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 BB31AC433EF for ; Tue, 10 May 2022 01:27:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234179AbiEJBbi (ORCPT ); Mon, 9 May 2022 21:31:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55664 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234178AbiEJBbh (ORCPT ); Mon, 9 May 2022 21:31:37 -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 1C8F9154B0C; Mon, 9 May 2022 18:27:38 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R231e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=alimailimapcm10staff010182156082;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=32;SR=0;TI=SMTPD_---0VCo8GaE_1652146048; Received: from 30.15.214.13(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VCo8GaE_1652146048) by smtp.aliyun-inc.com(127.0.0.1); Tue, 10 May 2022 09:27:31 +0800 Message-ID: <86671cb8-51e7-0e8e-430a-a325887391b3@linux.alibaba.com> Date: Tue, 10 May 2022 09:28:08 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH 3/3] mm: rmap: Fix CONT-PTE/PMD size hugetlb issue when unmapping To: Peter Xu , Mike Kravetz Cc: Gerald Schaefer , akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org, tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org References: <20220429220214.4cfc5539@thinkpad> <20220502160232.589a6111@thinkpad> <48a05075-a323-e7f1-9e99-6c0d106eb2cb@linux.alibaba.com> <20220503120343.6264e126@thinkpad> <927dfbf4-c899-b88a-4d58-36a637d611f9@oracle.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On 5/10/2022 12:41 AM, Peter Xu wrote: > On Fri, May 06, 2022 at 12:07:13PM -0700, Mike Kravetz wrote: >> On 5/3/22 03:03, Gerald Schaefer wrote: >>> On Tue, 3 May 2022 10:19:46 +0800 >>> Baolin Wang wrote: >>>> On 5/2/2022 10:02 PM, Gerald Schaefer wrote: > > [...] > >>>> Please see previous code, we'll use the original pte value to check if >>>> it is uffd-wp armed, and if need to mark it dirty though the hugetlbfs >>>> is set noop_dirty_folio(). >>>> >>>> pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval); >>> >>> Uh, ok, that wouldn't work on s390, but we also don't have >>> CONFIG_PTE_MARKER_UFFD_WP / HAVE_ARCH_USERFAULTFD_WP set, so >>> I guess we will be fine (for now). >>> >>> Still, I find it a bit unsettling that pte_install_uffd_wp_if_needed() >>> would work on a potential hugetlb *pte, directly de-referencing it >>> instead of using huge_ptep_get(). >>> >>> The !pte_none(*pte) check at the beginning would be broken in the >>> hugetlb case for s390 (not sure about other archs, but I think s390 >>> might be the only exception strictly requiring huge_ptep_get() >>> for de-referencing hugetlb *pte pointers). > > We could have used is_vm_hugetlb_page(vma) within the helper so as to > properly use either generic pte or hugetlb version of pte fetching. We may > want to conditionally do set_[huge_]pte_at() too at the end. > > I could prepare a patch for that even if it's not really anything urgently > needed. I assume that won't need to block this patchset since we need the > pteval for pte_dirty() check anyway and uffd-wp definitely needs it too. OK. Thanks Peter.