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snapshot.c

/*
 * linux/kernel/power/snapshot.c
 *
 * This file provides system snapshot/restore functionality for swsusp.
 *
 * Copyright (C) 1998-2005 Pavel Machek <pavel@suse.cz>
 * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
 *
 * This file is released under the GPLv2.
 *
 */

#include <linux/version.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/suspend.h>
#include <linux/delay.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/kernel.h>
#include <linux/pm.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/syscalls.h>
#include <linux/console.h>
#include <linux/highmem.h>

#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/io.h>

#include "power.h"

static int swsusp_page_is_free(struct page *);
static void swsusp_set_page_forbidden(struct page *);
static void swsusp_unset_page_forbidden(struct page *);

/* List of PBEs needed for restoring the pages that were allocated before
 * the suspend and included in the suspend image, but have also been
 * allocated by the "resume" kernel, so their contents cannot be written
 * directly to their "original" page frames.
 */
struct pbe *restore_pblist;

/* Pointer to an auxiliary buffer (1 page) */
static void *buffer;

/**
 *    @safe_needed - on resume, for storing the PBE list and the image,
 *    we can only use memory pages that do not conflict with the pages
 *    used before suspend.  The unsafe pages have PageNosaveFree set
 *    and we count them using unsafe_pages.
 *
 *    Each allocated image page is marked as PageNosave and PageNosaveFree
 *    so that swsusp_free() can release it.
 */

#define PG_ANY          0
#define PG_SAFE         1
#define PG_UNSAFE_CLEAR 1
#define PG_UNSAFE_KEEP  0

static unsigned int allocated_unsafe_pages;

static void *get_image_page(gfp_t gfp_mask, int safe_needed)
{
      void *res;

      res = (void *)get_zeroed_page(gfp_mask);
      if (safe_needed)
            while (res && swsusp_page_is_free(virt_to_page(res))) {
                  /* The page is unsafe, mark it for swsusp_free() */
                  swsusp_set_page_forbidden(virt_to_page(res));
                  allocated_unsafe_pages++;
                  res = (void *)get_zeroed_page(gfp_mask);
            }
      if (res) {
            swsusp_set_page_forbidden(virt_to_page(res));
            swsusp_set_page_free(virt_to_page(res));
      }
      return res;
}

unsigned long get_safe_page(gfp_t gfp_mask)
{
      return (unsigned long)get_image_page(gfp_mask, PG_SAFE);
}

static struct page *alloc_image_page(gfp_t gfp_mask)
{
      struct page *page;

      page = alloc_page(gfp_mask);
      if (page) {
            swsusp_set_page_forbidden(page);
            swsusp_set_page_free(page);
      }
      return page;
}

/**
 *    free_image_page - free page represented by @addr, allocated with
 *    get_image_page (page flags set by it must be cleared)
 */

static inline void free_image_page(void *addr, int clear_nosave_free)
{
      struct page *page;

      BUG_ON(!virt_addr_valid(addr));

      page = virt_to_page(addr);

      swsusp_unset_page_forbidden(page);
      if (clear_nosave_free)
            swsusp_unset_page_free(page);

      __free_page(page);
}

/* struct linked_page is used to build chains of pages */

#define LINKED_PAGE_DATA_SIZE (PAGE_SIZE - sizeof(void *))

struct linked_page {
      struct linked_page *next;
      char data[LINKED_PAGE_DATA_SIZE];
} __attribute__((packed));

static inline void
free_list_of_pages(struct linked_page *list, int clear_page_nosave)
{
      while (list) {
            struct linked_page *lp = list->next;

            free_image_page(list, clear_page_nosave);
            list = lp;
      }
}

/**
  *   struct chain_allocator is used for allocating small objects out of
  *   a linked list of pages called 'the chain'.
  *
  *   The chain grows each time when there is no room for a new object in
  *   the current page.  The allocated objects cannot be freed individually.
  *   It is only possible to free them all at once, by freeing the entire
  *   chain.
  *
  *   NOTE: The chain allocator may be inefficient if the allocated objects
  *   are not much smaller than PAGE_SIZE.
  */

00157 struct chain_allocator {
      struct linked_page *chain;    /* the chain */
      unsigned int used_space;      /* total size of objects allocated out
                               * of the current page
                               */
      gfp_t gfp_mask;         /* mask for allocating pages */
      int safe_needed;  /* if set, only "safe" pages are allocated */
};

static void
chain_init(struct chain_allocator *ca, gfp_t gfp_mask, int safe_needed)
{
      ca->chain = NULL;
      ca->used_space = LINKED_PAGE_DATA_SIZE;
      ca->gfp_mask = gfp_mask;
      ca->safe_needed = safe_needed;
}

static void *chain_alloc(struct chain_allocator *ca, unsigned int size)
{
      void *ret;

      if (LINKED_PAGE_DATA_SIZE - ca->used_space < size) {
            struct linked_page *lp;

            lp = get_image_page(ca->gfp_mask, ca->safe_needed);
            if (!lp)
                  return NULL;

            lp->next = ca->chain;
            ca->chain = lp;
            ca->used_space = 0;
      }
      ret = ca->chain->data + ca->used_space;
      ca->used_space += size;
      return ret;
}

static void chain_free(struct chain_allocator *ca, int clear_page_nosave)
{
      free_list_of_pages(ca->chain, clear_page_nosave);
      memset(ca, 0, sizeof(struct chain_allocator));
}

/**
 *    Data types related to memory bitmaps.
 *
 *    Memory bitmap is a structure consiting of many linked lists of
 *    objects.  The main list's elements are of type struct zone_bitmap
 *    and each of them corresonds to one zone.  For each zone bitmap
 *    object there is a list of objects of type struct bm_block that
 *    represent each blocks of bit chunks in which information is
 *    stored.
 *
 *    struct memory_bitmap contains a pointer to the main list of zone
 *    bitmap objects, a struct bm_position used for browsing the bitmap,
 *    and a pointer to the list of pages used for allocating all of the
 *    zone bitmap objects and bitmap block objects.
 *
 *    NOTE: It has to be possible to lay out the bitmap in memory
 *    using only allocations of order 0.  Additionally, the bitmap is
 *    designed to work with arbitrary number of zones (this is over the
 *    top for now, but let's avoid making unnecessary assumptions ;-).
 *
 *    struct zone_bitmap contains a pointer to a list of bitmap block
 *    objects and a pointer to the bitmap block object that has been
 *    most recently used for setting bits.  Additionally, it contains the
 *    pfns that correspond to the start and end of the represented zone.
 *
 *    struct bm_block contains a pointer to the memory page in which
 *    information is stored (in the form of a block of bit chunks
 *    of type unsigned long each).  It also contains the pfns that
 *    correspond to the start and end of the represented memory area and
 *    the number of bit chunks in the block.
 */

#define BM_END_OF_MAP   (~0UL)

#define BM_CHUNKS_PER_BLOCK   (PAGE_SIZE / sizeof(long))
#define BM_BITS_PER_CHUNK     (sizeof(long) << 3)
#define BM_BITS_PER_BLOCK     (PAGE_SIZE << 3)

struct bm_block {
      struct bm_block *next;        /* next element of the list */
      unsigned long start_pfn;      /* pfn represented by the first bit */
      unsigned long end_pfn;  /* pfn represented by the last bit plus 1 */
      unsigned int size;      /* number of bit chunks */
      unsigned long *data;    /* chunks of bits representing pages */
};

struct zone_bitmap {
      struct zone_bitmap *next;     /* next element of the list */
      unsigned long start_pfn;      /* minimal pfn in this zone */
      unsigned long end_pfn;        /* maximal pfn in this zone plus 1 */
      struct bm_block *bm_blocks;   /* list of bitmap blocks */
      struct bm_block *cur_block;   /* recently used bitmap block */
};

