text: /*
   * kernel/power/tuxonice_bio_devinfo.c
   *
   * Copyright (C) 2009-2010 Nigel Cunningham (nigel at tuxonice net)
   *
   * Distributed under GPLv2.
   *
   */
  
  #include <linux/mm_types.h>
  #include "tuxonice_bio.h"
  #include "tuxonice_bio_internal.h"
  #include "tuxonice_alloc.h"
  #include "tuxonice_ui.h"
  #include "tuxonice.h"
  #include "tuxonice_io.h"
  
  static struct toi_bdev_info *prio_chain_head;
  static int num_chains;
  
  /* Pointer to current entry being loaded/saved. */
  struct toi_extent_iterate_state toi_writer_posn;
  
  #define metadata_size (sizeof(struct toi_bdev_info) - \
  		offsetof(struct toi_bdev_info, uuid))
  
  /*
   * After section 0 (header) comes 2 => next_section[0] = 2
   */
  static int next_section[3] = { 2, 3, 1 };
  
  /**
   * dump_block_chains - print the contents of the bdev info array.
   **/
  void dump_block_chains(void)
  {
  	int i = 0;
  	int j;
  	struct toi_bdev_info *cur_chain = prio_chain_head;
  
  	while (cur_chain) {
  		struct hibernate_extent *this = cur_chain->blocks.first;
  
  		printk(KERN_DEBUG "Chain %d (prio %d):", i, cur_chain->prio);
  
  		while (this) {
  			printk(KERN_CONT " [%lu-%lu]%s", this->start,
  			       this->end, this->next ? "," : "");
  			this = this->next;
  		}
  
  		printk("\n");
  		cur_chain = cur_chain->next;
  		i++;
  	}
  
  	printk(KERN_DEBUG "Saved states:\n");
  	for (i = 0; i < 4; i++) {
  		printk(KERN_DEBUG "Slot %d: Chain %d.\n", i, toi_writer_posn.saved_chain_number[i]);
  
  		cur_chain = prio_chain_head;
  		j = 0;
  		while (cur_chain) {
  			printk(KERN_DEBUG " Chain %d: Extent %d. Offset %lu.\n",
  			       j, cur_chain->saved_state[i].extent_num,
  			       cur_chain->saved_state[i].offset);
  			cur_chain = cur_chain->next;
  			j++;
  		}
  		printk(KERN_CONT "\n");
  	}
  }
  
  /**
   *
   **/
  static void toi_extent_chain_next(void)
  {
  	struct toi_bdev_info *this = toi_writer_posn.current_chain;
  
  	if (!this->blocks.current_extent)
  		return;
  
  	if (this->blocks.current_offset == this->blocks.current_extent->end) {
  		if (this->blocks.current_extent->next) {
  			this->blocks.current_extent = this->blocks.current_extent->next;
  			this->blocks.current_offset = this->blocks.current_extent->start;
  		} else {
  			this->blocks.current_extent = NULL;
  			this->blocks.current_offset = 0;
  		}
  	} else
  		this->blocks.current_offset++;
  }
  
  /**
   *
   */
  
  static struct toi_bdev_info *__find_next_chain_same_prio(void)
  {
  	struct toi_bdev_info *start_chain = toi_writer_posn.current_chain;
  	struct toi_bdev_info *this = start_chain;
  	int orig_prio = this->prio;
  
  	do {
  		this = this->next;
  
  		if (!this)
  			this = prio_chain_head;
  
  		/* Back on original chain? Use it again. */
  		if (this == start_chain)
  			return start_chain;
  
  	} while (!this->blocks.current_extent || this->prio != orig_prio);
  
  	return this;
  }
  
  static void find_next_chain(void)
  {
  	struct toi_bdev_info *this;
  
  	this = __find_next_chain_same_prio();
  
