block: make request_to_qc_t public

block consumers will need it for polling requests that
are sent with blk_execute_rq_nowait. Also, get rid of
blk_tag_to_qc_t and open-code it instead.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

include/linux/blk-mq.h

@@ -357,4 +357,14 @@ static inline void *blk_mq_rq_to_pdu(struct request *rq)
 	for ((i) = 0; (i) < (hctx)->nr_ctx &&				\
 	     ({ ctx = (hctx)->ctxs[(i)]; 1; }); (i)++)
 
+static inline blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx,
+		struct request *rq)
+{
+	if (rq->tag != -1)
+		return rq->tag | (hctx->queue_num << BLK_QC_T_SHIFT);
+
+	return rq->internal_tag | (hctx->queue_num << BLK_QC_T_SHIFT) |
+			BLK_QC_T_INTERNAL;
+}
+
 #endif