[linux-lvm] lvm2 2.02.105 breaks snapshots

[Christian Hesse]

Hello everybody,

looks like lvm2 2.02.105 breaks snapshots. This is my block device tree:

NAME                MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                   8:0    0   477G  0 disk
|-sda1                8:1    0   767M  0 part
| `-vg0-boot        254:0    0    64M  0 lvm   /boot
|-sda2                8:2    0 444,2G  0 part
| `-cvg             254:3    0 444,2G  0 crypt
|   |-cvg-root      254:4    0    40G  0 lvm   /
|   |-cvg-swap      254:5    0     4G  0 lvm   [SWAP]
|   |-cvg-log       254:6    0     1G  0 lvm   /var/log
|   `-cvg-home      254:8    0   320G  0 lvm   /home
|-sda3                8:3    0    32G  0 part
`-sda128            259:0    0     1M  0 part

Creating a snapshot succeeds, but it is broken and can not be mounted:

# lvcreate -s -pr -l50%free -n snap-home cvg/home
  Logical volume "snap-home" created
# mount /dev/cvg/snap-home /mnt/tmp 
mount: /dev/mapper/cvg-snap--home is write-protected, mounting read-only
mount: wrong fs type, bad option, bad superblock on
/dev/mapper/cvg-snap--home, missing codepage or helper program, or other error

Syslog has a lot of these messages:

[ 4823.002220] EXT4-fs (dm-7): ext4_check_descriptors: Checksum for group 256
failed (43470!=57954)

Downgrading to lvm2 2.02.104 fixes the problem:

# lvcreate -s -pr -l50%free -n snap-home
cvg/home Logical volume "snap-home" created
# mount /dev/cvg/snap-home /mnt/tmp
mount: /dev/mapper/cvg-snap--home is write-protected, mounting read-only

This is an Arch Linux system with Linux 3.12.8.
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