pnfs: use lwb as layoutcommit length

Using NFS4_MAX_UINT64 will break current protocol.

[Needed in v3.0]
CC: Stable Tree <stable@kernel.org>
Signed-off-by: NPeng Tao <peng_tao@emc.com>
Signed-off-by: NJim Rees <rees@umich.edu>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4xdr.c

@@ -1916,7 +1916,7 @@ encode_layoutcommit(struct xdr_stream *xdr,
 	*p++ = cpu_to_be32(OP_LAYOUTCOMMIT);
 	/* Only whole file layouts */
 	p = xdr_encode_hyper(p, 0); /* offset */
-	p = xdr_encode_hyper(p, NFS4_MAX_UINT64); /* length */
+	p = xdr_encode_hyper(p, args->lastbytewritten + 1);	/* length */
 	*p++ = cpu_to_be32(0); /* reclaim */
 	p = xdr_encode_opaque_fixed(p, args->stateid.data, NFS4_STATEID_SIZE);
 	*p++ = cpu_to_be32(1); /* newoffset = TRUE */