  	/*
  	 * If we didn't get another chain of the same priority that we
  	 * can use, look for the next priority.
  	 */
  	while (this && !this->blocks.current_extent)
  		this = this->next;
  
  	toi_writer_posn.current_chain = this;
  }
  
  /**
   * toi_extent_state_next - go to the next extent
   * @blocks: The number of values to progress.
   * @stripe_mode: Whether to spread usage across all chains.
   *
   * Given a state, progress to the next valid entry. We may begin in an
   * invalid state, as we do when invoked after extent_state_goto_start below.
   *
   * When using compression and expected_compression > 0, we let the image size
   * be larger than storage, so we can validly run out of data to return.
   **/
  static unsigned long toi_extent_state_next(int blocks, int current_stream)
  {
  	int i;
  
  	if (!toi_writer_posn.current_chain)
  		return -ENOSPC;
  
  	/* Assume chains always have lengths that are multiples of @blocks */
  	for (i = 0; i < blocks; i++)
  		toi_extent_chain_next();
  
  	/* The header stream is not striped */
  	if (current_stream || !toi_writer_posn.current_chain->blocks.current_extent)
  		find_next_chain();
  
  	return toi_writer_posn.current_chain ? 0 : -ENOSPC;
  }
  
  static void toi_insert_chain_in_prio_list(struct toi_bdev_info *this)
  {
  	struct toi_bdev_info **prev_ptr;
  	struct toi_bdev_info *cur;
  
  	/* Loop through the existing chain, finding where to insert it */
  	prev_ptr = &prio_chain_head;
  	cur = prio_chain_head;
  
  	while (cur && cur->prio >= this->prio) {
  		prev_ptr = &cur->next;
  		cur = cur->next;
  	}
  
  	this->next = *prev_ptr;
  	*prev_ptr = this;
  
  	this = prio_chain_head;
  	while (this)
  		this = this->next;
  	num_chains++;
  }
  
  /**
   * toi_extent_state_goto_start - reinitialize an extent chain iterator
   * @state:	Iterator to reinitialize
   **/
  void toi_extent_state_goto_start(void)
  {
  	struct toi_bdev_info *this = prio_chain_head;
  
  	while (this) {
  		toi_message(TOI_BIO, TOI_VERBOSE, 0,
  			    "Setting current extent to %p.", this->blocks.first);
  		this->blocks.current_extent = this->blocks.first;
  		if (this->blocks.current_extent) {
  			toi_message(TOI_BIO, TOI_VERBOSE, 0,
  				    "Setting current offset to %lu.",
  				    this->blocks.current_extent->start);
  			this->blocks.current_offset = this->blocks.current_extent->start;
  		}
  
  		this = this->next;
  	}
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Setting current chain to %p.", prio_chain_head);
  	toi_writer_posn.current_chain = prio_chain_head;
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Leaving extent state goto start.");
  }
  
  /**
   * toi_extent_state_save - save state of the iterator
   * @state:		Current state of the chain
   * @saved_state:	Iterator to populate
   *
   * Given a state and a struct hibernate_extent_state_store, save the current
   * position in a format that can be used with relocated chains (at
   * resume time).
   **/
  void toi_extent_state_save(int slot)
  {
  	struct toi_bdev_info *cur_chain = prio_chain_head;
  	struct hibernate_extent *extent;
  	struct hibernate_extent_saved_state *chain_state;
  	int i = 0;
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "toi_extent_state_save, slot %d.", slot);
  
  	if (!toi_writer_posn.current_chain) {
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, "No current chain => " "chain_num = -1.");
  		toi_writer_posn.saved_chain_number[slot] = -1;
  		return;
  	}
  
  	while (cur_chain) {
  		i++;
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, "Saving chain %d (%p) "
  			    "state, slot %d.", i, cur_chain, slot);
  
  		chain_state = &cur_chain->saved_state[slot];
  
  		chain_state->offset = cur_chain->blocks.current_offset;
  
  		if (toi_writer_posn.current_chain == cur_chain) {
  			toi_writer_posn.saved_chain_number[slot] = i;
  			toi_message(TOI_BIO, TOI_VERBOSE, 0, "This is the chain "
  				    "we were on => chain_num is %d.", i);
  		}
  
  		if (!cur_chain->blocks.current_extent) {
  			chain_state->extent_num = 0;
  			toi_message(TOI_BIO, TOI_VERBOSE, 0, "No current extent "
  				    "for this chain => extent_num %d is 0.", i);
  			cur_chain = cur_chain->next;
  			continue;
  		}
  
  		extent = cur_chain->blocks.first;
  		chain_state->extent_num = 1;
  
  		while (extent != cur_chain->blocks.current_extent) {
  			chain_state->extent_num++;
  			extent = extent->next;
  		}
  
