PM / Hibernate: Avoid hitting OOM during preallocation of memory

[net-next-2.6.git] / kernel / power / snapshot.c

/*
 * linux/kernel/power/snapshot.c
 *
 * This file provides system snapshot/restore functionality for swsusp.
 *
 * Copyright (C) 1998-2005 Pavel Machek <pavel@ucw.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 <linux/list.h>
#include <linux/slab.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 *);

/*
 * Preferred image size in bytes (tunable via /sys/power/image_size).
 * When it is set to N, swsusp will do its best to ensure the image
 * size will not exceed N bytes, but if that is impossible, it will
 * try to create the smallest image possible.
 */
unsigned long image_size = 500 * 1024 * 1024;

/* 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.
  */

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;
}

/**
 *      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 bitmap 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 bitmap)
 *      It also contains the pfns that correspond to the start and end of
 *      the represented memory area.
 */

#define BM_END_OF_MAP   (~0UL)

#define BM_BITS_PER_BLOCK       (PAGE_SIZE * BITS_PER_BYTE)

struct bm_block {
        struct list_head hook;  /* hook into a list of bitmap blocks */
        unsigned long start_pfn;        /* pfn represented by the first bit */
        unsigned long end_pfn;  /* pfn represented by the last bit plus 1 */
        unsigned long *data;    /* bitmap representing pages */
};

static inline unsigned long bm_block_bits(struct bm_block *bb)
{
        return bb->end_pfn - bb->start_pfn;
}

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

struct bm_position {
        struct bm_block *block;
        int bit;
};

struct memory_bitmap {
        struct list_head blocks;        /* list of bitmap blocks */
        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 void memory_bm_position_reset(struct memory_bitmap *bm)
{
        bm->cur.block = list_entry(bm->blocks.next, struct bm_block, hook);
        bm->cur.bit = 0;
}

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

/**
 *      create_bm_block_list - create a list of block bitmap objects
 *      @pages - number of pages to track
 *      @list - list to put the allocated blocks into
 *      @ca - chain allocator to be used for allocating memory
 */
static int create_bm_block_list(unsigned long pages,
                                struct list_head *list,
                                struct chain_allocator *ca)
{
        unsigned int nr_blocks = DIV_ROUND_UP(pages, BM_BITS_PER_BLOCK);

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

                bb = chain_alloc(ca, sizeof(struct bm_block));
                if (!bb)
                        return -ENOMEM;
                list_add(&bb->hook, list);
        }

        return 0;
}

struct mem_extent {
        struct list_head hook;
        unsigned long start;
        unsigned long end;
};

/**
 *      free_mem_extents - free a list of memory extents
 *      @list - list of extents to empty
 */
static void free_mem_extents(struct list_head *list)
{
        struct mem_extent *ext, *aux;

        list_for_each_entry_safe(ext, aux, list, hook) {
                list_del(&ext->hook);
                kfree(ext);
        }
}

/**
 *      create_mem_extents - create a list of memory extents representing
 *                           contiguous ranges of PFNs
 *      @list - list to put the extents into
 *      @gfp_mask - mask to use for memory allocations
 */
static int create_mem_extents(struct list_head *list, gfp_t gfp_mask)
{
        struct zone *zone;

        INIT_LIST_HEAD(list);

        for_each_populated_zone(zone) {
                unsigned long zone_start, zone_end;
                struct mem_extent *ext, *cur, *aux;

                zone_start = zone->zone_start_pfn;
                zone_end = zone->zone_start_pfn + zone->spanned_pages;

                list_for_each_entry(ext, list, hook)
                        if (zone_start <= ext->end)
                                break;

                if (&ext->hook == list || zone_end < ext->start) {
                        /* New extent is necessary */
                        struct mem_extent *new_ext;

                        new_ext = kzalloc(sizeof(struct mem_extent), gfp_mask);
                        if (!new_ext) {
                                free_mem_extents(list);
                                return -ENOMEM;
                        }
                        new_ext->start = zone_start;
                        new_ext->end = zone_end;
                        list_add_tail(&new_ext->hook, &ext->hook);
                        continue;
                }

                /* Merge this zone's range of PFNs with the existing one */
                if (zone_start < ext->start)
                        ext->start = zone_start;
                if (zone_end > ext->end)
                        ext->end = zone_end;

