fs/yaffs2/yaffs_checkptrw.c - manifest_repos/valens - Git at Google

 /*
  * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
  *
  * Copyright (C) 2002-2018 Aleph One Ltd.
  *
  * 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 General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #include "yaffs_checkptrw.h"
 #include "yaffs_getblockinfo.h"
 #include "yaffs_endian.h"

 struct yaffs_checkpt_chunk_hdr {
 	int version;
 	int seq;
 	u32 sum;
 	u32 xor;
 } ;


 static int apply_chunk_offset(struct yaffs_dev *dev, int chunk)
 {
 	return chunk - dev->chunk_offset;
 }

 static int apply_block_offset(struct yaffs_dev *dev, int block)
 {
 	return block - dev->block_offset;
 }


 static void yaffs2_do_endian_hdr(struct yaffs_dev *dev,
 				 struct yaffs_checkpt_chunk_hdr *hdr)
 {
 	if (!dev->swap_endian)
 		return;
 	hdr->version = swap_s32(hdr->version);
 	hdr->seq     = swap_s32(hdr->seq);
 	hdr->sum     = swap_u32(hdr->sum);
 	hdr->xor     = swap_u32(hdr->xor);
 }

 static void yaffs2_checkpt_init_chunk_hdr(struct yaffs_dev *dev)
 {
 	struct yaffs_checkpt_chunk_hdr hdr;

 	hdr.version = YAFFS_CHECKPOINT_VERSION;
 	hdr.seq = dev->checkpt_page_seq;
 	hdr.sum = dev->checkpt_sum;
 	hdr.xor = dev->checkpt_xor;

 	dev->checkpt_byte_offs = sizeof(hdr);

 	yaffs2_do_endian_hdr(dev, &hdr);
 	memcpy(dev->checkpt_buffer, &hdr, sizeof(hdr));
 }

 static int yaffs2_checkpt_check_chunk_hdr(struct yaffs_dev *dev)
 {
 	struct yaffs_checkpt_chunk_hdr hdr;

 	memcpy(&hdr, dev->checkpt_buffer, sizeof(hdr));
 	yaffs2_do_endian_hdr(dev, &hdr);

 	dev->checkpt_byte_offs = sizeof(hdr);

 	return hdr.version == YAFFS_CHECKPOINT_VERSION &&
 		hdr.seq == dev->checkpt_page_seq &&
 		hdr.sum == dev->checkpt_sum &&
 		hdr.xor == dev->checkpt_xor;
 }

 static int yaffs2_checkpt_space_ok(struct yaffs_dev *dev)
 {
 	int blocks_avail = dev->n_erased_blocks - dev->param.n_reserved_blocks;

 	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 		"checkpt blocks_avail = %d", blocks_avail);

 	return (blocks_avail <= 0) ? 0 : 1;
 }

 static int yaffs_checkpt_erase(struct yaffs_dev *dev)
 {
 	u32 i;

 	if (!dev->drv.drv_erase_fn)
 		return 0;
 	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 		"checking blocks %d to %d",
 		dev->internal_start_block, dev->internal_end_block);

 	for (i = dev->internal_start_block; i <= dev->internal_end_block; i++) {
 		struct yaffs_block_info *bi = yaffs_get_block_info(dev, i);
 		int offset_i = apply_block_offset(dev, i);
 		int result;

 		if (bi->block_state == YAFFS_BLOCK_STATE_CHECKPOINT) {
 			yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 			"erasing checkpt block %d", i);

 			dev->n_erasures++;

 			result = dev->drv.drv_erase_fn(dev, offset_i);
 			if(result) {
 				bi->block_state = YAFFS_BLOCK_STATE_EMPTY;
 				dev->n_erased_blocks++;
 				dev->n_free_chunks +=
 				    dev->param.chunks_per_block;
 			} else {
 				dev->drv.drv_mark_bad_fn(dev, offset_i);
 				bi->block_state = YAFFS_BLOCK_STATE_DEAD;
 			}
 		}
 	}

 	dev->blocks_in_checkpt = 0;

 	return 1;
 }

 static void yaffs2_checkpt_find_erased_block(struct yaffs_dev *dev)
 {
 	u32 i;
 	int blocks_avail = dev->n_erased_blocks - dev->param.n_reserved_blocks;

