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")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
mm/rmap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index c6c4d4ea29a7..17fbfa61f7ef 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);
--
2.48.1
