Pileus Git - ~andy/linux/blob - kernel/power/snapshot.c

   1 /*
   2  * linux/kernel/power/snapshot.c
   3  *
   4  * This file provide system snapshot/restore functionality.
   5  *
   6  * Copyright (C) 1998-2005 Pavel Machek <pavel@suse.cz>
   7  *
   8  * This file is released under the GPLv2, and is based on swsusp.c.
   9  *
  10  */
  11
  12
  13 #include <linux/version.h>
  14 #include <linux/module.h>
  15 #include <linux/mm.h>
  16 #include <linux/suspend.h>
  17 #include <linux/smp_lock.h>
  18 #include <linux/delay.h>
  19 #include <linux/bitops.h>
  20 #include <linux/spinlock.h>
  21 #include <linux/kernel.h>
  22 #include <linux/pm.h>
  23 #include <linux/device.h>
  24 #include <linux/bootmem.h>
  25 #include <linux/syscalls.h>
  26 #include <linux/console.h>
  27 #include <linux/highmem.h>
  28
  29 #include <asm/uaccess.h>
  30 #include <asm/mmu_context.h>
  31 #include <asm/pgtable.h>
  32 #include <asm/tlbflush.h>
  33 #include <asm/io.h>
  34
  35 #include "power.h"
  36
  37 /* List of PBEs used for creating and restoring the suspend image */
  38 struct pbe *restore_pblist;
  39
  40 static unsigned int nr_copy_pages;
  41 static unsigned int nr_meta_pages;
  42 static unsigned long *buffer;
  43
  44 #ifdef CONFIG_HIGHMEM
  45 unsigned int count_highmem_pages(void)
  46 {
  47         struct zone *zone;
  48         unsigned long zone_pfn;
  49         unsigned int n = 0;
  50
  51         for_each_zone (zone)
  52                 if (is_highmem(zone)) {
  53                         mark_free_pages(zone);
  54                         for (zone_pfn = 0; zone_pfn < zone->spanned_pages; zone_pfn++) {
  55                                 struct page *page;
  56                                 unsigned long pfn = zone_pfn + zone->zone_start_pfn;
  57                                 if (!pfn_valid(pfn))
  58                                         continue;
  59                                 page = pfn_to_page(pfn);
  60                                 if (PageReserved(page))
  61                                         continue;
  62                                 if (PageNosaveFree(page))
  63                                         continue;
  64                                 n++;
  65                         }
  66                 }
  67         return n;
  68 }
  69
  70 struct highmem_page {
  71         char *data;
  72         struct page *page;
  73         struct highmem_page *next;
  74 };
  75
  76 static struct highmem_page *highmem_copy;
  77
  78 static int save_highmem_zone(struct zone *zone)
  79 {
  80         unsigned long zone_pfn;
  81         mark_free_pages(zone);
  82         for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn) {
  83                 struct page *page;
  84                 struct highmem_page *save;
  85                 void *kaddr;
  86                 unsigned long pfn = zone_pfn + zone->zone_start_pfn;
  87
  88                 if (!(pfn%10000))
  89                         printk(".");
  90                 if (!pfn_valid(pfn))
  91                         continue;
  92                 page = pfn_to_page(pfn);
  93                 /*
  94                  * This condition results from rvmalloc() sans vmalloc_32()
  95                  * and architectural memory reservations. This should be
  96                  * corrected eventually when the cases giving rise to this
  97                  * are better understood.