 	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 		"allocating checkpt block: erased %d reserved %d avail %d next %d ",
 		dev->n_erased_blocks, dev->param.n_reserved_blocks,
 		blocks_avail, dev->checkpt_next_block);

 	if (dev->checkpt_next_block >= 0 &&
 	    dev->checkpt_next_block <= (int)dev->internal_end_block &&
 	    blocks_avail > 0) {

 		for (i = dev->checkpt_next_block; i <= dev->internal_end_block;
 		     i++) {
 			struct yaffs_block_info *bi;

 			bi = yaffs_get_block_info(dev, i);
 			if (bi->block_state == YAFFS_BLOCK_STATE_EMPTY) {
 				dev->checkpt_next_block = i + 1;
 				dev->checkpt_cur_block = i;
 				yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 					"allocating checkpt block %d", i);
 				return;
 			}
 		}
 	}
 	yaffs_trace(YAFFS_TRACE_CHECKPOINT, "out of checkpt blocks");

 	dev->checkpt_next_block = -1;
 	dev->checkpt_cur_block = -1;
 }

 static void yaffs2_checkpt_find_block(struct yaffs_dev *dev)
 {
 	u32 i;
 	struct yaffs_ext_tags tags;

 	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 		"find next checkpt block: start:  blocks %d next %d",
 		dev->blocks_in_checkpt, dev->checkpt_next_block);

 	if (dev->blocks_in_checkpt < dev->checkpt_max_blocks)
 		for (i = dev->checkpt_next_block; i <= dev->internal_end_block;
 		     i++) {
 			int chunk = i * dev->param.chunks_per_block;
 			enum yaffs_block_state state;
 			u32 seq;

 			dev->tagger.read_chunk_tags_fn(dev,
 					apply_chunk_offset(dev, chunk),
 					NULL, &tags);
 			yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 				"find next checkpt block: search: block %d state %d oid %d seq %d eccr %d",
 				i, (int) state,
 				tags.obj_id, tags.seq_number,
 				tags.ecc_result);

 			if (tags.seq_number != YAFFS_SEQUENCE_CHECKPOINT_DATA)
 				continue;

 			dev->tagger.query_block_fn(dev,
 						apply_block_offset(dev, i),
 						&state, &seq);
 			if (state == YAFFS_BLOCK_STATE_DEAD)
 				continue;

 			/* Right kind of block */
 			dev->checkpt_next_block = tags.obj_id;
 			dev->checkpt_cur_block = i;
 			dev->checkpt_block_list[dev->blocks_in_checkpt] = i;
 			dev->blocks_in_checkpt++;
 			yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 				"found checkpt block %d", i);
 			return;
 		}

 	yaffs_trace(YAFFS_TRACE_CHECKPOINT, "found no more checkpt blocks");

 	dev->checkpt_next_block = -1;
 	dev->checkpt_cur_block = -1;
 }

 int yaffs2_checkpt_open(struct yaffs_dev *dev, int writing)
 {
 	u32 i;

 	dev->checkpt_open_write = writing;

 	/* Got the functions we need? */
 	if (!dev->tagger.write_chunk_tags_fn ||
 	    !dev->tagger.read_chunk_tags_fn ||
 	    !dev->drv.drv_erase_fn ||
 	    !dev->drv.drv_mark_bad_fn)
 		return 0;

 	if (writing && !yaffs2_checkpt_space_ok(dev))
 		return 0;

 	if (!dev->checkpt_buffer)
 		dev->checkpt_buffer =
 		    kmalloc(dev->param.total_bytes_per_chunk, GFP_NOFS);
 	if (!dev->checkpt_buffer)
 		return 0;

 	dev->checkpt_page_seq = 0;
 	dev->checkpt_byte_count = 0;
 	dev->checkpt_sum = 0;
 	dev->checkpt_xor = 0;
 	dev->checkpt_cur_block = -1;
 	dev->checkpt_cur_chunk = -1;
 	dev->checkpt_next_block = dev->internal_start_block;

 	if (writing) {
 		memset(dev->checkpt_buffer, 0, dev->data_bytes_per_chunk);
 		yaffs2_checkpt_init_chunk_hdr(dev);
 		return yaffs_checkpt_erase(dev);
 	}