/* strcut bm_position is used for browsing memory bitmaps */

struct bm_position {
      struct zone_bitmap *zone_bm;
      struct bm_block *block;
      int chunk;
      int bit;
};

struct memory_bitmap {
      struct zone_bitmap *zone_bm_list;   /* list of zone bitmaps */
      struct linked_page *p_list;   /* list of pages used to store zone
                               * bitmap objects and bitmap block
                               * objects
                               */
      struct bm_position cur; /* most recently used bit position */
};

/* Functions that operate on memory bitmaps */

static inline void memory_bm_reset_chunk(struct memory_bitmap *bm)
{
      bm->cur.chunk = 0;
      bm->cur.bit = -1;
}

static void memory_bm_position_reset(struct memory_bitmap *bm)
{
      struct zone_bitmap *zone_bm;

      zone_bm = bm->zone_bm_list;
      bm->cur.zone_bm = zone_bm;
      bm->cur.block = zone_bm->bm_blocks;
      memory_bm_reset_chunk(bm);
}

static void memory_bm_free(struct memory_bitmap *bm, int clear_nosave_free);

/**
 *    create_bm_block_list - create a list of block bitmap objects
 */

static inline struct bm_block *
create_bm_block_list(unsigned int nr_blocks, struct chain_allocator *ca)
{
      struct bm_block *bblist = NULL;

      while (nr_blocks-- > 0) {
            struct bm_block *bb;

            bb = chain_alloc(ca, sizeof(struct bm_block));
            if (!bb)
                  return NULL;

            bb->next = bblist;
            bblist = bb;
      }
      return bblist;
}

/**
 *    create_zone_bm_list - create a list of zone bitmap objects
 */

static inline struct zone_bitmap *
create_zone_bm_list(unsigned int nr_zones, struct chain_allocator *ca)
{
      struct zone_bitmap *zbmlist = NULL;

      while (nr_zones-- > 0) {
            struct zone_bitmap *zbm;

            zbm = chain_alloc(ca, sizeof(struct zone_bitmap));
            if (!zbm)
                  return NULL;

            zbm->next = zbmlist;
            zbmlist = zbm;
      }
      return zbmlist;
}

/**
  *   memory_bm_create - allocate memory for a memory bitmap
  */

static int
memory_bm_create(struct memory_bitmap *bm, gfp_t gfp_mask, int safe_needed)
{
      struct chain_allocator ca;
      struct zone *zone;
      struct zone_bitmap *zone_bm;
      struct bm_block *bb;
      unsigned int nr;

      chain_init(&ca, gfp_mask, safe_needed);

      /* Compute the number of zones */
      nr = 0;
      for_each_zone(zone)
            if (populated_zone(zone))
                  nr++;

      /* Allocate the list of zones bitmap objects */
      zone_bm = create_zone_bm_list(nr, &ca);
      bm->zone_bm_list = zone_bm;
      if (!zone_bm) {
            chain_free(&ca, PG_UNSAFE_CLEAR);
            return -ENOMEM;
      }

      /* Initialize the zone bitmap objects */
      for_each_zone(zone) {
            unsigned long pfn;

            if (!populated_zone(zone))
                  continue;

            zone_bm->start_pfn = zone->zone_start_pfn;
            zone_bm->end_pfn = zone->zone_start_pfn + zone->spanned_pages;
            /* Allocate the list of bitmap block objects */
            nr = DIV_ROUND_UP(zone->spanned_pages, BM_BITS_PER_BLOCK);
            bb = create_bm_block_list(nr, &ca);
            zone_bm->bm_blocks = bb;
            zone_bm->cur_block = bb;
            if (!bb)
                  goto Free;

            nr = zone->spanned_pages;
            pfn = zone->zone_start_pfn;
            /* Initialize the bitmap block objects */
            while (bb) {
                  unsigned long *ptr;

                  ptr = get_image_page(gfp_mask, safe_needed);
                  bb->data = ptr;
                  if (!ptr)
                        goto Free;

                  bb->start_pfn = pfn;
                  if (nr >= BM_BITS_PER_BLOCK) {
                        pfn += BM_BITS_PER_BLOCK;
                        bb->size = BM_CHUNKS_PER_BLOCK;
                        nr -= BM_BITS_PER_BLOCK;
                  } else {
                        /* This is executed only once in the loop */
                        pfn += nr;
                        bb->size = DIV_ROUND_UP(nr, BM_BITS_PER_CHUNK);
                  }
                  bb->end_pfn = pfn;
                  bb = bb->next;
            }
            zone_bm = zone_bm->next;
      }
      bm->p_list = ca.chain;
      memory_bm_position_reset(bm);
      return 0;

 Free:
      bm->p_list = ca.chain;
      memory_bm_free(bm, PG_UNSAFE_CLEAR);
      return -ENOMEM;
}

/**
  *   memory_bm_free - free memory occupied by the memory bitmap @bm
  */

static void memory_bm_free(struct memory_bitmap *bm, int clear_nosave_free)
{
      struct zone_bitmap *zone_bm;

      /* Free the list of bit blocks for each zone_bitmap object */
      zone_bm = bm->zone_bm_list;
      while (zone_bm) {
            struct bm_block *bb;

            bb = zone_bm->bm_blocks;
            while (bb) {
                  if (bb->data)
                        free_image_page(bb->data, clear_nosave_free);
                  bb = bb->next;
            }
            zone_bm = zone_bm->next;
      }
      free_list_of_pages(bm->p_list, clear_nosave_free);
      bm->zone_bm_list = NULL;
}

/**
 *    memory_bm_find_bit - find the bit in the bitmap @bm that corresponds
 *    to given pfn.  The cur_zone_bm member of @bm and the cur_block member
 *    of @bm->cur_zone_bm are updated.
 */

static void memory_bm_find_bit(struct memory_bitmap *bm, unsigned long pfn,
                        void **addr, unsigned int *bit_nr)
{
      struct zone_bitmap *zone_bm;
      struct bm_block *bb;

      /* Check if the pfn is from the current zone */
      zone_bm = bm->cur.zone_bm;
      if (pfn < zone_bm->start_pfn || pfn >= zone_bm->end_pfn) {
            zone_bm = bm->zone_bm_list;
            /* We don't assume that the zones are sorted by pfns */
            while (pfn < zone_bm->start_pfn || pfn >= zone_bm->end_pfn) {
                  zone_bm = zone_bm->next;

                  BUG_ON(!zone_bm);
            }
            bm->cur.zone_bm = zone_bm;
      }
      /* Check if the pfn corresponds to the current bitmap block */
      bb = zone_bm->cur_block;
      if (pfn < bb->start_pfn)
            bb = zone_bm->bm_blocks;

      while (pfn >= bb->end_pfn) {
            bb = bb->next;

