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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE5C4C25B08 for ; Thu, 18 Aug 2022 02:57:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1682B8D0002; Wed, 17 Aug 2022 22:57:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 117A98D0001; Wed, 17 Aug 2022 22:57:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 02CCA8D0002; Wed, 17 Aug 2022 22:57:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id EBBF48D0001 for ; Wed, 17 Aug 2022 22:57:15 -0400 (EDT) Received: from smtpin18.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id C195F1602E2 for ; Thu, 18 Aug 2022 02:57:15 +0000 (UTC) X-FDA: 79811201988.18.CD7DD0A Received: from out30-54.freemail.mail.aliyun.com (out30-54.freemail.mail.aliyun.com [115.124.30.54]) by imf14.hostedemail.com (Postfix) with ESMTP id E8BCC1001C2 for ; Thu, 18 Aug 2022 02:57:13 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046059;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VMYubQo_1660791429; Received: from 30.97.48.48(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VMYubQo_1660791429) by smtp.aliyun-inc.com; Thu, 18 Aug 2022 10:57:10 +0800 Message-ID: Date: Thu, 18 Aug 2022 10:57:21 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH] mm/damon: Validate if the pmd entry is present before accessing To: Muchun Song Cc: sj@kernel.org, Andrew Morton , damon@lists.linux.dev, Linux MM , linux-kernel@vger.kernel.org, Mike Kravetz References: <2838b6737bc259cf575ff11fd1c4b7fdb340fa73.1660717122.git.baolin.wang@linux.alibaba.com> <5173E308-2403-4667-9162-865CF7F11838@linux.dev> From: Baolin Wang In-Reply-To: <5173E308-2403-4667-9162-865CF7F11838@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=none; spf=pass (imf14.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.54 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660791435; a=rsa-sha256; cv=none; b=XJHelmt+qjrnL723u8pBsXl3+gJ95AUXR7tSM+88ZfqSmZIWqD8pjIhOxV15doiRxHd9dE m7JMghKbwvgNvH4wC09p4IzH5rRRSdRRznnUsMnUsa39+nedZO53qjLVJjhmX87FqjWVDL tyD6I7VjUmdeDYRUL60B+uGW7067jwY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660791435; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BugxK2ENxWJrWWz+94GG96+opV/kLvKTkgRw1Q1ecHM=; b=xGGnXWyq1WhbHagxH4/+g2vilVS1pnNoK1B+98sZ9qfybiiTICST2d9XMhOimyglk66mAt JW4l+GIvG5SAXKyI1g9Xa0GskoUQoDo5jMRkjH1AKSuTKXnWAq2NuFCwBIFcH6wWtXrQD4 J/i9x7XxvHmP4zc1bcJjEvERatnJfsY= Authentication-Results: imf14.hostedemail.com; dkim=none; spf=pass (imf14.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.54 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=alibaba.com X-Stat-Signature: ujjcjruaba7cdw8nwwwyb7bdp38a8sh8 X-Rspamd-Queue-Id: E8BCC1001C2 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1660791433-779229 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 在 8/18/2022 10:41 AM, Muchun Song 写道: > > >> On Aug 17, 2022, at 14:21, Baolin Wang wrote: >> >> 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. Thus we should validate if it >> is present before making the pmd entry old or getting young state, >> otherwise we can not get the correct corresponding page. >> >> Signed-off-by: Baolin Wang >> --- >> 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)) { > > Unluckily, we should use pte_present here. See commit c9d398fa23788. We can use > huge_ptep_get() to get a hugetlb pte, so it’s better to put the check after > pmd_huge. IMO this is not the case for hugetlb, and the hugetlb case will be handled by damon_mkold_hugetlb_entry(), which already used pte_present() for hugetlb case. > > Cc Mike to make sure I am not missing something. > > Muchun, > Thanks. > >> + 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 >> >> >