 	/* Opening for a read */
 	/* Set to a value that will kick off a read */
 	dev->checkpt_byte_offs = dev->data_bytes_per_chunk;
 	/* A checkpoint block list of 1 checkpoint block per 16 block is
 	 * (hopefully) going to be way more than we need */
 	dev->blocks_in_checkpt = 0;
 	dev->checkpt_max_blocks =
 	    (dev->internal_end_block - dev->internal_start_block) / 16 + 2;
 	if (!dev->checkpt_block_list)
 		dev->checkpt_block_list =
 		      kmalloc(sizeof(int) * dev->checkpt_max_blocks, GFP_NOFS);

 	if (!dev->checkpt_block_list)
 		return 0;

 	for (i = 0; i < dev->checkpt_max_blocks; i++)
 		dev->checkpt_block_list[i] = -1;

 	return 1;
 }

 int yaffs2_get_checkpt_sum(struct yaffs_dev *dev, u32 * sum)
 {
 	u32 composite_sum;

 	composite_sum = (dev->checkpt_sum << 8) | (dev->checkpt_xor & 0xff);
 	*sum = composite_sum;
 	return 1;
 }

 static int yaffs2_checkpt_flush_buffer(struct yaffs_dev *dev)
 {
 	int chunk;
 	int offset_chunk;
 	struct yaffs_ext_tags tags;

 	if (dev->checkpt_cur_block < 0) {
 		yaffs2_checkpt_find_erased_block(dev);
 		dev->checkpt_cur_chunk = 0;
 	}

 	if (dev->checkpt_cur_block < 0)
 		return 0;

 	tags.is_deleted = 0;
 	tags.obj_id = dev->checkpt_next_block;	/* Hint to next place to look */
 	tags.chunk_id = dev->checkpt_page_seq + 1;
 	tags.seq_number = YAFFS_SEQUENCE_CHECKPOINT_DATA;
 	tags.n_bytes = dev->data_bytes_per_chunk;
 	if (dev->checkpt_cur_chunk == 0) {
 		/* First chunk we write for the block? Set block state to
 		   checkpoint */
 		struct yaffs_block_info *bi =
 		    yaffs_get_block_info(dev, dev->checkpt_cur_block);
 		bi->block_state = YAFFS_BLOCK_STATE_CHECKPOINT;
 		dev->blocks_in_checkpt++;
 	}

 	chunk =
 	    dev->checkpt_cur_block * dev->param.chunks_per_block +
 	    dev->checkpt_cur_chunk;

 	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 		"checkpoint wite buffer nand %d(%d:%d) objid %d chId %d",
 		chunk, dev->checkpt_cur_block, dev->checkpt_cur_chunk,
 		tags.obj_id, tags.chunk_id);

 	offset_chunk = apply_chunk_offset(dev, chunk);

 	dev->n_page_writes++;

 	dev->tagger.write_chunk_tags_fn(dev, offset_chunk,
 				       dev->checkpt_buffer, &tags);
 	dev->checkpt_page_seq++;
 	dev->checkpt_cur_chunk++;
 	if (dev->checkpt_cur_chunk >= (int)dev->param.chunks_per_block) {
 		dev->checkpt_cur_chunk = 0;
 		dev->checkpt_cur_block = -1;
 	}
 	memset(dev->checkpt_buffer, 0, dev->data_bytes_per_chunk);

 	yaffs2_checkpt_init_chunk_hdr(dev);


 	return 1;
 }

 int yaffs2_checkpt_wr(struct yaffs_dev *dev, const void *data, int n_bytes)
 {
 	int i = 0;
 	int ok = 1;
 	u8 *data_bytes = (u8 *) data;

 	if (!dev->checkpt_buffer)
 		return 0;

 	if (!dev->checkpt_open_write)
 		return -1;

 	while (i < n_bytes && ok) {
 		dev->checkpt_buffer[dev->checkpt_byte_offs] = *data_bytes;
 		dev->checkpt_sum += *data_bytes;
 		dev->checkpt_xor ^= *data_bytes;