                /* More merging may be possible */
                cur = ext;
                list_for_each_entry_safe_continue(cur, aux, list, hook) {
                        if (zone_end < cur->start)
                                break;
                        if (zone_end < cur->end)
                                ext->end = cur->end;
                        list_del(&cur->hook);
                        kfree(cur);
                }
        }

        return 0;
}

/**
  *     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 list_head mem_extents;
        struct mem_extent *ext;
        int error;

        chain_init(&ca, gfp_mask, safe_needed);
        INIT_LIST_HEAD(&bm->blocks);

        error = create_mem_extents(&mem_extents, gfp_mask);
        if (error)
                return error;

        list_for_each_entry(ext, &mem_extents, hook) {
                struct bm_block *bb;
                unsigned long pfn = ext->start;
                unsigned long pages = ext->end - ext->start;

                bb = list_entry(bm->blocks.prev, struct bm_block, hook);

                error = create_bm_block_list(pages, bm->blocks.prev, &ca);
                if (error)
                        goto Error;

                list_for_each_entry_continue(bb, &bm->blocks, hook) {
                        bb->data = get_image_page(gfp_mask, safe_needed);
                        if (!bb->data) {
                                error = -ENOMEM;
                                goto Error;
                        }

                        bb->start_pfn = pfn;
                        if (pages >= BM_BITS_PER_BLOCK) {
                                pfn += BM_BITS_PER_BLOCK;
                                pages -= BM_BITS_PER_BLOCK;
                        } else {
                                /* This is executed only once in the loop */
                                pfn += pages;
                        }
                        bb->end_pfn = pfn;
                }
        }

        bm->p_list = ca.chain;
        memory_bm_position_reset(bm);
 Exit:
        free_mem_extents(&mem_extents);
        return error;

 Error:
        bm->p_list = ca.chain;
        memory_bm_free(bm, PG_UNSAFE_CLEAR);
        goto Exit;
}

/**
  *     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 bm_block *bb;

        list_for_each_entry(bb, &bm->blocks, hook)
                if (bb->data)
                        free_image_page(bb->data, clear_nosave_free);

        free_list_of_pages(bm->p_list, clear_nosave_free);

        INIT_LIST_HEAD(&bm->blocks);
}

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

        /*
         * Check if the pfn corresponds to the current bitmap block and find
         * the block where it fits if this is not the case.
         */
        bb = bm->cur.block;
        if (pfn < bb->start_pfn)
                list_for_each_entry_continue_reverse(bb, &bm->blocks, hook)
                        if (pfn >= bb->start_pfn)
                                break;

        if (pfn >= bb->end_pfn)
                list_for_each_entry_continue(bb, &bm->blocks, hook)
                        if (pfn >= bb->start_pfn && pfn < bb->end_pfn)
                                break;

        if (&bb->hook == &bm->blocks)
                return -EFAULT;

        /* The block has been found */
        bm->cur.block = bb;
        pfn -= bb->start_pfn;
        bm->cur.bit = pfn + 1;
        *bit_nr = pfn;
        *addr = bb->data;
        return 0;
}

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

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

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

        error = memory_bm_find_bit(bm, pfn, &addr, &bit);
        if (!error)
                set_bit(bit, addr);
        return error;
}

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

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

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

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

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

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

/**
 *      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 bm_block *bb;
        int bit;

        bb = bm->cur.block;
        do {
                bit = bm->cur.bit;
                bit = find_next_bit(bb->data, bm_block_bits(bb), bit);
                if (bit < bm_block_bits(bb))
                        goto Return_pfn;

                bb = list_entry(bb->hook.next, struct bm_block, hook);
                bm->cur.block = bb;
                bm->cur.bit = 0;
        } while (&bb->hook != &bm->blocks);

        memory_bm_position_reset(bm);
        return BM_END_OF_MAP;

