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 X-Spam-Level: X-Spam-Status: No, score=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 028C1C433E1 for ; Thu, 13 Aug 2020 05:28:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A2F0620715 for ; Thu, 13 Aug 2020 05:28:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A2F0620715 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2399E6B0008; Thu, 13 Aug 2020 01:28:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1C3E46B000A; Thu, 13 Aug 2020 01:28:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 067636B000C; Thu, 13 Aug 2020 01:28:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0116.hostedemail.com [216.40.44.116]) by kanga.kvack.org (Postfix) with ESMTP id DF54D6B0008 for ; Thu, 13 Aug 2020 01:28:15 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id A306745BC for ; Thu, 13 Aug 2020 05:28:15 +0000 (UTC) X-FDA: 77144414550.28.peace26_410301726ff1 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin28.hostedemail.com (Postfix) with ESMTP id 743E86C3C for ; Thu, 13 Aug 2020 05:28:15 +0000 (UTC) X-HE-Tag: peace26_410301726ff1 X-Filterd-Recvd-Size: 3305 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf45.hostedemail.com (Postfix) with ESMTP for ; Thu, 13 Aug 2020 05:28:14 +0000 (UTC) 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 12B4F30E; Wed, 12 Aug 2020 22:28:14 -0700 (PDT) Received: from [192.168.0.129] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 308053F6CF; Wed, 12 Aug 2020 22:28:11 -0700 (PDT) From: Anshuman Khandual Subject: Re: [PATCH 13/16] debug_vm_pgtable/pmd_clear: Don't use pmd/pud_clear on pte entries To: "Aneesh Kumar K.V" , linux-mm@kvack.org, akpm@linux-foundation.org Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org References: <20200812063358.369514-1-aneesh.kumar@linux.ibm.com> <20200812063358.369514-13-aneesh.kumar@linux.ibm.com> Message-ID: <1bb841d2-4622-b122-7176-246eb3702c9f@arm.com> Date: Thu, 13 Aug 2020 10:57:41 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200812063358.369514-13-aneesh.kumar@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 743E86C3C X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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: On 08/12/2020 12:03 PM, Aneesh Kumar K.V wrote: > pmd_clear() should not be used to clear pmd level pte entries. Could you please elaborate on this. The proposed change set does not match the description here. > > Signed-off-by: Aneesh Kumar K.V > --- > mm/debug_vm_pgtable.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index 061c19bba7f0..529892b9be2f 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -191,6 +191,8 @@ static void __init pmd_advanced_tests(struct mm_struct *mm, > pmd = READ_ONCE(*pmdp); > WARN_ON(pmd_young(pmd)); > > + /* Clear the pte entries */ > + pmdp_huge_get_and_clear(mm, vaddr, pmdp); > pgtable = pgtable_trans_huge_withdraw(mm, pmdp); > } > > @@ -313,6 +315,8 @@ static void __init pud_advanced_tests(struct mm_struct *mm, > pudp_test_and_clear_young(vma, vaddr, pudp); > pud = READ_ONCE(*pudp); > WARN_ON(pud_young(pud)); > + > + pudp_huge_get_and_clear(mm, vaddr, pudp); > } > > static void __init pud_leaf_tests(unsigned long pfn, pgprot_t prot) > @@ -431,8 +435,6 @@ static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp, > * This entry points to next level page table page. > * Hence this must not qualify as pud_bad(). > */ > - pmd_clear(pmdp); > - pud_clear(pudp); Both entires are cleared before creating a fresh page table entry. Why that is a problem. > pud_populate(mm, pudp, pmdp); > pud = READ_ONCE(*pudp); > WARN_ON(pud_bad(pud)); > @@ -564,7 +566,6 @@ static void __init pmd_populate_tests(struct mm_struct *mm, pmd_t *pmdp, > * This entry points to next level page table page. > * Hence this must not qualify as pmd_bad(). > */ > - pmd_clear(pmdp); Ditto. > pmd_populate(mm, pmdp, pgtable); > pmd = READ_ONCE(*pmdp); > WARN_ON(pmd_bad(pmd)); >