_del_timer(cfqd, cfqq);
+		cfq_clear_queue_stats(cfqd, cfqq);
 	}
 
 	cfqd->active_queue = cfqq;
@@ -3332,7 +3338,8 @@ static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 	BUG_ON(!cfq_cfqq_on_rr(cfqq));
 
 	cfq_service_tree_add(cfqd, cfqq, 1);
-	__cfq_set_active_queue(cfqd, cfqq);
+
+	cfq_clear_queue_stats(cfqd, cfqq);
 }
 
 /*