freebsd stable - Feb 2009 - zfs crashes with nfs and snapshots

Hi folks,

I just saw one of my FreeBSD servers (7.0-stable of June 2008) crash while
trying to access the .zfs snapshot directory via a nfs client machine.
The server got a page fault caused by the nfsd process. It wasn't even
able to dump the kernel image anymore.
Resetting the machine it first appeared to come back fine, but shortly
before the login prompt the nfsd let it crash hard again the same way as
before. Then I booted single user, fscked the ufs partitions by hand and
had to re-import the zpool with -f. After that I did another reboot,
whereupon everything was fine again.

As I need that machine I'm a bit unwilling to try accessing the snapshot
directory again via nfs right now. :-)
So here are some questions before I do anything else:
- Did anyone else already see this behaviour?
- Is there something wrong with accessing the snapshot directory via nfs?
- Does zfs stability profit from an update to a recent -stable?

Any answers or further thoughts/hints on this are very welcome.


cu
  Gerrit

On 2009-02-11, Gerrit K?hn wrote:
> I just saw one of my FreeBSD servers (7.0-stable of June 2008) crash while
> trying to access the .zfs snapshot directory via a nfs client machine.
This is likely the issue described in this message:

http://lists.freebsd.org/pipermail/freebsd-fs/2008-October/005217.html

The nfs fix has been committed to head and stable/7 (7.1-RELEASE has the
fix). The fix prevents system from panicing but you still can't access
the snapshot directory with readdirplus enabled nfs clients. As a
workaround you can disable readdirplus support if your nfs client allows
it.

-- 
Jaakko