fs/yaffs2/yaffs_checkptrw.c - kernel/windcharger - Git at Google

 /*
  * YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
  *
  * Copyright (C) 2002-2010 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 General Public License version 2 as
  * published by the Free Software Foundation.
  */

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

 static int yaffs2_checkpt_space_ok(yaffs_dev_t *dev)
 {
 	int blocksAvailable = dev->n_erased_blocks - dev->param.n_reserved_blocks;

 	T(YAFFS_TRACE_CHECKPOINT,
 		(TSTR("checkpt blocks available = %d" TENDSTR),
 		blocksAvailable));

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


 static int yaffs_checkpt_erase(yaffs_dev_t *dev)
 {
 	int i;

 	if (!dev->param.erase_fn)
 		return 0;
 	T(YAFFS_TRACE_CHECKPOINT, (TSTR("checking blocks %d to %d"TENDSTR),
 		dev->internal_start_block, dev->internal_end_block));

 	for (i = dev->internal_start_block; i <= dev->internal_end_block; i++) {
 		yaffs_block_info_t *bi = yaffs_get_block_info(dev, i);
 		if (bi->block_state == YAFFS_BLOCK_STATE_CHECKPOINT) {
 			T(YAFFS_TRACE_CHECKPOINT, (TSTR("erasing checkpt block %d"TENDSTR), i));

 			dev->n_erasures++;

 			if (dev->param.erase_fn(dev, i - dev->block_offset /* realign */)) {
 				bi->block_state = YAFFS_BLOCK_STATE_EMPTY;
 				dev->n_erased_blocks++;
 				dev->n_free_chunks += dev->param.chunks_per_block;
 			} else {
 				dev->param.bad_block_fn(dev, i);
 				bi->block_state = YAFFS_BLOCK_STATE_DEAD;
 			}
 		}
 	}

 	dev->blocks_in_checkpt = 0;

 	return 1;
 }


 static void yaffs2_checkpt_find_erased_block(yaffs_dev_t *dev)
 {
 	int  i;
 	int blocksAvailable = dev->n_erased_blocks - dev->param.n_reserved_blocks;
 	T(YAFFS_TRACE_CHECKPOINT,
 		(TSTR("allocating checkpt block: erased %d reserved %d avail %d next %d "TENDSTR),
 		dev->n_erased_blocks, dev->param.n_reserved_blocks, blocksAvailable, dev->checkpt_next_block));

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

 		for (i = dev->checkpt_next_block; i <= dev->internal_end_block; i++) {
 			yaffs_block_info_t *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;
 				T(YAFFS_TRACE_CHECKPOINT, (TSTR("allocating checkpt block %d"TENDSTR), i));
 				return;
 			}
 		}
 	}
 	T(YAFFS_TRACE_CHECKPOINT, (TSTR("out of checkpt blocks"TENDSTR)));

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

 static void yaffs2_checkpt_find_block(yaffs_dev_t *dev)
 {
 	int  i;
 	yaffs_ext_tags tags;

 	T(YAFFS_TRACE_CHECKPOINT, (TSTR("find next checkpt block: start:  blocks %d next %d" TENDSTR),
 		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;
 			int realignedChunk = chunk - dev->chunk_offset;

 			dev->param.read_chunk_tags_fn(dev, realignedChunk,
 					NULL, &tags);
 			T(YAFFS_TRACE_CHECKPOINT, (TSTR("find next checkpt block: search: block %d oid %d seq %d eccr %d" TENDSTR),
 				i, tags.obj_id, tags.seq_number, tags.ecc_result));

 			if (tags.seq_number == YAFFS_SEQUENCE_CHECKPOINT_DATA) {
 				/* 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++;
 				T(YAFFS_TRACE_CHECKPOINT, (TSTR("found checkpt block %d"TENDSTR), i));
 				return;
 			}
 		}

 	T(YAFFS_TRACE_CHECKPOINT, (TSTR("found no more checkpt blocks"TENDSTR)));

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


 int yaffs2_checkpt_open(yaffs_dev_t *dev, int forWriting)
 {


 	dev->checkpt_open_write = forWriting;

 	/* Got the functions we need? */
 	if (!dev->param.write_chunk_tags_fn ||
 		!dev->param.read_chunk_tags_fn ||
 		!dev->param.erase_fn ||
 		!dev->param.bad_block_fn)
 		return 0;

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

 	if (!dev->checkpt_buffer)
 		dev->checkpt_buffer = YMALLOC_DMA(dev->param.total_bytes_per_chunk);
 	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;

