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=-2.5 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT 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 A4C9BC4360F for ; Fri, 15 Feb 2019 05:39:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6D50721927 for ; Fri, 15 Feb 2019 05:39:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20150623.gappssmtp.com header.i=@osandov-com.20150623.gappssmtp.com header.b="f52brf+h" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731511AbfBOFjw (ORCPT ); Fri, 15 Feb 2019 00:39:52 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:43408 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726336AbfBOFjw (ORCPT ); Fri, 15 Feb 2019 00:39:52 -0500 Received: by mail-pg1-f195.google.com with SMTP id v28so4249438pgk.10 for ; Thu, 14 Feb 2019 21:39:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=HaZj6WZq8bt12xjoYpuzuAGCzO6878f/AB6sJH+QDSQ=; b=f52brf+hmO17QSieL0bvnJyW4YwJrzb4BPFwsuNawt+4oW+vq5rVv0gnHmAbQMNQ+c mQ8pkd9zZYQz6JV6yJy/2YPhP3RTmH/VZii1Qtuy2GRqWVFJtsCdCqYDlEmeaDmurU6Z AS8fnWjRurg9KNFoV+UDUBHjDp2R9Tyo1Jp4fnJcdyj+dw8gjSc+aMFlgVtd10mBSDuk 3eHS0SO+7gxV/OQTP7Jbti1Qd7hsAOn1/g/Csj4UYmoH1lUtL83IkMOT84j6N6lowITG PkbBtSO0hjQalVT2lCh8+HLnhhFda4VsG1e43w2HB7q7jHwxIGSVNJbtYW5bxEVEdzBc OEVw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=HaZj6WZq8bt12xjoYpuzuAGCzO6878f/AB6sJH+QDSQ=; b=jPD16CVn6vDwI/cOtB/XStPpObumPxgMna65WdzKEmXKVt9ojwg+oYKQDs2Zlgw6c4 MrY+cxfW1T/4ePbLqHNPxcHsyQrKt0uCc6LasZgcu3i0S8adLoaOi9mUL+fFFWXhugXL SGQe1IPjGC5LH229Igv6UzFBOkuNyQckzVrtP/4MlGnWi5taVtrA48+h+0wqQ2sDf5U6 xR4i5YteOpzqiDCxv7wgUPtYelG7h8LUxX88/pQb8l0wHg9WEn4qpXGO3EwmLez1rJQG SRcIToYwbMDEuzWOOLANnEDFgpUFLZt1ZeH7AI1PN4BDtx17l1gWzivGUkHnV/1mz5xn GOhA== X-Gm-Message-State: AHQUAuadE1/siPqemXCUEgEWkZaFYK7xMmfILQus4YZ5eVIOVo4yvPyu veqq9qvLjxA81s8PQw3Hr3q89A== X-Google-Smtp-Source: AHgI3IbNmamUmr6xpmYEJn3AZ2qn54+j3cwXoNnI/U09nStWsyTnbCHvdL7oeZ4owrS16Nk+FRndNQ== X-Received: by 2002:a62:e519:: with SMTP id n25mr7987895pff.151.1550209191421; Thu, 14 Feb 2019 21:39:51 -0800 (PST) Received: from vader ([2601:602:8b00:55d3:e6a7:a0ff:fe0b:c9a8]) by smtp.gmail.com with ESMTPSA id o85sm8781046pfi.105.2019.02.14.21.39.50 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 14 Feb 2019 21:39:50 -0800 (PST) Date: Thu, 14 Feb 2019 21:39:50 -0800 From: Omar Sandoval To: Hans van Kranenburg Cc: "linux-fsdevel@vger.kernel.org" , Al Viro , "kernel-team@fb.com" , "linux-api@vger.kernel.org" , "linux-btrfs@vger.kernel.org" , "linux-ext4@vger.kernel.org" , "linux-f2fs-devel@lists.sourceforge.net" , "linux-xfs@vger.kernel.org" Subject: Re: [RFC PATCH 0/6] Allow setting file birth time with utimensat() Message-ID: <20190215053950.GF9819@vader> References: <1190dcc0-7054-72b4-2a88-33d0b97e332c@mendix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1190dcc0-7054-72b4-2a88-33d0b97e332c@mendix.com> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Feb 15, 2019 at 01:57:39AM +0000, Hans van Kranenburg wrote: > Hi, > > On 2/14/19 11:00 AM, Omar Sandoval wrote: > > From: Omar Sandoval > > > > Since statx was added in 4.11, userspace has had an interface for > > reading btime (file creation time), but no way to set it. This RFC patch > > series adds support for changing btime with utimensat(). Patch 1 adds > > the VFS infrastructure, patch 2 adds the support to utimensat() with a > > new flag, and the rest of the patches add filesystem support; I excluded > > CIFS for now because I don't have a CIFS setup to test it on. > > > > Updating btime is useful for at least a couple of use cases: > > > > - Backup/restore programs (my motivation for this feature is btrfs send) > > Can you give an example of such usefulness? What's the thing you run > into that you can't do without having this? That boils down to what's useful about having the file creation time, and it's really just another tidbit of information which you may or may not care about. Maybe you have a document that you've been editing for awhile, and you want to know when you started working on it. Or, you want to know when a user created some directory that they keep adding files to. If the file creation time is useful to you, then you likely want it preserved if you have to restore from backups. If I had to restore from backups yesterday and I'm trying to figure out when I started that document, I don't care that I restored that file yesterday, I want the real creation date. If you've never wondered when a file was created, then I'm sure you won't care whether btrfs send/receive preserves it :)