[PATCH] swsusp: low level interface

Introduce the low level interface that can be used for handling the
snapshot of the system memory by the in-kernel swap-writing/reading code of
swsusp and the userland interface code (to be introduced shortly).

Also change the way in which swsusp records the allocated swap pages and,
consequently, simplifies the in-kernel swap-writing/reading code (this is
necessary for the userland interface too).  To this end, it introduces two
helper functions in mm/swapfile.c, so that the swsusp code does not refer
directly to the swap internals.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 256 insertions, 467 deletions

diff --git a/kernel/power/swsusp.c b/kernel/power/swsusp.c
index 4e90905f0e8..457084f5001 100644
--- a/kernel/power/swsusp.c
+++ b/kernel/power/swsusp.c
@@ -77,6 +77,8 @@
  */
 unsigned long image_size = 500 * 1024 * 1024;
 
+int in_suspend __nosavedata = 0;
+
 #ifdef CONFIG_HIGHMEM
 unsigned int count_highmem_pages(void);
 int save_highmem(void);
@@ -98,8 +100,6 @@ static struct swsusp_header {
 	char	sig[10];
 } __attribute__((packed, aligned(PAGE_SIZE))) swsusp_header;
 
-static struct swsusp_info swsusp_info;
-
 /*
  * Saving part...
  */
@@ -129,255 +129,261 @@ static int mark_swapfiles(swp_entry_t start)
 	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.)
+/**
+ *	swsusp_swap_check - check if the resume device is a swap device
+ *	and get its index (if so)
  */
-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;
-
-	if (!swsusp_resume_device)
-		return -ENODEV;
-	spin_lock(&swap_lock);
-	for (i = 0; i < MAX_SWAPFILES; i++) {
-		if (!(swap_info[i].flags & SWP_WRITEOK))
-			continue;
-		if (is_resume_device(swap_info + i)) {
-			spin_unlock(&swap_lock);
-			root_swap = i;
-			return 0;
-		}
+	int res = swap_type_of(swsusp_resume_device);
+
+	if (res >= 0) {
+		root_swap = res;
+		return 0;
 	}
-	spin_unlock(&swap_lock);
-	return -ENODEV;
+	return res;
 }
 
 /**
- *	write_page - Write one page to a fresh swap location.
- *	@addr:	Address we're writing.
- *	@loc:	Place to store the entry we used.
+ *	The bitmap is used for tracing allocated swap pages
  *
- *	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.
+ *	The entire bitmap consists of a number of bitmap_page
+ *	structures linked with the help of the .next member.
+ *	Thus each page can be allocated individually, so we only
+ *	need to make 0-order memory allocations to create
+ *	the bitmap.
  */
-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;
-}
+#define BITMAP_PAGE_SIZE	(PAGE_SIZE - sizeof(void *))
+#define BITMAP_PAGE_CHUNKS	(BITMAP_PAGE_SIZE / sizeof(long))
+#define BITS_PER_CHUNK		(sizeof(long) * 8)
+#define BITMAP_PAGE_BITS	(BITMAP_PAGE_CHUNKS * BITS_PER_CHUNK)
+
+struct bitmap_page {
+	unsigned long		chunks[BITMAP_PAGE_CHUNKS];
+	struct bitmap_page	*next;
+};
 
 /**
- *	Swap map-handling functions
+ *	The following functions are used for tracing the allocated
+ *	swap pages, so that they can be freed in case of an error.
  *
- *	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.
+ *	The functions operate on a linked bitmap structure defined
+ *	above
  */
 
-#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)
+static void free_bitmap(struct bitmap_page *bitmap)
 {
-	struct swap_map_page *swp;
+	struct bitmap_page *bp;
 
-	while (swap_map) {
-		swp = swap_map->next;
-		free_page((unsigned long)swap_map);
-		swap_map = swp;
+	while (bitmap) {
+		bp = bitmap->next;
+		free_page((unsigned long)bitmap);
+		bitmap = bp;
 	}
 }
 
-static struct swap_map_page *alloc_swap_map(unsigned int nr_pages)
+static struct bitmap_page *alloc_bitmap(unsigned int nr_bits)
 {
-	struct swap_map_page *swap_map, *swp;
-	unsigned n = 0;
+	struct bitmap_page *bitmap, *bp;
+	unsigned int n;
 
