NFSv4 server running on RHEL 5.2 -- Server/Client Incompatibilities?

[Paarvai Naai]

Hi all,

This somewhat related to the post from Feb 2008:

http://linux-nfs.org/pipermail/nfsv4/2008-February/007697.html

Specifically, I am running an NFSv4 server on Centos 5.2 (kernel
2.6.18-92.1.6.el5).  I am then using FC8 as an NFSv4 client (kernel
2.6.25.6-27.fc8).  I am able to mount the server's NFSv4 export on the
client and access files with no perceived problems.

I am using the following krb5-based export:

/export        gss/krb5(rw,fsid=0,crossmnt,insecure,no_subtree_check,sync)

and the following mount parameters on the client:

nfs:/                   /mnt/nfs4               nfs4    noauto,sec=krb5 0 0

However, when I try to exercise file locking using the command "flock
-x filename echo" I get an "Input/Output Error" on the client.
Furthermore, I see the following error in my /var/log/messages on the
server:

kernel: NFSD: preprocess_seqid_op: bad seqid (expected 2, got 3)

I am suspecting I am simply out of luck here because I am using wildly
different versions of the kernel on the server and client machines.
Is this true?  This brings me to the question of how stable the
underlying protocol of NFSv4 is.  In other words should I still be
expecting these sorts of problems for a while or will things stabilize
as it has for NFSv3?

Lastly, the following pages seem to be a bit out-of-date.  Are there
new pages that list the current status/stability of the NFSv4 support
for Linux?

http://client.linux-nfs.org/priorities.html
http://www.citi.umich.edu/projects/nfsv4/linux/NFSv4_server_priorities.html

Thank you,
Paarvai