/*
 * kernel/power/pmdisk.c - Suspend-to-disk implmentation
 *
 * This STD implementation is initially derived from swsusp (suspend-to-swap).
 * The original copyright on that was: 
 *
 * Copyright (C) 1998-2001 Gabor Kuti <seasons@fornax.hu>
 * Copyright (C) 1998,2001,2002 Pavel Machek <pavel@suse.cz>
 *
 * The additional parts are: 
 * 
 * Copyright (C) 2003 Patrick Mochel
 * Copyright (C) 2003 Open Source Development Lab
 * 
 * This file is released under the GPLv2. 
 *
 * For more information, please see the text files in Documentation/power/
 *
 */

#undef DEBUG

#include <linux/mm.h>
#include <linux/bio.h>
#include <linux/suspend.h>
#include <linux/version.h>
#include <linux/reboot.h>
#include <linux/device.h>
#include <linux/swapops.h>
#include <linux/bootmem.h>
#include <linux/utsname.h>

#include <asm/mmu_context.h>

#include "power.h"


extern asmlinkage int pmdisk_arch_suspend(int resume);

#define __ADDRESS(x)  ((unsigned long) phys_to_virt(x))
#define ADDRESS(x) __ADDRESS((x) << PAGE_SHIFT)
#define ADDRESS2(x) __ADDRESS(__pa(x))          /* Needed for x86-64 where some pages are in memory twice */

/* References to section boundaries */
extern char __nosave_begin, __nosave_end;

extern int is_head_of_free_region(struct page *);

/* Variables to be preserved over suspend */
static int pagedir_order_check;
static int nr_copy_pages_check;

/* For resume= kernel option */
static char resume_file[256] = CONFIG_PM_DISK_PARTITION;

static dev_t resume_device;
/* Local variables that should not be affected by save */
unsigned int pmdisk_pages __nosavedata = 0;

/* Suspend pagedir is allocated before final copy, therefore it
   must be freed after resume 

   Warning: this is evil. There are actually two pagedirs at time of
   resume. One is "pagedir_save", which is empty frame allocated at
   time of suspend, that must be freed. Second is "pagedir_nosave", 
   allocated at time of resume, that travels through memory not to
   collide with anything.
 */
suspend_pagedir_t *pm_pagedir_nosave __nosavedata = NULL;
static suspend_pagedir_t *pagedir_save;
static int pagedir_order __nosavedata = 0;


struct pmdisk_info {
        struct new_utsname      uts;
        u32                     version_code;
        unsigned long           num_physpages;
        int                     cpus;
        unsigned long           image_pages;
        unsigned long           pagedir_pages;
        swp_entry_t             pagedir[768];
} __attribute__((aligned(PAGE_SIZE))) pmdisk_info;



#define PMDISK_SIG      "pmdisk-swap1"

struct pmdisk_header {
        char reserved[PAGE_SIZE - 20 - sizeof(swp_entry_t)];
        swp_entry_t pmdisk_info;
        char    orig_sig[10];
        char    sig[10];
} __attribute__((packed, aligned(PAGE_SIZE))) pmdisk_header;

/*
 * XXX: We try to keep some more pages free so that I/O operations succeed
 * without paging. Might this be more?
 */
#define PAGES_FOR_IO    512


/*
 * Saving part...
 */


/* We memorize in swapfile_used what swap devices are used for suspension */
#define SWAPFILE_UNUSED    0
#define SWAPFILE_SUSPEND   1    /* This is the suspending device */
#define SWAPFILE_IGNORED   2    /* Those are other swap devices ignored for suspension */

static unsigned short swapfile_used[MAX_SWAPFILES];
static unsigned short root_swap;


static int mark_swapfiles(swp_entry_t prev)
{
        int error;

