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SubjectRe: Apparent serious progressive ext4 data corruption bug in 3.6.3 (and other stable branches?)
On 10/23/12 3:57 PM, Nix wrote:

<snip>

> (I'd provide more sample errors, but this bug has been eating
> newly-written logs in /var all day, so not much has survived.)
>
> I rebooted into 3.6.1 rescue mode and fscked everything: lots of
> orphans, block group corruption and cross-linked files. The problems did
> not recur upon booting from 3.6.1 into 3.6.1 again. It is quite clear
> that metadata changes made in 3.6.3 are not making it to disk reliably,
> thus leading to corrupted filesystems marked clean on reboot into other
> kernels: pretty much every file appended to in 3.6.3 loses some or all
> of its appended data, and newly allocated blocks often end up
> cross-linked between multiple files.
>
> The curious thing is this doesn't affect every filesystem: for a while
> it affected only /var, and now it's affecting only /var and /home. The
> massive writes to the ext4 filesystem mounted on /usr/src seem to have
> gone off without incident: fsck reports no problems.
>
>
> The only unusual thing about the filesystems on this machine are that
> they have hardware RAID-5 (using the Areca driver), so I'm mounting with
> 'nobarrier':

I should have read more. :( More questions follow:

* Does the Areca have a battery backed write cache?
* Are you crashing or rebooting cleanly?
* Do you see log recovery messages in the logs for this filesystem?

> the full set of options for all my ext4 filesystems are:
>
> rw,nosuid,nodev,relatime,journal_checksum,journal_async_commit,nobarrier,quota,
> usrquota,grpquota,commit=30,stripe=16,data=ordered,usrquota,grpquota

ok journal_async_commit is off the reservation a bit; that's really not
tested, and Jan had serious reservations about its safety.

* Can you reproduce this w/o journal_async_commit?

-Eric

> If there's anything I can do to help, I'm happy to do it, once I've
> restored my home directory from backup :(
>
>
> tune2fs output for one of the afflicted filesystems (after fscking):
>
> tune2fs 1.42.2 (9-Apr-2012)
> Filesystem volume name: home
> Last mounted on: /home
> Filesystem UUID: 95bd22c2-253c-456f-8e36-b6cfb9ecd4ef
> Filesystem magic number: 0xEF53
> Filesystem revision #: 1 (dynamic)
> Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
> Filesystem flags: signed_directory_hash
> Default mount options: (none)
> Filesystem state: clean
> Errors behavior: Continue
> Filesystem OS type: Linux
> Inode count: 3276800
> Block count: 13107200
> Reserved block count: 655360
> Free blocks: 5134852
> Free inodes: 3174777
> First block: 0
> Block size: 4096
> Fragment size: 4096
> Reserved GDT blocks: 20
> Blocks per group: 32768
> Fragments per group: 32768
> Inodes per group: 8192
> Inode blocks per group: 512
> RAID stripe width: 16
> Flex block group size: 64
> Filesystem created: Tue May 26 21:29:41 2009
> Last mount time: Tue Oct 23 21:32:07 2012
> Last write time: Tue Oct 23 21:32:07 2012
> Mount count: 2
> Maximum mount count: 20
> Last checked: Tue Oct 23 21:22:16 2012
> Check interval: 15552000 (6 months)
> Next check after: Sun Apr 21 21:22:16 2013
> Lifetime writes: 1092 GB
> 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 inode: 8
> First orphan inode: 1572907
> Default directory hash: half_md4
> Directory Hash Seed: a201983d-d8a3-460b-93ca-eb7804b62c23
> Journal backup: inode blocks
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