nfsd41: add flag checking for create_session

Teach the NFS server to reject invalid create_session flags.

Also do some minor formatting adjustments.

Signed-off-by: Mi Jinlong <mijinlong@cn.fujitsu.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
index b528f6d..8937727 100644
--- a/include/linux/nfs4.h
+++ b/include/linux/nfs4.h
@@ -570,9 +570,11 @@
 };
 
 /* Create Session Flags */
-#define SESSION4_PERSIST	 0x001
-#define SESSION4_BACK_CHAN 	 0x002
-#define SESSION4_RDMA		 0x004
+#define SESSION4_PERSIST	0x001
+#define SESSION4_BACK_CHAN	0x002
+#define SESSION4_RDMA		0x004
+
+#define SESSION4_FLAG_MASK_A	0x007
 
 enum state_protect_how4 {
 	SP4_NONE	= 0,