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, "extent num %d is %d.", i,
  			    chain_state->extent_num);
  
  		cur_chain = cur_chain->next;
  	}
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Completed saving extent state slot %d.", slot);
  }
  
  /**
   * toi_extent_state_restore - restore the position saved by extent_state_save
   * @state:		State to populate
   * @saved_state:	Iterator saved to restore
   **/
  void toi_extent_state_restore(int slot)
  {
  	int i = 0;
  	struct toi_bdev_info *cur_chain = prio_chain_head;
  	struct hibernate_extent_saved_state *chain_state;
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "toi_extent_state_restore - slot %d.", slot);
  
  	if (toi_writer_posn.saved_chain_number[slot] == -1) {
  		toi_writer_posn.current_chain = NULL;
  		return;
  	}
  
  	while (cur_chain) {
  		int posn;
  		int j;
  		i++;
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, "Restoring chain %d (%p) "
  			    "state, slot %d.", i, cur_chain, slot);
  
  		chain_state = &cur_chain->saved_state[slot];
  
  		posn = chain_state->extent_num;
  
  		cur_chain->blocks.current_extent = cur_chain->blocks.first;
  		cur_chain->blocks.current_offset = chain_state->offset;
  
  		if (i == toi_writer_posn.saved_chain_number[slot]) {
  			toi_writer_posn.current_chain = cur_chain;
  			toi_message(TOI_BIO, TOI_VERBOSE, 0, "Found current chain.");
  		}
  
  		for (j = 0; j < 4; j++)
  			if (i == toi_writer_posn.saved_chain_number[j]) {
  				toi_writer_posn.saved_chain_ptr[j] = cur_chain;
  				toi_message(TOI_BIO, TOI_VERBOSE, 0,
  					    "Found saved chain ptr %d (%p) (offset"
  					    " %d).", j, cur_chain,
  					    cur_chain->saved_state[j].offset);
  			}
  
  		if (posn) {
  			while (--posn)
  				cur_chain->blocks.current_extent =
  				    cur_chain->blocks.current_extent->next;
  		} else
  			cur_chain->blocks.current_extent = NULL;
  
  		cur_chain = cur_chain->next;
  	}
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Done.");
  	if (test_action_state(TOI_LOGALL))
  		dump_block_chains();
  }
  
  /*
   * Storage needed
   *
   * Returns amount of space in the image header required
   * for the chain data. This ignores the links between
   * pages, which we factor in when allocating the space.
   */
  int toi_bio_devinfo_storage_needed(void)
  {
  	int result = sizeof(num_chains);
  	struct toi_bdev_info *chain = prio_chain_head;
  
  	while (chain) {
  		result += metadata_size;
  
  		/* Chain size */
  		result += sizeof(int);
  
  		/* Extents */
  		result += (2 * sizeof(unsigned long) * chain->blocks.num_extents);
  
  		chain = chain->next;
  	}
  
  	result += 4 * sizeof(int);
  	return result;
  }
  
  static unsigned long chain_pages_used(struct toi_bdev_info *chain)
  {
  	struct hibernate_extent *this = chain->blocks.first;
  	struct hibernate_extent_saved_state *state = &chain->saved_state[3];
  	unsigned long size = 0;
  	int extent_idx = 1;
  
  	if (!state->extent_num) {
  		if (!this)
  			return 0;
  		else
  			return chain->blocks.size;
  	}
  
  	while (extent_idx < state->extent_num) {
  		size += (this->end - this->start + 1);
  		this = this->next;
  		extent_idx++;
  	}
  
  	/* We didn't use the one we're sitting on, so don't count it */
  	return size + state->offset - this->start;
  }
  
