[deliverable/linux.git] / kernel / power / swap.c

/*
 * linux/kernel/power/swap.c
 *
 * This file provides functions for reading the suspend image from
 * and writing it to a swap partition.
 *
 * Copyright (C) 1998,2001-2005 Pavel Machek <pavel@ucw.cz>
 * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
 *
 * This file is released under the GPLv2.
 *
 */

#include <linux/module.h>
#include <linux/file.h>
#include <linux/delay.h>
#include <linux/bitops.h>
#include <linux/genhd.h>
#include <linux/device.h>
#include <linux/buffer_head.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/pm.h>
#include <linux/slab.h>
#include <linux/lzo.h>
#include <linux/vmalloc.h>

#include "power.h"

#define SWSUSP_SIG      "S1SUSPEND"

/*
 *      The swap map is a data structure used for keeping track of each page
 *      written to a swap partition.  It consists of many swap_map_page
 *      structures that contain each an array of MAP_PAGE_ENTRIES swap entries.
 *      These structures are stored on the swap and linked together with the
 *      help of the .next_swap member.
 *
 *      The swap map is created during suspend.  The swap map pages are
 *      allocated and populated one at a time, so we only need one memory
 *      page to set up the entire structure.
 *
 *      During resume we also only need to use one swap_map_page structure
 *      at a time.
 */

#define MAP_PAGE_ENTRIES        (PAGE_SIZE / sizeof(sector_t) - 1)

struct swap_map_page {
        sector_t entries[MAP_PAGE_ENTRIES];
        sector_t next_swap;
};

/**
 *      The swap_map_handle structure is used for handling swap in
 *      a file-alike way
 */

struct swap_map_handle {
        struct swap_map_page *cur;
        sector_t cur_swap;
        sector_t first_sector;
        unsigned int k;
};

struct swsusp_header {
        char reserved[PAGE_SIZE - 20 - sizeof(sector_t) - sizeof(int)];
        sector_t image;
        unsigned int flags;     /* Flags to pass to the "boot" kernel */
        char    orig_sig[10];
        char    sig[10];
} __attribute__((packed));

static struct swsusp_header *swsusp_header;

/**
 *      The following functions are used for tracing the allocated
 *      swap pages, so that they can be freed in case of an error.
 */

struct swsusp_extent {
        struct rb_node node;
        unsigned long start;
        unsigned long end;
};

static struct rb_root swsusp_extents = RB_ROOT;

static int swsusp_extents_insert(unsigned long swap_offset)
{
        struct rb_node **new = &(swsusp_extents.rb_node);
        struct rb_node *parent = NULL;
        struct swsusp_extent *ext;

        /* Figure out where to put the new node */
        while (*new) {
                ext = container_of(*new, struct swsusp_extent, node);
                parent = *new;
                if (swap_offset < ext->start) {
                        /* Try to merge */
                        if (swap_offset == ext->start - 1) {
                                ext->start--;
                                return 0;
                        }
                        new = &((*new)->rb_left);
                } else if (swap_offset > ext->end) {
                        /* Try to merge */
                        if (swap_offset == ext->end + 1) {
                                ext->end++;
                                return 0;
                        }
                        new = &((*new)->rb_right);
                } else {
                        /* It already is in the tree */
                        return -EINVAL;
                }
        }
        /* Add the new node and rebalance the tree. */
        ext = kzalloc(sizeof(struct swsusp_extent), GFP_KERNEL);
        if (!ext)
                return -ENOMEM;

        ext->start = swap_offset;
        ext->end = swap_offset;
        rb_link_node(&ext->node, parent, new);
        rb_insert_color(&ext->node, &swsusp_extents);
        return 0;
}

/**
 *      alloc_swapdev_block - allocate a swap page and register that it has
 *      been allocated, so that it can be freed in case of an error.
 */

sector_t alloc_swapdev_block(int swap)
{
        unsigned long offset;

        offset = swp_offset(get_swap_page_of_type(swap));
        if (offset) {
                if (swsusp_extents_insert(offset))
                        swap_free(swp_entry(swap, offset));
                else
                        return swapdev_block(swap, offset);
        }
        return 0;
}