 	/* Erase all the blocks in the checkpoint area */
 	if (forWriting) {
 		memset(dev->checkpt_buffer, 0, dev->data_bytes_per_chunk);
 		dev->checkpt_byte_offs = 0;
 		return yaffs_checkpt_erase(dev);
 	} else {
 		int i;
 		/* 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;
 		dev->checkpt_block_list = YMALLOC(sizeof(int) * dev->checkpt_max_blocks);
 		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(yaffs_dev_t *dev, __u32 *sum)
 {
 	__u32 compositeSum;
 	compositeSum =  (dev->checkpt_sum << 8) | (dev->checkpt_xor & 0xFF);
 	*sum = compositeSum;
 	return 1;
 }

 static int yaffs2_checkpt_flush_buffer(yaffs_dev_t *dev)
 {
 	int chunk;
 	int realignedChunk;

 	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 */
 		yaffs_block_info_t *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;


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

 	realignedChunk = chunk - dev->chunk_offset;

 	dev->n_page_writes++;

 	dev->param.write_chunk_tags_fn(dev, realignedChunk,
 			dev->checkpt_buffer, &tags);
 	dev->checkpt_byte_offs = 0;
 	dev->checkpt_page_seq++;
 	dev->checkpt_cur_chunk++;
 	if (dev->checkpt_cur_chunk >= 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);

 	return 1;
 }


 int yaffs2_checkpt_wr(yaffs_dev_t *dev, const void *data, int n_bytes)
 {
 	int i = 0;
 	int ok = 1;


 	__u8 * dataBytes = (__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] = *dataBytes;
 		dev->checkpt_sum += *dataBytes;
 		dev->checkpt_xor ^= *dataBytes;

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


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

 	return i;
 }

 int yaffs2_checkpt_rd(yaffs_dev_t *dev, void *data, int n_bytes)
 {
 	int i = 0;
 	int ok = 1;
 	yaffs_ext_tags tags;


 	int chunk;
 	int realignedChunk;

 	__u8 *dataBytes = (__u8 *)data;

 	if (!dev->checkpt_buffer)
 		return 0;

 	if (dev->checkpt_open_write)
 		return -1;

 	while (i < n_bytes && ok) {


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

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

 			if (dev->checkpt_cur_block < 0)
 				ok = 0;
 			else {
 				chunk = dev->checkpt_cur_block *
 					dev->param.chunks_per_block +
 					dev->checkpt_cur_chunk;

 				realignedChunk = chunk - dev->chunk_offset;

 				dev->n_page_reads++;

 				/* read in the next chunk */
 				/* printf("read checkpoint page %d\n",dev->checkpointPage); */
 				dev->param.read_chunk_tags_fn(dev,
 						realignedChunk,
 						dev->checkpt_buffer,
 						&tags);

 				if (tags.chunk_id != (dev->checkpt_page_seq + 1) ||
 					tags.ecc_result > YAFFS_ECC_RESULT_FIXED ||
 					tags.seq_number != YAFFS_SEQUENCE_CHECKPOINT_DATA)
 					ok = 0;

 				dev->checkpt_byte_offs = 0;
 				dev->checkpt_page_seq++;
 				dev->checkpt_cur_chunk++;

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

 		if (ok) {
 			*dataBytes = dev->checkpt_buffer[dev->checkpt_byte_offs];
 			dev->checkpt_sum += *dataBytes;
 			dev->checkpt_xor ^= *dataBytes;
 			dev->checkpt_byte_offs++;
 			i++;
 			dataBytes++;
 			dev->checkpt_byte_count++;
 		}
 	}

 	return 	i;
 }

 int yaffs_checkpt_close(yaffs_dev_t *dev)
 {

 	if (dev->checkpt_open_write) {
 		if (dev->checkpt_byte_offs != 0)
 			yaffs2_checkpt_flush_buffer(dev);
 	} else if(dev->checkpt_block_list){
 		int i;
 		for (i = 0; i < dev->blocks_in_checkpt && dev->checkpt_block_list[i] >= 0; i++) {
 			int blk = dev->checkpt_block_list[i];
 			yaffs_block_info_t *bi = NULL;
 			if( dev->internal_start_block <= blk && blk <= 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;
 			else {
 				/* Todo this looks odd... */
 			}
 		}
 		YFREE(dev->checkpt_block_list);
 		dev->checkpt_block_list = NULL;
 	}

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


 	T(YAFFS_TRACE_CHECKPOINT, (TSTR("checkpoint byte count %d" TENDSTR),
 			dev->checkpt_byte_count));

 	if (dev->checkpt_buffer) {
 		/* free the buffer */
 		YFREE(dev->checkpt_buffer);
 		dev->checkpt_buffer = NULL;
 		return 1;
 	} else
 		return 0;
 }

