kernel_samsung_msm8974/fs/yaffs2/yaffs_yaffs2.c

/*
 * 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_guts.h"
#include "yaffs_trace.h"
#include "yaffs_yaffs2.h"
#include "yaffs_checkptrw.h"
#include "yaffs_bitmap.h"
#include "yaffs_nand.h"
#include "yaffs_getblockinfo.h"
#include "yaffs_verify.h"
#include "yaffs_attribs.h"

/*
 * Checkpoints are really no benefit on very small partitions.
 *
 * To save space on small partitions don't bother with checkpoints unless
 * the partition is at least this big.
 */
#define YAFFS_CHECKPOINT_MIN_BLOCKS 60

#define YAFFS_SMALL_HOLE_THRESHOLD 4

/*
 * Oldest Dirty Sequence Number handling.
 */

/* yaffs_calc_oldest_dirty_seq()
 * yaffs2_find_oldest_dirty_seq()
 * Calculate the oldest dirty sequence number if we don't know it.
 */
void yaffs_calc_oldest_dirty_seq(struct yaffs_dev *dev)
{
	int i;
	unsigned seq;
	unsigned block_no = 0;
	struct yaffs_block_info *b;

	if (!dev->param.is_yaffs2)
		return;

	/* Find the oldest dirty sequence number. */
	seq = dev->seq_number + 1;
	b = dev->block_info;
	for (i = dev->internal_start_block; i <= dev->internal_end_block; i++) {
		if (b->block_state == YAFFS_BLOCK_STATE_FULL &&
		    (b->pages_in_use - b->soft_del_pages) <
		    dev->param.chunks_per_block && b->seq_number < seq) {
			seq = b->seq_number;
			block_no = i;
		}
		b++;
	}

	if (block_no) {
		dev->oldest_dirty_seq = seq;
		dev->oldest_dirty_block = block_no;
	}

}

void yaffs2_find_oldest_dirty_seq(struct yaffs_dev *dev)
{
	if (!dev->param.is_yaffs2)
		return;

	if (!dev->oldest_dirty_seq)
		yaffs_calc_oldest_dirty_seq(dev);
}

/*
 * yaffs_clear_oldest_dirty_seq()
 * Called when a block is erased or marked bad. (ie. when its seq_number
 * becomes invalid). If the value matches the oldest then we clear 
 * dev->oldest_dirty_seq to force its recomputation.
 */
void yaffs2_clear_oldest_dirty_seq(struct yaffs_dev *dev,
				   struct yaffs_block_info *bi)
{

	if (!dev->param.is_yaffs2)
		return;

	if (!bi || bi->seq_number == dev->oldest_dirty_seq) {
		dev->oldest_dirty_seq = 0;
		dev->oldest_dirty_block = 0;
	}
}

/*
 * yaffs2_update_oldest_dirty_seq()
 * Update the oldest dirty sequence number whenever we dirty a block.
 * Only do this if the oldest_dirty_seq is actually being tracked.
 */
void yaffs2_update_oldest_dirty_seq(struct yaffs_dev *dev, unsigned block_no,
				    struct yaffs_block_info *bi)
{
	if (!dev->param.is_yaffs2)
		return;

	if (dev->oldest_dirty_seq) {
		if (dev->oldest_dirty_seq > bi->seq_number) {
			dev->oldest_dirty_seq = bi->seq_number;
			dev->oldest_dirty_block = block_no;
		}
	}
}

int yaffs_block_ok_for_gc(struct yaffs_dev *dev, struct yaffs_block_info *bi)
{

	if (!dev->param.is_yaffs2)
		return 1;	/* disqualification only applies to yaffs2. */

	if (!bi->has_shrink_hdr)
		return 1;	/* can gc */

	yaffs2_find_oldest_dirty_seq(dev);

	/* Can't do gc of this block if there are any blocks older than this one that have
	 * discarded pages.
	 */
	return (bi->seq_number <= dev->oldest_dirty_seq);
}

/*
 * yaffs2_find_refresh_block()
 * periodically finds the oldest full block by sequence number for refreshing.
 * Only for yaffs2.
 */
u32 yaffs2_find_refresh_block(struct yaffs_dev * dev)
{
	u32 b;

	u32 oldest = 0;
	u32 oldest_seq = 0;

	struct yaffs_block_info *bi;

	if (!dev->param.is_yaffs2)
		return oldest;

	/*
	 * If refresh period < 10 then refreshing is disabled.
	 */
	if (dev->param.refresh_period < 10)
		return oldest;

	/*
	 * Fix broken values.
	 */
	if (dev->refresh_skip > dev->param.refresh_period)
		dev->refresh_skip = dev->param.refresh_period;

	if (dev->refresh_skip > 0)
		return oldest;

	/*
	 * Refresh skip is now zero.
	 * We'll do a refresh this time around....
	 * Update the refresh skip and find the oldest block.
	 */
	dev->refresh_skip = dev->param.refresh_period;
	dev->refresh_count++;
	bi = dev->block_info;
	for (b = dev->internal_start_block; b <= dev->internal_end_block; b++) {

		if (bi->block_state == YAFFS_BLOCK_STATE_FULL) {

			if (oldest < 1 || bi->seq_number < oldest_seq) {
				oldest = b;
				oldest_seq = bi->seq_number;
			}
		}
		bi++;
	}

	if (oldest > 0) {
		yaffs_trace(YAFFS_TRACE_GC,
			"GC refresh count %d selected block %d with seq_number %d",
			dev->refresh_count, oldest, oldest_seq);
	}

	return oldest;
}

int yaffs2_checkpt_required(struct yaffs_dev *dev)
{
	int nblocks;

	if (!dev->param.is_yaffs2)
		return 0;

	nblocks = dev->internal_end_block - dev->internal_start_block + 1;

	return !dev->param.skip_checkpt_wr &&
	    !dev->read_only && (nblocks >= YAFFS_CHECKPOINT_MIN_BLOCKS);
}

int yaffs_calc_checkpt_blocks_required(struct yaffs_dev *dev)
{
	int retval;

	if (!dev->param.is_yaffs2)
		return 0;

	if (!dev->checkpoint_blocks_required && yaffs2_checkpt_required(dev)) {
		/* Not a valid value so recalculate */
		int n_bytes = 0;
		int n_blocks;
		int dev_blocks =
		    (dev->param.end_block - dev->param.start_block + 1);

		n_bytes += sizeof(struct yaffs_checkpt_validity);
		n_bytes += sizeof(struct yaffs_checkpt_dev);
		n_bytes += dev_blocks * sizeof(struct yaffs_block_info);
		n_bytes += dev_blocks * dev->chunk_bit_stride;
		n_bytes +=
		    (sizeof(struct yaffs_checkpt_obj) +
		     sizeof(u32)) * (dev->n_obj);
		n_bytes += (dev->tnode_size + sizeof(u32)) * (dev->n_tnodes);
		n_bytes += sizeof(struct yaffs_checkpt_validity);
		n_bytes += sizeof(u32);	/* checksum */

