[releases.git] / snapshot.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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>
 */

#define pr_fmt(fmt) "PM: hibernation: " fmt

#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/memblock.h>
#include <linux/nmi.h>
#include <linux/syscalls.h>
#include <linux/console.h>
#include <linux/highmem.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/compiler.h>
#include <linux/ktime.h>
#include <linux/set_memory.h>

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

#include "power.h"

#if defined(CONFIG_STRICT_KERNEL_RWX) && defined(CONFIG_ARCH_HAS_SET_MEMORY)
static bool hibernate_restore_protection;
static bool hibernate_restore_protection_active;

void enable_restore_image_protection(void)
{
        hibernate_restore_protection = true;
}

static inline void hibernate_restore_protection_begin(void)
{
        hibernate_restore_protection_active = hibernate_restore_protection;
}

static inline void hibernate_restore_protection_end(void)
{
        hibernate_restore_protection_active = false;
}

static inline void hibernate_restore_protect_page(void *page_address)
{
        if (hibernate_restore_protection_active)
                set_memory_ro((unsigned long)page_address, 1);
}

static inline void hibernate_restore_unprotect_page(void *page_address)
{
        if (hibernate_restore_protection_active)
                set_memory_rw((unsigned long)page_address, 1);
}
#else
static inline void hibernate_restore_protection_begin(void) {}
static inline void hibernate_restore_protection_end(void) {}
static inline void hibernate_restore_protect_page(void *page_address) {}
static inline void hibernate_restore_unprotect_page(void *page_address) {}
#endif /* CONFIG_STRICT_KERNEL_RWX  && CONFIG_ARCH_HAS_SET_MEMORY */

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

/*
 * Number of bytes to reserve for memory allocations made by device drivers
 * from their ->freeze() and ->freeze_noirq() callbacks so that they don't
 * cause image creation to fail (tunable via /sys/power/reserved_size).
 */
unsigned long reserved_size;

void __init hibernate_reserved_size_init(void)
{
        reserved_size = SPARE_PAGES * PAGE_SIZE;
}

/*
 * 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;

void __init hibernate_image_size_init(void)
{
        image_size = ((totalram_pages() * 2) / 5) * PAGE_SIZE;
}

/*
 * 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;

/* 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];
} __packed;

/*
 * List of "safe" pages (ie. pages that were not used by the image kernel
 * before hibernation) that may be used as temporary storage for image kernel
 * memory contents.
 */
static struct linked_page *safe_pages_list;

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

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

static unsigned int allocated_unsafe_pages;

/**
 * get_image_page - Allocate a page for a hibernation image.
 * @gfp_mask: GFP mask for the allocation.
 * @safe_needed: Get pages that were not used before hibernation (restore only)
 *
 * During image restoration, for storing the PBE list and the image data, we can
 * only use memory pages that do not conflict with the pages used before
 * hibernation.  The "unsafe" pages have PageNosaveFree set and we count them
 * using allocated_unsafe_pages.
 *
 * Each allocated image page is marked as PageNosave and PageNosaveFree so that
 * swsusp_free() can release it.
 */
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;
}

static void *__get_safe_page(gfp_t gfp_mask)
{
        if (safe_pages_list) {
                void *ret = safe_pages_list;

                safe_pages_list = safe_pages_list->next;
                memset(ret, 0, PAGE_SIZE);
                return ret;
        }
        return get_image_page(gfp_mask, PG_SAFE);
}

unsigned long get_safe_page(gfp_t gfp_mask)
{
        return (unsigned long)__get_safe_page(gfp_mask);
}

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;
}

static void recycle_safe_page(void *page_address)
{
        struct linked_page *lp = page_address;

        lp->next = safe_pages_list;
        safe_pages_list = lp;
}

/**
 * free_image_page - Free a page allocated for hibernation image.
 * @addr: Address of the page to free.
 * @clear_nosave_free: If set, clear the PageNosaveFree bit for the page.
 *
 * The page to free should have been allocated by get_image_page() (page flags
 * set by it are affected).
 */
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);
}

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 = ca->safe_needed ? __get_safe_page(ca->gfp_mask) :
                                        get_image_page(ca->gfp_mask, PG_ANY);
                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.
 *
 * The memory bitmap is organized as a radix tree to guarantee fast random
 * access to the bits. There is one radix tree for each zone (as returned
 * from create_mem_extents).
 *
 * One radix tree is represented by one struct mem_zone_bm_rtree. There are
 * two linked lists for the nodes of the tree, one for the inner nodes and
 * one for the leave nodes. The linked leave nodes are used for fast linear
 * access of the memory bitmap.
 *
 * The struct rtree_node represents one node of the radix tree.
 */