 Return_pfn:
        bm->cur.bit = bit + 1;
        return bb->start_pfn + bit;
}

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

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(sizeof(struct nosave_region));
        region->start_pfn = start_pfn;
        region->end_pfn = end_pfn;
        list_add_tail(&region->list, &nosave_regions);
 Report:
        printk(KERN_INFO "PM: Registered nosave memory: %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;

                pr_debug("PM: 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)) {
                                /*
                                 * It is safe to ignore the result of
                                 * mem_bm_set_bit_check() here, since we won't
                                 * touch the PFNs for which the error is
                                 * returned anyway.
                                 */
                                mem_bm_set_bit_check(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);

        pr_debug("PM: 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);

        pr_debug("PM: 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_populated_zone(zone)
                if (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(struct zone *zone, unsigned long pfn)
{
        struct page *page;

        if (!pfn_valid(pfn))
                return NULL;

        page = pfn_to_page(pfn);
        if (page_zone(page) != zone)
                return NULL;

        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.
 */

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

        for_each_populated_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(zone, pfn))
                                n++;
        }
        return n;
}
#else
static inline void *saveable_highmem_page(struct zone *z, unsigned long p)
{
        return NULL;
}
#endif /* CONFIG_HIGHMEM */

/**
 *      saveable_page - 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(struct zone *zone, unsigned long pfn)
{
        struct page *page;

        if (!pfn_valid(pfn))
                return NULL;

        page = pfn_to_page(pfn);
        if (page_zone(page) != zone)
                return NULL;

        BUG_ON(PageHighMem(page));

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

        if (PageReserved(page)
            && (!kernel_page_present(page) || pfn_is_nosave(pfn)))
                return NULL;

        return page;
}

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

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

        for_each_populated_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(zone, 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++;
}


/**
 *      safe_copy_page - check if the page we are going to copy is marked as
 *              present in the kernel page tables (this always is the case if
 *              CONFIG_DEBUG_PAGEALLOC is not set and in that case
 *              kernel_page_present() always returns 'true').
 */
static void safe_copy_page(void *dst, struct page *s_page)
{
        if (kernel_page_present(s_page)) {
                do_copy_page(dst, page_address(s_page));
        } else {
                kernel_map_pages(s_page, 1, 1);
                do_copy_page(dst, page_address(s_page));
                kernel_map_pages(s_page, 1, 0);
        }
}


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

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

static inline void copy_data_page(unsigned long dst_pfn, unsigned long src_pfn)
{
        safe_copy_page(page_address(pfn_to_page(dst_pfn)),
                                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_populated_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;
/*
 * Numbers of normal and highmem page frames allocated for hibernation image
 * before suspending devices.
 */
unsigned int alloc_normal, alloc_highmem;
/*
 * Memory bitmap used for marking saveable pages (during hibernation) or
 * hibernation image pages (during restore)
 */
static struct memory_bitmap orig_bm;
/*
 * Memory bitmap used during hibernation for marking allocated page frames that
 * will contain copies of saveable pages.  During restore it is initially used
 * for marking hibernation image pages, but then the set bits from it are
 * duplicated in @orig_bm and it is released.  On highmem systems it is next
 * used for marking "safe" highmem pages, but it has to be reinitialized for
 * this purpose.
 */
static struct memory_bitmap copy_bm;

/**
 *      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_populated_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;
        alloc_normal = 0;
        alloc_highmem = 0;
        hibernation_thaw_swap();
}

/* Helper functions used for the shrinking of memory. */

#define GFP_IMAGE       (GFP_KERNEL | __GFP_NOWARN)

/**
 * preallocate_image_pages - Allocate a number of pages for hibernation image
 * @nr_pages: Number of page frames to allocate.
 * @mask: GFP flags to use for the allocation.
 *
 * Return value: Number of page frames actually allocated
 */
static unsigned long preallocate_image_pages(unsigned long nr_pages, gfp_t mask)
{
        unsigned long nr_alloc = 0;

        while (nr_pages > 0) {
                struct page *page;

                page = alloc_image_page(mask);
                if (!page)
                        break;
                memory_bm_set_bit(&copy_bm, page_to_pfn(page));
                if (PageHighMem(page))
                        alloc_highmem++;
                else
                        alloc_normal++;
                nr_pages--;
                nr_alloc++;
        }

        return nr_alloc;
}

static unsigned long preallocate_image_memory(unsigned long nr_pages,
                                              unsigned long avail_normal)
{
        unsigned long alloc;

        if (avail_normal <= alloc_normal)
                return 0;

        alloc = avail_normal - alloc_normal;
        if (nr_pages < alloc)
                alloc = nr_pages;

        return preallocate_image_pages(alloc, GFP_IMAGE);
}

#ifdef CONFIG_HIGHMEM
static unsigned long preallocate_image_highmem(unsigned long nr_pages)
{
        return preallocate_image_pages(nr_pages, GFP_IMAGE | __GFP_HIGHMEM);
}

