mm/swapfile.c

   1 /*
   2  *  linux/mm/swapfile.c
   3  *
   4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   5  *  Swap reorganised 29.12.95, Stephen Tweedie
   6  */
   7
   8 #include <linux/mm.h>
   9 #include <linux/hugetlb.h>
  10 #include <linux/mman.h>
  11 #include <linux/slab.h>
  12 #include <linux/kernel_stat.h>
  13 #include <linux/swap.h>
  14 #include <linux/vmalloc.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/namei.h>
  17 #include <linux/shm.h>
  18 #include <linux/blkdev.h>
  19 #include <linux/writeback.h>
  20 #include <linux/proc_fs.h>
  21 #include <linux/seq_file.h>
  22 #include <linux/init.h>
  23 #include <linux/module.h>
  24 #include <linux/rmap.h>
  25 #include <linux/security.h>
  26 #include <linux/backing-dev.h>
  27 #include <linux/mutex.h>
  28 #include <linux/capability.h>
  29 #include <linux/syscalls.h>
  30 #include <linux/memcontrol.h>
  31
  32 #include <asm/pgtable.h>
  33 #include <asm/tlbflush.h>
  34 #include <linux/swapops.h>
  35
  36 static DEFINE_SPINLOCK(swap_lock);
  37 static unsigned int nr_swapfiles;
  38 long total_swap_pages;
  39 static int swap_overflow;
  40 static int least_priority;
  41
  42 static const char Bad_file[] = "Bad swap file entry ";
  43 static const char Unused_file[] = "Unused swap file entry ";
  44 static const char Bad_offset[] = "Bad swap offset entry ";
  45 static const char Unused_offset[] = "Unused swap offset entry ";
  46
  47 static struct swap_list_t swap_list = {-1, -1};
  48
  49 static struct swap_info_struct swap_info[MAX_SWAPFILES];
  50
  51 static DEFINE_MUTEX(swapon_mutex);
  52
  53 /*
  54  * We need this because the bdev->unplug_fn can sleep and we cannot
  55  * hold swap_lock while calling the unplug_fn. And swap_lock
  56  * cannot be turned into a mutex.
  57  */
  58 static DECLARE_RWSEM(swap_unplug_sem);
  59
  60 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
  61 {
  62         swp_entry_t entry;
  63
  64         down_read(&swap_unplug_sem);
  65         entry.val = page_private(page);
  66         if (PageSwapCache(page)) {
  67                 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
  68                 struct backing_dev_info *bdi;
  69
  70                 /*
  71                  * If the page is removed from swapcache from under us (with a
  72                  * racy try_to_unuse/swapoff) we need an additional reference
  73                  * count to avoid reading garbage from page_private(page) above.
  74                  * If the WARN_ON triggers during a swapoff it maybe the race
  75                  * condition and it's harmless. However if it triggers without
  76                  * swapoff it signals a problem.
  77                  */
  78                 WARN_ON(page_count(page) <= 1);
  79
  80                 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
  81                 blk_run_backing_dev(bdi, page);
  82         }
  83         up_read(&swap_unplug_sem);
  84 }
  85
  86 #define SWAPFILE_CLUSTER        256
  87 #define LATENCY_LIMIT           256
  88
  89 static inline unsigned long scan_swap_map(struct swap_info_struct *si)
  90 {
  91         unsigned long offset, last_in_cluster;
  92         int latency_ration = LATENCY_LIMIT;
  93
  94         /*
  95          * We try to cluster swap pages by allocating them sequentially
  96          * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
  97          * way, however, we resort to first-free allocation, starting
  98          * a new cluster.  This prevents us from scattering swap pages
  99          * all over the entire swap partition, so that we reduce
 100          * overall disk seek times between swap pages.  -- sct
 101          * But we do now try to find an empty cluster.  -Andrea
 102          */
 103
 104         si->flags += SWP_SCANNING;
 105         if (unlikely(!si->cluster_nr)) {
 106                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
 107                 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
 108                         goto lowest;
 109                 spin_unlock(&swap_lock);
 110
 111                 offset = si->lowest_bit;
 112                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
 113
 114                 /* Locate the first empty (unaligned) cluster */
 115                 for (; last_in_cluster <= si->highest_bit; offset++) {
 116                         if (si->swap_map[offset])
 117                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
 118                         else if (offset == last_in_cluster) {
 119                                 spin_lock(&swap_lock);
 120                                 si->cluster_next = offset-SWAPFILE_CLUSTER+1;
 121                                 goto cluster;
 122                         }
 123                         if (unlikely(--latency_ration < 0)) {
 124                                 cond_resched();
 125                                 latency_ration = LATENCY_LIMIT;
 126                         }
 127                 }
 128                 spin_lock(&swap_lock);
 129                 goto lowest;
 130         }
 131
 132         si->cluster_nr--;
 133 cluster:
 134         offset = si->cluster_next;
 135         if (offset > si->highest_bit)
 136 lowest:         offset = si->lowest_bit;
 137 checks: if (!(si->flags & SWP_WRITEOK))
 138                 goto no_page;
 139         if (!si->highest_bit)
 140                 goto no_page;
 141         if (!si->swap_map[offset]) {
 142                 if (offset == si->lowest_bit)
 143                         si->lowest_bit++;
 144                 if (offset == si->highest_bit)
 145                         si->highest_bit--;
 146                 si->inuse_pages++;
 147                 if (si->inuse_pages == si->pages) {
 148                         si->lowest_bit = si->max;
 149                         si->highest_bit = 0;
 150                 }
 151                 si->swap_map[offset] = 1;
 152                 si->cluster_next = offset + 1;
 153                 si->flags -= SWP_SCANNING;
 154                 return offset;
 155         }
 156
 157         spin_unlock(&swap_lock);
 158         while (++offset <= si->highest_bit) {
 159                 if (!si->swap_map[offset]) {
 160                         spin_lock(&swap_lock);
 161                         goto checks;
 162                 }
 163                 if (unlikely(--latency_ration < 0)) {
 164                         cond_resched();
 165                         latency_ration = LATENCY_LIMIT;
 166                 }
 167         }
 168         spin_lock(&swap_lock);
 169         goto lowest;
 170
 171 no_page:
 172         si->flags -= SWP_SCANNING;
 173         return 0;
 174 }
 175
 176 swp_entry_t get_swap_page(void)
 177 {
 178         struct swap_info_struct *si;
 179         pgoff_t offset;
 180         int type, next;
 181         int wrapped = 0;
 182
 183         spin_lock(&swap_lock);
 184         if (nr_swap_pages <= 0)
 185                 goto noswap;
 186         nr_swap_pages--;
 187
 188         for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
 189                 si = swap_info + type;
 190                 next = si->next;
 191                 if (next < 0 ||
 192                     (!wrapped && si->prio != swap_info[next].prio)) {
 193                         next = swap_list.head;
 194                         wrapped++;
 195                 }
 196
 197                 if (!si->highest_bit)
 198                         continue;
 199                 if (!(si->flags & SWP_WRITEOK))
 200                         continue;
 201
 202                 swap_list.next = next;
 203                 offset = scan_swap_map(si);
 204                 if (offset) {
 205                         spin_unlock(&swap_lock);
 206                         return swp_entry(type, offset);
 207                 }
 208                 next = swap_list.next;
 209         }
 210
 211         nr_swap_pages++;
 212 noswap:
 213         spin_unlock(&swap_lock);
 214         return (swp_entry_t) {0};
 215 }
 216
 217 swp_entry_t get_swap_page_of_type(int type)
 218 {
 219         struct swap_info_struct *si;
 220         pgoff_t offset;
 221
 222         spin_lock(&swap_lock);
 223         si = swap_info + type;
 224         if (si->flags & SWP_WRITEOK) {
 225                 nr_swap_pages--;
 226                 offset = scan_swap_map(si);
 227                 if (offset) {
 228                         spin_unlock(&swap_lock);
 229                         return swp_entry(type, offset);
 230                 }
 231                 nr_swap_pages++;
 232         }
 233         spin_unlock(&swap_lock);
 234         return (swp_entry_t) {0};
 235 }
 236
 237 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
 238 {
 239         struct swap_info_struct * p;
 240         unsigned long offset, type;
 241
 242         if (!entry.val)
 243                 goto out;
 244         type = swp_type(entry);
 245         if (type >= nr_swapfiles)
 246                 goto bad_nofile;
 247         p = & swap_info[type];
 248         if (!(p->flags & SWP_USED))
 249                 goto bad_device;
 250         offset = swp_offset(entry);
 251         if (offset >= p->max)
 252                 goto bad_offset;
 253         if (!p->swap_map[offset])
 254                 goto bad_free;
 255         spin_lock(&swap_lock);
 256         return p;
 257
 258 bad_free:
 259         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
 260         goto out;
 261 bad_offset:
 262         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
 263         goto out;
 264 bad_device:
 265         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
 266         goto out;
 267 bad_nofile:
 268         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
 269 out:
 270         return NULL;
 271 }
 272
 273 static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
 274 {
 275         int count = p->swap_map[offset];
 276
 277         if (count < SWAP_MAP_MAX) {
 278                 count--;
 279                 p->swap_map[offset] = count;
 280                 if (!count) {
 281                         if (offset < p->lowest_bit)
 282                                 p->lowest_bit = offset;
 283                         if (offset > p->highest_bit)
 284                                 p->highest_bit = offset;
 285                         if (p->prio > swap_info[swap_list.next].prio)
 286                                 swap_list.next = p - swap_info;
 287                         nr_swap_pages++;
 288                         p->inuse_pages--;
 289                 }
 290         }
 291         return count;
 292 }
 293
 294 /*
 295  * Caller has made sure that the swapdevice corresponding to entry
 296  * is still around or has not been recycled.