 		dev->checkpt_byte_offs++;
 		i++;
 		data_bytes++;
 		dev->checkpt_byte_count++;

 		if (dev->checkpt_byte_offs < 0 ||
 		    dev->checkpt_byte_offs >= (int)dev->data_bytes_per_chunk)
 			ok = yaffs2_checkpt_flush_buffer(dev);
 	}

 	return i;
 }

 int yaffs2_checkpt_rd(struct yaffs_dev *dev, void *data, int n_bytes)
 {
 	int i = 0;
 	struct yaffs_ext_tags tags;
 	int chunk;
 	int offset_chunk;
 	u8 *data_bytes = (u8 *) data;

 	if (!dev->checkpt_buffer)
 		return 0;

 	if (dev->checkpt_open_write)
 		return -1;

 	while (i < n_bytes) {

 		if (dev->checkpt_byte_offs < 0 ||
 		    dev->checkpt_byte_offs >= (int)dev->data_bytes_per_chunk) {

 			if (dev->checkpt_cur_block < 0) {
 				yaffs2_checkpt_find_block(dev);
 				dev->checkpt_cur_chunk = 0;
 			}

 			/* Bail out if we can't find a checpoint block */
 			if (dev->checkpt_cur_block < 0)
 				break;

 			chunk = dev->checkpt_cur_block *
 			    dev->param.chunks_per_block +
 			    dev->checkpt_cur_chunk;

 			offset_chunk = apply_chunk_offset(dev, chunk);
 			dev->n_page_reads++;

 			/* Read in the next chunk */
 			dev->tagger.read_chunk_tags_fn(dev,
 						offset_chunk,
 						dev->checkpt_buffer,
 						&tags);

 			/* Bail out if the chunk is corrupted. */
 			if (tags.chunk_id != (u32)(dev->checkpt_page_seq + 1) ||
 			    tags.ecc_result > YAFFS_ECC_RESULT_FIXED ||
 			    tags.seq_number != YAFFS_SEQUENCE_CHECKPOINT_DATA)
 				break;

 			/* Bail out if it is not a checkpoint chunk. */
 			if(!yaffs2_checkpt_check_chunk_hdr(dev))
 				break;

 			dev->checkpt_page_seq++;
 			dev->checkpt_cur_chunk++;

 			if (dev->checkpt_cur_chunk >=
 					(int)dev->param.chunks_per_block)
 				dev->checkpt_cur_block = -1;

 		}

 		*data_bytes = dev->checkpt_buffer[dev->checkpt_byte_offs];
 		dev->checkpt_sum += *data_bytes;
 		dev->checkpt_xor ^= *data_bytes;
 		dev->checkpt_byte_offs++;
 		i++;
 		data_bytes++;
 		dev->checkpt_byte_count++;
 	}

 	return i; /* Number of bytes read */
 }

 int yaffs_checkpt_close(struct yaffs_dev *dev)
 {
 	u32 i;

 	if (dev->checkpt_open_write) {
 		if (dev->checkpt_byte_offs !=
 			sizeof(sizeof(struct yaffs_checkpt_chunk_hdr)))
 			yaffs2_checkpt_flush_buffer(dev);
 	} else if (dev->checkpt_block_list) {
 		for (i = 0;
 		     i < dev->blocks_in_checkpt &&
 		     dev->checkpt_block_list[i] >= 0; i++) {
 			int blk = dev->checkpt_block_list[i];
 			struct yaffs_block_info *bi = NULL;

 			if ((int)dev->internal_start_block <= blk &&
 			    blk <= (int)dev->internal_end_block)
 				bi = yaffs_get_block_info(dev, blk);
 			if (bi && bi->block_state == YAFFS_BLOCK_STATE_EMPTY)
 				bi->block_state = YAFFS_BLOCK_STATE_CHECKPOINT;
 		}
 	}

 	dev->n_free_chunks -=
 		dev->blocks_in_checkpt * dev->param.chunks_per_block;
 	dev->n_erased_blocks -= dev->blocks_in_checkpt;

 	yaffs_trace(YAFFS_TRACE_CHECKPOINT, "checkpoint byte count %d",
 		dev->checkpt_byte_count);

 	if (dev->checkpt_buffer)
 		return 1;
 	else
 		return 0;
 }

 int yaffs2_checkpt_invalidate_stream(struct yaffs_dev *dev)
 {
 	/* Erase the checkpoint data */

