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32 results

swsusp.c

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  • swsusp.c 25.99 KiB
    /*
     * linux/kernel/power/swsusp.c
     *
     * This file provides code to write suspend image to swap and read it back.
     *
     * Copyright (C) 1998-2001 Gabor Kuti <seasons@fornax.hu>
     * Copyright (C) 1998,2001-2005 Pavel Machek <pavel@suse.cz>
     *
     * This file is released under the GPLv2.
     *
     * I'd like to thank the following people for their work:
     *
     * Pavel Machek <pavel@ucw.cz>:
     * Modifications, defectiveness pointing, being with me at the very beginning,
     * suspend to swap space, stop all tasks. Port to 2.4.18-ac and 2.5.17.
     *
     * Steve Doddi <dirk@loth.demon.co.uk>:
     * Support the possibility of hardware state restoring.
     *
     * Raph <grey.havens@earthling.net>:
     * Support for preserving states of network devices and virtual console
     * (including X and svgatextmode)
     *
     * Kurt Garloff <garloff@suse.de>:
     * Straightened the critical function in order to prevent compilers from
     * playing tricks with local variables.
     *
     * Andreas Mohr <a.mohr@mailto.de>
     *
     * Alex Badea <vampire@go.ro>:
     * Fixed runaway init
     *
     * Rafael J. Wysocki <rjw@sisk.pl>
     * Added the swap map data structure and reworked the handling of swap
     *
     * More state savers are welcome. Especially for the scsi layer...
     *
     * For TODOs,FIXMEs also look in Documentation/power/swsusp.txt
     */
    
    #include <linux/module.h>
    #include <linux/mm.h>
    #include <linux/suspend.h>
    #include <linux/smp_lock.h>
    #include <linux/file.h>
    #include <linux/utsname.h>
    #include <linux/version.h>
    #include <linux/delay.h>
    #include <linux/bitops.h>
    #include <linux/spinlock.h>
    #include <linux/genhd.h>
    #include <linux/kernel.h>
    #include <linux/major.h>
    #include <linux/swap.h>
    #include <linux/pm.h>
    #include <linux/device.h>
    #include <linux/buffer_head.h>
    #include <linux/swapops.h>
    #include <linux/bootmem.h>
    #include <linux/syscalls.h>
    #include <linux/highmem.h>
    #include <linux/bio.h>
    
    #include <asm/uaccess.h>
    #include <asm/mmu_context.h>
    #include <asm/pgtable.h>
    #include <asm/tlbflush.h>
    #include <asm/io.h>
    
    #include "power.h"
    
    /*
     * Preferred image size in bytes (tunable via /sys/power/image_size).
     * When it is set to N, swsusp will do its best to ensure the image
     * size will not exceed N bytes, but if that is impossible, it will
     * try to create the smallest image possible.
     */
    unsigned long image_size = 500 * 1024 * 1024;
    
    #ifdef CONFIG_HIGHMEM
    unsigned int count_highmem_pages(void);
    int save_highmem(void);
    int restore_highmem(void);
    #else
    static int save_highmem(void) { return 0; }
    static int restore_highmem(void) { return 0; }
    static unsigned int count_highmem_pages(void) { return 0; }
    #endif
    
    extern char resume_file[];
    
    #define SWSUSP_SIG	"S1SUSPEND"
    
    static struct swsusp_header {
    	char reserved[PAGE_SIZE - 20 - sizeof(swp_entry_t)];
    	swp_entry_t image;
    	char	orig_sig[10];
    	char	sig[10];
    } __attribute__((packed, aligned(PAGE_SIZE))) swsusp_header;
    
    static struct swsusp_info swsusp_info;
    
    /*
     * Saving part...
     */
    
    static unsigned short root_swap = 0xffff;
    
    static int mark_swapfiles(swp_entry_t start)
    {
    	int error;
    
    	rw_swap_page_sync(READ,
    			  swp_entry(root_swap, 0),
    			  virt_to_page((unsigned long)&swsusp_header));
    	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;
    		error = rw_swap_page_sync(WRITE,
    					  swp_entry(root_swap, 0),
    					  virt_to_page((unsigned long)
    						       &swsusp_header));
    	} else {
    		pr_debug("swsusp: Partition is not swap space.\n");
    		error = -ENODEV;
    	}
    	return error;
    }
    