  /**
   * toi_serialise_extent_chain - write a chain in the image
   * @chain:	Chain to write.
   **/
  static int toi_serialise_extent_chain(struct toi_bdev_info *chain)
  {
  	struct hibernate_extent *this;
  	int ret;
  	int i = 1;
  
  	chain->pages_used = chain_pages_used(chain);
  
  	if (test_action_state(TOI_LOGALL))
  		dump_block_chains();
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Serialising chain (dev_t %lx).", chain->dev_t);
  	/* Device info -  dev_t, prio, bmap_shift, blocks per page, positions */
  	ret = toiActiveAllocator->rw_header_chunk(WRITE, &toi_blockwriter_ops,
  						  (char *)&chain->uuid, metadata_size);
  	if (ret)
  		return ret;
  
  	/* Num extents */
  	ret = toiActiveAllocator->rw_header_chunk(WRITE, &toi_blockwriter_ops,
  						  (char *)&chain->blocks.num_extents, sizeof(int));
  	if (ret)
  		return ret;
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "%d extents.", chain->blocks.num_extents);
  
  	this = chain->blocks.first;
  	while (this) {
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, "Extent %d.", i);
  		ret = toiActiveAllocator->rw_header_chunk(WRITE,
  							  &toi_blockwriter_ops,
  							  (char *)this, 2 * sizeof(this->start));
  		if (ret)
  			return ret;
  		this = this->next;
  		i++;
  	}
  
  	return ret;
  }
  
  int toi_serialise_extent_chains(void)
  {
  	struct toi_bdev_info *this = prio_chain_head;
  	int result;
  
  	/* Write the number of chains */
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Write number of chains (%d)", num_chains);
  	result = toiActiveAllocator->rw_header_chunk(WRITE,
  						     &toi_blockwriter_ops, (char *)&num_chains,
  						     sizeof(int));
  	if (result)
  		return result;
  
  	/* Then the chains themselves */
  	while (this) {
  		result = toi_serialise_extent_chain(this);
  		if (result)
  			return result;
  		this = this->next;
  	}
  
  	/*
  	 * Finally, the chain we should be on at the start of each
  	 * section.
  	 */
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Saved chain numbers.");
  	result = toiActiveAllocator->rw_header_chunk(WRITE,
  						     &toi_blockwriter_ops,
  						     (char *)&toi_writer_posn.saved_chain_number[0],
  						     4 * sizeof(int));
  
  	return result;
  }
  
  int toi_register_storage_chain(struct toi_bdev_info *new)
  {
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Inserting chain %p into list.", new);
  	toi_insert_chain_in_prio_list(new);
  	return 0;
  }
  
  static void free_bdev_info(struct toi_bdev_info *chain)
  {
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Free chain %p.", chain);
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, " - Block extents.");
  	toi_put_extent_chain(&chain->blocks);
  
  	/*
  	 * The allocator may need to do more than just free the chains
  	 * (swap_free, for example). Don't call from boot kernel.
  	 */
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, " - Allocator extents.");
  	if (chain->allocator)
  		chain->allocator->bio_allocator_ops->free_storage(chain);
  
  	/*
  	 * Dropping out of reading atomic copy? Need to undo
  	 * toi_open_by_devnum.
  	 */
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, " - Bdev.");
  	if (chain->bdev && !IS_ERR(chain->bdev) &&
  	    chain->bdev != resume_block_device &&
  	    chain->bdev != header_block_device && test_toi_state(TOI_TRYING_TO_RESUME))
  		toi_close_bdev(chain->bdev);
  
  	/* Poison */
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, " - Struct.");
  	toi_kfree(39, chain, sizeof(*chain));
  
  	if (prio_chain_head == chain)
  		prio_chain_head = NULL;
  
  	num_chains--;
  }
  
  void free_all_bdev_info(void)
  {
  	struct toi_bdev_info *this = prio_chain_head;
  
  	while (this) {
  		struct toi_bdev_info *next = this->next;
  		free_bdev_info(this);
  		this = next;
  	}
  
  	memset((char *)&toi_writer_posn, 0, sizeof(toi_writer_posn));
  	prio_chain_head = NULL;
  }
  
  static void set_up_start_position(void)
  {
  	toi_writer_posn.current_chain = prio_chain_head;
  	go_next_page(0, 0);
  }
  