		/* Round up and add 2 blocks to allow for some bad blocks, so add 3 */

		n_blocks =
		    (n_bytes /
		     (dev->data_bytes_per_chunk *
		      dev->param.chunks_per_block)) + 3;

		dev->checkpoint_blocks_required = n_blocks;
	}

	retval = dev->checkpoint_blocks_required - dev->blocks_in_checkpt;
	if (retval < 0)
		retval = 0;
	return retval;
}

/*--------------------- Checkpointing --------------------*/

static int yaffs2_wr_checkpt_validity_marker(struct yaffs_dev *dev, int head)
{
	struct yaffs_checkpt_validity cp;

	memset(&cp, 0, sizeof(cp));

	cp.struct_type = sizeof(cp);
	cp.magic = YAFFS_MAGIC;
	cp.version = YAFFS_CHECKPOINT_VERSION;
	cp.head = (head) ? 1 : 0;

	return (yaffs2_checkpt_wr(dev, &cp, sizeof(cp)) == sizeof(cp)) ? 1 : 0;
}

static int yaffs2_rd_checkpt_validity_marker(struct yaffs_dev *dev, int head)
{
	struct yaffs_checkpt_validity cp;
	int ok;

	ok = (yaffs2_checkpt_rd(dev, &cp, sizeof(cp)) == sizeof(cp));

	if (ok)
		ok = (cp.struct_type == sizeof(cp)) &&
		    (cp.magic == YAFFS_MAGIC) &&
		    (cp.version == YAFFS_CHECKPOINT_VERSION) &&
		    (cp.head == ((head) ? 1 : 0));
	return ok ? 1 : 0;
}

static void yaffs2_dev_to_checkpt_dev(struct yaffs_checkpt_dev *cp,
				      struct yaffs_dev *dev)
{
	cp->n_erased_blocks = dev->n_erased_blocks;
	cp->alloc_block = dev->alloc_block;
	cp->alloc_page = dev->alloc_page;
	cp->n_free_chunks = dev->n_free_chunks;

	cp->n_deleted_files = dev->n_deleted_files;
	cp->n_unlinked_files = dev->n_unlinked_files;
	cp->n_bg_deletions = dev->n_bg_deletions;
	cp->seq_number = dev->seq_number;

}

static void yaffs_checkpt_dev_to_dev(struct yaffs_dev *dev,
				     struct yaffs_checkpt_dev *cp)
{
	dev->n_erased_blocks = cp->n_erased_blocks;
	dev->alloc_block = cp->alloc_block;
	dev->alloc_page = cp->alloc_page;
	dev->n_free_chunks = cp->n_free_chunks;

	dev->n_deleted_files = cp->n_deleted_files;
	dev->n_unlinked_files = cp->n_unlinked_files;
	dev->n_bg_deletions = cp->n_bg_deletions;
	dev->seq_number = cp->seq_number;
}

static int yaffs2_wr_checkpt_dev(struct yaffs_dev *dev)
{
	struct yaffs_checkpt_dev cp;
	u32 n_bytes;
	u32 n_blocks =
	    (dev->internal_end_block - dev->internal_start_block + 1);

	int ok;

	/* Write device runtime values */
	yaffs2_dev_to_checkpt_dev(&cp, dev);
	cp.struct_type = sizeof(cp);

	ok = (yaffs2_checkpt_wr(dev, &cp, sizeof(cp)) == sizeof(cp));

	/* Write block info */
	if (ok) {
		n_bytes = n_blocks * sizeof(struct yaffs_block_info);
		ok = (yaffs2_checkpt_wr(dev, dev->block_info, n_bytes) ==
		      n_bytes);
	}

	/* Write chunk bits */
	if (ok) {
		n_bytes = n_blocks * dev->chunk_bit_stride;
		ok = (yaffs2_checkpt_wr(dev, dev->chunk_bits, n_bytes) ==
		      n_bytes);
	}
	return ok ? 1 : 0;

}

static int yaffs2_rd_checkpt_dev(struct yaffs_dev *dev)
{
	struct yaffs_checkpt_dev cp;
	u32 n_bytes;
	u32 n_blocks =
	    (dev->internal_end_block - dev->internal_start_block + 1);

	int ok;

	ok = (yaffs2_checkpt_rd(dev, &cp, sizeof(cp)) == sizeof(cp));
	if (!ok)
		return 0;

	if (cp.struct_type != sizeof(cp))
		return 0;

	yaffs_checkpt_dev_to_dev(dev, &cp);

	n_bytes = n_blocks * sizeof(struct yaffs_block_info);

	ok = (yaffs2_checkpt_rd(dev, dev->block_info, n_bytes) == n_bytes);

	if (!ok)
		return 0;
	n_bytes = n_blocks * dev->chunk_bit_stride;

	ok = (yaffs2_checkpt_rd(dev, dev->chunk_bits, n_bytes) == n_bytes);

	return ok ? 1 : 0;
}

static void yaffs2_obj_checkpt_obj(struct yaffs_checkpt_obj *cp,
				   struct yaffs_obj *obj)
{

