linux-kernel - [PATCH] block: make block

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Date: Tue, 05 Mar 2024 16:32:16 -0300
From: "Ricardo B. Marliere" <ricardo@...liere.net>
To: Jens Axboe <axboe@...nel.dk>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
 "Ricardo B. Marliere" <ricardo@...liere.net>
Subject: [PATCH] block: make block_class constant

Since commit 43a7206b0963 ("driver core: class: make class_register() take
a const *"), the driver core allows for struct class to be in read-only
memory, so move the block_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@...liere.net>
---
 block/genhd.c          | 2 +-
 drivers/base/base.h    | 2 +-
 include/linux/blkdev.h | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 84c822d989da..a214f9cf3a35 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1201,7 +1201,7 @@ static int block_uevent(const struct device *dev, struct kobj_uevent_env *env)
 	return add_uevent_var(env, "DISKSEQ=%llu", disk->diskseq);
 }

-struct class block_class = {
+const struct class block_class = {
 	.name		= "block",
 	.dev_uevent	= block_uevent,
 };
diff --git a/drivers/base/base.h b/drivers/base/base.h
index eb4c0ace9242..0738ccad08b2 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -207,7 +207,7 @@ static inline int devtmpfs_init(void) { return 0; }
 #endif

 #ifdef CONFIG_BLOCK
-extern struct class block_class;
+extern const struct class block_class;
 static inline bool is_blockdev(struct device *dev)
 {
 	return dev->class == &block_class;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 285e82723d64..19c7596f4ebf 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -42,7 +42,7 @@ struct blk_crypto_profile;

 extern const struct device_type disk_type;
 extern const struct device_type part_type;
-extern struct class block_class;
+extern const struct class block_class;

 /*
  * Maximum number of blkcg policies allowed to be registered concurrently.

---
base-commit: 8b4ecbe5270032cf73b464b3a25c5eb25c7be71c
change-id: 20240305-class_cleanup-block-78db91ce02dd

Best regards,
-- 
Ricardo B. Marliere <ricardo@...liere.net>