  98                  */
  99                 if (PageReserved(page))
 100                         continue;
 101                 BUG_ON(PageNosave(page));
 102                 if (PageNosaveFree(page))
 103                         continue;
 104                 save = kmalloc(sizeof(struct highmem_page), GFP_ATOMIC);
 105                 if (!save)
 106                         return -ENOMEM;
 107                 save->next = highmem_copy;
 108                 save->page = page;
 109                 save->data = (void *) get_zeroed_page(GFP_ATOMIC);
 110                 if (!save->data) {
 111                         kfree(save);
 112                         return -ENOMEM;
 113                 }
 114                 kaddr = kmap_atomic(page, KM_USER0);
 115                 memcpy(save->data, kaddr, PAGE_SIZE);
 116                 kunmap_atomic(kaddr, KM_USER0);
 117                 highmem_copy = save;
 118         }
 119         return 0;
 120 }
 121
 122 int save_highmem(void)
 123 {
 124         struct zone *zone;
 125         int res = 0;
 126
 127         pr_debug("swsusp: Saving Highmem");
 128         drain_local_pages();
 129         for_each_zone (zone) {
 130                 if (is_highmem(zone))
 131                         res = save_highmem_zone(zone);
 132                 if (res)
 133                         return res;
 134         }
 135         printk("\n");
 136         return 0;
 137 }
 138
 139 int restore_highmem(void)
 140 {
 141         printk("swsusp: Restoring Highmem\n");
 142         while (highmem_copy) {
 143                 struct highmem_page *save = highmem_copy;
 144                 void *kaddr;
 145                 highmem_copy = save->next;
 146
 147                 kaddr = kmap_atomic(save->page, KM_USER0);
 148                 memcpy(kaddr, save->data, PAGE_SIZE);
 149                 kunmap_atomic(kaddr, KM_USER0);
 150                 free_page((long) save->data);
 151                 kfree(save);
 152         }
 153         return 0;
 154 }
 155 #else
 156 static inline unsigned int count_highmem_pages(void) {return 0;}
 157 static inline int save_highmem(void) {return 0;}
 158 static inline int restore_highmem(void) {return 0;}
 159 #endif
 160
 161 /**
 162  *      @safe_needed - on resume, for storing the PBE list and the image,
 163  *      we can only use memory pages that do not conflict with the pages
 164  *      used before suspend.
 165  *
 166  *      The unsafe pages are marked with the PG_nosave_free flag
 167  *      and we count them using unsafe_pages
 168  */
 169
 170 static unsigned int unsafe_pages;
 171
 172 static void *alloc_image_page(gfp_t gfp_mask, int safe_needed)
 173 {
 174         void *res;
 175
 176         res = (void *)get_zeroed_page(gfp_mask);
 177         if (safe_needed)
 178                 while (res && PageNosaveFree(virt_to_page(res))) {
 179                         /* The page is unsafe, mark it for swsusp_free() */
 180                         SetPageNosave(virt_to_page(res));
 181                         unsafe_pages++;
 182                         res = (void *)get_zeroed_page(gfp_mask);
 183                 }
 184         if (res) {
 185                 SetPageNosave(virt_to_page(res));
 186                 SetPageNosaveFree(virt_to_page(res));
 187         }
 188         return res;
 189 }
 190
 191 unsigned long get_safe_page(gfp_t gfp_mask)
 192 {
 193         return (unsigned long)alloc_image_page(gfp_mask, 1);
 194 }
 195
 196 /**
 197  *      free_image_page - free page represented by @addr, allocated with
 198  *      alloc_image_page (page flags set by it must be cleared)
 199  */
 200
 201 static inline void free_image_page(void *addr, int clear_nosave_free)
 202 {
 203         ClearPageNosave(virt_to_page(addr));
 204         if (clear_nosave_free)
 205                 ClearPageNosaveFree(virt_to_page(addr));
 206         free_page((unsigned long)addr);
 207 }
 208
 209 /**
 210  *      pfn_is_nosave - check if given pfn is in the 'nosave' section
 211  */
 212
 213 static inline int pfn_is_nosave(unsigned long pfn)
 214 {
 215         unsigned long nosave_begin_pfn = __pa(&__nosave_begin) >> PAGE_SHIFT;
 216         unsigned long nosave_end_pfn = PAGE_ALIGN(__pa(&__nosave_end)) >> PAGE_SHIFT;
 217         return (pfn >= nosave_begin_pfn) && (pfn < nosave_end_pfn);
 218 }
 219
 220 /**
 221  *      saveable - Determine whether a page should be cloned or not.