	cp->obj_id = obj->obj_id;
	cp->parent_id = (obj->parent) ? obj->parent->obj_id : 0;
	cp->hdr_chunk = obj->hdr_chunk;
	cp->variant_type = obj->variant_type;
	cp->deleted = obj->deleted;
	cp->soft_del = obj->soft_del;
	cp->unlinked = obj->unlinked;
	cp->fake = obj->fake;
	cp->rename_allowed = obj->rename_allowed;
	cp->unlink_allowed = obj->unlink_allowed;
	cp->serial = obj->serial;
	cp->n_data_chunks = obj->n_data_chunks;

	if (obj->variant_type == YAFFS_OBJECT_TYPE_FILE)
		cp->size_or_equiv_obj = obj->variant.file_variant.file_size;
	else if (obj->variant_type == YAFFS_OBJECT_TYPE_HARDLINK)
		cp->size_or_equiv_obj = obj->variant.hardlink_variant.equiv_id;
}

static int taffs2_checkpt_obj_to_obj(struct yaffs_obj *obj,
				     struct yaffs_checkpt_obj *cp)
{

	struct yaffs_obj *parent;

	if (obj->variant_type != cp->variant_type) {
		yaffs_trace(YAFFS_TRACE_ERROR,
			"Checkpoint read object %d type %d chunk %d does not match existing object type %d",
			cp->obj_id, cp->variant_type, cp->hdr_chunk,
			obj->variant_type);
		return 0;
	}

	obj->obj_id = cp->obj_id;

	if (cp->parent_id)
		parent = yaffs_find_or_create_by_number(obj->my_dev,
							cp->parent_id,
							YAFFS_OBJECT_TYPE_DIRECTORY);
	else
		parent = NULL;

	if (parent) {
		if (parent->variant_type != YAFFS_OBJECT_TYPE_DIRECTORY) {
			yaffs_trace(YAFFS_TRACE_ALWAYS,
				"Checkpoint read object %d parent %d type %d chunk %d Parent type, %d, not directory",
				cp->obj_id, cp->parent_id,
				cp->variant_type, cp->hdr_chunk,
				parent->variant_type);
			return 0;
		}
		yaffs_add_obj_to_dir(parent, obj);
	}

	obj->hdr_chunk = cp->hdr_chunk;
	obj->variant_type = cp->variant_type;
	obj->deleted = cp->deleted;
	obj->soft_del = cp->soft_del;
	obj->unlinked = cp->unlinked;
	obj->fake = cp->fake;
	obj->rename_allowed = cp->rename_allowed;
	obj->unlink_allowed = cp->unlink_allowed;
	obj->serial = cp->serial;
	obj->n_data_chunks = cp->n_data_chunks;

	if (obj->variant_type == YAFFS_OBJECT_TYPE_FILE)
		obj->variant.file_variant.file_size = cp->size_or_equiv_obj;
	else if (obj->variant_type == YAFFS_OBJECT_TYPE_HARDLINK)
		obj->variant.hardlink_variant.equiv_id = cp->size_or_equiv_obj;

	if (obj->hdr_chunk > 0)
		obj->lazy_loaded = 1;
	return 1;
}

static int yaffs2_checkpt_tnode_worker(struct yaffs_obj *in,
				       struct yaffs_tnode *tn, u32 level,
				       int chunk_offset)
{
	int i;
	struct yaffs_dev *dev = in->my_dev;
	int ok = 1;

	if (tn) {
		if (level > 0) {

			for (i = 0; i < YAFFS_NTNODES_INTERNAL && ok; i++) {
				if (tn->internal[i]) {
					ok = yaffs2_checkpt_tnode_worker(in,
									 tn->
									 internal
									 [i],
									 level -
									 1,
									 (chunk_offset
									  <<
									  YAFFS_TNODES_INTERNAL_BITS)
									 + i);
				}
			}
		} else if (level == 0) {
			u32 base_offset =
			    chunk_offset << YAFFS_TNODES_LEVEL0_BITS;
			ok = (yaffs2_checkpt_wr
			      (dev, &base_offset,
			       sizeof(base_offset)) == sizeof(base_offset));
			if (ok)
				ok = (yaffs2_checkpt_wr
				      (dev, tn,
				       dev->tnode_size) == dev->tnode_size);
		}
	}

	return ok;

}

static int yaffs2_wr_checkpt_tnodes(struct yaffs_obj *obj)
{
	u32 end_marker = ~0;
	int ok = 1;

	if (obj->variant_type == YAFFS_OBJECT_TYPE_FILE) {
		ok = yaffs2_checkpt_tnode_worker(obj,
						 obj->variant.file_variant.top,
						 obj->variant.file_variant.
						 top_level, 0);
		if (ok)
			ok = (yaffs2_checkpt_wr
			      (obj->my_dev, &end_marker,
			       sizeof(end_marker)) == sizeof(end_marker));
	}

	return ok ? 1 : 0;
}

static int yaffs2_rd_checkpt_tnodes(struct yaffs_obj *obj)
{
	u32 base_chunk;
	int ok = 1;
	struct yaffs_dev *dev = obj->my_dev;
	struct yaffs_file_var *file_stuct_ptr = &obj->variant.file_variant;
	struct yaffs_tnode *tn;
	int nread = 0;

	ok = (yaffs2_checkpt_rd(dev, &base_chunk, sizeof(base_chunk)) ==
	      sizeof(base_chunk));

	while (ok && (~base_chunk)) {
		nread++;
		/* Read level 0 tnode */

		tn = yaffs_get_tnode(dev);
		if (tn) {
			ok = (yaffs2_checkpt_rd(dev, tn, dev->tnode_size) ==
			      dev->tnode_size);
		} else {
			ok = 0;
                }

		if (tn && ok)
			ok = yaffs_add_find_tnode_0(dev,
						    file_stuct_ptr,
						    base_chunk, tn) ? 1 : 0;

		if (ok)
			ok = (yaffs2_checkpt_rd
			      (dev, &base_chunk,
			       sizeof(base_chunk)) == sizeof(base_chunk));

	}

	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
		"Checkpoint read tnodes %d records, last %d. ok %d",
		nread, base_chunk, ok);

	return ok ? 1 : 0;
}

static int yaffs2_wr_checkpt_objs(struct yaffs_dev *dev)
{
	struct yaffs_obj *obj;
	struct yaffs_checkpt_obj cp;
	int i;
	int ok = 1;
	struct list_head *lh;

