NFSv4: Replace callback string decode function with a generic

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/callback_xdr.c

@@ -83,23 +83,15 @@ static __be32 *read_buf(struct xdr_stream *xdr, size_t nbytes)
 	return p;
 }
 
-static __be32 decode_string(struct xdr_stream *xdr, unsigned int *len, const char **str)
+static __be32 decode_string(struct xdr_stream *xdr, unsigned int *len,
+		const char **str, size_t maxlen)
 {
-	__be32 *p;
-
-	p = read_buf(xdr, 4);
-	if (unlikely(p == NULL))
-		return htonl(NFS4ERR_RESOURCE);
-	*len = ntohl(*p);
-
-	if (*len != 0) {
-		p = read_buf(xdr, *len);
-		if (unlikely(p == NULL))
-			return htonl(NFS4ERR_RESOURCE);
-		*str = (const char *)p;
-	} else
-		*str = NULL;
+	ssize_t err;
 
+	err = xdr_stream_decode_opaque_inline(xdr, (void **)str, maxlen);
+	if (err < 0)
+		return cpu_to_be32(NFS4ERR_RESOURCE);
+	*len = err;
 	return 0;
 }
 
@@ -162,15 +154,9 @@ static __be32 decode_compound_hdr_arg(struct xdr_stream *xdr, struct cb_compound
 	__be32 *p;
 	__be32 status;
 
-	status = decode_string(xdr, &hdr->taglen, &hdr->tag);
+	status = decode_string(xdr, &hdr->taglen, &hdr->tag, CB_OP_TAGLEN_MAXSZ);
 	if (unlikely(status != 0))
 		return status;
-	/* We do not like overly long tags! */
-	if (hdr->taglen > CB_OP_TAGLEN_MAXSZ) {
-		printk("NFS: NFSv4 CALLBACK %s: client sent tag of length %u\n",
-				__func__, hdr->taglen);
-		return htonl(NFS4ERR_RESOURCE);
-	}
 	p = read_buf(xdr, 12);
 	if (unlikely(p == NULL))
 		return htonl(NFS4ERR_RESOURCE);