[Samba] Samba-3.0.23c kernel lock problems with new Redhat kernel 2.6.9-42.0.8

[Ole Holm Nielsen]

We run samba-3.0.23c on some Redhat RHEL4 servers, and Samba used to work
like a charm.  But then a couple of days ago we upgraded the kernel
on the Samba servers to kernel-smp-2.6.9-42.0.8.EL.  All of a sudden
our Windows users could not use Microsoft Office with files on the
Samba shares :-(

Our filesystems are actually NFS-mounted by the Samba server from
another server, and the Samba server showed these log entries:

Feb  1 13:27:41 serv309 smbd[11728]: [2007/02/01 13:27:41, 0] 
locking/posix.c:posix_fcntl_lock(660)
Feb  1 13:27:41 serv309 smbd[11728]:   posix_fcntl_lock: WARNING: lock request 
at offset 2147483538, length 1 returned
Feb  1 13:27:41 serv309 smbd[11728]: [2007/02/01 13:27:41, 0] 
locking/posix.c:posix_fcntl_lock(661)
Feb  1 13:27:41 serv309 smbd[11728]:   an No locks available error. This can 
happen when using 64 bit lock offsets
Feb  1 13:27:41 serv309 smbd[11728]: [2007/02/01 13:27:41, 0] 
locking/posix.c:posix_fcntl_lock(662)
Feb  1 13:27:41 serv309 smbd[11728]:   on 32 bit NFS mounted file systems.
Feb  1 13:27:41 serv309 smbd[11728]: [2007/02/01 13:27:41, 0] 
locking/posix.c:posix_fcntl_lock(660)
Feb  1 13:27:41 serv309 kernel: lockd: cannot monitor 130.225.87.40
Feb  1 13:27:41 serv309 kernel: lockd: failed to monitor 130.225.87.40

With the previous kernel kernel-smp-2.6.9-42.0.3.EL there were no
such problems !  The Redhat kernel Release Notes
    https://rhn.redhat.com/errata/RHSA-2007-0014.html
do not mention any changes that seem to be related to Samba or NFS or locking.

Fortunately I found this article
    http://lists.samba.org/archive/samba/2006-October/126638.html
where Jeremy recommends to use "posix locking = no", and indeed
this fixes the problem !

Hopefully these observations can help others, but a real solution
to the problem would be most welcome !

-- 
Ole Holm Nielsen
Department of Physics, Technical University of Denmark