From nobody Sat Feb 7 13:41:08 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 51B84C001DE for ; Mon, 17 Jul 2023 19:30:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231500AbjGQTaZ (ORCPT ); Mon, 17 Jul 2023 15:30:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230522AbjGQTaV (ORCPT ); Mon, 17 Jul 2023 15:30:21 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5EC18E1; Mon, 17 Jul 2023 12:30:20 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id EE9E86122B; Mon, 17 Jul 2023 19:30:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 282DCC433C8; Mon, 17 Jul 2023 19:30:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689622219; bh=B3lKcl6AG4VzLC8vKc3oOwsXsHm9qE0hLnyJCufjkwQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tZBQ0hW12YiHopMYlgU/iscjagmj++kFnsMTRjCXXss4RiQSZmC+t1AoqGLtwSH/Q ApRemcZP1v8V0m6UAxS1FT0C/s3o6IyBBx980E6uz1JTeeg30qeLdFNpeh9eiAS9UO ypGzf+fanyWIUa5996eXCNxKos8nrQJD3hXn+b51BlcSEZIg2QtnqOntZITca/GM3F rWSt60S2igAtbmHSzNBLFkG3/oW96LvlEHPby+FkCu4ayFcG44Y4eOBUCl49O4AGum zt7XLhr0V/n4IPtlkN1uJL/Pb9V6soEQ9Rdl6aqDNqN/1So3uIzt8vuoZTSC0w4ClN Q5VPS8kggiT0Q== From: SeongJae Park To: gregkh@linuxfoundation.org Cc: ryan.roberts@arm.com, akpm@linux-foundation.org, hch@lst.de, kirill.shutemov@linux.intel.com, lstoakes@gmail.com, rppt@kernel.org, sj@kernel.org, stable@vger.kernel.org, urezki@gmail.com, willy@infradead.org, yuzhao@google.com, ziy@nvidia.com, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 5.15.y] mm/damon/ops-common: atomically test and clear young on ptes and pmds Date: Mon, 17 Jul 2023 19:30:08 +0000 Message-Id: <20230717193008.122040-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <2023071613-reminder-relapse-b922@gregkh> References: <2023071613-reminder-relapse-b922@gregkh> 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" From: Ryan Roberts commit c11d34fa139e4b0fb4249a30f37b178353533fa1 upstream. 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. Link: https://lkml.kernel.org/r/20230602092949.545577-3-ryan.roberts@arm.com 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) Cc: Christoph Hellwig Cc: Kirill A. Shutemov Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Uladzislau Rezki (Sony) Cc: Yu Zhao Cc: Signed-off-by: Andrew Morton Signed-off-by: SeongJae Park --- This is a manual backport of the commit, which cannot cleanly cherry-picked on 5.15.y[1], on 5.15.y, specifically 5.15.120. [1] https://lore.kernel.org/stable/2023071613-reminder-relapse-b922@gregkh/ mm/damon/vaddr.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index 1945196fd743..6ad96da15081 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -393,7 +393,7 @@ static struct page *damon_get_page(unsigned long pfn) return page; } =20 -static void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, +static void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr) { bool referenced =3D false; @@ -402,13 +402,11 @@ static void damon_ptep_mkold(pte_t *pte, struct mm_st= ruct *mm, if (!page) 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 @@ -419,7 +417,7 @@ static void damon_ptep_mkold(pte_t *pte, struct mm_stru= ct *mm, put_page(page); } =20 -static void damon_pmdp_mkold(pmd_t *pmd, struct mm_struct *mm, +static void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr) { #ifdef CONFIG_TRANSPARENT_HUGEPAGE @@ -429,13 +427,11 @@ static void damon_pmdp_mkold(pmd_t *pmd, struct mm_st= ruct *mm, if (!page) 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, + if (mmu_notifier_clear_young(vma->vm_mm, addr, addr + ((1UL) << HPAGE_PMD_SHIFT))) referenced =3D true; #endif /* CONFIG_MMU_NOTIFIER */ @@ -462,7 +458,7 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned l= ong addr, } =20 if (pmd_huge(*pmd)) { - damon_pmdp_mkold(pmd, walk->mm, addr); + damon_pmdp_mkold(pmd, walk->vma, addr); spin_unlock(ptl); return 0; } @@ -474,7 +470,7 @@ 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