 297  */
 298 void swap_free(swp_entry_t entry)
 299 {
 300         struct swap_info_struct * p;
 301
 302         p = swap_info_get(entry);
 303         if (p) {
 304                 swap_entry_free(p, swp_offset(entry));
 305                 spin_unlock(&swap_lock);
 306         }
 307 }
 308
 309 /*
 310  * How many references to page are currently swapped out?
 311  */
 312 static inline int page_swapcount(struct page *page)
 313 {
 314         int count = 0;
 315         struct swap_info_struct *p;
 316         swp_entry_t entry;
 317
 318         entry.val = page_private(page);
 319         p = swap_info_get(entry);
 320         if (p) {
 321                 /* Subtract the 1 for the swap cache itself */
 322                 count = p->swap_map[swp_offset(entry)] - 1;
 323                 spin_unlock(&swap_lock);
 324         }
 325         return count;
 326 }
 327
 328 /*
 329  * We can use this swap cache entry directly
 330  * if there are no other references to it.
 331  */
 332 int can_share_swap_page(struct page *page)
 333 {
 334         int count;
 335
 336         BUG_ON(!PageLocked(page));
 337         count = page_mapcount(page);
 338         if (count <= 1 && PageSwapCache(page))
 339                 count += page_swapcount(page);
 340         return count == 1;
 341 }
 342
 343 /*
 344  * Work out if there are any other processes sharing this
 345  * swap cache page. Free it if you can. Return success.
 346  */
 347 static int remove_exclusive_swap_page_count(struct page *page, int count)
 348 {
 349         int retval;
 350         struct swap_info_struct * p;
 351         swp_entry_t entry;
 352
 353         BUG_ON(PagePrivate(page));
 354         BUG_ON(!PageLocked(page));
 355
 356         if (!PageSwapCache(page))
 357                 return 0;
 358         if (PageWriteback(page))
 359                 return 0;
 360         if (page_count(page) != count) /* us + cache + ptes */
 361                 return 0;
 362
 363         entry.val = page_private(page);
 364         p = swap_info_get(entry);
 365         if (!p)
 366                 return 0;
 367
 368         /* Is the only swap cache user the cache itself? */
 369         retval = 0;
 370         if (p->swap_map[swp_offset(entry)] == 1) {
 371                 /* Recheck the page count with the swapcache lock held.. */
 372                 spin_lock_irq(&swapper_space.tree_lock);
 373                 if ((page_count(page) == count) && !PageWriteback(page)) {
 374                         __delete_from_swap_cache(page);
 375                         SetPageDirty(page);
 376                         retval = 1;
 377                 }
 378                 spin_unlock_irq(&swapper_space.tree_lock);
 379         }
 380         spin_unlock(&swap_lock);
 381
 382         if (retval) {
 383                 swap_free(entry);
 384                 page_cache_release(page);
 385         }
 386
 387         return retval;
 388 }
 389
 390 /*
 391  * Most of the time the page should have two references: one for the
 392  * process and one for the swap cache.
 393  */
 394 int remove_exclusive_swap_page(struct page *page)
 395 {
 396         return remove_exclusive_swap_page_count(page, 2);
 397 }
 398
 399 /*
 400  * The pageout code holds an extra reference to the page.  That raises
 401  * the reference count to test for to 2 for a page that is only in the
 402  * swap cache plus 1 for each process that maps the page.
 403  */
 404 int remove_exclusive_swap_page_ref(struct page *page)
 405 {
 406         return remove_exclusive_swap_page_count(page, 2 + page_mapcount(page));
 407 }
 408
 409 /*
 410  * Free the swap entry like above, but also try to
 411  * free the page cache entry if it is the last user.
 412  */
 413 void free_swap_and_cache(swp_entry_t entry)
 414 {
 415         struct swap_info_struct * p;
 416         struct page *page = NULL;
 417
 418         if (is_migration_entry(entry))
 419                 return;
 420
 421         p = swap_info_get(entry);
 422         if (p) {
 423                 if (swap_entry_free(p, swp_offset(entry)) == 1) {
 424                         page = find_get_page(&swapper_space, entry.val);
 425                         if (page && !trylock_page(page)) {
 426                                 page_cache_release(page);
 427                                 page = NULL;
 428                         }
 429                 }
 430                 spin_unlock(&swap_lock);
 431         }
 432         if (page) {
 433                 int one_user;
 434
 435                 BUG_ON(PagePrivate(page));
 436                 one_user = (page_count(page) == 2);
 437                 /* Only cache user (+us), or swap space full? Free it! */
 438                 /* Also recheck PageSwapCache after page is locked (above) */
 439                 if (PageSwapCache(page) && !PageWriteback(page) &&
 440                                         (one_user || vm_swap_full())) {
 441                         delete_from_swap_cache(page);
 442                         SetPageDirty(page);
 443                 }
 444                 unlock_page(page);
 445                 page_cache_release(page);
 446         }
 447 }
 448
 449 #ifdef CONFIG_HIBERNATION
 450 /*
 451  * Find the swap type that corresponds to given device (if any).
 452  *
 453  * @offset - number of the PAGE_SIZE-sized block of the device, starting
 454  * from 0, in which the swap header is expected to be located.
 455  *
 456  * This is needed for the suspend to disk (aka swsusp).
