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=-1.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 9E0B8C43381 for ; Sun, 17 Feb 2019 20:40:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C3832173C for ; Sun, 17 Feb 2019 20:40:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550436025; bh=DSocnF1L6eyWNj3hPIODBxXx1gHkBTOmUqDASHhUTlI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=KDNuYf8WFkeYfUo1GAOMbE6F9o21vtO81AGDH6sDyzwwRRX1+JPMUTIVsB7sUQFI+ /HnIgH4h0eCfNCGcIHxmm/VUDr+iGzqr5/fvW7AXTw2uKeaKr6AQsG/P+Ci1OBNLnd xeEDWebIkiCdRQhe0k/UmqJrJElaEVu/7K4kduPA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726235AbfBQUkZ (ORCPT ); Sun, 17 Feb 2019 15:40:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:60108 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726015AbfBQUkY (ORCPT ); Sun, 17 Feb 2019 15:40:24 -0500 Received: from mail-wr1-f45.google.com (mail-wr1-f45.google.com [209.85.221.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1267D218B0 for ; Sun, 17 Feb 2019 20:40:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550436023; bh=DSocnF1L6eyWNj3hPIODBxXx1gHkBTOmUqDASHhUTlI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=LuJBlvNvd3qm+c8CSavQDSYtrCzMqVlzd++BRkdjsFhLyda7remWJV3gEJ6d2L2HJ bwJpDooZ5Xn20DBpEztsIXVRW51K1lYsCB6tixgYF5u3T0nV7BGh5pG1cFGwXfMjO9 k3cXzbEC7inGWMh6afmETu+M9EChLD66+qYHpPu4= Received: by mail-wr1-f45.google.com with SMTP id c8so16081610wrs.4 for ; Sun, 17 Feb 2019 12:40:22 -0800 (PST) X-Gm-Message-State: AHQUAuZZa8hU8o6+sQITrr2kbSGoslXgQhNxLTZs2um5mmpqPXnn/6F0 qPbE1vwSBjeMddYgWG0bP2l2jmpntD+d8cUOBo8LFg== X-Google-Smtp-Source: AHgI3Ibg57IFwXe//4IvXlOFrImVvDpNG51+kGQ0Cj4rjhUyaI6txLLa//dLfQr2ZKaR86QZMejnx7SDRhCnf/xAELI= X-Received: by 2002:adf:eb4c:: with SMTP id u12mr13616557wrn.199.1550436021371; Sun, 17 Feb 2019 12:40:21 -0800 (PST) MIME-Version: 1.0 References: <20190214220626.GV14116@dastard> <6a9dc05a-0445-d0ab-0140-1de4fee7ba9b@gmail.com> <20190217175450.psaesabv3vlzvjv4@angband.pl> In-Reply-To: <20190217175450.psaesabv3vlzvjv4@angband.pl> From: Andy Lutomirski Date: Sun, 17 Feb 2019 12:40:09 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 0/6] Allow setting file birth time with utimensat() To: Adam Borowski Cc: Boaz Harrosh , Dave Chinner , Omar Sandoval , Linux FS Devel , Al Viro , kernel-team , Linux API , Linux btrfs Developers List , Ext4 Developers List , linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Sun, Feb 17, 2019 at 9:55 AM Adam Borowski wrote: > > On Sun, Feb 17, 2019 at 06:35:25PM +0200, Boaz Harrosh wrote: > > On 15/02/19 00:06, Dave Chinner wrote: > > > So you're adding an interface that allows users to change the create > > > time of files without needing any privileges? > > > > Inode create time is forensic metadata in XFS - information we use > > > for sequence of event and inode lifetime analysis during examination > > > of broken filesystem images and systems that have been broken into. > > > I think the difference in opinion here is that there are two totally > > different BTIme out in the world. For two somewhat opposite motivations > > and it seems they both try to be crammed into the same on disk space. > > > > One - Author creation time > > Two - Local creation time > > > So it looks like both sides are correct trying to preserve their own guy? > > I'd say that [2] is too easily gameable to be worth the effort. You can > just change it on the disk. That right now it'd take some skill to find the > right place to edit doesn't matter -- a tool to update the btime against > your wishes would need to be written just once. Unlike btrfs, XFS doesn't > even have a chain of checksums all the way to the root. > > On the other hand, [1] has a lot of uses. It can also be preserved in > backups and version control (svnt and git-restore-mtime could be easily > extended). > > I'd thus go with [2] -- any uses for [1] are better delegated to filesystem > specific tools. > I started out in the Windows world, and I found it quite handy to right-click a file and see when it was created. When I started using Linux, I saw things like this: Access: 2019-02-16 22:19:32.024284060 -0800 Modify: 2016-02-02 19:26:47.901766778 -0800 Change: 2016-02-02 19:26:47.907766649 -0800 and my mind boggled a bit. Modify makes sense. Change? What's that? Why do I care? Adding "birth" makes sense, and I think that filesystem-agnostic backup tools *should* be able to write it. So I'm highly in favor of this patch. If XFS wants to disallow writing the birth time, fine, but I think that behavior should be overridable.