        rw_swap_page_sync(READ, 
                          swp_entry(root_swap, 0),
                          virt_to_page((unsigned long)&pmdisk_header));
        if (!memcmp("SWAP-SPACE",pmdisk_header.sig,10) ||
            !memcmp("SWAPSPACE2",pmdisk_header.sig,10)) {
                memcpy(pmdisk_header.orig_sig,pmdisk_header.sig,10);
                memcpy(pmdisk_header.sig,PMDISK_SIG,10);
                pmdisk_header.pmdisk_info = prev;
                error = rw_swap_page_sync(WRITE, 
                                          swp_entry(root_swap, 0),
                                          virt_to_page((unsigned long)
                                                       &pmdisk_header));
        } else {
                pr_debug("pmdisk: Partition is not swap space.\n");
                error = -ENODEV;
        }
        return error;
}

static int read_swapfiles(void) /* This is called before saving image */
{
        int i, len;
        
        len=strlen(resume_file);
        root_swap = 0xFFFF;
        
        swap_list_lock();
        for(i=0; i<MAX_SWAPFILES; i++) {
                if (swap_info[i].flags == 0) {
                        swapfile_used[i]=SWAPFILE_UNUSED;
                } else {
                        if(!len) {
                                pr_debug("pmdisk: Default resume partition not set.\n");
                                if(root_swap == 0xFFFF) {
                                        swapfile_used[i] = SWAPFILE_SUSPEND;
                                        root_swap = i;
                                } else
                                        swapfile_used[i] = SWAPFILE_IGNORED;                              
                        } else {
                                /* we ignore all swap devices that are not the resume_file */
                                if (1) {
// FIXME                                if(resume_device == swap_info[i].swap_device) {
                                        swapfile_used[i] = SWAPFILE_SUSPEND;
                                        root_swap = i;
                                } else
                                        swapfile_used[i] = SWAPFILE_IGNORED;
                        }
                }
        }
        swap_list_unlock();
        return (root_swap != 0xffff) ? 0 : -ENODEV;
}


/* This is called after saving image so modification
   will be lost after resume... and that's what we want. */
static void lock_swapdevices(void)
{
        int i;

        swap_list_lock();
        for(i = 0; i< MAX_SWAPFILES; i++)
                if(swapfile_used[i] == SWAPFILE_IGNORED) {
                        swap_info[i].flags ^= 0xFF; /* we make the device unusable. A new call to
                                                       lock_swapdevices can unlock the devices. */
                }
        swap_list_unlock();
}



/**
 *      write_swap_page - Write one page to a fresh swap location.
 *      @addr:  Address we're writing.
 *      @loc:   Place to store the entry we used.
 *
 *      Allocate a new swap entry and 'sync' it. Note we discard -EIO
 *      errors. That is an artifact left over from swsusp. It did not 
 *      check the return of rw_swap_page_sync() at all, since most pages
 *      written back to swap would return -EIO.
 *      This is a partial improvement, since we will at least return other
 *      errors, though we need to eventually fix the damn code.
 */

static int write_swap_page(unsigned long addr, swp_entry_t * loc)
{
        swp_entry_t entry;
        int error = 0;

        entry = get_swap_page();
        if (swp_offset(entry) && 
            swapfile_used[swp_type(entry)] == SWAPFILE_SUSPEND) {
                error = rw_swap_page_sync(WRITE, entry,
                                          virt_to_page(addr));
                if (error == -EIO)
                        error = 0;
                if (!error)
                        *loc = entry;
        } else
                error = -ENOSPC;
        return error;
}


/**
 *      free_data - Free the swap entries used by the saved image.
 *
 *      Walk the list of used swap entries and free each one. 
 */

static void free_data(void)
{
        swp_entry_t entry;
        int i;

        for (i = 0; i < pmdisk_pages; i++) {
                entry = (pm_pagedir_nosave + i)->swap_address;
                if (entry.val)
                        swap_free(entry);
                else
                        break;
                (pm_pagedir_nosave + i)->swap_address = (swp_entry_t){0};
        }
}