#define BM_END_OF_MAP   (~0UL)

#define BM_BITS_PER_BLOCK       (PAGE_SIZE * BITS_PER_BYTE)
#define BM_BLOCK_SHIFT          (PAGE_SHIFT + 3)
#define BM_BLOCK_MASK           ((1UL << BM_BLOCK_SHIFT) - 1)

/*
 * struct rtree_node is a wrapper struct to link the nodes
 * of the rtree together for easy linear iteration over
 * bits and easy freeing
 */
struct rtree_node {
        struct list_head list;
        unsigned long *data;
};

/*
 * struct mem_zone_bm_rtree represents a bitmap used for one
 * populated memory zone.
 */
struct mem_zone_bm_rtree {
        struct list_head list;          /* Link Zones together         */
        struct list_head nodes;         /* Radix Tree inner nodes      */
        struct list_head leaves;        /* Radix Tree leaves           */
        unsigned long start_pfn;        /* Zone start page frame       */
        unsigned long end_pfn;          /* Zone end page frame + 1     */
        struct rtree_node *rtree;       /* Radix Tree Root             */
        int levels;                     /* Number of Radix Tree Levels */
        unsigned int blocks;            /* Number of Bitmap Blocks     */
};

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

struct bm_position {
        struct mem_zone_bm_rtree *zone;
        struct rtree_node *node;
        unsigned long node_pfn;
        int node_bit;
};

struct memory_bitmap {
        struct list_head zones;
        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 */

#define BM_ENTRIES_PER_LEVEL    (PAGE_SIZE / sizeof(unsigned long))
#if BITS_PER_LONG == 32
#define BM_RTREE_LEVEL_SHIFT    (PAGE_SHIFT - 2)
#else
#define BM_RTREE_LEVEL_SHIFT    (PAGE_SHIFT - 3)
#endif
#define BM_RTREE_LEVEL_MASK     ((1UL << BM_RTREE_LEVEL_SHIFT) - 1)

/**
 * alloc_rtree_node - Allocate a new node and add it to the radix tree.
 *
 * This function is used to allocate inner nodes as well as the
 * leave nodes of the radix tree. It also adds the node to the
 * corresponding linked list passed in by the *list parameter.
 */
static struct rtree_node *alloc_rtree_node(gfp_t gfp_mask, int safe_needed,
                                           struct chain_allocator *ca,
                                           struct list_head *list)
{
        struct rtree_node *node;

        node = chain_alloc(ca, sizeof(struct rtree_node));
        if (!node)
                return NULL;

        node->data = get_image_page(gfp_mask, safe_needed);
        if (!node->data)
                return NULL;

        list_add_tail(&node->list, list);

        return node;
}

/**
 * add_rtree_block - Add a new leave node to the radix tree.
 *
 * The leave nodes need to be allocated in order to keep the leaves
 * linked list in order. This is guaranteed by the zone->blocks
 * counter.
 */
static int add_rtree_block(struct mem_zone_bm_rtree *zone, gfp_t gfp_mask,
                           int safe_needed, struct chain_allocator *ca)
{
        struct rtree_node *node, *block, **dst;
        unsigned int levels_needed, block_nr;
        int i;

        block_nr = zone->blocks;
        levels_needed = 0;

        /* How many levels do we need for this block nr? */
        while (block_nr) {
                levels_needed += 1;
                block_nr >>= BM_RTREE_LEVEL_SHIFT;
        }

        /* Make sure the rtree has enough levels */
        for (i = zone->levels; i < levels_needed; i++) {
                node = alloc_rtree_node(gfp_mask, safe_needed, ca,
                                        &zone->nodes);
                if (!node)
                        return -ENOMEM;

                node->data[0] = (unsigned long)zone->rtree;
                zone->rtree = node;
                zone->levels += 1;
        }

        /* Allocate new block */
        block = alloc_rtree_node(gfp_mask, safe_needed, ca, &zone->leaves);
        if (!block)
                return -ENOMEM;

