From 7c153bfa40948a12735239c67490d43db9fc1577 Mon Sep 17 00:00:00 2001
From: Shaohua Li <shaohua.li@intel.com>
Date: Tue, 27 Oct 2009 08:46:23 +0100
Subject: [PATCH] --- yaml --- r: 172915 b: refs/heads/master c:
 1a1238a7dd48e48b3bba8f426a1d61c22c80d6d1 h: refs/heads/master i:   172913:
 858a68ffe53528bdd632db870371a1675419fc30   172911:
 e07f0fdc83097dbb510a80877afe8940f59e794f v: v3

---
 [refs]                    |  2 +-
 trunk/block/cfq-iosched.c | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index d9ef24940128..528babaeb48c 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: e6c5bc737ab71e4af6025ef7d150f5a26ae5f146
+refs/heads/master: 1a1238a7dd48e48b3bba8f426a1d61c22c80d6d1
diff --git a/trunk/block/cfq-iosched.c b/trunk/block/cfq-iosched.c
index 47d6aaca0c51..418da9a49bb0 100644
--- a/trunk/block/cfq-iosched.c
+++ b/trunk/block/cfq-iosched.c
@@ -2257,6 +2257,8 @@ static void cfq_insert_request(struct request_queue *q, struct request *rq)
  */
 static void cfq_update_hw_tag(struct cfq_data *cfqd)
 {
+	struct cfq_queue *cfqq = cfqd->active_queue;
+
 	if (rq_in_driver(cfqd) > cfqd->rq_in_driver_peak)
 		cfqd->rq_in_driver_peak = rq_in_driver(cfqd);
 
@@ -2264,6 +2266,16 @@ static void cfq_update_hw_tag(struct cfq_data *cfqd)
 	    rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
 		return;
 
+	/*
+	 * If active queue hasn't enough requests and can idle, cfq might not
+	 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
+	 * case
+	 */
+	if (cfqq && cfq_cfqq_idle_window(cfqq) &&
+	    cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
+	    CFQ_HW_QUEUE_MIN && rq_in_driver(cfqd) < CFQ_HW_QUEUE_MIN)
+		return;
+
 	if (cfqd->hw_tag_samples++ < 50)
 		return;