NFSv3 currently returns the unsigned 64-bit cookie directly to
 userspace. The following patch causes the kernel to generate
 loff_t offsets for the benefit of userland.
 The current server-generated READDIR cookie is cached in the
 nfs_open_context instead of in filp->f_pos, so we still end up work
 correctly under directory insertions/deletion.
Signed-off-by: NOlivier Galibert <galibert@pobox.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>