	/* Iterate through the objects in each hash entry,
	 * dumping them to the checkpointing stream.
	 */

	for (i = 0; ok && i < YAFFS_NOBJECT_BUCKETS; i++) {
		list_for_each(lh, &dev->obj_bucket[i].list) {
			if (lh) {
				obj =
				    list_entry(lh, struct yaffs_obj, hash_link);
				if (!obj->defered_free) {
					yaffs2_obj_checkpt_obj(&cp, obj);
					cp.struct_type = sizeof(cp);

					yaffs_trace(YAFFS_TRACE_CHECKPOINT,
						"Checkpoint write object %d parent %d type %d chunk %d obj addr %p",
						cp.obj_id, cp.parent_id,
						cp.variant_type, cp.hdr_chunk, obj);

					ok = (yaffs2_checkpt_wr
					      (dev, &cp,
					       sizeof(cp)) == sizeof(cp));

					if (ok
					    && obj->variant_type ==
					    YAFFS_OBJECT_TYPE_FILE)
						ok = yaffs2_wr_checkpt_tnodes
						    (obj);
				}
			}
		}
	}

	/* Dump end of list */
	memset(&cp, 0xFF, sizeof(struct yaffs_checkpt_obj));
	cp.struct_type = sizeof(cp);

	if (ok)
		ok = (yaffs2_checkpt_wr(dev, &cp, sizeof(cp)) == sizeof(cp));

	return ok ? 1 : 0;
}

static int yaffs2_rd_checkpt_objs(struct yaffs_dev *dev)
{
	struct yaffs_obj *obj;
	struct yaffs_checkpt_obj cp;
	int ok = 1;
	int done = 0;
	struct yaffs_obj *hard_list = NULL;

	while (ok && !done) {
		ok = (yaffs2_checkpt_rd(dev, &cp, sizeof(cp)) == sizeof(cp));
		if (cp.struct_type != sizeof(cp)) {
			yaffs_trace(YAFFS_TRACE_CHECKPOINT,
				"struct size %d instead of %d ok %d",
				cp.struct_type, (int)sizeof(cp), ok);
			ok = 0;
		}

		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"Checkpoint read object %d parent %d type %d chunk %d ",
			cp.obj_id, cp.parent_id, cp.variant_type,
			cp.hdr_chunk);

		if (ok && cp.obj_id == ~0) {
			done = 1;
		} else if (ok) {
			obj =
			    yaffs_find_or_create_by_number(dev, cp.obj_id,
							   cp.variant_type);
			if (obj) {
				ok = taffs2_checkpt_obj_to_obj(obj, &cp);
				if (!ok)
					break;
				if (obj->variant_type == YAFFS_OBJECT_TYPE_FILE) {
					ok = yaffs2_rd_checkpt_tnodes(obj);
				} else if (obj->variant_type ==
					   YAFFS_OBJECT_TYPE_HARDLINK) {
					obj->hard_links.next =
					    (struct list_head *)hard_list;
					hard_list = obj;
				}
			} else {
				ok = 0;
                        }
		}
	}

	if (ok)
		yaffs_link_fixup(dev, hard_list);

	return ok ? 1 : 0;
}

static int yaffs2_wr_checkpt_sum(struct yaffs_dev *dev)
{
	u32 checkpt_sum;
	int ok;

	yaffs2_get_checkpt_sum(dev, &checkpt_sum);

	ok = (yaffs2_checkpt_wr(dev, &checkpt_sum, sizeof(checkpt_sum)) ==
	      sizeof(checkpt_sum));

	if (!ok)
		return 0;

	return 1;
}

static int yaffs2_rd_checkpt_sum(struct yaffs_dev *dev)
{
	u32 checkpt_sum0;
	u32 checkpt_sum1;
	int ok;

	yaffs2_get_checkpt_sum(dev, &checkpt_sum0);

	ok = (yaffs2_checkpt_rd(dev, &checkpt_sum1, sizeof(checkpt_sum1)) ==
	      sizeof(checkpt_sum1));

	if (!ok)
		return 0;

	if (checkpt_sum0 != checkpt_sum1)
		return 0;

	return 1;
}

static int yaffs2_wr_checkpt_data(struct yaffs_dev *dev)
{
	int ok = 1;

	if (!yaffs2_checkpt_required(dev)) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"skipping checkpoint write");
		ok = 0;
	}

	if (ok)
		ok = yaffs2_checkpt_open(dev, 1);

	if (ok) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"write checkpoint validity");
		ok = yaffs2_wr_checkpt_validity_marker(dev, 1);
	}
	if (ok) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"write checkpoint device");
		ok = yaffs2_wr_checkpt_dev(dev);
	}
	if (ok) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"write checkpoint objects");
		ok = yaffs2_wr_checkpt_objs(dev);
	}
	if (ok) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"write checkpoint validity");
		ok = yaffs2_wr_checkpt_validity_marker(dev, 0);
	}

	if (ok)
		ok = yaffs2_wr_checkpt_sum(dev);

	if (!yaffs_checkpt_close(dev))
		ok = 0;

	if (ok)
		dev->is_checkpointed = 1;
	else
		dev->is_checkpointed = 0;

	return dev->is_checkpointed;
}

static int yaffs2_rd_checkpt_data(struct yaffs_dev *dev)
{
	int ok = 1;

	if (!dev->param.is_yaffs2)
		ok = 0;

	if (ok && dev->param.skip_checkpt_rd) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"skipping checkpoint read");
		ok = 0;
	}

	if (ok)
		ok = yaffs2_checkpt_open(dev, 0); /* open for read */

	if (ok) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"read checkpoint validity");
		ok = yaffs2_rd_checkpt_validity_marker(dev, 1);
	}
	if (ok) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"read checkpoint device");
		ok = yaffs2_rd_checkpt_dev(dev);
	}
	if (ok) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"read checkpoint objects");
		ok = yaffs2_rd_checkpt_objs(dev);
	}
	if (ok) {
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"read checkpoint validity");
		ok = yaffs2_rd_checkpt_validity_marker(dev, 0);
	}

	if (ok) {
		ok = yaffs2_rd_checkpt_sum(dev);
		yaffs_trace(YAFFS_TRACE_CHECKPOINT,
			"read checkpoint checksum %d", ok);
	}

	if (!yaffs_checkpt_close(dev))
		ok = 0;

	if (ok)
		dev->is_checkpointed = 1;
	else
		dev->is_checkpointed = 0;

	return ok ? 1 : 0;

