[Bug 1637779] Re: ext4 filesystem fails randomly with checksum error

[Theodore Ts'o]

The errors simply mean that ext4 has detected that its metadata has
gotten corrupted.  How and why it happened is going to vary from
situation to situation.

For example, in the case of the original reporter, it was due to him
installing ext2fsd, and trying to access the file system from windows.
The ext2fsd isn't aware of all of the latest new features in ext4, and
worse, it didn't know to check the file system feature bitmaps, and if
there is a feature set in the read-only incompat feature set or the
incompat feature set which ext2fsd didn't understand, that it should
keep its paws off the file system.   This caused the checksum failures.

In Gerard's case in #8 and #9, it's not clear what the cause might be.
Ubuntu 14.04 doesn't ship with e2fsprogs 1.43.  So you've updated to a
newer version of e2fsprogs; one which is newer than what is supported
with Ubuntu 14.04.  It's possible that this was due to your using a much
older kernel than one that was truly ready to support the metadata
checksum feature; so if you are using the ancient Ubuntu 14.04 kernel,
that might be the explanation.  Or it could be that there is a true
hardware problem that you are tripping up against.  In any case, this
isn't an e2fsprogs bug.  It's possible it's a kernel bug, but neither
Ubuntu nor the upstream kernel community is going to support the ext4
metadata checksum feature on an ancient Ubuntu 14.04 kernel.

If you think your are technically saavy enough to run with an upstream
kernel, you could update to a bleeding edge kernel, and then you can ask
about ext4 problems on the linux-ext4 mailing list.  If you don't think
you're ready to go that extreme, it might be for the best if you were to
just disable the metadata_csum feature, using "tune2fs -O ^metadata_csum
/dev/sdb5" with the file system umounted.   You can then disable mke2fs
from enabling the metadata_csum feature in the future by editing
/etc/mke2fs.conf, and removing metadata_csum from the features list.

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https://bugs.launchpad.net/bugs/1637779

Title:
  ext4 filesystem fails randomly with checksum error

Status in e2fsprogs package in Ubuntu:
  Confirmed

Bug description:
  Description:	Ubuntu 16.10
  Release:	16.10

  package version:
  linux-image-4.8.0-26-generic:
    Installed: 4.8.0-26.28
    Candidate: 4.8.0-26.28
    Version table:
   *** 4.8.0-26.28 500
          500 http://sk.archive.ubuntu.com/ubuntu yakkety-updates/main amd64 Packages
          500 http://security.ubuntu.com/ubuntu yakkety-security/main amd64 Packages
          100 /var/lib/dpkg/status

  
  fresh installation of Ubunut 16.10, all updates included

  While I am working with system after few minutes root filesystem /dev/sdb5 switches into readonly mode
  in dmesg is this:

  [  304.921552] EXT4-fs error (device sdb5): ext4_iget:4476: inode #24577: comm updatedb.mlocat: checksum invalid
  [  304.925565] Aborting journal on device sdb5-8.
  [  304.926507] EXT4-fs (sdb5): Remounting filesystem read-only
  [  304.927416] EXT4-fs error (device sdb5): ext4_journal_check_start:56: Detected aborted journal
  [  304.943408] EXT4-fs error (device sda1): ext4_iget:4476: inode #12: comm updatedb.mlocat: checksum invalid

  when it happens I must do fsck f /dev/sdb1 once, second time it says
  everything is fine. after reboot when I start dto do something it soon
  happens again

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