 	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
 		"checkpoint invalidate of %d blocks",
 		dev->blocks_in_checkpt);

 	return yaffs_checkpt_erase(dev);
 }
	/*
	* YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
	*
	* Copyright (C) 2002-2018 Aleph One Ltd.
	*
	* 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 General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#include "yaffs_checkptrw.h"
	#include "yaffs_getblockinfo.h"
	#include "yaffs_endian.h"

	struct yaffs_checkpt_chunk_hdr {
	int version;
	int seq;
	u32 sum;
	u32 xor;
	} ;


	static int apply_chunk_offset(struct yaffs_dev *dev, int chunk)
	{
	return chunk - dev->chunk_offset;
	}

	static int apply_block_offset(struct yaffs_dev *dev, int block)
	{
	return block - dev->block_offset;
	}


	static void yaffs2_do_endian_hdr(struct yaffs_dev *dev,
	struct yaffs_checkpt_chunk_hdr *hdr)
	{
	if (!dev->swap_endian)
	return;
	hdr->version = swap_s32(hdr->version);
	hdr->seq = swap_s32(hdr->seq);
	hdr->sum = swap_u32(hdr->sum);
	hdr->xor = swap_u32(hdr->xor);
	}

	static void yaffs2_checkpt_init_chunk_hdr(struct yaffs_dev *dev)
	{
	struct yaffs_checkpt_chunk_hdr hdr;

	hdr.version = YAFFS_CHECKPOINT_VERSION;
	hdr.seq = dev->checkpt_page_seq;
	hdr.sum = dev->checkpt_sum;
	hdr.xor = dev->checkpt_xor;

	dev->checkpt_byte_offs = sizeof(hdr);

	yaffs2_do_endian_hdr(dev, &hdr);
	memcpy(dev->checkpt_buffer, &hdr, sizeof(hdr));
	}

	static int yaffs2_checkpt_check_chunk_hdr(struct yaffs_dev *dev)
	{
	struct yaffs_checkpt_chunk_hdr hdr;

	memcpy(&hdr, dev->checkpt_buffer, sizeof(hdr));
	yaffs2_do_endian_hdr(dev, &hdr);

	dev->checkpt_byte_offs = sizeof(hdr);

	return hdr.version == YAFFS_CHECKPOINT_VERSION &&
	hdr.seq == dev->checkpt_page_seq &&
	hdr.sum == dev->checkpt_sum &&
	hdr.xor == dev->checkpt_xor;
	}

	static int yaffs2_checkpt_space_ok(struct yaffs_dev *dev)
	{
	int blocks_avail = dev->n_erased_blocks - dev->param.n_reserved_blocks;

	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"checkpt blocks_avail = %d", blocks_avail);

	return (blocks_avail <= 0) ? 0 : 1;
	}

	static int yaffs_checkpt_erase(struct yaffs_dev *dev)
	{
	u32 i;

	if (!dev->drv.drv_erase_fn)
	return 0;
	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"checking blocks %d to %d",
	dev->internal_start_block, dev->internal_end_block);

	for (i = dev->internal_start_block; i <= dev->internal_end_block; i++) {
	struct yaffs_block_info *bi = yaffs_get_block_info(dev, i);
	int offset_i = apply_block_offset(dev, i);
	int result;

	if (bi->block_state == YAFFS_BLOCK_STATE_CHECKPOINT) {
	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"erasing checkpt block %d", i);

	dev->n_erasures++;

	result = dev->drv.drv_erase_fn(dev, offset_i);
	if(result) {
	bi->block_state = YAFFS_BLOCK_STATE_EMPTY;
	dev->n_erased_blocks++;
	dev->n_free_chunks +=
	dev->param.chunks_per_block;
	} else {
	dev->drv.drv_mark_bad_fn(dev, offset_i);
	bi->block_state = YAFFS_BLOCK_STATE_DEAD;
	}
	}
	}

	dev->blocks_in_checkpt = 0;

	return 1;
	}

	static void yaffs2_checkpt_find_erased_block(struct yaffs_dev *dev)
	{
	u32 i;
	int blocks_avail = dev->n_erased_blocks - dev->param.n_reserved_blocks;