  /**
   * toi_load_extent_chain - read back a chain saved in the image
   * @chain:	Chain to load
   *
   * The linked list of extents is reconstructed from the disk. chain will point
   * to the first entry.
   **/
  int toi_load_extent_chain(int index, int *num_loaded)
  {
  	struct toi_bdev_info *chain = toi_kzalloc(39,
  						  sizeof(struct toi_bdev_info), GFP_ATOMIC);
  	struct hibernate_extent *this, *last = NULL;
  	int i, ret;
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Loading extent chain %d.", index);
  	/* Get dev_t, prio, bmap_shift, blocks per page, positions */
  	ret = toiActiveAllocator->rw_header_chunk_noreadahead(READ, NULL,
  							      (char *)&chain->uuid, metadata_size);
  
  	if (ret) {
  		printk(KERN_ERR "Failed to read the size of extent chain.\n");
  		toi_kfree(39, chain, sizeof(*chain));
  		return 1;
  	}
  
  	toi_bkd.pages_used[index] = chain->pages_used;
  
  	ret = toiActiveAllocator->rw_header_chunk_noreadahead(READ, NULL,
  							      (char *)&chain->blocks.num_extents,
  							      sizeof(int));
  	if (ret) {
  		printk(KERN_ERR "Failed to read the size of extent chain.\n");
  		toi_kfree(39, chain, sizeof(*chain));
  		return 1;
  	}
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "%d extents.", chain->blocks.num_extents);
  
  	for (i = 0; i < chain->blocks.num_extents; i++) {
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, "Extent %d.", i + 1);
  
  		this = toi_kzalloc(2, sizeof(struct hibernate_extent), TOI_ATOMIC_GFP);
  		if (!this) {
  			printk(KERN_INFO "Failed to allocate a new extent.\n");
  			free_bdev_info(chain);
  			return -ENOMEM;
  		}
  		this->next = NULL;
  		/* Get the next page */
  		ret = toiActiveAllocator->rw_header_chunk_noreadahead(READ,
  								      NULL, (char *)this,
  								      2 * sizeof(this->start));
  		if (ret) {
  			printk(KERN_INFO "Failed to read an extent.\n");
  			toi_kfree(2, this, sizeof(struct hibernate_extent));
  			free_bdev_info(chain);
  			return 1;
  		}
  
  		if (last)
  			last->next = this;
  		else {
  			char b1[32], b2[32], b3[32];
  			/*
  			 * Open the bdev
  			 */
  			toi_message(TOI_BIO, TOI_VERBOSE, 0,
  				    "Chain dev_t is %s. Resume dev t is %s. Header"
  				    " bdev_t is %s.\n",
  				    format_dev_t(b1, chain->dev_t),
  				    format_dev_t(b2, resume_dev_t),
  				    format_dev_t(b3, toi_sig_data->header_dev_t));
  
  			if (chain->dev_t == resume_dev_t)
  				chain->bdev = resume_block_device;
  			else if (chain->dev_t == toi_sig_data->header_dev_t)
  				chain->bdev = header_block_device;
  			else {
  				chain->bdev = toi_open_bdev(chain->uuid, chain->dev_t, 1);
  				if (IS_ERR(chain->bdev)) {
  					free_bdev_info(chain);
  					return -ENODEV;
  				}
  			}
  
  			toi_message(TOI_BIO, TOI_VERBOSE, 0, "Chain bmap shift "
  				    "is %d and blocks per page is %d.",
  				    chain->bmap_shift, chain->blocks_per_page);
  
  			chain->blocks.first = this;
  
  			/*
  			 * Couldn't do this earlier, but can't do
  			 * goto_start now - we may have already used blocks
  			 * in the first chain.
  			 */
  			chain->blocks.current_extent = this;
  			chain->blocks.current_offset = this->start;
  