 457  */
 458 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
 459 {
 460         struct block_device *bdev = NULL;
 461         int i;
 462
 463         if (device)
 464                 bdev = bdget(device);
 465
 466         spin_lock(&swap_lock);
 467         for (i = 0; i < nr_swapfiles; i++) {
 468                 struct swap_info_struct *sis = swap_info + i;
 469
 470                 if (!(sis->flags & SWP_WRITEOK))
 471                         continue;
 472
 473                 if (!bdev) {
 474                         if (bdev_p)
 475                                 *bdev_p = sis->bdev;
 476
 477                         spin_unlock(&swap_lock);
 478                         return i;
 479                 }
 480                 if (bdev == sis->bdev) {
 481                         struct swap_extent *se;
 482
 483                         se = list_entry(sis->extent_list.next,
 484                                         struct swap_extent, list);
 485                         if (se->start_block == offset) {
 486                                 if (bdev_p)
 487                                         *bdev_p = sis->bdev;
 488
 489                                 spin_unlock(&swap_lock);
 490                                 bdput(bdev);
 491                                 return i;
 492                         }
 493                 }
 494         }
 495         spin_unlock(&swap_lock);
 496         if (bdev)
 497                 bdput(bdev);
 498
 499         return -ENODEV;
 500 }
 501
 502 /*
 503  * Return either the total number of swap pages of given type, or the number
 504  * of free pages of that type (depending on @free)
 505  *
 506  * This is needed for software suspend
 507  */
 508 unsigned int count_swap_pages(int type, int free)
 509 {
 510         unsigned int n = 0;
 511
 512         if (type < nr_swapfiles) {
 513                 spin_lock(&swap_lock);
 514                 if (swap_info[type].flags & SWP_WRITEOK) {
 515                         n = swap_info[type].pages;
 516                         if (free)
 517                                 n -= swap_info[type].inuse_pages;
 518                 }
 519                 spin_unlock(&swap_lock);
 520         }
 521         return n;
 522 }
 523 #endif
 524
 525 /*
 526  * No need to decide whether this PTE shares the swap entry with others,
 527  * just let do_wp_page work it out if a write is requested later - to
 528  * force COW, vm_page_prot omits write permission from any private vma.
 529  */
 530 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
 531                 unsigned long addr, swp_entry_t entry, struct page *page)
 532 {
 533         spinlock_t *ptl;
 534         pte_t *pte;
 535         int ret = 1;
 536
 537         if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
 538                 ret = -ENOMEM;
 539
 540         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 541         if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
 542                 if (ret > 0)
 543                         mem_cgroup_uncharge_page(page);
 544                 ret = 0;
 545                 goto out;
 546         }
 547
 548         inc_mm_counter(vma->vm_mm, anon_rss);
 549         get_page(page);
 550         set_pte_at(vma->vm_mm, addr, pte,
 551                    pte_mkold(mk_pte(page, vma->vm_page_prot)));
 552         page_add_anon_rmap(page, vma, addr);
 553         swap_free(entry);
 554         /*
 555          * Move the page to the active list so it is not
 556          * immediately swapped out again after swapon.
 557          */
 558         activate_page(page);
 559 out:
 560         pte_unmap_unlock(pte, ptl);
 561         return ret;
 562 }
 563
 564 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 565                                 unsigned long addr, unsigned long end,
 566                                 swp_entry_t entry, struct page *page)
 567 {
 568         pte_t swp_pte = swp_entry_to_pte(entry);
 569         pte_t *pte;
 570         int ret = 0;
 571
 572         /*
 573          * We don't actually need pte lock while scanning for swp_pte: since
 574          * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
 575          * page table while we're scanning; though it could get zapped, and on
 576          * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
 577          * of unmatched parts which look like swp_pte, so unuse_pte must
 578          * recheck under pte lock.  Scanning without pte lock lets it be
 579          * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
 580          */
 581         pte = pte_offset_map(pmd, addr);
 582         do {
 583                 /*
 584                  * swapoff spends a _lot_ of time in this loop!
 585                  * Test inline before going to call unuse_pte.
 586                  */
 587                 if (unlikely(pte_same(*pte, swp_pte))) {
 588                         pte_unmap(pte);
 589                         ret = unuse_pte(vma, pmd, addr, entry, page);
 590                         if (ret)
 591                                 goto out;
 592                         pte = pte_offset_map(pmd, addr);
 593                 }
 594         } while (pte++, addr += PAGE_SIZE, addr != end);
 595         pte_unmap(pte - 1);
 596 out:
 597         return ret;
 598 }
 599
 600 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
 601                                 unsigned long addr, unsigned long end,
 602                                 swp_entry_t entry, struct page *page)
 603 {
 604         pmd_t *pmd;
 605         unsigned long next;
 606         int ret;
 607
 608         pmd = pmd_offset(pud, addr);
 609         do {
 610                 next = pmd_addr_end(addr, end);
 611                 if (pmd_none_or_clear_bad(pmd))
 612                         continue;
 613                 ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
 614                 if (ret)
 615                         return ret;
 616         } while (pmd++, addr = next, addr != end);
 617         return 0;
 618 }
 619
 620 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
 621                                 unsigned long addr, unsigned long end,
 622                                 swp_entry_t entry, struct page *page)
 623 {
 624         pud_t *pud;
 625         unsigned long next;
 626         int ret;
 627
 628         pud = pud_offset(pgd, addr);
 629         do {
 630                 next = pud_addr_end(addr, end);
 631                 if (pud_none_or_clear_bad(pud))
 632                         continue;
 633                 ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
 634                 if (ret)
 635                         return ret;
 636         } while (pud++, addr = next, addr != end);
 637         return 0;
 638 }
 639
 640 static int unuse_vma(struct vm_area_struct *vma,
 641                                 swp_entry_t entry, struct page *page)
 642 {
 643         pgd_t *pgd;
 644         unsigned long addr, end, next;
 645         int ret;
 646
 647         if (page->mapping) {
 648                 addr = page_address_in_vma(page, vma);
 649                 if (addr == -EFAULT)
 650                         return 0;
 651                 else
 652                         end = addr + PAGE_SIZE;
 653         } else {
 654                 addr = vma->vm_start;
 655                 end = vma->vm_end;
 656         }
 657
 658         pgd = pgd_offset(vma->vm_mm, addr);
 659         do {
 660                 next = pgd_addr_end(addr, end);
 661                 if (pgd_none_or_clear_bad(pgd))
 662                         continue;
 663                 ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
 664                 if (ret)
 665                         return ret;
 666         } while (pgd++, addr = next, addr != end);
 667         return 0;
 668 }
 669
 670 static int unuse_mm(struct mm_struct *mm,
 671                                 swp_entry_t entry, struct page *page)
 672 {
 673         struct vm_area_struct *vma;
 674         int ret = 0;
 675
 676         if (!down_read_trylock(&mm->mmap_sem)) {
 677                 /*
 678                  * Activate page so shrink_inactive_list is unlikely to unmap
 679                  * its ptes while lock is dropped, so swapoff can make progress.
 680                  */
 681                 activate_page(page);
 682                 unlock_page(page);
 683                 down_read(&mm->mmap_sem);
 684                 lock_page(page);
 685         }
 686         for (vma = mm->mmap; vma; vma = vma->vm_next) {
 687                 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
 688                         break;
 689         }
 690         up_read(&mm->mmap_sem);
 691         return (ret < 0)? ret: 0;
 692 }
 693
 694 /*
 695  * Scan swap_map from current position to next entry still in use.
 696  * Recycle to start on reaching the end, returning 0 when empty.
 697  */
 698 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
 699                                         unsigned int prev)
 700 {
 701         unsigned int max = si->max;
 702         unsigned int i = prev;
 703         int count;
 704
 705         /*
 706          * No need for swap_lock here: we're just looking
 707          * for whether an entry is in use, not modifying it; false
 708          * hits are okay, and sys_swapoff() has already prevented new
 709          * allocations from this area (while holding swap_lock).
 710          */
 711         for (;;) {
 712                 if (++i >= max) {
 713                         if (!prev) {
 714                                 i = 0;
 715                                 break;
 716                         }
 717                         /*
 718                          * No entries in use at top of swap_map,
 719                          * loop back to start and recheck there.
 720                          */
 721                         max = prev + 1;
 722                         prev = 0;
 723                         i = 1;
 724                 }
 725                 count = si->swap_map[i];
 726                 if (count && count != SWAP_MAP_BAD)
 727                         break;
 728         }
 729         return i;
 730 }
 731
 732 /*
 733  * We completely avoid races by reading each swap page in advance,
 734  * and then search for the process using it.  All the necessary
 735  * page table adjustments can then be made atomically.
