[PATCH V2 2/5] blk-mq: introduce blk_mq_get_queue_depth()

[Ming Lei]

The hardware queue depth can be resized via blk_mq_update_nr_requests(),
so introduce this helper for retrieving queue's depth easily.

Signed-off-by: Ming Lei <ming....@redhat.com>
---
 block/blk-mq.c | 12 ++++++++++++
 block/blk-mq.h |  1 +
 2 files changed, 13 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 095099df041f..be475ad112ec 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2120,6 +2120,18 @@ static void blk_mq_map_swqueue(struct request_queue *q,
        }
 }
 
+/*
+ * Queue depth can be changed via blk_mq_update_nr_requests(),
+ * so use this helper to retrieve queue's depth.
+ */
+int blk_mq_get_queue_depth(struct request_queue *q)
+{
+       /* All queues have same queue depth */
+       struct blk_mq_tags      *tags = q->tag_set->tags[0];
+
+       return tags->bitmap_tags.sb.depth + tags->breserved_tags.sb.depth;
+}
+
 static void queue_set_hctx_shared(struct request_queue *q, bool shared)
 {
        struct blk_mq_hw_ctx *hctx;
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 2814a14e529c..8085d5989cf5 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -166,6 +166,7 @@ void __blk_mq_finish_request(struct blk_mq_hw_ctx *hctx, 
struct blk_mq_ctx *ctx,
 void blk_mq_finish_request(struct request *rq);
 struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data,
                                        unsigned int op);
+int blk_mq_get_queue_depth(struct request_queue *q);
 
 static inline bool blk_mq_hctx_stopped(struct blk_mq_hw_ctx *hctx)
 {
-- 
2.9.3