mm/hugetlb: use folio->lru int demote_free_hugetlb_folios()

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().

Link: https://lkml.kernel.org/r/20250113131611.2554758-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 308b0e3876b52f317a9e0fb11b14fd568a35f0ae..87761b042ed04a96cb5502f777ef1d1d465bbd4f 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3826,13 +3826,15 @@ 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);
                }
        }