    /*
     * Check whether the swap device is the specified resume
     * device, irrespective of whether they are specified by
     * identical names.
     *
     * (Thus, device inode aliasing is allowed.  You can say /dev/hda4
     * instead of /dev/ide/host0/bus0/target0/lun0/part4 [if using devfs]
     * and they'll be considered the same device.  This is *necessary* for
     * devfs, since the resume code can only recognize the form /dev/hda4,
     * but the suspend code would see the long name.)
     */
    static inline int is_resume_device(const struct swap_info_struct *swap_info)
    {
    	struct file *file = swap_info->swap_file;
    	struct inode *inode = file->f_dentry->d_inode;
    
    	return S_ISBLK(inode->i_mode) &&
    		swsusp_resume_device == MKDEV(imajor(inode), iminor(inode));
    }
    
    static int swsusp_swap_check(void) /* This is called before saving image */
    {
    	int i;
    
    	spin_lock(&swap_lock);
    	for (i = 0; i < MAX_SWAPFILES; i++) {
    		if (!(swap_info[i].flags & SWP_WRITEOK))
    			continue;
    		if (!swsusp_resume_device || is_resume_device(swap_info + i)) {
    			spin_unlock(&swap_lock);
    			root_swap = i;
    			return 0;
    		}
    	}
    	spin_unlock(&swap_lock);
    	return -ENODEV;
    }
    
    /**
     *	write_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_page(unsigned long addr, swp_entry_t *loc)
    {
    	swp_entry_t entry;
    	int error = -ENOSPC;
    
    	entry = get_swap_page_of_type(root_swap);
    	if (swp_offset(entry)) {
    		error = rw_swap_page_sync(WRITE, entry, virt_to_page(addr));
    		if (!error || error == -EIO)
    			*loc = entry;
    	}
    	return error;
    }
    
    /**
     *	Swap map-handling functions
     *
     *	The swap map is a data structure used for keeping track of each page
     *	written to the swap.  It consists of many swap_map_page structures
     *	that contain each an array of MAP_PAGE_SIZE swap entries.
     *	These structures are linked together with the help of either the
     *	.next (in memory) or the .next_swap (in swap) member.
     *
     *	The swap map is created during suspend.  At that time we need to keep
     *	it in memory, because we have to free all of the allocated swap
     *	entries if an error occurs.  The memory needed is preallocated
     *	so that we know in advance if there's enough of it.
     *
     *	The first swap_map_page structure is filled with the swap entries that
     *	correspond to the first MAP_PAGE_SIZE data pages written to swap and
     *	so on.  After the all of the data pages have been written, the order
     *	of the swap_map_page structures in the map is reversed so that they
     *	can be read from swap in the original order.  This causes the data
     *	pages to be loaded in exactly the same order in which they have been
     *	saved.
     *
     *	During resume we only need to use one swap_map_page structure
     *	at a time, which means that we only need to use two memory pages for
     *	reading the image - one for reading the swap_map_page structures
     *	and the second for reading the data pages from swap.
     */
    
    #define MAP_PAGE_SIZE	((PAGE_SIZE - sizeof(swp_entry_t) - sizeof(void *)) \
    			/ sizeof(swp_entry_t))
    
    struct swap_map_page {
    	swp_entry_t		entries[MAP_PAGE_SIZE];
    	swp_entry_t		next_swap;
    	struct swap_map_page	*next;
    };
    
    static inline void free_swap_map(struct swap_map_page *swap_map)
    {
    	struct swap_map_page *swp;
    
    	while (swap_map) {
    		swp = swap_map->next;
    		free_page((unsigned long)swap_map);
    		swap_map = swp;
    	}
    }
    
    static struct swap_map_page *alloc_swap_map(unsigned int nr_pages)
    {
    	struct swap_map_page *swap_map, *swp;
    	unsigned n = 0;
    
    	if (!nr_pages)
    		return NULL;
    
    	pr_debug("alloc_swap_map(): nr_pages = %d\n", nr_pages);
    	swap_map = (struct swap_map_page *)get_zeroed_page(GFP_ATOMIC);
    	swp = swap_map;
    	for (n = MAP_PAGE_SIZE; n < nr_pages; n += MAP_PAGE_SIZE) {
    		swp->next = (struct swap_map_page *)get_zeroed_page(GFP_ATOMIC);
    		swp = swp->next;
    		if (!swp) {
    			free_swap_map(swap_map);
    			return NULL;
    		}
    	}
    	return swap_map;
    }
    
