ext4: Avoid corruption of directories with hash tree indexes

While directories can be read using the old linear scan method, adding a
new file would require updating the index tree (alternatively, the whole
tree could be removed).

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
diff --git a/include/ext4fs.h b/include/ext4fs.h
index e3f6216..6e31c73 100644
--- a/include/ext4fs.h
+++ b/include/ext4fs.h
@@ -28,6 +28,7 @@
 #define __EXT4__
 #include <ext_common.h>
 
+#define EXT4_INDEX_FL		0x00001000 /* Inode uses hash tree index */
 #define EXT4_EXTENTS_FL		0x00080000 /* Inode uses extents */
 #define EXT4_EXT_MAGIC			0xf30a
 #define EXT4_FEATURE_RO_COMPAT_GDT_CSUM	0x0010