Re: [PATCH 5/10] memory-hotplug : memory-hotplug: check page type in get_page_bootmem

Yasuaki Ishimatsu
2012-10-19T00:49:24Z

Hi Kosaki,

Sorry for late reply.

2012/10/13 4:28, KOSAKI Motohiro wrote:
> On Thu, Oct 4, 2012 at 10:32 PM, Yasuaki Ishimatsu
> <isimatu.yasuaki@jp.fujitsu.com> wrote:
>> The function get_page_bootmem() may be called more than one time to the same
>> page. There is no need to set page's type, private if the function is not
>> the first time called to the page.
>>
>> Note: the patch is just optimization and does not fix any problem.
>>
>> CC: David Rientjes <rientjes@google.com>
>> CC: Jiang Liu <liuj97@gmail.com>
>> CC: Len Brown <len.brown@intel.com>
>> CC: Christoph Lameter <cl@linux.com>
>> Cc: Minchan Kim <minchan.kim@gmail.com>
>> CC: Andrew Morton <akpm@linux-foundation.org>
>> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>> CC: Wen Congyang <wency@cn.fujitsu.com>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>> ---
>> mm/memory_hotplug.c | 15 +++++++++++----
>> 1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> Index: linux-3.6/mm/memory_hotplug.c
>> ===================================================================
>> --- linux-3.6.orig/mm/memory_hotplug.c 2012-10-04 18:29:58.284676075 +0900
>> +++ linux-3.6/mm/memory_hotplug.c 2012-10-04 18:30:03.454680542 +0900
>> @@ -95,10 +95,17 @@ static void release_memory_resource(stru
>> static void get_page_bootmem(unsigned long info, struct page *page,
>> unsigned long type)
>> {
>> - page->lru.next = (struct list_head *) type;
>> - SetPagePrivate(page);
>> - set_page_private(page, info);
>> - atomic_inc(&page->_count);
>> + unsigned long page_type;
>> +
>> + page_type = (unsigned long)page->lru.next;
>
> If I understand correctly, page->lru.next might be uninitialized yet.

Ah yes. I was misunderstanding...

Hi Wen,

When you update the physical hot remove patch-set, please drop the patch.

Thanks,
Yasuaki Ishimatsu

> Moreover, I have no seen any good effect in this patch. I don't understand
> why we need to increase code complexity.
>
>
>
>> + if (page_type < MEMORY_HOTPLUG_MIN_BOOTMEM_TYPE ||
>> + page_type > MEMORY_HOTPLUG_MAX_BOOTMEM_TYPE){
>> + page->lru.next = (struct list_head *)type;
>> + SetPagePrivate(page);
>> + set_page_private(page, info);
>> + atomic_inc(&page->_count);
>> + } else
>> + atomic_inc(&page->_count);
>> }
>>
>> /* reference to __meminit __free_pages_bootmem is valid
>>
>> --
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