summaryrefslogtreecommitdiff
path: root/kernel/power/swsusp.c
blob: 457084f500107fb7486173244cf8055814e7b78c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
/*
 * 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;

int in_suspend __nosavedata = 0;

#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;

/*
 * 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;
}

/**
 *	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 = swap_type_of(swsusp_resume_device);

	if (res >= 0) {
		root_swap = res;
		return 0;
	}
	return res;
}

/**
 *	The bitmap is used for tracing allocated swap pages
 *
 *	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.
 */

#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;
};

/**
 *	The following functions are used for tracing the allocated
 *	swap pages, so that they can be freed in case of an error.
 *
 *	The functions operate on a linked bitmap structure defined
 *	above
 */

static void free_bitmap(struct bitmap_page *bitmap)
{
	struct bitmap_page *bp;

	while (bitmap) {
		bp = bitmap->next;
		free_page((unsigned long)bitmap);
		bitmap = bp;
	}
}

static struct bitmap_page *alloc_bitmap(unsigned int nr_bits)
{
	struct bitmap_page *bitmap, *bp;
	unsigned int n;

	if (!nr_bits)
		return NULL;

	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 bitmap;
}

static int bitmap_set(struct bitmap_page *bitmap, unsigned long bit)
{
	unsigned int n;

	n = BITMAP_PAGE_BITS;
	while (bitmap && n <= bit) {
		n += BITMAP_PAGE_BITS;
		bitmap = bitmap->next;
	}
	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;
}

static unsigned long alloc_swap_page(int swap, struct bitmap_page *bitmap)
{
	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;
}

static void free_all_swap_pages(int swap, struct bitmap_page *bitmap)
{
	unsigned int bit, n;
	unsigned long test;

	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;
	}
}

/**
 *	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 int write_page(void *buf, unsigned long offset)
{
	swp_entry_t entry;
	int error = -ENOSPC;

	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 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 void release_swap_writer(struct swap_map_handle *handle)
{
	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 int swap_write_page(struct swap_map_handle *handle, void *buf)
{
	int error;
	unsigned long offset;

	if (!handle->cur)
		return -EINVAL;
	offset = alloc_swap_page(root_swap, handle->bitmap);
	error = write_page(buf, offset);
	if (error)
		return error;
	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 - save the suspend image data
 */

static int save_image(struct swap_map_handle *handle,
                      struct snapshot_handle *snapshot,
                      unsigned int nr_pages)
{
	unsigned int m;
	int ret;
	int error = 0;

	printk("Saving image data pages (%u pages) ...     ", nr_pages);
	m = nr_pages / 100;
	if (!m)
		m = 1;
	nr_pages = 0;
	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;
}

/**
 *	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("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(void)
{
	struct swap_map_handle handle;
	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;
	}
	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;
	}
	error = get_swap_writer(&handle);
	if (!error) {
		start = handle.cur_swap;
		error = swap_write_page(&handle, header);
	}
	if (!error)
		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)
		free_all_swap_pages(root_swap, handle.bitmap);
	release_swap_writer(&handle);
	return error;
}

/**
 *	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;
}

/*
 *	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 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,
                                      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_reader(handle);
		return error;
	}
	handle->k = 0;
	return 0;
}

static int swap_read_page(struct swap_map_handle *handle, void *buf)
{
	unsigned long offset;
	int error;

	if (!handle->cur)
		return -EINVAL;
	offset = handle->cur->entries[handle->k];
	if (!offset)
		return -EFAULT;
	error = bio_read_page(offset, buf);
	if (error)
		return error;
	if (++handle->k >= MAP_PAGE_ENTRIES) {
		handle->k = 0;
		offset = handle->cur->next_swap;
		if (!offset)
			release_swap_reader(handle);
		else
			error = bio_read_page(offset, handle->cur);
	}
	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_pages)
{
	unsigned int m;
	int ret;
	int error = 0;

	printk("Loading image data pages (%u pages) ...     ", nr_pages);
	m = nr_pages / 100;
	if (!m)
		m = 1;
	nr_pages = 0;
	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;
}

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

	if (IS_ERR(resume_bdev)) {
		pr_debug("swsusp: block 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);
	if (!error) {
		nr_pages = header->image_pages;
		error = load_image(&handle, &snapshot, nr_pages);
	}
	release_swap_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);
}