            BUG_ON(!bb);
      }
      zone_bm->cur_block = bb;
      pfn -= bb->start_pfn;
      *bit_nr = pfn % BM_BITS_PER_CHUNK;
      *addr = bb->data + pfn / BM_BITS_PER_CHUNK;
}

static void memory_bm_set_bit(struct memory_bitmap *bm, unsigned long pfn)
{
      void *addr;
      unsigned int bit;

      memory_bm_find_bit(bm, pfn, &addr, &bit);
      set_bit(bit, addr);
}

static void memory_bm_clear_bit(struct memory_bitmap *bm, unsigned long pfn)
{
      void *addr;
      unsigned int bit;

      memory_bm_find_bit(bm, pfn, &addr, &bit);
      clear_bit(bit, addr);
}

static int memory_bm_test_bit(struct memory_bitmap *bm, unsigned long pfn)
{
      void *addr;
      unsigned int bit;

      memory_bm_find_bit(bm, pfn, &addr, &bit);
      return test_bit(bit, addr);
}

/* Two auxiliary functions for memory_bm_next_pfn */

/* Find the first set bit in the given chunk, if there is one */

static inline int next_bit_in_chunk(int bit, unsigned long *chunk_p)
{
      bit++;
      while (bit < BM_BITS_PER_CHUNK) {
            if (test_bit(bit, chunk_p))
                  return bit;

            bit++;
      }
      return -1;
}

/* Find a chunk containing some bits set in given block of bits */

static inline int next_chunk_in_block(int n, struct bm_block *bb)
{
      n++;
      while (n < bb->size) {
            if (bb->data[n])
                  return n;

            n++;
      }
      return -1;
}

/**
 *    memory_bm_next_pfn - find the pfn that corresponds to the next set bit
 *    in the bitmap @bm.  If the pfn cannot be found, BM_END_OF_MAP is
 *    returned.
 *
 *    It is required to run memory_bm_position_reset() before the first call to
 *    this function.
 */

static unsigned long memory_bm_next_pfn(struct memory_bitmap *bm)
{
      struct zone_bitmap *zone_bm;
      struct bm_block *bb;
      int chunk;
      int bit;

      do {
            bb = bm->cur.block;
            do {
                  chunk = bm->cur.chunk;
                  bit = bm->cur.bit;
                  do {
                        bit = next_bit_in_chunk(bit, bb->data + chunk);
                        if (bit >= 0)
                              goto Return_pfn;

                        chunk = next_chunk_in_block(chunk, bb);
                        bit = -1;
                  } while (chunk >= 0);
                  bb = bb->next;
                  bm->cur.block = bb;
                  memory_bm_reset_chunk(bm);
            } while (bb);
            zone_bm = bm->cur.zone_bm->next;
            if (zone_bm) {
                  bm->cur.zone_bm = zone_bm;
                  bm->cur.block = zone_bm->bm_blocks;
                  memory_bm_reset_chunk(bm);
            }
      } while (zone_bm);
      memory_bm_position_reset(bm);
      return BM_END_OF_MAP;

 Return_pfn:
      bm->cur.chunk = chunk;
      bm->cur.bit = bit;
      return bb->start_pfn + chunk * BM_BITS_PER_CHUNK + bit;
}

/**
 *    This structure represents a range of page frames the contents of which
 *    should not be saved during the suspend.
 */

00595 struct nosave_region {
      struct list_head list;
      unsigned long start_pfn;
      unsigned long end_pfn;
};

static LIST_HEAD(nosave_regions);

/**
 *    register_nosave_region - register a range of page frames the contents
 *    of which should not be saved during the suspend (to be used in the early
 *    initialization code)
 */

void __init
__register_nosave_region(unsigned long start_pfn, unsigned long end_pfn,
                   int use_kmalloc)
{
      struct nosave_region *region;

      if (start_pfn >= end_pfn)
            return;

      if (!list_empty(&nosave_regions)) {
            /* Try to extend the previous region (they should be sorted) */
            region = list_entry(nosave_regions.prev,
                              struct nosave_region, list);
            if (region->end_pfn == start_pfn) {
                  region->end_pfn = end_pfn;
                  goto Report;
            }
      }
      if (use_kmalloc) {
            /* during init, this shouldn't fail */
            region = kmalloc(sizeof(struct nosave_region), GFP_KERNEL);
            BUG_ON(!region);
      } else
            /* This allocation cannot fail */
            region = alloc_bootmem_low(sizeof(struct nosave_region));
      region->start_pfn = start_pfn;
      region->end_pfn = end_pfn;
      list_add_tail(&region->list, &nosave_regions);
 Report:
      printk("swsusp: Registered nosave memory region: %016lx - %016lx\n",
            start_pfn << PAGE_SHIFT, end_pfn << PAGE_SHIFT);
}

/*
 * Set bits in this map correspond to the page frames the contents of which
 * should not be saved during the suspend.
 */
static struct memory_bitmap *forbidden_pages_map;

/* Set bits in this map correspond to free page frames. */
static struct memory_bitmap *free_pages_map;

/*
 * Each page frame allocated for creating the image is marked by setting the
 * corresponding bits in forbidden_pages_map and free_pages_map simultaneously
 */

void swsusp_set_page_free(struct page *page)
{
      if (free_pages_map)
            memory_bm_set_bit(free_pages_map, page_to_pfn(page));
}

static int swsusp_page_is_free(struct page *page)
{
      return free_pages_map ?
            memory_bm_test_bit(free_pages_map, page_to_pfn(page)) : 0;
}

void swsusp_unset_page_free(struct page *page)
{
      if (free_pages_map)
            memory_bm_clear_bit(free_pages_map, page_to_pfn(page));
}

static void swsusp_set_page_forbidden(struct page *page)
{
      if (forbidden_pages_map)
            memory_bm_set_bit(forbidden_pages_map, page_to_pfn(page));
}

int swsusp_page_is_forbidden(struct page *page)
{
      return forbidden_pages_map ?
            memory_bm_test_bit(forbidden_pages_map, page_to_pfn(page)) : 0;
}

static void swsusp_unset_page_forbidden(struct page *page)
{
      if (forbidden_pages_map)
            memory_bm_clear_bit(forbidden_pages_map, page_to_pfn(page));
}

/**
 *    mark_nosave_pages - set bits corresponding to the page frames the
 *    contents of which should not be saved in a given bitmap.
 */

static void mark_nosave_pages(struct memory_bitmap *bm)
{
      struct nosave_region *region;

      if (list_empty(&nosave_regions))
            return;

      list_for_each_entry(region, &nosave_regions, list) {
            unsigned long pfn;

            printk("swsusp: Marking nosave pages: %016lx - %016lx\n",
                        region->start_pfn << PAGE_SHIFT,
                        region->end_pfn << PAGE_SHIFT);

            for (pfn = region->start_pfn; pfn < region->end_pfn; pfn++)
                  if (pfn_valid(pfn))
                        memory_bm_set_bit(bm, pfn);
      }
}

/**
 *    create_basic_memory_bitmaps - create bitmaps needed for marking page
 *    frames that should not be saved and free page frames.  The pointers
 *    forbidden_pages_map and free_pages_map are only modified if everything
 *    goes well, because we don't want the bits to be used before both bitmaps
 *    are set up.
 */

int create_basic_memory_bitmaps(void)
{
      struct memory_bitmap *bm1, *bm2;
      int error = 0;

      BUG_ON(forbidden_pages_map || free_pages_map);

      bm1 = kzalloc(sizeof(struct memory_bitmap), GFP_KERNEL);
      if (!bm1)
            return -ENOMEM;

      error = memory_bm_create(bm1, GFP_KERNEL, PG_ANY);
      if (error)
            goto Free_first_object;

      bm2 = kzalloc(sizeof(struct memory_bitmap), GFP_KERNEL);
      if (!bm2)
            goto Free_first_bitmap;

      error = memory_bm_create(bm2, GFP_KERNEL, PG_ANY);
      if (error)
            goto Free_second_object;

      forbidden_pages_map = bm1;
      free_pages_map = bm2;
      mark_nosave_pages(forbidden_pages_map);

      printk("swsusp: Basic memory bitmaps created\n");

      return 0;

