/*
 * 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@suse.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 "power.h"

#define SWSUSP_SIG      "S1SUSPEND"

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;

/*
 * General things
 */

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

/**
 *      submit - submit BIO request.
 *      @rw:    READ or WRITE.
 *      @off    physical offset of page.
 *      @page:  page we're reading or writing.
 *      @bio_chain: list of pending biod (for async reading)
 *
 *      Straight from the textbook - allocate and initialize the bio.
 *      If we're reading, make sure the page is marked as dirty.
 *      Then submit it and, if @bio_chain == NULL, wait.
 */
static int submit(int rw, pgoff_t page_off, struct page *page,
                        struct bio **bio_chain)
{
        const int bio_rw = rw | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
        struct bio *bio;

        bio = bio_alloc(__GFP_WAIT | __GFP_HIGH, 1);
        bio->bi_sector = page_off * (PAGE_SIZE >> 9);
        bio->bi_bdev = resume_bdev;
        bio->bi_end_io = end_swap_bio_read;

        if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE) {
                printk(KERN_ERR "PM: Adding page to bio failed at %ld\n",
                        page_off);
                bio_put(bio);
                return -EFAULT;
        }

        lock_page(page);
        bio_get(bio);

        if (bio_chain == NULL) {
                submit_bio(bio_rw, bio);
                wait_on_page_locked(page);
                if (rw == READ)
                        bio_set_pages_dirty(bio);
                bio_put(bio);
        } else {
                if (rw == READ)
                        get_page(page); /* These pages are freed later */
                bio->bi_private = *bio_chain;
                *bio_chain = bio;
                submit_bio(bio_rw, bio);
        }
        return 0;
}

static int bio_read_page(pgoff_t page_off, void *addr, struct bio **bio_chain)
{
        return submit(READ, page_off, virt_to_page(addr), bio_chain);
}

static int bio_write_page(pgoff_t page_off, void *addr, struct bio **bio_chain)
{
        return submit(WRITE, page_off, virt_to_page(addr), bio_chain);
}

static int wait_on_bio_chain(struct bio **bio_chain)
{
        struct bio *bio;
        struct bio *next_bio;
        int ret = 0;

        if (bio_chain == NULL)
                return 0;

        bio = *bio_chain;
        if (bio == NULL)
                return 0;
        while (bio) {
                struct page *page;

                next_bio = bio->bi_private;
                page = bio->bi_io_vec[0].bv_page;
                wait_on_page_locked(page);
                if (!PageUptodate(page) || PageError(page))
                        ret = -EIO;
                put_page(page);
                bio_put(bio);
                bio = next_bio;
        }
        *bio_chain = NULL;
        return ret;
}

/*
 * Saving part
 */

static int mark_swapfiles(sector_t start, unsigned int flags)
{
        int error;

        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 = start;
                swsusp_header->flags = flags;
                error = 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)
 */

static int swsusp_swap_check(void) /* This is called before saving image */
{
        int res;

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

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

        res = set_blocksize(resume_bdev, PAGE_SIZE);
        if (res < 0)
                blkdev_put(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 bio_write_page(offset, src, bio_chain);
}

/*
 *      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_SIZE 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;
        unsigned int k;
};

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)
{
        handle->cur = (struct swap_map_page *)get_zeroed_page(GFP_KERNEL);
        if (!handle->cur)
                return -ENOMEM;
        handle->cur_swap = alloc_swapdev_block(root_swap);
        if (!handle->cur_swap) {
                release_swap_writer(handle);
                return -ENOSPC;
        }
        handle->k = 0;
        return 0;
}

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 = 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;
}

/**
 *      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, PAGE_SIZE);
                if (ret <= 0)
                        break;
                ret = swap_write_page(handle, data_of(*snapshot), &bio);
                if (ret)
                        break;
                if (!(nr_pages % m))
                        printk("\b\b\b\b%3d%%", nr_pages / m);
                nr_pages++;
        }
        err2 = wait_on_bio_chain(&bio);
        do_gettimeofday(&stop);
        if (!ret)
                ret = err2;
        if (!ret)
                printk("\b\b\b\bdone\n");
        else
                printk("\n");
        swsusp_show_speed(&start, &stop, nr_to_write, "Wrote");
        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 free_swap = count_swap_pages(root_swap, 1);

        pr_debug("PM: Free swap pages: %u\n", free_swap);
        return free_swap > nr_pages + PAGES_FOR_IO;
}

