NFS client kernel issue?

[Keith Jackson]

Hi,
I've run into a strange problem, and I'm not sure where to ask about  
it. It appears to be kernel related, so hopefully someone here can  
shed some light on it for me. I have a over a dozen ubuntu 9 server  
machines that share an NFS filesystem served up on a FreeBSD machine.  
We recently upgraded the FreeBSD box to FreeBSD 7.2. The ubuntu  
machines are running the standard 2.6.28-11-server kernel.

At this point, we started having problems with NFS on all of the  
ubuntu machines. They would come up, mount the NFS shares and then  
5-10 minutes later NFS would be hung. I ran wireshark on one of them,  
while doing "ls -l ~username". When NFS was working everything looked  
fine. Once it hung, I would see the normal YP MATCH RPC call looking  
for the entry for "username". The NIS server would return the password  
entry for "username" as I'd expect. When things were working, I'd then  
see the standard NFS traffic. When NFS was hosed, the YP MATCH reply  
would be the last net traffic I would see to the NFS server. Nothing  
NFS related would ever happen. An strace would show that the ls was  
hung in a stat64 call.

A reboot of the system would cause things to start working for a  
while, but 5-10 minutes later NFS would hang. I eventually updated to   
a 2.6.30 kernel from: http://kernel.ubuntu.com/~kernel-ppa/mainline/v2.6.30/ 
  This has fixed the problem.

Any thoughts on what the problem might be, or how I might go about  
debugging it better?
thx,
--keith
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Keith R. Jackson                                     email: KRJackson at lbl.gov
MS: 50B-2239                                         phone: 510-486-4401
Lawrence Berkeley National Lab        url: http://www-itg.lbl.gov/~kjackson/
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