 222  *      @pfn:   The page
 223  *
 224  *      We save a page if it isn't Nosave, and is not in the range of pages
 225  *      statically defined as 'unsaveable', and it
 226  *      isn't a part of a free chunk of pages.
 227  */
 228
 229 static struct page *saveable_page(unsigned long pfn)
 230 {
 231         struct page *page;
 232
 233         if (!pfn_valid(pfn))
 234                 return NULL;
 235
 236         page = pfn_to_page(pfn);
 237
 238         if (PageNosave(page))
 239                 return NULL;
 240         if (PageReserved(page) && pfn_is_nosave(pfn))
 241                 return NULL;
 242         if (PageNosaveFree(page))
 243                 return NULL;
 244
 245         return page;
 246 }
 247
 248 unsigned int count_data_pages(void)
 249 {
 250         struct zone *zone;
 251         unsigned long pfn, max_zone_pfn;
 252         unsigned int n = 0;
 253
 254         for_each_zone (zone) {
 255                 if (is_highmem(zone))
 256                         continue;
 257                 mark_free_pages(zone);
 258                 max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
 259                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
 260                         n += !!saveable_page(pfn);
 261         }
 262         return n;
 263 }
 264
 265 static inline void copy_data_page(long *dst, long *src)
 266 {
 267         int n;
 268
 269         /* copy_page and memcpy are not usable for copying task structs. */
 270         for (n = PAGE_SIZE / sizeof(long); n; n--)
 271                 *dst++ = *src++;
 272 }
 273
 274 static void copy_data_pages(struct pbe *pblist)
 275 {
 276         struct zone *zone;
 277         unsigned long pfn, max_zone_pfn;
 278         struct pbe *pbe;
 279
 280         pbe = pblist;
 281         for_each_zone (zone) {
 282                 if (is_highmem(zone))
 283                         continue;
 284                 mark_free_pages(zone);
 285                 max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
 286                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
 287                         struct page *page = saveable_page(pfn);
 288
 289                         if (page) {
 290                                 void *ptr = page_address(page);
 291
 292                                 BUG_ON(!pbe);
 293                                 copy_data_page((void *)pbe->address, ptr);
 294                                 pbe->orig_address = (unsigned long)ptr;
 295                                 pbe = pbe->next;
 296                         }
 297                 }
 298         }
 299         BUG_ON(pbe);
 300 }
 301
 302 /**
 303  *      free_pagedir - free pages allocated with alloc_pagedir()
 304  */
 305
 306 static void free_pagedir(struct pbe *pblist, int clear_nosave_free)
 307 {
 308         struct pbe *pbe;
 309
 310         while (pblist) {
 311                 pbe = (pblist + PB_PAGE_SKIP)->next;
 312                 free_image_page(pblist, clear_nosave_free);
 313                 pblist = pbe;
 314         }
 315 }
 316
 317 /**
 318  *      fill_pb_page - Create a list of PBEs on a given memory page
 319  */
 320
 321 static inline void fill_pb_page(struct pbe *pbpage, unsigned int n)
 322 {
 323         struct pbe *p;
 324
 325         p = pbpage;
 326         pbpage += n - 1;
 327         do
 328                 p->next = p + 1;
 329         while (++p < pbpage);
 330 }
 331
 332 /**
 333  *      create_pbe_list - Create a list of PBEs on top of a given chain
 334  *      of memory pages allocated with alloc_pagedir()
 335  *
 336  *      This function assumes that pages allocated by alloc_image_page() will
 337  *      always be zeroed.
 338  */
 339
 340 static inline void create_pbe_list(struct pbe *pblist, unsigned int nr_pages)
 341 {
 342         struct pbe *pbpage;
 343         unsigned int num = PBES_PER_PAGE;
 344
 345         for_each_pb_page (pbpage, pblist) {
 346                 if (num >= nr_pages)
 347                         break;
 348
 349                 fill_pb_page(pbpage, PBES_PER_PAGE);
 350                 num += PBES_PER_PAGE;
 351         }
 352         if (pbpage) {
 353                 num -= PBES_PER_PAGE;
 354                 fill_pb_page(pbpage, nr_pages - num);
 355         }
 356 }
 357
 358 /**
 359  *      alloc_pagedir - Allocate the page directory.
