| Message ID | 20250129115411.2077152-3-david@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: fixes for device-exclusive entries (hmm) | expand |
On Wed, Jan 29, 2025 at 12:54:00PM +0100, David Hildenbrand wrote: > 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. Agreed, thanks for fixing. Reviewed-by: Alistair Popple <apopple@nvidia.com> > Fixes: b756a3b5e7ea ("mm: device exclusive memory access") > 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 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 >
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);
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@vger.kernel.org> Signed-off-by: David Hildenbrand <david@redhat.com> --- mm/rmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)