/*
   * linux/kernel/power/swap.c
   *
   * This file provides functions for reading the suspend image from
   * and writing it to a swap partition.
   *

   * Copyright (C) 1998,2001-2005 Pavel Machek <pavel@ucw.cz>

   * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>

   * Copyright (C) 2010 Bojan Smojver <bojan@rexursive.com>

   *
   * This file is released under the GPLv2.
   *
   */
  
  #include <linux/module.h>

  #include <linux/file.h>

  #include <linux/delay.h>
  #include <linux/bitops.h>
  #include <linux/genhd.h>
  #include <linux/device.h>

  #include <linux/bio.h>

  #include <linux/blkdev.h>

  #include <linux/swap.h>
  #include <linux/swapops.h>
  #include <linux/pm.h>

  #include <linux/slab.h>

  #include <linux/lzo.h>
  #include <linux/vmalloc.h>

  #include <linux/cpumask.h>
  #include <linux/atomic.h>
  #include <linux/kthread.h>
  #include <linux/crc32.h>

  
  #include "power.h"

  #define HIBERNATE_SIG	"S1SUSPEND"

  /*
   *	The swap map is a data structure used for keeping track of each page
   *	written to a swap partition.  It consists of many swap_map_page

   *	structures that contain each an array of MAP_PAGE_ENTRIES swap entries.

   *	These structures are stored on the swap and linked together with the
   *	help of the .next_swap member.
   *
   *	The swap map is created during suspend.  The swap map pages are
   *	allocated and populated one at a time, so we only need one memory
   *	page to set up the entire structure.
   *

   *	During resume we pick up all swap_map_page structures into a list.

   */
  
  #define MAP_PAGE_ENTRIES	(PAGE_SIZE / sizeof(sector_t) - 1)
  
  struct swap_map_page {
  	sector_t entries[MAP_PAGE_ENTRIES];
  	sector_t next_swap;
  };

  struct swap_map_page_list {
  	struct swap_map_page *map;
  	struct swap_map_page_list *next;
  };

  /**
   *	The swap_map_handle structure is used for handling swap in
   *	a file-alike way
   */
  
  struct swap_map_handle {
  	struct swap_map_page *cur;

  	struct swap_map_page_list *maps;

  	sector_t cur_swap;
  	sector_t first_sector;
  	unsigned int k;

  	unsigned long nr_free_pages, written;
  	u32 crc32;

  };

  struct swsusp_header {

  	char reserved[PAGE_SIZE - 20 - sizeof(sector_t) - sizeof(int) -
  	              sizeof(u32)];
  	u32	crc32;

  	sector_t image;

  	unsigned int flags;	/* Flags to pass to the "boot" kernel */

  	char	orig_sig[10];
  	char	sig[10];

  } __attribute__((packed));
  
  static struct swsusp_header *swsusp_header;

  /**
   *	The following functions are used for tracing the allocated
   *	swap pages, so that they can be freed in case of an error.
   */
  
  struct swsusp_extent {
  	struct rb_node node;
  	unsigned long start;
  	unsigned long end;
  };
  
  static struct rb_root swsusp_extents = RB_ROOT;
  
  static int swsusp_extents_insert(unsigned long swap_offset)
  {
  	struct rb_node **new = &(swsusp_extents.rb_node);
  	struct rb_node *parent = NULL;
  	struct swsusp_extent *ext;
  
  	/* Figure out where to put the new node */
  	while (*new) {
  		ext = container_of(*new, struct swsusp_extent, node);
  		parent = *new;
  		if (swap_offset < ext->start) {
  			/* Try to merge */
  			if (swap_offset == ext->start - 1) {
  				ext->start--;
  				return 0;
  			}
  			new = &((*new)->rb_left);
  		} else if (swap_offset > ext->end) {
  			/* Try to merge */
  			if (swap_offset == ext->end + 1) {
  				ext->end++;
  				return 0;
  			}
  			new = &((*new)->rb_right);
  		} else {
  			/* It already is in the tree */
  			return -EINVAL;
  		}
  	}
  	/* Add the new node and rebalance the tree. */
  	ext = kzalloc(sizeof(struct swsusp_extent), GFP_KERNEL);
  	if (!ext)
  		return -ENOMEM;
  
  	ext->start = swap_offset;
  	ext->end = swap_offset;
  	rb_link_node(&ext->node, parent, new);
  	rb_insert_color(&ext->node, &swsusp_extents);
  	return 0;
  }
  
  /**
   *	alloc_swapdev_block - allocate a swap page and register that it has
   *	been allocated, so that it can be freed in case of an error.
   */
  
  sector_t alloc_swapdev_block(int swap)
  {
  	unsigned long offset;

  	offset = swp_offset(get_swap_page_of_type(swap));

  	if (offset) {
  		if (swsusp_extents_insert(offset))

  			swap_free(swp_entry(swap, offset));

  		else
  			return swapdev_block(swap, offset);
  	}
  	return 0;
  }
  
  /**
   *	free_all_swap_pages - free swap pages allocated for saving image data.

