Avoid beyond bounds copy while caching ACL

[zen-stable.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>
 * Copyright (C) 2010 Bojan Smojver <bojan@rexursive.com>
 *
 * This file is released under the GPLv2.
 *
 */

#include <linux/module.h>
#include <linux/file.h>
#include <linux/delay.h>
#include <linux/bitops.h>
#include <linux/genhd.h>
#include <linux/device.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/pm.h>
#include <linux/slab.h>
#include <linux/lzo.h>
#include <linux/vmalloc.h>
#include <linux/cpumask.h>
#include <linux/atomic.h>
#include <linux/kthread.h>
#include <linux/crc32.h>

#include "power.h"

#define HIBERNATE_SIG   "S1SUSPEND"

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

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

/*
 * Number of free pages that are not high.
 */
static inline unsigned long low_free_pages(void)
{
        return nr_free_pages() - nr_free_highpages();
}

/*
 * Number of pages required to be kept free while writing the image. Always
 * half of all available low pages before the writing starts.
 */
static inline unsigned long reqd_free_pages(void)
{
        return low_free_pages() / 2;
}

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

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

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

struct swap_map_handle {
        struct swap_map_page *cur;
        struct swap_map_page_list *maps;
        sector_t cur_swap;
        sector_t first_sector;
        unsigned int k;
        unsigned long reqd_free_pages;
        u32 crc32;
};

struct swsusp_header {
        char reserved[PAGE_SIZE - 20 - sizeof(sector_t) - sizeof(int) -
                      sizeof(u32)];
        u32     crc32;
        sector_t image;
        unsigned int flags;     /* Flags to pass to the "boot" kernel */
        char    orig_sig[10];
        char    sig[10];
} __attribute__((packed));

static struct swsusp_header *swsusp_header;

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

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

static struct rb_root swsusp_extents = RB_ROOT;

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

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

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

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

sector_t alloc_swapdev_block(int swap)
{
        unsigned long offset;

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

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

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

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

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

                kfree(ext);
        }
}

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

/*
 * General things
 */

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

/*
 * Saving part
 */

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

        hib_bio_read_page(swsusp_resume_block, swsusp_header, NULL);
        if (!memcmp("SWAP-SPACE",swsusp_header->sig, 10) ||
            !memcmp("SWAPSPACE2",swsusp_header->sig, 10)) {
                memcpy(swsusp_header->orig_sig,swsusp_header->sig, 10);
                memcpy(swsusp_header->sig, HIBERNATE_SIG, 10);
                swsusp_header->image = handle->first_sector;
                swsusp_header->flags = flags;
                if (flags & SF_CRC32_MODE)
                        swsusp_header->crc32 = handle->crc32;
                error = hib_bio_write_page(swsusp_resume_block,
                                        swsusp_header, NULL);
        } else {
                printk(KERN_ERR "PM: Swap header not found!\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, NULL);
        if (res)
                return res;

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

        return res;
}

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

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

        if (!offset)
                return -ENOSPC;

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

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

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

        ret = swsusp_swap_check();
        if (ret) {
                if (ret != -ENOSPC)
                        printk(KERN_ERR "PM: Cannot find swap device, try "
                                        "swapon -a.\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->reqd_free_pages = reqd_free_pages();
        handle->first_sector = handle->cur_swap;
        return 0;
err_rel:
        release_swap_writer(handle);
err_close:
        swsusp_close(FMODE_WRITE);
        return ret;
}

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

        if (!handle->cur)
                return -EINVAL;
        offset = alloc_swapdev_block(root_swap);
        error = write_page(buf, offset, bio_chain);
        if (error)
                return error;
        handle->cur->entries[handle->k++] = offset;
        if (handle->k >= MAP_PAGE_ENTRIES) {
                offset = alloc_swapdev_block(root_swap);
                if (!offset)
                        return -ENOSPC;
                handle->cur->next_swap = offset;
                error = write_page(handle->cur, handle->cur_swap, bio_chain);
                if (error)
                        goto out;
                clear_page(handle->cur);
                handle->cur_swap = offset;
                handle->k = 0;
        }
        if (bio_chain && low_free_pages() <= handle->reqd_free_pages) {
                error = hib_wait_on_bio_chain(bio_chain);
                if (error)
                        goto out;
                handle->reqd_free_pages = reqd_free_pages();
        }
 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)

