NFS: Add READ_PLUS hole segment decoding

We keep things simple for now by only decoding a single hole or data
segment returned by the server, even if they returned more to us.
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs42xdr.c

@@ -53,7 +53,7 @@
 #define decode_read_plus_maxsz		(op_decode_hdr_maxsz + \
 					 1 /* rpr_eof */ + \
 					 1 /* rpr_contents count */ + \
-					 NFS42_READ_PLUS_SEGMENT_SIZE)
+					 2 * NFS42_READ_PLUS_SEGMENT_SIZE)
 #define encode_seek_maxsz		(op_encode_hdr_maxsz + \
 					 encode_stateid_maxsz + \
 					 2 /* offset */ + \
@@ -1045,6 +1045,28 @@ static int decode_read_plus_data(struct xdr_stream *xdr, struct nfs_pgio_res *re
 	return 0;
 }
 
+static int decode_read_plus_hole(struct xdr_stream *xdr, struct nfs_pgio_res *res,
+				 uint32_t *eof)
+{
+	uint64_t offset, length, recvd;
+	__be32 *p;
+
+	p = xdr_inline_decode(xdr, 8 + 8);
+	if (unlikely(!p))
+		return -EIO;
+
+	p = xdr_decode_hyper(p, &offset);
+	p = xdr_decode_hyper(p, &length);
+	recvd = xdr_expand_hole(xdr, 0, length);
+	res->count += recvd;
+
+	if (recvd < length) {
+		*eof = 0;
+		return 1;
+	}
+	return 0;
+}
+
 static int decode_read_plus(struct xdr_stream *xdr, struct nfs_pgio_res *res)
 {
 	uint32_t eof, segments, type;
@@ -1071,6 +1093,8 @@ static int decode_read_plus(struct xdr_stream *xdr, struct nfs_pgio_res *res)
 	type = be32_to_cpup(p++);
 	if (type == NFS4_CONTENT_DATA)
 		status = decode_read_plus_data(xdr, res, &eof);
+	else if (type == NFS4_CONTENT_HOLE)
+		status = decode_read_plus_hole(xdr, res, &eof);
 	else
 		return -EINVAL;