On Tue, Feb 6, 2024 at 12:48 AM Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx> wrote: > > From: Paul Gofman <pgofman@xxxxxxxxxxxxxxx> > > pte_mkdirty() sets both _PAGE_DIRTY and _PAGE_SOFT_DIRTY bits. The > _PAGE_SOFT_DIRTY can get set even if it wasn't set on original page > before migration. This makes non-soft-dirty pages soft-dirty just > because of migration/compaction. Clear the _PAGE_SOFT_DIRTY flag if > it wasn't set on original page. > > By definition of soft-dirty feature, there can be spurious soft-dirty > pages because of kernel's internal activity such as VMA merging or > migration/compaction. This patch is eliminating the spurious soft-dirty > pages because of migration/compaction. > > Cc: Michał Mirosław <emmir@xxxxxxxxxx> > Cc: Andrei Vagin <avagin@xxxxxxxxx> Acked-by: Andrei Vagin <avagin@xxxxxxxxx> > Signed-off-by: Paul Gofman <pgofman@xxxxxxxxxxxxxxx> > Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx> > --- > mm/migrate.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index cc9f2bcd73b4..05d6ca437321 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -211,14 +211,17 @@ static bool remove_migration_pte(struct folio *folio, > folio_get(folio); > pte = mk_pte(new, READ_ONCE(vma->vm_page_prot)); > old_pte = ptep_get(pvmw.pte); > - if (pte_swp_soft_dirty(old_pte)) > - pte = pte_mksoft_dirty(pte); > > entry = pte_to_swp_entry(old_pte); > if (!is_migration_entry_young(entry)) > pte = pte_mkold(pte); > if (folio_test_dirty(folio) && is_migration_entry_dirty(entry)) > pte = pte_mkdirty(pte); > + if (pte_swp_soft_dirty(old_pte)) > + pte = pte_mksoft_dirty(pte); > + else > + pte = pte_clear_soft_dirty(pte); > + > if (is_writable_migration_entry(entry)) > pte = pte_mkwrite(pte, vma); > else if (pte_swp_uffd_wp(old_pte)) > -- > 2.42.0 >