/**
 *      write_data - Write saved image to swap.
 *
 *      Walk the list of pages in the image and sync each one to swap.
 */

static int write_data(void)
{
        int error = 0;
        int i;

        printk( "Writing data to swap (%d pages): ", pmdisk_pages );
        for (i = 0; i < pmdisk_pages && !error; i++) {
                if (!(i%100))
                        printk( "." );
                error = write_swap_page((pm_pagedir_nosave+i)->address,
                                        &((pm_pagedir_nosave+i)->swap_address));
        }
        printk(" %d Pages done.\n",i);
        return error;
}


/**
 *      free_pagedir - Free pages used by the page directory.
 */

static void free_pagedir_entries(void)
{
        int num = pmdisk_info.pagedir_pages;
        int i;

        for (i = 0; i < num; i++)
                swap_free(pmdisk_info.pagedir[i]);
}


/**
 *      write_pagedir - Write the array of pages holding the page directory.
 *      @last:  Last swap entry we write (needed for header).
 */

static int write_pagedir(void)
{
        unsigned long addr = (unsigned long)pm_pagedir_nosave;
        int error = 0;
        int n = SUSPEND_PD_PAGES(pmdisk_pages);
        int i;

        pmdisk_info.pagedir_pages = n;
        printk( "Writing pagedir (%d pages)\n", n);
        for (i = 0; i < n && !error; i++, addr += PAGE_SIZE)
                error = write_swap_page(addr,&pmdisk_info.pagedir[i]);
        return error;
}


#ifdef DEBUG
static void dump_pmdisk_info(void)
{
        printk(" pmdisk: Version: %u\n",pmdisk_info.version_code);
        printk(" pmdisk: Num Pages: %ld\n",pmdisk_info.num_physpages);
        printk(" pmdisk: UTS Sys: %s\n",pmdisk_info.uts.sysname);
        printk(" pmdisk: UTS Node: %s\n",pmdisk_info.uts.nodename);
        printk(" pmdisk: UTS Release: %s\n",pmdisk_info.uts.release);
        printk(" pmdisk: UTS Version: %s\n",pmdisk_info.uts.version);
        printk(" pmdisk: UTS Machine: %s\n",pmdisk_info.uts.machine);
        printk(" pmdisk: UTS Domain: %s\n",pmdisk_info.uts.domainname);
        printk(" pmdisk: CPUs: %d\n",pmdisk_info.cpus);
        printk(" pmdisk: Image: %ld Pages\n",pmdisk_info.image_pages);
        printk(" pmdisk: Pagedir: %ld Pages\n",pmdisk_info.pagedir_pages);
}
#else
static void dump_pmdisk_info(void)
{

}
#endif

static void init_header(void)
{
        memset(&pmdisk_info,0,sizeof(pmdisk_info));
        pmdisk_info.version_code = LINUX_VERSION_CODE;
        pmdisk_info.num_physpages = num_physpages;
        memcpy(&pmdisk_info.uts,&system_utsname,sizeof(system_utsname));

        pmdisk_info.cpus = num_online_cpus();
        pmdisk_info.image_pages = pmdisk_pages;
}

/**
 *      write_header - Fill and write the suspend header.
 *      @entry: Location of the last swap entry used.
 *
 *      Allocate a page, fill header, write header. 
 *
 *      @entry is the location of the last pagedir entry written on 
 *      entrance. On exit, it contains the location of the header. 
 */

static int write_header(swp_entry_t * entry)
{
        dump_pmdisk_info();
        return write_swap_page((unsigned long)&pmdisk_info,entry);
}



/**
 *      write_suspend_image - Write entire image and metadata.
 *
 */

static int write_suspend_image(void)
{
        int error;
        swp_entry_t prev = { 0 };

        init_header();

        if ((error = write_data()))
                goto FreeData;

        if ((error = write_pagedir()))
                goto FreePagedir;

        if ((error = write_header(&prev)))
                goto FreePagedir;

        error = mark_swapfiles(prev);
 Done:
        return error;
 FreePagedir:
        free_pagedir_entries();
 FreeData:
        free_data();
        goto Done;
}