        /* Now walk the rtree to insert the block */
        node = zone->rtree;
        dst = &zone->rtree;
        block_nr = zone->blocks;
        for (i = zone->levels; i > 0; i--) {
                int index;

                if (!node) {
                        node = alloc_rtree_node(gfp_mask, safe_needed, ca,
                                                &zone->nodes);
                        if (!node)
                                return -ENOMEM;
                        *dst = node;
                }

                index = block_nr >> ((i - 1) * BM_RTREE_LEVEL_SHIFT);
                index &= BM_RTREE_LEVEL_MASK;
                dst = (struct rtree_node **)&((*dst)->data[index]);
                node = *dst;
        }

        zone->blocks += 1;
        *dst = block;

        return 0;
}

static void free_zone_bm_rtree(struct mem_zone_bm_rtree *zone,
                               int clear_nosave_free);

/**
 * create_zone_bm_rtree - Create a radix tree for one zone.
 *
 * Allocated the mem_zone_bm_rtree structure and initializes it.
 * This function also allocated and builds the radix tree for the
 * zone.
 */
static struct mem_zone_bm_rtree *create_zone_bm_rtree(gfp_t gfp_mask,
                                                      int safe_needed,
                                                      struct chain_allocator *ca,
                                                      unsigned long start,
                                                      unsigned long end)
{
        struct mem_zone_bm_rtree *zone;
        unsigned int i, nr_blocks;
        unsigned long pages;

        pages = end - start;
        zone  = chain_alloc(ca, sizeof(struct mem_zone_bm_rtree));
        if (!zone)
                return NULL;

        INIT_LIST_HEAD(&zone->nodes);
        INIT_LIST_HEAD(&zone->leaves);
        zone->start_pfn = start;
        zone->end_pfn = end;
        nr_blocks = DIV_ROUND_UP(pages, BM_BITS_PER_BLOCK);

        for (i = 0; i < nr_blocks; i++) {
                if (add_rtree_block(zone, gfp_mask, safe_needed, ca)) {
                        free_zone_bm_rtree(zone, PG_UNSAFE_CLEAR);
                        return NULL;
                }
        }

        return zone;
}

/**
 * free_zone_bm_rtree - Free the memory of the radix tree.
 *
 * Free all node pages of the radix tree. The mem_zone_bm_rtree
 * structure itself is not freed here nor are the rtree_node
 * structs.
 */
static void free_zone_bm_rtree(struct mem_zone_bm_rtree *zone,
                               int clear_nosave_free)
{
        struct rtree_node *node;

        list_for_each_entry(node, &zone->nodes, list)
                free_image_page(node->data, clear_nosave_free);

        list_for_each_entry(node, &zone->leaves, list)
                free_image_page(node->data, clear_nosave_free);
}

static void memory_bm_position_reset(struct memory_bitmap *bm)
{
        bm->cur.zone = list_entry(bm->zones.next, struct mem_zone_bm_rtree,
                                  list);
        bm->cur.node = list_entry(bm->cur.zone->leaves.next,
                                  struct rtree_node, list);
        bm->cur.node_pfn = 0;
        bm->cur.node_bit = 0;
}

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

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 free.
 */
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.
 * @list: List to put the extents into.
 * @gfp_mask: Mask to use for memory allocations.
 *
 * The extents represent contiguous ranges of PFNs.
 */
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_end_pfn(zone);

                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->zones);

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

        list_for_each_entry(ext, &mem_extents, hook) {
                struct mem_zone_bm_rtree *zone;

                zone = create_zone_bm_rtree(gfp_mask, safe_needed, &ca,
                                            ext->start, ext->end);
                if (!zone) {
                        error = -ENOMEM;
                        goto Error;
                }
                list_add_tail(&zone->list, &bm->zones);
        }

        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: Memory bitmap.
 */
static void memory_bm_free(struct memory_bitmap *bm, int clear_nosave_free)
{
        struct mem_zone_bm_rtree *zone;

        list_for_each_entry(zone, &bm->zones, list)
                free_zone_bm_rtree(zone, clear_nosave_free);

        free_list_of_pages(bm->p_list, clear_nosave_free);

        INIT_LIST_HEAD(&bm->zones);
}

/**
 * memory_bm_find_bit - Find the bit for a given PFN in a memory bitmap.
 *
 * Find the bit in memory bitmap @bm that corresponds to the given PFN.
 * The cur.zone, cur.block and cur.node_pfn members of @bm are updated.
 *
 * Walk the radix tree to find the page containing the bit that represents @pfn
 * and return the position of the bit in @addr and @bit_nr.
 */
static int memory_bm_find_bit(struct memory_bitmap *bm, unsigned long pfn,
                              void **addr, unsigned int *bit_nr)
{
        struct mem_zone_bm_rtree *curr, *zone;
        struct rtree_node *node;
        int i, block_nr;

        zone = bm->cur.zone;

        if (pfn >= zone->start_pfn && pfn < zone->end_pfn)
                goto zone_found;

        zone = NULL;

