Re: can't recover ext4 on lvm from ext4_mb_generate_buddy:739: group1687, 32254 clusters in bitmap, 32258 in gd

From: Landry Minoza
Date: Thu Apr 12 2012 - 02:45:42 EST


On Thu, Jan 5, 2012 at 7:15 PM, Ted Ts'o <tytso@xxxxxxx> 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.)
>

If it can help, I add the exactly same behaviour: filesystem remounted
read-only with the same messages in dmesg and had to fsck it with a
3.1 kernel when I resized my ext4/lvm root fs.

I used kernel 3.3-rc6 from debian experimental amd64.
root fs remounted read-only with the same errors in dmesg after:
lvresize -L +5G /dev/mapper/perceval_vg1-root
resize2fs /dev/mapper/perceval_vg1-root

Rebooting on 3.3 or 3.2 kernel doesn't helped. Also tried to boot on
3.0 and 2.6.x from rescue CDs without success (fsck ok, mounting
without problem but fs remounted ro as soon as I boot on 3.2 or 3.3
kernel).
I had to install a 3.1 kernel boot on it to be able to finaly reboot on 3.3.

I use a single harddrive without any sort of raid and with one lvm pv
and one vg:
sudo fdisk -l /dev/sda

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xb0000000

Device Boot Start End Blocks Id System
/dev/sda1 63 273104 136521 de Dell Utility
/dev/sda2 205073105 205265884 96390 83 Linux
/dev/sda3 * 273105 205073104 102400000 7 HPFS/NTFS/exFAT
/dev/sda4 205265885 976773167 385753641+ 8e Linux LVM

Partition table entries are not in disk order

sudo pvs
PV VG Fmt Attr PSize PFree
/dev/sda4 perceval_vg1 lvm2 a-- 367,88g 187,35g

sudo vgs
VG #PV #LV #SN Attr VSize VFree
perceval_vg1 1 3 0 wz--n- 367,88g 187,35g

sudo lvs
LV VG Attr LSize Origin Snap% Move Log Copy% Convert
home perceval_vg1 -wi-ao 151,75g
root perceval_vg1 -wi-ao 24,97g
swap perceval_vg1 -wi-ao 3,82g


Can post other informations if it can help

--
Landry MINOZA
landry.minoza@xxxxxxxxx
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