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 850B5C00140 for ; Thu, 18 Aug 2022 07:38:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243764AbiHRHiF (ORCPT ); Thu, 18 Aug 2022 03:38:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243591AbiHRHiB (ORCPT ); Thu, 18 Aug 2022 03:38:01 -0400 Received: from out199-14.us.a.mail.aliyun.com (out199-14.us.a.mail.aliyun.com [47.90.199.14]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3FA62AB43A for ; Thu, 18 Aug 2022 00:37:59 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R211e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045170;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0VMZnOij_1660808275; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VMZnOij_1660808275) by smtp.aliyun-inc.com; Thu, 18 Aug 2022 15:37:56 +0800 From: Baolin Wang To: sj@kernel.org, akpm@linux-foundation.org Cc: baolin.wang@linux.alibaba.com, muchun.song@linux.dev, mike.kravetz@oracle.com, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/2] mm/damon: validate if the pmd entry is present before accessing Date: Thu, 18 Aug 2022 15:37:43 +0800 Message-Id: <58b1d1f5fbda7db49ca886d9ef6783e3dcbbbc98.1660805030.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The pmd_huge() is used to validate if the pmd entry is mapped by a huge page, also including the case of non-present (migration or hwpoisoned) pmd entry on arm64 or x86 architectures. That means the pmd_pfn() can not get the correct pfn number for the non-present pmd entry, which will cause damon_get_page() to get an incorrect page struct (also may be NULL by pfn_to_online_page()) to make the access statistics incorrect. Moreover it does not make sense that we still waste time to get the page of the non-present entry, just treat it as not-accessed and skip it, that keeps consistent with non-present pte level entry. Thus adding a pmd entry present validation to fix above issues. Signed-off-by: Baolin Wang Reviewed-by: SeongJae Park --- Changes from v1: - Update the commit message to make it more clear. - Add reviewed tag from SeongJae. --- mm/damon/vaddr.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c index 3c7b9d6..1d16c6c 100644 --- a/mm/damon/vaddr.c +++ b/mm/damon/vaddr.c @@ -304,6 +304,11 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr, if (pmd_huge(*pmd)) { ptl = pmd_lock(walk->mm, pmd); + if (!pmd_present(*pmd)) { + spin_unlock(ptl); + return 0; + } + if (pmd_huge(*pmd)) { damon_pmdp_mkold(pmd, walk->mm, addr); spin_unlock(ptl); @@ -431,6 +436,11 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr, #ifdef CONFIG_TRANSPARENT_HUGEPAGE if (pmd_huge(*pmd)) { ptl = pmd_lock(walk->mm, pmd); + if (!pmd_present(*pmd)) { + spin_unlock(ptl); + return 0; + } + if (!pmd_huge(*pmd)) { spin_unlock(ptl); goto regular_page; -- 1.8.3.1