/* Maximum number of threads for compression/decompression. */
#define LZO_THREADS     3

/* Maximum number of pages for read buffering. */
#define LZO_READ_PAGES  (MAP_PAGE_ENTRIES * 8)


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

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

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

/**
 * Structure used for CRC32.
 */
struct crc_data {
        struct task_struct *thr;                  /* thread */
        atomic_t ready;                           /* ready to start flag */
        atomic_t stop;                            /* ready to stop flag */
        unsigned run_threads;                     /* nr current threads */
        wait_queue_head_t go;                     /* start crc update */
        wait_queue_head_t done;                   /* crc update done */
        u32 *crc32;                               /* points to handle's crc32 */
        size_t *unc_len[LZO_THREADS];             /* uncompressed lengths */
        unsigned char *unc[LZO_THREADS];          /* uncompressed data */
};

/**
 * CRC32 update function that runs in its own thread.
 */
static int crc32_threadfn(void *data)
{
        struct crc_data *d = data;
        unsigned i;

        while (1) {
                wait_event(d->go, atomic_read(&d->ready) ||
                                  kthread_should_stop());
                if (kthread_should_stop()) {
                        d->thr = NULL;
                        atomic_set(&d->stop, 1);
                        wake_up(&d->done);
                        break;
                }
                atomic_set(&d->ready, 0);

                for (i = 0; i < d->run_threads; i++)
                        *d->crc32 = crc32_le(*d->crc32,
                                             d->unc[i], *d->unc_len[i]);
                atomic_set(&d->stop, 1);
                wake_up(&d->done);
        }
        return 0;
}
/**
 * Structure used for LZO data compression.
 */
struct cmp_data {
        struct task_struct *thr;                  /* thread */
        atomic_t ready;                           /* ready to start flag */
        atomic_t stop;                            /* ready to stop flag */
        int ret;                                  /* return code */
        wait_queue_head_t go;                     /* start compression */
        wait_queue_head_t done;                   /* compression done */
        size_t unc_len;                           /* uncompressed length */
        size_t cmp_len;                           /* compressed length */
        unsigned char unc[LZO_UNC_SIZE];          /* uncompressed buffer */
        unsigned char cmp[LZO_CMP_SIZE];          /* compressed buffer */
        unsigned char wrk[LZO1X_1_MEM_COMPRESS];  /* compression workspace */
};

/**
 * Compression function that runs in its own thread.
 */
static int lzo_compress_threadfn(void *data)
{
        struct cmp_data *d = data;

        while (1) {
                wait_event(d->go, atomic_read(&d->ready) ||
                                  kthread_should_stop());
                if (kthread_should_stop()) {
                        d->thr = NULL;
                        d->ret = -1;
                        atomic_set(&d->stop, 1);
                        wake_up(&d->done);
                        break;
                }
                atomic_set(&d->ready, 0);

                d->ret = lzo1x_1_compress(d->unc, d->unc_len,
                                          d->cmp + LZO_HEADER, &d->cmp_len,
                                          d->wrk);
                atomic_set(&d->stop, 1);
                wake_up(&d->done);
        }
        return 0;
}

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

        /*
         * We'll limit the number of threads for compression to limit memory
         * footprint.
         */
        nr_threads = num_online_cpus() - 1;
        nr_threads = clamp_val(nr_threads, 1, LZO_THREADS);

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

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

        crc = kmalloc(sizeof(*crc), GFP_KERNEL);
        if (!crc) {
                printk(KERN_ERR "PM: Failed to allocate crc\n");
                ret = -ENOMEM;
                goto out_clean;
        }
        memset(crc, 0, offsetof(struct crc_data, go));

        /*
         * Start the compression threads.
         */
        for (thr = 0; thr < nr_threads; thr++) {
                init_waitqueue_head(&data[thr].go);
                init_waitqueue_head(&data[thr].done);

                data[thr].thr = kthread_run(lzo_compress_threadfn,
                                            &data[thr],
                                            "image_compress/%u", thr);
                if (IS_ERR(data[thr].thr)) {
                        data[thr].thr = NULL;
                        printk(KERN_ERR
                               "PM: Cannot start compression threads\n");
                        ret = -ENOMEM;
                        goto out_clean;
                }
        }

