From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from postfix.iai.uni-bonn.de ([131.220.8.4]:56910 "EHLO postfix.iai.uni-bonn.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753536AbaGQIAL (ORCPT ); Thu, 17 Jul 2014 04:00:11 -0400 Message-ID: <53C78212.2070204@informatik.uni-bonn.de> Date: Thu, 17 Jul 2014 09:58:10 +0200 From: Sebastian Ochmann MIME-Version: 1.0 To: Chris Murphy , zhe.zhang.research@gmail.com Cc: Btrfs BTRFS Subject: Re: Is it safe to mount subvolumes of already-mounted volumes (even with different options)? References: <53C6FA3D.9010803@informatik.uni-bonn.de> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Hello, I need to clarify, I'm _not_ sharing a drive between multiple computers at the _same_ time. It's a portable device which I use at different locations with different computers. I just wanted to give a rationale for mounting the whole drive to some mountpoint and then also part of that drive (a subvolume) to the respective computer's /home mountpoint. So it's controlled by the same kernel in the same computer, it's just that part of the filesystem is mounted at multiple mountpoints, much like a bind-mount, but I'm interested in mounting a subvolume of the already-mounted volume to some other mountpoint. Sorry for the confusion. Best regards Sebastian On 17.07.2014 01:18, Chris Murphy wrote: > > On Jul 16, 2014, at 4:18 PM, Sebastian Ochmann wrote: > >> Hello, >> >> I'm sharing a btrfs-formatted drive between multiple computers and each of the machines has a separate home directory on that drive. > > 2+ computers writing to the same block device? I don't see how this is safe. Seems possibly a bug that the 1st mount event isn't setting some metadata so that another kernel instance knows not to allow another mount. > > > Chris Murphy >