   *	It also frees the extents used to register which swap entries had been

   *	allocated.
   */
  
  void free_all_swap_pages(int swap)
  {
  	struct rb_node *node;
  
  	while ((node = swsusp_extents.rb_node)) {
  		struct swsusp_extent *ext;
  		unsigned long offset;
  
  		ext = container_of(node, struct swsusp_extent, node);
  		rb_erase(node, &swsusp_extents);
  		for (offset = ext->start; offset <= ext->end; offset++)

  			swap_free(swp_entry(swap, offset));

  
  		kfree(ext);
  	}
  }
  
  int swsusp_swap_in_use(void)
  {
  	return (swsusp_extents.rb_node != NULL);
  }

  /*

   * General things

   */
  
  static unsigned short root_swap = 0xffff;

  struct block_device *hib_resume_bdev;

  /*
   * Saving part
   */

  static int mark_swapfiles(struct swap_map_handle *handle, unsigned int flags)

  {
  	int error;

  	hib_bio_read_page(swsusp_resume_block, swsusp_header, NULL);

  	if (!memcmp("SWAP-SPACE",swsusp_header->sig, 10) ||
  	    !memcmp("SWAPSPACE2",swsusp_header->sig, 10)) {
  		memcpy(swsusp_header->orig_sig,swsusp_header->sig, 10);

  		memcpy(swsusp_header->sig, HIBERNATE_SIG, 10);

  		swsusp_header->image = handle->first_sector;

  		swsusp_header->flags = flags;

  		if (flags & SF_CRC32_MODE)
  			swsusp_header->crc32 = handle->crc32;

  		error = hib_bio_write_page(swsusp_resume_block,

  					swsusp_header, NULL);

  	} else {

  		printk(KERN_ERR "PM: Swap header not found!
  ");

  		error = -ENODEV;
  	}
  	return error;
  }
  
  /**
   *	swsusp_swap_check - check if the resume device is a swap device
   *	and get its index (if so)

   *
   *	This is called before saving image

   */

  static int swsusp_swap_check(void)

  {

  	int res;

  	res = swap_type_of(swsusp_resume_device, swsusp_resume_block,

  			&hib_resume_bdev);

  	if (res < 0)
  		return res;
  
  	root_swap = res;

  	res = blkdev_get(hib_resume_bdev, FMODE_WRITE, NULL);

  	if (res)
  		return res;

  	res = set_blocksize(hib_resume_bdev, PAGE_SIZE);

  	if (res < 0)

  		blkdev_put(hib_resume_bdev, FMODE_WRITE);

  	return res;
  }
  
  /**
   *	write_page - Write one page to given swap location.
   *	@buf:		Address we're writing.
   *	@offset:	Offset of the swap page we're writing to.

   *	@bio_chain:	Link the next write BIO here

   */

  static int write_page(void *buf, sector_t offset, struct bio **bio_chain)

  {

  	void *src;

  	int ret;

  
  	if (!offset)
  		return -ENOSPC;
  
  	if (bio_chain) {

  		src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);

  		if (src) {

  			copy_page(src, buf);

  		} else {

  			ret = hib_wait_on_bio_chain(bio_chain); /* Free pages */
  			if (ret)
  				return ret;
  			src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
  			if (src) {
  				copy_page(src, buf);
  			} else {
  				WARN_ON_ONCE(1);
  				bio_chain = NULL;	/* Go synchronous */
  				src = buf;
  			}

  		}

  	} else {
  		src = buf;

  	}

  	return hib_bio_write_page(offset, src, bio_chain);

  }

  static void release_swap_writer(struct swap_map_handle *handle)
  {
  	if (handle->cur)
  		free_page((unsigned long)handle->cur);
  	handle->cur = NULL;

  }
  
  static int get_swap_writer(struct swap_map_handle *handle)
  {

  	int ret;
  
  	ret = swsusp_swap_check();
  	if (ret) {
  		if (ret != -ENOSPC)
  			printk(KERN_ERR "PM: Cannot find swap device, try "
  					"swapon -a.
  ");
  		return ret;
  	}

  	handle->cur = (struct swap_map_page *)get_zeroed_page(GFP_KERNEL);

  	if (!handle->cur) {
  		ret = -ENOMEM;
  		goto err_close;
  	}

  	handle->cur_swap = alloc_swapdev_block(root_swap);

  	if (!handle->cur_swap) {

  		ret = -ENOSPC;
  		goto err_rel;

  	}
  	handle->k = 0;

  	handle->nr_free_pages = nr_free_pages() >> 1;
  	handle->written = 0;

  	handle->first_sector = handle->cur_swap;

  	return 0;

  err_rel:
  	release_swap_writer(handle);
  err_close:
  	swsusp_close(FMODE_WRITE);
  	return ret;

  }

  static int swap_write_page(struct swap_map_handle *handle, void *buf,
  				struct bio **bio_chain)
  {
  	int error = 0;

  	sector_t offset;

  
  	if (!handle->cur)
  		return -EINVAL;

  	offset = alloc_swapdev_block(root_swap);

  	error = write_page(buf, offset, bio_chain);

  	if (error)
  		return error;
  	handle->cur->entries[handle->k++] = offset;
  	if (handle->k >= MAP_PAGE_ENTRIES) {

  		offset = alloc_swapdev_block(root_swap);

  		if (!offset)
  			return -ENOSPC;
  		handle->cur->next_swap = offset;

  		error = write_page(handle->cur, handle->cur_swap, bio_chain);

  		if (error)

  			goto out;

  		clear_page(handle->cur);

  		handle->cur_swap = offset;
  		handle->k = 0;
  	}

  	if (bio_chain && ++handle->written > handle->nr_free_pages) {
  		error = hib_wait_on_bio_chain(bio_chain);
  		if (error)
  			goto out;
  		handle->written = 0;
  	}

   out:

  	return error;

  }
  
  static int flush_swap_writer(struct swap_map_handle *handle)
  {
  	if (handle->cur && handle->cur_swap)

  		return write_page(handle->cur, handle->cur_swap, NULL);

  	else
  		return -EINVAL;
  }

  static int swap_writer_finish(struct swap_map_handle *handle,
  		unsigned int flags, int error)
  {
  	if (!error) {
  		flush_swap_writer(handle);
  		printk(KERN_INFO "PM: S");
  		error = mark_swapfiles(handle, flags);
  		printk("|
  ");
  	}
  
  	if (error)
  		free_all_swap_pages(root_swap);
  	release_swap_writer(handle);
  	swsusp_close(FMODE_WRITE);
  
  	return error;
  }

  /* We need to remember how much compressed data we need to read. */
  #define LZO_HEADER	sizeof(size_t)
  
