SUNRPC: Add the helper xdr_stream_pos

Add a helper to report the current offset from the start of the
xdr_stream.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/sunrpc/xdr.h

@@ -218,6 +218,7 @@ extern void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32
 extern __be32 *xdr_reserve_space(struct xdr_stream *xdr, size_t nbytes);
 extern void xdr_write_pages(struct xdr_stream *xdr, struct page **pages,
 		unsigned int base, unsigned int len);
+extern unsigned int xdr_stream_pos(const struct xdr_stream *xdr);
 extern void xdr_init_decode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p);
 extern void xdr_init_decode_pages(struct xdr_stream *xdr, struct xdr_buf *buf,
 		struct page **pages, unsigned int len);

net/sunrpc/xdr.c

@@ -454,6 +454,16 @@ xdr_shift_buf(struct xdr_buf *buf, size_t len)
 }
 EXPORT_SYMBOL_GPL(xdr_shift_buf);
 
+/**
+ * xdr_stream_pos - Return the current offset from the start of the xdr_stream
+ * @xdr: pointer to struct xdr_stream
+ */
+unsigned int xdr_stream_pos(const struct xdr_stream *xdr)
+{
+	return (unsigned int)(XDR_QUADLEN(xdr->buf->len) - xdr->nwords) << 2;
+}
+EXPORT_SYMBOL_GPL(xdr_stream_pos);
+
 /**
  * xdr_init_encode - Initialize a struct xdr_stream for sending data.
  * @xdr: pointer to xdr_stream struct