  			/*
  			 * Can't wait until we've read the whole chain
  			 * before we insert it in the list. We might need
  			 * this chain to read the next page in the header
  			 */
  			toi_insert_chain_in_prio_list(chain);
  		}
  
  		/*
  		 * We have to wait until 2 extents are loaded before setting up
  		 * properly because if the first extent has only one page, we
  		 * will need to put the position on the second extent. Sounds
  		 * obvious, but it wasn't!
  		 */
  		(*num_loaded)++;
  		if ((*num_loaded) == 2)
  			set_up_start_position();
  		last = this;
  	}
  
  	/*
  	 * Shouldn't get empty chains, but it's not impossible. Link them in so
  	 * they get freed properly later.
  	 */
  	if (!chain->blocks.num_extents)
  		toi_insert_chain_in_prio_list(chain);
  
  	if (!chain->blocks.current_extent) {
  		chain->blocks.current_extent = chain->blocks.first;
  		if (chain->blocks.current_extent)
  			chain->blocks.current_offset = chain->blocks.current_extent->start;
  	}
  	return 0;
  }
  
  int toi_load_extent_chains(void)
  {
  	int result;
  	int to_load;
  	int i;
  	int extents_loaded = 0;
  
  	result = toiActiveAllocator->rw_header_chunk_noreadahead(READ, NULL,
  								 (char *)&to_load, sizeof(int));
  	if (result)
  		return result;
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "%d chains to read.", to_load);
  
  	for (i = 0; i < to_load; i++) {
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, " >> Loading chain %d/%d.", i, to_load);
  		result = toi_load_extent_chain(i, &extents_loaded);
  		if (result)
  			return result;
  	}
  
  	/* If we never got to a second extent, we still need to do this. */
  	if (extents_loaded == 1)
  		set_up_start_position();
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Save chain numbers.");
  	result = toiActiveAllocator->rw_header_chunk_noreadahead(READ,
  								 &toi_blockwriter_ops,
  								 (char *)&toi_writer_posn.
  								 saved_chain_number[0],
  								 4 * sizeof(int));
  
  	return result;
  }
  
  static int toi_end_of_stream(int writing, int section_barrier)
  {
  	struct toi_bdev_info *cur_chain = toi_writer_posn.current_chain;
  	int compare_to = next_section[current_stream];
  	struct toi_bdev_info *compare_chain = toi_writer_posn.saved_chain_ptr[compare_to];
  	int compare_offset = compare_chain ? compare_chain->saved_state[compare_to].offset : 0;
  
  	if (!section_barrier)
  		return 0;
  
  	if (!cur_chain)
  		return 1;
  
  	if (cur_chain == compare_chain && cur_chain->blocks.current_offset == compare_offset) {
  		if (writing) {
  			if (!current_stream) {
  				debug_broken_header();
  				return 1;
  			}
  		} else {
  			more_readahead = 0;
  			toi_message(TOI_BIO, TOI_VERBOSE, 0,
  				    "Reached the end of stream %d "
  				    "(not an error).", current_stream);
  			return 1;
  		}
  	}
  
  	return 0;
  }
  
  /**
   * go_next_page - skip blocks to the start of the next page
   * @writing: Whether we're reading or writing the image.
   *
   * Go forward one page.
   **/
  int go_next_page(int writing, int section_barrier)
  {
  	struct toi_bdev_info *cur_chain = toi_writer_posn.current_chain;
  	int max = cur_chain ? cur_chain->blocks_per_page : 1;
  
  	/* Nope. Go foward a page - or maybe two. Don't stripe the header,
  	 * so that bad fragmentation doesn't put the extent data containing
  	 * the location of the second page out of the first header page.
  	 */
  	if (toi_extent_state_next(max, current_stream)) {
  		/* Don't complain if readahead falls off the end */
  		if (writing && section_barrier) {
  			toi_message(TOI_BIO, TOI_VERBOSE, 0, "Extent state eof. "
  				    "Expected compression ratio too optimistic?");
  			if (test_action_state(TOI_LOGALL))
  				dump_block_chains();
  		}
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, "Ran out of extents to "
  			    "read/write. (Not necessarily a fatal error.");
  		return -ENOSPC;
  	}
  
