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>

block/blk-mq.c

@@ -404,6 +404,12 @@ void blk_mq_complete_request(struct request *rq)
 }
 EXPORT_SYMBOL(blk_mq_complete_request);
 
+int blk_mq_request_started(struct request *rq)
+{
+	return test_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
+}
+EXPORT_SYMBOL_GPL(blk_mq_request_started);
+
 void blk_mq_start_request(struct request *rq)
 {
 	struct request_queue *q = rq->q;

include/linux/blk-mq.h

@@ -194,6 +194,7 @@ static inline u16 blk_mq_unique_tag_to_tag(u32 unique_tag)
 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);