	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"allocating checkpt block: erased %d reserved %d avail %d next %d ",
	dev->n_erased_blocks, dev->param.n_reserved_blocks,
	blocks_avail, dev->checkpt_next_block);

	if (dev->checkpt_next_block >= 0 &&
	dev->checkpt_next_block <= (int)dev->internal_end_block &&
	blocks_avail > 0) {

	for (i = dev->checkpt_next_block; i <= dev->internal_end_block;
	i++) {
	struct yaffs_block_info *bi;

	bi = yaffs_get_block_info(dev, i);
	if (bi->block_state == YAFFS_BLOCK_STATE_EMPTY) {
	dev->checkpt_next_block = i + 1;
	dev->checkpt_cur_block = i;
	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"allocating checkpt block %d", i);
	return;
	}
	}
	}
	yaffs_trace(YAFFS_TRACE_CHECKPOINT, "out of checkpt blocks");

	dev->checkpt_next_block = -1;
	dev->checkpt_cur_block = -1;
	}

	static void yaffs2_checkpt_find_block(struct yaffs_dev *dev)
	{
	u32 i;
	struct yaffs_ext_tags tags;

	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"find next checkpt block: start: blocks %d next %d",
	dev->blocks_in_checkpt, dev->checkpt_next_block);

	if (dev->blocks_in_checkpt < dev->checkpt_max_blocks)
	for (i = dev->checkpt_next_block; i <= dev->internal_end_block;
	i++) {
	int chunk = i * dev->param.chunks_per_block;
	enum yaffs_block_state state;
	u32 seq;

	dev->tagger.read_chunk_tags_fn(dev,
	apply_chunk_offset(dev, chunk),
	NULL, &tags);
	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"find next checkpt block: search: block %d state %d oid %d seq %d eccr %d",
	i, (int) state,
	tags.obj_id, tags.seq_number,
	tags.ecc_result);

	if (tags.seq_number != YAFFS_SEQUENCE_CHECKPOINT_DATA)
	continue;

	dev->tagger.query_block_fn(dev,
	apply_block_offset(dev, i),
	&state, &seq);
	if (state == YAFFS_BLOCK_STATE_DEAD)
	continue;

	/* Right kind of block */
	dev->checkpt_next_block = tags.obj_id;
	dev->checkpt_cur_block = i;
	dev->checkpt_block_list[dev->blocks_in_checkpt] = i;
	dev->blocks_in_checkpt++;
	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"found checkpt block %d", i);
	return;
	}

	yaffs_trace(YAFFS_TRACE_CHECKPOINT, "found no more checkpt blocks");

	dev->checkpt_next_block = -1;
	dev->checkpt_cur_block = -1;
	}

	int yaffs2_checkpt_open(struct yaffs_dev *dev, int writing)
	{
	u32 i;

	dev->checkpt_open_write = writing;

	/* Got the functions we need? */
	if (!dev->tagger.write_chunk_tags_fn \|\|
	!dev->tagger.read_chunk_tags_fn \|\|
	!dev->drv.drv_erase_fn \|\|
	!dev->drv.drv_mark_bad_fn)
	return 0;

	if (writing && !yaffs2_checkpt_space_ok(dev))
	return 0;

	if (!dev->checkpt_buffer)
	dev->checkpt_buffer =
	kmalloc(dev->param.total_bytes_per_chunk, GFP_NOFS);
	if (!dev->checkpt_buffer)
	return 0;

	dev->checkpt_page_seq = 0;
	dev->checkpt_byte_count = 0;
	dev->checkpt_sum = 0;
	dev->checkpt_xor = 0;
	dev->checkpt_cur_block = -1;
	dev->checkpt_cur_chunk = -1;
	dev->checkpt_next_block = dev->internal_start_block;

	if (writing) {
	memset(dev->checkpt_buffer, 0, dev->data_bytes_per_chunk);
	yaffs2_checkpt_init_chunk_hdr(dev);
	return yaffs_checkpt_erase(dev);
	}