        /* Find the right zone */
        list_for_each_entry(curr, &bm->zones, list) {
                if (pfn >= curr->start_pfn && pfn < curr->end_pfn) {
                        zone = curr;
                        break;
                }
        }

        if (!zone)
                return -EFAULT;

zone_found:
        /*
         * We have found the zone. Now walk the radix tree to find the leaf node
         * for our PFN.
         */

        /*
         * If the zone we wish to scan is the current zone and the
         * pfn falls into the current node then we do not need to walk
         * the tree.
         */
        node = bm->cur.node;
        if (zone == bm->cur.zone &&
            ((pfn - zone->start_pfn) & ~BM_BLOCK_MASK) == bm->cur.node_pfn)
                goto node_found;

        node      = zone->rtree;
        block_nr  = (pfn - zone->start_pfn) >> BM_BLOCK_SHIFT;

        for (i = zone->levels; i > 0; i--) {
                int index;

                index = block_nr >> ((i - 1) * BM_RTREE_LEVEL_SHIFT);
                index &= BM_RTREE_LEVEL_MASK;
                BUG_ON(node->data[index] == 0);
                node = (struct rtree_node *)node->data[index];
        }

node_found:
        /* Update last position */
        bm->cur.zone = zone;
        bm->cur.node = node;
        bm->cur.node_pfn = (pfn - zone->start_pfn) & ~BM_BLOCK_MASK;

        /* Set return values */
        *addr = node->data;
        *bit_nr = (pfn - zone->start_pfn) & BM_BLOCK_MASK;

        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 void memory_bm_clear_current(struct memory_bitmap *bm)
{
        int bit;

        bit = max(bm->cur.node_bit - 1, 0);
        clear_bit(bit, bm->cur.node->data);
}

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);
}

/*
 * rtree_next_node - Jump to the next leaf node.
 *
 * Set the position to the beginning of the next node in the
 * memory bitmap. This is either the next node in the current
 * zone's radix tree or the first node in the radix tree of the
 * next zone.
 *
 * Return true if there is a next node, false otherwise.
 */
static bool rtree_next_node(struct memory_bitmap *bm)
{
        if (!list_is_last(&bm->cur.node->list, &bm->cur.zone->leaves)) {
                bm->cur.node = list_entry(bm->cur.node->list.next,
                                          struct rtree_node, list);
                bm->cur.node_pfn += BM_BITS_PER_BLOCK;
                bm->cur.node_bit  = 0;
                touch_softlockup_watchdog();
                return true;
        }

        /* No more nodes, goto next zone */
        if (!list_is_last(&bm->cur.zone->list, &bm->zones)) {
                bm->cur.zone = list_entry(bm->cur.zone->list.next,
                                  struct mem_zone_bm_rtree, list);
                bm->cur.node = list_entry(bm->cur.zone->leaves.next,
                                          struct rtree_node, list);
                bm->cur.node_pfn = 0;
                bm->cur.node_bit = 0;
                return true;
        }

        /* No more zones */
        return false;
}

/**
 * memory_bm_rtree_next_pfn - Find the next set bit in a memory bitmap.
 * @bm: Memory bitmap.
 *
 * Starting from the last returned position this function searches for the next
 * set bit in @bm and returns the PFN represented by it.  If no more bits are
 * set, BM_END_OF_MAP is returned.
 *
 * It is required to run memory_bm_position_reset() before the first call to
 * this function for the given memory bitmap.
 */
static unsigned long memory_bm_next_pfn(struct memory_bitmap *bm)
{
        unsigned long bits, pfn, pages;
        int bit;

        do {
                pages     = bm->cur.zone->end_pfn - bm->cur.zone->start_pfn;
                bits      = min(pages - bm->cur.node_pfn, BM_BITS_PER_BLOCK);
                bit       = find_next_bit(bm->cur.node->data, bits,
                                          bm->cur.node_bit);
                if (bit < bits) {
                        pfn = bm->cur.zone->start_pfn + bm->cur.node_pfn + bit;
                        bm->cur.node_bit = bit + 1;
                        return pfn;
                }
        } while (rtree_next_node(bm));

