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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 A4D8CC433DB for ; Thu, 4 Feb 2021 17:56:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 442C864F43 for ; Thu, 4 Feb 2021 17:56:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237140AbhBDR4g (ORCPT ); Thu, 4 Feb 2021 12:56:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42194 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238675AbhBDR4R (ORCPT ); Thu, 4 Feb 2021 12:56:17 -0500 Received: from mail-lj1-x235.google.com (mail-lj1-x235.google.com [IPv6:2a00:1450:4864:20::235]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16A93C061788 for ; Thu, 4 Feb 2021 09:55:37 -0800 (PST) Received: by mail-lj1-x235.google.com with SMTP id c18so4453713ljd.9 for ; Thu, 04 Feb 2021 09:55:37 -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=voNiwPhzeLAZNHX2oRQL59Hxy42wWXI9DL6jmHv2mf0=; b=NUI9thqKSFpWLW3nPn6698yvI2J++NtLklBNQ+xHDuLU0hK9vHDTLtOsI88z5efBKG 8uCbzqHIDFL7NCjPcpmxpKuVrzdrJkALf3jaBFQky7nr8k1jo5+j5RhC3jzu3Fehs4lq k6G5sz9oPMVP3kBQajQ0ZaZP5M53dDdKmwQsU= 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=voNiwPhzeLAZNHX2oRQL59Hxy42wWXI9DL6jmHv2mf0=; b=cxwOn7Pwkm12ZVRVaGZINTjeQuKT6YjbMl2ViOj+7Aqj8CBd5HQ16AGDR+/UnFwmwS raFUMuDMouhqk/caBKr6qT+eydiuXv9L8jz6LS6mMvnbrmrtL12GLEk77c42LBSi1k5A 7FlllxoMq5y06XiocvrnaSPItr3tWGdlMqznFVdhe8WRc0M/2FejtwL67iOqdUdgN8On 3sutZN603WrQLrmRJavx72NmOls3vhkRSNKRFIK1XINSTzVGSXT3mAnPmM8ccZAdgbAn Lvi5e/NRAreavsoKReCnRHHcgHvqjV+OEerJcf280g0atsbNvFMbZLq71lbPtH/J8BWV Z+ZQ== X-Gm-Message-State: AOAM532SBfk+uirlTDdObtetEkSo2XYuFQyNkWyIOpzgWcMoDs6RmcZ4 LDZva8L8IHID0JSFhzSWJgYHOs8ebqhkfw== X-Google-Smtp-Source: ABdhPJygUNpsYU/NRJ4SGfuixwUQ99mNQeRWAjEhWVXkz2oGz+pumeC0kMgsBO24+fRkgIHSujw/xw== X-Received: by 2002:a2e:2ac4:: with SMTP id q187mr301709ljq.151.1612461335040; Thu, 04 Feb 2021 09:55:35 -0800 (PST) Received: from mail-lf1-f51.google.com (mail-lf1-f51.google.com. [209.85.167.51]) by smtp.gmail.com with ESMTPSA id x144sm694590lff.89.2021.02.04.09.55.33 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 04 Feb 2021 09:55:33 -0800 (PST) Received: by mail-lf1-f51.google.com with SMTP id i187so5863244lfd.4 for ; Thu, 04 Feb 2021 09:55:33 -0800 (PST) X-Received: by 2002:a19:8186:: with SMTP id c128mr273214lfd.377.1612461332734; Thu, 04 Feb 2021 09:55:32 -0800 (PST) MIME-Version: 1.0 References: <20210204145033.136755-1-peterx@redhat.com> <20210204145033.136755-4-peterx@redhat.com> In-Reply-To: <20210204145033.136755-4-peterx@redhat.com> From: Linus Torvalds Date: Thu, 4 Feb 2021 09:54:37 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 3/4] mm: Introduce page_needs_cow_for_dma() for deciding whether cow To: Peter Xu Cc: Linux-MM , Linux Kernel Mailing List , Kirill Shutemov , Wei Zhang , Mike Rapoport , Matthew Wilcox , Miaohe Lin , Andrea Arcangeli , Gal Pressman , Jan Kara , Jann Horn , Andrew Morton , Kirill Tkhai , Mike Kravetz , Jason Gunthorpe , David Gibson , Christoph Hellwig Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 4, 2021 at 6:50 AM Peter Xu wrote: > > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1291,6 +1291,27 @@ static inline bool page_maybe_dma_pinned(struct page *page) > GUP_PIN_COUNTING_BIAS; > } > > +static inline bool is_cow_mapping(vm_flags_t flags) > +{ > + return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; > +} Oh, and I just realized: moving this to means that this patch could/should also get rid of - manual copy of this in mm/hugetlb.c: cow = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; - private #define for the same thing in fs/proc/task_mmu.c #define is_cow_mapping(flags) (((flags) & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE) - manual copy in drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c: bool is_cow_mapping = (vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE; I guess it could be a later cleanup patch too, but maybe best done in this series just to not forget about it. Linus