knfsd: 64 bit ino support for NFS server

knfsd: 64 bit ino support for NFS server

Modify the NFS server code to support 64 bit ino's, as
appropriate for the system and the NFS protocol version.

The gist of the changes is to query the underlying file system
for attributes and not just to use the cached attributes in the
inode.  For this specific purpose, the inode only contains an
ino field which unsigned long, which is large enough on 64 bit
platforms, but is not large enough on 32 bit platforms.

I haven't been able to find any reason why ->getattr can't be called
while i_mutex.  The specification indicates that i_mutex is not
required to be held in order to invoke ->getattr, but it doesn't say
that i_mutex can't be held while invoking ->getattr.

I also haven't come to any conclusions regarding the value of
lease_get_mtime() and whether it should or should not be invoked
by fill_post_wcc() too.  I chose not to change this because I
thought that it was safer to leave well enough alone.  If we
decide to make a change, it can be done separately.

Signed-off-by: Peter Staubach <staubach@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Acked-by: Neil Brown <neilb@suse.de>