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=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 CD3D9C56202 for ; Wed, 25 Nov 2020 15:52:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58380205CB for ; Wed, 25 Nov 2020 15:52:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IesDUyiG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730929AbgKYPwP (ORCPT ); Wed, 25 Nov 2020 10:52:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731840AbgKYPwO (ORCPT ); Wed, 25 Nov 2020 10:52:14 -0500 Received: from mail-il1-x144.google.com (mail-il1-x144.google.com [IPv6:2607:f8b0:4864:20::144]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9E3AC0613D4; Wed, 25 Nov 2020 07:52:14 -0800 (PST) Received: by mail-il1-x144.google.com with SMTP id b8so2519553ila.13; Wed, 25 Nov 2020 07:52:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=ZiuOyRTDnGxkNKDi3LqaWIg9/ryrtd/8rLTKFpwvXO4=; b=IesDUyiGY4msVm/mAJr9InhHvy9L/1ThEwro6HUd9Ie+vOE0aH4v3IdtgzAtlJWWJs nTz8Wo2vuTbVWEVD3rc0TR42uw8e+RaN7y9l8KZEq5wWAUw5zotJ5mc/9jMzW3FtnU0w keRwvS2eF13pAkXKA801K5VRidna2932JNbStPCHwhvcNLsZGpU+n1ytlbShK3wYYgKd adC2cDTXuKIsH+ruxwUO1Ce9KyYcHeVr2QPVr3T30cJZ3ZQZQFva934Ll7+6W4iZbWTH AmTlQrykwFQeXLC7auZuxSFYI4z5AFkzyhaQ3Be4pxEoXRRPqoFrS8WRfS+xkt6+shsy 7i8Q== 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=ZiuOyRTDnGxkNKDi3LqaWIg9/ryrtd/8rLTKFpwvXO4=; b=tMnHDAhxdBBJucUjWja7G3++46vkPrLzPrYZKFCJCoEVln6ve/pyEaHiKN65ayEnk6 hjRZe/ZIVyBoR0OmBQ22YCx4tGl7TPpqukRhDS639WlgVGuv70csuxa2nOJ++yqHiqgg Ewmdi4d0ryhqbU3H5MQgJgrSRbi3BQ5sMUXsiRNKNd+T/nGeeTINnidk0It1v3z0QRXr R75QZJ+d0bqdsN0FRN6whPRfi8MxgcQ7dJs/RS9SsSgPUW9OreOjySBppdpYQmZas5eY NUGNVns3SGnVwZnwQMeLai5S1jZGdrDK8vt2dXc5H5/R0v79NN2P/g6FmEAOx1bMbeO+ 6/KQ== X-Gm-Message-State: AOAM531Hi+FMYuukwrVhlxKkZg3RPttt+eaNl4ECm1tMdg1T4zP6bgO5 My/2kIFVE9DQykIHVmT1NlMo5gwyAN1DO14GhK4= X-Google-Smtp-Source: ABdhPJxKs2Tv4YSW6vzK6SbD5qLPK93Gu3lEP9RW3v5hB3XqDFoGiKyzo6jQyoaEp8tZGIXM9J1K2vulYO98UQmPers= X-Received: by 2002:a92:6403:: with SMTP id y3mr3827782ilb.72.1606319534010; Wed, 25 Nov 2020 07:52:14 -0800 (PST) MIME-Version: 1.0 References: <20201125104621.18838-1-sargun@sargun.me> <20201125104621.18838-4-sargun@sargun.me> <20201125153646.GC3095@redhat.com> In-Reply-To: <20201125153646.GC3095@redhat.com> From: Amir Goldstein Date: Wed, 25 Nov 2020 17:52:03 +0200 Message-ID: Subject: Re: [PATCH v1 3/3] overlay: Add rudimentary checking of writeback errseq on volatile remount To: Vivek Goyal Cc: Sargun Dhillon , overlayfs , Miklos Szeredi , Alexander Viro , Giuseppe Scrivano , Daniel J Walsh , linux-fsdevel , David Howells Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org On Wed, Nov 25, 2020 at 5:36 PM Vivek Goyal wrote: > > On Wed, Nov 25, 2020 at 04:03:06PM +0200, Amir Goldstein wrote: > > On Wed, Nov 25, 2020 at 12:46 PM Sargun Dhillon wrote: > > > > > > Volatile remounts validate the following at the moment: > > > * Has the module been reloaded / the system rebooted > > > * Has the workdir been remounted > > > > > > This adds a new check for errors detected via the superblock's > > > errseq_t. At mount time, the errseq_t is snapshotted to disk, > > > and upon remount it's re-verified. This allows for kernel-level > > > detection of errors without forcing userspace to perform a > > > sync and allows for the hidden detection of writeback errors. > > > > > > > Looks fine as long as you verify that the reuse is also volatile. > > > > Care to also add the alleged issues that Vivek pointed out with existing > > volatile mount to the documentation? (unless Vivek intends to do fix those) > > I thought current writeback error issue with volatile mounts needs to > be fixed with shutting down filesystem. (And mere documentation is not > enough). > Documentation is the bare minimum. If someone implements the shutdown approach that would be best. > Amir, are you planning to improve your ovl-shutdown patches to detect > writeback errors for volatile mounts. Or you want somebody else to > look at it. I did not intend to work on this. Whoever wants to pick this up doesn't need to actually implement the shutdown ioctl, may implement only an "internal shutdown" on error. > > W.r.t this patch set, I still think that first we should have patches > to shutdown filesystem on writeback errors (for volatile mount), and > then detecting writeback errors on remount makes more sense. > I agree that would be very nice, but I can also understand the argument that volatile mount has an issue, which does not get any better or any worse as a result of Sargun's patches. If anything, they improve the situation: Currently, the user does have a way to know if any data was lost on a volatile mount. After a successful mount cycle, the user knows that no data was lost during the last volatile mount period. Thanks, Amir.