From: Eric Sandeen Subject: Re: [PATCH] jbd2: don't write superblock when unmounting an ro filesystem Date: Wed, 15 Aug 2012 12:25:15 -0500 Message-ID: <502BDB7B.6030404@redhat.com> References: <500F1C28.8010800@redhat.com> <20120815121403.GA29223@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Eric Sandeen , ext4 development To: Jan Kara Return-path: Received: from mx1.redhat.com ([209.132.183.28]:55072 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755653Ab2HORZV (ORCPT ); Wed, 15 Aug 2012 13:25:21 -0400 In-Reply-To: <20120815121403.GA29223@quack.suse.cz> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 8/15/12 7:14 AM, Jan Kara wrote: > On Tue 24-07-12 17:05:28, Eric Sandeen wrote: >> This sequence: >> >> # truncate --size=65536 fsfile >> # losetup --offset 65536 /dev/loop0 fsfile >> # mkfs.ext4 /dev/loop0 >> # losetup -d /dev/loop0 >> # mount -o loop,ro,offset=65536 fsfile mnt/ >> # umount mnt >> # dmesg | tail >> >> results in an IO error when unmounting the RO filesystem: >> >> [ 312.386074] SELinux: initialized (dev loop1, type ext4), uses xattr >> [ 318.020828] Buffer I/O error on device loop1, logical block 196608 >> [ 318.027024] lost page write due to I/O error on loop1 >> [ 318.032088] JBD2: Error -5 detected when updating journal superblock for loop1-8. > Ted, did this patch fall through cracks? I've ported the fix to JBD and > added it to my tree. I plan to send it to Linus in a few days. Also I've > CC'd stable since this is a bit annoying regression. > > Honza Thanks for doing both of those things, Jan. BTW this happens on loop because mount -o,ro apparently sets up the loop device itself as readonly. -Eric