	/* Opening for a read */
	/* Set to a value that will kick off a read */
	dev->checkpt_byte_offs = dev->data_bytes_per_chunk;
	/* A checkpoint block list of 1 checkpoint block per 16 block is
	* (hopefully) going to be way more than we need */
	dev->blocks_in_checkpt = 0;
	dev->checkpt_max_blocks =
	(dev->internal_end_block - dev->internal_start_block) / 16 + 2;
	if (!dev->checkpt_block_list)
	dev->checkpt_block_list =
	kmalloc(sizeof(int) * dev->checkpt_max_blocks, GFP_NOFS);

	if (!dev->checkpt_block_list)
	return 0;

	for (i = 0; i < dev->checkpt_max_blocks; i++)
	dev->checkpt_block_list[i] = -1;

	return 1;
	}

	int yaffs2_get_checkpt_sum(struct yaffs_dev dev, u32 sum)
	{
	u32 composite_sum;

	composite_sum = (dev->checkpt_sum << 8) \| (dev->checkpt_xor & 0xff);
	*sum = composite_sum;
	return 1;
	}

	static int yaffs2_checkpt_flush_buffer(struct yaffs_dev *dev)
	{
	int chunk;
	int offset_chunk;
	struct yaffs_ext_tags tags;

	if (dev->checkpt_cur_block < 0) {
	yaffs2_checkpt_find_erased_block(dev);
	dev->checkpt_cur_chunk = 0;
	}

	if (dev->checkpt_cur_block < 0)
	return 0;

	tags.is_deleted = 0;
	tags.obj_id = dev->checkpt_next_block; /* Hint to next place to look */
	tags.chunk_id = dev->checkpt_page_seq + 1;
	tags.seq_number = YAFFS_SEQUENCE_CHECKPOINT_DATA;
	tags.n_bytes = dev->data_bytes_per_chunk;
	if (dev->checkpt_cur_chunk == 0) {
	/* First chunk we write for the block? Set block state to
	checkpoint */
	struct yaffs_block_info *bi =
	yaffs_get_block_info(dev, dev->checkpt_cur_block);
	bi->block_state = YAFFS_BLOCK_STATE_CHECKPOINT;
	dev->blocks_in_checkpt++;
	}

	chunk =
	dev->checkpt_cur_block * dev->param.chunks_per_block +
	dev->checkpt_cur_chunk;

	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"checkpoint wite buffer nand %d(%d:%d) objid %d chId %d",
	chunk, dev->checkpt_cur_block, dev->checkpt_cur_chunk,
	tags.obj_id, tags.chunk_id);

	offset_chunk = apply_chunk_offset(dev, chunk);

	dev->n_page_writes++;

	dev->tagger.write_chunk_tags_fn(dev, offset_chunk,
	dev->checkpt_buffer, &tags);
	dev->checkpt_page_seq++;
	dev->checkpt_cur_chunk++;
	if (dev->checkpt_cur_chunk >= (int)dev->param.chunks_per_block) {
	dev->checkpt_cur_chunk = 0;
	dev->checkpt_cur_block = -1;
	}
	memset(dev->checkpt_buffer, 0, dev->data_bytes_per_chunk);

	yaffs2_checkpt_init_chunk_hdr(dev);


	return 1;
	}

	int yaffs2_checkpt_wr(struct yaffs_dev dev, const void data, int n_bytes)
	{
	int i = 0;
	int ok = 1;
	u8 data_bytes = (u8 ) data;

	if (!dev->checkpt_buffer)
	return 0;

	if (!dev->checkpt_open_write)
	return -1;

	while (i < n_bytes && ok) {
	dev->checkpt_buffer[dev->checkpt_byte_offs] = *data_bytes;
	dev->checkpt_sum += *data_bytes;
	dev->checkpt_xor ^= *data_bytes;

	dev->checkpt_byte_offs++;
	i++;
	data_bytes++;
	dev->checkpt_byte_count++;

