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, USER_AGENT_MUTT 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 81D64C43381 for ; Fri, 15 Feb 2019 05:39:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F6BD21927 for ; Fri, 15 Feb 2019 05:39:56 +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 S1731543AbfBOFjy (ORCPT ); Fri, 15 Feb 2019 00:39:54 -0500 Received: from mail-pg1-f194.google.com ([209.85.215.194]:40688 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731485AbfBOFjw (ORCPT ); Fri, 15 Feb 2019 00:39:52 -0500 Received: by mail-pg1-f194.google.com with SMTP id u9so731276pgo.7 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=sVfrN8A9zPXFtVc4nrpkat2I66dnAC4/wVgLTKCOjxv+Rl2jCmjyn8/dmYNyuCCJjB Is1TxEu2ZptNk08VNTqimYjCrX7mtwXlKBennvM1e2V3vuSxZhAHIlSYYJl+MSNFmYlq 0jAqguZV7wnQjfmYnd0ztGc1Ed4EwR+w9wUDba08FMZe1tg6UdWf59Io4o1GBrf0JMco kVtKwuAFyl3q0H7Sn9V4KbBndIDHo2Evpjy+AvYsj1RzsEmi89L1RzbPwPZA4kxqHbXB j60RcCsbD783EVddgBXCSBfWjD/QMI0eOKhRkOiha+AjnS5SK/RNeiqXSFnzW0LaJE1+ zb4w== X-Gm-Message-State: AHQUAuYkEczKvaSi4eFWJ/3JDbPdWYmld9KeA/tzgsaR9SduBEXDYJPp 9xXCnkthVOey1ZJNuTbBb3Q47Q== 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-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@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 :)