    /**
     *	reverse_swap_map - reverse the order of pages in the swap map
     *	@swap_map
     */
    
    static inline struct swap_map_page *reverse_swap_map(struct swap_map_page *swap_map)
    {
    	struct swap_map_page *prev, *next;
    
    	prev = NULL;
    	while (swap_map) {
    		next = swap_map->next;
    		swap_map->next = prev;
    		prev = swap_map;
    		swap_map = next;
    	}
    	return prev;
    }
    
    /**
     *	free_swap_map_entries - free the swap entries allocated to store
     *	the swap map @swap_map (this is only called in case of an error)
     */
    static inline void free_swap_map_entries(struct swap_map_page *swap_map)
    {
    	while (swap_map) {
    		if (swap_map->next_swap.val)
    			swap_free(swap_map->next_swap);
    		swap_map = swap_map->next;
    	}
    }
    
    /**
     *	save_swap_map - save the swap map used for tracing the data pages
     *	stored in the swap
     */
    
    static int save_swap_map(struct swap_map_page *swap_map, swp_entry_t *start)
    {
    	swp_entry_t entry = (swp_entry_t){0};
    	int error;
    
    	while (swap_map) {
    		swap_map->next_swap = entry;
    		if ((error = write_page((unsigned long)swap_map, &entry)))
    			return error;
    		swap_map = swap_map->next;
    	}
    	*start = entry;
    	return 0;
    }
    
    /**
     *	free_image_entries - free the swap entries allocated to store
     *	the image data pages (this is only called in case of an error)
     */
    
    static inline void free_image_entries(struct swap_map_page *swp)
    {
    	unsigned k;
    
    	while (swp) {
    		for (k = 0; k < MAP_PAGE_SIZE; k++)
    			if (swp->entries[k].val)
    				swap_free(swp->entries[k]);
    		swp = swp->next;
    	}
    }
    
    /**
     *	The swap_map_handle structure is used for handling the swap map in
     *	a file-alike way
     */
    
    struct swap_map_handle {
    	struct swap_map_page *cur;
    	unsigned int k;
    };
    
    static inline void init_swap_map_handle(struct swap_map_handle *handle,
                                            struct swap_map_page *map)
    {
    	handle->cur = map;
    	handle->k = 0;
    }
    
    static inline int swap_map_write_page(struct swap_map_handle *handle,
                                          unsigned long addr)
    {
    	int error;
    
    	error = write_page(addr, handle->cur->entries + handle->k);
    	if (error)
    		return error;
    	if (++handle->k >= MAP_PAGE_SIZE) {
    		handle->cur = handle->cur->next;
    		handle->k = 0;
    	}
    	return 0;
    }
    
    /**
     *	save_image_data - save the data pages pointed to by the PBEs
     *	from the list @pblist using the swap map handle @handle
     *	(assume there are @nr_pages data pages to save)
     */
    
    static int save_image_data(struct pbe *pblist,
                               struct swap_map_handle *handle,
                               unsigned int nr_pages)
    {
    	unsigned int m;
    	struct pbe *p;
    	int error = 0;
    
    	printk("Saving image data pages (%u pages) ...     ", nr_pages);
    	m = nr_pages / 100;
    	if (!m)
    		m = 1;
    	nr_pages = 0;
    	for_each_pbe (p, pblist) {
    		error = swap_map_write_page(handle, p->address);
    		if (error)
    			break;
    		if (!(nr_pages % m))
    			printk("\b\b\b\b%3d%%", nr_pages / m);
    		nr_pages++;
    	}
    	if (!error)
    		printk("\b\b\b\bdone\n");
    	return error;
    }
    
    static void dump_info(void)
    {
    	pr_debug(" swsusp: Version: %u\n",swsusp_info.version_code);
    	pr_debug(" swsusp: Num Pages: %ld\n",swsusp_info.num_physpages);
    	pr_debug(" swsusp: UTS Sys: %s\n",swsusp_info.uts.sysname);
    	pr_debug(" swsusp: UTS Node: %s\n",swsusp_info.uts.nodename);
    	pr_debug(" swsusp: UTS Release: %s\n",swsusp_info.uts.release);
    	pr_debug(" swsusp: UTS Version: %s\n",swsusp_info.uts.version);
    	pr_debug(" swsusp: UTS Machine: %s\n",swsusp_info.uts.machine);
    	pr_debug(" swsusp: UTS Domain: %s\n",swsusp_info.uts.domainname);
    	pr_debug(" swsusp: CPUs: %d\n",swsusp_info.cpus);
    	pr_debug(" swsusp: Image: %ld Pages\n",swsusp_info.image_pages);
    	pr_debug(" swsusp: Total: %ld Pages\n", swsusp_info.pages);
    }
    
