newer Linux nfs client freeze under load to OpenSolaris server

My Ubuntu 10.04 workstation automounts my OpenSolaris 2008.11 server. This works and is stable for "light use." If I hit it hard though with large "cp -a" reads or rsync/unison, then Linux locks up. The system is non-responsive, the activity light on my switch shows very active until I force the power off on the box. The activity light to NFS Server is calm during the Linux NFS Client activity.

I believe this happened when I ran Ubuntu 9.04. It does not happen on 2 other boxes: Ubuntu 8.04 and Gentoo ~2009. These other boxes are on the same switch 1Gb as the NFS Server, the problemed 10.04 workstation has 2 1Gb switches between.

I've tried nfs mount options vers=3 and udp and tcp, none seem to solve the problem.

I put another 100M switch between my 2 1Gb switches, this seems to work around the problem - no crashing.

Ideas? Seems harsh that Linux would freeze.
(I'll try with no switches next.)

Thanks for any ideas,
Scott

Does this bugzilla look relevant?

     https://bugzilla.kernel.org/show_bug.cgi?id=16056

If so, would you mind testing the patch that I posted for it?

Cheers
Trond