 Free_second_object:
      kfree(bm2);
 Free_first_bitmap:
      memory_bm_free(bm1, PG_UNSAFE_CLEAR);
 Free_first_object:
      kfree(bm1);
      return -ENOMEM;
}

/**
 *    free_basic_memory_bitmaps - free memory bitmaps allocated by
 *    create_basic_memory_bitmaps().  The auxiliary pointers are necessary
 *    so that the bitmaps themselves are not referred to while they are being
 *    freed.
 */

void free_basic_memory_bitmaps(void)
{
      struct memory_bitmap *bm1, *bm2;

      BUG_ON(!(forbidden_pages_map && free_pages_map));

      bm1 = forbidden_pages_map;
      bm2 = free_pages_map;
      forbidden_pages_map = NULL;
      free_pages_map = NULL;
      memory_bm_free(bm1, PG_UNSAFE_CLEAR);
      kfree(bm1);
      memory_bm_free(bm2, PG_UNSAFE_CLEAR);
      kfree(bm2);

      printk("swsusp: Basic memory bitmaps freed\n");
}

/**
 *    snapshot_additional_pages - estimate the number of additional pages
 *    be needed for setting up the suspend image data structures for given
 *    zone (usually the returned value is greater than the exact number)
 */

unsigned int snapshot_additional_pages(struct zone *zone)
{
      unsigned int res;

      res = DIV_ROUND_UP(zone->spanned_pages, BM_BITS_PER_BLOCK);
      res += DIV_ROUND_UP(res * sizeof(struct bm_block), PAGE_SIZE);
      return 2 * res;
}

#ifdef CONFIG_HIGHMEM
/**
 *    count_free_highmem_pages - compute the total number of free highmem
 *    pages, system-wide.
 */

static unsigned int count_free_highmem_pages(void)
{
      struct zone *zone;
      unsigned int cnt = 0;

      for_each_zone(zone)
            if (populated_zone(zone) && is_highmem(zone))
                  cnt += zone_page_state(zone, NR_FREE_PAGES);

      return cnt;
}

/**
 *    saveable_highmem_page - Determine whether a highmem page should be
 *    included in the suspend image.
 *
 *    We should save the page if it isn't Nosave or NosaveFree, or Reserved,
 *    and it isn't a part of a free chunk of pages.
 */

static struct page *saveable_highmem_page(unsigned long pfn)
{
      struct page *page;

      if (!pfn_valid(pfn))
            return NULL;

      page = pfn_to_page(pfn);

      BUG_ON(!PageHighMem(page));

      if (swsusp_page_is_forbidden(page) ||  swsusp_page_is_free(page) ||
          PageReserved(page))
            return NULL;

      return page;
}

/**
 *    count_highmem_pages - compute the total number of saveable highmem
 *    pages.
 */

unsigned int count_highmem_pages(void)
{
      struct zone *zone;
      unsigned int n = 0;

      for_each_zone(zone) {
            unsigned long pfn, max_zone_pfn;

            if (!is_highmem(zone))
                  continue;

            mark_free_pages(zone);
            max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
            for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
                  if (saveable_highmem_page(pfn))
                        n++;
      }
      return n;
}
#else
static inline void *saveable_highmem_page(unsigned long pfn) { return NULL; }
static inline unsigned int count_highmem_pages(void) { return 0; }
#endif /* CONFIG_HIGHMEM */

/**
 *    saveable - Determine whether a non-highmem page should be included in
 *    the suspend image.
 *
 *    We should save the page if it isn't Nosave, and is not in the range
 *    of pages statically defined as 'unsaveable', and it isn't a part of
 *    a free chunk of pages.
 */

static struct page *saveable_page(unsigned long pfn)
{
      struct page *page;

      if (!pfn_valid(pfn))
            return NULL;

      page = pfn_to_page(pfn);

      BUG_ON(PageHighMem(page));

      if (swsusp_page_is_forbidden(page) || swsusp_page_is_free(page))
            return NULL;

      if (PageReserved(page) && pfn_is_nosave(pfn))
            return NULL;

      return page;
}

/**
 *    count_data_pages - compute the total number of saveable non-highmem
 *    pages.
 */

unsigned int count_data_pages(void)
{
      struct zone *zone;
      unsigned long pfn, max_zone_pfn;
      unsigned int n = 0;

      for_each_zone(zone) {
            if (is_highmem(zone))
                  continue;

            mark_free_pages(zone);
            max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
            for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
                  if(saveable_page(pfn))
                        n++;
      }
      return n;
}

/* This is needed, because copy_page and memcpy are not usable for copying
 * task structs.
 */
static inline void do_copy_page(long *dst, long *src)
{
      int n;

      for (n = PAGE_SIZE / sizeof(long); n; n--)
            *dst++ = *src++;
}

#ifdef CONFIG_HIGHMEM
static inline struct page *
page_is_saveable(struct zone *zone, unsigned long pfn)
{
      return is_highmem(zone) ?
                  saveable_highmem_page(pfn) : saveable_page(pfn);
}

static inline void
copy_data_page(unsigned long dst_pfn, unsigned long src_pfn)
{
      struct page *s_page, *d_page;
      void *src, *dst;

      s_page = pfn_to_page(src_pfn);
      d_page = pfn_to_page(dst_pfn);
      if (PageHighMem(s_page)) {
            src = kmap_atomic(s_page, KM_USER0);
            dst = kmap_atomic(d_page, KM_USER1);
            do_copy_page(dst, src);
            kunmap_atomic(src, KM_USER0);
            kunmap_atomic(dst, KM_USER1);
      } else {
            src = page_address(s_page);
            if (PageHighMem(d_page)) {
                  /* Page pointed to by src may contain some kernel
                   * data modified by kmap_atomic()
                   */
                  do_copy_page(buffer, src);
                  dst = kmap_atomic(pfn_to_page(dst_pfn), KM_USER0);
                  memcpy(dst, buffer, PAGE_SIZE);
                  kunmap_atomic(dst, KM_USER0);
            } else {
                  dst = page_address(d_page);
                  do_copy_page(dst, src);
            }
      }
}
#else
#define page_is_saveable(zone, pfn) saveable_page(pfn)

static inline void
copy_data_page(unsigned long dst_pfn, unsigned long src_pfn)
{
      do_copy_page(page_address(pfn_to_page(dst_pfn)),
                  page_address(pfn_to_page(src_pfn)));
}
#endif /* CONFIG_HIGHMEM */

static void
copy_data_pages(struct memory_bitmap *copy_bm, struct memory_bitmap *orig_bm)
{
      struct zone *zone;
      unsigned long pfn;

      for_each_zone(zone) {
            unsigned long max_zone_pfn;

            mark_free_pages(zone);
            max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
            for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
                  if (page_is_saveable(zone, pfn))
                        memory_bm_set_bit(orig_bm, pfn);
      }
      memory_bm_position_reset(orig_bm);
      memory_bm_position_reset(copy_bm);
      for(;;) {
            pfn = memory_bm_next_pfn(orig_bm);
            if (unlikely(pfn == BM_END_OF_MAP))
                  break;
            copy_data_page(memory_bm_next_pfn(copy_bm), pfn);
      }
}

/* Total number of image pages */
static unsigned int nr_copy_pages;
/* Number of pages needed for saving the original pfns of the image pages */
static unsigned int nr_meta_pages;