    static void init_header(unsigned int nr_pages)
    {
    	memset(&swsusp_info, 0, sizeof(swsusp_info));
    	swsusp_info.version_code = LINUX_VERSION_CODE;
    	swsusp_info.num_physpages = num_physpages;
    	memcpy(&swsusp_info.uts, &system_utsname, sizeof(system_utsname));
    
    	swsusp_info.cpus = num_online_cpus();
    	swsusp_info.image_pages = nr_pages;
    	swsusp_info.pages = nr_pages +
    		((nr_pages * sizeof(long) + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
    }
    
    /**
     *	pack_orig_addresses - the .orig_address fields of the PBEs from the
     *	list starting at @pbe are stored in the array @buf[] (1 page)
     */
    
    static inline struct pbe *pack_orig_addresses(unsigned long *buf,
                                                  struct pbe *pbe)
    {
    	int j;
    
    	for (j = 0; j < PAGE_SIZE / sizeof(long) && pbe; j++) {
    		buf[j] = pbe->orig_address;
    		pbe = pbe->next;
    	}
    	if (!pbe)
    		for (; j < PAGE_SIZE / sizeof(long); j++)
    			buf[j] = 0;
    	return pbe;
    }
    
    /**
     *	save_image_metadata - save the .orig_address fields of the PBEs
     *	from the list @pblist using the swap map handle @handle
     */
    
    static int save_image_metadata(struct pbe *pblist,
                                   struct swap_map_handle *handle)
    {
    	unsigned long *buf;
    	unsigned int n = 0;
    	struct pbe *p;
    	int error = 0;
    
    	printk("Saving image metadata ... ");
    	buf = (unsigned long *)get_zeroed_page(GFP_ATOMIC);
    	if (!buf)
    		return -ENOMEM;
    	p = pblist;
    	while (p) {
    		p = pack_orig_addresses(buf, p);
    		error = swap_map_write_page(handle, (unsigned long)buf);
    		if (error)
    			break;
    		n++;
    	}
    	free_page((unsigned long)buf);
    	if (!error)
    		printk("done (%u pages saved)\n", n);
    	return error;
    }
    
    /**
     *	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 = swap_info[root_swap].pages -
    		swap_info[root_swap].inuse_pages;
    
    	pr_debug("swsusp: free swap pages: %u\n", free_swap);
    	return free_swap > (nr_pages + PAGES_FOR_IO +
    		(nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE);
    }
    
    /**
     *	swsusp_write - Write entire image and metadata.
     *
     *	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(struct pbe *pblist, unsigned int nr_pages)
    {
    	struct swap_map_page *swap_map;
    	struct swap_map_handle handle;
    	swp_entry_t start;
    	int error;
    
    	if ((error = swsusp_swap_check())) {
    		printk(KERN_ERR "swsusp: Cannot find swap device, try swapon -a.\n");
    		return error;
    	}
    	if (!enough_swap(nr_pages)) {
    		printk(KERN_ERR "swsusp: Not enough free swap\n");
    		return -ENOSPC;
    	}
    
    	init_header(nr_pages);
    	swap_map = alloc_swap_map(swsusp_info.pages);
    	if (!swap_map)
    		return -ENOMEM;
    	init_swap_map_handle(&handle, swap_map);
    
    	error = swap_map_write_page(&handle, (unsigned long)&swsusp_info);
    	if (!error)
    		error = save_image_metadata(pblist, &handle);
    	if (!error)
    		error = save_image_data(pblist, &handle, nr_pages);
    	if (error)
    		goto Free_image_entries;
    
    	swap_map = reverse_swap_map(swap_map);
    	error = save_swap_map(swap_map, &start);
    	if (error)
    		goto Free_map_entries;
    
    	dump_info();
    	printk( "S" );
    	error = mark_swapfiles(start);
    	printk( "|\n" );
    	if (error)
    		goto Free_map_entries;
    
    Free_swap_map:
    	free_swap_map(swap_map);
    	return error;
    
