SUNRPC: Fix the return value of xdr_align_pages()

The callers of xdr_align_pages() expect it to return the number of bytes
of actual XDR data remaining in the pages.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 0afba1b..fbbd1c47 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -742,6 +742,8 @@
 	/* Truncate page data and move it into the tail */
 	if (buf->page_len > len)
 		xdr_shrink_pagelen(buf, buf->page_len - len);
+	else
+		len = buf->page_len;
 	xdr->nwords = XDR_QUADLEN(buf->len - cur);
 	return len;
 }