/**
 *      free_all_swap_pages - free swap pages allocated for saving image data.
 *      It also frees the extents used to register which swap entries had been
 *      allocated.
 */

void free_all_swap_pages(int swap)
{
        struct rb_node *node;

        while ((node = swsusp_extents.rb_node)) {
                struct swsusp_extent *ext;
                unsigned long offset;

                ext = container_of(node, struct swsusp_extent, node);
                rb_erase(node, &swsusp_extents);
                for (offset = ext->start; offset <= ext->end; offset++)
                        swap_free(swp_entry(swap, offset));

                kfree(ext);
        }
}

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

/*
 * General things
 */

static unsigned short root_swap = 0xffff;
struct block_device *hib_resume_bdev;

/*
 * Saving part
 */

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

        hib_bio_read_page(swsusp_resume_block, swsusp_header, NULL);
        if (!memcmp("SWAP-SPACE",swsusp_header->sig, 10) ||
            !memcmp("SWAPSPACE2",swsusp_header->sig, 10)) {
                memcpy(swsusp_header->orig_sig,swsusp_header->sig, 10);
                memcpy(swsusp_header->sig,SWSUSP_SIG, 10);
                swsusp_header->image = handle->first_sector;
                swsusp_header->flags = flags;
                error = hib_bio_write_page(swsusp_resume_block,
                                        swsusp_header, NULL);
        } else {
                printk(KERN_ERR "PM: Swap header not found!\n");
                error = -ENODEV;
        }
        return error;
}

/**
 *      swsusp_swap_check - check if the resume device is a swap device
 *      and get its index (if so)
 *
 *      This is called before saving image
 */
static int swsusp_swap_check(void)
{
        int res;

        res = swap_type_of(swsusp_resume_device, swsusp_resume_block,
                        &hib_resume_bdev);
        if (res < 0)
                return res;

        root_swap = res;
        res = blkdev_get(hib_resume_bdev, FMODE_WRITE);
        if (res)
                return res;

        res = set_blocksize(hib_resume_bdev, PAGE_SIZE);
        if (res < 0)
                blkdev_put(hib_resume_bdev, FMODE_WRITE);

        return res;
}

/**
 *      write_page - Write one page to given swap location.
 *      @buf:           Address we're writing.
 *      @offset:        Offset of the swap page we're writing to.
 *      @bio_chain:     Link the next write BIO here
 */

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

        if (!offset)
                return -ENOSPC;

        if (bio_chain) {
                src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
                if (src) {
                        memcpy(src, buf, PAGE_SIZE);
                } else {
                        WARN_ON_ONCE(1);
                        bio_chain = NULL;       /* Go synchronous */
                        src = buf;
                }
        } else {
                src = buf;
        }
        return hib_bio_write_page(offset, src, bio_chain);
}

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

static int get_swap_writer(struct swap_map_handle *handle)
{
        int ret;

        ret = swsusp_swap_check();
        if (ret) {
                if (ret != -ENOSPC)
                        printk(KERN_ERR "PM: Cannot find swap device, try "
                                        "swapon -a.\n");
                return ret;
        }
        handle->cur = (struct swap_map_page *)get_zeroed_page(GFP_KERNEL);
        if (!handle->cur) {
                ret = -ENOMEM;
                goto err_close;
        }
        handle->cur_swap = alloc_swapdev_block(root_swap);
        if (!handle->cur_swap) {
                ret = -ENOSPC;
                goto err_rel;
        }
        handle->k = 0;
        handle->first_sector = handle->cur_swap;
        return 0;
err_rel:
        release_swap_writer(handle);
err_close:
        swsusp_close(FMODE_WRITE);
        return ret;
}