    Free_map_entries:
    	free_swap_map_entries(swap_map);
    Free_image_entries:
    	free_image_entries(swap_map);
    	goto Free_swap_map;
    }
    
    /**
     *	swsusp_shrink_memory -  Try to free as much memory as needed
     *
     *	... but do not OOM-kill anyone
     *
     *	Notice: all userland should be stopped before it is called, or
     *	livelock is possible.
     */
    
    #define SHRINK_BITE	10000
    
    int swsusp_shrink_memory(void)
    {
    	long size, tmp;
    	struct zone *zone;
    	unsigned long pages = 0;
    	unsigned int i = 0;
    	char *p = "-\\|/";
    
    	printk("Shrinking memory...  ");
    	do {
    		size = 2 * count_highmem_pages();
    		size += size / 50 + count_data_pages();
    		size += (size + PBES_PER_PAGE - 1) / PBES_PER_PAGE +
    			PAGES_FOR_IO;
    		tmp = size;
    		for_each_zone (zone)
    			if (!is_highmem(zone))
    				tmp -= zone->free_pages;
    		if (tmp > 0) {
    			tmp = shrink_all_memory(SHRINK_BITE);
    			if (!tmp)
    				return -ENOMEM;
    			pages += tmp;
    		} else if (size > image_size / PAGE_SIZE) {
    			tmp = shrink_all_memory(SHRINK_BITE);
    			pages += tmp;
    		}
    		printk("\b%c", p[i++%4]);
    	} while (tmp > 0);
    	printk("\bdone (%lu pages freed)\n", pages);
    
    	return 0;
    }
    
    int swsusp_suspend(void)
    {
    	int error;
    
    	if ((error = arch_prepare_suspend()))
    		return error;
    	local_irq_disable();
    	/* At this point, device_suspend() has been called, but *not*
    	 * device_power_down(). We *must* device_power_down() now.
    	 * Otherwise, drivers for some devices (e.g. interrupt controllers)
    	 * become desynchronized with the actual state of the hardware
    	 * at resume time, and evil weirdness ensues.
    	 */
    	if ((error = device_power_down(PMSG_FREEZE))) {
    		printk(KERN_ERR "Some devices failed to power down, aborting suspend\n");
    		goto Enable_irqs;
    	}
    
    	if ((error = save_highmem())) {
    		printk(KERN_ERR "swsusp: Not enough free pages for highmem\n");
    		goto Restore_highmem;
    	}
    
    	save_processor_state();
    	if ((error = swsusp_arch_suspend()))
    		printk(KERN_ERR "Error %d suspending\n", error);
    	/* Restore control flow magically appears here */
    	restore_processor_state();
    Restore_highmem:
    	restore_highmem();
    	device_power_up();
    Enable_irqs:
    	local_irq_enable();
    	return error;
    }
    
    int swsusp_resume(void)
    {
    	int error;
    	local_irq_disable();
    	if (device_power_down(PMSG_FREEZE))
    		printk(KERN_ERR "Some devices failed to power down, very bad\n");
    	/* We'll ignore saved state, but this gets preempt count (etc) right */
    	save_processor_state();
    	error = swsusp_arch_resume();
    	/* Code below is only ever reached in case of failure. Otherwise
    	 * execution continues at place where swsusp_arch_suspend was called
             */
    	BUG_ON(!error);
    	/* The only reason why swsusp_arch_resume() can fail is memory being
    	 * very tight, so we have to free it as soon as we can to avoid
    	 * subsequent failures
    	 */
    	swsusp_free();
    	restore_processor_state();
    	restore_highmem();
    	touch_softlockup_watchdog();
    	device_power_up();
    	local_irq_enable();
    	return error;
    }
    
    /**
     *	mark_unsafe_pages - mark the pages that cannot be used for storing
     *	the image during resume, because they conflict with the pages that
     *	had been used before suspend
     */
    
    static void mark_unsafe_pages(struct pbe *pblist)
    {
    	struct zone *zone;
    	unsigned long zone_pfn;
    	struct pbe *p;
    
    	if (!pblist) /* a sanity check */
    		return;
    
    	/* Clear page flags */
    	for_each_zone (zone) {
    		for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
    			if (pfn_valid(zone_pfn + zone->zone_start_pfn))
    				ClearPageNosaveFree(pfn_to_page(zone_pfn +
    					zone->zone_start_pfn));
    	}
    
