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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 BE6AEC433FE for ; Tue, 8 Dec 2020 23:41:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 83C0A23A7C for ; Tue, 8 Dec 2020 23:41:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731804AbgLHXlh (ORCPT ); Tue, 8 Dec 2020 18:41:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725906AbgLHXlg (ORCPT ); Tue, 8 Dec 2020 18:41:36 -0500 Received: from mail-ej1-x643.google.com (mail-ej1-x643.google.com [IPv6:2a00:1450:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 12695C0613D6 for ; Tue, 8 Dec 2020 15:40:56 -0800 (PST) Received: by mail-ej1-x643.google.com with SMTP id x16so330332ejj.7 for ; Tue, 08 Dec 2020 15:40:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=mFLKQRkZoww23XEL7PXOxhhtdWSbzprjYliTkriku9g=; b=Jntq7/6SNEMUM+eYiV7G1myyo+nAu2Zf/Ui7zyVN8Rx9JmZzQSKOZqkFrGDz2HKzIx ompHPIdlRCYp+RD+MWBTTOhJrYrPGgnm6FvSJkQ4hVoL2ssKEkAF+zV2AqkBpaqwQf1L 6KDbKsmFu0PuNmu0YProuT3VQdw7k2jl/7PzhJiGqIAcMDDBmL5Ec350EZ+jcnng1WDY q5SxN7JIbfpUCSkAeFvg3Azyk+kELpLE6khv6dGODjlbUnNFy9sd4viKNgatXVk3Gx3A cxLQrKvJMCMfZTJByzYEXAlFPEin3M8KQL9Jh520h+nPnlomi4pTcOhw0/Iu6YbmJMy4 OeIw== 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=mFLKQRkZoww23XEL7PXOxhhtdWSbzprjYliTkriku9g=; b=eAValDPpJ+X+nhdGa8/oM7a0nwqj8WPM/bVJb4ueyf5bY7cMiJklJoN4Kw2BbpZ5Pt HBrqdgUu/8PAavOJRRyo2yUpBlDH9XxSIMKlR8k9sCUaHNN3mgB93DI12J0hndQDTrAq ML9f/orPoYqcZA70tj3SwLSrVSDoxO70hgn3IWik1CUJGCmNhf7QgWOcW5SE+u3ty8ox HVa2aqg9ViTDpvI566Lwd4/VKsSn1kvwJlE/61CjEyJ4tLhIxlGmz4OLe6bPYDx5/y5Z UR6GP4seIT5aZbVCp38VQUz4q5RgMvGyPXiw6fCTIScwdGNAxKxxdHOKDjnJdvnF9pfO D/5g== X-Gm-Message-State: AOAM5319M3H0wiFfIvMDep2h5eQjfXChcYNn4fTdvkMvkEh94zS+ztXW akiFeqnbJpdQfzQI/Y9pdKbgPsupcyeOTo1QOszq7A== X-Google-Smtp-Source: ABdhPJwlgMQbj1gq6mP6kKfYjuwAl+ty/SxoFyiYcdC1W4w7ngUFi1kqfZfhHd3aFaQ+dqp4EipB37tPTiaBbuvqFIE= X-Received: by 2002:a17:906:518a:: with SMTP id y10mr77069ejk.323.1607470854865; Tue, 08 Dec 2020 15:40:54 -0800 (PST) MIME-Version: 1.0 References: <20201207225703.2033611-1-ira.weiny@intel.com> <20201207225703.2033611-3-ira.weiny@intel.com> <20201207232649.GD7338@casper.infradead.org> <20201207234008.GE7338@casper.infradead.org> <20201208213255.GO1563847@iweiny-DESK2.sc.intel.com> <20201208215028.GK7338@casper.infradead.org> <20201208223234.GL7338@casper.infradead.org> <20201208224555.GA605321@magnolia> In-Reply-To: <20201208224555.GA605321@magnolia> From: Dan Williams Date: Tue, 8 Dec 2020 15:40:52 -0800 Message-ID: Subject: Re: [PATCH V2 2/2] mm/highmem: Lift memcpy_[to|from]_page to core To: "Darrick J. Wong" Cc: Matthew Wilcox , Ira Weiny , Thomas Gleixner , Andrew Morton , Dave Hansen , Christoph Hellwig , Al Viro , Eric Biggers , Joonas Lahtinen , Linux Kernel Mailing List , linux-fsdevel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 8, 2020 at 2:49 PM Darrick J. Wong wrote: [..] > > So what's your preferred poison? > > > > 1. Corrupt random data in whatever's been mapped into the next page (which > > is what the helpers currently do) > > Please no. My assertion is that the kernel can't know it's corruption, it can only know that the driver is abusing the API. So over-copy and WARN seems better than violently regress by crashing what might have been working silently before.