Hello Michal,
Mon, 19 Feb 2018 18:19:16 +0100 Michal Hocko wrote:
> On Mon 19-02-18 12:06:14, Masayoshi Mizuma wrote:
>> From: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
>>
>> struct page is inizialized as zero in __init_single_page().
>> If the page is offlined page, PG_reserved flag is set in early boot
>> time before __init_single_page(), so we should not clear the flag.
>>
>> The real problem is that we can not online the offlined page
>> through following sysfs operation because offlined page is
>> expected PG_reserved flag is set.
>> It is not needed the initialization, so remove it simply.
>>
>> Code:
>>
>> static int online_pages_range(unsigned long start_pfn,
>> ...
>> if (PageReserved(pfn_to_page(start_pfn))) <= HERE!!
>> for (i = 0; i < nr_pages; i++) {
>> page = pfn_to_page(start_pfn + i);
>> (*online_page_callback)(page);
>> onlined_pages++;
>> sysfs operation:
>>
>> # echo online > /sys/devices/system/node/node2/memory12288/online
>> # cat /sys/devices/system/node/node2/memory12288/online
>> 1
>> # cat /sys/devices/system/node/node2/meminfo
>> Node 2 MemTotal: 0 kB
>
> Nack. The patch is simply wrong. We do need to zero page for the boot
> pages. I believe the fix you are looking for is 9bb5a391f9a5 ("mm,
> memory_hotplug: fix memmap initialization"). Or do you still see a
> problem with this patch applied?
I have confirmed the problem is fixed by your patch 9bb5a391f9a5.
(I had tested it in 4.15.2, so I did not notice your patch, sorry)
Thank you for the fix!
- Masayoshi
>
>> Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap")
>> Signed-off-by: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx>
>> ---
>> mm/page_alloc.c | 1 -
>> 1 file changed, 1 deletion(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 76c9688..3260cd2 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -1179,7 +1179,6 @@ static void free_one_page(struct zone *zone,
>> static void __meminit __init_single_page(struct page *page, unsigned long pfn,
>> unsigned long zone, int nid)
>> {
>> - mm_zero_struct_page(page);
>> set_page_links(page, zone, nid, pfn);
>> init_page_count(page);
>> page_mapcount_reset(page);
>> --
>> 2.16.1
>>
>> - Masayoshi
>
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