sync-Regression in 2.6.28.2?

[Ralf Hildebrandt <Ralf.Hildebrandt@charite.de>]

I recently installed 2.6.28.2 on our postfix/dovecot-based
mailboxserver. Previously, 2.6.28 and 2.6.28.1 have been running there
without a hitch.

Now with 2.6.28.2 I had two major lockups: All writes to the users'
Maildirs (on ext4) would stall, the load would rise, "sync" would never
return.

I had to "reboot -f -n" to get the machine back. All hanging processes
were unkillable, even with kill -9.

There was NOTHING in dmesg, nothing in the log either. No indication
of filesystem errors or anything.

Lookin at the
http://www.eu.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.28.2
I see changes to 

fs: sys_sync fix
fs: sync_sb_inodes fix
fs: remove WB_SYNC_HOLD

Since the mailserver uses sync() extensively (both dovecot and
postfix), maybe that's the culprit?

Note: I'm really just guessing here!
Back to 2.6.28.1 for now.

-- 
Ralf Hildebrandt                                Ralf.Hildebrandt@charite.de
Charite - Universitätsmedizin Berlin            Tel.  +49 (0)30-450 570-155
Geschäftsbereich IT | Abt. Netzwerk             Fax.  +49 (0)30-450 570-962
Hindenburgdamm 30 | 12200 Berlin