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

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Message-ID: <561B0ECD.5000507@huawei.com>
Date:	Mon, 12 Oct 2015 09:37:17 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Yasuaki Ishimatsu <yasu.isimatu@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>,
	"David Rientjes" <rientjes@...gle.com>,
	Tang Chen <tangchen@...fujitsu.com>, <zhongjiang@...wei.com>,
	Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: skip if required_kernelcore is larger than totalpages

On 2015/10/9 23:41, Yasuaki Ishimatsu wrote:

> 
> On Thu, 8 Oct 2015 10:21:05 +0800
> Xishi Qiu <qiuxishi@...wei.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;
		...

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@...wei.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
>>
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@...ck.org.  For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
> 
> .
> 



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