        /*
         * Adjust number of free pages after all allocations have been done.
         * We don't want to run out of pages when writing.
         */
        handle->reqd_free_pages = reqd_free_pages();

        /*
         * Start the CRC32 thread.
         */
        init_waitqueue_head(&crc->go);
        init_waitqueue_head(&crc->done);

        handle->crc32 = 0;
        crc->crc32 = &handle->crc32;
        for (thr = 0; thr < nr_threads; thr++) {
                crc->unc[thr] = data[thr].unc;
                crc->unc_len[thr] = &data[thr].unc_len;
        }

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

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

                                if (!ret)
                                        break;

                                memcpy(data[thr].unc + off,
                                       data_of(*snapshot), PAGE_SIZE);

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

                        data[thr].unc_len = off;

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

                if (!thr)
                        break;

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

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

                        ret = data[thr].ret;

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

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

                        *(size_t *)data[thr].cmp = data[thr].cmp_len;

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

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

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

out_finish:
        err2 = hib_wait_on_bio_chain(&bio);
        do_gettimeofday(&stop);
        if (!ret)
                ret = err2;
        if (!ret) {
                printk(KERN_CONT "\b\b\b\bdone\n");
        } else {
                printk(KERN_CONT "\n");
        }
        swsusp_show_speed(&start, &stop, nr_to_write, "Wrote");
out_clean:
        if (crc) {
                if (crc->thr)
                        kthread_stop(crc->thr);
                kfree(crc);
        }
        if (data) {
                for (thr = 0; thr < nr_threads; thr++)
                        if (data[thr].thr)
                                kthread_stop(data[thr].thr);
                vfree(data);
        }
        if (page) free_page((unsigned long)page);

        return ret;
}

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

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

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

        required = PAGES_FOR_IO + nr_pages;
        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 (flags & SF_NOCOMPRESS_MODE) {
                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)
{
        struct swap_map_page_list *tmp;

        while (handle->maps) {
                if (handle->maps->map)
                        free_page((unsigned long)handle->maps->map);
                tmp = handle->maps;
                handle->maps = handle->maps->next;
                kfree(tmp);
        }
        handle->cur = NULL;
}

static int get_swap_reader(struct swap_map_handle *handle,
                unsigned int *flags_p)
{
        int error;
        struct swap_map_page_list *tmp, *last;
        sector_t offset;

        *flags_p = swsusp_header->flags;

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

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

                tmp->map = (struct swap_map_page *)
                           __get_free_page(__GFP_WAIT | __GFP_HIGH);
                if (!tmp->map) {
                        release_swap_reader(handle);
                        return -ENOMEM;
                }

                error = hib_bio_read_page(offset, tmp->map, NULL);
                if (error) {
                        release_swap_reader(handle);
                        return error;
                }
                offset = tmp->map->next_swap;
        }
        handle->k = 0;
        handle->cur = handle->maps->map;
        return 0;
}

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

        if (!handle->cur)
                return -EINVAL;
        offset = handle->cur->entries[handle->k];
        if (!offset)
                return -EFAULT;
        error = hib_bio_read_page(offset, buf, bio_chain);
        if (error)
                return error;
        if (++handle->k >= MAP_PAGE_ENTRIES) {
                handle->k = 0;
                free_page((unsigned long)handle->maps->map);
                tmp = handle->maps;
                handle->maps = handle->maps->next;
                kfree(tmp);
                if (!handle->maps)
                        release_swap_reader(handle);
                else
                        handle->cur = handle->maps->map;
        }
        return error;
}

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

        return 0;
}

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

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

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

/**
 * Structure used for LZO data decompression.
 */
struct dec_data {
        struct task_struct *thr;                  /* thread */
        atomic_t ready;                           /* ready to start flag */
        atomic_t stop;                            /* ready to stop flag */
        int ret;                                  /* return code */
        wait_queue_head_t go;                     /* start decompression */
        wait_queue_head_t done;                   /* decompression done */
        size_t unc_len;                           /* uncompressed length */
        size_t cmp_len;                           /* compressed length */
        unsigned char unc[LZO_UNC_SIZE];          /* uncompressed buffer */
        unsigned char cmp[LZO_CMP_SIZE];          /* compressed buffer */
};

