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

[David Hildenbrand]

On 06.09.23 17:03, Zi Yan wrote:
> From: Zi Yan <ziy@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
>   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@xxxxxxxxxx>

--
Cheers,

David / dhildenb