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=-18.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, 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 8FD2CC433F5 for ; Fri, 3 Sep 2021 07:07:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 41F2060FC0 for ; Fri, 3 Sep 2021 07:07:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 41F2060FC0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id D17E38D0002; Fri, 3 Sep 2021 03:07:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CC7D38D0001; Fri, 3 Sep 2021 03:07:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B8F598D0002; Fri, 3 Sep 2021 03:07:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0184.hostedemail.com [216.40.44.184]) by kanga.kvack.org (Postfix) with ESMTP id A50638D0001 for ; Fri, 3 Sep 2021 03:07:28 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 61A7E184D8F9E for ; Fri, 3 Sep 2021 07:07:28 +0000 (UTC) X-FDA: 78545381376.15.8B471A0 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf28.hostedemail.com (Postfix) with ESMTP id 10C71900009E for ; Fri, 3 Sep 2021 07:07:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630652847; 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=mZDuU7BAOLBhLJY4HPiW+0aRj9rBKIKaHcL++uG3Fy0=; b=UHENwNCnw6a6eVy4EcFXo8yCLPWvtk20sSCtkDd8rfsdtPgeDYWj6WbLRJZ11CeExRVXX4 USIBRW6tFtcQE1hn1K6IDfAkIl8X7ZHM8rKOWqgleVVPsgGvEgak3EyqCZ9RHMz4UmDlDw /QtrXkfDV9gR0464Bxk/4RLQKwubOvI= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-473-Jp4AKhL4P-q00E15t90Wzw-1; Fri, 03 Sep 2021 03:07:26 -0400 X-MC-Unique: Jp4AKhL4P-q00E15t90Wzw-1 Received: by mail-wr1-f69.google.com with SMTP id u2-20020adfdd42000000b001579f5d6779so1264391wrm.8 for ; Fri, 03 Sep 2021 00:07:25 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:organization :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=mZDuU7BAOLBhLJY4HPiW+0aRj9rBKIKaHcL++uG3Fy0=; b=GeYx6npG1xwL8FMtqJps498tsjWDGkMIpJPjhxLqJGXuaFMnoodzyYdBZ5rZJ6WkVC fdQ6Ttb5zynEgE7ZheOh3ajrTI46s9amL/ruMCvfVBlKQ5o5M8p5PUOkZ/NCHfnKpX11 9IM0PMDBrjtEViO5eBTIjjSkqLaUZcw9AT4B4kjWbQbVE2afh+OY+ZN17uzTL0Ur/UEG L/W/aWRVTo/Vh8NQD52GyGX8ZhrRe0xP+rdhtdmCTqSuqVxkddSoEV9P6FGkFFVPtQg1 AZ31Xd+TJ4A1OB98Ktl6qKbMBmHkBCm7PRNmemEHy7nnSnD1Ca051Mnp/I2KyqPMRuh0 B9XQ== X-Gm-Message-State: AOAM531JENQzv/Iac7hwhT36CQsLMb6eeoeyUPStRmWxJwN88rYDliO2 iY1yNErG3IxSgS1s/0pC5BxAZLJmpmedxvXUwIRAUnIrY/HvXoKD5PI6sLVhJWzJq6xU15me7d+ xxKq/HVN16Lg= X-Received: by 2002:a1c:f:: with SMTP id 15mr1799432wma.67.1630652844945; Fri, 03 Sep 2021 00:07:24 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwoBIf2qQq69J5mO2W3iddq5WUEfks7zCZdnJCrDBdBsVF0mOIsUfZqxsH9o1bzM4XnwJhf/g== X-Received: by 2002:a1c:f:: with SMTP id 15mr1799404wma.67.1630652844762; Fri, 03 Sep 2021 00:07:24 -0700 (PDT) Received: from [192.168.3.132] (p4ff23e05.dip0.t-ipconnect.de. [79.242.62.5]) by smtp.gmail.com with ESMTPSA id o7sm3384838wmc.46.2021.09.03.00.07.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 03 Sep 2021 00:07:24 -0700 (PDT) Subject: Re: [PATCH v2 4/5] mm: Add zap_skip_check_mapping() helper To: Alistair Popple , Peter Xu Cc: Hugh Dickins , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "Kirill A . Shutemov" , Jerome Glisse , Andrea Arcangeli , Miaohe Lin , Yang Shi , Matthew Wilcox , Mike Rapoport References: <20210902201721.52796-1-peterx@redhat.com> <1771631.QAr93JHi05@nvdebian> <2306207.EELmk4mpEQ@nvdebian> From: David Hildenbrand Organization: Red Hat Message-ID: <072aa3aa-e4f8-96f0-50b5-92707404926d@redhat.com> Date: Fri, 3 Sep 2021 09:07:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <2306207.EELmk4mpEQ@nvdebian> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=UHENwNCn; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf28.