CIFS: Add echo request support for SMB2

Signed-off-by: Pavel Shilovsky <piastryyy@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 0c53a83..ae9a1e9 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -73,6 +73,9 @@
 /*           (max path length + 1 for null) * 2 for unicode    */
 #define MAX_NAME 514
 
+/* SMB echo "timeout" -- FIXME: tunable? */
+#define SMB_ECHO_INTERVAL (60 * HZ)
+
 #include "cifspdu.h"
 
 #ifndef XATTR_DOS_ATTRIB