From: Paul Gofman Date: Tue, 6 Feb 2024 08:48:01 +0000 (+0500) Subject: mm/migrate: preserve exact soft-dirty state X-Git-Tag: v6.9-rc1~107^2~284 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=055267feaecc9c6c53f128aa50746f64c4ef5ca2;p=linux-2.6-block.git mm/migrate: preserve exact soft-dirty state 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. Link: https://lkml.kernel.org/r/20240206084838.34560-1-usama.anjum@collabora.com Signed-off-by: Paul Gofman Signed-off-by: Muhammad Usama Anjum Acked-by: Andrei Vagin Cc: Michał Mirosław Signed-off-by: Andrew Morton --- 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))