linux-kernel - Re: [PATCH v2 -next] md: bcache: use DEFINE

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Date:   Thu, 24 Dec 2020 22:47:00 +0800
From:   Coly Li <colyli@...e.de>
To:     Zheng Yongjun <zhengyongjun3@...wei.com>,
        kent.overstreet@...il.com, linux-bcache@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 -next] md: bcache: use DEFINE_MUTEX() for mutex lock

On 12/24/20 9:24 PM, Zheng Yongjun wrote:
> mutex lock can be initialized automatically with DEFINE_MUTEX()
> rather than explicitly calling mutex_init().
> 
> Signed-off-by: Zheng Yongjun <zhengyongjun3@...wei.com>

NACK. For this case, it is unnecessary to initialize a global variable
so early in declaration, this change makes bcache.ko bigger and I don't
see any benefit.

Coly Li

> ---
>  drivers/md/bcache/super.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index 46a00134a36a..963d62a15f37 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -40,7 +40,7 @@ static const char invalid_uuid[] = {
>  };
>  
>  static struct kobject *bcache_kobj;
> -struct mutex bch_register_lock;
> +DEFINE_MUTEX(bch_register_lock);
>  bool bcache_is_reboot;
>  LIST_HEAD(bch_cache_sets);
>  static LIST_HEAD(uncached_devices);
> @@ -2832,7 +2832,6 @@ static int __init bcache_init(void)
>  
>  	check_module_parameters();
>  
> -	mutex_init(&bch_register_lock);
>  	init_waitqueue_head(&unregister_wait);
>  	register_reboot_notifier(&reboot);
>  
>