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SubjectRe: [PATCH 3/3] acpi, memory-hotplug: Support getting hotplug info from SRAT.
On 02/05/2013 07:26 AM, Andrew Morton wrote:
> On Fri, 25 Jan 2013 17:42:09 +0800
> Tang Chen<tangchen@cn.fujitsu.com> wrote:
>
>> We now provide an option for users who don't want to specify physical
>> memory address in kernel commandline.
>>
>> /*
>> * For movablemem_map=acpi:
>> *
>> * SRAT: |_____| |_____| |_________| |_________| ......
>> * node id: 0 1 1 2
>> * hotpluggable: n y y n
>> * movablemem_map: |_____| |_________|
>> *
>> * Using movablemem_map, we can prevent memblock from allocating memory
>> * on ZONE_MOVABLE at boot time.
>> */
>>
>> So user just specify movablemem_map=acpi, and the kernel will use hotpluggable
>> info in SRAT to determine which memory ranges should be set as ZONE_MOVABLE.
>>
>> ...
>>
>> + if (!strncmp(p, "acpi", max(4, strlen(p))))
>> + movablemem_map.acpi = true;
>
> Generates a warning:
>
> mm/page_alloc.c: In function 'cmdline_parse_movablemem_map':
> mm/page_alloc.c:5312: warning: comparison of distinct pointer types lacks a cast
>
> due to max(int, size_t).
>
> This is easily fixed, but the code looks rather pointless. If the
> incoming string is supposed to be exactly "acpi" then use strcmp(). If
> the incoming string must start with "acpi" then use strncmp(p, "acpi", 4).
>
> IOW, the max is unneeded?

Hi Andrew,

I think I made another mistake here. I meant to use min(4, strlen(p)) in
case p is
something like 'aaa' whose length is less then 4. But I mistook it with
max().

But after I dig into strcmp() in the kernel, I think it is OK to use
strcmp().
min() or max() is not needed.

Thanks. :)

>
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