Even though FOLL_SPLIT_PMD on hugetlb now always fails with -EOPNOTSUPP, let's add a safety net in case FOLL_SPLIT_PMD usage would ever be reworked.

In particular, before commit 9cb28da54643 ("mm/gup: handle hugetlb in the generic follow_page_mask code"), GUP(FOLL_SPLIT_PMD) would just have returned a page. In particular, hugetlb folios that are not PMD-sized would never have been prone to FOLL_SPLIT_PMD.

hugetlb folios can be anonymous, and page_make_device_exclusive_one() is not really prepared for handling them at all. So let's spell that out.

Fixes: b756a3b5e7ea ("mm: device exclusive memory access") Reviewed-by: Alistair Popple apopple@nvidia.com Cc: stable@vger.kernel.org Signed-off-by: David Hildenbrand david@redhat.com --- mm/rmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/rmap.c b/mm/rmap.c index c6c4d4ea29a7e..17fbfa61f7efb 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2499,7 +2499,7 @@ static bool folio_make_device_exclusive(struct folio *folio, * Restrict to anonymous folios for now to avoid potential writeback * issues. */ - if (!folio_test_anon(folio)) + if (!folio_test_anon(folio) || folio_test_hugetlb(folio)) return false;

rmap_walk(folio, &rwc);