block: move blk_mq_tag_to_rq() inline

This is in the fast path of driver issue or completion, and it's a single
array index operation. Move it inline to avoid a function call for it.

This does mean making struct blk_mq_tags block layer public, but there's
not really much in there.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq-tag.h

@@ -4,29 +4,6 @@
 
 struct blk_mq_alloc_data;
 
-/*
- * Tag address space map.
- */
-struct blk_mq_tags {
-	unsigned int nr_tags;
-	unsigned int nr_reserved_tags;
-
-	atomic_t active_queues;
-
-	struct sbitmap_queue bitmap_tags;
-	struct sbitmap_queue breserved_tags;
-
-	struct request **rqs;
-	struct request **static_rqs;
-	struct list_head page_list;
-
-	/*
-	 * used to clear request reference in rqs[] before freeing one
-	 * request pool
-	 */
-	spinlock_t lock;
-};
-
 extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags,
 					unsigned int reserved_tags,
 					int node, int alloc_policy);

block/blk-mq.c

@@ -1120,17 +1120,6 @@ void blk_mq_delay_kick_requeue_list(struct request_queue *q,
 }
 EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);
 
-struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
-{
-	if (tag < tags->nr_tags) {
-		prefetch(tags->rqs[tag]);
-		return tags->rqs[tag];
-	}
-
-	return NULL;
-}
-EXPORT_SYMBOL(blk_mq_tag_to_rq);
-
 static bool blk_mq_rq_inflight(struct blk_mq_hw_ctx *hctx, struct request *rq,
 			       void *priv, bool reserved)
 {

include/linux/blk-mq.h

@@ -7,6 +7,7 @@
 #include <linux/srcu.h>
 #include <linux/lockdep.h>
 #include <linux/scatterlist.h>
+#include <linux/prefetch.h>
 
 struct blk_mq_tags;
 struct blk_flush_queue;
@@ -675,7 +676,40 @@ struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
 struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
 		unsigned int op, blk_mq_req_flags_t flags,
 		unsigned int hctx_idx);
-struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag);
+
+/*
+ * Tag address space map.
+ */
+struct blk_mq_tags {
+	unsigned int nr_tags;
+	unsigned int nr_reserved_tags;
+
+	atomic_t active_queues;
+
+	struct sbitmap_queue bitmap_tags;
+	struct sbitmap_queue breserved_tags;
+
+	struct request **rqs;
+	struct request **static_rqs;
+	struct list_head page_list;
+
+	/*
+	 * used to clear request reference in rqs[] before freeing one
+	 * request pool
+	 */
+	spinlock_t lock;
+};
+
+static inline struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags,
+					       unsigned int tag)
+{
+	if (tag < tags->nr_tags) {
+		prefetch(tags->rqs[tag]);
+		return tags->rqs[tag];
+	}
+
+	return NULL;
+}
 
 enum {
 	BLK_MQ_UNIQUE_TAG_BITS = 16,