kernel/power/swap.c

   1 /*
   2  * linux/kernel/power/swap.c
   3  *
   4  * This file provides functions for reading the suspend image from
   5  * and writing it to a swap partition.
   6  *
   7  * Copyright (C) 1998,2001-2005 Pavel Machek <pavel@suse.cz>
   8  * Copyright (C) 2006 Rafael J. Wysocki <rjw@sisk.pl>
   9  *
  10  * This file is released under the GPLv2.
  11  *
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/file.h>
  16 #include <linux/delay.h>
  17 #include <linux/bitops.h>
  18 #include <linux/genhd.h>
  19 #include <linux/device.h>
  20 #include <linux/buffer_head.h>
  21 #include <linux/bio.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/swap.h>
  24 #include <linux/swapops.h>
  25 #include <linux/pm.h>
  26 #include <linux/slab.h>
  27
  28 #include "power.h"
  29
  30 #define SWSUSP_SIG      "S1SUSPEND"
  31
  32 struct swsusp_header {
  33         char reserved[PAGE_SIZE - 20 - sizeof(sector_t) - sizeof(int)];
  34         sector_t image;
  35         unsigned int flags;     /* Flags to pass to the "boot" kernel */
  36         char    orig_sig[10];
  37         char    sig[10];
  38 } __attribute__((packed));
  39
  40 static struct swsusp_header *swsusp_header;
  41
  42 /**
  43  *      The following functions are used for tracing the allocated
  44  *      swap pages, so that they can be freed in case of an error.
  45  */
  46
  47 struct swsusp_extent {
  48         struct rb_node node;
  49         unsigned long start;
  50         unsigned long end;
  51 };
  52
  53 static struct rb_root swsusp_extents = RB_ROOT;
  54
  55 static int swsusp_extents_insert(unsigned long swap_offset)
  56 {
  57         struct rb_node **new = &(swsusp_extents.rb_node);
  58         struct rb_node *parent = NULL;
  59         struct swsusp_extent *ext;
  60
  61         /* Figure out where to put the new node */
  62         while (*new) {
  63                 ext = container_of(*new, struct swsusp_extent, node);
  64                 parent = *new;
  65                 if (swap_offset < ext->start) {
  66                         /* Try to merge */
  67                         if (swap_offset == ext->start - 1) {
  68                                 ext->start--;
  69                                 return 0;
  70                         }
  71                         new = &((*new)->rb_left);
  72                 } else if (swap_offset > ext->end) {
  73                         /* Try to merge */
  74                         if (swap_offset == ext->end + 1) {
  75                                 ext->end++;
  76                                 return 0;
  77                         }
  78                         new = &((*new)->rb_right);
  79                 } else {
  80                         /* It already is in the tree */
  81                         return -EINVAL;
  82                 }
  83         }
  84         /* Add the new node and rebalance the tree. */
  85         ext = kzalloc(sizeof(struct swsusp_extent), GFP_KERNEL);
  86         if (!ext)
  87                 return -ENOMEM;
  88
  89         ext->start = swap_offset;
  90         ext->end = swap_offset;
  91         rb_link_node(&ext->node, parent, new);
  92         rb_insert_color(&ext->node, &swsusp_extents);
  93         return 0;
  94 }
  95
  96 /**
  97  *      alloc_swapdev_block - allocate a swap page and register that it has
  98  *      been allocated, so that it can be freed in case of an error.
  99  */
 100
 101 sector_t alloc_swapdev_block(int swap)
 102 {
 103         unsigned long offset;
 104
 105         offset = swp_offset(get_swap_page_of_type(swap));
 106         if (offset) {
 107                 if (swsusp_extents_insert(offset))
 108                         swap_free(swp_entry(swap, offset));
 109                 else
 110                         return swapdev_block(swap, offset);
 111         }
 112         return 0;
 113 }
 114
 115 /**
 116  *      free_all_swap_pages - free swap pages allocated for saving image data.
 117  *      It also frees the extents used to register which swap entres had been
 118  *      allocated.
