I had some time and tracked this one down. It should be possible to export PFS's via NFS to linux now.
The bug was in the readdirplus rpc, which linux uses by default. Well, not really a bug, the NFS code simply did not supply enough information to HAMMER for HAMMER to be able to determine which PFS to lookup the inode number in. -- I also noticed that the d_ino field for directory entries returned by NFS was being truncated to 32 bits, and fixed that as well. -Matt