 736  */
 737 static int try_to_unuse(unsigned int type)
 738 {
 739         struct swap_info_struct * si = &swap_info[type];
 740         struct mm_struct *start_mm;
 741         unsigned short *swap_map;
 742         unsigned short swcount;
 743         struct page *page;
 744         swp_entry_t entry;
 745         unsigned int i = 0;
 746         int retval = 0;
 747         int reset_overflow = 0;
 748         int shmem;
 749
 750         /*
 751          * When searching mms for an entry, a good strategy is to
 752          * start at the first mm we freed the previous entry from
 753          * (though actually we don't notice whether we or coincidence
 754          * freed the entry).  Initialize this start_mm with a hold.
 755          *
 756          * A simpler strategy would be to start at the last mm we
 757          * freed the previous entry from; but that would take less
 758          * advantage of mmlist ordering, which clusters forked mms
 759          * together, child after parent.  If we race with dup_mmap(), we
 760          * prefer to resolve parent before child, lest we miss entries
 761          * duplicated after we scanned child: using last mm would invert
 762          * that.  Though it's only a serious concern when an overflowed
 763          * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
 764          */
 765         start_mm = &init_mm;
 766         atomic_inc(&init_mm.mm_users);
 767
 768         /*
 769          * Keep on scanning until all entries have gone.  Usually,
 770          * one pass through swap_map is enough, but not necessarily:
 771          * there are races when an instance of an entry might be missed.
 772          */
 773         while ((i = find_next_to_unuse(si, i)) != 0) {
 774                 if (signal_pending(current)) {
 775                         retval = -EINTR;
 776                         break;
 777                 }
 778
 779                 /*
 780                  * Get a page for the entry, using the existing swap
 781                  * cache page if there is one.  Otherwise, get a clean
 782                  * page and read the swap into it.
 783                  */
 784                 swap_map = &si->swap_map[i];
 785                 entry = swp_entry(type, i);
 786                 page = read_swap_cache_async(entry,
 787                                         GFP_HIGHUSER_MOVABLE, NULL, 0);
 788                 if (!page) {
 789                         /*
 790                          * Either swap_duplicate() failed because entry
 791                          * has been freed independently, and will not be
 792                          * reused since sys_swapoff() already disabled
 793                          * allocation from here, or alloc_page() failed.
 794                          */
 795                         if (!*swap_map)
 796                                 continue;
 797                         retval = -ENOMEM;
 798                         break;
 799                 }
 800
 801                 /*
 802                  * Don't hold on to start_mm if it looks like exiting.
 803                  */
 804                 if (atomic_read(&start_mm->mm_users) == 1) {
 805                         mmput(start_mm);
 806                         start_mm = &init_mm;
 807                         atomic_inc(&init_mm.mm_users);
 808                 }
 809
 810                 /*
 811                  * Wait for and lock page.  When do_swap_page races with
 812                  * try_to_unuse, do_swap_page can handle the fault much
 813                  * faster than try_to_unuse can locate the entry.  This
 814                  * apparently redundant "wait_on_page_locked" lets try_to_unuse
 815                  * defer to do_swap_page in such a case - in some tests,
 816                  * do_swap_page and try_to_unuse repeatedly compete.
 817                  */
 818                 wait_on_page_locked(page);
 819                 wait_on_page_writeback(page);
 820                 lock_page(page);
 821                 wait_on_page_writeback(page);
 822
 823                 /*
 824                  * Remove all references to entry.
 825                  * Whenever we reach init_mm, there's no address space
 826                  * to search, but use it as a reminder to search shmem.
 827                  */
 828                 shmem = 0;
 829                 swcount = *swap_map;
 830                 if (swcount > 1) {
 831                         if (start_mm == &init_mm)
 832                                 shmem = shmem_unuse(entry, page);
 833                         else
 834                                 retval = unuse_mm(start_mm, entry, page);
 835                 }
 836                 if (*swap_map > 1) {
 837                         int set_start_mm = (*swap_map >= swcount);
 838                         struct list_head *p = &start_mm->mmlist;
 839                         struct mm_struct *new_start_mm = start_mm;
 840                         struct mm_struct *prev_mm = start_mm;
 841                         struct mm_struct *mm;
 842
 843                         atomic_inc(&new_start_mm->mm_users);
 844                         atomic_inc(&prev_mm->mm_users);
 845                         spin_lock(&mmlist_lock);
 846                         while (*swap_map > 1 && !retval && !shmem &&
 847                                         (p = p->next) != &start_mm->mmlist) {
 848                                 mm = list_entry(p, struct mm_struct, mmlist);
 849                                 if (!atomic_inc_not_zero(&mm->mm_users))
 850                                         continue;
 851                                 spin_unlock(&mmlist_lock);
 852                                 mmput(prev_mm);
 853                                 prev_mm = mm;
 854
 855                                 cond_resched();
 856
 857                                 swcount = *swap_map;
 858                                 if (swcount <= 1)
 859                                         ;
 860                                 else if (mm == &init_mm) {
 861                                         set_start_mm = 1;
 862                                         shmem = shmem_unuse(entry, page);
 863                                 } else
 864                                         retval = unuse_mm(mm, entry, page);
 865                                 if (set_start_mm && *swap_map < swcount) {
 866                                         mmput(new_start_mm);
 867                                         atomic_inc(&mm->mm_users);
 868                                         new_start_mm = mm;
 869                                         set_start_mm = 0;
 870                                 }
 871                                 spin_lock(&mmlist_lock);
 872                         }
 873                         spin_unlock(&mmlist_lock);
 874                         mmput(prev_mm);
 875                         mmput(start_mm);
 876                         start_mm = new_start_mm;
 877                 }
 878                 if (shmem) {
 879                         /* page has already been unlocked and released */
 880                         if (shmem > 0)
 881                                 continue;
 882                         retval = shmem;
 883                         break;
 884                 }
 885                 if (retval) {
 886                         unlock_page(page);
 887                         page_cache_release(page);
 888                         break;
 889                 }
 890
 891                 /*
 892                  * How could swap count reach 0x7fff when the maximum
 893                  * pid is 0x7fff, and there's no way to repeat a swap
 894                  * page within an mm (except in shmem, where it's the
 895                  * shared object which takes the reference count)?
 896                  * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
 897                  *
 898                  * If that's wrong, then we should worry more about
 899                  * exit_mmap() and do_munmap() cases described above:
 900                  * we might be resetting SWAP_MAP_MAX too early here.
 901                  * We know "Undead"s can happen, they're okay, so don't
 902                  * report them; but do report if we reset SWAP_MAP_MAX.
 903                  */
 904                 if (*swap_map == SWAP_MAP_MAX) {
 905                         spin_lock(&swap_lock);
 906                         *swap_map = 1;
 907                         spin_unlock(&swap_lock);
 908                         reset_overflow = 1;
 909                 }
 910
 911                 /*
 912                  * If a reference remains (rare), we would like to leave
 913                  * the page in the swap cache; but try_to_unmap could
 914                  * then re-duplicate the entry once we drop page lock,
 915                  * so we might loop indefinitely; also, that page could
 916                  * not be swapped out to other storage meanwhile.  So:
 917                  * delete from cache even if there's another reference,
 918                  * after ensuring that the data has been saved to disk -
 919                  * since if the reference remains (rarer), it will be
 920                  * read from disk into another page.  Splitting into two
 921                  * pages would be incorrect if swap supported "shared
 922                  * private" pages, but they are handled by tmpfs files.
