From: Jens Axboe <axboe@kernel.dk>
Date: Wed, 13 Oct 2021 08:28:14 -0600
Subject: [PATCH] block: inline fast path of driver tag allocation
Git-commit: a808a9d545cdffb964f27239d1fc0c6e2330b424
Patch-mainline: v5.16-rc1
References: jsc#PED-1183

If we don't use an IO scheduler or have shared tags, then we don't need
to call into this external function at all. This saves ~2% for such
a setup.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/blk-mq.c |  8 +++-----
 block/blk-mq.h | 15 ++++++++++++++-
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3481a8712234..bf5936d72de8 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1324,7 +1324,7 @@ struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
 	return data.rq;
 }
 
-static bool __blk_mq_get_driver_tag(struct request *rq)
+static bool __blk_mq_alloc_driver_tag(struct request *rq)
 {
 	struct sbitmap_queue *bt = &rq->mq_hctx->tags->bitmap_tags;
 	unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
@@ -1348,11 +1348,9 @@ static bool __blk_mq_get_driver_tag(struct request *rq)
 	return true;
 }
 
-bool blk_mq_get_driver_tag(struct request *rq)
+bool __blk_mq_get_driver_tag(struct blk_mq_hw_ctx *hctx, struct request *rq)
 {
-	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
-
-	if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_get_driver_tag(rq))
+	if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_alloc_driver_tag(rq))
 		return false;
 
 	if ((hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) &&
diff --git a/block/blk-mq.h b/block/blk-mq.h
index ebf67f4d4f2e..d8ccb341e82e 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -258,7 +258,20 @@ static inline void blk_mq_put_driver_tag(struct request *rq)
 	__blk_mq_put_driver_tag(rq->mq_hctx, rq);
 }
 
-bool blk_mq_get_driver_tag(struct request *rq);
+bool __blk_mq_get_driver_tag(struct blk_mq_hw_ctx *hctx, struct request *rq);
+
+static inline bool blk_mq_get_driver_tag(struct request *rq)
+{
+	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
+
+	if (rq->tag != BLK_MQ_NO_TAG &&
+	    !(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
+		hctx->tags->rqs[rq->tag] = rq;
+		return true;
+	}
+
+	return __blk_mq_get_driver_tag(hctx, rq);
+}
 
 static inline void blk_mq_clear_mq_map(struct blk_mq_queue_map *qmap)
 {
-- 
2.35.3