  /* Number of pages/bytes we'll compress at one time. */
  #define LZO_UNC_PAGES	32
  #define LZO_UNC_SIZE	(LZO_UNC_PAGES * PAGE_SIZE)
  
  /* Number of pages/bytes we need for compressed data (worst case). */
  #define LZO_CMP_PAGES	DIV_ROUND_UP(lzo1x_worst_compress(LZO_UNC_SIZE) + \
  			             LZO_HEADER, PAGE_SIZE)
  #define LZO_CMP_SIZE	(LZO_CMP_PAGES * PAGE_SIZE)

  /* Maximum number of threads for compression/decompression. */
  #define LZO_THREADS	3
  
  /* Maximum number of pages for read buffering. */
  #define LZO_READ_PAGES	(MAP_PAGE_ENTRIES * 8)

  /**
   *	save_image - save the suspend image data
   */
  
  static int save_image(struct swap_map_handle *handle,
                        struct snapshot_handle *snapshot,

                        unsigned int nr_to_write)

  {
  	unsigned int m;
  	int ret;

  	int nr_pages;

  	int err2;
  	struct bio *bio;

  	struct timeval start;
  	struct timeval stop;

  	printk(KERN_INFO "PM: Saving image data pages (%u pages) ...     ",
  		nr_to_write);

  	m = nr_to_write / 100;

  	if (!m)
  		m = 1;
  	nr_pages = 0;

  	bio = NULL;

  	do_gettimeofday(&start);

  	while (1) {

  		ret = snapshot_read_next(snapshot);

  		if (ret <= 0)
  			break;
  		ret = swap_write_page(handle, data_of(*snapshot), &bio);
  		if (ret)
  			break;
  		if (!(nr_pages % m))

  			printk(KERN_CONT "\b\b\b\b%3d%%", nr_pages / m);

  		nr_pages++;
  	}

  	err2 = hib_wait_on_bio_chain(&bio);

  	do_gettimeofday(&stop);

  	if (!ret)
  		ret = err2;
  	if (!ret)

  		printk(KERN_CONT "\b\b\b\bdone
  ");

  	else

  		printk(KERN_CONT "
  ");

  	swsusp_show_speed(&start, &stop, nr_to_write, "Wrote");

  	return ret;

  }

  /**
   * Structure used for CRC32.
   */
  struct crc_data {
  	struct task_struct *thr;                  /* thread */
  	atomic_t ready;                           /* ready to start flag */
  	atomic_t stop;                            /* ready to stop flag */
  	unsigned run_threads;                     /* nr current threads */
  	wait_queue_head_t go;                     /* start crc update */
  	wait_queue_head_t done;                   /* crc update done */
  	u32 *crc32;                               /* points to handle's crc32 */
  	size_t *unc_len[LZO_THREADS];             /* uncompressed lengths */
  	unsigned char *unc[LZO_THREADS];          /* uncompressed data */
  };
  
  /**
   * CRC32 update function that runs in its own thread.
   */
  static int crc32_threadfn(void *data)
  {
  	struct crc_data *d = data;
  	unsigned i;
  
  	while (1) {
  		wait_event(d->go, atomic_read(&d->ready) ||
  		                  kthread_should_stop());
  		if (kthread_should_stop()) {
  			d->thr = NULL;
  			atomic_set(&d->stop, 1);
  			wake_up(&d->done);
  			break;
  		}
  		atomic_set(&d->ready, 0);
  
  		for (i = 0; i < d->run_threads; i++)
  			*d->crc32 = crc32_le(*d->crc32,
  			                     d->unc[i], *d->unc_len[i]);
  		atomic_set(&d->stop, 1);
  		wake_up(&d->done);
  	}
  	return 0;
  }
  /**
   * Structure used for LZO data compression.
   */
  struct cmp_data {
  	struct task_struct *thr;                  /* thread */
  	atomic_t ready;                           /* ready to start flag */
  	atomic_t stop;                            /* ready to stop flag */
  	int ret;                                  /* return code */
  	wait_queue_head_t go;                     /* start compression */
  	wait_queue_head_t done;                   /* compression done */
  	size_t unc_len;                           /* uncompressed length */
  	size_t cmp_len;                           /* compressed length */
  	unsigned char unc[LZO_UNC_SIZE];          /* uncompressed buffer */
  	unsigned char cmp[LZO_CMP_SIZE];          /* compressed buffer */
  	unsigned char wrk[LZO1X_1_MEM_COMPRESS];  /* compression workspace */
  };
  
  /**
   * Compression function that runs in its own thread.
   */
  static int lzo_compress_threadfn(void *data)
  {
  	struct cmp_data *d = data;
  
  	while (1) {
  		wait_event(d->go, atomic_read(&d->ready) ||
  		                  kthread_should_stop());
  		if (kthread_should_stop()) {
  			d->thr = NULL;
  			d->ret = -1;
  			atomic_set(&d->stop, 1);
  			wake_up(&d->done);
  			break;
  		}
  		atomic_set(&d->ready, 0);
  
  		d->ret = lzo1x_1_compress(d->unc, d->unc_len,
  		                          d->cmp + LZO_HEADER, &d->cmp_len,
  		                          d->wrk);
  		atomic_set(&d->stop, 1);
  		wake_up(&d->done);
  	}
  	return 0;
  }