 923                  */
 924                 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
 925                         struct writeback_control wbc = {
 926                                 .sync_mode = WB_SYNC_NONE,
 927                         };
 928
 929                         swap_writepage(page, &wbc);
 930                         lock_page(page);
 931                         wait_on_page_writeback(page);
 932                 }
 933                 if (PageSwapCache(page))
 934                         delete_from_swap_cache(page);
 935
 936                 /*
 937                  * So we could skip searching mms once swap count went
 938                  * to 1, we did not mark any present ptes as dirty: must
 939                  * mark page dirty so shrink_page_list will preserve it.
 940                  */
 941                 SetPageDirty(page);
 942                 unlock_page(page);
 943                 page_cache_release(page);
 944
 945                 /*
 946                  * Make sure that we aren't completely killing
 947                  * interactive performance.
 948                  */
 949                 cond_resched();
 950         }
 951
 952         mmput(start_mm);
 953         if (reset_overflow) {
 954                 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
 955                 swap_overflow = 0;
 956         }
 957         return retval;
 958 }
 959
 960 /*
 961  * After a successful try_to_unuse, if no swap is now in use, we know
 962  * we can empty the mmlist.  swap_lock must be held on entry and exit.
 963  * Note that mmlist_lock nests inside swap_lock, and an mm must be
 964  * added to the mmlist just after page_duplicate - before would be racy.
 965  */
 966 static void drain_mmlist(void)
 967 {
 968         struct list_head *p, *next;
 969         unsigned int i;
 970
 971         for (i = 0; i < nr_swapfiles; i++)
 972                 if (swap_info[i].inuse_pages)
 973                         return;
 974         spin_lock(&mmlist_lock);
 975         list_for_each_safe(p, next, &init_mm.mmlist)
 976                 list_del_init(p);
 977         spin_unlock(&mmlist_lock);
 978 }
 979
 980 /*
 981  * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
 982  * corresponds to page offset `offset'.
 983  */
 984 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
 985 {
 986         struct swap_extent *se = sis->curr_swap_extent;
 987         struct swap_extent *start_se = se;
 988
 989         for ( ; ; ) {
 990                 struct list_head *lh;
 991
 992                 if (se->start_page <= offset &&
 993                                 offset < (se->start_page + se->nr_pages)) {
 994                         return se->start_block + (offset - se->start_page);
 995                 }
 996                 lh = se->list.next;
 997                 if (lh == &sis->extent_list)
 998                         lh = lh->next;
 999                 se = list_entry(lh, struct swap_extent, list);
1000                 sis->curr_swap_extent = se;
1001                 BUG_ON(se == start_se);         /* It *must* be present */
1002         }
1003 }
1004
1005 #ifdef CONFIG_HIBERNATION
1006 /*
1007  * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1008  * corresponding to given index in swap_info (swap type).
1009  */
1010 sector_t swapdev_block(int swap_type, pgoff_t offset)
1011 {
1012         struct swap_info_struct *sis;
1013
1014         if (swap_type >= nr_swapfiles)
1015                 return 0;
1016
1017         sis = swap_info + swap_type;
1018         return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0;
1019 }
1020 #endif /* CONFIG_HIBERNATION */
1021
1022 /*
1023  * Free all of a swapdev's extent information
1024  */
1025 static void destroy_swap_extents(struct swap_info_struct *sis)
1026 {
1027         while (!list_empty(&sis->extent_list)) {
1028                 struct swap_extent *se;
1029
1030                 se = list_entry(sis->extent_list.next,
1031                                 struct swap_extent, list);
1032                 list_del(&se->list);
1033                 kfree(se);
1034         }
1035 }
1036
1037 /*
1038  * Add a block range (and the corresponding page range) into this swapdev's
1039  * extent list.  The extent list is kept sorted in page order.
1040  *
1041  * This function rather assumes that it is called in ascending page order.
1042  */
1043 static int
1044 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1045                 unsigned long nr_pages, sector_t start_block)
1046 {
1047         struct swap_extent *se;
1048         struct swap_extent *new_se;
1049         struct list_head *lh;
1050
1051         lh = sis->extent_list.prev;     /* The highest page extent */
1052         if (lh != &sis->extent_list) {
1053                 se = list_entry(lh, struct swap_extent, list);
1054                 BUG_ON(se->start_page + se->nr_pages != start_page);
1055                 if (se->start_block + se->nr_pages == start_block) {
1056                         /* Merge it */
1057                         se->nr_pages += nr_pages;
1058                         return 0;
1059                 }
1060         }
1061
1062         /*
1063          * No merge.  Insert a new extent, preserving ordering.
1064          */
1065         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1066         if (new_se == NULL)
1067                 return -ENOMEM;
1068         new_se->start_page = start_page;
1069         new_se->nr_pages = nr_pages;
1070         new_se->start_block = start_block;
1071
1072         list_add_tail(&new_se->list, &sis->extent_list);
1073         return 1;
1074 }
1075
1076 /*
1077  * A `swap extent' is a simple thing which maps a contiguous range of pages
1078  * onto a contiguous range of disk blocks.  An ordered list of swap extents
1079  * is built at swapon time and is then used at swap_writepage/swap_readpage
1080  * time for locating where on disk a page belongs.
1081  *
1082  * If the swapfile is an S_ISBLK block device, a single extent is installed.
1083  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1084  * swap files identically.
1085  *
1086  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1087  * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
1088  * swapfiles are handled *identically* after swapon time.
1089  *
1090  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1091  * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
1092  * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1093  * requirements, they are simply tossed out - we will never use those blocks
1094  * for swapping.
1095  *
1096  * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
1097  * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1098  * which will scribble on the fs.
1099  *
1100  * The amount of disk space which a single swap extent represents varies.
1101  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
1102  * extents in the list.  To avoid much list walking, we cache the previous
1103  * search location in `curr_swap_extent', and start new searches from there.
1104  * This is extremely effective.  The average number of iterations in
1105  * map_swap_page() has been measured at about 0.3 per page.  - akpm.
1106  */
1107 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1108 {
1109         struct inode *inode;
1110         unsigned blocks_per_page;
1111         unsigned long page_no;
1112         unsigned blkbits;
1113         sector_t probe_block;
1114         sector_t last_block;
1115         sector_t lowest_block = -1;
1116         sector_t highest_block = 0;
1117         int nr_extents = 0;
1118         int ret;
1119
1120         inode = sis->swap_file->f_mapping->host;
1121         if (S_ISBLK(inode->i_mode)) {
1122                 ret = add_swap_extent(sis, 0, sis->max, 0);
1123                 *span = sis->pages;
1124                 goto done;
1125         }
1126
1127         blkbits = inode->i_blkbits;
1128         blocks_per_page = PAGE_SIZE >> blkbits;
1129
1130         /*
1131          * Map all the blocks into the extent list.  This code doesn't try
1132          * to be very smart.
