blk-mq: let blk_mq_tag_to_rq() take blk_mq_tags as the main parameter

We currently pass in the hardware queue, and get the tags from there.
But from scsi-mq, with a shared tag space, it's a lot more convenient
to pass in the blk_mq_tags instead as the hardware queue isn't always
directly available. So instead of having to re-map to a given
hardware queue from rq->mq_ctx, just pass in the tags structure.

Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -529,15 +529,20 @@ void blk_mq_kick_requeue_list(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_mq_kick_requeue_list);
 
-struct request *blk_mq_tag_to_rq(struct blk_mq_hw_ctx *hctx, unsigned int tag)
+static inline bool is_flush_request(struct request *rq, unsigned int tag)
 {
-	struct request_queue *q = hctx->queue;
+	return ((rq->cmd_flags & REQ_FLUSH_SEQ) &&
+			rq->q->flush_rq->tag == tag);
+}
 
-	if ((q->flush_rq->cmd_flags & REQ_FLUSH_SEQ) &&
-	    q->flush_rq->tag == tag)
-		return q->flush_rq;
+struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
+{
+	struct request *rq = tags->rqs[tag];
 
-	return hctx->tags->rqs[tag];
+	if (!is_flush_request(rq, tag))
+		return rq;
+
+	return rq->q->flush_rq;
 }
 EXPORT_SYMBOL(blk_mq_tag_to_rq);
 
@@ -566,7 +571,7 @@ static void blk_mq_timeout_check(void *__data, unsigned long *free_tags)
 		if (tag >= hctx->tags->nr_tags)
 			break;
 
-		rq = blk_mq_tag_to_rq(hctx, tag++);
+		rq = blk_mq_tag_to_rq(hctx->tags, tag++);
 		if (rq->q != hctx->queue)
 			continue;
 		if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))

drivers/block/mtip32xx/mtip32xx.c

@@ -193,7 +193,9 @@ static void mtip_put_int_command(struct driver_data *dd, struct mtip_cmd *cmd)
 static struct request *mtip_rq_from_tag(struct driver_data *dd,
 					unsigned int tag)
 {
-	return blk_mq_tag_to_rq(dd->queue->queue_hw_ctx[0], tag);
+	struct blk_mq_hw_ctx *hctx = dd->queue->queue_hw_ctx[0];
+
+	return blk_mq_tag_to_rq(hctx->tags, tag);
 }
 
 static struct mtip_cmd *mtip_cmd_from_tag(struct driver_data *dd,

include/linux/blk-mq.h

@@ -155,7 +155,7 @@ void blk_mq_free_request(struct request *rq);
 bool blk_mq_can_queue(struct blk_mq_hw_ctx *);
 struct request *blk_mq_alloc_request(struct request_queue *q, int rw,
 		gfp_t gfp, bool reserved);
-struct request *blk_mq_tag_to_rq(struct blk_mq_hw_ctx *hctx, unsigned int tag);
+struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int 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);