/**
 *      saveable - Determine whether a page should be cloned or not.
 *      @pfn:   The page
 *
 *      We save a page if it's Reserved, and not in the range of pages
 *      statically defined as 'unsaveable', or if it isn't reserved, and
 *      isn't part of a free chunk of pages.
 *      If it is part of a free chunk, we update @pfn to point to the last 
 *      page of the chunk.
 */

static int saveable(unsigned long * pfn)
{
        struct page * page = pfn_to_page(*pfn);

        if (PageNosave(page))
                return 0;

        if (!PageReserved(page)) {
                int chunk_size;

                if ((chunk_size = is_head_of_free_region(page))) {
                        *pfn += chunk_size - 1;
                        return 0;
                }
        } else if (PageReserved(page)) {
                /* Just copy whole code segment. 
                 * Hopefully it is not that big.
                 */
                if ((ADDRESS(*pfn) >= (unsigned long) ADDRESS2(&__nosave_begin)) && 
                    (ADDRESS(*pfn) <  (unsigned long) ADDRESS2(&__nosave_end))) {
                        pr_debug("[nosave %lx]\n", ADDRESS(*pfn));
                        return 0;
                }
                /* Hmm, perhaps copying all reserved pages is not 
                 * too healthy as they may contain 
                 * critical bios data? 
                 */
        }
        return 1;
}



/**
 *      count_pages - Determine size of page directory.
 *      
 *      Iterate over all the pages in the system and tally the number
 *      we need to clone.
 */

static void count_pages(void)
{
        unsigned long pfn;
        int n = 0;
        
        for (pfn = 0; pfn < max_pfn; pfn++) {
                if (saveable(&pfn))
                        n++;
        }
        pmdisk_pages = n;
}


/**
 *      copy_pages - Atomically snapshot memory.
 *
 *      Iterate over all the pages in the system and copy each one 
 *      into its corresponding location in the pagedir.
 *      We rely on the fact that the number of pages that we're snap-
 *      shotting hasn't changed since we counted them. 
 */

static void copy_pages(void)
{
        struct pbe * p = pagedir_save;
        unsigned long pfn;
        int n = 0;

        for (pfn = 0; pfn < max_pfn; pfn++) {
                if (saveable(&pfn)) {
                        n++;
                        p->orig_address = ADDRESS(pfn);
                        copy_page((void *) p->address, 
                                  (void *) p->orig_address);
                        p++;
                }
        }
        BUG_ON(n != pmdisk_pages);
}


/**
 *      free_image_pages - Free each page allocated for snapshot.
 */

static void free_image_pages(void)
{
        struct pbe * p;
        int i;

        for (i = 0, p = pagedir_save; i < pmdisk_pages; i++, p++) {
                ClearPageNosave(virt_to_page(p->address));
                free_page(p->address);
        }
}


/**
 *      free_pagedir - Free the page directory.
 */

static void free_pagedir(void)
{
        free_image_pages();
        free_pages((unsigned long)pagedir_save, pagedir_order);
}


static void calc_order(void)
{
        int diff;
        int order;

        order = get_bitmask_order(SUSPEND_PD_PAGES(pmdisk_pages));
        pmdisk_pages += 1 << order;
        do {
                diff = get_bitmask_order(SUSPEND_PD_PAGES(pmdisk_pages)) - order;
                if (diff) {
                        order += diff;
                        pmdisk_pages += 1 << diff;
                }
        } while(diff);
        pagedir_order = order;
}


/**
 *      alloc_pagedir - Allocate the page directory.
 *
 *      First, determine exactly how many contiguous pages we need, 
 *      allocate them, then mark each 'unsavable'.
 */

static int alloc_pagedir(void)
{
        calc_order();
        pagedir_save = (suspend_pagedir_t *)__get_free_pages(GFP_ATOMIC | __GFP_COLD, 
                                                             pagedir_order);
        if(!pagedir_save)
                return -ENOMEM;
        memset(pagedir_save,0,(1 << pagedir_order) * PAGE_SIZE);
        pm_pagedir_nosave = pagedir_save;
        return 0;
}