}

void yaffs2_checkpt_invalidate(struct yaffs_dev *dev)
{
	if (dev->is_checkpointed || dev->blocks_in_checkpt > 0) {
		dev->is_checkpointed = 0;
		yaffs2_checkpt_invalidate_stream(dev);
	}
	if (dev->param.sb_dirty_fn)
		dev->param.sb_dirty_fn(dev);
}

int yaffs_checkpoint_save(struct yaffs_dev *dev)
{

	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
		"save entry: is_checkpointed %d",
		dev->is_checkpointed);

	yaffs_verify_objects(dev);
	yaffs_verify_blocks(dev);
	yaffs_verify_free_chunks(dev);

	if (!dev->is_checkpointed) {
		yaffs2_checkpt_invalidate(dev);
		yaffs2_wr_checkpt_data(dev);
	}

	yaffs_trace(YAFFS_TRACE_CHECKPOINT | YAFFS_TRACE_MOUNT,
		"save exit: is_checkpointed %d",
		dev->is_checkpointed);

	return dev->is_checkpointed;
}

int yaffs2_checkpt_restore(struct yaffs_dev *dev)
{
	int retval;
	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
		"restore entry: is_checkpointed %d",
		dev->is_checkpointed);

	retval = yaffs2_rd_checkpt_data(dev);

	if (dev->is_checkpointed) {
		yaffs_verify_objects(dev);
		yaffs_verify_blocks(dev);
		yaffs_verify_free_chunks(dev);
	}

	yaffs_trace(YAFFS_TRACE_CHECKPOINT,
		"restore exit: is_checkpointed %d",
		dev->is_checkpointed);

	return retval;
}

int yaffs2_handle_hole(struct yaffs_obj *obj, loff_t new_size)
{
	/* if new_size > old_file_size.
	 * We're going to be writing a hole.
	 * If the hole is small then write zeros otherwise write a start of hole marker.
	 */

	loff_t old_file_size;
	int increase;
	int small_hole;
	int result = YAFFS_OK;
	struct yaffs_dev *dev = NULL;

	u8 *local_buffer = NULL;

	int small_increase_ok = 0;

	if (!obj)
		return YAFFS_FAIL;

	if (obj->variant_type != YAFFS_OBJECT_TYPE_FILE)
		return YAFFS_FAIL;

	dev = obj->my_dev;

	/* Bail out if not yaffs2 mode */
	if (!dev->param.is_yaffs2)
		return YAFFS_OK;

	old_file_size = obj->variant.file_variant.file_size;

	if (new_size <= old_file_size)
		return YAFFS_OK;

	increase = new_size - old_file_size;

	if (increase < YAFFS_SMALL_HOLE_THRESHOLD * dev->data_bytes_per_chunk &&
	    yaffs_check_alloc_available(dev, YAFFS_SMALL_HOLE_THRESHOLD + 1))
		small_hole = 1;
	else
		small_hole = 0;

	if (small_hole)
		local_buffer = yaffs_get_temp_buffer(dev, __LINE__);

	if (local_buffer) {
		/* fill hole with zero bytes */
		int pos = old_file_size;
		int this_write;
		int written;
		memset(local_buffer, 0, dev->data_bytes_per_chunk);
		small_increase_ok = 1;

		while (increase > 0 && small_increase_ok) {
			this_write = increase;
			if (this_write > dev->data_bytes_per_chunk)
				this_write = dev->data_bytes_per_chunk;
			written =
			    yaffs_do_file_wr(obj, local_buffer, pos, this_write,
					     0);
			if (written == this_write) {
				pos += this_write;
				increase -= this_write;
			} else {
				small_increase_ok = 0;
                        }
		}

		yaffs_release_temp_buffer(dev, local_buffer, __LINE__);

		/* If we were out of space then reverse any chunks we've added */
		if (!small_increase_ok)
			yaffs_resize_file_down(obj, old_file_size);
	}

	if (!small_increase_ok &&
	    obj->parent &&
	    obj->parent->obj_id != YAFFS_OBJECTID_UNLINKED &&
	    obj->parent->obj_id != YAFFS_OBJECTID_DELETED) {
		/* Write a hole start header with the old file size */
		yaffs_update_oh(obj, NULL, 0, 1, 0, NULL);
	}

	return result;

}

struct yaffs_block_index {
	int seq;
	int block;
};

static int yaffs2_ybicmp(const void *a, const void *b)
{
	int aseq = ((struct yaffs_block_index *)a)->seq;
	int bseq = ((struct yaffs_block_index *)b)->seq;
	int ablock = ((struct yaffs_block_index *)a)->block;
	int bblock = ((struct yaffs_block_index *)b)->block;
	if (aseq == bseq)
		return ablock - bblock;
	else
		return aseq - bseq;
}

int yaffs2_scan_backwards(struct yaffs_dev *dev)
{
	struct yaffs_ext_tags tags;
	int blk;
	int block_iter;
	int start_iter;
	int end_iter;
	int n_to_scan = 0;

	int chunk;
	int result;
	int c;
	int deleted;
	enum yaffs_block_state state;
	struct yaffs_obj *hard_list = NULL;
	struct yaffs_block_info *bi;
	u32 seq_number;
	struct yaffs_obj_hdr *oh;
	struct yaffs_obj *in;
	struct yaffs_obj *parent;
	int n_blocks = dev->internal_end_block - dev->internal_start_block + 1;
	int is_unlinked;
	u8 *chunk_data;

	int file_size;
	int is_shrink;
	int found_chunks;
	int equiv_id;
	int alloc_failed = 0;

	struct yaffs_block_index *block_index = NULL;
	int alt_block_index = 0;

	yaffs_trace(YAFFS_TRACE_SCAN,
		"yaffs2_scan_backwards starts  intstartblk %d intendblk %d...",
		dev->internal_start_block, dev->internal_end_block);

	dev->seq_number = YAFFS_LOWEST_SEQUENCE_NUMBER;

	block_index = kmalloc(n_blocks * sizeof(struct yaffs_block_index),
			GFP_NOFS);

	if (!block_index) {
		block_index =
		    vmalloc(n_blocks * sizeof(struct yaffs_block_index));
		alt_block_index = 1;
	}

	if (!block_index) {
		yaffs_trace(YAFFS_TRACE_SCAN,
			"yaffs2_scan_backwards() could not allocate block index!"
			);
		return YAFFS_FAIL;
	}

	dev->blocks_in_checkpt = 0;

	chunk_data = yaffs_get_temp_buffer(dev, __LINE__);

