linux-kernel - Re: [PATCH v5 08/14] memory-hotplug: Common APIs to support page tables hot-remove

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Date:	Wed, 26 Dec 2012 11:19:56 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Jianguo Wu <wujianguo@...wei.com>
CC:	akpm@...ux-foundation.org, rientjes@...gle.com, liuj97@...il.com,
	len.brown@...el.com, benh@...nel.crashing.org, paulus@...ba.org,
	cl@...ux.com, minchan.kim@...il.com,
	kosaki.motohiro@...fujitsu.com, isimatu.yasuaki@...fujitsu.com,
	wency@...fujitsu.com, hpa@...or.com, linfeng@...fujitsu.com,
	laijs@...fujitsu.com, mgorman@...e.de, yinghai@...nel.org,
	x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
	linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
	linux-ia64@...r.kernel.org, cmetcalf@...era.com,
	sparclinux@...r.kernel.org
Subject: Re: [PATCH v5 08/14] memory-hotplug: Common APIs to support page
 tables hot-remove

On 12/26/2012 11:11 AM, Tang Chen wrote:
> On 12/26/2012 10:49 AM, Tang Chen wrote:
>> On 12/25/2012 04:17 PM, Jianguo Wu wrote:
>>>> +
>>>> +static void __meminit free_pagetable(struct page *page, int order)
>>>> +{
>>>> + struct zone *zone;
>>>> + bool bootmem = false;
>>>> + unsigned long magic;
>>>> +
>>>> + /* bootmem page has reserved flag */
>>>> + if (PageReserved(page)) {
>>>> + __ClearPageReserved(page);
>>>> + bootmem = true;
>>>> +
>>>> + magic = (unsigned long)page->lru.next;
>>>> + if (magic == SECTION_INFO || magic == MIX_SECTION_INFO)
>
> And also, I think we don't need to check MIX_SECTION_INFO since it is
> for the pageblock_flags, not the memmap in the section.

Oh, no :)

We also need to check MIX_SECTION_INFO because we set pgd, pud, pmd
pages as MIX_SECTION_INFO in register_page_bootmem_memmap() in patch6.

Thanks. :)

>
> Thanks. :)
>
>>>> + put_page_bootmem(page);
>>>
>>> Hi Tang,
>>>
>>> For removing memmap of sparse-vmemmap, in cpu_has_pse case, if magic
>>> == SECTION_INFO,
>>> the order will be get_order(PMD_SIZE), so we need a loop here to put
>>> all the 512 pages.
>>>
>> Hi Wu,
>>
>> Thanks for reminding me that. I truely missed it.
>>
>> And since in register_page_bootmem_info_section(), a whole memory
>> section will be set as SECTION_INFO, I think we don't need to check
>> the page magic one by one, just the first one is enough. :)
>>
>> I will fix it, thanks. :)
>>
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>
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