  
  /**
   * save_image_lzo - Save the suspend image data compressed with LZO.
   * @handle: Swap mam handle to use for saving the image.
   * @snapshot: Image to read data from.
   * @nr_to_write: Number of pages to save.
   */
  static int save_image_lzo(struct swap_map_handle *handle,
                            struct snapshot_handle *snapshot,
                            unsigned int nr_to_write)
  {
  	unsigned int m;
  	int ret = 0;
  	int nr_pages;
  	int err2;
  	struct bio *bio;
  	struct timeval start;
  	struct timeval stop;

  	size_t off;
  	unsigned thr, run_threads, nr_threads;
  	unsigned char *page = NULL;
  	struct cmp_data *data = NULL;
  	struct crc_data *crc = NULL;
  
  	/*
  	 * We'll limit the number of threads for compression to limit memory
  	 * footprint.
  	 */
  	nr_threads = num_online_cpus() - 1;
  	nr_threads = clamp_val(nr_threads, 1, LZO_THREADS);

  
  	page = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
  	if (!page) {
  		printk(KERN_ERR "PM: Failed to allocate LZO page
  ");

  		ret = -ENOMEM;
  		goto out_clean;

  	}

  	data = vmalloc(sizeof(*data) * nr_threads);
  	if (!data) {
  		printk(KERN_ERR "PM: Failed to allocate LZO data
  ");
  		ret = -ENOMEM;
  		goto out_clean;

  	}

  	for (thr = 0; thr < nr_threads; thr++)
  		memset(&data[thr], 0, offsetof(struct cmp_data, go));

  	crc = kmalloc(sizeof(*crc), GFP_KERNEL);
  	if (!crc) {
  		printk(KERN_ERR "PM: Failed to allocate crc
  ");
  		ret = -ENOMEM;
  		goto out_clean;
  	}
  	memset(crc, 0, offsetof(struct crc_data, go));
  
  	/*
  	 * Start the compression threads.
  	 */
  	for (thr = 0; thr < nr_threads; thr++) {
  		init_waitqueue_head(&data[thr].go);
  		init_waitqueue_head(&data[thr].done);
  
  		data[thr].thr = kthread_run(lzo_compress_threadfn,
  		                            &data[thr],
  		                            "image_compress/%u", thr);
  		if (IS_ERR(data[thr].thr)) {
  			data[thr].thr = NULL;
  			printk(KERN_ERR
  			       "PM: Cannot start compression threads
  ");
  			ret = -ENOMEM;
  			goto out_clean;
  		}

  	}

  	/*
  	 * Adjust number of free pages after all allocations have been done.
  	 * We don't want to run out of pages when writing.
  	 */
  	handle->nr_free_pages = nr_free_pages() >> 1;
  
  	/*
  	 * Start the CRC32 thread.
  	 */
  	init_waitqueue_head(&crc->go);
  	init_waitqueue_head(&crc->done);
  
  	handle->crc32 = 0;
  	crc->crc32 = &handle->crc32;
  	for (thr = 0; thr < nr_threads; thr++) {
  		crc->unc[thr] = data[thr].unc;
  		crc->unc_len[thr] = &data[thr].unc_len;
  	}
  
  	crc->thr = kthread_run(crc32_threadfn, crc, "image_crc32");
  	if (IS_ERR(crc->thr)) {
  		crc->thr = NULL;
  		printk(KERN_ERR "PM: Cannot start CRC32 thread
  ");
  		ret = -ENOMEM;
  		goto out_clean;

  	}
  
  	printk(KERN_INFO

  		"PM: Using %u thread(s) for compression.
  "

  		"PM: Compressing and saving image data (%u pages) ...     ",

  		nr_threads, nr_to_write);

  	m = nr_to_write / 100;
  	if (!m)
  		m = 1;
  	nr_pages = 0;
  	bio = NULL;
  	do_gettimeofday(&start);
  	for (;;) {

  		for (thr = 0; thr < nr_threads; thr++) {
  			for (off = 0; off < LZO_UNC_SIZE; off += PAGE_SIZE) {
  				ret = snapshot_read_next(snapshot);
  				if (ret < 0)
  					goto out_finish;
  
  				if (!ret)
  					break;
  
  				memcpy(data[thr].unc + off,
  				       data_of(*snapshot), PAGE_SIZE);
  
  				if (!(nr_pages % m))
  					printk(KERN_CONT "\b\b\b\b%3d%%",
  				               nr_pages / m);
  				nr_pages++;
  			}
  			if (!off)

  				break;

  			data[thr].unc_len = off;

  			atomic_set(&data[thr].ready, 1);
  			wake_up(&data[thr].go);

  		}

  		if (!thr)

  			break;

  		crc->run_threads = thr;
  		atomic_set(&crc->ready, 1);
  		wake_up(&crc->go);

  		for (run_threads = thr, thr = 0; thr < run_threads; thr++) {
  			wait_event(data[thr].done,
  			           atomic_read(&data[thr].stop));
  			atomic_set(&data[thr].stop, 0);

  			ret = data[thr].ret;

  			if (ret < 0) {
  				printk(KERN_ERR "PM: LZO compression failed
  ");
  				goto out_finish;
  			}

  			if (unlikely(!data[thr].cmp_len ||
  			             data[thr].cmp_len >
  			             lzo1x_worst_compress(data[thr].unc_len))) {
  				printk(KERN_ERR
  				       "PM: Invalid LZO compressed length
  ");
  				ret = -1;

  				goto out_finish;

  			}
  
  			*(size_t *)data[thr].cmp = data[thr].cmp_len;
  
  			/*
  			 * Given we are writing one page at a time to disk, we
  			 * copy that much from the buffer, although the last
  			 * bit will likely be smaller than full page. This is
  			 * OK - we saved the length of the compressed data, so
  			 * any garbage at the end will be discarded when we
  			 * read it.
  			 */
  			for (off = 0;
  			     off < LZO_HEADER + data[thr].cmp_len;
  			     off += PAGE_SIZE) {
  				memcpy(page, data[thr].cmp + off, PAGE_SIZE);
  
  				ret = swap_write_page(handle, page, &bio);
  				if (ret)
  					goto out_finish;
  			}