	/* Scan all the blocks to determine their state */
	bi = dev->block_info;
	for (blk = dev->internal_start_block; blk <= dev->internal_end_block;
	     blk++) {
		yaffs_clear_chunk_bits(dev, blk);
		bi->pages_in_use = 0;
		bi->soft_del_pages = 0;

		yaffs_query_init_block_state(dev, blk, &state, &seq_number);

		bi->block_state = state;
		bi->seq_number = seq_number;

		if (bi->seq_number == YAFFS_SEQUENCE_CHECKPOINT_DATA)
			bi->block_state = state = YAFFS_BLOCK_STATE_CHECKPOINT;
		if (bi->seq_number == YAFFS_SEQUENCE_BAD_BLOCK)
			bi->block_state = state = YAFFS_BLOCK_STATE_DEAD;

		yaffs_trace(YAFFS_TRACE_SCAN_DEBUG,
			"Block scanning block %d state %d seq %d",
			blk, state, seq_number);

		if (state == YAFFS_BLOCK_STATE_CHECKPOINT) {
			dev->blocks_in_checkpt++;

		} else if (state == YAFFS_BLOCK_STATE_DEAD) {
			yaffs_trace(YAFFS_TRACE_BAD_BLOCKS,
				"block %d is bad", blk);
		} else if (state == YAFFS_BLOCK_STATE_EMPTY) {
			yaffs_trace(YAFFS_TRACE_SCAN_DEBUG, "Block empty ");
			dev->n_erased_blocks++;
			dev->n_free_chunks += dev->param.chunks_per_block;
		} else if (state == YAFFS_BLOCK_STATE_NEEDS_SCANNING) {

			/* Determine the highest sequence number */
			if (seq_number >= YAFFS_LOWEST_SEQUENCE_NUMBER &&
			    seq_number < YAFFS_HIGHEST_SEQUENCE_NUMBER) {

				block_index[n_to_scan].seq = seq_number;
				block_index[n_to_scan].block = blk;

				n_to_scan++;

				if (seq_number >= dev->seq_number)
					dev->seq_number = seq_number;
			} else {
				/* TODO: Nasty sequence number! */
				yaffs_trace(YAFFS_TRACE_SCAN,
					"Block scanning block %d has bad sequence number %d",
					blk, seq_number);

			}
		}
		bi++;
	}

	yaffs_trace(YAFFS_TRACE_SCAN, "%d blocks to be sorted...", n_to_scan);

	cond_resched();

	/* Sort the blocks by sequence number */
	sort(block_index, n_to_scan, sizeof(struct yaffs_block_index),
		   yaffs2_ybicmp, NULL);

	cond_resched();

	yaffs_trace(YAFFS_TRACE_SCAN, "...done");

	/* Now scan the blocks looking at the data. */
	start_iter = 0;
	end_iter = n_to_scan - 1;
	yaffs_trace(YAFFS_TRACE_SCAN_DEBUG, "%d blocks to scan", n_to_scan);

	/* For each block.... backwards */
	for (block_iter = end_iter; !alloc_failed && block_iter >= start_iter;
	     block_iter--) {
		/* Cooperative multitasking! This loop can run for so
		   long that watchdog timers expire. */
		cond_resched();

		/* get the block to scan in the correct order */
		blk = block_index[block_iter].block;

		bi = yaffs_get_block_info(dev, blk);

		state = bi->block_state;

		deleted = 0;

		/* For each chunk in each block that needs scanning.... */
		found_chunks = 0;
		for (c = dev->param.chunks_per_block - 1;
		     !alloc_failed && c >= 0 &&
		     (state == YAFFS_BLOCK_STATE_NEEDS_SCANNING ||
		      state == YAFFS_BLOCK_STATE_ALLOCATING); c--) {
			/* Scan backwards...
			 * Read the tags and decide what to do
			 */

			chunk = blk * dev->param.chunks_per_block + c;

			result = yaffs_rd_chunk_tags_nand(dev, chunk, NULL,
							  &tags);

			/* Let's have a good look at this chunk... */

			if (!tags.chunk_used) {
				/* An unassigned chunk in the block.
				 * If there are used chunks after this one, then
				 * it is a chunk that was skipped due to failing the erased
				 * check. Just skip it so that it can be deleted.
				 * But, more typically, We get here when this is an unallocated
				 * chunk and his means that either the block is empty or
				 * this is the one being allocated from
				 */

				if (found_chunks) {
					/* This is a chunk that was skipped due to failing the erased check */
				} else if (c == 0) {
					/* We're looking at the first chunk in the block so the block is unused */
					state = YAFFS_BLOCK_STATE_EMPTY;
					dev->n_erased_blocks++;
				} else {
					if (state ==
					    YAFFS_BLOCK_STATE_NEEDS_SCANNING
					    || state ==
					    YAFFS_BLOCK_STATE_ALLOCATING) {
						if (dev->seq_number ==
						    bi->seq_number) {
							/* this is the block being allocated from */

							yaffs_trace(YAFFS_TRACE_SCAN,
								" Allocating from %d %d",
								blk, c);

							state =
							    YAFFS_BLOCK_STATE_ALLOCATING;
							dev->alloc_block = blk;
							dev->alloc_page = c;
							dev->
							    alloc_block_finder =
							    blk;
						} else {
							/* This is a partially written block that is not
							 * the current allocation block.
							 */

							yaffs_trace(YAFFS_TRACE_SCAN,
								"Partially written block %d detected",
								blk);
						}
					}
				}

				dev->n_free_chunks++;