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 216.205.24.124) smtp.mailfrom=david@redhat.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 10C71900009E X-Stat-Signature: jwmamzjgyd7ccmdg16i3zmmmncb4zuhn X-HE-Tag: 1630652847-923905 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 03.09.21 03:50, Alistair Popple wrote: > On Friday, 3 September 2021 11:39:32 AM AEST Peter Xu wrote: >> On Fri, Sep 03, 2021 at 10:58:53AM +1000, Alistair Popple wrote: >>> On Friday, 3 September 2021 6:18:19 AM AEST Peter Xu wrote: >>>> Use the helper for the checks. Rename "check_mapping" into "zap_mapping" >>>> because "check_mapping" looks like a bool but in fact it stores the mapping >>>> itself. When it's set, we check the mapping (it must be non-NULL). When it's >>>> cleared we skip the check, which works like the old way. >>>> >>>> Move the duplicated comments to the helper too. >>>> >>>> Signed-off-by: Peter Xu >>>> --- >>>> include/linux/mm.h | 15 ++++++++++++++- >>>> mm/memory.c | 29 ++++++----------------------- >>>> 2 files changed, 20 insertions(+), 24 deletions(-) >>>> >>>> diff --git a/include/linux/mm.h b/include/linux/mm.h >>>> index 69259229f090..81e402a5fbc9 100644 >>>> --- a/include/linux/mm.h >>>> +++ b/include/linux/mm.h >>>> @@ -1720,10 +1720,23 @@ extern void user_shm_unlock(size_t, struct ucounts *); >>>> * Parameter block passed down to zap_pte_range in exceptional cases. >>>> */ >>>> struct zap_details { >>>> - struct address_space *check_mapping; /* Check page->mapping if set */ >>>> + struct address_space *zap_mapping; /* Check page->mapping if set */ >>>> struct page *single_page; /* Locked page to be unmapped */ >>>> }; >>>> >>>> +/* >>>> + * We set details->zap_mappings when we want to unmap shared but keep private >>>> + * pages. Return true if skip zapping this page, false otherwise. >>>> + */ >>>> +static inline bool >>>> +zap_skip_check_mapping(struct zap_details *details, struct page *page) >>>> +{ >>>> + if (!details || !page) >>>> + return false; >>>> + >>>> + return details->zap_mapping != page_rmapping(page); >>> >>> Shouldn't this check still be >>> details->zap_mapping && details->zap_mapping != page_rmapping(page)? >>> >>> Previously we wouldn't skip zapping pages if even_cows == true (ie. >>> details->check_mapping == NULL). With this change the check when >>> even_cows == true becomes NULL != page_rmapping(page). Doesn't this mean we >>> will now skip zapping any pages with a mapping when even_cows == true? >> >> Yes I think so. Thanks for pointing that out, Alistair, I'll fix in v3. >> >> But frankly I really think we should simply have that flag I used to introduce. >> It'll make everything much clearer. > > Yeah, I think a flag would also be fine. I still don't see the need for a flag quite frankly. Just factor out the checks we already have ... no change in behavior. -- Thanks, David / dhildenb