NFSD: Update the NFSv2 READDIR argument decoder to use struct xdr_stream

As an additional clean up, move code not related to XDR decoding
into readdir's .pc_func call out.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfsxdr.c

@@ -381,15 +381,17 @@ nfssvc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p)
 int
 nfssvc_decode_readdirargs(struct svc_rqst *rqstp, __be32 *p)
 {
+	struct xdr_stream *xdr = &rqstp->rq_arg_stream;
 	struct nfsd_readdirargs *args = rqstp->rq_argp;
 
-	p = decode_fh(p, &args->fh);
-	if (!p)
+	if (!svcxdr_decode_fhandle(xdr, &args->fh))
+		return 0;
+	if (xdr_stream_decode_u32(xdr, &args->cookie) < 0)
+		return 0;
+	if (xdr_stream_decode_u32(xdr, &args->count) < 0)
 		return 0;
-	args->cookie = ntohl(*p++);
-	args->count  = ntohl(*p++);
 
-	return xdr_argsize_check(rqstp, p);
+	return 1;
 }
 
 /*