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

        if (!handle->cur)
                return -EINVAL;
        offset = alloc_swapdev_block(root_swap);
        error = write_page(buf, offset, bio_chain);
        if (error)
                return error;
        handle->cur->entries[handle->k++] = offset;
        if (handle->k >= MAP_PAGE_ENTRIES) {
                error = hib_wait_on_bio_chain(bio_chain);
                if (error)
                        goto out;
                offset = alloc_swapdev_block(root_swap);
                if (!offset)
                        return -ENOSPC;
                handle->cur->next_swap = offset;
                error = write_page(handle->cur, handle->cur_swap, NULL);
                if (error)
                        goto out;
                memset(handle->cur, 0, PAGE_SIZE);
                handle->cur_swap = offset;
                handle->k = 0;
        }
 out:
        return error;
}

static int flush_swap_writer(struct swap_map_handle *handle)
{
        if (handle->cur && handle->cur_swap)
                return write_page(handle->cur, handle->cur_swap, NULL);
        else
                return -EINVAL;
}

static int swap_writer_finish(struct swap_map_handle *handle,
                unsigned int flags, int error)
{
        if (!error) {
                flush_swap_writer(handle);
                printk(KERN_INFO "PM: S");
                error = mark_swapfiles(handle, flags);
                printk("|\n");
        }

        if (error)
                free_all_swap_pages(root_swap);
        release_swap_writer(handle);
        swsusp_close(FMODE_WRITE);

        return error;
}

/* We need to remember how much compressed data we need to read. */
#define LZO_HEADER      sizeof(size_t)

/* Number of pages/bytes we'll compress at one time. */
#define LZO_UNC_PAGES   32
#define LZO_UNC_SIZE    (LZO_UNC_PAGES * PAGE_SIZE)

/* Number of pages/bytes we need for compressed data (worst case). */
#define LZO_CMP_PAGES   DIV_ROUND_UP(lzo1x_worst_compress(LZO_UNC_SIZE) + \
                                     LZO_HEADER, PAGE_SIZE)
#define LZO_CMP_SIZE    (LZO_CMP_PAGES * PAGE_SIZE)

/**
 *      save_image - save the suspend image data
 */

static int save_image(struct swap_map_handle *handle,
                      struct snapshot_handle *snapshot,
                      unsigned int nr_to_write)
{
        unsigned int m;
        int ret;
        int nr_pages;
        int err2;
        struct bio *bio;
        struct timeval start;
        struct timeval stop;

        printk(KERN_INFO "PM: Saving image data pages (%u pages) ...     ",
                nr_to_write);
        m = nr_to_write / 100;
        if (!m)
                m = 1;
        nr_pages = 0;
        bio = NULL;
        do_gettimeofday(&start);
        while (1) {
                ret = snapshot_read_next(snapshot);
                if (ret <= 0)
                        break;
                ret = swap_write_page(handle, data_of(*snapshot), &bio);
                if (ret)
                        break;
                if (!(nr_pages % m))
                        printk(KERN_CONT "\b\b\b\b%3d%%", nr_pages / m);
                nr_pages++;
        }
        err2 = hib_wait_on_bio_chain(&bio);
        do_gettimeofday(&stop);
        if (!ret)
                ret = err2;
        if (!ret)
                printk(KERN_CONT "\b\b\b\bdone\n");
        else
                printk(KERN_CONT "\n");
        swsusp_show_speed(&start, &stop, nr_to_write, "Wrote");
        return ret;
}


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

        page = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
        if (!page) {
                printk(KERN_ERR "PM: Failed to allocate LZO page\n");
                return -ENOMEM;
        }

        wrk = vmalloc(LZO1X_1_MEM_COMPRESS);
        if (!wrk) {
                printk(KERN_ERR "PM: Failed to allocate LZO workspace\n");
                free_page((unsigned long)page);
                return -ENOMEM;
        }

        unc = vmalloc(LZO_UNC_SIZE);
        if (!unc) {
                printk(KERN_ERR "PM: Failed to allocate LZO uncompressed\n");
                vfree(wrk);
                free_page((unsigned long)page);
                return -ENOMEM;
        }

        cmp = vmalloc(LZO_CMP_SIZE);
        if (!cmp) {
                printk(KERN_ERR "PM: Failed to allocate LZO compressed\n");
                vfree(unc);
                vfree(wrk);
                free_page((unsigned long)page);
                return -ENOMEM;
        }

        printk(KERN_INFO
                "PM: Compressing and saving image data (%u pages) ...     ",
                nr_to_write);
        m = nr_to_write / 100;
        if (!m)
                m = 1;
        nr_pages = 0;
        bio = NULL;
        do_gettimeofday(&start);
        for (;;) {
                for (off = 0; off < LZO_UNC_SIZE; off += PAGE_SIZE) {
                        ret = snapshot_read_next(snapshot);
                        if (ret < 0)
                                goto out_finish;

