GFS2: Add "top dir" flag support

This patch adds support for the "top dir" flag. Currently this is unused
but a subsequent patch is planned which will add support for the
Orlov allocation policy when allocating subdirectories in a parent
with this flag set.

In order to ensure backward compatible behaviour, mkfs.gfs2 does
not currently tag the root directory with this flag, it must always be
set manually.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/include/linux/gfs2_ondisk.h b/include/linux/gfs2_ondisk.h
index fa98bdb..e8ccf6f 100644
--- a/include/linux/gfs2_ondisk.h
+++ b/include/linux/gfs2_ondisk.h
@@ -214,6 +214,7 @@
 	gfs2fl_NoAtime		= 7,
 	gfs2fl_Sync		= 8,
 	gfs2fl_System		= 9,
+	gfs2fl_TopLevel		= 10,
 	gfs2fl_TruncInProg	= 29,
 	gfs2fl_InheritDirectio	= 30,
 	gfs2fl_InheritJdata	= 31,
@@ -230,8 +231,9 @@
 #define GFS2_DIF_NOATIME		0x00000080
 #define GFS2_DIF_SYNC			0x00000100
 #define GFS2_DIF_SYSTEM			0x00000200 /* New in gfs2 */
+#define GFS2_DIF_TOPDIR			0x00000400 /* New in gfs2 */
 #define GFS2_DIF_TRUNC_IN_PROG		0x20000000 /* New in gfs2 */
-#define GFS2_DIF_INHERIT_DIRECTIO	0x40000000
+#define GFS2_DIF_INHERIT_DIRECTIO	0x40000000 /* only in gfs1 */
 #define GFS2_DIF_INHERIT_JDATA		0x80000000
 
 struct gfs2_dinode {