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

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

 	return yaffs_checkpt_erase(dev);
 }
	/*
	* YAFFS: Yet Another Flash File System. A NAND-flash specific file system.
	*
	* Copyright (C) 2002-2010 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 General Public License version 2 as
	* published by the Free Software Foundation.
	*/

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

	static int yaffs2_checkpt_space_ok(yaffs_dev_t *dev)
	{
	int blocksAvailable = dev->n_erased_blocks - dev->param.n_reserved_blocks;

	T(YAFFS_TRACE_CHECKPOINT,
	(TSTR("checkpt blocks available = %d" TENDSTR),
	blocksAvailable));

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


	static int yaffs_checkpt_erase(yaffs_dev_t *dev)
	{
	int i;

	if (!dev->param.erase_fn)
	return 0;
	T(YAFFS_TRACE_CHECKPOINT, (TSTR("checking blocks %d to %d"TENDSTR),
	dev->internal_start_block, dev->internal_end_block));

	for (i = dev->internal_start_block; i <= dev->internal_end_block; i++) {
	yaffs_block_info_t *bi = yaffs_get_block_info(dev, i);
	if (bi->block_state == YAFFS_BLOCK_STATE_CHECKPOINT) {
	T(YAFFS_TRACE_CHECKPOINT, (TSTR("erasing checkpt block %d"TENDSTR), i));

	dev->n_erasures++;

	if (dev->param.erase_fn(dev, i - dev->block_offset /* realign */)) {
	bi->block_state = YAFFS_BLOCK_STATE_EMPTY;
	dev->n_erased_blocks++;
	dev->n_free_chunks += dev->param.chunks_per_block;
	} else {
	dev->param.bad_block_fn(dev, i);
	bi->block_state = YAFFS_BLOCK_STATE_DEAD;
	}
	}
	}

	dev->blocks_in_checkpt = 0;

	return 1;
	}


	static void yaffs2_checkpt_find_erased_block(yaffs_dev_t *dev)
	{
	int i;
	int blocksAvailable = dev->n_erased_blocks - dev->param.n_reserved_blocks;
	T(YAFFS_TRACE_CHECKPOINT,
	(TSTR("allocating checkpt block: erased %d reserved %d avail %d next %d "TENDSTR),
	dev->n_erased_blocks, dev->param.n_reserved_blocks, blocksAvailable, dev->checkpt_next_block));

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

	for (i = dev->checkpt_next_block; i <= dev->internal_end_block; i++) {
	yaffs_block_info_t *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;
	T(YAFFS_TRACE_CHECKPOINT, (TSTR("allocating checkpt block %d"TENDSTR), i));
	return;
	}
	}
	}
	T(YAFFS_TRACE_CHECKPOINT, (TSTR("out of checkpt blocks"TENDSTR)));

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

	static void yaffs2_checkpt_find_block(yaffs_dev_t *dev)
	{
	int i;
	yaffs_ext_tags tags;

	T(YAFFS_TRACE_CHECKPOINT, (TSTR("find next checkpt block: start: blocks %d next %d" TENDSTR),
	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;
	int realignedChunk = chunk - dev->chunk_offset;

	dev->param.read_chunk_tags_fn(dev, realignedChunk,
	NULL, &tags);
	T(YAFFS_TRACE_CHECKPOINT, (TSTR("find next checkpt block: search: block %d oid %d seq %d eccr %d" TENDSTR),
	i, tags.obj_id, tags.seq_number, tags.ecc_result));

	if (tags.seq_number == YAFFS_SEQUENCE_CHECKPOINT_DATA) {
	/* 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++;
	T(YAFFS_TRACE_CHECKPOINT, (TSTR("found checkpt block %d"TENDSTR), i));
	return;
	}
	}

	T(YAFFS_TRACE_CHECKPOINT, (TSTR("found no more checkpt blocks"TENDSTR)));

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


	int yaffs2_checkpt_open(yaffs_dev_t *dev, int forWriting)
	{


	dev->checkpt_open_write = forWriting;

	/* Got the functions we need? */
	if (!dev->param.write_chunk_tags_fn \|\|
	!dev->param.read_chunk_tags_fn \|\|
	!dev->param.erase_fn \|\|
	!dev->param.bad_block_fn)
	return 0;

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

	if (!dev->checkpt_buffer)
	dev->checkpt_buffer = YMALLOC_DMA(dev->param.total_bytes_per_chunk);
	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;