1133          */
1134         probe_block = 0;
1135         page_no = 0;
1136         last_block = i_size_read(inode) >> blkbits;
1137         while ((probe_block + blocks_per_page) <= last_block &&
1138                         page_no < sis->max) {
1139                 unsigned block_in_page;
1140                 sector_t first_block;
1141
1142                 first_block = bmap(inode, probe_block);
1143                 if (first_block == 0)
1144                         goto bad_bmap;
1145
1146                 /*
1147                  * It must be PAGE_SIZE aligned on-disk
1148                  */
1149                 if (first_block & (blocks_per_page - 1)) {
1150                         probe_block++;
1151                         goto reprobe;
1152                 }
1153
1154                 for (block_in_page = 1; block_in_page < blocks_per_page;
1155                                         block_in_page++) {
1156                         sector_t block;
1157
1158                         block = bmap(inode, probe_block + block_in_page);
1159                         if (block == 0)
1160                                 goto bad_bmap;
1161                         if (block != first_block + block_in_page) {
1162                                 /* Discontiguity */
1163                                 probe_block++;
1164                                 goto reprobe;
1165                         }
1166                 }
1167
1168                 first_block >>= (PAGE_SHIFT - blkbits);
1169                 if (page_no) {  /* exclude the header page */
1170                         if (first_block < lowest_block)
1171                                 lowest_block = first_block;
1172                         if (first_block > highest_block)
1173                                 highest_block = first_block;
1174                 }
1175
1176                 /*
1177                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1178                  */
1179                 ret = add_swap_extent(sis, page_no, 1, first_block);
1180                 if (ret < 0)
1181                         goto out;
1182                 nr_extents += ret;
1183                 page_no++;
1184                 probe_block += blocks_per_page;
1185 reprobe:
1186                 continue;
1187         }
1188         ret = nr_extents;
1189         *span = 1 + highest_block - lowest_block;
1190         if (page_no == 0)
1191                 page_no = 1;    /* force Empty message */
1192         sis->max = page_no;
1193         sis->pages = page_no - 1;
1194         sis->highest_bit = page_no - 1;
1195 done:
1196         sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1197                                         struct swap_extent, list);
1198         goto out;
1199 bad_bmap:
1200         printk(KERN_ERR "swapon: swapfile has holes\n");
1201         ret = -EINVAL;
1202 out:
1203         return ret;
1204 }
1205
1206 #if 0   /* We don't need this yet */
1207 #include <linux/backing-dev.h>
1208 int page_queue_congested(struct page *page)
1209 {
1210         struct backing_dev_info *bdi;
1211
1212         BUG_ON(!PageLocked(page));      /* It pins the swap_info_struct */
1213
1214         if (PageSwapCache(page)) {
1215                 swp_entry_t entry = { .val = page_private(page) };
1216                 struct swap_info_struct *sis;
1217
1218                 sis = get_swap_info_struct(swp_type(entry));
1219                 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1220         } else
1221                 bdi = page->mapping->backing_dev_info;
1222         return bdi_write_congested(bdi);
1223 }
1224 #endif
1225
1226 asmlinkage long sys_swapoff(const char __user * specialfile)
1227 {
1228         struct swap_info_struct * p = NULL;
1229         unsigned short *swap_map;
1230         struct file *swap_file, *victim;
1231         struct address_space *mapping;
1232         struct inode *inode;
1233         char * pathname;
1234         int i, type, prev;
1235         int err;
1236
1237         if (!capable(CAP_SYS_ADMIN))
1238                 return -EPERM;
1239
1240         pathname = getname(specialfile);
1241         err = PTR_ERR(pathname);
1242         if (IS_ERR(pathname))
1243                 goto out;
1244
1245         victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1246         putname(pathname);
1247         err = PTR_ERR(victim);
1248         if (IS_ERR(victim))
1249                 goto out;
1250
1251         mapping = victim->f_mapping;
1252         prev = -1;
1253         spin_lock(&swap_lock);
1254         for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1255                 p = swap_info + type;
1256                 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1257                         if (p->swap_file->f_mapping == mapping)
1258                                 break;
1259                 }
1260                 prev = type;
1261         }
1262         if (type < 0) {
1263                 err = -EINVAL;
1264                 spin_unlock(&swap_lock);
1265                 goto out_dput;
1266         }
1267         if (!security_vm_enough_memory(p->pages))
1268                 vm_unacct_memory(p->pages);
1269         else {
1270                 err = -ENOMEM;
1271                 spin_unlock(&swap_lock);
1272                 goto out_dput;
1273         }
1274         if (prev < 0) {
1275                 swap_list.head = p->next;
1276         } else {
1277                 swap_info[prev].next = p->next;
1278         }
1279         if (type == swap_list.next) {
1280                 /* just pick something that's safe... */
1281                 swap_list.next = swap_list.head;
1282         }
1283         if (p->prio < 0) {
1284                 for (i = p->next; i >= 0; i = swap_info[i].next)
1285                         swap_info[i].prio = p->prio--;
1286                 least_priority++;
1287         }
1288         nr_swap_pages -= p->pages;
1289         total_swap_pages -= p->pages;
1290         p->flags &= ~SWP_WRITEOK;
1291         spin_unlock(&swap_lock);
1292
1293         current->flags |= PF_SWAPOFF;
1294         err = try_to_unuse(type);
1295         current->flags &= ~PF_SWAPOFF;
1296
1297         if (err) {
1298                 /* re-insert swap space back into swap_list */
1299                 spin_lock(&swap_lock);
1300                 if (p->prio < 0)
1301                         p->prio = --least_priority;
1302                 prev = -1;
1303                 for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1304                         if (p->prio >= swap_info[i].prio)
1305                                 break;
1306                         prev = i;
1307                 }
1308                 p->next = i;
1309                 if (prev < 0)
1310                         swap_list.head = swap_list.next = p - swap_info;
1311                 else
1312                         swap_info[prev].next = p - swap_info;
1313                 nr_swap_pages += p->pages;
1314                 total_swap_pages += p->pages;
1315                 p->flags |= SWP_WRITEOK;
1316                 spin_unlock(&swap_lock);
1317                 goto out_dput;
1318         }
1319
1320         /* wait for any unplug function to finish */
1321         down_write(&swap_unplug_sem);
1322         up_write(&swap_unplug_sem);
1323
1324         destroy_swap_extents(p);
1325         mutex_lock(&swapon_mutex);
1326         spin_lock(&swap_lock);
1327         drain_mmlist();
1328
1329         /* wait for anyone still in scan_swap_map */
1330         p->highest_bit = 0;             /* cuts scans short */
1331         while (p->flags >= SWP_SCANNING) {
1332                 spin_unlock(&swap_lock);
1333                 schedule_timeout_uninterruptible(1);
1334                 spin_lock(&swap_lock);
1335         }
1336
1337         swap_file = p->swap_file;
1338         p->swap_file = NULL;
1339         p->max = 0;
1340         swap_map = p->swap_map;
1341         p->swap_map = NULL;
1342         p->flags = 0;
1343         spin_unlock(&swap_lock);
1344         mutex_unlock(&swapon_mutex);
1345         vfree(swap_map);
1346         inode = mapping->host;
1347         if (S_ISBLK(inode->i_mode)) {
1348                 struct block_device *bdev = I_BDEV(inode);
1349                 set_blocksize(bdev, p->old_block_size);
1350                 bd_release(bdev);
1351         } else {
1352                 mutex_lock(&inode->i_mutex);
1353                 inode->i_flags &= ~S_SWAPFILE;
1354                 mutex_unlock(&inode->i_mutex);
1355         }
1356         filp_close(swap_file, NULL);
1357         err = 0;
1358
1359 out_dput:
1360         filp_close(victim, NULL);
1361 out:
1362         return err;
1363 }
1364
1365 #ifdef CONFIG_PROC_FS
1366 /* iterator */
1367 static void *swap_start(struct seq_file *swap, loff_t *pos)
1368 {
1369         struct swap_info_struct *ptr = swap_info;
1370         int i;
1371         loff_t l = *pos;
1372
1373         mutex_lock(&swapon_mutex);
1374
1375         if (!l)
1376                 return SEQ_START_TOKEN;
1377
1378         for (i = 0; i < nr_swapfiles; i++, ptr++) {
1379                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1380                         continue;
1381                 if (!--l)
1382                         return ptr;
1383         }
1384
1385         return NULL;
1386 }
1387
1388 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1389 {