  		}

  
  		wait_event(crc->done, atomic_read(&crc->stop));
  		atomic_set(&crc->stop, 0);

  	}
  
  out_finish:
  	err2 = hib_wait_on_bio_chain(&bio);
  	do_gettimeofday(&stop);
  	if (!ret)
  		ret = err2;

  	if (!ret) {

  		printk(KERN_CONT "\b\b\b\bdone
  ");

  	} else {

  		printk(KERN_CONT "
  ");

  	}

  	swsusp_show_speed(&start, &stop, nr_to_write, "Wrote");

  out_clean:
  	if (crc) {
  		if (crc->thr)
  			kthread_stop(crc->thr);
  		kfree(crc);
  	}
  	if (data) {
  		for (thr = 0; thr < nr_threads; thr++)
  			if (data[thr].thr)
  				kthread_stop(data[thr].thr);
  		vfree(data);
  	}
  	if (page) free_page((unsigned long)page);

  
  	return ret;
  }

  /**
   *	enough_swap - Make sure we have enough swap to save the image.
   *
   *	Returns TRUE or FALSE after checking the total amount of swap
   *	space avaiable from the resume partition.
   */

  static int enough_swap(unsigned int nr_pages, unsigned int flags)

  {
  	unsigned int free_swap = count_swap_pages(root_swap, 1);

  	unsigned int required;

  	pr_debug("PM: Free swap pages: %u
  ", free_swap);

  
  	required = PAGES_FOR_IO + ((flags & SF_NOCOMPRESS_MODE) ?
  		nr_pages : (nr_pages * LZO_CMP_PAGES) / LZO_UNC_PAGES + 1);
  	return free_swap > required;

  }
  
  /**
   *	swsusp_write - Write entire image and metadata.

   *	@flags: flags to pass to the "boot" kernel in the image header

   *
   *	It is important _NOT_ to umount filesystems at this point. We want
   *	them synced (in case something goes wrong) but we DO not want to mark
   *	filesystem clean: it is not. (And it does not matter, if we resume
   *	correctly, we'll mark system clean, anyway.)
   */

  int swsusp_write(unsigned int flags)

  {
  	struct swap_map_handle handle;
  	struct snapshot_handle snapshot;
  	struct swsusp_info *header;

  	unsigned long pages;

  	int error;

  	pages = snapshot_get_image_size();
  	error = get_swap_writer(&handle);

  	if (error) {

  		printk(KERN_ERR "PM: Cannot get swap writer
  ");

  		return error;
  	}

  	if (!enough_swap(pages, flags)) {

  		printk(KERN_ERR "PM: Not enough free swap
  ");
  		error = -ENOSPC;
  		goto out_finish;
  	}

  	memset(&snapshot, 0, sizeof(struct snapshot_handle));

  	error = snapshot_read_next(&snapshot);

  	if (error < PAGE_SIZE) {
  		if (error >= 0)
  			error = -EFAULT;

  		goto out_finish;

  	}

  	header = (struct swsusp_info *)data_of(snapshot);

  	error = swap_write_page(&handle, header, NULL);

  	if (!error) {
  		error = (flags & SF_NOCOMPRESS_MODE) ?
  			save_image(&handle, &snapshot, pages - 1) :
  			save_image_lzo(&handle, &snapshot, pages - 1);
  	}

  out_finish:
  	error = swap_writer_finish(&handle, flags, error);

  	return error;
  }

  /**
   *	The following functions allow us to read data using a swap map
   *	in a file-alike way
   */
  
  static void release_swap_reader(struct swap_map_handle *handle)
  {

  	struct swap_map_page_list *tmp;
  
  	while (handle->maps) {
  		if (handle->maps->map)
  			free_page((unsigned long)handle->maps->map);
  		tmp = handle->maps;
  		handle->maps = handle->maps->next;
  		kfree(tmp);
  	}

  	handle->cur = NULL;
  }

  static int get_swap_reader(struct swap_map_handle *handle,
  		unsigned int *flags_p)

  {
  	int error;

  	struct swap_map_page_list *tmp, *last;
  	sector_t offset;

  	*flags_p = swsusp_header->flags;
  
  	if (!swsusp_header->image) /* how can this happen? */

  		return -EINVAL;

  	handle->cur = NULL;
  	last = handle->maps = NULL;
  	offset = swsusp_header->image;
  	while (offset) {
  		tmp = kmalloc(sizeof(*handle->maps), GFP_KERNEL);
  		if (!tmp) {
  			release_swap_reader(handle);
  			return -ENOMEM;
  		}
  		memset(tmp, 0, sizeof(*tmp));
  		if (!handle->maps)
  			handle->maps = tmp;
  		if (last)
  			last->next = tmp;
  		last = tmp;
  
  		tmp->map = (struct swap_map_page *)
  		           __get_free_page(__GFP_WAIT | __GFP_HIGH);
  		if (!tmp->map) {
  			release_swap_reader(handle);
  			return -ENOMEM;
  		}

  		error = hib_bio_read_page(offset, tmp->map, NULL);
  		if (error) {
  			release_swap_reader(handle);
  			return error;
  		}
  		offset = tmp->map->next_swap;

  	}
  	handle->k = 0;

  	handle->cur = handle->maps->map;

  	return 0;
  }

  static int swap_read_page(struct swap_map_handle *handle, void *buf,
  				struct bio **bio_chain)