-	if (!nr_pages)
+	if (!nr_bits)
 		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);
+	bitmap = (struct bitmap_page *)get_zeroed_page(GFP_KERNEL);
+	bp = bitmap;
+	for (n = BITMAP_PAGE_BITS; n < nr_bits; n += BITMAP_PAGE_BITS) {
+		bp->next = (struct bitmap_page *)get_zeroed_page(GFP_KERNEL);
+		bp = bp->next;
+		if (!bp) {
+			free_bitmap(bitmap);
 			return NULL;
 		}
 	}
-	return swap_map;
+	return bitmap;
 }
 
-/**
- *	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)
+static int bitmap_set(struct bitmap_page *bitmap, unsigned long bit)
 {
-	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;
+	unsigned int n;
+
+	n = BITMAP_PAGE_BITS;
+	while (bitmap && n <= bit) {
+		n += BITMAP_PAGE_BITS;
+		bitmap = bitmap->next;
 	}
-	return prev;
+	if (!bitmap)
+		return -EINVAL;
+	n -= BITMAP_PAGE_BITS;
+	bit -= n;
+	n = 0;
+	while (bit >= BITS_PER_CHUNK) {
+		bit -= BITS_PER_CHUNK;
+		n++;
+	}
+	bitmap->chunks[n] |= (1UL << bit);
+	return 0;
 }
 
-/**
- *	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)
+static unsigned long alloc_swap_page(int swap, struct bitmap_page *bitmap)
 {
-	while (swap_map) {
-		if (swap_map->next_swap.val)
-			swap_free(swap_map->next_swap);
-		swap_map = swap_map->next;
+	unsigned long offset;
+
+	offset = swp_offset(get_swap_page_of_type(swap));
+	if (offset) {
+		if (bitmap_set(bitmap, offset)) {
+			swap_free(swp_entry(swap, offset));
+			offset = 0;
+		}
 	}
+	return offset;
 }
 
-/**
- *	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)
+static void free_all_swap_pages(int swap, struct bitmap_page *bitmap)
 {
-	swp_entry_t entry = (swp_entry_t){0};
-	int error;
+	unsigned int bit, n;
+	unsigned long test;
 
-	while (swap_map) {
-		swap_map->next_swap = entry;
-		if ((error = write_page((unsigned long)swap_map, &entry)))
-			return error;
-		swap_map = swap_map->next;
+	bit = 0;
+	while (bitmap) {
+		for (n = 0; n < BITMAP_PAGE_CHUNKS; n++)
+			for (test = 1UL; test; test <<= 1) {
+				if (bitmap->chunks[n] & test)
+					swap_free(swp_entry(swap, bit));
+				bit++;
+			}
+		bitmap = bitmap->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)
+ *	write_page - Write one page to given swap location.
+ *	@buf:		Address we're writing.
+ *	@offset:	Offset of the swap page we're writing to.
  */
 
-static inline void free_image_entries(struct swap_map_page *swp)
+static int write_page(void *buf, unsigned long offset)
 {
-	unsigned k;
+	swp_entry_t entry;
+	int error = -ENOSPC;
 
-	while (swp) {
-		for (k = 0; k < MAP_PAGE_SIZE; k++)
-			if (swp->entries[k].val)
-				swap_free(swp->entries[k]);
-		swp = swp->next;
+	if (offset) {
+		entry = swp_entry(root_swap, offset);
+		error = rw_swap_page_sync(WRITE, entry, virt_to_page(buf));
 	}
+	return error;
 }
 
+/*
+ *	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(long) - 1)
+
+struct swap_map_page {
+	unsigned long		entries[MAP_PAGE_ENTRIES];
+	unsigned long		next_swap;
+};
+
 /**
- *	The swap_map_handle structure is used for handling the swap map in
+ *	The swap_map_handle structure is used for handling swap in
  *	a file-alike way
  */
 
 struct swap_map_handle {
 	struct swap_map_page *cur;
+	unsigned long cur_swap;
+	struct bitmap_page *bitmap;
 	unsigned int k;
 };
 
