Re: [PATCH -next] bcache: use DEFINE_MUTEX() for mutex lock

[Coly Li <colyli@suse.de>]

On 4/5/21 6:14 PM, Zheng Yongjun wrote:
> mutex lock can be initialized automatically with DEFINE_MUTEX()
> rather than explicitly calling mutex_init().
> 
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>

NACK. This is not the first time people try to "fix" this location...

Using DEFINE_MUTEX() does not gain anything for us, it will generate
unnecessary extra size for the bcache.ko.
ines.

> ---
>  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 78c08a8aece8..c124da6e646d 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -41,7 +41,7 @@ static const char invalid_uuid[] = {
>  };
>  
>  static struct kobject *bcache_kobj;
> -struct mutex bch_register_lock;


Hmm, maybe if you compose a patch to add comments for bch_register_lock,
for something like: Don't initialize global variable here. It might be
helpful for noticing people not to fixing this in future.

Thanks.

Coly Li

> +DEFINE_MUTEX(bch_register_lock);
>  bool bcache_is_reboot;
>  LIST_HEAD(bch_cache_sets);
>  static LIST_HEAD(uncached_devices);
> @@ -2870,7 +2870,6 @@ static int __init bcache_init(void)
>  
>  	check_module_parameters();
>  
> -	mutex_init(&bch_register_lock);
>  	init_waitqueue_head(&unregister_wait);
>  	register_reboot_notifier(&reboot);
>  
>