diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
index b07f5cd..bcdb34c 100644
--- a/include/linux/nilfs2_fs.h
+++ b/include/linux/nilfs2_fs.h
@@ -271,6 +271,14 @@
 					   segments */
 
 /*
+ * We call DAT, cpfile, and sufile root metadata files.  Inodes of
+ * these files are written in super root block instead of ifile, and
+ * garbage collector doesn't keep any past versions of these files.
+ */
+#define NILFS_ROOT_METADATA_FILE(ino) \
+	((ino) >= NILFS_DAT_INO && (ino) <= NILFS_SUFILE_INO)
+
+/*
  * bytes offset of secondary super block
  */
 #define NILFS_SB2_OFFSET_BYTES(devsize)	((((devsize) >> 12) - 1) << 12)