/**
 *      alloc_image_pages - Allocate pages for the snapshot.
 *
 */

static int alloc_image_pages(void)
{
        struct pbe * p;
        int i;

        for (i = 0, p = pagedir_save; i < pmdisk_pages; i++, p++) {
                p->address = get_zeroed_page(GFP_ATOMIC | __GFP_COLD);
                if(!p->address)
                        goto Error;
                SetPageNosave(virt_to_page(p->address));
        }
        return 0;
 Error:
        do { 
                if (p->address)
                        free_page(p->address);
                p->address = 0;
        } while (p-- > pagedir_save);
        return -ENOMEM;
}


/**
 *      enough_free_mem - Make sure we enough free memory to snapshot.
 *
 *      Returns TRUE or FALSE after checking the number of available 
 *      free pages.
 */

static int enough_free_mem(void)
{
        if(nr_free_pages() < (pmdisk_pages + PAGES_FOR_IO)) {
                pr_debug("pmdisk: Not enough free pages: Have %d\n",
                         nr_free_pages());
                return 0;
        }
        return 1;
}


/**
 *      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.
 *
 *      FIXME: si_swapinfo(&i) returns all swap devices information.
 *      We should only consider resume_device. 
 */

static int enough_swap(void)
{
        struct sysinfo i;

        si_swapinfo(&i);
        if (i.freeswap < (pmdisk_pages + PAGES_FOR_IO))  {
                pr_debug("pmdisk: Not enough swap. Need %ld\n",i.freeswap);
                return 0;
        }
        return 1;
}


/**
 *      pmdisk_suspend - Atomically snapshot the system.
 *
 *      This must be called with interrupts disabled, to prevent the 
 *      system changing at all from underneath us. 
 *
 *      To do this, we count the number of pages in the system that we 
 *      need to save; make sure we have enough memory and swap to clone
 *      the pages and save them in swap, allocate the space to hold them,
 *      and then snapshot them all.
 */

int pmdisk_suspend(void)
{
        int error = 0;

        if ((error = read_swapfiles()))
                return error;

        drain_local_pages();

        pm_pagedir_nosave = NULL;
        pr_debug("pmdisk: Counting pages to copy.\n" );
        count_pages();
        
        pr_debug("pmdisk: (pages needed: %d + %d free: %d)\n",
                 pmdisk_pages,PAGES_FOR_IO,nr_free_pages());

        if (!enough_free_mem())
                return -ENOMEM;

        if (!enough_swap())
                return -ENOSPC;

        if ((error = alloc_pagedir())) {
                pr_debug("pmdisk: Allocating pagedir failed.\n");
                return error;
        }
        if ((error = alloc_image_pages())) {
                pr_debug("pmdisk: Allocating image pages failed.\n");
                free_pagedir();
                return error;
        }

        nr_copy_pages_check = pmdisk_pages;
        pagedir_order_check = pagedir_order;

        /* During allocating of suspend pagedir, new cold pages may appear. 
         * Kill them 
         */
        drain_local_pages();

        /* copy */
        copy_pages();

        /*
         * End of critical section. From now on, we can write to memory,
         * but we should not touch disk. This specially means we must _not_
         * touch swap space! Except we must write out our image of course.
         */

        pr_debug("pmdisk: %d pages copied\n", pmdisk_pages );
        return 0;
}


/**
 *      suspend_save_image - Prepare and write saved image to swap.
 *
 *      IRQs are re-enabled here so we can resume devices and safely write
 *      to the swap devices. We disable them again before we leave.
 *
 *      The second lock_swapdevices() will unlock ignored swap devices since
 *      writing is finished.
 *      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.)
 */

static int suspend_save_image(void)
{
        int error;
        device_resume();
        lock_swapdevices();
        error = write_suspend_image();
        lock_swapdevices();
        return error;
}

/*
 * Magic happens here
 */

int pmdisk_resume(void)
{
        BUG_ON (nr_copy_pages_check != pmdisk_pages);
        BUG_ON (pagedir_order_check != pagedir_order);
        
