umount -f <nfs> forces to panic

[Rick Macklem]

> From: "pluknet" <pluknet at gmail.com>
> To: "freebsd-stable" <freebsd-stable at freebsd.org>
> Sent: Friday, July 30, 2010 12:53:08 PM
> Subject: umount -f <nfs> forces to panic
> Hi.
> 
> This is 8.1 booted from NFS.
> I did installworld to NFS on idle system, then it started
> to print repeatedly "nfs server foo:mp lockd not responding".
> umount returned EBUSY, umount -f dropped to panic:
> 

I can't help w.r.t. fixing the lockd (NLM protocol). If you
don't need locking to work across multiple clients for a given
file, you can use the "nolockd" mount option. If you need
locking on a given file to work across multiple clients, then
you could consider trying NFSv4, which does have integrated
file locking in the protocol.

I am aware that "umount -f" crashes the system and hope to
have a working "hard forced umount" implemented for 8.2.

rick