From owner-freebsd-current@FreeBSD.ORG Sun Oct 11 23:38:27 2009 Return-Path: Delivered-To: freebsd-current@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 1AA0B106568B for ; Sun, 11 Oct 2009 23:38:27 +0000 (UTC) (envelope-from ehrmann@gmail.com) Received: from mxout-07.mxes.net (mxout-07.mxes.net [216.86.168.182]) by mx1.freebsd.org (Postfix) with ESMTP id E3A588FC23 for ; Sun, 11 Oct 2009 23:38:26 +0000 (UTC) Received: from [10.0.0.171] (unknown [64.9.236.71]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.mxes.net (Postfix) with ESMTPSA id 05A8622DD6D; Sun, 11 Oct 2009 19:38:24 -0400 (EDT) Message-ID: <4AD26C69.4040202@gmail.com> Date: Sun, 11 Oct 2009 16:38:17 -0700 From: David Ehrmann User-Agent: Thunderbird 2.0.0.23 (Windows/20090812) MIME-Version: 1.0 To: Gavin Atkinson References: <4AD0E286.9030508@gmail.com> <20091011133411.A80896@ury.york.ac.uk> In-Reply-To: <20091011133411.A80896@ury.york.ac.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: daichi@FreeBSD.org, freebsd-current@FreeBSD.org Subject: Re: Strange md/unionfs issue X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 11 Oct 2009 23:38:27 -0000 Gavin Atkinson wrote: > > On Sat, 10 Oct 2009, David Ehrmann wrote: > >> I have a system running on a flash disk. To prevent it from wearing >> out quickly, I don't run with a swap and mount /tmp and /var from >> memory. Because /var needs some directories and contains files I >> probably should save from time to time, I mount it from flash, mount >> /var to /var_real so I can access the underlying files, and then I >> mount an md device on top of /var as a unionfs. Initially, it seems >> to work, but seconds later, the unionfs seems to fail. > > When the mount "fails", is it still shown in the output of mount(1)? The output of mount is the same; it reports that a md-backed unionfs is on top of /var. > > It appears that this problem is the same as is reported in PR > kern/131441, which has so far not had any activity. It appears that > this bug has existed since at least 7.1-RELEASE. It does seem to be the same bug (or similar). With mine, I mounted a unionfs on top of a mount point that a nullfs was based on, not the nullfs's mount point. I think the bug in kern/131441 was with a unionfs over a nullfs. This probably means md's off the hook as the culprit, and the same thing would happen with ufs on /dev/foo.