 119  */
 120
 121 void free_all_swap_pages(int swap)
 122 {
 123         struct rb_node *node;
 124
 125         while ((node = swsusp_extents.rb_node)) {
 126                 struct swsusp_extent *ext;
 127                 unsigned long offset;
 128
 129                 ext = container_of(node, struct swsusp_extent, node);
 130                 rb_erase(node, &swsusp_extents);
 131                 for (offset = ext->start; offset <= ext->end; offset++)
 132                         swap_free(swp_entry(swap, offset));
 133
 134                 kfree(ext);
 135         }
 136 }
 137
 138 int swsusp_swap_in_use(void)
 139 {
 140         return (swsusp_extents.rb_node != NULL);
 141 }
 142
 143 /*
 144  * General things
 145  */
 146
 147 static unsigned short root_swap = 0xffff;
 148 static struct block_device *resume_bdev;
 149
 150 /**
 151  *      submit - submit BIO request.
 152  *      @rw:    READ or WRITE.
 153  *      @off    physical offset of page.
 154  *      @page:  page we're reading or writing.
 155  *      @bio_chain: list of pending biod (for async reading)
 156  *
 157  *      Straight from the textbook - allocate and initialize the bio.
 158  *      If we're reading, make sure the page is marked as dirty.
 159  *      Then submit it and, if @bio_chain == NULL, wait.
 160  */
 161 static int submit(int rw, pgoff_t page_off, struct page *page,
 162                         struct bio **bio_chain)
 163 {
 164         const int bio_rw = rw | (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
 165         struct bio *bio;
 166
 167         bio = bio_alloc(__GFP_WAIT | __GFP_HIGH, 1);
 168         bio->bi_sector = page_off * (PAGE_SIZE >> 9);
 169         bio->bi_bdev = resume_bdev;
 170         bio->bi_end_io = end_swap_bio_read;
 171
 172         if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE) {
 173                 printk(KERN_ERR "PM: Adding page to bio failed at %ld\n",
 174                         page_off);
 175                 bio_put(bio);
 176                 return -EFAULT;
 177         }
 178
 179         lock_page(page);
 180         bio_get(bio);
 181
 182         if (bio_chain == NULL) {
 183                 submit_bio(bio_rw, bio);
 184                 wait_on_page_locked(page);
 185                 if (rw == READ)
 186                         bio_set_pages_dirty(bio);
 187                 bio_put(bio);
 188         } else {
 189                 if (rw == READ)
 190                         get_page(page); /* These pages are freed later */
 191                 bio->bi_private = *bio_chain;
 192                 *bio_chain = bio;
 193                 submit_bio(bio_rw, bio);
 194         }
 195         return 0;
 196 }
 197
 198 static int bio_read_page(pgoff_t page_off, void *addr, struct bio **bio_chain)
 199 {
 200         return submit(READ, page_off, virt_to_page(addr), bio_chain);
 201 }
 202
 203 static int bio_write_page(pgoff_t page_off, void *addr, struct bio **bio_chain)
 204 {
 205         return submit(WRITE, page_off, virt_to_page(addr), bio_chain);
 206 }
 207
 208 static int wait_on_bio_chain(struct bio **bio_chain)
 209 {
 210         struct bio *bio;
 211         struct bio *next_bio;
 212         int ret = 0;
 213
 214         if (bio_chain == NULL)
 215                 return 0;
 216
 217         bio = *bio_chain;
 218         if (bio == NULL)
 219                 return 0;
 220         while (bio) {
 221                 struct page *page;
 222
 223                 next_bio = bio->bi_private;
 224                 page = bio->bi_io_vec[0].bv_page;
 225                 wait_on_page_locked(page);
 226                 if (!PageUptodate(page) || PageError(page))
 227                         ret = -EIO;
 228                 put_page(page);
 229                 bio_put(bio);
 230                 bio = next_bio;
 231         }
 232         *bio_chain = NULL;
 233         return ret;
 234 }
 235
 236 /*
 237  * Saving part
 238  */
 239
 240 static int mark_swapfiles(sector_t start, unsigned int flags)
 241 {
 242         int error;
 243
 244         bio_read_page(swsusp_resume_block, swsusp_header, NULL);
 245         if (!memcmp("SWAP-SPACE",swsusp_header->sig, 10) ||
 246             !memcmp("SWAPSPACE2",swsusp_header->sig, 10)) {
 247                 memcpy(swsusp_header->orig_sig,swsusp_header->sig, 10);
 248                 memcpy(swsusp_header->sig,SWSUSP_SIG, 10);
 249                 swsusp_header->image = start;
 250                 swsusp_header->flags = flags;
 251                 error = bio_write_page(swsusp_resume_block,
 252                                         swsusp_header, NULL);
 253         } else {
 254                 printk(KERN_ERR "PM: Swap header not found!\n");
 255                 error = -ENODEV;
 256         }
 257         return error;
 258 }
 259
 260 /**
 261  *      swsusp_swap_check - check if the resume device is a swap device
 262  *      and get its index (if so)
 263  */
 264
 265 static int swsusp_swap_check(void) /* This is called before saving image */
 266 {
 267         int res;
 268
 269         res = swap_type_of(swsusp_resume_device, swsusp_resume_block,
 270                         &resume_bdev);
 271         if (res < 0)
 272                 return res;
 273
 274         root_swap = res;
 275         res = blkdev_get(resume_bdev, FMODE_WRITE);
 276         if (res)
 277                 return res;
 278
 279         res = set_blocksize(resume_bdev, PAGE_SIZE);
 280         if (res < 0)
 281                 blkdev_put(resume_bdev, FMODE_WRITE);
 282
 283         return res;
 284 }
 285
 286 /**
 287  *      write_page - Write one page to given swap location.
