--- a/block/cfq-iosched.c	2009-11-17 15:47:50.000000000 -0500
+++ b/block/cfq-iosched.c	2009-11-17 15:50:38.000000000 -0500
@@ -234,8 +234,17 @@ struct cfq_data {
 	 */
 	int rq_queued;
 	int hw_tag;
-	int hw_tag_samples;
-	int rq_in_driver_peak;
+
+	/*
+	 * hw_tag can be
+	 * -1 => indeterminate, (cfq will behave as if NCQ is present,
+	 *			 to allow better detection)
+	 *  1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
+	 *  0 => no NCQ
+	 */
+	int hw_tag_est_depth;
+	unsigned int hw_tag_samples;
+
 
 	/*
 	 * idle window management
@@ -3199,8 +3208,11 @@ static void cfq_update_hw_tag(struct cfq
 {
 	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);
+	if (rq_in_driver(cfqd) > cfqd->hw_tag_est_depth)
+		cfqd->hw_tag_est_depth = rq_in_driver(cfqd);
+
+	if (cfqd->hw_tag == 1)
+		return;
 
 	if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
 	    rq_in_driver(cfqd) <= CFQ_HW_QUEUE_MIN)
@@ -3219,13 +3231,10 @@ static void cfq_update_hw_tag(struct cfq
 	if (cfqd->hw_tag_samples++ < 50)
 		return;
 
-	if (cfqd->rq_in_driver_peak >= CFQ_HW_QUEUE_MIN)
+	if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
 		cfqd->hw_tag = 1;
 	else
 		cfqd->hw_tag = 0;
-
-	cfqd->hw_tag_samples = 0;
-	cfqd->rq_in_driver_peak = 0;
 }
 
 static void cfq_completed_request(struct request_queue *q, struct request *rq)
@@ -3661,7 +3670,7 @@ static void *cfq_init_queue(struct reque
 	cfqd->cfq_slice_idle = cfq_slice_idle;
 	cfqd->cfq_latency = 1;
 	cfqd->cfq_group_idle = 1;
-	cfqd->hw_tag = 1;
+	cfqd->hw_tag = -1;
 	cfqd->last_end_sync_rq = jiffies;
 	return cfqd;
 }