-static inline void init_swap_map_handle(struct swap_map_handle *handle,
-                                        struct swap_map_page *map)
+static void release_swap_writer(struct swap_map_handle *handle)
 {
-	handle->cur = map;
+	if (handle->cur)
+		free_page((unsigned long)handle->cur);
+	handle->cur = NULL;
+	if (handle->bitmap)
+		free_bitmap(handle->bitmap);
+	handle->bitmap = 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->bitmap = alloc_bitmap(count_swap_pages(root_swap, 0));
+	if (!handle->bitmap) {
+		release_swap_writer(handle);
+		return -ENOMEM;
+	}
+	handle->cur_swap = alloc_swap_page(root_swap, handle->bitmap);
+	if (!handle->cur_swap) {
+		release_swap_writer(handle);
+		return -ENOSPC;
+	}
 	handle->k = 0;
+	return 0;
 }
 
-static inline int swap_map_write_page(struct swap_map_handle *handle,
-                                      unsigned long addr)
+static int swap_write_page(struct swap_map_handle *handle, void *buf)
 {
 	int error;
+	unsigned long offset;
 
-	error = write_page(addr, handle->cur->entries + handle->k);
+	if (!handle->cur)
+		return -EINVAL;
+	offset = alloc_swap_page(root_swap, handle->bitmap);
+	error = write_page(buf, offset);
 	if (error)
 		return error;
-	if (++handle->k >= MAP_PAGE_SIZE) {
-		handle->cur = handle->cur->next;
+	handle->cur->entries[handle->k++] = offset;
+	if (handle->k >= MAP_PAGE_ENTRIES) {
+		offset = alloc_swap_page(root_swap, handle->bitmap);
+		if (!offset)
+			return -ENOSPC;
+		handle->cur->next_swap = offset;
+		error = write_page(handle->cur, handle->cur_swap);
+		if (error)
+			return error;
+		memset(handle->cur, 0, PAGE_SIZE);
+		handle->cur_swap = offset;
 		handle->k = 0;
 	}
 	return 0;
 }
 
+static int flush_swap_writer(struct swap_map_handle *handle)
+{
+	if (handle->cur && handle->cur_swap)
+		return write_page(handle->cur, handle->cur_swap);
+	else
+		return -EINVAL;
+}
+
 /**
- *	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)
+ *	save_image - save the suspend image data
  */
 
-static int save_image_data(struct pbe *pblist,
-                           struct swap_map_handle *handle,
-                           unsigned int nr_pages)
+static int save_image(struct swap_map_handle *handle,
+                      struct snapshot_handle *snapshot,
+                      unsigned int nr_pages)
 {
 	unsigned int m;
-	struct pbe *p;
+	int ret;
 	int error = 0;
 
 	printk("Saving image data pages (%u pages) ...     ", nr_pages);
@@ -385,98 +391,22 @@ static int save_image_data(struct pbe *pblist,
 	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++;
-	}
+	do {
+		ret = snapshot_read_next(snapshot, PAGE_SIZE);
+		if (ret > 0) {
+			error = swap_write_page(handle, data_of(*snapshot));
+			if (error)
+				break;
+			if (!(nr_pages % m))
+				printk("\b\b\b\b%3d%%", nr_pages / m);
+			nr_pages++;
+		}
+	} while (ret > 0);
 	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.
  *
@@ -486,8 +416,7 @@ static int save_image_metadata(struct pbe *pblist,
 
 static int enough_swap(unsigned int nr_pages)
 {
-	unsigned int free_swap = swap_info[root_swap].pages -
-		swap_info[root_swap].inuse_pages;
+	unsigned int free_swap = count_swap_pages(root_swap, 1);
 
 	pr_debug("swsusp: free swap pages: %u\n", free_swap);
 	return free_swap > (nr_pages + PAGES_FOR_IO +
@@ -503,57 +432,44 @@ static int enough_swap(unsigned int nr_pages)
  *	correctly, we'll mark system clean, anyway.)
  */
 