 288  *      @buf:           Address we're writing.
 289  *      @offset:        Offset of the swap page we're writing to.
 290  *      @bio_chain:     Link the next write BIO here
 291  */
 292
 293 static int write_page(void *buf, sector_t offset, struct bio **bio_chain)
 294 {
 295         void *src;
 296
 297         if (!offset)
 298                 return -ENOSPC;
 299
 300         if (bio_chain) {
 301                 src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
 302                 if (src) {
 303                         memcpy(src, buf, PAGE_SIZE);
 304                 } else {
 305                         WARN_ON_ONCE(1);
 306                         bio_chain = NULL;       /* Go synchronous */
 307                         src = buf;
 308                 }
 309         } else {
 310                 src = buf;
 311         }
 312         return bio_write_page(offset, src, bio_chain);
 313 }
 314
 315 /*
 316  *      The swap map is a data structure used for keeping track of each page
 317  *      written to a swap partition.  It consists of many swap_map_page
 318  *      structures that contain each an array of MAP_PAGE_SIZE swap entries.
 319  *      These structures are stored on the swap and linked together with the
 320  *      help of the .next_swap member.
 321  *
 322  *      The swap map is created during suspend.  The swap map pages are
 323  *      allocated and populated one at a time, so we only need one memory
 324  *      page to set up the entire structure.
 325  *
 326  *      During resume we also only need to use one swap_map_page structure
 327  *      at a time.
 328  */
 329
 330 #define MAP_PAGE_ENTRIES        (PAGE_SIZE / sizeof(sector_t) - 1)
 331
 332 struct swap_map_page {
 333         sector_t entries[MAP_PAGE_ENTRIES];
 334         sector_t next_swap;
 335 };
 336
 337 /**
 338  *      The swap_map_handle structure is used for handling swap in
 339  *      a file-alike way
 340  */
 341
 342 struct swap_map_handle {
 343         struct swap_map_page *cur;
 344         sector_t cur_swap;
 345         unsigned int k;
 346 };
 347
 348 static void release_swap_writer(struct swap_map_handle *handle)
 349 {
 350         if (handle->cur)
 351                 free_page((unsigned long)handle->cur);
 352         handle->cur = NULL;
 353 }
 354
 355 static int get_swap_writer(struct swap_map_handle *handle)
 356 {
 357         handle->cur = (struct swap_map_page *)get_zeroed_page(GFP_KERNEL);
 358         if (!handle->cur)
 359                 return -ENOMEM;
 360         handle->cur_swap = alloc_swapdev_block(root_swap);
 361         if (!handle->cur_swap) {
 362                 release_swap_writer(handle);
 363                 return -ENOSPC;
 364         }
 365         handle->k = 0;
 366         return 0;
 367 }
 368
 369 static int swap_write_page(struct swap_map_handle *handle, void *buf,
 370                                 struct bio **bio_chain)
 371 {
 372         int error = 0;
 373         sector_t offset;
 374
 375         if (!handle->cur)
 376                 return -EINVAL;
 377         offset = alloc_swapdev_block(root_swap);
 378         error = write_page(buf, offset, bio_chain);
 379         if (error)
 380                 return error;
 381         handle->cur->entries[handle->k++] = offset;
 382         if (handle->k >= MAP_PAGE_ENTRIES) {
 383                 error = wait_on_bio_chain(bio_chain);
 384                 if (error)