 360  *
 361  *      First, determine exactly how many pages we need and
 362  *      allocate them.
 363  *
 364  *      We arrange the pages in a chain: each page is an array of PBES_PER_PAGE
 365  *      struct pbe elements (pbes) and the last element in the page points
 366  *      to the next page.
 367  *
 368  *      On each page we set up a list of struct_pbe elements.
 369  */
 370
 371 static struct pbe *alloc_pagedir(unsigned int nr_pages, gfp_t gfp_mask,
 372                                  int safe_needed)
 373 {
 374         unsigned int num;
 375         struct pbe *pblist, *pbe;
 376
 377         if (!nr_pages)
 378                 return NULL;
 379
 380         pblist = alloc_image_page(gfp_mask, safe_needed);
 381         pbe = pblist;
 382         for (num = PBES_PER_PAGE; num < nr_pages; num += PBES_PER_PAGE) {
 383                 if (!pbe) {
 384                         free_pagedir(pblist, 1);
 385                         return NULL;
 386                 }
 387                 pbe += PB_PAGE_SKIP;
 388                 pbe->next = alloc_image_page(gfp_mask, safe_needed);
 389                 pbe = pbe->next;
 390         }
 391         create_pbe_list(pblist, nr_pages);
 392         return pblist;
 393 }
 394
 395 /**
 396  * Free pages we allocated for suspend. Suspend pages are alocated
 397  * before atomic copy, so we need to free them after resume.
 398  */
 399
 400 void swsusp_free(void)
 401 {
 402         struct zone *zone;
 403         unsigned long pfn, max_zone_pfn;
 404
 405         for_each_zone(zone) {
 406                 max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
 407                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
 408                         if (pfn_valid(pfn)) {
 409                                 struct page *page = pfn_to_page(pfn);
 410
 411                                 if (PageNosave(page) && PageNosaveFree(page)) {
 412                                         ClearPageNosave(page);
 413                                         ClearPageNosaveFree(page);
 414                                         free_page((long) page_address(page));
 415                                 }
 416                         }
 417         }
 418         nr_copy_pages = 0;
 419         nr_meta_pages = 0;
 420         restore_pblist = NULL;
 421         buffer = NULL;
 422 }
 423
 424
 425 /**
 426  *      enough_free_mem - Make sure we enough free memory to snapshot.
 427  *
 428  *      Returns TRUE or FALSE after checking the number of available
 429  *      free pages.
 430  */
 431
 432 static int enough_free_mem(unsigned int nr_pages)
 433 {
 434         struct zone *zone;
 435         unsigned int n = 0;
 436
 437         for_each_zone (zone)
 438                 if (!is_highmem(zone))
 439                         n += zone->free_pages;
 440         pr_debug("swsusp: available memory: %u pages\n", n);
 441         return n > (nr_pages + PAGES_FOR_IO +
 442                 (nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE);
 443 }
 444
 445 static int alloc_data_pages(struct pbe *pblist, gfp_t gfp_mask, int safe_needed)
 446 {
 447         struct pbe *p;
 448
 449         for_each_pbe (p, pblist) {
 450                 p->address = (unsigned long)alloc_image_page(gfp_mask, safe_needed);
 451                 if (!p->address)
 452                         return -ENOMEM;
 453         }
 454         return 0;
 455 }
 456
 457 static struct pbe *swsusp_alloc(unsigned int nr_pages)
 458 {
 459         struct pbe *pblist;
 460
 461         if (!(pblist = alloc_pagedir(nr_pages, GFP_ATOMIC | __GFP_COLD, 0))) {
 462                 printk(KERN_ERR "suspend: Allocating pagedir failed.\n");
 463                 return NULL;
 464         }
 465
 466         if (alloc_data_pages(pblist, GFP_ATOMIC | __GFP_COLD, 0)) {
