linux-kernel - Re: [PATCH] kernel/crash_core.c: No judgment required

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Message-ID: <20211214173242.192f47e8@rhtmp>
Date:   Tue, 14 Dec 2021 17:32:42 +0100
From:   Philipp Rudo <prudo@...hat.com>
To:     lizhe <sensor1010@....com>
Cc:     dyoung@...hat.com, bhe@...hat.com, vgoyal@...hat.com,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/crash_core.c: No judgment required

Hi lizhe,

On Thu,  9 Dec 2021 19:20:03 -0800
lizhe <sensor1010@....com> wrote:

> No judgment required ck_cmdline is NULL
> its caller has alreadly judged, see __parse_crashkernel
> function
> 
> Signed-off-by: lizhe <sensor1010@....com>
> ---
>  kernel/crash_core.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index eb53f5ec62c9..9981cf9b9fe4 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -221,9 +221,6 @@ static __init char *get_last_crashkernel(char *cmdline,
>  		p = strstr(p+1, name);
>  	}
>  
> -	if (!ck_cmdline)
> -		return NULL;
> -
>  	return ck_cmdline;
>  }
>  

I agree that the if-block is not needed and can be removed. However, I
cannot follow your reasoning in the commit message. Could you please
explain it in more detail.

The reason why I think that the 'if' can be removed is that the
expression can only be true when ck_cmdline = NULL. But with that the
last three lines are equivalent to

	if (!ck_cmdline)
		return ck_cmdline;

	return ck_cmdline;

Which simply doesn't make any sense.

Thanks
Philipp