1 files changed, 31 insertions, 3 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 6e5c3d715ebe..76afa3696894 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1160,6 +1160,34 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
         return cfqq;
 }
 
+/*
+ * Determine whether we should enforce idle window for this queue.
+ */
+
+static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
+{
+        enum wl_prio_t prio = cfqq_prio(cfqq);
+        struct cfq_rb_root *service_tree;
+
+        /* We never do for idle class queues. */
+        if (prio == IDLE_WORKLOAD)
+                return false;
+
+        /* We do for queues that were marked with idle window flag. */
+        if (cfq_cfqq_idle_window(cfqq))
+                return true;
+
+        /*
+         * Otherwise, we do only if they are the last ones
+         * in their service tree.
+         */
+        service_tree = service_tree_for(prio, cfqd);
+        if (service_tree->count == 0)
+                return true;
+
+        return (service_tree->count == 1 && cfq_rb_first(service_tree) == cfqq);
+}
+
 static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 {
         struct cfq_queue *cfqq = cfqd->active_queue;
@@ -1180,7 +1208,7 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
         /*
          * idle is disabled, either manually or by past process history
          */
-        if (!cfqd->cfq_slice_idle || !cfq_cfqq_idle_window(cfqq))
+        if (!cfqd->cfq_slice_idle || !cfq_should_idle(cfqd, cfqq))
                 return;
 
         /*
@@ -1362,7 +1390,7 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
          * conditions to happen (or time out) before selecting a new queue.
          */
         if (timer_pending(&cfqd->idle_slice_timer) ||
-            (cfqq->dispatched && cfq_cfqq_idle_window(cfqq))) {
+            (cfqq->dispatched && cfq_should_idle(cfqd, cfqq))) {
                 cfqq = NULL;
                 goto keep_queue;
         }
@@ -1427,7 +1455,7 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
         /*
          * Drain async requests before we start sync IO
          */
-        if (cfq_cfqq_idle_window(cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
+        if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_driver[BLK_RW_ASYNC])
                 return false;
 
         /*