 467                 printk(KERN_ERR "suspend: Allocating image pages failed.\n");
 468                 swsusp_free();
 469                 return NULL;
 470         }
 471
 472         return pblist;
 473 }
 474
 475 asmlinkage int swsusp_save(void)
 476 {
 477         unsigned int nr_pages;
 478
 479         pr_debug("swsusp: critical section: \n");
 480
 481         drain_local_pages();
 482         nr_pages = count_data_pages();
 483         printk("swsusp: Need to copy %u pages\n", nr_pages);
 484
 485         pr_debug("swsusp: pages needed: %u + %lu + %u, free: %u\n",
 486                  nr_pages,
 487                  (nr_pages + PBES_PER_PAGE - 1) / PBES_PER_PAGE,
 488                  PAGES_FOR_IO, nr_free_pages());
 489
 490         if (!enough_free_mem(nr_pages)) {
 491                 printk(KERN_ERR "swsusp: Not enough free memory\n");
 492                 return -ENOMEM;
 493         }
 494
 495         restore_pblist = swsusp_alloc(nr_pages);
 496         if (!restore_pblist)
 497                 return -ENOMEM;
 498
 499         /* During allocating of suspend pagedir, new cold pages may appear.
 500          * Kill them.
 501          */
 502         drain_local_pages();
 503         copy_data_pages(restore_pblist);
 504
 505         /*
 506          * End of critical section. From now on, we can write to memory,
 507          * but we should not touch disk. This specially means we must _not_
 508          * touch swap space! Except we must write out our image of course.
 509          */
 510
 511         nr_copy_pages = nr_pages;
 512         nr_meta_pages = (nr_pages * sizeof(long) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 513
 514         printk("swsusp: critical section/: done (%d pages copied)\n", nr_pages);
 515         return 0;
 516 }
 517
 518 static void init_header(struct swsusp_info *info)
 519 {
 520         memset(info, 0, sizeof(struct swsusp_info));
 521         info->version_code = LINUX_VERSION_CODE;
 522         info->num_physpages = num_physpages;
 523         memcpy(&info->uts, &system_utsname, sizeof(system_utsname));
 524         info->cpus = num_online_cpus();
 525         info->image_pages = nr_copy_pages;
 526         info->pages = nr_copy_pages + nr_meta_pages + 1;
 527         info->size = info->pages;
 528         info->size <<= PAGE_SHIFT;
 529 }
 530
 531 /**
 532  *      pack_orig_addresses - the .orig_address fields of the PBEs from the
 533  *      list starting at @pbe are stored in the array @buf[] (1 page)
 534  */
 535
 536 static inline struct pbe *pack_orig_addresses(unsigned long *buf, struct pbe *pbe)
 537 {
 538         int j;
 539
 540         for (j = 0; j < PAGE_SIZE / sizeof(long) && pbe; j++) {
 541                 buf[j] = pbe->orig_address;
 542                 pbe = pbe->next;
 543         }
 544         if (!pbe)
 545                 for (; j < PAGE_SIZE / sizeof(long); j++)
 546                         buf[j] = 0;
 547         return pbe;
 548 }
 549
 550 /**
 551  *      snapshot_read_next - used for reading the system memory snapshot.
 552  *
 553  *      On the first call to it @handle should point to a zeroed
 554  *      snapshot_handle structure.  The structure gets updated and a pointer
 555  *      to it should be passed to this function every next time.
 556  *
 557  *      The @count parameter should contain the number of bytes the caller
 558  *      wants to read from the snapshot.  It must not be zero.
 559  *
 560  *      On success the function returns a positive number.  Then, the caller
 561  *      is allowed to read up to the returned number of bytes from the memory
 562  *      location computed by the data_of() macro.  The number returned
 563  *      may be smaller than @count, but this only happens if the read would
 564  *      cross a page boundary otherwise.
