We are demoting hugetlb folios to smaller hugetlb folios; let's avoid
messing with pages where avoidable and handle it more similar to
__split_huge_page_tail().

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/hugetlb.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index bc4ab45d9b93b..a94d52dd53728 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3822,13 +3822,15 @@ static long demote_free_hugetlb_folios(struct hstate *src, struct hstate *dst,
 
 		for (i = 0; i < pages_per_huge_page(src); i += pages_per_huge_page(dst)) {
 			struct page *page = folio_page(folio, i);
+			/* Careful: see __split_huge_page_tail() */
+			struct folio *new_folio = (struct folio *)page;
 
-			page->mapping = NULL;
 			clear_compound_head(page);
 			prep_compound_page(page, dst->order);
 
-			init_new_hugetlb_folio(dst, page_folio(page));
-			list_add(&page->lru, &dst_list);
+			new_folio->mapping = NULL;
+			init_new_hugetlb_folio(dst, new_folio);
+			list_add(&new_folio->lru, &dst_list);
 		}
 	}
 
-- 
2.47.1

On 1/13/25 8:16 AM, David Hildenbrand wrote:
> We are demoting hugetlb folios to smaller hugetlb folios; let's avoid
> messing with pages where avoidable and handle it more similar to
> __split_huge_page_tail().
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>   mm/hugetlb.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index bc4ab45d9b93b..a94d52dd53728 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3822,13 +3822,15 @@ static long demote_free_hugetlb_folios(struct hstate *src, struct hstate *dst,
>   
>   		for (i = 0; i < pages_per_huge_page(src); i += pages_per_huge_page(dst)) {
>   			struct page *page = folio_page(folio, i);
> +			/* Careful: see __split_huge_page_tail() */
> +			struct folio *new_folio = (struct folio *)page;
>   
> -			page->mapping = NULL;
>   			clear_compound_head(page);
>   			prep_compound_page(page, dst->order);
>   
> -			init_new_hugetlb_folio(dst, page_folio(page));
> -			list_add(&page->lru, &dst_list);
> +			new_folio->mapping = NULL;
> +			init_new_hugetlb_folio(dst, new_folio);
> +			list_add(&new_folio->lru, &dst_list);
>   		}
>   	}
>   

Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>