	/* Erase all the blocks in the checkpoint area */
	if (forWriting) {
	memset(dev->checkpt_buffer, 0, dev->data_bytes_per_chunk);
	dev->checkpt_byte_offs = 0;
	return yaffs_checkpt_erase(dev);
	} else {
	int i;
	/* 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;
	dev->checkpt_block_list = YMALLOC(sizeof(int) * dev->checkpt_max_blocks);
	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(yaffs_dev_t dev, __u32 sum)
	{
	__u32 compositeSum;
	compositeSum = (dev->checkpt_sum << 8) \| (dev->checkpt_xor & 0xFF);
	*sum = compositeSum;
	return 1;
	}

	static int yaffs2_checkpt_flush_buffer(yaffs_dev_t *dev)
	{
	int chunk;
	int realignedChunk;

	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 */
	yaffs_block_info_t *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;


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

	realignedChunk = chunk - dev->chunk_offset;

	dev->n_page_writes++;

	dev->param.write_chunk_tags_fn(dev, realignedChunk,
	dev->checkpt_buffer, &tags);
	dev->checkpt_byte_offs = 0;
	dev->checkpt_page_seq++;
	dev->checkpt_cur_chunk++;
	if (dev->checkpt_cur_chunk >= 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);

	return 1;
	}


	int yaffs2_checkpt_wr(yaffs_dev_t dev, const void data, int n_bytes)
	{
	int i = 0;
	int ok = 1;


	__u8 * dataBytes = (__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] = *dataBytes;
	dev->checkpt_sum += *dataBytes;
	dev->checkpt_xor ^= *dataBytes;

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


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

	return i;
	}

	int yaffs2_checkpt_rd(yaffs_dev_t dev, void data, int n_bytes)
	{
	int i = 0;
	int ok = 1;
	yaffs_ext_tags tags;


	int chunk;
	int realignedChunk;

	__u8 dataBytes = (__u8 )data;

	if (!dev->checkpt_buffer)
	return 0;

	if (dev->checkpt_open_write)
	return -1;

	while (i < n_bytes && ok) {


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

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

	if (dev->checkpt_cur_block < 0)
	ok = 0;
	else {
	chunk = dev->checkpt_cur_block *
	dev->param.chunks_per_block +
	dev->checkpt_cur_chunk;

	realignedChunk = chunk - dev->chunk_offset;

	dev->n_page_reads++;

	/* read in the next chunk */
	/* printf("read checkpoint page %d\n",dev->checkpointPage); */
	dev->param.read_chunk_tags_fn(dev,
	realignedChunk,
	dev->checkpt_buffer,
	&tags);

	if (tags.chunk_id != (dev->checkpt_page_seq + 1) \|\|
	tags.ecc_result > YAFFS_ECC_RESULT_FIXED \|\|
	tags.seq_number != YAFFS_SEQUENCE_CHECKPOINT_DATA)
	ok = 0;

	dev->checkpt_byte_offs = 0;
	dev->checkpt_page_seq++;
	dev->checkpt_cur_chunk++;

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

	if (ok) {
	*dataBytes = dev->checkpt_buffer[dev->checkpt_byte_offs];
	dev->checkpt_sum += *dataBytes;
	dev->checkpt_xor ^= *dataBytes;
	dev->checkpt_byte_offs++;
	i++;
	dataBytes++;
	dev->checkpt_byte_count++;
	}
	}

	return i;
	}

	int yaffs_checkpt_close(yaffs_dev_t *dev)
	{

	if (dev->checkpt_open_write) {
	if (dev->checkpt_byte_offs != 0)
	yaffs2_checkpt_flush_buffer(dev);
	} else if(dev->checkpt_block_list){
	int i;
	for (i = 0; i < dev->blocks_in_checkpt && dev->checkpt_block_list[i] >= 0; i++) {
	int blk = dev->checkpt_block_list[i];
	yaffs_block_info_t *bi = NULL;
	if( dev->internal_start_block <= blk && blk <= 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;
	else {
	/* Todo this looks odd... */
	}
	}
	YFREE(dev->checkpt_block_list);
	dev->checkpt_block_list = NULL;
	}

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


	T(YAFFS_TRACE_CHECKPOINT, (TSTR("checkpoint byte count %d" TENDSTR),
	dev->checkpt_byte_count));

	if (dev->checkpt_buffer) {
	/* free the buffer */
	YFREE(dev->checkpt_buffer);
	dev->checkpt_buffer = NULL;
	return 1;
	} else
	return 0;
	}

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

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

	return yaffs_checkpt_erase(dev);
	}