 385                         goto out;
 386                 offset = alloc_swapdev_block(root_swap);
 387                 if (!offset)
 388                         return -ENOSPC;
 389                 handle->cur->next_swap = offset;
 390                 error = write_page(handle->cur, handle->cur_swap, NULL);
 391                 if (error)
 392                         goto out;
 393                 memset(handle->cur, 0, PAGE_SIZE);
 394                 handle->cur_swap = offset;
 395                 handle->k = 0;
 396         }
 397  out:
 398         return error;
 399 }
 400
 401 static int flush_swap_writer(struct swap_map_handle *handle)
 402 {
 403         if (handle->cur && handle->cur_swap)
 404                 return write_page(handle->cur, handle->cur_swap, NULL);
 405         else
 406                 return -EINVAL;
 407 }
 408
 409 /**
 410  *      save_image - save the suspend image data
 411  */
 412
 413 static int save_image(struct swap_map_handle *handle,
 414                       struct snapshot_handle *snapshot,
 415                       unsigned int nr_to_write)
 416 {
 417         unsigned int m;
 418         int ret;
 419         int nr_pages;
 420         int err2;
 421         struct bio *bio;
 422         struct timeval start;
 423         struct timeval stop;
 424
 425         printk(KERN_INFO "PM: Saving image data pages (%u pages) ...     ",
 426                 nr_to_write);
 427         m = nr_to_write / 100;
 428         if (!m)
 429                 m = 1;
 430         nr_pages = 0;
 431         bio = NULL;
 432         do_gettimeofday(&start);
 433         while (1) {
 434                 ret = snapshot_read_next(snapshot, PAGE_SIZE);
 435                 if (ret <= 0)
 436                         break;
 437                 ret = swap_write_page(handle, data_of(*snapshot), &bio);
 438                 if (ret)
 439                         break;
 440                 if (!(nr_pages % m))
 441                         printk(KERN_CONT "\b\b\b\b%3d%%", nr_pages / m);
 442                 nr_pages++;
 443         }
 444         err2 = wait_on_bio_chain(&bio);
 445         do_gettimeofday(&stop);
 446         if (!ret)
 447                 ret = err2;
 448         if (!ret)
 449                 printk(KERN_CONT "\b\b\b\bdone\n");
 450         else
 451                 printk(KERN_CONT "\n");
 452         swsusp_show_speed(&start, &stop, nr_to_write, "Wrote");
 453         return ret;
 454 }
 455
 456 /**
 457  *      enough_swap - Make sure we have enough swap to save the image.
 458  *
 459  *      Returns TRUE or FALSE after checking the total amount of swap
 460  *      space avaiable from the resume partition.
 461  */
 462
 463 static int enough_swap(unsigned int nr_pages)
 464 {
 465         unsigned int free_swap = count_swap_pages(root_swap, 1);
 466
 467         pr_debug("PM: Free swap pages: %u\n", free_swap);
 468         return free_swap > nr_pages + PAGES_FOR_IO;
 469 }
 470
 471 /**
 472  *      swsusp_write - Write entire image and metadata.
 473  *      @flags: flags to pass to the "boot" kernel in the image header
 474  *
 475  *      It is important _NOT_ to umount filesystems at this point. We want
 476  *      them synced (in case something goes wrong) but we DO not want to mark
 477  *      filesystem clean: it is not. (And it does not matter, if we resume
 478  *      correctly, we'll mark system clean, anyway.)