 565  *
 566  *      The function returns 0 to indicate the end of data stream condition,
 567  *      and a negative number is returned on error.  In such cases the
 568  *      structure pointed to by @handle is not updated and should not be used
 569  *      any more.
 570  */
 571
 572 int snapshot_read_next(struct snapshot_handle *handle, size_t count)
 573 {
 574         if (handle->cur > nr_meta_pages + nr_copy_pages)
 575                 return 0;
 576         if (!buffer) {
 577                 /* This makes the buffer be freed by swsusp_free() */
 578                 buffer = alloc_image_page(GFP_ATOMIC, 0);
 579                 if (!buffer)
 580                         return -ENOMEM;
 581         }
 582         if (!handle->offset) {
 583                 init_header((struct swsusp_info *)buffer);
 584                 handle->buffer = buffer;
 585                 handle->pbe = restore_pblist;
 586         }
 587         if (handle->prev < handle->cur) {
 588                 if (handle->cur <= nr_meta_pages) {
 589                         handle->pbe = pack_orig_addresses(buffer, handle->pbe);
 590                         if (!handle->pbe)
 591                                 handle->pbe = restore_pblist;
 592                 } else {
 593                         handle->buffer = (void *)handle->pbe->address;
 594                         handle->pbe = handle->pbe->next;
 595                 }
 596                 handle->prev = handle->cur;
 597         }
 598         handle->buf_offset = handle->cur_offset;
 599         if (handle->cur_offset + count >= PAGE_SIZE) {
 600                 count = PAGE_SIZE - handle->cur_offset;
 601                 handle->cur_offset = 0;
 602                 handle->cur++;
 603         } else {
 604                 handle->cur_offset += count;
 605         }
 606         handle->offset += count;
 607         return count;
 608 }
 609
 610 /**
 611  *      mark_unsafe_pages - mark the pages that cannot be used for storing
 612  *      the image during resume, because they conflict with the pages that
 613  *      had been used before suspend
 614  */
 615
 616 static int mark_unsafe_pages(struct pbe *pblist)
 617 {
 618         struct zone *zone;
 619         unsigned long pfn, max_zone_pfn;
 620         struct pbe *p;
 621
 622         if (!pblist) /* a sanity check */
 623                 return -EINVAL;
 624
 625         /* Clear page flags */
 626         for_each_zone (zone) {
 627                 max_zone_pfn = zone->zone_start_pfn + zone->spanned_pages;
 628                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++)
 629                         if (pfn_valid(pfn))
 630                                 ClearPageNosaveFree(pfn_to_page(pfn));
 631         }
 632
 633         /* Mark orig addresses */
 634         for_each_pbe (p, pblist) {
 635                 if (virt_addr_valid(p->orig_address))
 636                         SetPageNosaveFree(virt_to_page(p->orig_address));
 637                 else
 638                         return -EFAULT;
 639         }
 640
 641         unsafe_pages = 0;
 642
 643         return 0;
 644 }
 645
 646 static void copy_page_backup_list(struct pbe *dst, struct pbe *src)
 647 {
 648         /* We assume both lists contain the same number of elements */
 649         while (src) {
 650                 dst->orig_address = src->orig_address;
 651                 dst = dst->next;
 652                 src = src->next;
 653         }
 654 }
 655
 656 static int check_header(struct swsusp_info *info)
 657 {
 658         char *reason = NULL;
 659
 660         if (info->version_code != LINUX_VERSION_CODE)
 661                 reason = "kernel version";
 662         if (info->num_physpages != num_physpages)
 663                 reason = "memory size";
 664         if (strcmp(info->uts.sysname,system_utsname.sysname))
 665                 reason = "system type";
 666         if (strcmp(info->uts.release,system_utsname.release))
 667                 reason = "kernel release";
 668         if (strcmp(info->uts.version,system_utsname.version))
 669                 reason = "version";
 670         if (strcmp(info->uts.machine,system_utsname.machine))
 671                 reason = "machine";
 672         if (reason) {
 673                 printk(KERN_ERR "swsusp: Resume mismatch: %s\n", reason);
 674                 return -EPERM;
 675         }
 676         return 0;
 677 }
 678
 679 /**
 680  *      load header - check the image header and copy data from it
 681  */
 682
 683 static int load_header(struct snapshot_handle *handle,
 684                               struct swsusp_info *info)
 685 {
 686         int error;
 687         struct pbe *pblist;
 688
 689         error = check_header(info);
 690         if (!error) {
