mm/rmap: fixup copying of soft dirty and uffd ptes

During memory migration a pte is temporarily replaced with a migration
swap pte.  Some pte bits from the existing mapping such as the soft-dirty
and uffd write-protect bits are preserved by copying these to the
temporary migration swap pte.

However these bits are not stored at the same location for swap and
non-swap ptes.  Therefore testing these bits requires using the
appropriate helper function for the given pte type.

Unfortunately several code locations were found where the wrong helper
function is being used to test soft_dirty and uffd_wp bits which leads to
them getting incorrectly set or cleared during page-migration.

Fix these by using the correct tests based on pte type.

Fixes: a56ecb24d40e ("mm/migrate: support un-addressable ZONE_DEVICE page in migration")
Fixes: 3b4c5288d4b6 ("mm/migrate: migrate_vma() unmap page from vma while collecting pages")
Fixes: 2dd1c0fd164d ("userfaultfd: wp: support swap and page migration")
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Alistair Popple <alistair@popple.id.au>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200825064232.10023-2-alistair@popple.id.au
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/migrate.c b/mm/migrate.c
index ddb64253fe3ea373538ff55700323a9e5ebff8b0..12f63806d0ac6015f0ef3235d598eb2b792be84f 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2427,10 +2427,17 @@ again:
                        entry = make_migration_entry(page, mpfn &
                                                     MIGRATE_PFN_WRITE);
                        swp_pte = swp_entry_to_pte(entry);
-                       if (pte_soft_dirty(pte))
-                               swp_pte = pte_swp_mksoft_dirty(swp_pte);
-                       if (pte_uffd_wp(pte))
-                               swp_pte = pte_swp_mkuffd_wp(swp_pte);
+                       if (pte_present(pte)) {
+                               if (pte_soft_dirty(pte))
+                                       swp_pte = pte_swp_mksoft_dirty(swp_pte);
+                               if (pte_uffd_wp(pte))
+                                       swp_pte = pte_swp_mkuffd_wp(swp_pte);
+                       } else {
+                               if (pte_swp_soft_dirty(pte))
+                                       swp_pte = pte_swp_mksoft_dirty(swp_pte);
+                               if (pte_swp_uffd_wp(pte))
+                                       swp_pte = pte_swp_mkuffd_wp(swp_pte);
+                       }
                        set_pte_at(mm, addr, ptep, swp_pte);
 
                        /*

diff --git a/mm/rmap.c b/mm/rmap.c
index 83cc459edc407fc26392df777bebd15ce5df419b..9425260774a1f0d034d6a3d434ff153b6e7e8440 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1511,9 +1511,14 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
                         */
                        entry = make_migration_entry(page, 0);
                        swp_pte = swp_entry_to_pte(entry);
-                       if (pte_soft_dirty(pteval))
+
+                       /*
+                        * pteval maps a zone device page and is therefore
+                        * a swap pte.
+                        */
+                       if (pte_swp_soft_dirty(pteval))
                                swp_pte = pte_swp_mksoft_dirty(swp_pte);
-                       if (pte_uffd_wp(pteval))
+                       if (pte_swp_uffd_wp(pteval))
                                swp_pte = pte_swp_mkuffd_wp(swp_pte);
                        set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
                        /*