/**
 *    swsusp_free - free pages allocated for the suspend.
 *
 *    Suspend pages are alocated before the atomic copy is made, so we
 *    need to release them after the resume.
 */

void swsusp_free(void)
{
      struct zone *zone;
      unsigned long pfn, max_zone_pfn;

      for_each_zone(zone) {
            max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
            for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
                  if (pfn_valid(pfn)) {
                        struct page *page = pfn_to_page(pfn);

                        if (swsusp_page_is_forbidden(page) &&
                            swsusp_page_is_free(page)) {
                              swsusp_unset_page_forbidden(page);
                              swsusp_unset_page_free(page);
                              __free_page(page);
                        }
                  }
      }
      nr_copy_pages = 0;
      nr_meta_pages = 0;
      restore_pblist = NULL;
      buffer = NULL;
}

#ifdef CONFIG_HIGHMEM
/**
  *   count_pages_for_highmem - compute the number of non-highmem pages
  *   that will be necessary for creating copies of highmem pages.
  */

static unsigned int count_pages_for_highmem(unsigned int nr_highmem)
{
      unsigned int free_highmem = count_free_highmem_pages();

      if (free_highmem >= nr_highmem)
            nr_highmem = 0;
      else
            nr_highmem -= free_highmem;

      return nr_highmem;
}
#else
static unsigned int
count_pages_for_highmem(unsigned int nr_highmem) { return 0; }
#endif /* CONFIG_HIGHMEM */

/**
 *    enough_free_mem - Make sure we have enough free memory for the
 *    snapshot image.
 */

static int enough_free_mem(unsigned int nr_pages, unsigned int nr_highmem)
{
      struct zone *zone;
      unsigned int free = 0, meta = 0;

      for_each_zone(zone) {
            meta += snapshot_additional_pages(zone);
            if (!is_highmem(zone))
                  free += zone_page_state(zone, NR_FREE_PAGES);
      }

      nr_pages += count_pages_for_highmem(nr_highmem);
      pr_debug("swsusp: Normal pages needed: %u + %u + %u, available pages: %u\n",
            nr_pages, PAGES_FOR_IO, meta, free);

      return free > nr_pages + PAGES_FOR_IO + meta;
}

#ifdef CONFIG_HIGHMEM
/**
 *    get_highmem_buffer - if there are some highmem pages in the suspend
 *    image, we may need the buffer to copy them and/or load their data.
 */

static inline int get_highmem_buffer(int safe_needed)
{
      buffer = get_image_page(GFP_ATOMIC | __GFP_COLD, safe_needed);
      return buffer ? 0 : -ENOMEM;
}

/**
 *    alloc_highmem_image_pages - allocate some highmem pages for the image.
 *    Try to allocate as many pages as needed, but if the number of free
 *    highmem pages is lesser than that, allocate them all.
 */

static inline unsigned int
alloc_highmem_image_pages(struct memory_bitmap *bm, unsigned int nr_highmem)
{
      unsigned int to_alloc = count_free_highmem_pages();

      if (to_alloc > nr_highmem)
            to_alloc = nr_highmem;

      nr_highmem -= to_alloc;
      while (to_alloc-- > 0) {
            struct page *page;

            page = alloc_image_page(__GFP_HIGHMEM);
            memory_bm_set_bit(bm, page_to_pfn(page));
      }
      return nr_highmem;
}
#else
static inline int get_highmem_buffer(int safe_needed) { return 0; }

static inline unsigned int
alloc_highmem_image_pages(struct memory_bitmap *bm, unsigned int n) { return 0; }
#endif /* CONFIG_HIGHMEM */

/**
 *    swsusp_alloc - allocate memory for the suspend image
 *
 *    We first try to allocate as many highmem pages as there are
 *    saveable highmem pages in the system.  If that fails, we allocate
 *    non-highmem pages for the copies of the remaining highmem ones.
 *
 *    In this approach it is likely that the copies of highmem pages will
 *    also be located in the high memory, because of the way in which
 *    copy_data_pages() works.
 */

static int
swsusp_alloc(struct memory_bitmap *orig_bm, struct memory_bitmap *copy_bm,
            unsigned int nr_pages, unsigned int nr_highmem)
{
      int error;

      error = memory_bm_create(orig_bm, GFP_ATOMIC | __GFP_COLD, PG_ANY);
      if (error)
            goto Free;

      error = memory_bm_create(copy_bm, GFP_ATOMIC | __GFP_COLD, PG_ANY);
      if (error)
            goto Free;

      if (nr_highmem > 0) {
            error = get_highmem_buffer(PG_ANY);
            if (error)
                  goto Free;

            nr_pages += alloc_highmem_image_pages(copy_bm, nr_highmem);
      }
      while (nr_pages-- > 0) {
            struct page *page = alloc_image_page(GFP_ATOMIC | __GFP_COLD);

            if (!page)
                  goto Free;

            memory_bm_set_bit(copy_bm, page_to_pfn(page));
      }
      return 0;

 Free:
      swsusp_free();
      return -ENOMEM;
}

/* Memory bitmap used for marking saveable pages (during suspend) or the
 * suspend image pages (during resume)
 */
static struct memory_bitmap orig_bm;
/* Memory bitmap used on suspend for marking allocated pages that will contain
 * the copies of saveable pages.  During resume it is initially used for
 * marking the suspend image pages, but then its set bits are duplicated in
 * @orig_bm and it is released.  Next, on systems with high memory, it may be
 * used for marking "safe" highmem pages, but it has to be reinitialized for
 * this purpose.
 */
static struct memory_bitmap copy_bm;

asmlinkage int swsusp_save(void)
{
      unsigned int nr_pages, nr_highmem;

      printk("swsusp: critical section: \n");

      drain_local_pages();
      nr_pages = count_data_pages();
      nr_highmem = count_highmem_pages();
      printk("swsusp: Need to copy %u pages\n", nr_pages + nr_highmem);

      if (!enough_free_mem(nr_pages, nr_highmem)) {
            printk(KERN_ERR "swsusp: Not enough free memory\n");
            return -ENOMEM;
      }

      if (swsusp_alloc(&orig_bm, &copy_bm, nr_pages, nr_highmem)) {
            printk(KERN_ERR "swsusp: Memory allocation failed\n");
            return -ENOMEM;
      }

      /* During allocating of suspend pagedir, new cold pages may appear.
       * Kill them.
       */
      drain_local_pages();
      copy_data_pages(&copy_bm, &orig_bm);

      /*
       * End of critical section. From now on, we can write to memory,
       * but we should not touch disk. This specially means we must _not_
       * touch swap space! Except we must write out our image of course.
       */

      nr_pages += nr_highmem;
      nr_copy_pages = nr_pages;
      nr_meta_pages = DIV_ROUND_UP(nr_pages * sizeof(long), PAGE_SIZE);

      printk("swsusp: critical section: done (%d pages copied)\n", nr_pages);

      return 0;
}

#ifndef CONFIG_ARCH_HIBERNATION_HEADER
static int init_header_complete(struct swsusp_info *info)
{
      memcpy(&info->uts, init_utsname(), sizeof(struct new_utsname));
      info->version_code = LINUX_VERSION_CODE;
      return 0;
}

static char *check_image_kernel(struct swsusp_info *info)
{
      if (info->version_code != LINUX_VERSION_CODE)
            return "kernel version";
      if (strcmp(info->uts.sysname,init_utsname()->sysname))
            return "system type";
      if (strcmp(info->uts.release,init_utsname()->release))
            return "kernel release";
      if (strcmp(info->uts.version,init_utsname()->version))
            return "version";
      if (strcmp(info->uts.machine,init_utsname()->machine))
            return "machine";
      return NULL;
}
#endif /* CONFIG_ARCH_HIBERNATION_HEADER */

static int init_header(struct swsusp_info *info)
{
      memset(info, 0, sizeof(struct swsusp_info));
      info->num_physpages = num_physpages;
      info->image_pages = nr_copy_pages;
      info->pages = nr_copy_pages + nr_meta_pages + 1;
      info->size = info->pages;
      info->size <<= PAGE_SHIFT;
      return init_header_complete(info);
}

