From: Christoph Hellwig <hch@lst.de>
Date: Tue, 15 Feb 2022 11:05:36 +0100
Subject: [PATCH] blk-mq: make the blk-mq stacking code optional
Git-commit: 248c793359daacd826a7507a258ffe41653efef7
Patch-mainline: v5.18-rc1
References: jsc#PED-1183

The code to stack blk-mq drivers is only used by dm-multipath, and
will preferably stay that way.  Make it optional and only selected
by device mapper, so that the buildbots more easily catch abuses
like the one that slipped in in the ufs driver in the last merged
window.  Another positive side effects is that kernel builds without
device mapper shrink a little bit as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Link: https://lore.kernel.org/r/20220215100540.3892965-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/Kconfig      | 3 +++
 block/blk-mq.c     | 2 ++
 drivers/md/Kconfig | 1 +
 3 files changed, 6 insertions(+)

diff --git a/block/Kconfig b/block/Kconfig
index 205f8d01c695..168b873eb666 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -230,6 +230,9 @@ config BLK_PM
 config BLOCK_HOLDER_DEPRECATED
 	bool
 
+config BLK_MQ_STACKING
+	bool
+
 source "block/Kconfig.iosched"
 
 endif # BLOCK
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6c59ffe765fd..db62d34afb63 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2840,6 +2840,7 @@ void blk_mq_submit_bio(struct bio *bio)
 				blk_mq_try_issue_directly(rq->mq_hctx, rq));
 }
 
+#ifdef CONFIG_BLK_MQ_STACKING
 /**
  * blk_cloned_rq_check_limits - Helper function to check a cloned request
  *                              for the new queue limits
@@ -3017,6 +3018,7 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
 	return -ENOMEM;
 }
 EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
+#endif /* CONFIG_BLK_MQ_STACKING */
 
 /*
  * Steal bios from a request and add them to a bio list.
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index b5ea378e66cb..998a5cfdbc4e 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -204,6 +204,7 @@ config BLK_DEV_DM
 	tristate "Device mapper support"
 	select BLOCK_HOLDER_DEPRECATED if SYSFS
 	select BLK_DEV_DM_BUILTIN
+	select BLK_MQ_STACKING
 	depends on DAX || DAX=n
 	help
 	  Device-mapper is a low level volume manager.  It works by allowing
-- 
2.35.3