/**
 *      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;
        int error;

        error = swsusp_swap_check();
        if (error) {
                printk(KERN_ERR "PM: Cannot find swap device, try "
                                "swapon -a.\n");
                return error;
        }
        memset(&snapshot, 0, sizeof(struct snapshot_handle));
        error = snapshot_read_next(&snapshot, PAGE_SIZE);
        if (error < PAGE_SIZE) {
                if (error >= 0)
                        error = -EFAULT;

                goto out;
        }
        header = (struct swsusp_info *)data_of(snapshot);
        if (!enough_swap(header->pages)) {
                printk(KERN_ERR "PM: Not enough free swap\n");
                error = -ENOSPC;
                goto out;
        }
        error = get_swap_writer(&handle);
        if (!error) {
                sector_t start = handle.cur_swap;

                error = swap_write_page(&handle, header, NULL);
                if (!error)
                        error = save_image(&handle, &snapshot,
                                        header->pages - 1);

                if (!error) {
                        flush_swap_writer(&handle);
                        printk(KERN_INFO "PM: S");
                        error = mark_swapfiles(start, flags);
                        printk("|\n");
                }
        }
        if (error)
                free_all_swap_pages(root_swap);

        release_swap_writer(&handle);
 out:
        swsusp_close(FMODE_WRITE);
        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, sector_t start)
{
        int error;

        if (!start)
                return -EINVAL;

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

        error = bio_read_page(start, 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 = bio_read_page(offset, buf, bio_chain);
        if (error)
                return error;
        if (++handle->k >= MAP_PAGE_ENTRIES) {
                error = wait_on_bio_chain(bio_chain);
                handle->k = 0;
                offset = handle->cur->next_swap;
                if (!offset)
                        release_swap_reader(handle);
                else if (!error)
                        error = bio_read_page(offset, handle->cur, NULL);
        }
        return error;
}

/**
 *      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, PAGE_SIZE);
                if (error <= 0)
                        break;
                error = swap_read_page(handle, data_of(*snapshot), &bio);
                if (error)
                        break;
                if (snapshot->sync_read)
                        error = wait_on_bio_chain(&bio);
                if (error)
                        break;
                if (!(nr_pages % m))
                        printk("\b\b\b\b%3d%%", nr_pages / m);
                nr_pages++;
        }
        err2 = 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;
}

/**
 *      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;

        *flags_p = swsusp_header->flags;
        if (IS_ERR(resume_bdev)) {
                pr_debug("PM: Image device not initialised\n");
                return PTR_ERR(resume_bdev);
        }

        memset(&snapshot, 0, sizeof(struct snapshot_handle));
        error = snapshot_write_next(&snapshot, PAGE_SIZE);
        if (error < PAGE_SIZE)
                return error < 0 ? error : -EFAULT;
        header = (struct swsusp_info *)data_of(snapshot);
        error = get_swap_reader(&handle, swsusp_header->image);
        if (!error)
                error = swap_read_page(&handle, header, NULL);
        if (!error)
                error = load_image(&handle, &snapshot, header->pages - 1);
        release_swap_reader(&handle);

        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;

        resume_bdev = open_by_devnum(swsusp_resume_device, FMODE_READ);
        if (!IS_ERR(resume_bdev)) {
                set_blocksize(resume_bdev, PAGE_SIZE);
                memset(swsusp_header, 0, PAGE_SIZE);
                error = 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 = bio_write_page(swsusp_resume_block,
                                                swsusp_header, NULL);
                } else {
                        error = -EINVAL;
                }

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

        if (error)
                pr_debug("PM: Error %d checking image file\n", error);

        return error;
}

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

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

        blkdev_put(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);