/**
 *    pack_pfns - pfns corresponding to the set bits found in the bitmap @bm
 *    are stored in the array @buf[] (1 page at a time)
 */

static inline void
pack_pfns(unsigned long *buf, struct memory_bitmap *bm)
{
      int j;

      for (j = 0; j < PAGE_SIZE / sizeof(long); j++) {
            buf[j] = memory_bm_next_pfn(bm);
            if (unlikely(buf[j] == BM_END_OF_MAP))
                  break;
      }
}

/**
 *    snapshot_read_next - used for reading the system memory snapshot.
 *
 *    On the first call to it @handle should point to a zeroed
 *    snapshot_handle structure.  The structure gets updated and a pointer
 *    to it should be passed to this function every next time.
 *
 *    The @count parameter should contain the number of bytes the caller
 *    wants to read from the snapshot.  It must not be zero.
 *
 *    On success the function returns a positive number.  Then, the caller
 *    is allowed to read up to the returned number of bytes from the memory
 *    location computed by the data_of() macro.  The number returned
 *    may be smaller than @count, but this only happens if the read would
 *    cross a page boundary otherwise.
 *
 *    The function returns 0 to indicate the end of data stream condition,
 *    and a negative number is returned on error.  In such cases the
 *    structure pointed to by @handle is not updated and should not be used
 *    any more.
 */

int snapshot_read_next(struct snapshot_handle *handle, size_t count)
{
      if (handle->cur > nr_meta_pages + nr_copy_pages)
            return 0;

      if (!buffer) {
            /* This makes the buffer be freed by swsusp_free() */
            buffer = get_image_page(GFP_ATOMIC, PG_ANY);
            if (!buffer)
                  return -ENOMEM;
      }
      if (!handle->offset) {
            int error;

            error = init_header((struct swsusp_info *)buffer);
            if (error)
                  return error;
            handle->buffer = buffer;
            memory_bm_position_reset(&orig_bm);
            memory_bm_position_reset(&copy_bm);
      }
      if (handle->prev < handle->cur) {
            if (handle->cur <= nr_meta_pages) {
                  memset(buffer, 0, PAGE_SIZE);
                  pack_pfns(buffer, &orig_bm);
            } else {
                  struct page *page;

                  page = pfn_to_page(memory_bm_next_pfn(&copy_bm));
                  if (PageHighMem(page)) {
                        /* Highmem pages are copied to the buffer,
                         * because we can't return with a kmapped
                         * highmem page (we may not be called again).
                         */
                        void *kaddr;

                        kaddr = kmap_atomic(page, KM_USER0);
                        memcpy(buffer, kaddr, PAGE_SIZE);
                        kunmap_atomic(kaddr, KM_USER0);
                        handle->buffer = buffer;
                  } else {
                        handle->buffer = page_address(page);
                  }
            }
            handle->prev = handle->cur;
      }
      handle->buf_offset = handle->cur_offset;
      if (handle->cur_offset + count >= PAGE_SIZE) {
            count = PAGE_SIZE - handle->cur_offset;
            handle->cur_offset = 0;
            handle->cur++;
      } else {
            handle->cur_offset += count;
      }
      handle->offset += count;
      return count;
}

/**
 *    mark_unsafe_pages - mark the pages that cannot be used for storing
 *    the image during resume, because they conflict with the pages that
 *    had been used before suspend
 */

static int mark_unsafe_pages(struct memory_bitmap *bm)
{
      struct zone *zone;
      unsigned long pfn, max_zone_pfn;

      /* Clear page flags */
      for_each_zone(zone) {
            max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
            for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
                  if (pfn_valid(pfn))
                        swsusp_unset_page_free(pfn_to_page(pfn));
      }

      /* Mark pages that correspond to the "original" pfns as "unsafe" */
      memory_bm_position_reset(bm);
      do {
            pfn = memory_bm_next_pfn(bm);
            if (likely(pfn != BM_END_OF_MAP)) {
                  if (likely(pfn_valid(pfn)))
                        swsusp_set_page_free(pfn_to_page(pfn));
                  else
                        return -EFAULT;
            }
      } while (pfn != BM_END_OF_MAP);

      allocated_unsafe_pages = 0;

      return 0;
}

static void
duplicate_memory_bitmap(struct memory_bitmap *dst, struct memory_bitmap *src)
{
      unsigned long pfn;

      memory_bm_position_reset(src);
      pfn = memory_bm_next_pfn(src);
      while (pfn != BM_END_OF_MAP) {
            memory_bm_set_bit(dst, pfn);
            pfn = memory_bm_next_pfn(src);
      }
}

static int check_header(struct swsusp_info *info)
{
      char *reason;

      reason = check_image_kernel(info);
      if (!reason && info->num_physpages != num_physpages)
            reason = "memory size";
      if (reason) {
            printk(KERN_ERR "swsusp: Resume mismatch: %s\n", reason);
            return -EPERM;
      }
      return 0;
}

/**
 *    load header - check the image header and copy data from it
 */

static int
load_header(struct swsusp_info *info)
{
      int error;

      restore_pblist = NULL;
      error = check_header(info);
      if (!error) {
            nr_copy_pages = info->image_pages;
            nr_meta_pages = info->pages - info->image_pages - 1;
      }
      return error;
}

/**
 *    unpack_orig_pfns - for each element of @buf[] (1 page at a time) set
 *    the corresponding bit in the memory bitmap @bm
 */

static inline void
unpack_orig_pfns(unsigned long *buf, struct memory_bitmap *bm)
{
      int j;

      for (j = 0; j < PAGE_SIZE / sizeof(long); j++) {
            if (unlikely(buf[j] == BM_END_OF_MAP))
                  break;

            memory_bm_set_bit(bm, buf[j]);
      }
}

/* List of "safe" pages that may be used to store data loaded from the suspend
 * image
 */
static struct linked_page *safe_pages_list;

#ifdef CONFIG_HIGHMEM
/* struct highmem_pbe is used for creating the list of highmem pages that
 * should be restored atomically during the resume from disk, because the page
 * frames they have occupied before the suspend are in use.
 */
struct highmem_pbe {
      struct page *copy_page; /* data is here now */
      struct page *orig_page; /* data was here before the suspend */
      struct highmem_pbe *next;
};

/* List of highmem PBEs needed for restoring the highmem pages that were
 * allocated before the suspend and included in the suspend image, but have
 * also been allocated by the "resume" kernel, so their contents cannot be
 * written directly to their "original" page frames.
 */
static struct highmem_pbe *highmem_pblist;

