linux-kernel - Re: [PATCH v3 3/4] x86, kdump: Change crashkernel

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Date:	Tue, 09 Apr 2013 08:00:57 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Vivek Goyal <vgoyal@...hat.com>, Yinghai Lu <yinghai@...nel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	WANG Chao <chaowang@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] x86, kdump: Change crashkernel_high/low= to crashkernel=;high/low

Please, no semicolons. We already have established syntax for suboptions (option=suboption,suboption,...) and suboptions with parameters (option=suboption:value,...)

Vivek Goyal <vgoyal@...hat.com> wrote:

>On Thu, Apr 04, 2013 at 03:17:01PM -0700, Yinghai Lu wrote:
>
>[..]
>> @@ -1360,37 +1369,80 @@ static int __init parse_crashkernel_simp
>>  
>>  	if (*cur == '@')
>>  		*crash_base = memparse(cur+1, &cur);
>> -	else if (*cur != ' ' && *cur != '\0') {
>> -		pr_warning("crashkernel: unrecognized char\n");
>> -		return -EINVAL;
>> +	else {
>> +		int i;
>> +
>> +		/* check with known suffix */
>> +		for (i = 0; suffix_tbl[i]; i++)
>> +			if (!strncmp(cur, suffix_tbl[i], strlen(suffix_tbl[i])))
>> +				return 0;
>> +
>
>So crashkernel=X@Y;high is a valid syntax? Looks like we will reserve
>X amount of RAM at base Y and ignore "high" or "low".
>
>[..]
>>  static int __init __parse_crashkernel(char *cmdline,
>>  			     unsigned long long system_ram,
>>  			     unsigned long long *crash_size,
>>  			     unsigned long long *crash_base,
>> -				const char *name)
>> +			     const char *name,
>> +			     const char *suffix,
>> +			     bool simple_only)
>>  {
>> -	char 	*p = cmdline, *ck_cmdline = NULL;
>>  	char	*first_colon, *first_space;
>> +	char	*ck_cmdline;
>>  
>>  	BUG_ON(!crash_size || !crash_base);
>>  	*crash_size = 0;
>>  	*crash_base = 0;
>>  
>> -	/* find crashkernel and use the last one if there are more */
>> -	p = strstr(p, name);
>> -	while (p) {
>> -		ck_cmdline = p;
>> -		p = strstr(p+1, name);
>> -	}
>> +	ck_cmdline = get_last_crashkernel(cmdline, name, suffix);
>>  
>>  	if (!ck_cmdline)
>>  		return -EINVAL;
>> @@ -1403,23 +1455,30 @@ static int __init __parse_crashkernel(ch
>>  	 */
>>  	first_colon = strchr(ck_cmdline, ':');
>>  	first_space = strchr(ck_cmdline, ' ');
>> -	if (first_colon && (!first_space || first_colon < first_space))
>> -		return parse_crashkernel_mem(ck_cmdline, system_ram,
>> -				crash_size, crash_base);
>> -	else
>> +	if (first_colon && (!first_space || first_colon < first_space)) {
>> +		if (simple_only)
>> +			return -EINVAL;
>> +		else
>> +			return parse_crashkernel_mem(ck_cmdline, system_ram,
>> +					crash_size, crash_base);
>> +	} else
>>  		return parse_crashkernel_simple(ck_cmdline, crash_size,
>>  				crash_base);
>
>Why don't we structure it little differently. Now we seem to have 3 
>categories of crashkernel= parameters.
>
>- crashkernel_simple (crashkernel=X or crashkernel=X@Y)
>- crashkernel_mem (crashkernel=range:size,.....)
>- crashkerenl_high_low_suffix (crashkernel=X;high or crashkernel=Y;low)
>
>if (suffix) {
>	parse_crashkernel_high_low_suffix()
>} else {
>	if (first_colon.....)
>		parse_crashkernel_mem()
>	else
>		parse_crashkernel_simple();
>}
>
>And now you should not require "simple_only" function parameter and you
>can also do strict syntax checking for each type of crashkernel=
>parameter.
>
>Thanks
>Vivek

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