From mboxrd@z Thu Jan 1 00:00:00 1970 From: Karel Zak Subject: Re: [BUG] remount ro on loopback mount leaves unmountable filesystem behind Date: Wed, 14 May 2008 00:55:58 +0200 Message-ID: <20080513225558.GU23843@nb.net.home> References: <20080513085047.GY155679365@sgi.com> <20080513102340.GA15112@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Chinner , lkml , linux-fsdevel , util-linux-ng@vger.kernel.org To: Christoph Hellwig Return-path: Received: from mx1.redhat.com ([66.187.233.31]:32974 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753296AbYEMW4H (ORCPT ); Tue, 13 May 2008 18:56:07 -0400 Content-Disposition: inline In-Reply-To: <20080513102340.GA15112@infradead.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, May 13, 2008 at 06:23:40AM -0400, Christoph Hellwig wrote: > On Tue, May 13, 2008 at 06:50:47PM +1000, David Chinner wrote: > > Same thing, but remounting the loop filesystem readonly > > before unmounting: > > > > $ mount -t xfs /dev/sdb6 /mnt/scratch > > $ mkdir /mnt/scratch/mnt > > $ touch /mnt/scratch/img > > $ mkfs.xfs -f -d file,name=/mnt/scratch/img,size=1g > > $ mount -t xfs -o loop /mnt/scratch/img /mnt/scratch/mnt > > $ mount -t xfs -o remount,ro /mnt/scratch/img /mnt/scratch/mnt > > $ umount /mnt/scratch/mnt > > $ umount /mnt/scratch > > umount: /mnt/scratch: device is busy > > umount: /mnt/scratch: device is busy > > This is a problem in mount, no the kernel. Before the remount the > /etc mtab looks something like this: > > /qemu/test.img /mnt xfs rw,loop=/dev/loop0 0 0 > > and after it looks something like this: > > /qemu/test.img /mnt xfs ro 0 0 Yes, that's mount(8) bug. It doesn't read old options from /etc/mtab when you remount by "mount -o remount ". > As a workaround do a losetup -d /dev/loop0 after unmounting the > filesystem. ... or use "mount -o remount ", for example: mount -t xfs -o remount,ro /mnt/scratch/mnt Karel -- Karel Zak