/**
 *    count_highmem_image_pages - compute the number of highmem pages in the
 *    suspend image.  The bits in the memory bitmap @bm that correspond to the
 *    image pages are assumed to be set.
 */

static unsigned int count_highmem_image_pages(struct memory_bitmap *bm)
{
      unsigned long pfn;
      unsigned int cnt = 0;

      memory_bm_position_reset(bm);
      pfn = memory_bm_next_pfn(bm);
      while (pfn != BM_END_OF_MAP) {
            if (PageHighMem(pfn_to_page(pfn)))
                  cnt++;

            pfn = memory_bm_next_pfn(bm);
      }
      return cnt;
}

/**
 *    prepare_highmem_image - try to allocate as many highmem pages as
 *    there are highmem image pages (@nr_highmem_p points to the variable
 *    containing the number of highmem image pages).  The pages that are
 *    "safe" (ie. will not be overwritten when the suspend image is
 *    restored) have the corresponding bits set in @bm (it must be
 *    unitialized).
 *
 *    NOTE: This function should not be called if there are no highmem
 *    image pages.
 */

static unsigned int safe_highmem_pages;

static struct memory_bitmap *safe_highmem_bm;

static int
prepare_highmem_image(struct memory_bitmap *bm, unsigned int *nr_highmem_p)
{
      unsigned int to_alloc;

      if (memory_bm_create(bm, GFP_ATOMIC, PG_SAFE))
            return -ENOMEM;

      if (get_highmem_buffer(PG_SAFE))
            return -ENOMEM;

      to_alloc = count_free_highmem_pages();
      if (to_alloc > *nr_highmem_p)
            to_alloc = *nr_highmem_p;
      else
            *nr_highmem_p = to_alloc;

      safe_highmem_pages = 0;
      while (to_alloc-- > 0) {
            struct page *page;

            page = alloc_page(__GFP_HIGHMEM);
            if (!swsusp_page_is_free(page)) {
                  /* The page is "safe", set its bit the bitmap */
                  memory_bm_set_bit(bm, page_to_pfn(page));
                  safe_highmem_pages++;
            }
            /* Mark the page as allocated */
            swsusp_set_page_forbidden(page);
            swsusp_set_page_free(page);
      }
      memory_bm_position_reset(bm);
      safe_highmem_bm = bm;
      return 0;
}

/**
 *    get_highmem_page_buffer - for given highmem image page find the buffer
 *    that suspend_write_next() should set for its caller to write to.
 *
 *    If the page is to be saved to its "original" page frame or a copy of
 *    the page is to be made in the highmem, @buffer is returned.  Otherwise,
 *    the copy of the page is to be made in normal memory, so the address of
 *    the copy is returned.
 *
 *    If @buffer is returned, the caller of suspend_write_next() will write
 *    the page's contents to @buffer, so they will have to be copied to the
 *    right location on the next call to suspend_write_next() and it is done
 *    with the help of copy_last_highmem_page().  For this purpose, if
 *    @buffer is returned, @last_highmem page is set to the page to which
 *    the data will have to be copied from @buffer.
 */

static struct page *last_highmem_page;

static void *
get_highmem_page_buffer(struct page *page, struct chain_allocator *ca)
{
      struct highmem_pbe *pbe;
      void *kaddr;

      if (swsusp_page_is_forbidden(page) && swsusp_page_is_free(page)) {
            /* We have allocated the "original" page frame and we can
             * use it directly to store the loaded page.
             */
            last_highmem_page = page;
            return buffer;
      }
      /* The "original" page frame has not been allocated and we have to
       * use a "safe" page frame to store the loaded page.
       */
      pbe = chain_alloc(ca, sizeof(struct highmem_pbe));
      if (!pbe) {
            swsusp_free();
            return NULL;
      }
      pbe->orig_page = page;
      if (safe_highmem_pages > 0) {
            struct page *tmp;

            /* Copy of the page will be stored in high memory */
            kaddr = buffer;
            tmp = pfn_to_page(memory_bm_next_pfn(safe_highmem_bm));
            safe_highmem_pages--;
            last_highmem_page = tmp;
            pbe->copy_page = tmp;
      } else {
            /* Copy of the page will be stored in normal memory */
            kaddr = safe_pages_list;
            safe_pages_list = safe_pages_list->next;
            pbe->copy_page = virt_to_page(kaddr);
      }
      pbe->next = highmem_pblist;
      highmem_pblist = pbe;
      return kaddr;
}

/**
 *    copy_last_highmem_page - copy the contents of a highmem image from
 *    @buffer, where the caller of snapshot_write_next() has place them,
 *    to the right location represented by @last_highmem_page .
 */

static void copy_last_highmem_page(void)
{
      if (last_highmem_page) {
            void *dst;

            dst = kmap_atomic(last_highmem_page, KM_USER0);
            memcpy(dst, buffer, PAGE_SIZE);
            kunmap_atomic(dst, KM_USER0);
            last_highmem_page = NULL;
      }
}

static inline int last_highmem_page_copied(void)
{
      return !last_highmem_page;
}

static inline void free_highmem_data(void)
{
      if (safe_highmem_bm)
            memory_bm_free(safe_highmem_bm, PG_UNSAFE_CLEAR);

      if (buffer)
            free_image_page(buffer, PG_UNSAFE_CLEAR);
}
#else
static inline int get_safe_write_buffer(void) { return 0; }

static unsigned int
count_highmem_image_pages(struct memory_bitmap *bm) { return 0; }

static inline int
prepare_highmem_image(struct memory_bitmap *bm, unsigned int *nr_highmem_p)
{
      return 0;
}

static inline void *
get_highmem_page_buffer(struct page *page, struct chain_allocator *ca)
{
      return NULL;
}

static inline void copy_last_highmem_page(void) {}
static inline int last_highmem_page_copied(void) { return 1; }
static inline void free_highmem_data(void) {}
#endif /* CONFIG_HIGHMEM */

/**
 *    prepare_image - use the memory bitmap @bm to mark the pages that will
 *    be overwritten in the process of restoring the system memory state
 *    from the suspend image ("unsafe" pages) and allocate memory for the
 *    image.
 *
 *    The idea is to allocate a new memory bitmap first and then allocate
 *    as many pages as needed for the image data, but not to assign these
 *    pages to specific tasks initially.  Instead, we just mark them as
 *    allocated and create a lists of "safe" pages that will be used
 *    later.  On systems with high memory a list of "safe" highmem pages is
 *    also created.
 */

#define PBES_PER_LINKED_PAGE  (LINKED_PAGE_DATA_SIZE / sizeof(struct pbe))

static int
prepare_image(struct memory_bitmap *new_bm, struct memory_bitmap *bm)
{
      unsigned int nr_pages, nr_highmem;
      struct linked_page *sp_list, *lp;
      int error;

      /* If there is no highmem, the buffer will not be necessary */
      free_image_page(buffer, PG_UNSAFE_CLEAR);
      buffer = NULL;

      nr_highmem = count_highmem_image_pages(bm);
      error = mark_unsafe_pages(bm);
      if (error)
            goto Free;

      error = memory_bm_create(new_bm, GFP_ATOMIC, PG_SAFE);
      if (error)
            goto Free;