 691                 pblist = alloc_pagedir(info->image_pages, GFP_ATOMIC, 0);
 692                 if (!pblist)
 693                         return -ENOMEM;
 694                 restore_pblist = pblist;
 695                 handle->pbe = pblist;
 696                 nr_copy_pages = info->image_pages;
 697                 nr_meta_pages = info->pages - info->image_pages - 1;
 698         }
 699         return error;
 700 }
 701
 702 /**
 703  *      unpack_orig_addresses - copy the elements of @buf[] (1 page) to
 704  *      the PBEs in the list starting at @pbe
 705  */
 706
 707 static inline struct pbe *unpack_orig_addresses(unsigned long *buf,
 708                                                 struct pbe *pbe)
 709 {
 710         int j;
 711
 712         for (j = 0; j < PAGE_SIZE / sizeof(long) && pbe; j++) {
 713                 pbe->orig_address = buf[j];
 714                 pbe = pbe->next;
 715         }
 716         return pbe;
 717 }
 718
 719 /**
 720  *      prepare_image - use metadata contained in the PBE list
 721  *      pointed to by restore_pblist to mark the pages that will
 722  *      be overwritten in the process of restoring the system
 723  *      memory state from the image ("unsafe" pages) and allocate
 724  *      memory for the image
 725  *
 726  *      The idea is to allocate the PBE list first and then
 727  *      allocate as many pages as it's needed for the image data,
 728  *      but not to assign these pages to the PBEs initially.
 729  *      Instead, we just mark them as allocated and create a list
 730  *      of "safe" which will be used later
 731  */
 732
 733 struct safe_page {
 734         struct safe_page *next;
 735         char padding[PAGE_SIZE - sizeof(void *)];
 736 };
 737
 738 static struct safe_page *safe_pages;
 739
 740 static int prepare_image(struct snapshot_handle *handle)
 741 {
 742         int error = 0;
 743         unsigned int nr_pages = nr_copy_pages;
 744         struct pbe *p, *pblist = NULL;
 745
 746         p = restore_pblist;
 747         error = mark_unsafe_pages(p);
 748         if (!error) {
 749                 pblist = alloc_pagedir(nr_pages, GFP_ATOMIC, 1);
 750                 if (pblist)
 751                         copy_page_backup_list(pblist, p);
 752                 free_pagedir(p, 0);
 753                 if (!pblist)
 754                         error = -ENOMEM;
 755         }
 756         safe_pages = NULL;
 757         if (!error && nr_pages > unsafe_pages) {
 758                 nr_pages -= unsafe_pages;
 759                 while (nr_pages--) {
 760                         struct safe_page *ptr;
 761
 762                         ptr = (struct safe_page *)get_zeroed_page(GFP_ATOMIC);
 763                         if (!ptr) {
 764                                 error = -ENOMEM;
 765                                 break;
 766                         }
 767                         if (!PageNosaveFree(virt_to_page(ptr))) {
 768                                 /* The page is "safe", add it to the list */
 769                                 ptr->next = safe_pages;
 770                                 safe_pages = ptr;
 771                         }
 772                         /* Mark the page as allocated */
 773                         SetPageNosave(virt_to_page(ptr));
 774                         SetPageNosaveFree(virt_to_page(ptr));
 775                 }
 776         }
 777         if (!error) {
 778                 restore_pblist = pblist;
 779         } else {
 780                 handle->pbe = NULL;
 781                 swsusp_free();
 782         }
 783         return error;
 784 }
 785
 786 static void *get_buffer(struct snapshot_handle *handle)
 787 {
 788         struct pbe *pbe = handle->pbe, *last = handle->last_pbe;
 789         struct page *page = virt_to_page(pbe->orig_address);
 790
 791         if (PageNosave(page) && PageNosaveFree(page)) {
 792                 /*
 793                  * We have allocated the "original" page frame and we can
 794                  * use it directly to store the read page
 795                  */
 796                 pbe->address = 0;
 797                 if (last && last->next)
 798                         last->next = NULL;
 799                 return (void *)pbe->orig_address;
 800         }
 801         /*
 802          * The "original" page frame has not been allocated and we have to
 803          * use a "safe" page frame to store the read page
 804          */
 805         pbe->address = (unsigned long)safe_pages;
 806         safe_pages = safe_pages->next;
 807         if (last)
 808                 last->next = pbe;
 809         handle->last_pbe = pbe;
 810         return (void *)pbe->address;
 811 }
 812
 813 /**
 814  *      snapshot_write_next - used for writing the system memory snapshot.
