From: Alistair Popple alistair@popple.id.au Subject: 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.

Link: https://lkml.kernel.org/r/20200825064232.10023-2-alistair@popple.id.au Fixes: a5430dda8a3a ("mm/migrate: support un-addressable ZONE_DEVICE page in migration") Fixes: 8c3328f1f36a ("mm/migrate: migrate_vma() unmap page from vma while collecting pages") Fixes: f45ec5ff16a7 ("userfaultfd: wp: support swap and page migration") Signed-off-by: Alistair Popple alistair@popple.id.au 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 Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/migrate.c | 15 +++++++++++---- mm/rmap.c | 9 +++++++-- 2 files changed, 18 insertions(+), 6 deletions(-)

--- a/mm/migrate.c~mm-rmap-fixup-copying-of-soft-dirty-and-uffd-ptes +++ a/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);

/* --- a/mm/rmap.c~mm-rmap-fixup-copying-of-soft-dirty-and-uffd-ptes +++ a/mm/rmap.c @@ -1511,9 +1511,14 @@ static bool try_to_unmap_one(struct page */ 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); /* _