/**
 * Deompression function that runs in its own thread.
 */
static int lzo_decompress_threadfn(void *data)
{
        struct dec_data *d = data;

        while (1) {
                wait_event(d->go, atomic_read(&d->ready) ||
                                  kthread_should_stop());
                if (kthread_should_stop()) {
                        d->thr = NULL;
                        d->ret = -1;
                        atomic_set(&d->stop, 1);
                        wake_up(&d->done);
                        break;
                }
                atomic_set(&d->ready, 0);

                d->unc_len = LZO_UNC_SIZE;
                d->ret = lzo1x_decompress_safe(d->cmp + LZO_HEADER, d->cmp_len,
                                               d->unc, &d->unc_len);
                atomic_set(&d->stop, 1);
                wake_up(&d->done);
        }
        return 0;
}

/**
 * load_image_lzo - Load compressed image data and decompress them with LZO.
 * @handle: Swap map handle to use for loading data.
 * @snapshot: Image to copy uncompressed data into.
 * @nr_to_read: Number of pages to load.
 */
static int load_image_lzo(struct swap_map_handle *handle,
                          struct snapshot_handle *snapshot,
                          unsigned int nr_to_read)
{
        unsigned int m;
        int ret = 0;
        int eof = 0;
        struct bio *bio;
        struct timeval start;
        struct timeval stop;
        unsigned nr_pages;
        size_t off;
        unsigned i, thr, run_threads, nr_threads;
        unsigned ring = 0, pg = 0, ring_size = 0,
                 have = 0, want, need, asked = 0;
        unsigned long read_pages;
        unsigned char **page = NULL;
        struct dec_data *data = NULL;
        struct crc_data *crc = NULL;

        /*
         * We'll limit the number of threads for decompression to limit memory
         * footprint.
         */
        nr_threads = num_online_cpus() - 1;
        nr_threads = clamp_val(nr_threads, 1, LZO_THREADS);

        page = vmalloc(sizeof(*page) * LZO_READ_PAGES);
        if (!page) {
                printk(KERN_ERR "PM: Failed to allocate LZO page\n");
                ret = -ENOMEM;
                goto out_clean;
        }

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

        crc = kmalloc(sizeof(*crc), GFP_KERNEL);
        if (!crc) {
                printk(KERN_ERR "PM: Failed to allocate crc\n");
                ret = -ENOMEM;
                goto out_clean;
        }
        memset(crc, 0, offsetof(struct crc_data, go));

        /*
         * Start the decompression threads.
         */
        for (thr = 0; thr < nr_threads; thr++) {
                init_waitqueue_head(&data[thr].go);
                init_waitqueue_head(&data[thr].done);

                data[thr].thr = kthread_run(lzo_decompress_threadfn,
                                            &data[thr],
                                            "image_decompress/%u", thr);
                if (IS_ERR(data[thr].thr)) {
                        data[thr].thr = NULL;
                        printk(KERN_ERR
                               "PM: Cannot start decompression threads\n");
                        ret = -ENOMEM;
                        goto out_clean;
                }
        }

        /*
         * Start the CRC32 thread.
         */
        init_waitqueue_head(&crc->go);
        init_waitqueue_head(&crc->done);

        handle->crc32 = 0;
        crc->crc32 = &handle->crc32;
        for (thr = 0; thr < nr_threads; thr++) {
                crc->unc[thr] = data[thr].unc;
                crc->unc_len[thr] = &data[thr].unc_len;
        }

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

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

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

        printk(KERN_INFO
                "PM: Using %u thread(s) for decompression.\n"
                "PM: Loading and decompressing image data (%u pages) ...     ",
                nr_threads, nr_to_read);
        m = nr_to_read / 100;
        if (!m)
                m = 1;
        nr_pages = 0;
        bio = NULL;
        do_gettimeofday(&start);

