Re: can't recover ext4 on lvm from ext4_mb_generate_buddy:739: group 1687, 32254 clusters in bitmap, 32258 in gd

["Ted Ts'o" <tytso@mit.edu>]

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


> 
> [ 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@eikelenboom.it>
> >> To: "Theodore Ts'o" <tytso@mit.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===========
> >> 
> >> 
> >> 
> >> -- 
> >> Best regards,
> >> Sander                            mailto:linux@eikelenboom.it<Message01.eml>
> 
> 
> 
> 
> -- 
> Best regards,
>  Sander                            mailto:linux@eikelenboom.it