			} else if (tags.ecc_result == YAFFS_ECC_RESULT_UNFIXED) {
				yaffs_trace(YAFFS_TRACE_SCAN,
					" Unfixed ECC in chunk(%d:%d), chunk ignored",
					blk, c);

				dev->n_free_chunks++;

			} else if (tags.obj_id > YAFFS_MAX_OBJECT_ID ||
				   tags.chunk_id > YAFFS_MAX_CHUNK_ID ||
				   (tags.chunk_id > 0
				    && tags.n_bytes > dev->data_bytes_per_chunk)
				   || tags.seq_number != bi->seq_number) {
				yaffs_trace(YAFFS_TRACE_SCAN,
					"Chunk (%d:%d) with bad tags:obj = %d, chunk_id = %d, n_bytes = %d, ignored",
					blk, c, tags.obj_id,
					tags.chunk_id, tags.n_bytes);

				dev->n_free_chunks++;

			} else if (tags.chunk_id > 0) {
				/* chunk_id > 0 so it is a data chunk... */
				unsigned int endpos;
				u32 chunk_base =
				    (tags.chunk_id -
				     1) * dev->data_bytes_per_chunk;

				found_chunks = 1;

				yaffs_set_chunk_bit(dev, blk, c);
				bi->pages_in_use++;

				in = yaffs_find_or_create_by_number(dev,
								    tags.obj_id,
								    YAFFS_OBJECT_TYPE_FILE);
				if (!in) {
					/* Out of memory */
					alloc_failed = 1;
				}

				if (in &&
				    in->variant_type == YAFFS_OBJECT_TYPE_FILE
				    && chunk_base <
				    in->variant.file_variant.shrink_size) {
					/* This has not been invalidated by a resize */
					if (!yaffs_put_chunk_in_file
					    (in, tags.chunk_id, chunk, -1)) {
						alloc_failed = 1;
					}

					/* File size is calculated by looking at the data chunks if we have not
					 * seen an object header yet. Stop this practice once we find an object header.
					 */
					endpos = chunk_base + tags.n_bytes;

					if (!in->valid &&	/* have not got an object header yet */
					    in->variant.file_variant.
					    scanned_size < endpos) {
						in->variant.file_variant.
						    scanned_size = endpos;
						in->variant.file_variant.
						    file_size = endpos;
					}

				} else if (in) {
					/* This chunk has been invalidated by a resize, or a past file deletion
					 * so delete the chunk*/
					yaffs_chunk_del(dev, chunk, 1,
							__LINE__);

				}
			} else {
				/* chunk_id == 0, so it is an ObjectHeader.
				 * Thus, we read in the object header and make the object
				 */
				found_chunks = 1;

				yaffs_set_chunk_bit(dev, blk, c);
				bi->pages_in_use++;

				oh = NULL;
				in = NULL;

				if (tags.extra_available) {
					in = yaffs_find_or_create_by_number(dev,
									    tags.
									    obj_id,
									    tags.
									    extra_obj_type);
					if (!in)
						alloc_failed = 1;
				}

				if (!in ||
				    (!in->valid && dev->param.disable_lazy_load)
				    || tags.extra_shadows || (!in->valid
							      && (tags.obj_id ==
								  YAFFS_OBJECTID_ROOT
								  || tags.
								  obj_id ==
								  YAFFS_OBJECTID_LOSTNFOUND)))
				{

					/* If we don't have  valid info then we need to read the chunk
					 * TODO In future we can probably defer reading the chunk and
					 * living with invalid data until needed.
					 */

					result = yaffs_rd_chunk_tags_nand(dev,
									  chunk,
									  chunk_data,
									  NULL);

					oh = (struct yaffs_obj_hdr *)chunk_data;

					if (dev->param.inband_tags) {
						/* Fix up the header if they got corrupted by inband tags */
						oh->shadows_obj =
						    oh->inband_shadowed_obj_id;
						oh->is_shrink =
						    oh->inband_is_shrink;
					}

					if (!in) {
						in = yaffs_find_or_create_by_number(dev, tags.obj_id, oh->type);
						if (!in)
							alloc_failed = 1;
					}

				}

				if (!in) {
					/* TODO Hoosterman we have a problem! */
					yaffs_trace(YAFFS_TRACE_ERROR,
						"yaffs tragedy: Could not make object for object  %d at chunk %d during scan",
						tags.obj_id, chunk);
					continue;
				}

				if (in->valid) {
					/* We have already filled this one.
					 * We have a duplicate that will be discarded, but
					 * we first have to suck out resize info if it is a file.
					 */

					if ((in->variant_type ==
					     YAFFS_OBJECT_TYPE_FILE) && ((oh
									  &&
									  oh->
									  type
									  ==
									  YAFFS_OBJECT_TYPE_FILE)
									 ||
									 (tags.
									  extra_available
									  &&
									  tags.
									  extra_obj_type
									  ==
									  YAFFS_OBJECT_TYPE_FILE)))
					{
						u32 this_size =
						    (oh) ? oh->
						    file_size :
						    tags.extra_length;
						u32 parent_obj_id =
						    (oh) ? oh->parent_obj_id :
						    tags.extra_parent_id;

						is_shrink =
						    (oh) ? oh->
						    is_shrink :
						    tags.extra_is_shrink;

						/* If it is deleted (unlinked at start also means deleted)
						 * we treat the file size as being zeroed at this point.
						 */
						if (parent_obj_id ==
						    YAFFS_OBJECTID_DELETED
						    || parent_obj_id ==
						    YAFFS_OBJECTID_UNLINKED) {
							this_size = 0;
							is_shrink = 1;
						}

						if (is_shrink
						    && in->variant.file_variant.
						    shrink_size > this_size)
							in->variant.
							    file_variant.
							    shrink_size =
							    this_size;

						if (is_shrink)
							bi->has_shrink_hdr = 1;

					}
					/* Use existing - destroy this one. */
					yaffs_chunk_del(dev, chunk, 1,
							__LINE__);

