Date:	Thu, 24 May 2012 18:54:17 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Sander Eikelenboom <linux@...elenboom.it>
Cc:	"Ted Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: dm corruption? (Was: Re: can't recover ext4 on lvm from
 ext4_mb_generate_buddy:739: group 1687, 32254 clusters in bitmap, 32258 in
 gd)

Hi,

On Thu, Jan 05, 2012 at 11:43:22PM +0100, Sander Eikelenboom wrote:
> Hello Ted,
> 
> Thursday, January 5, 2012, 7:15:35 PM, you 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,
> > 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
> 
> Tried to bisect, but every kernel in between seems to have some drivers for devices f*cked up so it doesn't even boot.
> That was a quite frustrating and disappointing experience.
> So it's back to 3.1.5 and continue with i was actually trying to do, and try later if it's still reproducible with another disk layout.
> 
> Thx for your effort so far.

Has anything else happened with this?

I'm seeing similar problems with dm_crypt (with kernel 3.2.7),
only I also see "JBD2: Spotted dirty metadata buffer",
which I've found some (unanswered) reference to here:
https://bugzilla.redhat.com/show_bug.cgi?format=multiple&id=822071

I can reproduce the problem 100% of the time, but only under the
early-boot conditions I see it in. I've failed at any attempt so far to
reproduce it once the system is all the way up. :(

My steps to reproduce are:

create 3G sparse file (making this zero-filled doesn't change anything)
loopback mount file
bring up dm-crypt on loopback
build ext4 on dm-crypt
copy about 100M worth of files into the filesystem

The amount of errors reported varies, but most recently:

[   82.659992] EXT4-fs error (device dm-1): ext4_mb_generate_buddy:739: group 14, 32258 clusters in bitmap, 32262 in gd
[   84.338432] EXT4-fs error (device dm-1): ext4_mb_generate_buddy:739: group 15, 32258 clusters in bitmap, 32262 in gd
[   86.334815] EXT4-fs error (device dm-1): ext4_mb_generate_buddy:739: group 16, 32258 clusters in bitmap, 32262 in gd
[   87.660183] JBD2: Spotted dirty metadata buffer (dev = dm-1, blocknr = 0). There's a risk of filesystem corruption in case of system crash.
[   87.814646] JBD2: Spotted dirty metadata buffer (dev = dm-1, blocknr = 0). There's a risk of filesystem corruption in case of system crash.
[   88.221369] EXT4-fs error (device dm-1): ext4_mb_generate_buddy:739: group 17, 32258 clusters in bitmap, 32262 in gd
[   89.930729] EXT4-fs error (device dm-1): ext4_mb_generate_buddy:739: group 18, 32258 clusters in bitmap, 32262 in gd
[   91.709804] EXT4-fs error (device dm-1): ext4_mb_generate_buddy:739: group 19, 32258 clusters in bitmap, 32262 in gd
[   93.805440] EXT4-fs error (device dm-1): ext4_mb_generate_buddy:739: group 20, 32258 clusters in bitmap, 32262 in gd

I'm at a loss for how to track this down. :(

Any ideas?