1390         struct swap_info_struct *ptr;
1391         struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1392
1393         if (v == SEQ_START_TOKEN)
1394                 ptr = swap_info;
1395         else {
1396                 ptr = v;
1397                 ptr++;
1398         }
1399
1400         for (; ptr < endptr; ptr++) {
1401                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1402                         continue;
1403                 ++*pos;
1404                 return ptr;
1405         }
1406
1407         return NULL;
1408 }
1409
1410 static void swap_stop(struct seq_file *swap, void *v)
1411 {
1412         mutex_unlock(&swapon_mutex);
1413 }
1414
1415 static int swap_show(struct seq_file *swap, void *v)
1416 {
1417         struct swap_info_struct *ptr = v;
1418         struct file *file;
1419         int len;
1420
1421         if (ptr == SEQ_START_TOKEN) {
1422                 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1423                 return 0;
1424         }
1425
1426         file = ptr->swap_file;
1427         len = seq_path(swap, &file->f_path, " \t\n\\");
1428         seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1429                        len < 40 ? 40 - len : 1, " ",
1430                        S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1431                                 "partition" : "file\t",
1432                        ptr->pages << (PAGE_SHIFT - 10),
1433                        ptr->inuse_pages << (PAGE_SHIFT - 10),
1434                        ptr->prio);
1435         return 0;
1436 }
1437
1438 static const struct seq_operations swaps_op = {
1439         .start =        swap_start,
1440         .next =         swap_next,
1441         .stop =         swap_stop,
1442         .show =         swap_show
1443 };
1444
1445 static int swaps_open(struct inode *inode, struct file *file)
1446 {
1447         return seq_open(file, &swaps_op);
1448 }
1449
1450 static const struct file_operations proc_swaps_operations = {
1451         .open           = swaps_open,
1452         .read           = seq_read,
1453         .llseek         = seq_lseek,
1454         .release        = seq_release,
1455 };
1456
1457 static int __init procswaps_init(void)
1458 {
1459         proc_create("swaps", 0, NULL, &proc_swaps_operations);
1460         return 0;
1461 }
1462 __initcall(procswaps_init);
1463 #endif /* CONFIG_PROC_FS */
1464
1465 #ifdef MAX_SWAPFILES_CHECK
1466 static int __init max_swapfiles_check(void)
1467 {
1468         MAX_SWAPFILES_CHECK();
1469         return 0;
1470 }
1471 late_initcall(max_swapfiles_check);
1472 #endif
1473
1474 /*
1475  * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1476  *
1477  * The swapon system call
1478  */
1479 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1480 {
1481         struct swap_info_struct * p;
1482         char *name = NULL;
1483         struct block_device *bdev = NULL;
1484         struct file *swap_file = NULL;
1485         struct address_space *mapping;
1486         unsigned int type;
1487         int i, prev;
1488         int error;
1489         union swap_header *swap_header = NULL;
1490         int swap_header_version;
1491         unsigned int nr_good_pages = 0;
1492         int nr_extents = 0;
1493         sector_t span;
1494         unsigned long maxpages = 1;
1495         int swapfilesize;
1496         unsigned short *swap_map = NULL;
1497         struct page *page = NULL;
1498         struct inode *inode = NULL;
1499         int did_down = 0;
1500
1501         if (!capable(CAP_SYS_ADMIN))
1502                 return -EPERM;
1503         spin_lock(&swap_lock);
1504         p = swap_info;
1505         for (type = 0 ; type < nr_swapfiles ; type++,p++)
1506                 if (!(p->flags & SWP_USED))
1507                         break;
1508         error = -EPERM;
1509         if (type >= MAX_SWAPFILES) {
1510                 spin_unlock(&swap_lock);
1511                 goto out;
1512         }
1513         if (type >= nr_swapfiles)
1514                 nr_swapfiles = type+1;
1515         memset(p, 0, sizeof(*p));
1516         INIT_LIST_HEAD(&p->extent_list);
1517         p->flags = SWP_USED;
1518         p->next = -1;
1519         spin_unlock(&swap_lock);
1520         name = getname(specialfile);
1521         error = PTR_ERR(name);
1522         if (IS_ERR(name)) {
1523                 name = NULL;
1524                 goto bad_swap_2;
1525         }
1526         swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1527         error = PTR_ERR(swap_file);
1528         if (IS_ERR(swap_file)) {
1529                 swap_file = NULL;
1530                 goto bad_swap_2;
1531         }
1532
1533         p->swap_file = swap_file;
1534         mapping = swap_file->f_mapping;
1535         inode = mapping->host;
1536
1537         error = -EBUSY;
1538         for (i = 0; i < nr_swapfiles; i++) {
1539                 struct swap_info_struct *q = &swap_info[i];
1540
1541                 if (i == type || !q->swap_file)
1542                         continue;
1543                 if (mapping == q->swap_file->f_mapping)
1544                         goto bad_swap;
1545         }
1546
1547         error = -EINVAL;
1548         if (S_ISBLK(inode->i_mode)) {
1549                 bdev = I_BDEV(inode);
1550                 error = bd_claim(bdev, sys_swapon);
1551                 if (error < 0) {
1552                         bdev = NULL;
1553                         error = -EINVAL;
1554                         goto bad_swap;
1555                 }
1556                 p->old_block_size = block_size(bdev);
1557                 error = set_blocksize(bdev, PAGE_SIZE);
1558                 if (error < 0)
1559                         goto bad_swap;
1560                 p->bdev = bdev;
1561         } else if (S_ISREG(inode->i_mode)) {
1562                 p->bdev = inode->i_sb->s_bdev;
1563                 mutex_lock(&inode->i_mutex);
1564                 did_down = 1;
1565                 if (IS_SWAPFILE(inode)) {
1566                         error = -EBUSY;
1567                         goto bad_swap;
1568                 }
1569         } else {
1570                 goto bad_swap;
1571         }
1572
1573         swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1574
1575         /*
1576          * Read the swap header.
1577          */
1578         if (!mapping->a_ops->readpage) {
1579                 error = -EINVAL;
1580                 goto bad_swap;
1581         }
1582         page = read_mapping_page(mapping, 0, swap_file);
1583         if (IS_ERR(page)) {
1584                 error = PTR_ERR(page);
1585                 goto bad_swap;
1586         }
1587         kmap(page);
1588         swap_header = page_address(page);
1589
1590         if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1591                 swap_header_version = 1;
1592         else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1593                 swap_header_version = 2;
1594         else {
1595                 printk(KERN_ERR "Unable to find swap-space signature\n");
1596                 error = -EINVAL;
1597                 goto bad_swap;
1598         }
1599
1600         switch (swap_header_version) {
1601         case 1:
1602                 printk(KERN_ERR "version 0 swap is no longer supported. "
1603                         "Use mkswap -v1 %s\n", name);
1604                 error = -EINVAL;
1605                 goto bad_swap;
1606         case 2:
1607                 /* swap partition endianess hack... */
1608                 if (swab32(swap_header->info.version) == 1) {
1609                         swab32s(&swap_header->info.version);
1610                         swab32s(&swap_header->info.last_page);
1611                         swab32s(&swap_header->info.nr_badpages);
1612                         for (i = 0; i < swap_header->info.nr_badpages; i++)
1613                                 swab32s(&swap_header->info.badpages[i]);
1614                 }
1615                 /* Check the swap header's sub-version and the size of
1616                    the swap file and bad block lists */
1617                 if (swap_header->info.version != 1) {
1618                         printk(KERN_WARNING
1619                                "Unable to handle swap header version %d\n",
1620                                swap_header->info.version);
1621                         error = -EINVAL;
1622                         goto bad_swap;
1623                 }
1624
1625                 p->lowest_bit  = 1;
1626                 p->cluster_next = 1;
1627
1628                 /*
1629                  * Find out how many pages are allowed for a single swap
1630                  * device. There are two limiting factors: 1) the number of
1631                  * bits for the swap offset in the swp_entry_t type and
1632                  * 2) the number of bits in the a swap pte as defined by
1633                  * the different architectures. In order to find the
1634                  * largest possible bit mask a swap entry with swap type 0
1635                  * and swap offset ~0UL is created, encoded to a swap pte,
1636                  * decoded to a swp_entry_t again and finally the swap
1637                  * offset is extracted. This will mask all the bits from
1638                  * the initial ~0UL mask that can't be encoded in either
1639                  * the swp_entry_t or the architecture definition of a
1640                  * swap pte.
