blk-mq: Export if requests were started

Drivers can iterate over all allocated request tags, but their callback
needs a way to know if the driver started the request in the first place.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index d0de259..addf8a19 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -194,6 +194,7 @@
 struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *, const int ctx_index);
 struct blk_mq_hw_ctx *blk_mq_alloc_single_hw_queue(struct blk_mq_tag_set *, unsigned int, int);
 
+int blk_mq_request_started(struct request *rq);
 void blk_mq_start_request(struct request *rq);
 void blk_mq_end_request(struct request *rq, int error);
 void __blk_mq_end_request(struct request *rq, int error);