                        if (!ret)
                                break;

                        memcpy(unc + off, data_of(*snapshot), PAGE_SIZE);

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

                if (!off)
                        break;

                unc_len = off;
                ret = lzo1x_1_compress(unc, unc_len,
                                       cmp + LZO_HEADER, &cmp_len, wrk);
                if (ret < 0) {
                        printk(KERN_ERR "PM: LZO compression failed\n");
                        break;
                }

                if (unlikely(!cmp_len ||
                             cmp_len > lzo1x_worst_compress(unc_len))) {
                        printk(KERN_ERR "PM: Invalid LZO compressed length\n");
                        ret = -1;
                        break;
                }

                *(size_t *)cmp = cmp_len;

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

                        ret = swap_write_page(handle, page, &bio);
                        if (ret)
                                goto out_finish;
                }
        }

out_finish:
        err2 = hib_wait_on_bio_chain(&bio);
        do_gettimeofday(&stop);
        if (!ret)
                ret = err2;
        if (!ret)
                printk(KERN_CONT "\b\b\b\bdone\n");
        else
                printk(KERN_CONT "\n");
        swsusp_show_speed(&start, &stop, nr_to_write, "Wrote");

        vfree(cmp);
        vfree(unc);
        vfree(wrk);
        free_page((unsigned long)page);

        return ret;
}

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

static int enough_swap(unsigned int nr_pages, unsigned int flags)
{
        unsigned int free_swap = count_swap_pages(root_swap, 1);
        unsigned int required;

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

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

/**
 *      swsusp_write - Write entire image and metadata.
 *      @flags: flags to pass to the "boot" kernel in the image header
 *
 *      It is important _NOT_ to umount filesystems at this point. We want
 *      them synced (in case something goes wrong) but we DO not want to mark
 *      filesystem clean: it is not. (And it does not matter, if we resume
 *      correctly, we'll mark system clean, anyway.)
 */

int swsusp_write(unsigned int flags)
{
        struct swap_map_handle handle;
        struct snapshot_handle snapshot;
        struct swsusp_info *header;
        unsigned long pages;
        int error;

        pages = snapshot_get_image_size();
        error = get_swap_writer(&handle);
        if (error) {
                printk(KERN_ERR "PM: Cannot get swap writer\n");
                return error;
        }
        if (!enough_swap(pages, flags)) {
                printk(KERN_ERR "PM: Not enough free swap\n");
                error = -ENOSPC;
                goto out_finish;
        }
        memset(&snapshot, 0, sizeof(struct snapshot_handle));
        error = snapshot_read_next(&snapshot);
        if (error < PAGE_SIZE) {
                if (error >= 0)
                        error = -EFAULT;

                goto out_finish;
        }
        header = (struct swsusp_info *)data_of(snapshot);
        error = swap_write_page(&handle, header, NULL);
        if (!error) {
                error = (flags & SF_NOCOMPRESS_MODE) ?
                        save_image(&handle, &snapshot, pages - 1) :
                        save_image_lzo(&handle, &snapshot, pages - 1);
        }
out_finish:
        error = swap_writer_finish(&handle, flags, error);
        return error;
}

/**
 *      The following functions allow us to read data using a swap map
 *      in a file-alike way
 */

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

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

        *flags_p = swsusp_header->flags;

        if (!swsusp_header->image) /* how can this happen? */
                return -EINVAL;

        handle->cur = (struct swap_map_page *)get_zeroed_page(__GFP_WAIT | __GFP_HIGH);
        if (!handle->cur)
                return -ENOMEM;

        error = hib_bio_read_page(swsusp_header->image, handle->cur, NULL);
        if (error) {
                release_swap_reader(handle);
                return error;
        }
        handle->k = 0;
        return 0;
}

static int swap_read_page(struct swap_map_handle *handle, void *buf,
                                struct bio **bio_chain)
{
        sector_t offset;
        int error;

        if (!handle->cur)
                return -EINVAL;
        offset = handle->cur->entries[handle->k];
        if (!offset)
                return -EFAULT;
        error = hib_bio_read_page(offset, buf, bio_chain);
        if (error)
                return error;
        if (++handle->k >= MAP_PAGE_ENTRIES) {
                error = hib_wait_on_bio_chain(bio_chain);
                handle->k = 0;
                offset = handle->cur->next_swap;
                if (!offset)
                        release_swap_reader(handle);
                else if (!error)
                        error = hib_bio_read_page(offset, handle->cur, NULL);
        }
        return error;
}