        return BM_END_OF_MAP;
}

/*
 * This structure represents a range of page frames the contents of which
 * should not be saved during hibernation.
 */
struct nosave_region {
        struct list_head list;
        unsigned long start_pfn;
        unsigned long end_pfn;
};

static LIST_HEAD(nosave_regions);

static void recycle_zone_bm_rtree(struct mem_zone_bm_rtree *zone)
{
        struct rtree_node *node;

        list_for_each_entry(node, &zone->nodes, list)
                recycle_safe_page(node->data);

        list_for_each_entry(node, &zone->leaves, list)
                recycle_safe_page(node->data);
}

static void memory_bm_recycle(struct memory_bitmap *bm)
{
        struct mem_zone_bm_rtree *zone;
        struct linked_page *p_list;

        list_for_each_entry(zone, &bm->zones, list)
                recycle_zone_bm_rtree(zone);

        p_list = bm->p_list;
        while (p_list) {
                struct linked_page *lp = p_list;

                p_list = lp->next;
                recycle_safe_page(lp);
        }
}

/**
 * register_nosave_region - Register a region of unsaveable memory.
 *
 * Register a range of page frames the contents of which should not be saved
 * during hibernation (to be used in the early initialization code).
 */
void __init register_nosave_region(unsigned long start_pfn, unsigned long end_pfn)
{
        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;
                }
        }
        /* This allocation cannot fail */
        region = memblock_alloc(sizeof(struct nosave_region),
                                SMP_CACHE_BYTES);
        if (!region)
                panic("%s: Failed to allocate %zu bytes\n", __func__,
                      sizeof(struct nosave_region));
        region->start_pfn = start_pfn;
        region->end_pfn = end_pfn;
        list_add_tail(&region->list, &nosave_regions);
 Report:
        pr_info("Registered nosave memory: [mem %#010llx-%#010llx]\n",
                (unsigned long long) start_pfn << PAGE_SHIFT,
                ((unsigned long long) end_pfn << PAGE_SHIFT) - 1);
}

/*
 * 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 - Mark pages that should not be saved.
 * @bm: Memory bitmap.
 *
 * Set the bits in @bm that correspond to the page frames the contents of which
 * should not be saved.
 */
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("Marking nosave pages: [mem %#010llx-%#010llx]\n",
                         (unsigned long long) region->start_pfn << PAGE_SHIFT,
                         ((unsigned long long) region->end_pfn << PAGE_SHIFT)
                                - 1);

                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 to hold basic page information.
 *
 * Create bitmaps needed for marking page frames that should not be saved and
 * free page frames.  The forbidden_pages_map and free_pages_map pointers are
 * only modified if everything goes well, because we don't want the bits to be
 * touched before both bitmaps are set up.
 */
int create_basic_memory_bitmaps(void)
{
        struct memory_bitmap *bm1, *bm2;
        int error = 0;

        if (forbidden_pages_map && free_pages_map)
                return 0;
        else
                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("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 holding basic information.
 *
 * 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;

        if (WARN_ON(!(forbidden_pages_map && free_pages_map)))
                return;

        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("Basic memory bitmaps freed\n");
}

void clear_free_pages(void)
{
        struct memory_bitmap *bm = free_pages_map;
        unsigned long pfn;

        if (WARN_ON(!(free_pages_map)))
                return;

        if (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) || want_init_on_free()) {
                memory_bm_position_reset(bm);
                pfn = memory_bm_next_pfn(bm);
                while (pfn != BM_END_OF_MAP) {
                        if (pfn_valid(pfn))
                                clear_highpage(pfn_to_page(pfn));

                        pfn = memory_bm_next_pfn(bm);
                }
                memory_bm_position_reset(bm);
                pr_info("free pages cleared after restore\n");
        }
}

