Bug#840070: cloud.debian.org: ext4 feature too new for jessie e2fsprogs

[Gerben Meijer <gerben@daybyday.nl>]

Package: cloud.debian.org
Severity: important

The ext4 filesystem for at least the libvirt box on Atlas is too new for
the version of e2fsprogs in jessie.

Trying to label the root partition results in:

tune2fs 1.42.12 (29-Aug-2014)
tune2fs: Filesystem has unsupported read-only feature(s) while trying to
open /dev/vda1
Couldn't find valid filesystem superblock.

Probable cause is an unsupported feature:

# dumpe2fs -h /dev/vda1 | grep -i feature
dumpe2fs 1.42.12 (29-Aug-2014)
Filesystem features:      has_journal ext_attr resize_inode dir_index
filetype needs_recovery extent 64bit flex_bg sparse_super large_file
huge_file dir_nlink extra_isize metadata_csum
Journal features:         journal_incompat_revoke journal_64bit
FEATURE_I4

FEATURE_I4 is "journal_checksum_v3" which is probably set by the hosts 
mkfs.ext4, but since the jessie e2fsprogs don't support it, it should 
not be set. It may even be the case that fsck will fail but I have not 
tested this.

To avoid this, "mkfs.ext4 -O ^metadata_csum" should suffice, until
e2fsprogs is at 1.43 or higher in jessie..