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

        return 0;
}

/**
 *      load_image - load the image using the swap map handle
 *      @handle and the snapshot handle @snapshot
 *      (assume there are @nr_pages pages to load)
 */

static int load_image(struct swap_map_handle *handle,
                      struct snapshot_handle *snapshot,
                      unsigned int nr_to_read)
{
        unsigned int m;
        int error = 0;
        struct timeval start;
        struct timeval stop;
        struct bio *bio;
        int err2;
        unsigned nr_pages;

        printk(KERN_INFO "PM: Loading image data pages (%u pages) ...     ",
                nr_to_read);
        m = nr_to_read / 100;
        if (!m)
                m = 1;
        nr_pages = 0;
        bio = NULL;
        do_gettimeofday(&start);
        for ( ; ; ) {
                error = snapshot_write_next(snapshot);
                if (error <= 0)
                        break;
                error = swap_read_page(handle, data_of(*snapshot), &bio);
                if (error)
                        break;
                if (snapshot->sync_read)
                        error = hib_wait_on_bio_chain(&bio);
                if (error)
                        break;
                if (!(nr_pages % m))
                        printk("\b\b\b\b%3d%%", nr_pages / m);
                nr_pages++;
        }
        err2 = hib_wait_on_bio_chain(&bio);
        do_gettimeofday(&stop);
        if (!error)
                error = err2;
        if (!error) {
                printk("\b\b\b\bdone\n");
                snapshot_write_finalize(snapshot);
                if (!snapshot_image_loaded(snapshot))
                        error = -ENODATA;
        } else
                printk("\n");
        swsusp_show_speed(&start, &stop, nr_to_read, "Read");
        return error;
}

/**
 * load_image_lzo - Load compressed image data and decompress them with LZO.
 * @handle: Swap map handle to use for loading data.
 * @snapshot: Image to copy uncompressed data into.
 * @nr_to_read: Number of pages to load.
 */
static int load_image_lzo(struct swap_map_handle *handle,
                          struct snapshot_handle *snapshot,
                          unsigned int nr_to_read)
{
        unsigned int m;
        int error = 0;
        struct timeval start;
        struct timeval stop;
        unsigned nr_pages;
        size_t off, unc_len, cmp_len;
        unsigned char *unc, *cmp, *page;

        page = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
        if (!page) {
                printk(KERN_ERR "PM: Failed to allocate LZO page\n");
                return -ENOMEM;
        }

        unc = vmalloc(LZO_UNC_SIZE);
        if (!unc) {
                printk(KERN_ERR "PM: Failed to allocate LZO uncompressed\n");
                free_page((unsigned long)page);
                return -ENOMEM;
        }

        cmp = vmalloc(LZO_CMP_SIZE);
        if (!cmp) {
                printk(KERN_ERR "PM: Failed to allocate LZO compressed\n");
                vfree(unc);
                free_page((unsigned long)page);
                return -ENOMEM;
        }

        printk(KERN_INFO
                "PM: Loading and decompressing image data (%u pages) ...     ",
                nr_to_read);
        m = nr_to_read / 100;
        if (!m)
                m = 1;
        nr_pages = 0;
        do_gettimeofday(&start);

        error = snapshot_write_next(snapshot);
        if (error <= 0)
                goto out_finish;

        for (;;) {
                error = swap_read_page(handle, page, NULL); /* sync */
                if (error)
                        break;

                cmp_len = *(size_t *)page;
                if (unlikely(!cmp_len ||
                             cmp_len > lzo1x_worst_compress(LZO_UNC_SIZE))) {
                        printk(KERN_ERR "PM: Invalid LZO compressed length\n");
                        error = -1;
                        break;
                }

                memcpy(cmp, page, PAGE_SIZE);
                for (off = PAGE_SIZE; off < LZO_HEADER + cmp_len; off += PAGE_SIZE) {
                        error = swap_read_page(handle, page, NULL); /* sync */
                        if (error)
                                goto out_finish;