 479  */
 480
 481 int swsusp_write(unsigned int flags)
 482 {
 483         struct swap_map_handle handle;
 484         struct snapshot_handle snapshot;
 485         struct swsusp_info *header;
 486         int error;
 487
 488         error = swsusp_swap_check();
 489         if (error) {
 490                 printk(KERN_ERR "PM: Cannot find swap device, try "
 491                                 "swapon -a.\n");
 492                 return error;
 493         }
 494         memset(&snapshot, 0, sizeof(struct snapshot_handle));
 495         error = snapshot_read_next(&snapshot, PAGE_SIZE);
 496         if (error < PAGE_SIZE) {
 497                 if (error >= 0)
 498                         error = -EFAULT;
 499
 500                 goto out;
 501         }
 502         header = (struct swsusp_info *)data_of(snapshot);
 503         if (!enough_swap(header->pages)) {
 504                 printk(KERN_ERR "PM: Not enough free swap\n");
 505                 error = -ENOSPC;
 506                 goto out;
 507         }
 508         error = get_swap_writer(&handle);
 509         if (!error) {
 510                 sector_t start = handle.cur_swap;
 511
 512                 error = swap_write_page(&handle, header, NULL);
 513                 if (!error)
 514                         error = save_image(&handle, &snapshot,
 515                                         header->pages - 1);
 516
 517                 if (!error) {
 518                         flush_swap_writer(&handle);
 519                         printk(KERN_INFO "PM: S");
 520                         error = mark_swapfiles(start, flags);
 521                         printk("|\n");
 522                 }
 523         }
 524         if (error)
 525                 free_all_swap_pages(root_swap);
 526
 527         release_swap_writer(&handle);
 528  out:
 529         swsusp_close(FMODE_WRITE);
 530         return error;
 531 }
 532
 533 /**
 534  *      The following functions allow us to read data using a swap map
 535  *      in a file-alike way
 536  */
 537
 538 static void release_swap_reader(struct swap_map_handle *handle)
 539 {
 540         if (handle->cur)
 541                 free_page((unsigned long)handle->cur);
 542         handle->cur = NULL;
 543 }
 544
 545 static int get_swap_reader(struct swap_map_handle *handle, sector_t start)
 546 {
 547         int error;
 548
 549         if (!start)
 550                 return -EINVAL;
 551
 552         handle->cur = (struct swap_map_page *)get_zeroed_page(__GFP_WAIT | __GFP_HIGH);
 553         if (!handle->cur)
 554                 return -ENOMEM;
 555
 556         error = bio_read_page(start, handle->cur, NULL);
 557         if (error) {
 558                 release_swap_reader(handle);
 559                 return error;
 560         }
 561         handle->k = 0;
 562         return 0;
 563 }
 564
 565 static int swap_read_page(struct swap_map_handle *handle, void *buf,
 566                                 struct bio **bio_chain)
 567 {
 568         sector_t offset;
 569         int error;
 570
 571         if (!handle->cur)
 572                 return -EINVAL;
 573         offset = handle->cur->entries[handle->k];
 574         if (!offset)
 575                 return -EFAULT;
 576         error = bio_read_page(offset, buf, bio_chain);
 577         if (error)
 578                 return error;
 579         if (++handle->k >= MAP_PAGE_ENTRIES) {
 580                 error = wait_on_bio_chain(bio_chain);
 581                 handle->k = 0;
 582                 offset = handle->cur->next_swap;
 583                 if (!offset)
 584                         release_swap_reader(handle);
 585                 else if (!error)
 586                         error = bio_read_page(offset, handle->cur, NULL);
 587         }
 588         return error;
 589 }
 590
 591 /**
 592  *      load_image - load the image using the swap map handle
 593  *      @handle and the snapshot handle @snapshot
 594  *      (assume there are @nr_pages pages to load)
 595  */
 596
 597 static int load_image(struct swap_map_handle *handle,
 598                       struct snapshot_handle *snapshot,
 599                       unsigned int nr_to_read)
 600 {
 601         unsigned int m;
 602         int error = 0;
 603         struct timeval start;
 604         struct timeval stop;
 605         struct bio *bio;
 606         int err2;
 607         unsigned nr_pages;
 608
 609         printk(KERN_INFO "PM: Loading image data pages (%u pages) ...     ",
 610                 nr_to_read);
 611         m = nr_to_read / 100;
 612         if (!m)
 613                 m = 1;
 614         nr_pages = 0;
 615         bio = NULL;
 616         do_gettimeofday(&start);
 617         for ( ; ; ) {
 618                 error = snapshot_write_next(snapshot, PAGE_SIZE);
 619                 if (error <= 0)
 620                         break;
 621                 error = swap_read_page(handle, data_of(*snapshot), &bio);
 622                 if (error)
 623                         break;
 624                 if (snapshot->sync_read)
 625                         error = wait_on_bio_chain(&bio);
 626                 if (error)
 627                         break;
 628                 if (!(nr_pages % m))
 629                         printk("\b\b\b\b%3d%%", nr_pages / m);
 630                 nr_pages++;
 631         }
 632         err2 = wait_on_bio_chain(&bio);
 633         do_gettimeofday(&stop);
 634         if (!error)
 635                 error = err2;
 636         if (!error) {
 637                 printk("\b\b\b\bdone\n");
 638                 snapshot_write_finalize(snapshot);
 639                 if (!snapshot_image_loaded(snapshot))
 640                         error = -ENODATA;
 641         } else
 642                 printk("\n");
 643         swsusp_show_speed(&start, &stop, nr_to_read, "Read");
 644         return error;
 645 }
 646
 647 /**
 648  *      swsusp_read - read the hibernation image.