  {

  	sector_t offset;

  	int error;

  	struct swap_map_page_list *tmp;

  
  	if (!handle->cur)
  		return -EINVAL;
  	offset = handle->cur->entries[handle->k];
  	if (!offset)
  		return -EFAULT;

  	error = hib_bio_read_page(offset, buf, bio_chain);

  	if (error)
  		return error;
  	if (++handle->k >= MAP_PAGE_ENTRIES) {
  		handle->k = 0;

  		free_page((unsigned long)handle->maps->map);
  		tmp = handle->maps;
  		handle->maps = handle->maps->next;
  		kfree(tmp);
  		if (!handle->maps)

  			release_swap_reader(handle);

  		else
  			handle->cur = handle->maps->map;

  	}
  	return error;
  }

  static int swap_reader_finish(struct swap_map_handle *handle)
  {
  	release_swap_reader(handle);
  
  	return 0;
  }

  /**
   *	load_image - load the image using the swap map handle
   *	@handle and the snapshot handle @snapshot
   *	(assume there are @nr_pages pages to load)
   */
  
  static int load_image(struct swap_map_handle *handle,
                        struct snapshot_handle *snapshot,

                        unsigned int nr_to_read)

  {
  	unsigned int m;

  	int ret = 0;

  	struct timeval start;
  	struct timeval stop;

  	struct bio *bio;
  	int err2;
  	unsigned nr_pages;

  	printk(KERN_INFO "PM: Loading image data pages (%u pages) ...     ",
  		nr_to_read);

  	m = nr_to_read / 100;

  	if (!m)
  		m = 1;
  	nr_pages = 0;

  	bio = NULL;

  	do_gettimeofday(&start);

  	for ( ; ; ) {

  		ret = snapshot_write_next(snapshot);
  		if (ret <= 0)

  			break;

  		ret = swap_read_page(handle, data_of(*snapshot), &bio);
  		if (ret)

  			break;
  		if (snapshot->sync_read)

  			ret = hib_wait_on_bio_chain(&bio);
  		if (ret)

  			break;
  		if (!(nr_pages % m))
  			printk("\b\b\b\b%3d%%", nr_pages / m);
  		nr_pages++;
  	}

  	err2 = hib_wait_on_bio_chain(&bio);

  	do_gettimeofday(&stop);

  	if (!ret)
  		ret = err2;
  	if (!ret) {

  		printk("\b\b\b\bdone
  ");

  		snapshot_write_finalize(snapshot);

  		if (!snapshot_image_loaded(snapshot))

  			ret = -ENODATA;

  	} else
  		printk("
  ");

  	swsusp_show_speed(&start, &stop, nr_to_read, "Read");

  	return ret;
  }
  
  /**
   * Structure used for LZO data decompression.
   */
  struct dec_data {
  	struct task_struct *thr;                  /* thread */
  	atomic_t ready;                           /* ready to start flag */
  	atomic_t stop;                            /* ready to stop flag */
  	int ret;                                  /* return code */
  	wait_queue_head_t go;                     /* start decompression */
  	wait_queue_head_t done;                   /* decompression done */
  	size_t unc_len;                           /* uncompressed length */
  	size_t cmp_len;                           /* compressed length */
  	unsigned char unc[LZO_UNC_SIZE];          /* uncompressed buffer */
  	unsigned char cmp[LZO_CMP_SIZE];          /* compressed buffer */
  };
  
  /**
   * Deompression function that runs in its own thread.
   */
  static int lzo_decompress_threadfn(void *data)
  {
  	struct dec_data *d = data;
  
  	while (1) {
  		wait_event(d->go, atomic_read(&d->ready) ||
  		                  kthread_should_stop());
  		if (kthread_should_stop()) {
  			d->thr = NULL;
  			d->ret = -1;
  			atomic_set(&d->stop, 1);
  			wake_up(&d->done);
  			break;
  		}
  		atomic_set(&d->ready, 0);
  
  		d->unc_len = LZO_UNC_SIZE;
  		d->ret = lzo1x_decompress_safe(d->cmp + LZO_HEADER, d->cmp_len,
  		                               d->unc, &d->unc_len);
  		atomic_set(&d->stop, 1);
  		wake_up(&d->done);
  	}
  	return 0;

  }

  /**

   * load_image_lzo - Load compressed image data and decompress them with LZO.
   * @handle: Swap map handle to use for loading data.
   * @snapshot: Image to copy uncompressed data into.
   * @nr_to_read: Number of pages to load.
   */
  static int load_image_lzo(struct swap_map_handle *handle,
                            struct snapshot_handle *snapshot,
                            unsigned int nr_to_read)
  {
  	unsigned int m;

  	int ret = 0;
  	int eof = 0;

  	struct bio *bio;

  	struct timeval start;
  	struct timeval stop;
  	unsigned nr_pages;

  	size_t off;
  	unsigned i, thr, run_threads, nr_threads;
  	unsigned ring = 0, pg = 0, ring_size = 0,
  	         have = 0, want, need, asked = 0;
  	unsigned long read_pages;
  	unsigned char **page = NULL;
  	struct dec_data *data = NULL;
  	struct crc_data *crc = NULL;
  
  	/*
  	 * We'll limit the number of threads for decompression to limit memory
  	 * footprint.
  	 */
  	nr_threads = num_online_cpus() - 1;
  	nr_threads = clamp_val(nr_threads, 1, LZO_THREADS);
  
  	page = vmalloc(sizeof(*page) * LZO_READ_PAGES);
  	if (!page) {
  		printk(KERN_ERR "PM: Failed to allocate LZO page
  ");
  		ret = -ENOMEM;
  		goto out_clean;
  	}

  	data = vmalloc(sizeof(*data) * nr_threads);
  	if (!data) {
  		printk(KERN_ERR "PM: Failed to allocate LZO data
  ");
  		ret = -ENOMEM;
  		goto out_clean;
  	}
  	for (thr = 0; thr < nr_threads; thr++)
  		memset(&data[thr], 0, offsetof(struct dec_data, go));

  	crc = kmalloc(sizeof(*crc), GFP_KERNEL);
  	if (!crc) {
  		printk(KERN_ERR "PM: Failed to allocate crc
  ");
  		ret = -ENOMEM;
  		goto out_clean;
  	}
  	memset(crc, 0, offsetof(struct crc_data, go));
  