                        memcpy(cmp + off, page, PAGE_SIZE);
                }

                unc_len = LZO_UNC_SIZE;
                error = lzo1x_decompress_safe(cmp + LZO_HEADER, cmp_len,
                                              unc, &unc_len);
                if (error < 0) {
                        printk(KERN_ERR "PM: LZO decompression failed\n");
                        break;
                }

                if (unlikely(!unc_len ||
                             unc_len > LZO_UNC_SIZE ||
                             unc_len & (PAGE_SIZE - 1))) {
                        printk(KERN_ERR "PM: Invalid LZO uncompressed length\n");
                        error = -1;
                        break;
                }

                for (off = 0; off < unc_len; off += PAGE_SIZE) {
                        memcpy(data_of(*snapshot), unc + off, PAGE_SIZE);

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

                        error = snapshot_write_next(snapshot);
                        if (error <= 0)
                                goto out_finish;
                }
        }

out_finish:
        do_gettimeofday(&stop);
        if (!error) {
                printk("\b\b\b\bdone\n");
                snapshot_write_finalize(snapshot);
                if (!snapshot_image_loaded(snapshot))
                        error = -ENODATA;
        } else
                printk("\n");
        swsusp_show_speed(&start, &stop, nr_to_read, "Read");

        vfree(cmp);
        vfree(unc);
        free_page((unsigned long)page);

        return error;
}

/**
 *      swsusp_read - read the hibernation image.
 *      @flags_p: flags passed by the "frozen" kernel in the image header should
 *                be written into this memeory location
 */

int swsusp_read(unsigned int *flags_p)
{
        int error;
        struct swap_map_handle handle;
        struct snapshot_handle snapshot;
        struct swsusp_info *header;

        memset(&snapshot, 0, sizeof(struct snapshot_handle));
        error = snapshot_write_next(&snapshot);
        if (error < PAGE_SIZE)
                return error < 0 ? error : -EFAULT;
        header = (struct swsusp_info *)data_of(snapshot);
        error = get_swap_reader(&handle, flags_p);
        if (error)
                goto end;
        if (!error)
                error = swap_read_page(&handle, header, NULL);
        if (!error) {
                error = (*flags_p & SF_NOCOMPRESS_MODE) ?
                        load_image(&handle, &snapshot, header->pages - 1) :
                        load_image_lzo(&handle, &snapshot, header->pages - 1);
        }
        swap_reader_finish(&handle);
end:
        if (!error)
                pr_debug("PM: Image successfully loaded\n");
        else
                pr_debug("PM: Error %d resuming\n", error);
        return error;
}

/**
 *      swsusp_check - Check for swsusp signature in the resume device
 */

int swsusp_check(void)
{
        int error;

        hib_resume_bdev = open_by_devnum(swsusp_resume_device, FMODE_READ);
        if (!IS_ERR(hib_resume_bdev)) {
                set_blocksize(hib_resume_bdev, PAGE_SIZE);
                memset(swsusp_header, 0, PAGE_SIZE);
                error = hib_bio_read_page(swsusp_resume_block,
                                        swsusp_header, NULL);
                if (error)
                        goto put;

                if (!memcmp(SWSUSP_SIG, swsusp_header->sig, 10)) {
                        memcpy(swsusp_header->sig, swsusp_header->orig_sig, 10);
                        /* Reset swap signature now */
                        error = hib_bio_write_page(swsusp_resume_block,
                                                swsusp_header, NULL);
                } else {
                        error = -EINVAL;
                }

put:
                if (error)
                        blkdev_put(hib_resume_bdev, FMODE_READ);
                else
                        pr_debug("PM: Image signature found, resuming\n");
        } else {
                error = PTR_ERR(hib_resume_bdev);
        }

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

        return error;
}

/**
 *      swsusp_close - close swap device.
 */

void swsusp_close(fmode_t mode)
{
        if (IS_ERR(hib_resume_bdev)) {
                pr_debug("PM: Image device not initialised\n");
                return;
        }

        blkdev_put(hib_resume_bdev, mode);
}

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

core_initcall(swsusp_header_init);