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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 AF356C433E6 for ; Tue, 19 Jan 2021 18:31:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7444E230FE for ; Tue, 19 Jan 2021 18:31:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387558AbhASSbU (ORCPT ); Tue, 19 Jan 2021 13:31:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48436 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387620AbhASSbC (ORCPT ); Tue, 19 Jan 2021 13:31:02 -0500 Received: from mail-qv1-xf35.google.com (mail-qv1-xf35.google.com [IPv6:2607:f8b0:4864:20::f35]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 54069C0613D3 for ; Tue, 19 Jan 2021 10:30:15 -0800 (PST) Received: by mail-qv1-xf35.google.com with SMTP id bd6so9609058qvb.9 for ; Tue, 19 Jan 2021 10:30:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=k26IIVGt0E6B0tvAWOLHZwdfWuzN6d7qHFvd8ZVNYk0=; b=SUDvSIigSqo9rIUtIa5Eu7WRTj6rJFVObJR6As14fn+j77cYLuyyxMrcYQn4LJ7oG7 c+B4J2r9aBh7C2LK9Ij3Rwg3xcoBksq1T/LmdXvtLr00KreJld2kCA0eD9SMgWcetyIG dN1f9MePpQ76i5U7QninrJfI6nDXmt78D4XVs8g1ze5Sg/QMQiFUS9DYfXAwUlRF8mqn 6cB8q+OXHzS5MK0gRo4uPohwvfUbo7BxlINAn4ZCTyFG0Tjjo977o6dQzaAww+qmiotF Ybr9L5jpCctVi2x5b//4Cv/tMqGPxAeaLRqM/yCPr1TjJknCu6hQDBScR/SeH0Y4SDJu VkJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=k26IIVGt0E6B0tvAWOLHZwdfWuzN6d7qHFvd8ZVNYk0=; b=iiIELOrb+V4rPejbVQZ9N9nFesymlAGuOfTrfB8f51OrIjat/bIpOTfjP09coxlQ6T /p3ASUgVOGJQkPWR8iEBQK5cnCFumKD65WqhgMJxnXSRHiKhCXynv9Dwpyr4AhZ+uPbS qm2A2sUbE6beKTSi6I5LZ0p/g/hfgUAEpF/esruOtWz3SCQeUCN5fZbGpIJDlXmXpUxc hPa2C/CNSYS9vYOM1svgQbTN6C1rKe1/MU99g7a0BQmDDIonvIQzcFmTIu7s7z3FLH0p NJEY68LgHBeUesPYRSiRzGfZ+Ei7UOsYreeygX7CoHsNnsci0lG6blyIez9TXyxYkGZ6 DfAw== X-Gm-Message-State: AOAM532QPlx6Jjk4ci7ZSz8OXxDQ78I3KXCOCWFCVH75MvNplDcAmP7O 5bjalt48QrohSC7xq/c1tdEuEg== X-Google-Smtp-Source: ABdhPJyVPdLzW30F86jbhbw02UhyEzNHNm1A2a7XQsfcX2SJOI44r3mS/eSEiOOFPJWqKfCPcbsZUA== X-Received: by 2002:a0c:f005:: with SMTP id z5mr5528978qvk.9.1611081014621; Tue, 19 Jan 2021 10:30:14 -0800 (PST) Received: from ziepe.ca (hlfxns017vw-142-162-115-133.dhcp-dynamic.fibreop.ns.bellaliant.net. [142.162.115.133]) by smtp.gmail.com with ESMTPSA id 128sm13451661qki.26.2021.01.19.10.30.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jan 2021 10:30:14 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1l1vld-003pg1-Ed; Tue, 19 Jan 2021 14:30:13 -0400 Date: Tue, 19 Jan 2021 14:30:13 -0400 From: Jason Gunthorpe To: Pavel Tatashin Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, vbabka@suse.cz, mhocko@suse.com, david@redhat.com, osalvador@suse.de, dan.j.williams@intel.com, sashal@kernel.org, tyhicks@linux.microsoft.com, iamjoonsoo.kim@lge.com, mike.kravetz@oracle.com, rostedt@goodmis.org, mingo@redhat.com, peterz@infradead.org, mgorman@suse.de, willy@infradead.org, rientjes@google.com, jhubbard@nvidia.com, linux-doc@vger.kernel.org, ira.weiny@intel.com, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v5 08/14] mm/gup: do not allow zero page for pinned pages Message-ID: <20210119183013.GB4605@ziepe.ca> References: <20210119043920.155044-1-pasha.tatashin@soleen.com> <20210119043920.155044-9-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210119043920.155044-9-pasha.tatashin@soleen.com> Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Mon, Jan 18, 2021 at 11:39:14PM -0500, Pavel Tatashin wrote: > Zero page should not be used for long term pinned pages. Once pages > are pinned their physical addresses cannot changed until they are unpinned. > > Guarantee to always return real pages when they are pinned by adding > FOLL_WRITE. > > Signed-off-by: Pavel Tatashin > --- > mm/gup.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) No, this will definitely break things Why does the zero page have to be movable? Jason