/**
 * snapshot_additional_pages - Estimate the number of extra pages needed.
 * @zone: Memory zone to carry out the computation for.
 *
 * Estimate the number of additional pages needed for setting up a hibernation
 * image data structures for @zone (usually, the returned value is greater than
 * the exact number).
 */
unsigned int snapshot_additional_pages(struct zone *zone)
{
        unsigned int rtree, nodes;

        rtree = nodes = DIV_ROUND_UP(zone->spanned_pages, BM_BITS_PER_BLOCK);
        rtree += DIV_ROUND_UP(rtree * sizeof(struct rtree_node),
                              LINKED_PAGE_DATA_SIZE);
        while (nodes > 1) {
                nodes = DIV_ROUND_UP(nodes, BM_ENTRIES_PER_LEVEL);
                rtree += nodes;
        }

        return 2 * rtree;
}

#ifdef CONFIG_HIGHMEM
/**
 * count_free_highmem_pages - Compute the total number of free highmem pages.
 *
 * The returned number is 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 - Check if a highmem page is saveable.
 *
 * Determine whether a highmem page should be included in a hibernation image.
 *
 * We should save the page if it isn't Nosave or NosaveFree, or Reserved,
 * and it isn't 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_online_page(pfn);
        if (!page || 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) || PageOffline(page))
                return NULL;

        if (page_is_guard(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_end_pfn(zone);
                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 - Check if the given page is saveable.
 *
 * Determine whether a non-highmem page should be included in a hibernation
 * 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 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_online_page(pfn);
        if (!page || page_zone(page) != zone)
                return NULL;

        BUG_ON(PageHighMem(page));

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

        if (PageOffline(page))
                return NULL;

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

        if (page_is_guard(page))
                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_end_pfn(zone);
                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 - Copy a page in a safe way.
 *
 * 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 or
 * CONFIG_ARCH_HAS_SET_DIRECT_MAP is not set. 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);
                dst = kmap_atomic(d_page);
                do_copy_page(dst, src);
                kunmap_atomic(dst);
                kunmap_atomic(src);
        } else {
                if (PageHighMem(d_page)) {
                        /*
                         * The 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);
                        copy_page(dst, buffer);
                        kunmap_atomic(dst);
                } 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_end_pfn(zone);
                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.
 */
static 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 hibernation image.
 *
 * Image pages are alocated before snapshot creation, so they need to be
 * released after resume.
 */
void swsusp_free(void)
{
        unsigned long fb_pfn, fr_pfn;

        if (!forbidden_pages_map || !free_pages_map)
                goto out;

        memory_bm_position_reset(forbidden_pages_map);
        memory_bm_position_reset(free_pages_map);

loop:
        fr_pfn = memory_bm_next_pfn(free_pages_map);
        fb_pfn = memory_bm_next_pfn(forbidden_pages_map);

        /*
         * Find the next bit set in both bitmaps. This is guaranteed to
         * terminate when fb_pfn == fr_pfn == BM_END_OF_MAP.
         */
        do {
                if (fb_pfn < fr_pfn)
                        fb_pfn = memory_bm_next_pfn(forbidden_pages_map);
                if (fr_pfn < fb_pfn)
                        fr_pfn = memory_bm_next_pfn(free_pages_map);
        } while (fb_pfn != fr_pfn);

        if (fr_pfn != BM_END_OF_MAP && pfn_valid(fr_pfn)) {
                struct page *page = pfn_to_page(fr_pfn);

                memory_bm_clear_current(forbidden_pages_map);
                memory_bm_clear_current(free_pages_map);
                hibernate_restore_unprotect_page(page_address(page));
                __free_page(page);
                goto loop;
        }

out:
        nr_copy_pages = 0;
        nr_meta_pages = 0;
        restore_pblist = NULL;
        buffer = NULL;
        alloc_normal = 0;
        alloc_highmem = 0;
        hibernate_restore_protection_end();
}

/* 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)
{
        return div64_u64(x * multiplier, base);
}

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 unsigned long free_unnecessary_pages(void)
{
        unsigned long save, to_free_normal, to_free_highmem, free;

        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;
                save -= alloc_highmem;
                if (to_free_normal > save)
                        to_free_normal -= save;
                else
                        to_free_normal = 0;
        }
        free = to_free_normal + to_free_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);
        }

        return free;
}

/**
 * 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 anonymous pages, (4) active and (5) inactive file pages.
 */
static unsigned long minimum_image_size(unsigned long saveable)
{
        unsigned long size;

        size = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B)
                + global_node_page_state(NR_ACTIVE_ANON)
                + global_node_page_state(NR_INACTIVE_ANON)
                + global_node_page_state(NR_ACTIVE_FILE)
                + global_node_page_state(NR_INACTIVE_FILE);

