mm: bdi init hooks

provide BDI constructor/destructor hooks

[akpm@linux-foundation.org: compile fix]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index ef2b46d..8428d5b 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -223,7 +223,17 @@
 
 int __init init_rootfs(void)
 {
-	return register_filesystem(&rootfs_fs_type);
+	int err;
+
+	err = bdi_init(&ramfs_backing_dev_info);
+	if (err)
+		return err;
+
+	err = register_filesystem(&rootfs_fs_type);
+	if (err)
+		bdi_destroy(&ramfs_backing_dev_info);
+
+	return err;
 }
 
 MODULE_LICENSE("GPL");