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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_RED autolearn=no 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 ECA79C433E6 for ; Thu, 7 Jan 2021 22:25:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD5DB235FF for ; Thu, 7 Jan 2021 22:25:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728486AbhAGWZf (ORCPT ); Thu, 7 Jan 2021 17:25:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46190 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728417AbhAGWZd (ORCPT ); Thu, 7 Jan 2021 17:25:33 -0500 Received: from mail-lf1-x12c.google.com (mail-lf1-x12c.google.com [IPv6:2a00:1450:4864:20::12c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 67BE0C0612F8 for ; Thu, 7 Jan 2021 14:25:18 -0800 (PST) Received: by mail-lf1-x12c.google.com with SMTP id o10so7442891lfl.13 for ; Thu, 07 Jan 2021 14:25:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=xVA8EX3Ya3VLCzTYD/3HJV6vu9wnB8Ksxcppehb8wkg=; b=aLBwEkrzH2dog7skXswOuCmN1wVRMYhtQrVhh0cQ18YIv5bYB9fwSP2jkbCjq16RT+ 7ZkrMMH8a+h9i/8LFGi5/v1m3OdFSKYDZaVpFHUGE7g/N7Bt360Bkv1ZfSzJUBd7uOu+ izF6/BGaqMIJpf7bImRHw95nrI9Iwi165eJuE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=xVA8EX3Ya3VLCzTYD/3HJV6vu9wnB8Ksxcppehb8wkg=; b=oqf/bHLIYXmo38jn2ryEVhW29L0O6CN28BzNFLyzZfyBwuMzcuxI5UT3q+hUwIgBuW gc6KX+ngsPSpXhgoJ6g06pCqu7WTX2VO7cP65lQD+5r4M63sdU83JGSfEjluPY2nVRnl buneVoOBF6MkXmXrNrJi+eMee2Nf7rrftq1YDm+GDc40nPBCRU/zIxLks9pn5SHKwd5L aqbVn4gngJ6d8UjJRxygB+JTWxBqqMXMDvwjFv+HfYVVT7Evq1S9mw8uI2w3vHNpWeQx AwRNaYDmssNf5kkmdXT9lIUX/iieV0jxsJCYe+DQ2ATqCgbCKcvKAGLMBz9TPol4kRQl SjWw== X-Gm-Message-State: AOAM530JATiOlIid9Z/7DEvNjBLbU+SJw7r+//YKJiJERJsplv6DnQBi 3HSMq52n2u7EbgJnvS0fd6CnKvMOLXjCsw== X-Google-Smtp-Source: ABdhPJxWynGQHaP/GRE8TbOBO/qxWaWiJOr653gLSZwC0iDzXb+4O6RCMUQKRy8ZYBPyWJ4Y4cTKHw== X-Received: by 2002:a19:5050:: with SMTP id z16mr358665lfj.48.1610058316638; Thu, 07 Jan 2021 14:25:16 -0800 (PST) Received: from mail-lf1-f41.google.com (mail-lf1-f41.google.com. [209.85.167.41]) by smtp.gmail.com with ESMTPSA id 84sm1442275lfd.131.2021.01.07.14.25.15 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Jan 2021 14:25:15 -0800 (PST) Received: by mail-lf1-f41.google.com with SMTP id s26so18309282lfc.8 for ; Thu, 07 Jan 2021 14:25:15 -0800 (PST) X-Received: by 2002:a19:7d85:: with SMTP id y127mr381008lfc.253.1610058315292; Thu, 07 Jan 2021 14:25:15 -0800 (PST) MIME-Version: 1.0 References: <20210107200402.31095-1-aarcange@redhat.com> <20210107200402.31095-3-aarcange@redhat.com> <4100a6f5-ab0b-f7e5-962f-ea1dbcb1e47e@nvidia.com> <394e17bc-8bed-4d17-5dba-9ab8052c8bea@nvidia.com> In-Reply-To: From: Linus Torvalds Date: Thu, 7 Jan 2021 14:24:59 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/2] mm: soft_dirty: userfaultfd: introduce wrprotect_tlb_flush_pending To: John Hubbard Cc: Andrea Arcangeli , Linux-MM , Linux Kernel Mailing List , Yu Zhao , Andy Lutomirski , Peter Xu , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , Minchan Kim , Will Deacon , Peter Zijlstra , Hugh Dickins , "Kirill A. Shutemov" , Matthew Wilcox , Oleg Nesterov , Jann Horn , Kees Cook , Leon Romanovsky , Jason Gunthorpe , Jan Kara , Kirill Tkhai Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 7, 2021 at 2:20 PM Linus Torvalds wrote: > > Hmm, add a check for the page being PageAnon(), perhaps? > > If it's a shared vma, then the page can be pinned shared with multiple > mappings, I agree. Or check the vma directly for whether it's a COW vma. That's probably a more obvious test, but would have to be done outside of page_maybe_dma_pinned(). For example, in copy_present_page(), we've already done that COW-vma test, so if we want to strengthen just _that_ test, then it would be sufficient to just add a /* This cannot be a pinned page if it has more than one mapping */ if (page_mappings(page) != 1) return 1; to copy_present_page() along with the existing page_maybe_dma_pinned() test. No? Linus