 649  *      @flags_p: flags passed by the "frozen" kernel in the image header should
 650  *                be written into this memeory location
 651  */
 652
 653 int swsusp_read(unsigned int *flags_p)
 654 {
 655         int error;
 656         struct swap_map_handle handle;
 657         struct snapshot_handle snapshot;
 658         struct swsusp_info *header;
 659
 660         *flags_p = swsusp_header->flags;
 661
 662         memset(&snapshot, 0, sizeof(struct snapshot_handle));
 663         error = snapshot_write_next(&snapshot, PAGE_SIZE);
 664         if (error < PAGE_SIZE)
 665                 return error < 0 ? error : -EFAULT;
 666         header = (struct swsusp_info *)data_of(snapshot);
 667         error = get_swap_reader(&handle, swsusp_header->image);
 668         if (!error)
 669                 error = swap_read_page(&handle, header, NULL);
 670         if (!error)
 671                 error = load_image(&handle, &snapshot, header->pages - 1);
 672         release_swap_reader(&handle);
 673
 674         if (!error)
 675                 pr_debug("PM: Image successfully loaded\n");
 676         else
 677                 pr_debug("PM: Error %d resuming\n", error);
 678         return error;
 679 }
 680
 681 /**
 682  *      swsusp_check - Check for swsusp signature in the resume device
 683  */
 684
 685 int swsusp_check(void)
 686 {
 687         int error;
 688
 689         resume_bdev = open_by_devnum(swsusp_resume_device, FMODE_READ);
 690         if (!IS_ERR(resume_bdev)) {
 691                 set_blocksize(resume_bdev, PAGE_SIZE);
 692                 memset(swsusp_header, 0, PAGE_SIZE);
 693                 error = bio_read_page(swsusp_resume_block,
 694                                         swsusp_header, NULL);
 695                 if (error)
 696                         goto put;
 697
 698                 if (!memcmp(SWSUSP_SIG, swsusp_header->sig, 10)) {
 699                         memcpy(swsusp_header->sig, swsusp_header->orig_sig, 10);
 700                         /* Reset swap signature now */
 701                         error = bio_write_page(swsusp_resume_block,
 702                                                 swsusp_header, NULL);
 703                 } else {
 704                         error = -EINVAL;
 705                 }
 706
 707 put:
 708                 if (error)
 709                         blkdev_put(resume_bdev, FMODE_READ);
 710                 else
 711                         pr_debug("PM: Signature found, resuming\n");
 712         } else {
 713                 error = PTR_ERR(resume_bdev);
 714         }
 715
 716         if (error)
 717                 pr_debug("PM: Error %d checking image file\n", error);
 718
 719         return error;
 720 }
 721
 722 /**
 723  *      swsusp_close - close swap device.
 724  */
 725
 726 void swsusp_close(fmode_t mode)
 727 {
 728         if (IS_ERR(resume_bdev)) {
 729                 pr_debug("PM: Image device not initialised\n");
 730                 return;
 731         }
 732
 733         blkdev_put(resume_bdev, mode);
 734 }
 735
 736 static int swsusp_header_init(void)
 737 {
 738         swsusp_header = (struct swsusp_header*) __get_free_page(GFP_KERNEL);
 739         if (!swsusp_header)
 740                 panic("Could not allocate memory for swsusp_header\n");
 741         return 0;
 742 }
 743
 744 core_initcall(swsusp_header_init);