-int swsusp_write(struct pbe *pblist, unsigned int nr_pages)
+int swsusp_write(void)
 {
-	struct swap_map_page *swap_map;
 	struct swap_map_handle handle;
-	swp_entry_t start;
+	struct snapshot_handle snapshot;
+	struct swsusp_info *header;
+	unsigned long 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)) {
+	memset(&snapshot, 0, sizeof(struct snapshot_handle));
+	error = snapshot_read_next(&snapshot, PAGE_SIZE);
+	if (error < PAGE_SIZE)
+		return error < 0 ? error : -EFAULT;
+	header = (struct swsusp_info *)data_of(snapshot);
+	if (!enough_swap(header->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);
+	error = get_swap_writer(&handle);
+	if (!error) {
+		start = handle.cur_swap;
+		error = swap_write_page(&handle, header);
+	}
 	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" );
+		error = save_image(&handle, &snapshot, header->pages - 1);
+	if (!error) {
+		flush_swap_writer(&handle);
+		printk("S");
+		error = mark_swapfiles(swp_entry(root_swap, start));
+		printk("|\n");
+	}
 	if (error)
-		goto Free_map_entries;
-
-Free_swap_map:
-	free_swap_map(swap_map);
+		free_all_swap_pages(root_swap, handle.bitmap);
+	release_swap_writer(&handle);
 	return error;
-
-Free_map_entries:
-	free_swap_map_entries(swap_map);
-Free_image_entries:
-	free_image_entries(swap_map);
-	goto Free_swap_map;
 }
 
 /**
@@ -663,45 +579,6 @@ int swsusp_resume(void)
 	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
@@ -779,14 +656,14 @@ static int bio_write_page(pgoff_t page_off, void *page)
  *	in a file-alike way
  */
 
-static inline void release_swap_map_reader(struct swap_map_handle *handle)
+static void release_swap_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,
+static int get_swap_reader(struct swap_map_handle *handle,
                                       swp_entry_t start)
 {
 	int error;
@@ -798,149 +675,80 @@ static inline int get_swap_map_reader(struct swap_map_handle *handle,
 		return -ENOMEM;
 	error = bio_read_page(swp_offset(start), handle->cur);
 	if (error) {
-		release_swap_map_reader(handle);
+		release_swap_reader(handle);
 		return error;
 	}
 	handle->k = 0;
 	return 0;
 }
 
-static inline int swap_map_read_page(struct swap_map_handle *handle, void *buf)
+static int swap_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]);
+	offset = handle->cur->entries[handle->k];
 	if (!offset)
-		return -EINVAL;
+		return -EFAULT;
 	error = bio_read_page(offset, buf);
 	if (error)
 		return error;
-	if (++handle->k >= MAP_PAGE_SIZE) {
+	if (++handle->k >= MAP_PAGE_ENTRIES) {
 		handle->k = 0;
-		offset = swp_offset(handle->cur->next_swap);
+		offset = handle->cur->next_swap;
 		if (!offset)
-			release_swap_map_reader(handle);
+			release_swap_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
+ *	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_data(struct pbe *pblist,
-                           struct swap_map_handle *handle,
-                           unsigned int nr_pages)
+static int load_image(struct swap_map_handle *handle,
+                      struct snapshot_handle *snapshot,
+                      unsigned int nr_pages)
 {
-	int error;
 	unsigned int m;
-	struct pbe *p;
+	int ret;
+	int error = 0;
 
-	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++;
-	}
+	do {
+		ret = snapshot_write_next(snapshot, PAGE_SIZE);
+		if (ret > 0) {
+			error = swap_read_page(handle, data_of(*snapshot));
+			if (error)
+				break;
+			if (!(nr_pages % m))
+				printk("\b\b\b\b%3d%%", nr_pages / m);
+			nr_pages++;
+		}
+	} while (ret > 0);
 	if (!error)
 		printk("\b\b\b\bdone\n");
+	if (!snapshot_image_loaded(snapshot))
+		error = -ENODATA;
 	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 swsusp_read(void)
 {
 	int error;
-	struct pbe *p, *pblist;
 	struct swap_map_handle handle;
+	struct snapshot_handle snapshot;
+	struct swsusp_info *header;
 	unsigned int nr_pages;
 
 	if (IS_ERR(resume_bdev)) {
@@ -948,38 +756,19 @@ int swsusp_read(struct pbe **pblist_ptr)
 		return PTR_ERR(resume_bdev);
 	}
 
-	error = get_swap_map_reader(&handle, swsusp_header.image);
+	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_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);
+		error = swap_read_page(&handle, header);
 	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;
+		nr_pages = header->image_pages;
+		error = load_image(&handle, &snapshot, nr_pages);
 	}
-	release_swap_map_reader(&handle);
+	release_swap_reader(&handle);
 
 	blkdev_put(resume_bdev);