--- linux-4.9.37/fs/yaffs2/yaffs_bitmap.h	1970-01-01 03:00:00.000000000 +0300
+++ linux-4.9.y/fs/yaffs2/yaffs_bitmap.h	2021-06-07 13:01:34.000000000 +0300
@@ -0,0 +1,33 @@
+/*
+ * YAFFS: Yet another Flash File System . A NAND-flash specific file system.
+ *
+ * Copyright (C) 2002-2011 Aleph One Ltd.
+ *   for Toby Churchill Ltd and Brightstar Engineering
+ *
+ * Created by Charles Manning <charles@aleph1.co.uk>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 2.1 as
+ * published by the Free Software Foundation.
+ *
+ * Note: Only YAFFS headers are LGPL, YAFFS C code is covered by GPL.
+ */
+
+/*
+ * Chunk bitmap manipulations
+ */
+
+#ifndef __YAFFS_BITMAP_H__
+#define __YAFFS_BITMAP_H__
+
+#include "yaffs_guts.h"
+
+void yaffs_verify_chunk_bit_id(struct yaffs_dev *dev, int blk, int chunk);
+void yaffs_clear_chunk_bits(struct yaffs_dev *dev, int blk);
+void yaffs_clear_chunk_bit(struct yaffs_dev *dev, int blk, int chunk);
+void yaffs_set_chunk_bit(struct yaffs_dev *dev, int blk, int chunk);
+int yaffs_check_chunk_bit(struct yaffs_dev *dev, int blk, int chunk);
+int yaffs_still_some_chunks(struct yaffs_dev *dev, int blk);
+int yaffs_count_chunk_bits(struct yaffs_dev *dev, int blk);
+
+#endif