  	return 0;
  }
  
  int devices_of_same_priority(struct toi_bdev_info *this)
  {
  	struct toi_bdev_info *check = prio_chain_head;
  	int i = 0;
  
  	while (check) {
  		if (check->prio == this->prio)
  			i++;
  		check = check->next;
  	}
  
  	return i;
  }
  
  /**
   * toi_bio_rw_page - do i/o on the next disk page in the image
   * @writing: Whether reading or writing.
   * @page: Page to do i/o on.
   * @is_readahead: Whether we're doing readahead
   * @free_group: The group used in allocating the page
   *
   * Submit a page for reading or writing, possibly readahead.
   * Pass the group used in allocating the page as well, as it should
   * be freed on completion of the bio if we're writing the page.
   **/
  int toi_bio_rw_page(int writing, struct page *page, int is_readahead, int free_group)
  {
  	int result = toi_end_of_stream(writing, 1);
  	struct toi_bdev_info *dev_info = toi_writer_posn.current_chain;
  
  	if (result) {
  		if (writing)
  			abort_hibernate(TOI_INSUFFICIENT_STORAGE,
  					"Insufficient storage for your image.");
  		else
  			toi_message(TOI_BIO, TOI_VERBOSE, 0, "Seeking to "
  				    "read/write another page when stream has " "ended.");
  		return -ENOSPC;
  	}
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0,
  		    "%s %lx:%ld",
  		    writing ? "Write" : "Read", dev_info->dev_t, dev_info->blocks.current_offset);
  
  	result = toi_do_io(writing, dev_info->bdev,
  			   dev_info->blocks.current_offset << dev_info->bmap_shift,
  			   page, is_readahead, 0, free_group);
  
  	/* Ignore the result here - will check end of stream if come in again */
  	go_next_page(writing, 1);
  
  	if (result)
  		printk(KERN_ERR "toi_do_io returned %d.\n", result);
  	return result;
  }
  
  dev_t get_header_dev_t(void)
  {
  	return prio_chain_head->dev_t;
  }
  
  struct block_device *get_header_bdev(void)
  {
  	return prio_chain_head->bdev;
  }
  
  unsigned long get_headerblock(void)
  {
  	return prio_chain_head->blocks.first->start << prio_chain_head->bmap_shift;
  }
  
  int get_main_pool_phys_params(void)
  {
  	struct toi_bdev_info *this = prio_chain_head;
  	int result;
  
  	while (this) {
  		result = this->allocator->bio_allocator_ops->bmap(this);
  		if (result)
  			return result;
  		this = this->next;
  	}
  
  	return 0;
  }
  
  static int apply_header_reservation(void)
  {
  	int i;
  
  	if (!header_pages_reserved) {
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, "No header pages reserved at the moment.");
  		return 0;
  	}
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Applying header reservation.");
  
  	/* Apply header space reservation */
  	toi_extent_state_goto_start();
  
  	for (i = 0; i < header_pages_reserved; i++)
  		if (go_next_page(1, 0))
  			return -ENOSPC;
  
  	/* The end of header pages will be the start of pageset 2 */
  	toi_extent_state_save(2);
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Finished applying header reservation.");
  	return 0;
  }
  
  static int toi_bio_register_storage(void)
  {
  	int result = 0;
  	struct toi_module_ops *this_module;
  
  	list_for_each_entry(this_module, &toi_modules, module_list) {
  		if (!this_module->enabled || this_module->type != BIO_ALLOCATOR_MODULE)
  			continue;
  		toi_message(TOI_BIO, TOI_VERBOSE, 0,
  			    "Registering storage from %s.", this_module->name);
  		result = this_module->bio_allocator_ops->register_storage();
  		if (result)
  			break;
  	}
  
  	return result;
  }
  
  int toi_bio_allocate_storage(unsigned long request)
  {
  	struct toi_bdev_info *chain = prio_chain_head;
  	unsigned long to_get = request;
  	unsigned long extra_pages, needed;
  	int no_free = 0;
  
