Re: [PATCH] mm: skip if required_kernelcore is larger than totalpages

[Tang Chen <tangchen@cn.fujitsu.com>]

Hi, Qiu

The patch seems OK to me. Only one little concern below.

On 10/12/2015 09:37 AM, Xishi Qiu wrote:
> On 2015/10/9 23:41, Yasuaki Ishimatsu wrote:
>
>> On Thu, 8 Oct 2015 10:21:05 +0800
>> Xishi Qiu <qiuxishi@huawei.com> wrote:
>>
>>> If kernelcore was not specified, or the kernelcore size is zero
>>> (required_movablecore >= totalpages), or the kernelcore size is larger
>> Why does required_movablecore become larger than totalpages, when the
>> kernelcore size is zero? I read the code but I could not find that you
>> mention.
>>
> If user only set boot option movablecore, and the value is larger than
> totalpages, the calculation of kernelcore is zero, but we can't fill
> the zone only with kernelcore, so skip it.
>
> I have send a patch before this patch.
> "fix overflow in find_zone_movable_pfns_for_nodes()"
> 		...
>   		required_movablecore =
>   			roundup(required_movablecore, MAX_ORDER_NR_PAGES);
> +		required_movablecore = min(totalpages, required_movablecore);
>   		corepages = totalpages - required_movablecore;
> 		...


So if required_movablecore >= totalpages, there won't be any ZONE_MOVABLE.
How about add a warning or debug info to tell the user he has specified a
too large movablecore, and it is ignored ?

Thanks.


>
> Thanks,
> Xishi Qiu
>
>> Thanks,
>> Yasuaki Ishimatsu
>>
>>> than totalpages, there is no ZONE_MOVABLE. We should fill the zone
>>> with both kernel memory and movable memory.
>>>
>>> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
>>> ---
>>>   mm/page_alloc.c | 7 +++++--
>>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index af3c9bd..6a6da0d 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -5674,8 +5674,11 @@ static void __init find_zone_movable_pfns_for_nodes(void)
>>>   		required_kernelcore = max(required_kernelcore, corepages);
>>>   	}
>>>   
>>> -	/* If kernelcore was not specified, there is no ZONE_MOVABLE */
>>> -	if (!required_kernelcore)
>>> +	/*
>>> +	 * If kernelcore was not specified or kernelcore size is larger
>>> +	 * than totalpages, there is no ZONE_MOVABLE.
>>> +	 */
>>> +	if (!required_kernelcore || required_kernelcore >= totalpages)
>>>   		goto out;
>>>   
>>>   	/* usable_startpfn is the lowest possible pfn ZONE_MOVABLE can be at */
>>> -- 
>>> 2.0.0
>>>
>>>
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>> .
>>
>
>
> .
>

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