diff --git a/fs/super.c b/fs/super.c
index 7e9dd4c..0d89e93 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -71,6 +71,7 @@
 #else
 		INIT_LIST_HEAD(&s->s_files);
 #endif
+		s->s_bdi = &default_backing_dev_info;
 		INIT_LIST_HEAD(&s->s_instances);
 		INIT_HLIST_BL_HEAD(&s->s_anon);
 		INIT_LIST_HEAD(&s->s_inodes);
@@ -1003,6 +1004,7 @@
 	}
 	BUG_ON(!mnt->mnt_sb);
 	WARN_ON(!mnt->mnt_sb->s_bdi);
+	WARN_ON(mnt->mnt_sb->s_bdi == &default_backing_dev_info);
 	mnt->mnt_sb->s_flags |= MS_BORN;
 
 	error = security_sb_kern_mount(mnt->mnt_sb, flags, secdata);
diff --git a/fs/sync.c b/fs/sync.c
index ba76b96..412dc89 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -33,7 +33,7 @@
 	 * This should be safe, as we require bdi backing to actually
 	 * write out data in the first place
 	 */
-	if (!sb->s_bdi || sb->s_bdi == &noop_backing_dev_info)
+	if (sb->s_bdi == &noop_backing_dev_info)
 		return 0;
 
 	if (sb->s_qcop && sb->s_qcop->quota_sync)
@@ -79,7 +79,7 @@
 
 static void sync_one_sb(struct super_block *sb, void *arg)
 {
-	if (!(sb->s_flags & MS_RDONLY) && sb->s_bdi)
+	if (!(sb->s_flags & MS_RDONLY))
 		__sync_filesystem(sb, *(int *)arg);
 }
 /*
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index c91e139..8fe9d34 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -598,7 +598,7 @@
 	spin_lock(&sb_lock);
 	list_for_each_entry(sb, &super_blocks, s_list) {
 		if (sb->s_bdi == bdi)
-			sb->s_bdi = NULL;
+			sb->s_bdi = &default_backing_dev_info;
 	}
 	spin_unlock(&sb_lock);
 }