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

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

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

                        ret = hib_wait_on_bio_chain(&bio);
                        if (ret)
                                goto out_finish;
                        have += asked;
                        asked = 0;
                        if (eof)
                                eof = 2;
                }

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

                for (thr = 0; have && thr < nr_threads; thr++) {
                        data[thr].cmp_len = *(size_t *)page[pg];
                        if (unlikely(!data[thr].cmp_len ||
                                     data[thr].cmp_len >
                                     lzo1x_worst_compress(LZO_UNC_SIZE))) {
                                printk(KERN_ERR
                                       "PM: Invalid LZO compressed length\n");
                                ret = -1;
                                goto out_finish;
                        }

                        need = DIV_ROUND_UP(data[thr].cmp_len + LZO_HEADER,
                                            PAGE_SIZE);
                        if (need > have) {
                                if (eof > 1) {
                                        ret = -1;
                                        goto out_finish;
                                }
                                break;
                        }

                        for (off = 0;
                             off < LZO_HEADER + data[thr].cmp_len;
                             off += PAGE_SIZE) {
                                memcpy(data[thr].cmp + off,
                                       page[pg], PAGE_SIZE);
                                have--;
                                want++;
                                if (++pg >= ring_size)
                                        pg = 0;
                        }

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

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

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

                        ret = data[thr].ret;

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

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

                        for (off = 0;
                             off < data[thr].unc_len; off += PAGE_SIZE) {
                                memcpy(data_of(*snapshot),
                                       data[thr].unc + off, PAGE_SIZE);

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

                                ret = snapshot_write_next(snapshot);
                                if (ret <= 0) {
                                        crc->run_threads = thr + 1;
                                        atomic_set(&crc->ready, 1);
                                        wake_up(&crc->go);
                                        goto out_finish;
                                }
                        }
                }

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

out_finish:
        if (crc->run_threads) {
                wait_event(crc->done, atomic_read(&crc->stop));
                atomic_set(&crc->stop, 0);
        }
        do_gettimeofday(&stop);
        if (!ret) {
                printk("\b\b\b\bdone\n");
                snapshot_write_finalize(snapshot);
                if (!snapshot_image_loaded(snapshot))
                        ret = -ENODATA;
                if (!ret) {
                        if (swsusp_header->flags & SF_CRC32_MODE) {
                                if(handle->crc32 != swsusp_header->crc32) {
                                        printk(KERN_ERR
                                               "PM: Invalid image CRC32!\n");
                                        ret = -ENODATA;
                                }
                        }
                }
        } else
                printk("\n");
        swsusp_show_speed(&start, &stop, nr_to_read, "Read");
out_clean:
        for (i = 0; i < ring_size; i++)
                free_page((unsigned long)page[i]);
        if (crc) {
                if (crc->thr)
                        kthread_stop(crc->thr);
                kfree(crc);
        }
        if (data) {
                for (thr = 0; thr < nr_threads; thr++)
                        if (data[thr].thr)
                                kthread_stop(data[thr].thr);
                vfree(data);
        }
        if (page) vfree(page);

        return ret;
}

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

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

        memset(&snapshot, 0, sizeof(struct snapshot_handle));
        error = snapshot_write_next(&snapshot);
        if (error < PAGE_SIZE)
                return error < 0 ? error : -EFAULT;
        header = (struct swsusp_info *)data_of(snapshot);
        error = get_swap_reader(&handle, flags_p);
        if (error)
                goto end;
        if (!error)
                error = swap_read_page(&handle, header, NULL);
        if (!error) {
                error = (*flags_p & SF_NOCOMPRESS_MODE) ?
                        load_image(&handle, &snapshot, header->pages - 1) :
                        load_image_lzo(&handle, &snapshot, header->pages - 1);
        }
        swap_reader_finish(&handle);
end:
        if (!error)
                pr_debug("PM: Image successfully loaded\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 = blkdev_get_by_dev(swsusp_resume_device,
                                            FMODE_READ, NULL);
        if (!IS_ERR(hib_resume_bdev)) {
                set_blocksize(hib_resume_bdev, PAGE_SIZE);
                clear_page(swsusp_header);
                error = hib_bio_read_page(swsusp_resume_block,
                                        swsusp_header, NULL);
                if (error)
                        goto put;

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

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