      duplicate_memory_bitmap(new_bm, bm);
      memory_bm_free(bm, PG_UNSAFE_KEEP);
      if (nr_highmem > 0) {
            error = prepare_highmem_image(bm, &nr_highmem);
            if (error)
                  goto Free;
      }
      /* Reserve some safe pages for potential later use.
       *
       * NOTE: This way we make sure there will be enough safe pages for the
       * chain_alloc() in get_buffer().  It is a bit wasteful, but
       * nr_copy_pages cannot be greater than 50% of the memory anyway.
       */
      sp_list = NULL;
      /* nr_copy_pages cannot be lesser than allocated_unsafe_pages */
      nr_pages = nr_copy_pages - nr_highmem - allocated_unsafe_pages;
      nr_pages = DIV_ROUND_UP(nr_pages, PBES_PER_LINKED_PAGE);
      while (nr_pages > 0) {
            lp = get_image_page(GFP_ATOMIC, PG_SAFE);
            if (!lp) {
                  error = -ENOMEM;
                  goto Free;
            }
            lp->next = sp_list;
            sp_list = lp;
            nr_pages--;
      }
      /* Preallocate memory for the image */
      safe_pages_list = NULL;
      nr_pages = nr_copy_pages - nr_highmem - allocated_unsafe_pages;
      while (nr_pages > 0) {
            lp = (struct linked_page *)get_zeroed_page(GFP_ATOMIC);
            if (!lp) {
                  error = -ENOMEM;
                  goto Free;
            }
            if (!swsusp_page_is_free(virt_to_page(lp))) {
                  /* The page is "safe", add it to the list */
                  lp->next = safe_pages_list;
                  safe_pages_list = lp;
            }
            /* Mark the page as allocated */
            swsusp_set_page_forbidden(virt_to_page(lp));
            swsusp_set_page_free(virt_to_page(lp));
            nr_pages--;
      }
      /* Free the reserved safe pages so that chain_alloc() can use them */
      while (sp_list) {
            lp = sp_list->next;
            free_image_page(sp_list, PG_UNSAFE_CLEAR);
            sp_list = lp;
      }
      return 0;

 Free:
      swsusp_free();
      return error;
}

/**
 *    get_buffer - compute the address that snapshot_write_next() should
 *    set for its caller to write to.
 */

static void *get_buffer(struct memory_bitmap *bm, struct chain_allocator *ca)
{
      struct pbe *pbe;
      struct page *page = pfn_to_page(memory_bm_next_pfn(bm));

      if (PageHighMem(page))
            return get_highmem_page_buffer(page, ca);

      if (swsusp_page_is_forbidden(page) && swsusp_page_is_free(page))
            /* We have allocated the "original" page frame and we can
             * use it directly to store the loaded page.
             */
            return page_address(page);

      /* The "original" page frame has not been allocated and we have to
       * use a "safe" page frame to store the loaded page.
       */
      pbe = chain_alloc(ca, sizeof(struct pbe));
      if (!pbe) {
            swsusp_free();
            return NULL;
      }
      pbe->orig_address = page_address(page);
      pbe->address = safe_pages_list;
      safe_pages_list = safe_pages_list->next;
      pbe->next = restore_pblist;
      restore_pblist = pbe;
      return pbe->address;
}

/**
 *    snapshot_write_next - used for writing the system memory snapshot.
 *
 *    On the first call to it @handle should point to a zeroed
 *    snapshot_handle structure.  The structure gets updated and a pointer
 *    to it should be passed to this function every next time.
 *
 *    The @count parameter should contain the number of bytes the caller
 *    wants to write to the image.  It must not be zero.
 *
 *    On success the function returns a positive number.  Then, the caller
 *    is allowed to write up to the returned number of bytes to the memory
 *    location computed by the data_of() macro.  The number returned
 *    may be smaller than @count, but this only happens if the write would
 *    cross a page boundary otherwise.
 *
 *    The function returns 0 to indicate the "end of file" condition,
 *    and a negative number is returned on error.  In such cases the
 *    structure pointed to by @handle is not updated and should not be used
 *    any more.
 */

int snapshot_write_next(struct snapshot_handle *handle, size_t count)
{
      static struct chain_allocator ca;
      int error = 0;

      /* Check if we have already loaded the entire image */
      if (handle->prev && handle->cur > nr_meta_pages + nr_copy_pages)
            return 0;

      if (handle->offset == 0) {
            if (!buffer)
                  /* This makes the buffer be freed by swsusp_free() */
                  buffer = get_image_page(GFP_ATOMIC, PG_ANY);

            if (!buffer)
                  return -ENOMEM;

            handle->buffer = buffer;
      }
      handle->sync_read = 1;
      if (handle->prev < handle->cur) {
            if (handle->prev == 0) {
                  error = load_header(buffer);
                  if (error)
                        return error;

                  error = memory_bm_create(&copy_bm, GFP_ATOMIC, PG_ANY);
                  if (error)
                        return error;

            } else if (handle->prev <= nr_meta_pages) {
                  unpack_orig_pfns(buffer, &copy_bm);
                  if (handle->prev == nr_meta_pages) {
                        error = prepare_image(&orig_bm, &copy_bm);
                        if (error)
                              return error;

                        chain_init(&ca, GFP_ATOMIC, PG_SAFE);
                        memory_bm_position_reset(&orig_bm);
                        restore_pblist = NULL;
                        handle->buffer = get_buffer(&orig_bm, &ca);
                        handle->sync_read = 0;
                        if (!handle->buffer)
                              return -ENOMEM;
                  }
            } else {
                  copy_last_highmem_page();
                  handle->buffer = get_buffer(&orig_bm, &ca);
                  if (handle->buffer != buffer)
                        handle->sync_read = 0;
            }
            handle->prev = handle->cur;
      }
      handle->buf_offset = handle->cur_offset;
      if (handle->cur_offset + count >= PAGE_SIZE) {
            count = PAGE_SIZE - handle->cur_offset;
            handle->cur_offset = 0;
            handle->cur++;
      } else {
            handle->cur_offset += count;
      }
      handle->offset += count;
      return count;
}

/**
 *    snapshot_write_finalize - must be called after the last call to
 *    snapshot_write_next() in case the last page in the image happens
 *    to be a highmem page and its contents should be stored in the
 *    highmem.  Additionally, it releases the memory that will not be
 *    used any more.
 */

void snapshot_write_finalize(struct snapshot_handle *handle)
{
      copy_last_highmem_page();
      /* Free only if we have loaded the image entirely */
      if (handle->prev && handle->cur > nr_meta_pages + nr_copy_pages) {
            memory_bm_free(&orig_bm, PG_UNSAFE_CLEAR);
            free_highmem_data();
      }
}

int snapshot_image_loaded(struct snapshot_handle *handle)
{
      return !(!nr_copy_pages || !last_highmem_page_copied() ||
                  handle->cur <= nr_meta_pages + nr_copy_pages);
}

#ifdef CONFIG_HIGHMEM
/* Assumes that @buf is ready and points to a "safe" page */
static inline void
swap_two_pages_data(struct page *p1, struct page *p2, void *buf)
{
      void *kaddr1, *kaddr2;

      kaddr1 = kmap_atomic(p1, KM_USER0);
      kaddr2 = kmap_atomic(p2, KM_USER1);
      memcpy(buf, kaddr1, PAGE_SIZE);
      memcpy(kaddr1, kaddr2, PAGE_SIZE);
      memcpy(kaddr2, buf, PAGE_SIZE);
      kunmap_atomic(kaddr1, KM_USER0);
      kunmap_atomic(kaddr2, KM_USER1);
}

/**
 *    restore_highmem - for each highmem page that was allocated before
 *    the suspend and included in the suspend image, and also has been
 *    allocated by the "resume" kernel swap its current (ie. "before
 *    resume") contents with the previous (ie. "before suspend") one.
 *
 *    If the resume eventually fails, we can call this function once
 *    again and restore the "before resume" highmem state.
 */

int restore_highmem(void)
{
      struct highmem_pbe *pbe = highmem_pblist;
      void *buf;

      if (!pbe)
            return 0;

      buf = get_image_page(GFP_ATOMIC, PG_SAFE);
      if (!buf)
            return -ENOMEM;

      while (pbe) {
            swap_two_pages_data(pbe->copy_page, pbe->orig_page, buf);
            pbe = pbe->next;
      }
      free_image_page(buf, PG_UNSAFE_CLEAR);
      return 0;
}
#endif /* CONFIG_HIGHMEM */

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