[dm-devel] [PATCH 1/9] blk-mq: Introduce blk_mq_queue_stopped()

[Bart Van Assche]

The function blk_queue_stopped() allows to test whether or not a
non-mq queue has been stopped. Introduce a helper function that
allows block drivers to query easily whether or not one or more
hardware contexts of a blk-mq queue have been stopped.

Signed-off-by: Bart Van Assche <bart.vanassche at sandisk.com>
Cc: Jens Axboe <axboe at fb.com>
Cc: Christoph Hellwig <hch at lst.de>
---
 block/blk-mq.c         | 17 +++++++++++++++++
 include/linux/blk-mq.h |  1 +
 2 files changed, 18 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0dcafa6..6929a52 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -965,6 +965,23 @@ void blk_mq_run_hw_queues(struct request_queue *q, bool async)
 }
 EXPORT_SYMBOL(blk_mq_run_hw_queues);
 
+/*
+ * The caller is responsible for serializing this function against
+ * blk_mq_{start,stop}_hw_queue().
+ */
+bool blk_mq_queue_stopped(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int i;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		if (test_bit(BLK_MQ_S_STOPPED, &hctx->state))
+			return true;
+
+	return false;
+}
+EXPORT_SYMBOL(blk_mq_queue_stopped);
+
 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
 {
 	cancel_delayed_work(&hctx->run_work);
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index e43bbff..bd677bc 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -235,6 +235,7 @@ void blk_mq_kick_requeue_list(struct request_queue *q);
 void blk_mq_abort_requeue_list(struct request_queue *q);
 void blk_mq_complete_request(struct request *rq, int error);
 
+bool blk_mq_queue_stopped(struct request_queue *q);
 void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx);
 void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx);
 void blk_mq_stop_hw_queues(struct request_queue *q);
-- 
2.9.3