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

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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>


David / dhildenb

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