[PATCH v4 2/4] blk-mq: Add blk_mq_delay_run_hw_queues() API call

[Douglas Anderson <dianders@chromium.org>]

We have:
* blk_mq_run_hw_queue()
* blk_mq_delay_run_hw_queue()
* blk_mq_run_hw_queues()

...but not blk_mq_delay_run_hw_queues(), presumably because nobody
needed it before now.  Since we need it for a later patch in this
series, add it.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v4: None
Changes in v3:
- ("blk-mq: Add blk_mq_delay_run_hw_queues() API call") new for v3

Changes in v2: None

 block/blk-mq.c         | 19 +++++++++++++++++++
 include/linux/blk-mq.h |  1 +
 2 files changed, 20 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2cd8d2b49ff4..ea0cd970a3ff 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1537,6 +1537,25 @@ void blk_mq_run_hw_queues(struct request_queue *q, bool async)
 }
 EXPORT_SYMBOL(blk_mq_run_hw_queues);
 
+/**
+ * blk_mq_delay_run_hw_queues - Run all hardware queues asynchronously.
+ * @q: Pointer to the request queue to run.
+ * @msecs: Microseconds of delay to wait before running the queues.
+ */
+void blk_mq_delay_run_hw_queues(struct request_queue *q, unsigned long msecs)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int i;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (blk_mq_hctx_stopped(hctx))
+			continue;
+
+		blk_mq_delay_run_hw_queue(hctx, msecs);
+	}
+}
+EXPORT_SYMBOL(blk_mq_delay_run_hw_queues);
+
 /**
  * blk_mq_queue_stopped() - check whether one or more hctxs have been stopped
  * @q: request queue.
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 11cfd6470b1a..405f8c196517 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -503,6 +503,7 @@ void blk_mq_unquiesce_queue(struct request_queue *q);
 void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs);
 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
 void blk_mq_run_hw_queues(struct request_queue *q, bool async);
+void blk_mq_delay_run_hw_queues(struct request_queue *q, unsigned long msecs);
 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 		busy_tag_iter_fn *fn, void *priv);
 void blk_mq_tagset_wait_completed_request(struct blk_mq_tag_set *tagset);
-- 
2.26.0.292.g33ef6b2f38-goog