	if (dev->checkpt_byte_offs < 0 \|\|
	dev->checkpt_byte_offs >= (int)dev->data_bytes_per_chunk)
	ok = yaffs2_checkpt_flush_buffer(dev);
	}

	return i;
	}

	int yaffs2_checkpt_rd(struct yaffs_dev dev, void data, int n_bytes)
	{
	int i = 0;
	struct yaffs_ext_tags tags;
	int chunk;
	int offset_chunk;
	u8 data_bytes = (u8 ) data;

	if (!dev->checkpt_buffer)
	return 0;

	if (dev->checkpt_open_write)
	return -1;

	while (i < n_bytes) {

	if (dev->checkpt_byte_offs < 0 \|\|
	dev->checkpt_byte_offs >= (int)dev->data_bytes_per_chunk) {

	if (dev->checkpt_cur_block < 0) {
	yaffs2_checkpt_find_block(dev);
	dev->checkpt_cur_chunk = 0;
	}

	/* Bail out if we can't find a checpoint block */
	if (dev->checkpt_cur_block < 0)
	break;

	chunk = dev->checkpt_cur_block *
	dev->param.chunks_per_block +
	dev->checkpt_cur_chunk;

	offset_chunk = apply_chunk_offset(dev, chunk);
	dev->n_page_reads++;

	/* Read in the next chunk */
	dev->tagger.read_chunk_tags_fn(dev,
	offset_chunk,
	dev->checkpt_buffer,
	&tags);

	/* Bail out if the chunk is corrupted. */
	if (tags.chunk_id != (u32)(dev->checkpt_page_seq + 1) \|\|
	tags.ecc_result > YAFFS_ECC_RESULT_FIXED \|\|
	tags.seq_number != YAFFS_SEQUENCE_CHECKPOINT_DATA)
	break;

	/* Bail out if it is not a checkpoint chunk. */
	if(!yaffs2_checkpt_check_chunk_hdr(dev))
	break;

	dev->checkpt_page_seq++;
	dev->checkpt_cur_chunk++;

	if (dev->checkpt_cur_chunk >=
	(int)dev->param.chunks_per_block)
	dev->checkpt_cur_block = -1;

	}

	*data_bytes = dev->checkpt_buffer[dev->checkpt_byte_offs];
	dev->checkpt_sum += *data_bytes;
	dev->checkpt_xor ^= *data_bytes;
	dev->checkpt_byte_offs++;
	i++;
	data_bytes++;
	dev->checkpt_byte_count++;
	}

	return i; /* Number of bytes read */
	}

	int yaffs_checkpt_close(struct yaffs_dev *dev)
	{
	u32 i;

	if (dev->checkpt_open_write) {
	if (dev->checkpt_byte_offs !=
	sizeof(sizeof(struct yaffs_checkpt_chunk_hdr)))
	yaffs2_checkpt_flush_buffer(dev);
	} else if (dev->checkpt_block_list) {
	for (i = 0;
	i < dev->blocks_in_checkpt &&
	dev->checkpt_block_list[i] >= 0; i++) {
	int blk = dev->checkpt_block_list[i];
	struct yaffs_block_info *bi = NULL;

	if ((int)dev->internal_start_block <= blk &&
	blk <= (int)dev->internal_end_block)
	bi = yaffs_get_block_info(dev, blk);
	if (bi && bi->block_state == YAFFS_BLOCK_STATE_EMPTY)
	bi->block_state = YAFFS_BLOCK_STATE_CHECKPOINT;
	}
	}

	dev->n_free_chunks -=
	dev->blocks_in_checkpt * dev->param.chunks_per_block;
	dev->n_erased_blocks -= dev->blocks_in_checkpt;

	yaffs_trace(YAFFS_TRACE_CHECKPOINT, "checkpoint byte count %d",
	dev->checkpt_byte_count);

	if (dev->checkpt_buffer)
	return 1;
	else
	return 0;
	}

	int yaffs2_checkpt_invalidate_stream(struct yaffs_dev *dev)
	{
	/* Erase the checkpoint data */

	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
	"checkpoint invalidate of %d blocks",
	dev->blocks_in_checkpt);

	return yaffs_checkpt_erase(dev);
	}