 815  *
 816  *      On the first call to it @handle should point to a zeroed
 817  *      snapshot_handle structure.  The structure gets updated and a pointer
 818  *      to it should be passed to this function every next time.
 819  *
 820  *      The @count parameter should contain the number of bytes the caller
 821  *      wants to write to the image.  It must not be zero.
 822  *
 823  *      On success the function returns a positive number.  Then, the caller
 824  *      is allowed to write up to the returned number of bytes to the memory
 825  *      location computed by the data_of() macro.  The number returned
 826  *      may be smaller than @count, but this only happens if the write would
 827  *      cross a page boundary otherwise.
 828  *
 829  *      The function returns 0 to indicate the "end of file" condition,
 830  *      and a negative number is returned on error.  In such cases the
 831  *      structure pointed to by @handle is not updated and should not be used
 832  *      any more.
 833  */
 834
 835 int snapshot_write_next(struct snapshot_handle *handle, size_t count)
 836 {
 837         int error = 0;
 838
 839         if (handle->prev && handle->cur > nr_meta_pages + nr_copy_pages)
 840                 return 0;
 841         if (!buffer) {
 842                 /* This makes the buffer be freed by swsusp_free() */
 843                 buffer = alloc_image_page(GFP_ATOMIC, 0);
 844                 if (!buffer)
 845                         return -ENOMEM;
 846         }
 847         if (!handle->offset)
 848                 handle->buffer = buffer;
 849         handle->sync_read = 1;
 850         if (handle->prev < handle->cur) {
 851                 if (!handle->prev) {
 852                         error = load_header(handle,
 853                                         (struct swsusp_info *)buffer);
 854                         if (error)
 855                                 return error;
 856                 } else if (handle->prev <= nr_meta_pages) {
 857                         handle->pbe = unpack_orig_addresses(buffer,
 858                                                         handle->pbe);
 859                         if (!handle->pbe) {
 860                                 error = prepare_image(handle);
 861                                 if (error)
 862                                         return error;
 863                                 handle->pbe = restore_pblist;
 864                                 handle->last_pbe = NULL;
 865                                 handle->buffer = get_buffer(handle);
 866                                 handle->sync_read = 0;
 867                         }
 868                 } else {
 869                         handle->pbe = handle->pbe->next;
 870                         handle->buffer = get_buffer(handle);
 871                         handle->sync_read = 0;
 872                 }
 873                 handle->prev = handle->cur;
 874         }
 875         handle->buf_offset = handle->cur_offset;
 876         if (handle->cur_offset + count >= PAGE_SIZE) {
 877                 count = PAGE_SIZE - handle->cur_offset;
 878                 handle->cur_offset = 0;
 879                 handle->cur++;
 880         } else {
 881                 handle->cur_offset += count;
 882         }
 883         handle->offset += count;
 884         return count;
 885 }
 886
 887 int snapshot_image_loaded(struct snapshot_handle *handle)
 888 {
 889         return !(!handle->pbe || handle->pbe->next || !nr_copy_pages ||
 890                 handle->cur <= nr_meta_pages + nr_copy_pages);
 891 }