zfs upgrade hang upgrading from v3 to v5
Darren Pilgrim
list_freebsd at bluerosetech.com
Sat Jan 4 22:55:27 UTC 2014
I'm upgrading a system from 8.3 to 9.2 using a fresh install onto a
parallel set of filesystems on the ZFS pool. The system is a root on
ZFS configuration with GPT-labeled AHCI disks. The zpool upgrade step
worked fine. When I did `zfs upgrade -a` it didn't return right away,
but this system is a little smaller so I left it to work.
An hour later, it's still not done. Ctrl-T shows zfs upgrade is in
tx->tx_sync_done_cv and using no CPU. Normally I expect to see
"runnable" and using some CPU. I can still work in open SSH sessions,
but other zfs commands hang. New SSH logins don't work. Console logins
hang between me entering the username and it printing the password
prompt. Even though I know there are active processes on the system,
there is no disk activity. Networking is still fine--the machine acts
as a router, and the LAN behind it hasn't loss internet access. The
unbound instance running on it is also responsive, but it never touches
the disk when running (it syslogs).
Figuring it's livelocked on disk I/O, I try to reboot, but neither
Control-Alt-Delete nor the power button do anything. I ended up hard
resetting the system.
The system rebooted without issue. Zfs upgrade showed a few of the v3
filesystems had been upgraded, but most hadn't. Upgrading filesystems
one by one got me most of the way there. By dumb luck I got all the way
to the base filesystem without anything hanging. The base filesystem,
however, did hang.
I read Devin Teske's messages to freebsd-fs from Sept 20, 2013 about the
same scenario. Interestingly, the base filesystem on this box is the
only one that has mountpoint=none. Later today I'll try setting a
mountpoint on it see if the upgrade will succeed then.
In the meantime, is this a known issue by now? The only things I could
find were the aforementioned emails from Devin, and no one answered him.
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