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 87F3CC433EF for ; Sat, 18 Dec 2021 10:07:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231472AbhLRKHD (ORCPT ); Sat, 18 Dec 2021 05:07:03 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:54847 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229847AbhLRKHC (ORCPT ); Sat, 18 Dec 2021 05:07:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1639822022; 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=XZ2/2GDqjwmlPCqWnOt2byTpaYB/3SglXvSt+1GORAs=; b=Jj4Lk7knnQRQTPvI0mCnORufeo3k+Y/hi937bg3o3YVZEK9sqKTkw9x+n0rzBRFGDP+H6V k26Y2nsJIawiaOBlD1J2a27H8ko4x6Ls7SbxaGA7FMSrGRRxP1XQhz9gwnlvqQEn1l69JL AUhaOumItp9o9+naF0izSRmA7x2IBhI= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-252-NBCsOCplPlS1oHjJY-T5CQ-1; Sat, 18 Dec 2021 05:07:00 -0500 X-MC-Unique: NBCsOCplPlS1oHjJY-T5CQ-1 Received: by mail-wm1-f72.google.com with SMTP id v190-20020a1cacc7000000b003456d598510so4236271wme.6 for ; Sat, 18 Dec 2021 02:07:00 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:organization:in-reply-to :content-transfer-encoding; bh=XZ2/2GDqjwmlPCqWnOt2byTpaYB/3SglXvSt+1GORAs=; b=qP/DdpehweHZTxFTGFyLbs07n6rZYg1ceW6kVuUlrDipcuTNh0SyI5AHVSGrgo2+6r tLCZ0waxLVmRxapWhbWhsZPLMtZKM5MJpcRG/7w8K3QzBtX2nTzXxkpheFARLwjbEzIB iORCOW19ik5uVLG9n2H0pRdGp3Bq5JnFHWuovR9+37ip+KmsbWWPxxvfFs3LvK4fOa2I VXs4anDWJed+TgY3LhZvON/YkMEpOYM23fQnfGnpuUsNrNwkrHv2T372t9b32BixPpYe O47kJzy0lEziEjg2aPkvguML5mTzM9ORD2K590bDosJ37UwSnFw0adUmSRdS5lqSD7+c 1Uhg== X-Gm-Message-State: AOAM532RD78sIUIzKCCdVxk4snX3KEi4gQ3yE/ULLLlUJUKlv03Ccfai G1aylheVS39CyJmVIEudvNfEUMjVimb1vFgZnxEX1GmVy5mcdoawBJjPyrdDoG6UhPL2VgOd8HJ eCLO5C34rD3muCdKIG+IPJqkIrtoF X-Received: by 2002:a5d:64e4:: with SMTP id g4mr5622447wri.510.1639822019719; Sat, 18 Dec 2021 02:06:59 -0800 (PST) X-Google-Smtp-Source: ABdhPJyE6IcrxlQD0ttKE3+QlbV92H6zyi5iah32fTwcoLS9Mg22cTAzNLO8d6jIQan1384A88Cdag== X-Received: by 2002:a5d:64e4:: with SMTP id g4mr5622424wri.510.1639822019520; Sat, 18 Dec 2021 02:06:59 -0800 (PST) Received: from [192.168.3.132] (p5b0c6703.dip0.t-ipconnect.de. [91.12.103.3]) by smtp.gmail.com with ESMTPSA id l2sm2726112wru.83.2021.12.18.02.06.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 18 Dec 2021 02:06:59 -0800 (PST) Message-ID: Date: Sat, 18 Dec 2021 11:06:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v1 06/11] mm: support GUP-triggered unsharing via FAULT_FLAG_UNSHARE (!hugetlb) Content-Language: en-US To: Linus Torvalds , Nadav Amit Cc: Jason Gunthorpe , Linux Kernel Mailing List , Andrew Morton , Hugh Dickins , David Rientjes , Shakeel Butt , John Hubbard , Mike Kravetz , Mike Rapoport , Yang Shi , "Kirill A . Shutemov" , Matthew Wilcox , Vlastimil Babka , Jann Horn , Michal Hocko , Rik van Riel , Roman Gushchin , Andrea Arcangeli , Peter Xu , Donald Dutile , Christoph Hellwig , Oleg Nesterov , Jan Kara , Linux-MM , "open list:KERNEL SELFTEST FRAMEWORK" , "open list:DOCUMENTATION" References: <20211217113049.23850-1-david@redhat.com> <20211217113049.23850-7-david@redhat.com> <54c492d7-ddcd-dcd0-7209-efb2847adf7c@redhat.com> <20211217204705.GF6385@nvidia.com> <2E28C79D-F79C-45BE-A16C-43678AD165E9@vmware.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 18.12.21 03:42, Linus Torvalds wrote: > On Fri, Dec 17, 2021 at 6:17 PM Linus Torvalds > wrote: >> >> I think the hugepage code should use the exact same logic that the >> regular wp fault code does. > > IOW, I think that this stupid (AND UNTESTED) patch should likely just > fix David's test-case with the hugepage and splice thing.. > > Or at least be somewhat close. But it should be paired with the GUP > side doing the right thing too, of course. Maybe it already does, > maybe it doesn't, I didn't check... > > And maybe there's something subtle about the page_count() of a THP > entry. Again, I can't really claim to have tested this all, but I'm > hoping this makes somebody go "Ahh, now I see what Linus means" Not the reaction you are hoping for: "Gah, Linus still doesn't see why the page_count is just wrong". :) See the mail I just wrote, let's get a common understanding of how our check should actually look like. -- Thanks, David / dhildenb