/**
 *  __fraction - Compute (an approximation of) x * (multiplier / base)
 */
static unsigned long __fraction(u64 x, u64 multiplier, u64 base)
{
        x *= multiplier;
        do_div(x, base);
        return (unsigned long)x;
}

static unsigned long preallocate_highmem_fraction(unsigned long nr_pages,
                                                unsigned long highmem,
                                                unsigned long total)
{
        unsigned long alloc = __fraction(nr_pages, highmem, total);

        return preallocate_image_pages(alloc, GFP_IMAGE | __GFP_HIGHMEM);
}
#else /* CONFIG_HIGHMEM */
static inline unsigned long preallocate_image_highmem(unsigned long nr_pages)
{
        return 0;
}

static inline unsigned long preallocate_highmem_fraction(unsigned long nr_pages,
                                                unsigned long highmem,
                                                unsigned long total)
{
        return 0;
}
#endif /* CONFIG_HIGHMEM */

/**
 * free_unnecessary_pages - Release preallocated pages not needed for the image
 */
static void free_unnecessary_pages(void)
{
        unsigned long save, to_free_normal, to_free_highmem;

        save = count_data_pages();
        if (alloc_normal >= save) {
                to_free_normal = alloc_normal - save;
                save = 0;
        } else {
                to_free_normal = 0;
                save -= alloc_normal;
        }
        save += count_highmem_pages();
        if (alloc_highmem >= save) {
                to_free_highmem = alloc_highmem - save;
        } else {
                to_free_highmem = 0;
                to_free_normal -= save - alloc_highmem;
        }

        memory_bm_position_reset(&copy_bm);

        while (to_free_normal > 0 || to_free_highmem > 0) {
                unsigned long pfn = memory_bm_next_pfn(&copy_bm);
                struct page *page = pfn_to_page(pfn);

                if (PageHighMem(page)) {
                        if (!to_free_highmem)
                                continue;
                        to_free_highmem--;
                        alloc_highmem--;
                } else {
                        if (!to_free_normal)
                                continue;
                        to_free_normal--;
                        alloc_normal--;
                }
                memory_bm_clear_bit(&copy_bm, pfn);
                swsusp_unset_page_forbidden(page);
                swsusp_unset_page_free(page);
                __free_page(page);
        }
}

/**
 * minimum_image_size - Estimate the minimum acceptable size of an image
 * @saveable: Number of saveable pages in the system.
 *
 * We want to avoid attempting to free too much memory too hard, so estimate the
 * minimum acceptable size of a hibernation image to use as the lower limit for
 * preallocating memory.
 *
 * We assume that the minimum image size should be proportional to
 *
 * [number of saveable pages] - [number of pages that can be freed in theory]
 *
 * where the second term is the sum of (1) reclaimable slab pages, (2) active
 * and (3) inactive anonymouns pages, (4) active and (5) inactive file pages,
 * minus mapped file pages.
 */
static unsigned long minimum_image_size(unsigned long saveable)
{
        unsigned long size;

        size = global_page_state(NR_SLAB_RECLAIMABLE)
                + global_page_state(NR_ACTIVE_ANON)
                + global_page_state(NR_INACTIVE_ANON)
                + global_page_state(NR_ACTIVE_FILE)
                + global_page_state(NR_INACTIVE_FILE)
                - global_page_state(NR_FILE_MAPPED);

