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Date:   Wed, 16 Mar 2022 13:39:44 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Zhen Lei <thunder.leizhen@huawei.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
        linux-kernel@vger.kernel.org, Dave Young <dyoung@redhat.com>,
        Vivek Goyal <vgoyal@redhat.com>,
        Eric Biederman <ebiederm@xmission.com>,
        kexec@lists.infradead.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        devicetree@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
        linux-doc@vger.kernel.org, Randy Dunlap <rdunlap@infradead.org>,
        Feng Zhou <zhoufeng.zf@bytedance.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Chen Zhou <dingguo.cz@antgroup.com>,
        John Donnelly <John.p.donnelly@oracle.com>,
        Dave Kleikamp <dave.kleikamp@oracle.com>
Subject: Re: [PATCH v21 1/5] kdump: return -ENOENT if required cmdline option
 does not exist
Message-ID: <YjF4IMuMlVDMYOas@MiWiFi-R3L-srv>
References: <20220227030717.1464-1-thunder.leizhen@huawei.com>
 <20220227030717.1464-2-thunder.leizhen@huawei.com>
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In-Reply-To: <20220227030717.1464-2-thunder.leizhen@huawei.com>
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On 02/27/22 at 11:07am, Zhen Lei wrote:
> The crashkernel=Y,low is an optional command-line option. When it doesn't
> exist, kernel will try to allocate minimum required memory below 4G
> automatically. Give it a unique error code to distinguish it from other
> error scenarios.

This log is a little confusing. __parse_crashkernel() has three callers. 
 - parse_crashkernel()
 - parse_crashkernel_high()
 - parse_crashkernel_low()

How about tuning the git log as below:

==================
According to the current crashkernel=Y,low support in other ARCHes, it's
an optional command-line option. When it doesn't exist, kernel will try
to allocate minimum required memory below 4G automatically. 

However, __parse_crashkernel() returns '-EINVAL' for all error cases. It
can't distinguish the nonexistent option from invalid option. 

Change __parse_crashkernel() to return '-ENOENT' for the nonexistent option
case. With this change, crashkernel,low memory will take the default
value if crashkernel=,low is not specified; while crashkernel reservation
will fail and bail out if an invalid option is specified.
==================

> 
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
>  kernel/crash_core.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
>  kernel/crash_core.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 256cf6db573cd09..4d57c03714f4e13 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -243,9 +243,8 @@ static int __init __parse_crashkernel(char *cmdline,
>  	*crash_base = 0;
>  
>  	ck_cmdline = get_last_crashkernel(cmdline, name, suffix);
> -
>  	if (!ck_cmdline)
> -		return -EINVAL;
> +		return -ENOENT;
>  
>  	ck_cmdline += strlen(name);
>  
> -- 
> 2.25.1
>