        /* Even mappings of "global" things (vmalloc) need to be fixed */
        __flush_tlb_global();
        return 0;
}

/* pmdisk_arch_suspend() is implemented in arch/?/power/pmdisk.S,
   and basically does:

        if (!resume) {
                save_processor_state();
                SAVE_REGISTERS
                return pmdisk_suspend();
        }
        GO_TO_SWAPPER_PAGE_TABLES
        COPY_PAGES_BACK
        RESTORE_REGISTERS
        restore_processor_state();
        return pmdisk_resume();

 */


/* More restore stuff */

#define does_collide(addr) does_collide_order(pm_pagedir_nosave, addr, 0)

/*
 * Returns true if given address/order collides with any orig_address 
 */
static int __init does_collide_order(suspend_pagedir_t *pagedir, 
                                     unsigned long addr, int order)
{
        int i;
        unsigned long addre = addr + (PAGE_SIZE<<order);
        
        for(i=0; i < pmdisk_pages; i++)
                if((pagedir+i)->orig_address >= addr &&
                        (pagedir+i)->orig_address < addre)
                        return 1;

        return 0;
}

/*
 * We check here that pagedir & pages it points to won't collide with pages
 * where we're going to restore from the loaded pages later
 */
static int __init check_pagedir(void)
{
        int i;

        for(i=0; i < pmdisk_pages; i++) {
                unsigned long addr;

                do {
                        addr = get_zeroed_page(GFP_ATOMIC);
                        if(!addr)
                                return -ENOMEM;
                } while (does_collide(addr));

                (pm_pagedir_nosave+i)->address = addr;
        }
        return 0;
}

static int __init relocate_pagedir(void)
{
        /*
         * We have to avoid recursion (not to overflow kernel stack),
         * and that's why code looks pretty cryptic 
         */
        suspend_pagedir_t *old_pagedir = pm_pagedir_nosave;
        void **eaten_memory = NULL;
        void **c = eaten_memory, *m, *f;
        int err;

        pr_debug("pmdisk: Relocating pagedir\n");

        if(!does_collide_order(old_pagedir, (unsigned long)old_pagedir, pagedir_order)) {
                pr_debug("pmdisk: Relocation not necessary\n");
                return 0;
        }

        err = -ENOMEM;
        while ((m = (void *) __get_free_pages(GFP_ATOMIC, pagedir_order)) != NULL) {
                if (!does_collide_order(old_pagedir, (unsigned long)m,
                                        pagedir_order)) {
                        pm_pagedir_nosave =
                                memcpy(m, old_pagedir,
                                       PAGE_SIZE << pagedir_order);
                        err = 0;
                        break;
                }
                eaten_memory = m;
                printk( "." ); 
                *eaten_memory = c;
                c = eaten_memory;
        }

        c = eaten_memory;
        while(c) {
                printk(":");
                f = c;
                c = *c;
                free_pages((unsigned long)f, pagedir_order);
        }
        printk("|\n");
        return err;
}


static struct block_device * resume_bdev;


/**
 *      Using bio to read from swap.
 *      This code requires a bit more work than just using buffer heads
 *      but, it is the recommended way for 2.5/2.6.
 *      The following are to signal the beginning and end of I/O. Bios
 *      finish asynchronously, while we want them to happen synchronously.
 *      A simple atomic_t, and a wait loop take care of this problem.
 */

static atomic_t io_done = ATOMIC_INIT(0);

static void start_io(void)
{
        atomic_set(&io_done,1);
}

static int end_io(struct bio * bio, unsigned int num, int err)
{
        atomic_set(&io_done,0);
        return 0;
}

static void wait_io(void)
{
        while(atomic_read(&io_done))
                io_schedule();
}


