From mboxrd@z Thu Jan 1 00:00:00 1970 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 71457C7EE22 for ; Thu, 11 May 2023 13:14:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237915AbjEKNOj (ORCPT ); Thu, 11 May 2023 09:14:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33190 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237967AbjEKNOa (ORCPT ); Thu, 11 May 2023 09:14:30 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B95F77AA8 for ; Thu, 11 May 2023 06:14:28 -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 B62C6165C; Thu, 11 May 2023 06:15:12 -0700 (PDT) Received: from [10.1.34.59] (C02Z41KALVDN.cambridge.arm.com [10.1.34.59]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 47F383F5A1; Thu, 11 May 2023 06:14:27 -0700 (PDT) Message-ID: Date: Thu, 11 May 2023 14:14:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 Subject: Re: [PATCH v1 2/5] mm: damon must atomically clear young on ptes and pmds To: Andrew Morton , "Matthew Wilcox (Oracle)" , "Kirill A. Shutemov" , SeongJae Park Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, damon@lists.linux.dev References: <20230511125848.78621-1-ryan.roberts@arm.com> <20230511125848.78621-3-ryan.roberts@arm.com> From: Ryan Roberts In-Reply-To: <20230511125848.78621-3-ryan.roberts@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org My appologies for the noise: A blank line between Cc and Subject has broken the subject and grouping in lore. Please Ignore this, I will resend. On 11/05/2023 13:58, Ryan Roberts wrote: > 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 validate (and potentially > modify) the operation. > > Fixes: 46c3a0accdc4 ("mm/damon/vaddr: separate commonly usable functions") > Signed-off-by: Ryan Roberts > --- > 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; > } > > -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 long addr) > { > bool referenced = false; > struct folio *folio = 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; > > - if (pte_young(*pte)) { > + if (ptep_test_and_clear_young(vma, addr, pte)) > referenced = true; > - *pte = pte_mkold(*pte); > - } > > #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 = true; > #endif /* CONFIG_MMU_NOTIFIER */ > > @@ -62,7 +60,7 @@ void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr) > folio_put(folio); > } > > -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 long addr) > { > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > bool referenced = false; > @@ -71,13 +69,11 @@ void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, unsigned long addr) > if (!folio) > return; > > - if (pmd_young(*pmd)) { > + if (pmdp_test_and_clear_young(vma, addr, pmd)) > referenced = true; > - *pmd = pmd_mkold(*pmd); > - } > > #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 = true; > #endif /* CONFIG_MMU_NOTIFIER */ > > 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 @@ > > struct folio *damon_get_folio(unsigned long pfn); > > -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 long addr); > +void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr); > > 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 = 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 long addr, > } > > 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 long addr, > pte = 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;