Re: [PATCH v2 3/5] mm/memory_hotplug: use nth_page() in place of direct struct page manipulation.

[Zi Yan <ziy@nvidia.com>]

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On 6 Sep 2023, at 13:17, David Hildenbrand wrote:

> On 06.09.23 17:03, Zi Yan wrote:
>> From: Zi Yan <ziy@nvidia.com>
>
> Subject talks about "nth_page()" but that's not what this patch does.
>
>>
>> When dealing with hugetlb pages, manipulating struct page pointers
>> directly can get to wrong struct page, since struct page is not guaranteed
>> to be contiguous on SPARSEMEM without VMEMMAP. Use nth_page() to handle
>> it properly.
>
> ^ dito
>
>>
>> Fixes: eeb0efd071d8 ("mm,memory_hotplug: fix scan_movable_pages() for gigantic hugepages")
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Zi Yan <ziy@nvidia.com>
>> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
>> ---
>>   mm/memory_hotplug.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index 1b03f4ec6fd2..3b301c4023ff 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1689,7 +1689,7 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
>>   		 */
>>   		if (HPageMigratable(head))
>>   			goto found;
>> -		skip = compound_nr(head) - (page - head);
>> +		skip = compound_nr(head) - (pfn - page_to_pfn(head));
>>   		pfn += skip - 1;
>>   	}
>>   	return -ENOENT;
>
> I suspect systems without VMEMMAP also don't usually support gigantic pages AND hotunplug :)
>
> With the subject+description fixed
>
> Acked-by: David Hildenbrand <david@redhat.com>

Sure. Thanks.


--
Best Regards,
Yan, Zi

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