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 9C70BC25B08 for ; Thu, 18 Aug 2022 03:39:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242742AbiHRDj4 (ORCPT ); Wed, 17 Aug 2022 23:39:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35800 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230520AbiHRDjy (ORCPT ); Wed, 17 Aug 2022 23:39:54 -0400 Received: from out0.migadu.com (out0.migadu.com [IPv6:2001:41d0:2:267::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C255C910AC for ; Wed, 17 Aug 2022 20:39:52 -0700 (PDT) Content-Type: text/plain; charset=utf-8 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1660793991; h=from:from: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=KUyb1pCJ/oDKXbqiOy+EBzbV0azHcNvfFJQrGl3ZoHw=; b=gIhBAaU7YmXiHcaDggk8vcGCT/7goON9W/+NsVTSgVmBy6E225FzyIxchhWQApf2XJrVie V21+ZScwyj2b3RR3WN4NscXIwuFvxme4sQB+4d7KVTA/NIfjk5omvZGiF0r+v2TUhS8TB8 24xGn49o7Z9SXlFXOQRwLvA0orm9wXk= MIME-Version: 1.0 Subject: Re: [PATCH] mm/damon: Validate if the pmd entry is present before accessing X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: Date: Thu, 18 Aug 2022 11:39:04 +0800 Cc: sj@kernel.org, Andrew Morton , damon@lists.linux.dev, Linux MM , linux-kernel@vger.kernel.org, Mike Kravetz Content-Transfer-Encoding: quoted-printable Message-Id: <6F99AE03-3C74-4E5B-87E1-6F3232BEEBB5@linux.dev> References: <2838b6737bc259cf575ff11fd1c4b7fdb340fa73.1660717122.git.baolin.wang@linux.alibaba.com> <5173E308-2403-4667-9162-865CF7F11838@linux.dev> To: Baolin Wang X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Aug 18, 2022, at 10:57, Baolin Wang = wrote: >=20 >=20 >=20 > =E5=9C=A8 8/18/2022 10:41 AM, Muchun Song =E5=86=99=E9=81=93: >>> On Aug 17, 2022, at 14:21, Baolin Wang = wrote: >>>=20 >>> 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. >>>=20 >>> Signed-off-by: Baolin Wang >>> --- >>> mm/damon/vaddr.c | 10 ++++++++++ >>> 1 file changed, 10 insertions(+) >>>=20 >>> 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, >>>=20 >>> if (pmd_huge(*pmd)) { >>> ptl =3D 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=E2=80=99s better to put = the check after >> pmd_huge. >=20 > 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. Well, I thought it is hugetlb related since I saw the usage of pmd_huge. = If it is THP case, why not use pmd_trans_huge? Thanks. >=20 >> 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 =3D pmd_lock(walk->mm, pmd); >>> + if (!pmd_present(*pmd)) { >>> + spin_unlock(ptl); >>> + return 0; >>> + } >>> + >>> if (!pmd_huge(*pmd)) { >>> spin_unlock(ptl); >>> goto regular_page; >>> --=20 >>> 1.8.3.1