				}

				if (!in->valid && in->variant_type !=
				    (oh ? oh->type : tags.extra_obj_type))
					yaffs_trace(YAFFS_TRACE_ERROR,
						"yaffs tragedy: Bad object type, %d != %d, for object %d at chunk %d during scan",
						oh ?
						oh->type : tags.extra_obj_type,
						in->variant_type, tags.obj_id,
						chunk);

				if (!in->valid &&
				    (tags.obj_id == YAFFS_OBJECTID_ROOT ||
				     tags.obj_id ==
				     YAFFS_OBJECTID_LOSTNFOUND)) {
					/* We only load some info, don't fiddle with directory structure */
					in->valid = 1;

					if (oh) {

						in->yst_mode = oh->yst_mode;
						yaffs_load_attribs(in, oh);
						in->lazy_loaded = 0;
					} else {
						in->lazy_loaded = 1;
                                        }
					in->hdr_chunk = chunk;

				} else if (!in->valid) {
					/* we need to load this info */

					in->valid = 1;
					in->hdr_chunk = chunk;

					if (oh) {
						in->variant_type = oh->type;

						in->yst_mode = oh->yst_mode;
						yaffs_load_attribs(in, oh);

						if (oh->shadows_obj > 0)
							yaffs_handle_shadowed_obj
							    (dev,
							     oh->shadows_obj,
							     1);

						yaffs_set_obj_name_from_oh(in,
									   oh);
						parent =
						    yaffs_find_or_create_by_number
						    (dev, oh->parent_obj_id,
						     YAFFS_OBJECT_TYPE_DIRECTORY);

						file_size = oh->file_size;
						is_shrink = oh->is_shrink;
						equiv_id = oh->equiv_id;

					} else {
						in->variant_type =
						    tags.extra_obj_type;
						parent =
						    yaffs_find_or_create_by_number
						    (dev, tags.extra_parent_id,
						     YAFFS_OBJECT_TYPE_DIRECTORY);
						file_size = tags.extra_length;
						is_shrink =
						    tags.extra_is_shrink;
						equiv_id = tags.extra_equiv_id;
						in->lazy_loaded = 1;

					}
					in->dirty = 0;

					if (!parent)
						alloc_failed = 1;

					/* directory stuff...
					 * hook up to parent
					 */

					if (parent && parent->variant_type ==
					    YAFFS_OBJECT_TYPE_UNKNOWN) {
						/* Set up as a directory */
						parent->variant_type =
						    YAFFS_OBJECT_TYPE_DIRECTORY;
						INIT_LIST_HEAD(&parent->
							       variant.dir_variant.children);
					} else if (!parent
						   || parent->variant_type !=
						   YAFFS_OBJECT_TYPE_DIRECTORY) {
						/* Hoosterman, another problem....
						 * We're trying to use a non-directory as a directory
						 */

						yaffs_trace(YAFFS_TRACE_ERROR,
							"yaffs tragedy: attempting to use non-directory as a directory in scan. Put in lost+found."
							);
						parent = dev->lost_n_found;
					}

					yaffs_add_obj_to_dir(parent, in);

					is_unlinked = (parent == dev->del_dir)
					    || (parent == dev->unlinked_dir);

					if (is_shrink) {
						/* Mark the block as having a shrink header */
						bi->has_shrink_hdr = 1;
					}

					/* Note re hardlinks.
					 * Since we might scan a hardlink before its equivalent object is scanned
					 * we put them all in a list.
					 * After scanning is complete, we should have all the objects, so we run
					 * through this list and fix up all the chains.
					 */

					switch (in->variant_type) {
					case YAFFS_OBJECT_TYPE_UNKNOWN:
						/* Todo got a problem */
						break;
					case YAFFS_OBJECT_TYPE_FILE:

						if (in->variant.
						    file_variant.scanned_size <
						    file_size) {
							/* This covers the case where the file size is greater
							 * than where the data is
							 * This will happen if the file is resized to be larger
							 * than its current data extents.
							 */
							in->variant.
							    file_variant.
							    file_size =
							    file_size;
							in->variant.
							    file_variant.
							    scanned_size =
							    file_size;
						}

						if (in->variant.file_variant.
						    shrink_size > file_size)
							in->variant.
							    file_variant.
							    shrink_size =
							    file_size;

						break;
					case YAFFS_OBJECT_TYPE_HARDLINK:
						if (!is_unlinked) {
							in->variant.
							    hardlink_variant.
							    equiv_id = equiv_id;
							in->hard_links.next =
							    (struct list_head *)
							    hard_list;
							hard_list = in;
						}
						break;
					case YAFFS_OBJECT_TYPE_DIRECTORY:
						/* Do nothing */
						break;
					case YAFFS_OBJECT_TYPE_SPECIAL:
						/* Do nothing */
						break;
					case YAFFS_OBJECT_TYPE_SYMLINK:
						if (oh) {
							in->variant.
							    symlink_variant.
							    alias =
							    yaffs_clone_str(oh->
									    alias);
							if (!in->variant.
							    symlink_variant.
							    alias)
								alloc_failed =
								    1;
						}
						break;
					}

				}

			}

		}		/* End of scanning for each chunk */

		if (state == YAFFS_BLOCK_STATE_NEEDS_SCANNING) {
			/* If we got this far while scanning, then the block is fully allocated. */
			state = YAFFS_BLOCK_STATE_FULL;
		}

		bi->block_state = state;

		/* Now let's see if it was dirty */
		if (bi->pages_in_use == 0 &&
		    !bi->has_shrink_hdr &&
		    bi->block_state == YAFFS_BLOCK_STATE_FULL) {
			yaffs_block_became_dirty(dev, blk);
		}

	}

	yaffs_skip_rest_of_block(dev);

	if (alt_block_index)
		vfree(block_index);
	else
		kfree(block_index);

	/* Ok, we've done all the scanning.
	 * Fix up the hard link chains.
	 * We should now have scanned all the objects, now it's time to add these
	 * hardlinks.
	 */
	yaffs_link_fixup(dev, hard_list);

	yaffs_release_temp_buffer(dev, chunk_data, __LINE__);

	if (alloc_failed)
		return YAFFS_FAIL;

	yaffs_trace(YAFFS_TRACE_SCAN, "yaffs2_scan_backwards ends");

	return YAFFS_OK;
}