-Kees

> >> [ 2357.655783] EXT4-fs error (device dm-2): ext4_mb_generate_buddy:739: group 1861, 32254 clusters in bitmap, 32258 in gd
> >> [ 2357.656056] Aborting journal on device dm-2-8.
> >> [ 2357.718473] EXT4-fs (dm-2): Remounting filesystem read-only
> >> [ 2357.736680] EXT4-fs error (device dm-2) in ext4_da_write_end:2532: IO failure
> >> [ 2357.738328] EXT4-fs (dm-2): ext4_da_writepages: jbd2_start: 7615 pages, ino 4079617; err -30
> >> [ 2716.125010] EXT4-fs error (device dm-2): ext4_put_super:818: Couldn't clean up the journal
> >> 
> >> 
> >> Attached are 4x output from dumpe2fs
> >> - dumpe2fs-xen_images-3.2.0                           Made just after boot
> >> - dumpe2fs-xen_images-3.2.0-afterfsck                 Made after doing a fsck -v -p -f on the unmounted LV
> >> - dumpe2fs-xen_images-3.2.0-aftererror                Made after the error occured on the mounted LV
> >> - dumpe2fs-xen_images-3.2.0-aftererror-afterfsck      Made after the error occured, and after a subsequent fsck -v -p -f on the unmounted LV
> >> - dumpe2fs-xen_images-3.1.5                           Made after booting into 3.1.5 after all of the above
> >> 
> >> Oh yes also did a badblock scan to rule that out, and it seems the numbers stay the same.
> >> e2fsck 1.41.12 (17-May-2010) (from debian squeeze)
> >> 
> >> --
> >> Sander
> >> 
> >> 
> >> 
> >> >> 
> >> >> --
> >> >> Sander
> >> >> 
> >> >> 
> >> >> This is a forwarded message
> >> >> From: Sander Eikelenboom <linux@...elenboom.it>
> >> >> To: "Theodore Ts'o" <tytso@....edu>
> >> >> Date: Thursday, January 5, 2012, 11:37:59 AM
> >> >> Subject: can't recover ext4 on lvm from ext4_mb_generate_buddy:739: group 1687, 32254 clusters in bitmap, 32258 in gd
> >> >> 
> >> >> ===8<==============Original message text===============
> >> >> 
> >> >> I'm having some troubles with a ext4 filesystem on LVM, it seems bricked and fsck doesn't seem to find and correct the problem.
> >> >> 
> >> >> Steps:
> >> >> 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)
> >> >> 
> >> >> 
> >> >> I think the way i bricked it is:
> >> >> - make a lvm snapshot from that lvm logical disk
> >> >> - mount that lvm snapshot as RO
> >> >> - try to copy a file from that mounted RO snapshot to a diffrent dir on the lvm logical disk the snapshot is from.
> >> >> - it fails and i can't recover (see above)
> >> >> 
> >> >> 
> >> >> Is there a way to recover from this ?
> >> >> 
> >> >> 
> >> >> 
> >> >> [  220.748928] EXT4-fs error (device dm-2): ext4_mb_generate_buddy:739: group 1687, 32254 clusters in bitmap, 32258 in gd
> >> >> [  220.749415] Aborting journal on device dm-2-8.
> >> >> [  220.771633] EXT4-fs error (device dm-2): ext4_journal_start_sb:327: Detected aborted journal
> >> >> [  220.772593] EXT4-fs (dm-2): Remounting filesystem read-only
> >> >> [  220.792455] EXT4-fs (dm-2): Remounting filesystem read-only
> >> >> [  220.805118] EXT4-fs (dm-2): ext4_da_writepages: jbd2_start: 9680 pages, ino 4079617; err -30
> >> >> serveerstertje:/mnt/xen_images/domains/production# cd /
> >> >> serveerstertje:/# umount /mnt/xen_images/
> >> >> serveerstertje:/# fsck -f -v -p /dev/serveerstertje/xen_images
> >> >> fsck from util-linux-ng 2.17.2
> >> >> /dev/mapper/serveerstertje-xen_images: recovering journal
> >> >> 
> >> >>     277 inodes used (0.00%)
> >> >>       5 non-contiguous files (1.8%)
> >> >>       0 non-contiguous directories (0.0%)
> >> >>         # of inodes with ind/dind/tind blocks: 41/41/3
> >> >>         Extent depth histogram: 69/28/2
> >> >> 51890920 blocks used (79.18%)
> >> >>       0 bad blocks
> >> >>      41 large files
> >> >> 
> >> >>     199 regular files
> >> >>      53 directories
> >> >>       0 character device files
> >> >>       0 block device files
> >> >>       0 fifos
> >> >>       0 links
> >> >>      16 symbolic links (16 fast symbolic links)
> >> >>       0 sockets
> >> >> --------
> >> >>     268 files
> >> >> serveerstertje:/#
> >> >> 
> >> >> 
> >> >> 
> >> >> 
> >> >> System:
> >> >> - Kernel 3.2.0
> >> >> - Debian Squeeze with:
> >> >> ii  e2fslibs                              1.41.12-4stable1                     ext2/ext3/ext4 file system libraries
> >> >> ii  e2fsprogs                             1.41.12-4stable1                     ext2/ext3/ext4 file system utilities
> >> >> 
> >> >> ===8<===========End of original message text===========

-- 
Kees Cook                                            @outflux.net

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