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Date: Wed, 08 May 2013 23:50:47 +0800
From: Jiang Liu <liuj97@gmail.com>
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Subject: Re: [PATCH v5, part3 11/15] mm: use a dedicated lock to protect totalram_pages
 and zone->managed_pages
References: <1368026235-5976-1-git-send-email-jiang.liu@huawei.com> <1368026235-5976-12-git-send-email-jiang.liu@huawei.com> <518A6EEC.6060102@redhat.com>
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To: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Jiang Liu <jiang.liu@huawei.com>, David Rientjes <rientjes@google.com>, Wen Congyang <wency@cn.fujitsu.com>, Mel Gorman <mgorman@suse.de>, Minchan Kim <minchan@kernel.org>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Michal Hocko <mhocko@suse.cz>, James Bottomley <James.Bottomley@HansenPartnership.com>, Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>, David Howells <dhowells@redhat.com>, Mark Salter <msalter@redhat.com>, Jianguo Wu <wujianguo@huawei.com>, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Michel Lespinasse <walken@google.com>

On 05/08/2013 11:27 PM, Rik van Riel wrote:
> On 05/08/2013 11:17 AM, Jiang Liu wrote:
> 
>> @@ -5186,6 +5189,15 @@ early_param("movablecore", cmdline_parse_movablecore);
>>
>>   #endif /* CONFIG_HAVE_MEMBLOCK_NODE_MAP */
>>
>> +void adjust_managed_page_count(struct page *page, long count)
>> +{
>> +    spin_lock(&managed_page_count_lock);
>> +    page_zone(page)->managed_pages += count;
>> +    totalram_pages += count;
>> +    spin_unlock(&managed_page_count_lock);
>> +}
>> +EXPORT_SYMBOL(adjust_managed_page_count);
>> +
> 
> Something I should have thought of when I reviewed the patch
> last time, but forgot...
> 
> What happens when the hotplug event adds more pages than fit
> in this zone, and some of the pages should go in the next
> zone?
> 
> For example, think about a 3GB x86_64 machine, which gets
> 2GB of memory hot-added. Roughly half may get added to the
> DMA32 zone, the rest to the NORMAL zone.
> 
> Do the callers of adjust_managed_page_count correctly make
> one call for each zone, or does the above code open up a
> window for a bug?
Hi Rik,
	Thanks for review! 
	Yes, the caller will make one call for each zone. Actually it will
call adjust_managed_page_count() for each page.
	Regards!
	Gerry

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