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 923A4C433F5 for ; Thu, 16 Dec 2021 08:04:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 188FC6B0073; Thu, 16 Dec 2021 03:04:35 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 139D36B0075; Thu, 16 Dec 2021 03:04:35 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0017B6B0078; Thu, 16 Dec 2021 03:04:34 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay027.a.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id E611E6B0073 for ; Thu, 16 Dec 2021 03:04:34 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id A8D03222B6 for ; Thu, 16 Dec 2021 08:04:24 +0000 (UTC) X-FDA: 78922920048.02.D862D7C Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf23.hostedemail.com (Postfix) with ESMTP id 03109140014 for ; Thu, 16 Dec 2021 08:04:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1639641863; 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: in-reply-to:in-reply-to:references:references; bh=Xwzuye7S0T3rwM3SGB9JNQpOpgQOfE/ay4CTJUX9JRc=; b=UgVDKbt8gELyQqvdjcuTm6sd+V7eClZdgw+y+FGJ9ZErv+PX4Im9zUUAZd2BfZ7fg6AX74 11bozxxPVh2qviwh7J4CeHChIIctcVNWVZKk1Ov4KBB+Tm+CqiAeaSZifMuCiTOa59K0qA c4zG453pl57/UMcn7YOxDPjrCKAdsyE= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-372-_JoQE5ywOi6pq8m49hni3A-1; Thu, 16 Dec 2021 03:04:19 -0500 X-MC-Unique: _JoQE5ywOi6pq8m49hni3A-1 Received: by mail-wm1-f70.google.com with SMTP id j25-20020a05600c1c1900b00332372c252dso9963709wms.1 for ; Thu, 16 Dec 2021 00:04:19 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=Xwzuye7S0T3rwM3SGB9JNQpOpgQOfE/ay4CTJUX9JRc=; b=nYua6PDVD3sZlSibczhMktwuTo4bJhCbAZ881uJ8Y//j3CaLuqwikj6wf4UNtuEvCd 4/1UeKShuvE9bjeOqVTBjcLZVYpPww+xL3/Tz72VMiVO5ZBPZkBwNb4QudjhcrVbGr4Y YTuzL4clC5GPxS8AL0MvmC9L/zIk+NFgYRIyqpQkcm7QKRLeLwMXYdbhNISuOIruVsSA lCoZVrEyL3VbgcuuojrLyTQ+GVd1kwCCwQPvpaUyhcw3LXkQpKPVZ/4gbMvd1Mphh5N2 l1wAAHTnlSOl75bHBD7kJjkhInpy67+/+QCpNiyd0gTPjSw//v5Zkq4I69yAYovWfC8T WNYA== X-Gm-Message-State: AOAM533CZP11/IqhnSOvLBaLJBQSry8TDG+5lEBEuCUyBNGlwWmzJ7Xa Gd1ZDdXus1wEZ5m8r1SkhawyGBEh6AcBP3ltRD/ihro2wLBAG0vHSu7SWZQ6Ja2Lrr7xOxMNQIJ nskE1lOXZlNI= X-Received: by 2002:a5d:4d91:: with SMTP id b17mr1634275wru.214.1639641858780; Thu, 16 Dec 2021 00:04:18 -0800 (PST) X-Google-Smtp-Source: ABdhPJzwCNul3EgDYz4gN3NPHyWlIp5E3OiCQeHtcX7O0+0vAVS6aKibqQ2Z2F3z248ifzQPcq8W4A== X-Received: by 2002:a5d:4d91:: with SMTP id b17mr1634255wru.214.1639641858525; Thu, 16 Dec 2021 00:04:18 -0800 (PST) Received: from xz-m1.local ([64.64.123.12]) by smtp.gmail.com with ESMTPSA id o5sm3912703wrx.83.2021.12.16.00.04.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Dec 2021 00:04:18 -0800 (PST) Date: Thu, 16 Dec 2021 16:04:09 +0800 From: Peter Xu To: Alistair Popple Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Axel Rasmussen , Nadav Amit , Mike Rapoport , Hugh Dickins , Mike Kravetz , "Kirill A . Shutemov" , Jerome Glisse , Matthew Wilcox , Andrew Morton , David Hildenbrand , Andrea Arcangeli Subject: Re: [PATCH v6 03/23] mm: Check against orig_pte for finish_fault() Message-ID: References: <20211115075522.73795-1-peterx@redhat.com> <1760244.MLhrlNdmRJ@nvdebian> <2472202.YjDCsHb11M@nvdebian> MIME-Version: 1.0 In-Reply-To: <2472202.YjDCsHb11M@nvdebian> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 03109140014 X-Stat-Signature: zyozxetm8wymweggae9itt77xsho7o1z Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=UgVDKbt8; spf=none (imf23.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-HE-Tag: 1639641859-771427 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 Thu, Dec 16, 2021 at 06:45:07PM +1100, Alistair Popple wrote: > On Thursday, 16 December 2021 6:06:54 PM AEDT Peter Xu wrote: > > [...] > > > I wondered how it could have worked - I thought e.g. pte_alloc_one() will > > always return a pgtable page will all zero-filled, whose allocation should > > require __GFP_ZERO anyway. But then I quickly noticed that pte_alloc_one() is > > per-arch too.. That explains, because per-arch can re-initialize the default > > pte values. > > Yes, I have wondered the same things before as well. It's all a little bit of > fun some of this stuff. > > > I thought this patch can greatly simplify things but I overlooked the > > pte_none() check you mentioned. So it seems I have no good choice but add that > > flag back. > > > > There's another alternative is we do pte_clear() on vmf->orig_pte as the new > > way to initialize it. I believe it should work too for s390 and xtensa. > > > > Any preference? > > I prefer the later approach (initialising to pte_clear) as it seems cleaner, > and pte_none(pte_clear()) is true for every architecture afaik. Will do. -- Peter Xu