From: Mikulas Patocka Subject: Re: [dm-devel] can't recover ext4 on lvm from ext4_mb_generate_buddy:739: group 1687, 32254 clusters in bitmap, 32258 in gd Date: Fri, 6 Jan 2012 11:40:17 -0500 (EST) Message-ID: References: <217150909.20120105113759@eikelenboom.it> <197607646.20120105142107@eikelenboom.it> <6FC155DD-80C1-4088-B745-6B74D9D5AA48@mit.edu> <4910694144.20120105171428@eikelenboom.it> <20120105181535.GB26382@thunk.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Sander Eikelenboom , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org To: device-mapper development Return-path: Received: from mx1.redhat.com ([209.132.183.28]:64694 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758757Ab2AFQk0 (ORCPT ); Fri, 6 Jan 2012 11:40:26 -0500 In-Reply-To: <20120105181535.GB26382@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, 5 Jan 2012, Ted Ts'o wrote: > On Thu, Jan 05, 2012 at 05:14:28PM +0100, Sander Eikelenboom wrote: > > > > OK spoke too soon, i have been able to trigger it again: > > - copying files from LV to the same LV without the snapshot went OK > > - copying from the RO snapshot of a LV to the same LV gave the error while copying the file again: > > OK. Originally, you said you did this: > > 1) fsck -v -p -f the filesystem > 2) mount the filesystem > 3) Try to copy a file > 4) filesystem will be mounted RO on error (see below) > 5) fsck again, journal will be recovered, no other errors > 6) start at 1) > > Was this with with a read-only snapshot always being in existence > through all of these five steps? When was the RO snapshot created? > > If a RO snapshot has to be there in order for this to happen, then > this is almost certainly a device-mapper regression. (dm-devel folks, The existence of a snapshot changes I/O completion times significantly, so it may be a race condition in ext4 that gets triggered which changed timings. Mikulas > this is a problem which apparently occurred when the user went from > v3.1.5 to v3.2, so this looks likes 3.2 regression.) > > - Ted