  	if (!chain) {
  		int result = toi_bio_register_storage();
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, "toi_bio_allocate_storage: "
  			    "Registering storage.");
  		if (result)
  			return 0;
  		chain = prio_chain_head;
  		if (!chain) {
  			printk("TuxOnIce: No storage was registered.\n");
  			return 0;
  		}
  	}
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "toi_bio_allocate_storage: "
  		    "Request is %lu pages.", request);
  	extra_pages = DIV_ROUND_UP(request * (sizeof(unsigned long)
  					      + sizeof(int)), PAGE_SIZE);
  	needed = request + extra_pages + header_pages_reserved;
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Adding %lu extra pages and %lu "
  		    "for header => %lu.", extra_pages, header_pages_reserved, needed);
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Already allocated %lu pages.", raw_pages_allocd);
  
  	to_get = needed > raw_pages_allocd ? needed - raw_pages_allocd : 0;
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Need to get %lu pages.", to_get);
  
  	if (!to_get)
  		return apply_header_reservation();
  
  	while (to_get && chain) {
  		int num_group = devices_of_same_priority(chain);
  		int divisor = num_group - no_free;
  		int i;
  		unsigned long portion = DIV_ROUND_UP(to_get, divisor);
  		unsigned long got = 0;
  		unsigned long got_this_round = 0;
  		struct toi_bdev_info *top = chain;
  
  		toi_message(TOI_BIO, TOI_VERBOSE, 0,
  			    " Start of loop. To get is %lu. Divisor is %d.", to_get, divisor);
  		no_free = 0;
  
  		/*
  		 * We're aiming to spread the allocated storage as evenly
  		 * as possible, but we also want to get all the storage we
  		 * can off this priority.
  		 */
  		for (i = 0; i < num_group; i++) {
  			struct toi_bio_allocator_ops *ops = chain->allocator->bio_allocator_ops;
  			toi_message(TOI_BIO, TOI_VERBOSE, 0,
  				    " Asking for %lu pages from chain %p.", portion, chain);
  			got = ops->allocate_storage(chain, portion);
  			toi_message(TOI_BIO, TOI_VERBOSE, 0,
  				    " Got %lu pages from allocator %p.", got, chain);
  			if (!got)
  				no_free++;
  			got_this_round += got;
  			chain = chain->next;
  		}
  		toi_message(TOI_BIO, TOI_VERBOSE, 0, " Loop finished. Got a "
  			    "total of %lu pages from %d allocators.",
  			    got_this_round, divisor - no_free);
  
  		raw_pages_allocd += got_this_round;
  		to_get = needed > raw_pages_allocd ? needed - raw_pages_allocd : 0;
  
  		/*
  		 * If we got anything from chains of this priority and we
  		 * still have storage to allocate, go over this priority
  		 * again.
  		 */
  		if (got_this_round && to_get)
  			chain = top;
  		else
  			no_free = 0;
  	}
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Finished allocating. Calling "
  		    "get_main_pool_phys_params");
  	/* Now let swap allocator bmap the pages */
  	get_main_pool_phys_params();
  
  	toi_message(TOI_BIO, TOI_VERBOSE, 0, "Done. Reserving header.");
  	return apply_header_reservation();
  }
  
  void toi_bio_chains_post_atomic(struct toi_boot_kernel_data *bkd)
  {
  	int i = 0;
  	struct toi_bdev_info *cur_chain = prio_chain_head;
  
  	while (cur_chain) {
  		cur_chain->pages_used = bkd->pages_used[i];
  		cur_chain = cur_chain->next;
  		i++;
  	}
  }
  
  int toi_bio_chains_debug_info(char *buffer, int size)
  {
  	/* Show what we actually used */
  	struct toi_bdev_info *cur_chain = prio_chain_head;
  	int len = 0;
  
  	while (cur_chain) {
  		len += scnprintf(buffer + len, size - len, "  Used %lu pages "
  				 "from %s.\n", cur_chain->pages_used, cur_chain->name);
  		cur_chain = cur_chain->next;
  	}
  
  	return len;
  }
  