Messages in this thread Patch in this message | | | From | Muhammad Usama Anjum <> | Subject | [PATCH] mm/migrate: preserve exact soft-dirty state | Date | Tue, 6 Feb 2024 13:48:01 +0500 |
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From: Paul Gofman <pgofman@codeweavers.com>
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@google.com> Cc: Andrei Vagin <avagin@gmail.com> Signed-off-by: Paul Gofman <pgofman@codeweavers.com> Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com> --- 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
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