ocfs2: Add dir_resv_level mount option

The default behavior for directory reservations stays the same, but we add a
mount option so people can tweak the size of directory reservations
according to their workloads.

Signed-off-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index 09d7aee..a388528 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -356,6 +356,7 @@
 	struct ocfs2_reservation_map	osb_la_resmap;
 
 	unsigned int	osb_resv_level;
+	unsigned int	osb_dir_resv_level;
 
 	/* Next three fields are for local node slot recovery during
 	 * mount. */