From nobody Mon Feb 9 01:29:21 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F4DDC7EE24 for ; Fri, 2 Jun 2023 09:31:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235056AbjFBJbU (ORCPT ); Fri, 2 Jun 2023 05:31:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234751AbjFBJak (ORCPT ); Fri, 2 Jun 2023 05:30:40 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D6334E68 for ; Fri, 2 Jun 2023 02:30:07 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 13E121764; Fri, 2 Jun 2023 02:30:53 -0700 (PDT) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.26]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DD7893F7BD; Fri, 2 Jun 2023 02:30:05 -0700 (PDT) From: Ryan Roberts To: Andrew Morton , SeongJae Park , Christoph Hellwig Cc: Ryan Roberts , "Matthew Wilcox (Oracle)" , "Kirill A. Shutemov" , Lorenzo Stoakes , Uladzislau Rezki , Zi Yan , Yu Zhao , Mike Rapoport , linux-kernel@vger.kernel.org, linux-mm@kvack.org, damon@lists.linux.dev Subject: [PATCH v3 2/4] mm/damon/ops-common: atomically test and clear young on ptes and pmds Date: Fri, 2 Jun 2023 10:29:47 +0100 Message-Id: <20230602092949.545577-3-ryan.roberts@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230602092949.545577-1-ryan.roberts@arm.com> References: <20230602092949.545577-1-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" It is racy to non-atomically read a pte, then clear the young bit, then write it back as this could discard dirty information. Further, it is bad practice to directly set a pte entry within a table. Instead clearing young must go through the arch-provided helper, ptep_test_and_clear_young() to ensure it is modified atomically and to give the arch code visibility and allow it to check (and potentially modify) the operation. Fixes: 3f49584b262c ("mm/damon: implement primitives for the virtual memory= address spaces"). Signed-off-by: Ryan Roberts Reviewed-by: Zi Yan Reviewed-by: SeongJae Park Reviewed-by: Mike Rapoport (IBM) --- mm/damon/ops-common.c | 16 ++++++---------- mm/damon/ops-common.h | 4 ++-- mm/damon/paddr.c | 4 ++-- mm/damon/vaddr.c | 4 ++-- 4 files changed, 12 insertions(+), 16 deletions(-) diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c index cc63cf953636..acc264b97903 100644 --- a/mm/damon/ops-common.c +++ b/mm/damon/ops-common.c @@ -37,7 +37,7 @@ struct folio *damon_get_folio(unsigned long pfn) return folio; } =20 -void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr) +void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned lon= g addr) { bool referenced =3D false; struct folio *folio =3D damon_get_folio(pte_pfn(*pte)); @@ -45,13 +45,11 @@ void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm,= unsigned long addr) if (!folio) return; =20 - if (pte_young(*pte)) { + if (ptep_test_and_clear_young(vma, addr, pte)) referenced =3D true; - *pte =3D pte_mkold(*pte); - } =20 #ifdef CONFIG_MMU_NOTIFIER - if (mmu_notifier_clear_young(mm, addr, addr + PAGE_SIZE)) + if (mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE)) referenced =3D true; #endif /* CONFIG_MMU_NOTIFIER */ =20 @@ -62,7 +60,7 @@ void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, u= nsigned long addr) folio_put(folio); } =20 -void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr) +void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned lon= g addr) { #ifdef CONFIG_TRANSPARENT_HUGEPAGE bool referenced =3D false; @@ -71,13 +69,11 @@ void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm,= unsigned long addr) if (!folio) return; =20 - if (pmd_young(*pmd)) { + if (pmdp_test_and_clear_young(vma, addr, pmd)) referenced =3D true; - *pmd =3D pmd_mkold(*pmd); - } =20 #ifdef CONFIG_MMU_NOTIFIER - if (mmu_notifier_clear_young(mm, addr, addr + HPAGE_PMD_SIZE)) + if (mmu_notifier_clear_young(vma->vm_mm, addr, addr + HPAGE_PMD_SIZE)) referenced =3D true; #endif /* CONFIG_MMU_NOTIFIER */ =20 diff --git a/mm/damon/ops-common.h b/mm/damon/ops-common.h index 14f4bc69f29b..18d837d11bce 100644 --- a/mm/damon/ops-common.h +++ b/mm/damon/ops-common.h @@ -9,8 +9,8 @@ =20 struct folio *damon_get_folio(unsigned long pfn); =20 -void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr= ); -void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr= ); +void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned lon= g addr); +void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned lon= g addr); =20 int damon_cold_score(struct damon_ctx *c, struct damon_region *r, struct damos *s); diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c index 467b99166b43..5b3a3463d078 100644 --- a/mm/damon/paddr.c +++ b/mm/damon/paddr.c @@ -24,9 +24,9 @@ static bool __damon_pa_mkold(struct folio *folio, struct = vm_area_struct *vma, while (page_vma_mapped_walk(&pvmw)) { addr =3D pvmw.address; if (pvmw.pte) - damon_ptep_mkold(pvmw.pte, vma->vm_mm, addr); + damon_ptep_mkold(pvmw.pte, vma, addr); else - damon_pmdp_mkold(pvmw.pmd, vma->vm_mm, addr); + damon_pmdp_mkold(pvmw.pmd, vma, addr); } return true; } diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index 1fec16d7263e..37994fb6120c 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -311,7 +311,7 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned l= ong addr, } =20 if (pmd_trans_huge(*pmd)) { - damon_pmdp_mkold(pmd, walk->mm, addr); + damon_pmdp_mkold(pmd, walk->vma, addr); spin_unlock(ptl); return 0; } @@ -323,7 +323,7 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned l= ong addr, pte =3D pte_offset_map_lock(walk->mm, pmd, addr, &ptl); if (!pte_present(*pte)) goto out; - damon_ptep_mkold(pte, walk->mm, addr); + damon_ptep_mkold(pte, walk->vma, addr); out: pte_unmap_unlock(pte, ptl); return 0; --=20 2.25.1