        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 (which is a rough
 * estimate) and reserved_size divided by PAGE_SIZE (which is tunable through
 * /sys/power/reserved_size, respectively).  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 * DIV_ROUND_UP(reserved_size, PAGE_SIZE)
 *
 * 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;
        ktime_t start, stop;
        int error;

        pr_info("Preallocating image memory\n");
        start = ktime_get();

        error = memory_bm_create(&orig_bm, GFP_IMAGE, PG_ANY);
        if (error) {
                pr_err("Cannot allocate original bitmap\n");
                goto err_out;
        }

        error = memory_bm_create(&copy_bm, GFP_IMAGE, PG_ANY);
        if (error) {
                pr_err("Cannot allocate copy bitmap\n");
                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 * DIV_ROUND_UP(reserved_size, PAGE_SIZE);
        /* Compute the desired number of image pages specified by image_size. */
        size = DIV_ROUND_UP(image_size, PAGE_SIZE);
        if (size > max_size)
                size = max_size;
        /*
         * If the desired number of image pages is at least as large as 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;
        if (alloc > pages_highmem)
                alloc -= pages_highmem;
        else
                alloc = 0;
        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) {
                        pr_err("Image allocation is %lu pages short\n",
                                alloc - pages_highmem);
                        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.
         */
        pages -= free_unnecessary_pages();

 out:
        stop = ktime_get();
        pr_info("Allocated %lu pages for snapshot\n", pages);
        swsusp_show_speed(start, stop, pages, "Allocated");

        return 0;

 err_out:
        swsusp_free();
        return -ENOMEM;
}

#ifdef CONFIG_HIGHMEM
/**
 * count_pages_for_highmem - Count non-highmem pages needed for copying 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 - Check if there is enough free memory for the 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("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 - Allocate a buffer for highmem pages.
 *
 * If there are some highmem pages in the hibernation image, we may need a
 * buffer to copy them and/or load their data.
 */
static inline int get_highmem_buffer(int safe_needed)
{
        buffer = get_image_page(GFP_ATOMIC, 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 less 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|__GFP_KSWAPD_RECLAIM);
                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 hibernation 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 *copy_bm,
                        unsigned int nr_pages, unsigned int nr_highmem)
{
        if (nr_highmem > 0) {
                if (get_highmem_buffer(PG_ANY))
                        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);
                        if (!page)
                                goto err_out;
                        memory_bm_set_bit(copy_bm, page_to_pfn(page));
                }
        }

        return 0;

 err_out:
        swsusp_free();
        return -ENOMEM;
}

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

        pr_info("Creating image:\n");

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

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

        if (swsusp_alloc(&copy_bm, nr_pages, nr_highmem)) {
                pr_err("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);

        pr_info("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 const 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 = get_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 - Prepare PFNs for saving.
 * @bm: Memory bitmap.
 * @buf: Memory buffer to store the PFNs in.
 *
 * PFNs corresponding to set bits in @bm are stored in the area of memory
 * pointed to by @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 - Get the address to read the next image page from.
 * @handle: Snapshot handle to be used for the reading.
 *
 * On the first call, @handle should point to a zeroed snapshot_handle
 * structure.  The structure gets populated then 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 the data stream condition,
 * and negative numbers are returned on errors.  If that happens, 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) {
                clear_page(buffer);
                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);
                        copy_page(buffer, kaddr);
                        kunmap_atomic(kaddr);
                        handle->buffer = buffer;
                } else {
                        handle->buffer = page_address(page);
                }
        }
        handle->cur++;
        return PAGE_SIZE;
}

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);
        }
}

/**
 * mark_unsafe_pages - Mark pages that were used before hibernation.
 *
 * Mark the pages that cannot be used for storing the image during restoration,
 * because they conflict with the pages that had been used before hibernation.
 */
static void mark_unsafe_pages(struct memory_bitmap *bm)
{
        unsigned long pfn;

        /* Clear the "free"/"unsafe" bit for all PFNs */
        memory_bm_position_reset(free_pages_map);
        pfn = memory_bm_next_pfn(free_pages_map);
        while (pfn != BM_END_OF_MAP) {
                memory_bm_clear_current(free_pages_map);
                pfn = memory_bm_next_pfn(free_pages_map);
        }

        /* Mark pages that correspond to the "original" PFNs as "unsafe" */
        duplicate_memory_bitmap(free_pages_map, bm);

        allocated_unsafe_pages = 0;
}

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

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

/**
 * load header - Check the image header and copy the 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 - Set bits corresponding to given PFNs in a memory bitmap.
 * @bm: Memory bitmap.
 * @buf: Area of memory containing the PFNs.
 *
 * For each element of the array pointed to by @buf (1 page at a time), set the
 * corresponding bit in @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 (pfn_valid(buf[j]) && memory_bm_pfn_present(bm, buf[j]))
                        memory_bm_set_bit(bm, buf[j]);
                else
                        return -EFAULT;
        }

        return 0;
}

#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 image.
 * @bm: Memory bitmap.
 *
 * The bits in @bm that correspond to 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;
}

static unsigned int safe_highmem_pages;

static struct memory_bitmap *safe_highmem_bm;

