ceph: handle session flush message

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
index 2ad7b86..26bb587 100644
--- a/include/linux/ceph/ceph_fs.h
+++ b/include/linux/ceph/ceph_fs.h
@@ -282,6 +282,8 @@
 	CEPH_SESSION_RENEWCAPS,
 	CEPH_SESSION_STALE,
 	CEPH_SESSION_RECALL_STATE,
+	CEPH_SESSION_FLUSHMSG,
+	CEPH_SESSION_FLUSHMSG_ACK,
 };
 
 extern const char *ceph_session_op_name(int op);