The patch titled
Subject: mm/rmap: fixup copying of soft dirty and uffd ptes
has been added to the -mm tree. Its filename is
mm-rmap-fixup-copying-of-soft-dirty-and-uffd-ptes.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-rmap-fixup-copying-of-soft-dirty-and-uffd-ptes.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-rmap-fixup-copying-of-soft-dirty-and-uffd-ptes.patch
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------------------------------------------------------
From: Alistair Popple <alistair@xxxxxxxxxxxx>
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@xxxxxxxxxxxx
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@xxxxxxxxxxxx>
Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Alistair Popple <alistair@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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);
/*
_
Patches currently in -mm which might be from alistair@xxxxxxxxxxxx are
mm-migrate-fixup-setting-uffd_wp-flag.patch
mm-rmap-fixup-copying-of-soft-dirty-and-uffd-ptes.patch