        return saveable <= size ? 0 : saveable - size;
}

/**
 * hibernate_preallocate_memory - Preallocate memory for hibernation image
 *
 * To create a hibernation image it is necessary to make a copy of every page
 * frame in use.  We also need a number of page frames to be free during
 * hibernation for allocations made while saving the image and for device
 * drivers, in case they need to allocate memory from their hibernation
 * callbacks (these two numbers are given by PAGES_FOR_IO and SPARE_PAGES,
 * respectively, both of which are rough estimates).  To make this happen, we
 * compute the total number of available page frames and allocate at least
 *
 * ([page frames total] + PAGES_FOR_IO + [metadata pages]) / 2 + 2 * SPARE_PAGES
 *
 * of them, which corresponds to the maximum size of a hibernation image.
 *
 * If image_size is set below the number following from the above formula,
 * the preallocation of memory is continued until the total number of saveable
 * pages in the system is below the requested image size or the minimum
 * acceptable image size returned by minimum_image_size(), whichever is greater.
 */
int hibernate_preallocate_memory(void)
{
        struct zone *zone;
        unsigned long saveable, size, max_size, count, highmem, pages = 0;
        unsigned long alloc, save_highmem, pages_highmem, avail_normal;
        struct timeval start, stop;
        int error;

        printk(KERN_INFO "PM: Preallocating image memory... ");
        do_gettimeofday(&start);

        error = memory_bm_create(&orig_bm, GFP_IMAGE, PG_ANY);
        if (error)
                goto err_out;

        error = memory_bm_create(&copy_bm, GFP_IMAGE, PG_ANY);
        if (error)
                goto err_out;

        alloc_normal = 0;
        alloc_highmem = 0;

        /* Count the number of saveable data pages. */
        save_highmem = count_highmem_pages();
        saveable = count_data_pages();

        /*
         * Compute the total number of page frames we can use (count) and the
         * number of pages needed for image metadata (size).
         */
        count = saveable;
        saveable += save_highmem;
        highmem = save_highmem;
        size = 0;
        for_each_populated_zone(zone) {
                size += snapshot_additional_pages(zone);
                if (is_highmem(zone))
                        highmem += zone_page_state(zone, NR_FREE_PAGES);
                else
                        count += zone_page_state(zone, NR_FREE_PAGES);
        }
        avail_normal = count;
        count += highmem;
        count -= totalreserve_pages;

        /* Compute the maximum number of saveable pages to leave in memory. */
        max_size = (count - (size + PAGES_FOR_IO)) / 2 - 2 * SPARE_PAGES;
        size = DIV_ROUND_UP(image_size, PAGE_SIZE);
        if (size > max_size)
                size = max_size;
        /*
         * If the maximum is not less than the current number of saveable pages
         * in memory, allocate page frames for the image and we're done.
         */
        if (size >= saveable) {
                pages = preallocate_image_highmem(save_highmem);
                pages += preallocate_image_memory(saveable - pages, avail_normal);
                goto out;
        }

        /* Estimate the minimum size of the image. */
        pages = minimum_image_size(saveable);
        /*
         * To avoid excessive pressure on the normal zone, leave room in it to
         * accommodate an image of the minimum size (unless it's already too
         * small, in which case don't preallocate pages from it at all).
         */
        if (avail_normal > pages)
                avail_normal -= pages;
        else
                avail_normal = 0;
        if (size < pages)
                size = min_t(unsigned long, pages, max_size);

        /*
         * Let the memory management subsystem know that we're going to need a
         * large number of page frames to allocate and make it free some memory.
         * NOTE: If this is not done, performance will be hurt badly in some
         * test cases.
         */
        shrink_all_memory(saveable - size);

        /*
         * The number of saveable pages in memory was too high, so apply some
         * pressure to decrease it.  First, make room for the largest possible
         * image and fail if that doesn't work.  Next, try to decrease the size
         * of the image as much as indicated by 'size' using allocations from
         * highmem and non-highmem zones separately.
         */
        pages_highmem = preallocate_image_highmem(highmem / 2);
        alloc = (count - max_size) - pages_highmem;
        pages = preallocate_image_memory(alloc, avail_normal);
        if (pages < alloc) {
                /* We have exhausted non-highmem pages, try highmem. */
                alloc -= pages;
                pages += pages_highmem;
                pages_highmem = preallocate_image_highmem(alloc);
                if (pages_highmem < alloc)
                        goto err_out;
                pages += pages_highmem;
                /*
                 * size is the desired number of saveable pages to leave in
                 * memory, so try to preallocate (all memory - size) pages.
                 */
                alloc = (count - pages) - size;
                pages += preallocate_image_highmem(alloc);
        } else {
                /*
                 * There are approximately max_size saveable pages at this point
                 * and we want to reduce this number down to size.
                 */
                alloc = max_size - size;
                size = preallocate_highmem_fraction(alloc, highmem, count);
                pages_highmem += size;
                alloc -= size;
                size = preallocate_image_memory(alloc, avail_normal);
                pages_highmem += preallocate_image_highmem(alloc - size);
                pages += pages_highmem + size;
        }

