linux-kernel - Re: [PATCH v2 3/8] crash_core: change parse_crashkernel() to support crashkernel=,high|low parsing

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Date:   Mon, 4 Sep 2023 10:47:58 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...weicloud.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        catalin.marinas@....com, thunder.leizhen@...wei.com,
        dyoung@...hat.com, prudo@...hat.com, samuel.holland@...ive.com,
        kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org
Subject: Re: [PATCH v2 3/8] crash_core: change parse_crashkernel() to support
 crashkernel=,high|low parsing



On 2023/9/1 17:49, Baoquan He wrote:
>>> +
>>> +		*high = true;
>>> +	} else if (ret || !*crash_size) {
>> This check can be moved outside of #ifdef. Because even '!high', it's completely
>> applicable. The overall adjustment is as follows:
> Hmm, the current logic is much easier to understand. However, I may not
> 100% get your suggestion. Can you paste the complete code in your
> suggested way? Do not need 100% correct code, just the skeleton of code logic
> so that I can better understand it and add inline comment.

int __init parse_crashkernel(...)
{
	int ret;

	/* crashkernel=X[@offset] */
	ret = __parse_crashkernel(cmdline, system_ram, crash_size,
				crash_base, NULL);

#ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
	if (high && ret == -ENOENT) {
		... ...		//The code for your original branch "else if (ret == -ENOENT) {"
		ret = 0;	//Added based on the next discussion
	}
+#endif

 	if (!*crash_size)
		ret = -EINVAL;

	return ret;
}

> 
>> -  	if (!high)
>> -  		return ret;
>>
>> #ifdef CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
>> 	if (high && ret == -ENOENT) {
>> 		... ...
>> 		if (ret || !*crash_size)	//parse HIGH
>> 		... ...
>> 	}
>>
>> 	//At this point, *crash_size is not 0 and ret is 0.
>> 	//We can also delete if (!*crash_size) above because it will be checked later.
>> #endif
>>
>> 	if (!*crash_size)
>> 		ret = -EINVAL;
>>
>> 	return ret;
> When crashkernel=,high is specified while crashkernel=,low is omitted,
> the ret==-ENOENT, but we can't return ret directly. That is still an
> acceptable way.

Oh, yes. Sorry, I didn't notice branch "ret==-ENOENT" didn't return. So "ret = 0;"
needs to be added.

	if (high && ret == -ENOENT) {
		... ...
		*high = true;
+		ret = 0;
	}

> 
>> -  	return 0;
>>
>>> +		/* The specified value is invalid */
>>> +		return -1;
>>> +	}
>>> +#endif
>>>  	return 0;
>>>  }
>>>  
>>>

-- 
Regards,
  Zhen Lei