Ext4 external journal UUID mismatch?

Kevin Shanahan
2012-07-15T23:41:04Z

Hi,

I have created some filesystems with external journals, and after
reboot (clean shutdown) these will not mount anymore. I see in dmesg:

[42214.365496] EXT4-fs (dm-10): journal UUID does not match

However, the UUIDs look fine when viewed with dumpe2fs:

# dumpe2fs -h /dev/it8/nfs-kvmhost0
Filesystem volume name: <none>
Last mounted on: /srv/nfs4/kvmhost0-rootfs
Filesystem UUID: 8a543c99-8a66-4ec2-9664-e82e3642cee0
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: journal_data user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 983040
Block count: 3932160
Reserved block count: 196608
Free blocks: 3628551
Free inodes: 939811
First block: 0
Block size: 4096
Fragment size: 4096
Reserved GDT blocks: 959
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 8192
Inode blocks per group: 512
RAID stride: 128
RAID stripe width: 768
Flex block group size: 16
Filesystem created: Sun Jul 8 10:45:26 2012
Last mount time: Sun Jul 8 10:45:26 2012
Last write time: Sun Jul 15 20:47:20 2012
Mount count: 1
Maximum mount count: -1
Last checked: Sun Jul 8 10:45:26 2012
Check interval: 0 (<none>)
Lifetime writes: 2024 MB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal UUID: 9e21ab2e-533e-41b1-a006-21bcf7574a45
Journal device: 0xfd0c
Default directory hash: half_md4
Directory Hash Seed: 61c03a7c-947b-4432-a134-7b0dfd307228

# dumpe2fs -h /dev/ssdvg/jnl-kvmhost0
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 9e21ab2e-533e-41b1-a006-21bcf7574a45
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: journal_dev
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 0
Block count: 262144
Reserved block count: 0
Free blocks: 0
Free inodes: 0
First block: 0
Block size: 4096
Fragment size: 4096
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 0
Inode blocks per group: 0
Filesystem created: Sun Jul 8 10:45:20 2012
Last mount time: n/a
Last write time: Sun Jul 8 10:45:21 2012
Mount count: 0
Maximum mount count: -1
Last checked: Sun Jul 8 10:45:20 2012
Check interval: 0 (<none>)
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Default directory hash: half_md4
Directory Hash Seed: 9f3616f0-a8e2-4e61-8e31-2632a0fb2287

Journal block size: 4096
Journal length: 262144
Journal first block: 2
Journal sequence: 0x000120d6
Journal start: 0
Journal number of users: 1
Journal users: 8a543c99-8a66-4ec2-9664-e82e3642cee0

I don't understand why mount/kernel unhappy with this. Can someone
shed some light on this?

# uname -r
3.4.4-3-ARCH

Thanks,
Kevin.