    	/* Mark orig addresses */
    	for_each_pbe (p, pblist)
    		SetPageNosaveFree(virt_to_page(p->orig_address));
    
    }
    
    static void copy_page_backup_list(struct pbe *dst, struct pbe *src)
    {
    	/* We assume both lists contain the same number of elements */
    	while (src) {
    		dst->orig_address = src->orig_address;
    		dst = dst->next;
    		src = src->next;
    	}
    }
    
    /*
     *	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 int end_io(struct bio *bio, unsigned int num, int err)
    {
    	if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
    		panic("I/O error reading memory image");
    	atomic_set(&io_done, 0);
    	return 0;
    }
    
    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.
     *
     *	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->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("swsusp: ERROR: adding page to bio at %ld\n",page_off);
    		error = -EFAULT;
    		goto Done;
    	}
    
    
    	atomic_set(&io_done, 1);
    	submit_bio(rw | (1 << BIO_RW_SYNC), bio);
    	while (atomic_read(&io_done))
    		yield();
    	if (rw == READ)
    		bio_set_pages_dirty(bio);
     Done:
    	bio_put(bio);
    	return error;
    }
    
    static int bio_read_page(pgoff_t page_off, void *page)
    {
    	return submit(READ, page_off, page);
    }
    
    static int bio_write_page(pgoff_t page_off, void *page)
    {
    	return submit(WRITE, page_off, page);
    }
    
    /**
     *	The following functions allow us to read data using a swap map
     *	in a file-alike way
     */
    
    static inline void release_swap_map_reader(struct swap_map_handle *handle)
    {
    	if (handle->cur)
    		free_page((unsigned long)handle->cur);
    	handle->cur = NULL;
    }
    
    static inline int get_swap_map_reader(struct swap_map_handle *handle,
                                          swp_entry_t start)
    {
    	int error;
    
    	if (!swp_offset(start))
    		return -EINVAL;
    	handle->cur = (struct swap_map_page *)get_zeroed_page(GFP_ATOMIC);
    	if (!handle->cur)
    		return -ENOMEM;
    	error = bio_read_page(swp_offset(start), handle->cur);
    	if (error) {
    		release_swap_map_reader(handle);
    		return error;
    	}
    	handle->k = 0;
    	return 0;
    }
    
    static inline int swap_map_read_page(struct swap_map_handle *handle, void *buf)
    {
    	unsigned long offset;
    	int error;
    
    	if (!handle->cur)
    		return -EINVAL;
    	offset = swp_offset(handle->cur->entries[handle->k]);
    	if (!offset)
    		return -EINVAL;
    	error = bio_read_page(offset, buf);
    	if (error)
    		return error;
    	if (++handle->k >= MAP_PAGE_SIZE) {
    		handle->k = 0;
    		offset = swp_offset(handle->cur->next_swap);
    		if (!offset)
    			release_swap_map_reader(handle);
    		else
    			error = bio_read_page(offset, handle->cur);
    	}
    	return error;
    }
    
    static int check_header(void)
    {
    	char *reason = NULL;
    
    	dump_info();
    	if (swsusp_info.version_code != LINUX_VERSION_CODE)
    		reason = "kernel version";
    	if (swsusp_info.num_physpages != num_physpages)
    		reason = "memory size";
    	if (strcmp(swsusp_info.uts.sysname,system_utsname.sysname))
    		reason = "system type";
    	if (strcmp(swsusp_info.uts.release,system_utsname.release))
    		reason = "kernel release";
    	if (strcmp(swsusp_info.uts.version,system_utsname.version))
    		reason = "version";
    	if (strcmp(swsusp_info.uts.machine,system_utsname.machine))
    		reason = "machine";
    	if (reason) {
    		printk(KERN_ERR "swsusp: Resume mismatch: %s\n", reason);
    		return -EPERM;
    	}
    	return 0;
    }
    
    /**
     *	load_image_data - load the image data using the swap map handle
     *	@handle and store them using the page backup list @pblist
     *	(assume there are @nr_pages pages to load)
     */
    
    static int load_image_data(struct pbe *pblist,
                               struct swap_map_handle *handle,
                               unsigned int nr_pages)
    {
    	int error;
    	unsigned int m;
    	struct pbe *p;
    
    	if (!pblist)
    		return -EINVAL;
    	printk("Loading image data pages (%u pages) ...     ", nr_pages);
    	m = nr_pages / 100;
    	if (!m)
    		m = 1;
    	nr_pages = 0;
    	p = pblist;
    	while (p) {
    		error = swap_map_read_page(handle, (void *)p->address);
    		if (error)
    			break;
    		p = p->next;
    		if (!(nr_pages % m))
    			printk("\b\b\b\b%3d%%", nr_pages / m);
    		nr_pages++;
    	}
    	if (!error)
    		printk("\b\b\b\bdone\n");
    	return error;
    }
    
