Running something like:

mkdir -p /mnt/nfs
while true
do
    if mount server:/path /mnt/nfs
    then
        find /mnt/nfs &> /dev/null
        umount /mnt/nfs
    else
        break
    fi
done

causes xtab to fill with identical entries.  Rpc.mountd's memory usage
grows without bound.  I suspect that (though I should do some more
debugging to be sure) that mountd is allocating a structure and stamping an
entry into xtab but never de-allocating that structure when unmounted.  I
have no idea if its proper behavior to have xtab behave that way but its
really silly to me.

This happens with knfsd-1.4.7-7 and kernel-2.2.12-20 (SMP) as well as our
in-house 2.2.13 kernel RPM.