/**
 * prepare_highmem_image - Allocate memory for loading highmem data from image.
 * @bm: Pointer to an uninitialized memory bitmap structure.
 * @nr_highmem_p: Pointer to the number of highmem image pages.
 *
 * 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
 * hibernation image is restored entirely) 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 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;
}

static struct page *last_highmem_page;

/**
 * get_highmem_page_buffer - Prepare a buffer to store a highmem image page.
 *
 * For a given highmem image page get a buffer that suspend_write_next() should
 * return to 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 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 = __get_safe_page(ca->gfp_mask);
                if (!kaddr)
                        return ERR_PTR(-ENOMEM);
                pbe->copy_page = virt_to_page(kaddr);
        }
        pbe->next = highmem_pblist;
        highmem_pblist = pbe;
        return kaddr;
}

/**
 * copy_last_highmem_page - Copy most the most recent highmem image page.
 *
 * Copy the contents of a highmem image from @buffer, where the caller of
 * snapshot_write_next() has stored 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);
                copy_page(dst, buffer);
                kunmap_atomic(dst);
                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 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 */

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

/**
 * prepare_image - Make room for loading hibernation image.
 * @new_bm: Unitialized memory bitmap structure.
 * @bm: Memory bitmap with unsafe pages marked.
 *
 * Use @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 image data, but without specifying what those
 * pages will be used for just yet.  Instead, we mark them all as allocated and
 * create a lists of "safe" pages to be used later.  On systems with high
 * memory a list of "safe" highmem pages is created too.
 */
static int prepare_image(struct memory_bitmap *new_bm, struct memory_bitmap *bm)
{
        unsigned int nr_pages, nr_highmem;
        struct linked_page *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);
        mark_unsafe_pages(bm);

        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.
         *
         * nr_copy_pages cannot be less than allocated_unsafe_pages too.
         */
        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 = safe_pages_list;
                safe_pages_list = lp;
                nr_pages--;
        }
        /* Preallocate memory for the image */
        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--;
        }
        return 0;

 Free:
        swsusp_free();
        return error;
}

/**
 * get_buffer - Get the address to store the next image data page.
 *
 * Get the address that snapshot_write_next() should return to 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 = __get_safe_page(ca->gfp_mask);
        if (!pbe->address)
                return ERR_PTR(-ENOMEM);
        pbe->next = restore_pblist;
        restore_pblist = pbe;
        return pbe->address;
}

/**
 * snapshot_write_next - Get the address to store the next image page.
 * @handle: Snapshot handle structure to guide the writing.
 *
 * On the first call, @handle should point to a zeroed snapshot_handle
 * structure.  The structure gets populated then 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.  Negative
 * numbers are returned on errors, in which 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;

        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;

                safe_pages_list = NULL;

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

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

/**
 * snapshot_write_finalize - Complete the loading of a hibernation image.
 *
 * 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 highmem.  Additionally, it recycles bitmap memory that's not
 * necessary any more.
 */
void snapshot_write_finalize(struct snapshot_handle *handle)
{
        copy_last_highmem_page();
        hibernate_restore_protect_page(handle->buffer);
        /* Do that only if we have loaded the image entirely */
        if (handle->cur > 1 && handle->cur > nr_meta_pages + nr_copy_pages) {
                memory_bm_recycle(&orig_bm);
                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);
        kaddr2 = kmap_atomic(p2);
        copy_page(buf, kaddr1);
        copy_page(kaddr1, kaddr2);
        copy_page(kaddr2, buf);
        kunmap_atomic(kaddr2);
        kunmap_atomic(kaddr1);
}

/**
 * restore_highmem - Put highmem image pages into their original locations.
 *
 * For each highmem page that was in use before hibernation and is included in
 * the image, and also has been allocated by the "restore" kernel, swap its
 * current contents with the previous (ie. "before hibernation") ones.
 *
 * If the restore eventually fails, we can call this function once again and
 * restore the highmem state as seen by the restore kernel.
 */
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 */