[PATCH v3 3/5] mm/memory_hotplug: use pfn math in place of direct struct page manipulation.

[Zi Yan]

From: Zi Yan <ziy@xxxxxxxxxx>

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 pfn calculation to
handle it properly.

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>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
---
 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;
-- 
2.40.1