  	/*
  	 * Start the decompression threads.
  	 */
  	for (thr = 0; thr < nr_threads; thr++) {
  		init_waitqueue_head(&data[thr].go);
  		init_waitqueue_head(&data[thr].done);
  
  		data[thr].thr = kthread_run(lzo_decompress_threadfn,
  		                            &data[thr],
  		                            "image_decompress/%u", thr);
  		if (IS_ERR(data[thr].thr)) {
  			data[thr].thr = NULL;
  			printk(KERN_ERR
  			       "PM: Cannot start decompression threads
  ");
  			ret = -ENOMEM;
  			goto out_clean;

  		}

  	}

  	/*
  	 * Start the CRC32 thread.
  	 */
  	init_waitqueue_head(&crc->go);
  	init_waitqueue_head(&crc->done);
  
  	handle->crc32 = 0;
  	crc->crc32 = &handle->crc32;
  	for (thr = 0; thr < nr_threads; thr++) {
  		crc->unc[thr] = data[thr].unc;
  		crc->unc_len[thr] = &data[thr].unc_len;

  	}

  	crc->thr = kthread_run(crc32_threadfn, crc, "image_crc32");
  	if (IS_ERR(crc->thr)) {
  		crc->thr = NULL;
  		printk(KERN_ERR "PM: Cannot start CRC32 thread
  ");
  		ret = -ENOMEM;
  		goto out_clean;
  	}

  	/*
  	 * Adjust number of pages for read buffering, in case we are short.
  	 */
  	read_pages = (nr_free_pages() - snapshot_get_image_size()) >> 1;
  	read_pages = clamp_val(read_pages, LZO_CMP_PAGES, LZO_READ_PAGES);

  	for (i = 0; i < read_pages; i++) {
  		page[i] = (void *)__get_free_page(i < LZO_CMP_PAGES ?
  		                                  __GFP_WAIT | __GFP_HIGH :
  		                                  __GFP_WAIT);
  		if (!page[i]) {
  			if (i < LZO_CMP_PAGES) {
  				ring_size = i;
  				printk(KERN_ERR
  				       "PM: Failed to allocate LZO pages
  ");
  				ret = -ENOMEM;
  				goto out_clean;
  			} else {
  				break;
  			}
  		}

  	}

  	want = ring_size = i;

  
  	printk(KERN_INFO

  		"PM: Using %u thread(s) for decompression.
  "

  		"PM: Loading and decompressing image data (%u pages) ...     ",

  		nr_threads, nr_to_read);

  	m = nr_to_read / 100;
  	if (!m)
  		m = 1;
  	nr_pages = 0;

  	bio = NULL;

  	do_gettimeofday(&start);

  	ret = snapshot_write_next(snapshot);
  	if (ret <= 0)

  		goto out_finish;

  	for(;;) {
  		for (i = 0; !eof && i < want; i++) {
  			ret = swap_read_page(handle, page[ring], &bio);
  			if (ret) {
  				/*
  				 * On real read error, finish. On end of data,
  				 * set EOF flag and just exit the read loop.
  				 */
  				if (handle->cur &&
  				    handle->cur->entries[handle->k]) {
  					goto out_finish;
  				} else {
  					eof = 1;
  					break;
  				}
  			}
  			if (++ring >= ring_size)
  				ring = 0;

  		}

  		asked += i;
  		want -= i;

  		/*
  		 * We are out of data, wait for some more.
  		 */
  		if (!have) {
  			if (!asked)
  				break;
  
  			ret = hib_wait_on_bio_chain(&bio);
  			if (ret)

  				goto out_finish;

  			have += asked;
  			asked = 0;
  			if (eof)
  				eof = 2;

  		}

  		if (crc->run_threads) {
  			wait_event(crc->done, atomic_read(&crc->stop));
  			atomic_set(&crc->stop, 0);
  			crc->run_threads = 0;

  		}

  		for (thr = 0; have && thr < nr_threads; thr++) {
  			data[thr].cmp_len = *(size_t *)page[pg];
  			if (unlikely(!data[thr].cmp_len ||
  			             data[thr].cmp_len >
  			             lzo1x_worst_compress(LZO_UNC_SIZE))) {
  				printk(KERN_ERR
  				       "PM: Invalid LZO compressed length
  ");
  				ret = -1;
  				goto out_finish;
  			}
  
  			need = DIV_ROUND_UP(data[thr].cmp_len + LZO_HEADER,
  			                    PAGE_SIZE);
  			if (need > have) {
  				if (eof > 1) {
  					ret = -1;
  					goto out_finish;
  				}
  				break;
  			}
  
  			for (off = 0;
  			     off < LZO_HEADER + data[thr].cmp_len;
  			     off += PAGE_SIZE) {
  				memcpy(data[thr].cmp + off,
  				       page[pg], PAGE_SIZE);
  				have--;
  				want++;
  				if (++pg >= ring_size)
  					pg = 0;
  			}
  
  			atomic_set(&data[thr].ready, 1);
  			wake_up(&data[thr].go);

  		}

  		/*
  		 * Wait for more data while we are decompressing.
  		 */
  		if (have < LZO_CMP_PAGES && asked) {
  			ret = hib_wait_on_bio_chain(&bio);
  			if (ret)
  				goto out_finish;
  			have += asked;
  			asked = 0;
  			if (eof)
  				eof = 2;

