Weird Linux - FreeBSD/ZFS NFSv4 interoperability problem

[Rick Macklem]

> (Note: I originally posted this to freebsd-questions, and it was
> suggested I take it here.)
> 
> While doing some interoperability testing between Linux and FreeBSD, I
> came up with this unusual issue. I could use some help figuring out
> if this is a bug, and if so, where to file it. Here's the scenario:
> 
> - FreeBSD 8.1-RELEASE server, sharing a ZFS filesystem via NFSv4.
> - Linux client (I've tested with RHEL 5.4 and Debian Lenny) mounting
> said filesystem with NFSv4.
> - A user on the Linux client does a Subversion checkout onto the
> mounted filesystem.
> 
> At the end of the checkout, access to the filesystem hangs. nfsd on
> the FreeBSD server and rpciod on the Linux client seem to be in a
> tight loop, and there's lots of network traffic between them. I can
> reproduce this every time.
> 
> The problem does not occur if the backing filesystem is UFS instead of
> ZFS, if NFSv3 is used instead of NFSv4, or if the client is FreeBSD
> instead of Linux.
> 
If you email me a packet capture (probably only need a few seconds
when it is the tight loop), I can look at it in wireshark.
Something like "tcpdump -s 0 -w xxx host <client>" run on the server
should do it. Then email me "xxx" as an attachment.

However, I don't know diddly w.r.t. ZFS, so I don't know how much
I'll be able to help?

rick
ps: You either need the correct kernel modules or a kernel built
    with "options NFSD" to run the exp. server (which is the one
    that does NFSv4).