2 files changed, 11 insertions, 2 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 52559715cb90..93051d151635 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1146,7 +1146,7 @@ void init_request_from_bio(struct request *req, struct bio *bio)
  */
 static inline bool queue_should_plug(struct request_queue *q)
 {
-        return !(blk_queue_nonrot(q) && blk_queue_tagged(q));
+        return !(blk_queue_nonrot(q) && blk_queue_queuing(q));
 }
 
 static int __make_request(struct request_queue *q, struct bio *bio)
@@ -1857,8 +1857,15 @@ void blk_dequeue_request(struct request *rq)
          * and to it is freed is accounted as io that is in progress at
          * the driver side.
          */
-        if (blk_account_rq(rq))
+        if (blk_account_rq(rq)) {
                 q->in_flight[rq_is_sync(rq)]++;
+                /*
+                 * Mark this device as supporting hardware queuing, if
+                 * we have more IOs in flight than 4.
+                 */
+                if (!blk_queue_queuing(q) && queue_in_flight(q) > 4)
+                        set_bit(QUEUE_FLAG_CQ, &q->queue_flags);
+        }
 }
 
 /**
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 88edb62def82..98b45633a27e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -459,6 +459,7 @@ struct request_queue
 #define QUEUE_FLAG_NONROT      14       /* non-rotational device (SSD) */
 #define QUEUE_FLAG_VIRT        QUEUE_FLAG_NONROT /* paravirt device */
 #define QUEUE_FLAG_IO_STAT     15       /* do IO stats */
+#define QUEUE_FLAG_CQ          16       /* hardware does queuing */
 
 #define QUEUE_FLAG_DEFAULT      ((1 << QUEUE_FLAG_IO_STAT) |            \
                                  (1 << QUEUE_FLAG_CLUSTER) |            \
@@ -581,6 +582,7 @@ enum {
 
 #define blk_queue_plugged(q)    test_bit(QUEUE_FLAG_PLUGGED, &(q)->queue_flags)
 #define blk_queue_tagged(q)     test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)
+#define blk_queue_queuing(q)    test_bit(QUEUE_FLAG_CQ, &(q)->queue_flags)
 #define blk_queue_stopped(q)    test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)
 #define blk_queue_nomerges(q)   test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)
 #define blk_queue_nonrot(q)     test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)