linux-kernel - Re: [PATCH] LoongArch: Delete debugfs checking

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Date:   Wed, 28 Jun 2023 22:22:20 +0800
From:   WANG Xuerui <kernel@...0n.name>
To:     Dan Carpenter <dan.carpenter@...aro.org>,
        Ivan Orlov <ivan.orlov0322@...il.com>,
        Immad Mir <mirimmad17@...il.com>
Cc:     Huacai Chen <chenhuacai@...nel.org>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] LoongArch: Delete debugfs checking

Hi,

On 2023/6/20 16:06, Dan Carpenter wrote:
> Debugfs functions are not supposed to be checked for errors.  This
> is sort of unusual but it is described in the comments for the
> debugfs_create_dir() function.  Also debugfs_create_dir() can never
> return NULL.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
> I spotted this code because I was looking at patches which were sent
> to stable but without a Fixes tag.  The correct way of checking for
> error pointers is not IS_ERR_OR_NULL(), it's IS_ERR().  When a function
> returns both error pointers and NULL, the NULL should be treated as a
> special kind of success.  Please see my blog for more details.
> 
> https://staticthinking.wordpress.com/2022/08/01/mixing-error-pointers-and-null/
> 
> I have not included a Fixes tag here, because it's not really a bug fix,
> it's just a clean up.

Thanks for the patch and sorry for the late review. I didn't notice this 
back then (just recovering from covid around that time) but since 
loongarch-next isn't tagged yet I think the patch could make it this 
cycle. (Somehow Huacai didn't see the mail either, weird...)

> 
>   arch/loongarch/kernel/unaligned.c | 2 --
>   1 file changed, 2 deletions(-)
> 
> diff --git a/arch/loongarch/kernel/unaligned.c b/arch/loongarch/kernel/unaligned.c
> index 85fae3d2d71a..3abf163dda05 100644
> --- a/arch/loongarch/kernel/unaligned.c
> +++ b/arch/loongarch/kernel/unaligned.c
> @@ -485,8 +485,6 @@ static int __init debugfs_unaligned(void)
>   	struct dentry *d;
>   
>   	d = debugfs_create_dir("loongarch", NULL);
> -	if (IS_ERR_OR_NULL(d))
> -		return -ENOMEM;
>   
>   	debugfs_create_u32("unaligned_instructions_user",
>   				S_IRUGO, d, &unaligned_instructions_user);

Trivial enough, thanks!

Reviewed-by: WANG Xuerui <git@...0n.name>

-- 
WANG "xen0n" Xuerui

Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/