        /*
         * We only need as many page frames for the image as there are saveable
         * pages in memory, but we have allocated more.  Release the excessive
         * ones now.
         */
        free_unnecessary_pages();

 out:
        do_gettimeofday(&stop);
        printk(KERN_CONT "done (allocated %lu pages)\n", pages);
        swsusp_show_speed(&start, &stop, pages, "Allocated");

        return 0;

 err_out:
        printk(KERN_CONT "\n");
        swsusp_free();
        return -ENOMEM;
}

#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() + alloc_highmem;

        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 = alloc_normal;

        for_each_populated_zone(zone)
                if (!is_highmem(zone))
                        free += zone_page_state(zone, NR_FREE_PAGES);

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

        return free > nr_pages + PAGES_FOR_IO;
}

#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_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_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 = 0;

        if (nr_highmem > 0) {
                error = get_highmem_buffer(PG_ANY);
                if (error)
                        goto err_out;
                if (nr_highmem > alloc_highmem) {
                        nr_highmem -= alloc_highmem;
                        nr_pages += alloc_highmem_pages(copy_bm, nr_highmem);
                }
        }
        if (nr_pages > alloc_normal) {
                nr_pages -= alloc_normal;
                while (nr_pages-- > 0) {
                        struct page *page;

                        page = alloc_image_page(GFP_ATOMIC | __GFP_COLD);
                        if (!page)
                                goto err_out;
                        memory_bm_set_bit(copy_bm, page_to_pfn(page));
                }
        }

        return 0;

 err_out:
        swsusp_free();
        return error;
}

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

        printk(KERN_INFO "PM: Creating hibernation image:\n");

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

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

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

        /* During allocating of suspend pagedir, new cold pages may appear.
         * Kill them.
         */
        drain_local_pages(NULL);
        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(KERN_INFO "PM: Hibernation image created (%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 */

unsigned long snapshot_get_image_size(void)
{
        return nr_copy_pages + nr_meta_pages + 1;
}

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 = snapshot_get_image_size();
        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.
 *
 *      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 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)
{
        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->cur) {
                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);
        } else 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->cur++;
        return PAGE_SIZE;
}

/**
 *      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_populated_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 "PM: Image 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 int 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;

                if (memory_bm_pfn_present(bm, buf[j]))
                        memory_bm_set_bit(bm, buf[j]);
                else
                        return -EFAULT;
        }

        return 0;
}

/* 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 ERR_PTR(-ENOMEM);
        }
        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 ERR_PTR(-EINVAL);
}

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;
        unsigned long pfn = memory_bm_next_pfn(bm);

        if (pfn == BM_END_OF_MAP)
                return ERR_PTR(-EFAULT);

        page = pfn_to_page(pfn);
        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 ERR_PTR(-ENOMEM);
        }
        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.
 *
 *      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 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)
{
        static struct chain_allocator ca;
        int error = 0;

        /* Check if we have already loaded the entire image */
        if (handle->cur > 1 && handle->cur > nr_meta_pages + nr_copy_pages)
                return 0;

        handle->sync_read = 1;

        if (!handle->cur) {
                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;
        } else if (handle->cur == 1) {
                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->cur <= nr_meta_pages + 1) {
                error = unpack_orig_pfns(buffer, &copy_bm);
                if (error)
                        return error;

                if (handle->cur == nr_meta_pages + 1) {
                        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 (IS_ERR(handle->buffer))
                                return PTR_ERR(handle->buffer);
                }
        } else {
                copy_last_highmem_page();
                handle->buffer = get_buffer(&orig_bm, &ca);
                if (IS_ERR(handle->buffer))
                        return PTR_ERR(handle->buffer);
                if (handle->buffer != buffer)
                        handle->sync_read = 0;
        }
        handle->cur++;
        return PAGE_SIZE;
}

/**
 *      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->cur > 1 && 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 */