/**
 *      submit - submit BIO request.
 *      @rw:    READ or WRITE.
 *      @off    physical offset of page.
 *      @page:  page we're reading or writing.
 *
 *      Straight from the textbook - allocate and initialize the bio.
 *      If we're writing, make sure the page is marked as dirty.
 *      Then submit it and wait.
 */

static int submit(int rw, pgoff_t page_off, void * page)
{
        int error = 0;
        struct bio * bio;

        bio = bio_alloc(GFP_ATOMIC,1);
        if (!bio)
                return -ENOMEM;
        bio->bi_sector = page_off * (PAGE_SIZE >> 9);
        bio_get(bio);
        bio->bi_bdev = resume_bdev;
        bio->bi_end_io = end_io;

        if (bio_add_page(bio, virt_to_page(page), PAGE_SIZE, 0) < PAGE_SIZE) {
                printk("pmdisk: ERROR: adding page to bio at %ld\n",page_off);
                error = -EFAULT;
                goto Done;
        }

        if (rw == WRITE)
                bio_set_pages_dirty(bio);
        start_io();
        submit_bio(rw | (1 << BIO_RW_SYNC), bio);
        wait_io();
 Done:
        bio_put(bio);
        return error;
}

static int
read_page(pgoff_t page_off, void * page)
{
        return submit(READ,page_off,page);
}

static int
write_page(pgoff_t page_off, void * page)
{
        return submit(WRITE,page_off,page);
}


extern dev_t __init name_to_dev_t(const char *line);


static int __init check_sig(void)
{
        int error;

        memset(&pmdisk_header,0,sizeof(pmdisk_header));
        if ((error = read_page(0,&pmdisk_header)))
                return error;
        if (!memcmp(PMDISK_SIG,pmdisk_header.sig,10)) {
                memcpy(pmdisk_header.sig,pmdisk_header.orig_sig,10);

                /*
                 * Reset swap signature now.
                 */
                error = write_page(0,&pmdisk_header);
        } else { 
                pr_debug(KERN_ERR "pmdisk: Invalid partition type.\n");
                return -EINVAL;
        }
        if (!error)
                pr_debug("pmdisk: Signature found, resuming\n");
        return error;
}


/*
 * Sanity check if this image makes sense with this kernel/swap context
 * I really don't think that it's foolproof but more than nothing..
 */

static const char * __init sanity_check(void)
{
        dump_pmdisk_info();
        if(pmdisk_info.version_code != LINUX_VERSION_CODE)
                return "kernel version";
        if(pmdisk_info.num_physpages != num_physpages)
                return "memory size";
        if (strcmp(pmdisk_info.uts.sysname,system_utsname.sysname))
                return "system type";
        if (strcmp(pmdisk_info.uts.release,system_utsname.release))
                return "kernel release";
        if (strcmp(pmdisk_info.uts.version,system_utsname.version))
                return "version";
        if (strcmp(pmdisk_info.uts.machine,system_utsname.machine))
                return "machine";
        if(pmdisk_info.cpus != num_online_cpus())
                return "number of cpus";
        return NULL;
}


static int __init check_header(void)
{
        const char * reason = NULL;
        int error;

        init_header();

        if ((error = read_page(swp_offset(pmdisk_header.pmdisk_info), 
                               &pmdisk_info)))
                return error;

        /* Is this same machine? */
        if ((reason = sanity_check())) {
                printk(KERN_ERR "pmdisk: Resume mismatch: %s\n",reason);
                return -EPERM;
        }
        pmdisk_pages = pmdisk_info.image_pages;
        return error;
}


static int __init read_pagedir(void)
{
        unsigned long addr;
        int i, n = pmdisk_info.pagedir_pages;
        int error = 0;

        pagedir_order = get_bitmask_order(n);

        addr =__get_free_pages(GFP_ATOMIC, pagedir_order);
        if (!addr)
                return -ENOMEM;
        pm_pagedir_nosave = (struct pbe *)addr;

        pr_debug("pmdisk: Reading pagedir (%d Pages)\n",n);

        for (i = 0; i < n && !error; i++, addr += PAGE_SIZE) {
                unsigned long offset = swp_offset(pmdisk_info.pagedir[i]);
                if (offset)
                        error = read_page(offset, (void *)addr);
                else

