linux-kernel - Re: [PATCH v21 1/5] kdump: return -ENOENT if required cmdline option does not exist

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Date:   Tue, 15 Mar 2022 21:32:10 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Baoquan He <bhe@...hat.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        <x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>,
        <linux-kernel@...r.kernel.org>, Dave Young <dyoung@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        <kexec@...ts.infradead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        <devicetree@...r.kernel.org>, "Jonathan Corbet" <corbet@....net>,
        <linux-doc@...r.kernel.org>, Randy Dunlap <rdunlap@...radead.org>,
        Feng Zhou <zhoufeng.zf@...edance.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Chen Zhou <dingguo.cz@...group.com>,
        "John Donnelly" <John.p.donnelly@...cle.com>,
        Dave Kleikamp <dave.kleikamp@...cle.com>
Subject: Re: [PATCH v21 1/5] kdump: return -ENOENT if required cmdline option
 does not exist



On 2022/3/15 20:21, Baoquan He wrote:
> On 03/15/22 at 07:57pm, Baoquan He wrote:
>> 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.
>>>
>>> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.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;
>>
>> Firstly, I am not sure if '-ENOENT' is a right value to return. From the
>> code comment of ENOENT, it's used for file or dir?
>> #define ENOENT           2      /* No such file or directory */

This error code does not return to user mode, so there is no problem.
There are a lot of places in the kernel that are used this way. For example:

int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
{
	if (!cpu_stop_queue_work(cpu, &work))
		return -ENOENT;

>>
>> Secondly, we ever discussed the case including
>>  - no crashkernel=,low is provided;
>>  - messy code is provied, e.g crashkernel=aaaaaabbbb,low
> 
> Checking the 3rd pach, this is handled. Take back my below words,
> continue reviewing.

Yes.

> 
>>
>> The 2nd one is not handled in this patchset. How about taking the
>> handling into another round of patches. This patchset just adds
>> crashkernel=,high purely.
>>
>>>  
>>>  	ck_cmdline += strlen(name);
>>>  
>>> -- 
>>> 2.25.1
>>>
>>
> 
> .
> 

-- 
Regards,
  Zhen Lei