From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from resqmta-po-04v.sys.comcast.net ([96.114.154.163]:59327 "EHLO resqmta-po-04v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751160AbaJOTHI (ORCPT ); Wed, 15 Oct 2014 15:07:08 -0400 Message-ID: <543EC5DA.9040905@pobox.com> Date: Wed, 15 Oct 2014 12:07:06 -0700 From: Robert White MIME-Version: 1.0 To: linux-btrfs@vger.kernel.org Subject: Re: Wishlist Item :: One Subvol in Multiple Places References: <543DA2E3.3070503@pobox.com> <543E5AD2.6080207@gmail.com> In-Reply-To: <543E5AD2.6080207@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 10/15/2014 04:30 AM, Austin S Hemmelgarn wrote: > On 2014-10-14 18:25, Robert White wrote: >> I've got no idea if this is possible given the current storage layout, >> but it would be Really Nice™ if there were a way to have a single >> subvolume exist in more than one place in hirearchy. I know this can be >> faked via mount tricks (bind or use of subvol=), but having it be a real >> thing would be preferable. >> >> For example, if I have two or more distributions on a computer or want >> to switch between 32bit and 64bit environments frequently, but I want to >> use the same /home (which is its own subvolume anyway) it would be nice >> if the native layout could be permuted such that /__System_32/home and >> /__System_64/home were the actual same subvolume. >> >> The mechanism, were it possible, would be something like "btrfs >> subvolume link /existing/path /new/path" (or "bind" instead of "link") >> >> I've got no idea if the directory structure would allow for this, but if >> it would it would simplify several things (for me anyway) if the file >> system layout represented the runtime layout. > This probably won't be implemented, for the same reason that most modern > unix systems disallow hardlinks to directories; namely, it results in > ambiguity regarding resolution of the .. directory entry. > The better solution would be to put /home in a separate top-level > sub-volume, and then mount that in each location. Oh. Duh. I knew that... Some days the brain, you know... 8-) --Rob.