1641                  */
1642                 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1643                 if (maxpages > swap_header->info.last_page)
1644                         maxpages = swap_header->info.last_page;
1645                 p->highest_bit = maxpages - 1;
1646
1647                 error = -EINVAL;
1648                 if (!maxpages)
1649                         goto bad_swap;
1650                 if (swapfilesize && maxpages > swapfilesize) {
1651                         printk(KERN_WARNING
1652                                "Swap area shorter than signature indicates\n");
1653                         goto bad_swap;
1654                 }
1655                 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1656                         goto bad_swap;
1657                 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1658                         goto bad_swap;
1659
1660                 /* OK, set up the swap map and apply the bad block list */
1661                 swap_map = vmalloc(maxpages * sizeof(short));
1662                 if (!swap_map) {
1663                         error = -ENOMEM;
1664                         goto bad_swap;
1665                 }
1666
1667                 error = 0;
1668                 memset(swap_map, 0, maxpages * sizeof(short));
1669                 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1670                         int page_nr = swap_header->info.badpages[i];
1671                         if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
1672                                 error = -EINVAL;
1673                         else
1674                                 swap_map[page_nr] = SWAP_MAP_BAD;
1675                 }
1676                 nr_good_pages = swap_header->info.last_page -
1677                                 swap_header->info.nr_badpages -
1678                                 1 /* header page */;
1679                 if (error)
1680                         goto bad_swap;
1681         }
1682
1683         if (nr_good_pages) {
1684                 swap_map[0] = SWAP_MAP_BAD;
1685                 p->max = maxpages;
1686                 p->pages = nr_good_pages;
1687                 nr_extents = setup_swap_extents(p, &span);
1688                 if (nr_extents < 0) {
1689                         error = nr_extents;
1690                         goto bad_swap;
1691                 }
1692                 nr_good_pages = p->pages;
1693         }
1694         if (!nr_good_pages) {
1695                 printk(KERN_WARNING "Empty swap-file\n");
1696                 error = -EINVAL;
1697                 goto bad_swap;
1698         }
1699
1700         mutex_lock(&swapon_mutex);
1701         spin_lock(&swap_lock);
1702         if (swap_flags & SWAP_FLAG_PREFER)
1703                 p->prio =
1704                   (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
1705         else
1706                 p->prio = --least_priority;
1707         p->swap_map = swap_map;
1708         p->flags = SWP_ACTIVE;
1709         nr_swap_pages += nr_good_pages;
1710         total_swap_pages += nr_good_pages;
1711
1712         printk(KERN_INFO "Adding %uk swap on %s.  "
1713                         "Priority:%d extents:%d across:%lluk\n",
1714                 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1715                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
1716
1717         /* insert swap space into swap_list: */
1718         prev = -1;
1719         for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1720                 if (p->prio >= swap_info[i].prio) {
1721                         break;
1722                 }
1723                 prev = i;
1724         }
1725         p->next = i;
1726         if (prev < 0) {
1727                 swap_list.head = swap_list.next = p - swap_info;
1728         } else {
1729                 swap_info[prev].next = p - swap_info;
1730         }
1731         spin_unlock(&swap_lock);
1732         mutex_unlock(&swapon_mutex);
1733         error = 0;
1734         goto out;
1735 bad_swap:
1736         if (bdev) {
1737                 set_blocksize(bdev, p->old_block_size);
1738                 bd_release(bdev);
1739         }
1740         destroy_swap_extents(p);
1741 bad_swap_2:
1742         spin_lock(&swap_lock);
1743         p->swap_file = NULL;
1744         p->flags = 0;
1745         spin_unlock(&swap_lock);
1746         vfree(swap_map);
1747         if (swap_file)
1748                 filp_close(swap_file, NULL);
1749 out:
1750         if (page && !IS_ERR(page)) {
1751                 kunmap(page);
1752                 page_cache_release(page);
1753         }
1754         if (name)
1755                 putname(name);
1756         if (did_down) {
1757                 if (!error)
1758                         inode->i_flags |= S_SWAPFILE;
1759                 mutex_unlock(&inode->i_mutex);
1760         }
1761         return error;
1762 }
1763
1764 void si_swapinfo(struct sysinfo *val)
1765 {
1766         unsigned int i;
1767         unsigned long nr_to_be_unused = 0;
1768
1769         spin_lock(&swap_lock);
1770         for (i = 0; i < nr_swapfiles; i++) {
1771                 if (!(swap_info[i].flags & SWP_USED) ||
1772                      (swap_info[i].flags & SWP_WRITEOK))
1773                         continue;
1774                 nr_to_be_unused += swap_info[i].inuse_pages;
1775         }
1776         val->freeswap = nr_swap_pages + nr_to_be_unused;
1777         val->totalswap = total_swap_pages + nr_to_be_unused;
1778         spin_unlock(&swap_lock);
1779 }
1780
1781 /*
1782  * Verify that a swap entry is valid and increment its swap map count.
1783  *
1784  * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1785  * "permanent", but will be reclaimed by the next swapoff.
1786  */
1787 int swap_duplicate(swp_entry_t entry)
1788 {
1789         struct swap_info_struct * p;
1790         unsigned long offset, type;
1791         int result = 0;
1792
1793         if (is_migration_entry(entry))
1794                 return 1;
1795
1796         type = swp_type(entry);
1797         if (type >= nr_swapfiles)
1798                 goto bad_file;
1799         p = type + swap_info;
1800         offset = swp_offset(entry);
1801
1802         spin_lock(&swap_lock);
1803         if (offset < p->max && p->swap_map[offset]) {
1804                 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1805                         p->swap_map[offset]++;
1806                         result = 1;
1807                 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1808                         if (swap_overflow++ < 5)
1809                                 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1810                         p->swap_map[offset] = SWAP_MAP_MAX;
1811                         result = 1;
1812                 }
1813         }
1814         spin_unlock(&swap_lock);
1815 out:
1816         return result;
1817
1818 bad_file:
1819         printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1820         goto out;
1821 }
1822
1823 struct swap_info_struct *
1824 get_swap_info_struct(unsigned type)
1825 {
1826         return &swap_info[type];
1827 }
1828
1829 /*
1830  * swap_lock prevents swap_map being freed. Don't grab an extra
1831  * reference on the swaphandle, it doesn't matter if it becomes unused.
1832  */
1833 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1834 {
1835         struct swap_info_struct *si;
1836         int our_page_cluster = page_cluster;
1837         pgoff_t target, toff;
1838         pgoff_t base, end;
1839         int nr_pages = 0;
1840
1841         if (!our_page_cluster)  /* no readahead */
1842                 return 0;
1843
1844         si = &swap_info[swp_type(entry)];
1845         target = swp_offset(entry);
1846         base = (target >> our_page_cluster) << our_page_cluster;
1847         end = base + (1 << our_page_cluster);
1848         if (!base)              /* first page is swap header */
1849                 base++;
1850
1851         spin_lock(&swap_lock);
1852         if (end > si->max)      /* don't go beyond end of map */
1853                 end = si->max;
1854
1855         /* Count contiguous allocated slots above our target */
1856         for (toff = target; ++toff < end; nr_pages++) {
1857                 /* Don't read in free or bad pages */
1858                 if (!si->swap_map[toff])
1859                         break;
1860                 if (si->swap_map[toff] == SWAP_MAP_BAD)
1861                         break;
1862         }
1863         /* Count contiguous allocated slots below our target */
1864         for (toff = target; --toff >= base; nr_pages++) {
1865                 /* Don't read in free or bad pages */
1866                 if (!si->swap_map[toff])
1867                         break;
1868                 if (si->swap_map[toff] == SWAP_MAP_BAD)
1869                         break;
1870         }
1871         spin_unlock(&swap_lock);
1872
1873         /*
1874          * Indicate starting offset, and return number of pages to get:
1875          * if only 1, say 0, since there's then no readahead to be done.
1876          */
1877         *offset = ++toff;
1878         return nr_pages? ++nr_pages: 0;
1879 }