    /**
     *	unpack_orig_addresses - copy the elements of @buf[] (1 page) to
     *	the PBEs in the list starting at @pbe
     */
    
    static inline struct pbe *unpack_orig_addresses(unsigned long *buf,
                                                    struct pbe *pbe)
    {
    	int j;
    
    	for (j = 0; j < PAGE_SIZE / sizeof(long) && pbe; j++) {
    		pbe->orig_address = buf[j];
    		pbe = pbe->next;
    	}
    	return pbe;
    }
    
    /**
     *	load_image_metadata - load the image metadata using the swap map
     *	handle @handle and put them into the PBEs in the list @pblist
     */
    
    static int load_image_metadata(struct pbe *pblist, struct swap_map_handle *handle)
    {
    	struct pbe *p;
    	unsigned long *buf;
    	unsigned int n = 0;
    	int error = 0;
    
    	printk("Loading image metadata ... ");
    	buf = (unsigned long *)get_zeroed_page(GFP_ATOMIC);
    	if (!buf)
    		return -ENOMEM;
    	p = pblist;
    	while (p) {
    		error = swap_map_read_page(handle, buf);
    		if (error)
    			break;
    		p = unpack_orig_addresses(buf, p);
    		n++;
    	}
    	free_page((unsigned long)buf);
    	if (!error)
    		printk("done (%u pages loaded)\n", n);
    	return error;
    }
    
    int swsusp_read(struct pbe **pblist_ptr)
    {
    	int error;
    	struct pbe *p, *pblist;
    	struct swap_map_handle handle;
    	unsigned int nr_pages;
    
    	if (IS_ERR(resume_bdev)) {
    		pr_debug("swsusp: block device not initialised\n");
    		return PTR_ERR(resume_bdev);
    	}
    
    	error = get_swap_map_reader(&handle, swsusp_header.image);
    	if (!error)
    		error = swap_map_read_page(&handle, &swsusp_info);
    	if (!error)
    		error = check_header();
    	if (error)
    		return error;
    	nr_pages = swsusp_info.image_pages;
    	p = alloc_pagedir(nr_pages, GFP_ATOMIC, 0);
    	if (!p)
    		return -ENOMEM;
    	error = load_image_metadata(p, &handle);
    	if (!error) {
    		mark_unsafe_pages(p);
    		pblist = alloc_pagedir(nr_pages, GFP_ATOMIC, 1);
    		if (pblist)
    			copy_page_backup_list(pblist, p);
    		free_pagedir(p);
    		if (!pblist)
    			error = -ENOMEM;
    
    		/* Allocate memory for the image and read the data from swap */
    		if (!error)
    			error = alloc_data_pages(pblist, GFP_ATOMIC, 1);
    		if (!error) {
    			release_eaten_pages();
    			error = load_image_data(pblist, &handle, nr_pages);
    		}
    		if (!error)
    			*pblist_ptr = pblist;
    	}
    	release_swap_map_reader(&handle);
    
    	blkdev_put(resume_bdev);
    
    	if (!error)
    		pr_debug("swsusp: Reading resume file was successful\n");
    	else
    		pr_debug("swsusp: 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, sizeof(swsusp_header));
    		if ((error = bio_read_page(0, &swsusp_header)))
    			return error;
    		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(0, &swsusp_header);
    		} else {
    			return -EINVAL;
    		}
    		if (error)
    			blkdev_put(resume_bdev);
    		else
    			pr_debug("swsusp: Signature found, resuming\n");
    	} else {
    		error = PTR_ERR(resume_bdev);
    	}
    
    	if (error)
    		pr_debug("swsusp: Error %d check for resume file\n", error);
    
    	return error;
    }
    
    /**
     *	swsusp_close - close swap device.
     */
    
    void swsusp_close(void)
    {
    	if (IS_ERR(resume_bdev)) {
    		pr_debug("swsusp: block device not initialised\n");
    		return;
    	}
    
    	blkdev_put(resume_bdev);
    }