                        error = -EFAULT;
        }
        if (error)
                free_pages((unsigned long)pm_pagedir_nosave,pagedir_order);
        return error;
}


/**
 *      read_image_data - Read image pages from swap.
 *
 *      You do not need to check for overlaps, check_pagedir()
 *      already did that.
 */

static int __init read_image_data(void)
{
        struct pbe * p;
        int error = 0;
        int i;

        printk( "Reading image data (%d pages): ", pmdisk_pages );
        for(i = 0, p = pm_pagedir_nosave; i < pmdisk_pages && !error; i++, p++) {
                if (!(i%100))
                        printk( "." );
                error = read_page(swp_offset(p->swap_address),
                                  (void *)p->address);
        }
        printk(" %d done.\n",i);
        return error;
}


static int __init read_suspend_image(void)
{
        int error = 0;

        if ((error = check_sig()))
                return error;
        if ((error = check_header()))
                return error;
        if ((error = read_pagedir()))
                return error;
        if ((error = relocate_pagedir()))
                goto FreePagedir;
        if ((error = check_pagedir()))
                goto FreePagedir;
        if ((error = read_image_data()))
                goto FreePagedir;
 Done:
        return error;
 FreePagedir:
        free_pages((unsigned long)pm_pagedir_nosave,pagedir_order);
        goto Done;
}

/**
 *      pmdisk_save - Snapshot memory
 */

int pmdisk_save(void) 
{
        int error;

#if defined (CONFIG_HIGHMEM) || defined (CONFIG_DISCONTIGMEM)
        pr_debug("pmdisk: not supported with high- or discontig-mem.\n");
        return -EPERM;
#endif
        if ((error = arch_prepare_suspend()))
                return error;
        local_irq_disable();
        save_processor_state();
        error = pmdisk_arch_suspend(0);
        restore_processor_state();
        local_irq_enable();
        return error;
}


/**
 *      pmdisk_write - Write saved memory image to swap.
 *
 *      pmdisk_arch_suspend(0) returns after system is resumed.
 *
 *      pmdisk_arch_suspend() copies all "used" memory to "free" memory,
 *      then unsuspends all device drivers, and writes memory to disk
 *      using normal kernel mechanism.
 */

int pmdisk_write(void)
{
        return suspend_save_image();
}


/**
 *      pmdisk_read - Read saved image from swap.
 */

int __init pmdisk_read(void)
{
        int error;

        if (!strlen(resume_file))
                return -ENOENT;

        resume_device = name_to_dev_t(resume_file);
        pr_debug("pmdisk: Resume From Partition: %s\n", resume_file);

        resume_bdev = open_by_devnum(resume_device, FMODE_READ);
        if (!IS_ERR(resume_bdev)) {
                set_blocksize(resume_bdev, PAGE_SIZE);
                error = read_suspend_image();
                blkdev_put(resume_bdev);
        } else
                error = PTR_ERR(resume_bdev);

        if (!error)
                pr_debug("Reading resume file was successful\n");
        else
                pr_debug("pmdisk: Error %d resuming\n", error);
        return error;
}


/**
 *      pmdisk_restore - Replace running kernel with saved image.
 */

int __init pmdisk_restore(void)
{
        int error;
        local_irq_disable();
        save_processor_state();
        error = pmdisk_arch_suspend(1);
        restore_processor_state();
        local_irq_enable();
        return error;
}


/**
 *      pmdisk_free - Free memory allocated to hold snapshot.
 */

int pmdisk_free(void)
{
        pr_debug( "Freeing prev allocated pagedir\n" );
        free_pagedir();
        return 0;
}

static int __init pmdisk_setup(char *str)
{
        if (strlen(str)) {
                if (!strcmp(str,"off"))
                        resume_file[0] = '\0';
                else
                        strncpy(resume_file, str, 255);
        } else
                resume_file[0] = '\0';
        return 1;
}

__setup("pmdisk=", pmdisk_setup);