  		}

  		for (run_threads = thr, thr = 0; thr < run_threads; thr++) {
  			wait_event(data[thr].done,
  			           atomic_read(&data[thr].stop));
  			atomic_set(&data[thr].stop, 0);
  
  			ret = data[thr].ret;

  			if (ret < 0) {
  				printk(KERN_ERR
  				       "PM: LZO decompression failed
  ");
  				goto out_finish;
  			}

  			if (unlikely(!data[thr].unc_len ||
  			             data[thr].unc_len > LZO_UNC_SIZE ||
  			             data[thr].unc_len & (PAGE_SIZE - 1))) {
  				printk(KERN_ERR
  				       "PM: Invalid LZO uncompressed length
  ");
  				ret = -1;

  				goto out_finish;

  			}
  
  			for (off = 0;
  			     off < data[thr].unc_len; off += PAGE_SIZE) {
  				memcpy(data_of(*snapshot),
  				       data[thr].unc + off, PAGE_SIZE);
  
  				if (!(nr_pages % m))
  					printk("\b\b\b\b%3d%%", nr_pages / m);
  				nr_pages++;
  
  				ret = snapshot_write_next(snapshot);
  				if (ret <= 0) {
  					crc->run_threads = thr + 1;
  					atomic_set(&crc->ready, 1);
  					wake_up(&crc->go);
  					goto out_finish;
  				}
  			}

  		}

  
  		crc->run_threads = thr;
  		atomic_set(&crc->ready, 1);
  		wake_up(&crc->go);

  	}
  
  out_finish:

  	if (crc->run_threads) {
  		wait_event(crc->done, atomic_read(&crc->stop));
  		atomic_set(&crc->stop, 0);
  	}

  	do_gettimeofday(&stop);

  	if (!ret) {

  		printk("\b\b\b\bdone
  ");
  		snapshot_write_finalize(snapshot);
  		if (!snapshot_image_loaded(snapshot))

  			ret = -ENODATA;
  		if (!ret) {
  			if (swsusp_header->flags & SF_CRC32_MODE) {
  				if(handle->crc32 != swsusp_header->crc32) {
  					printk(KERN_ERR
  					       "PM: Invalid image CRC32!
  ");
  					ret = -ENODATA;
  				}
  			}
  		}

  	} else
  		printk("
  ");
  	swsusp_show_speed(&start, &stop, nr_to_read, "Read");

  out_clean:
  	for (i = 0; i < ring_size; i++)

  		free_page((unsigned long)page[i]);

  	if (crc) {
  		if (crc->thr)
  			kthread_stop(crc->thr);
  		kfree(crc);
  	}
  	if (data) {
  		for (thr = 0; thr < nr_threads; thr++)
  			if (data[thr].thr)
  				kthread_stop(data[thr].thr);
  		vfree(data);
  	}
  	if (page) vfree(page);

  	return ret;

  }
  
  /**

   *	swsusp_read - read the hibernation image.
   *	@flags_p: flags passed by the "frozen" kernel in the image header should

   *		  be written into this memory location

   */
  
  int swsusp_read(unsigned int *flags_p)

  {
  	int error;
  	struct swap_map_handle handle;
  	struct snapshot_handle snapshot;
  	struct swsusp_info *header;

  	memset(&snapshot, 0, sizeof(struct snapshot_handle));

  	error = snapshot_write_next(&snapshot);

  	if (error < PAGE_SIZE)
  		return error < 0 ? error : -EFAULT;
  	header = (struct swsusp_info *)data_of(snapshot);

  	error = get_swap_reader(&handle, flags_p);
  	if (error)
  		goto end;

  	if (!error)

  		error = swap_read_page(&handle, header, NULL);

  	if (!error) {
  		error = (*flags_p & SF_NOCOMPRESS_MODE) ?
  			load_image(&handle, &snapshot, header->pages - 1) :
  			load_image_lzo(&handle, &snapshot, header->pages - 1);
  	}

  	swap_reader_finish(&handle);
  end:

  	if (!error)

  		pr_debug("PM: Image successfully loaded
  ");

  	else

  		pr_debug("PM: Error %d resuming
  ", error);

  	return error;
  }
  
  /**
   *      swsusp_check - Check for swsusp signature in the resume device
   */
  
  int swsusp_check(void)
  {
  	int error;

  	hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
  					    FMODE_READ, NULL);

  	if (!IS_ERR(hib_resume_bdev)) {
  		set_blocksize(hib_resume_bdev, PAGE_SIZE);

  		clear_page(swsusp_header);

  		error = hib_bio_read_page(swsusp_resume_block,

  					swsusp_header, NULL);

  		if (error)

  			goto put;

  		if (!memcmp(HIBERNATE_SIG, swsusp_header->sig, 10)) {

  			memcpy(swsusp_header->sig, swsusp_header->orig_sig, 10);

  			/* Reset swap signature now */

  			error = hib_bio_write_page(swsusp_resume_block,

  						swsusp_header, NULL);

  		} else {

  			error = -EINVAL;

  		}

  
  put:

  		if (error)

  			blkdev_put(hib_resume_bdev, FMODE_READ);

  		else

  			pr_debug("PM: Image signature found, resuming
  ");

  	} else {

  		error = PTR_ERR(hib_resume_bdev);

  	}
  
  	if (error)

  		pr_debug("PM: Image not found (code %d)
  ", error);

  
  	return error;
  }
  
  /**
   *	swsusp_close - close swap device.
   */

  void swsusp_close(fmode_t mode)

  {

  	if (IS_ERR(hib_resume_bdev)) {

  		pr_debug("PM: Image device not initialised
  ");

  		return;
  	}

  	blkdev_put(hib_resume_bdev, mode);

  }

  
  static int swsusp_header_init(void)
  {
  	swsusp_header = (struct swsusp_header*) __get_free_page(GFP_KERNEL);
  	if (!swsusp_header)
  		panic("Could not allocate memory for swsusp_header
  ");
  	return 0;
  }
  
  core_initcall(swsusp_header_init);