err.no Git - linux-2.6/blob - 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/config.h>
   9 #include <linux/mm.h>
  10 #include <linux/hugetlb.h>
  11 #include <linux/mman.h>
  12 #include <linux/slab.h>
  13 #include <linux/kernel_stat.h>
  14 #include <linux/swap.h>
  15 #include <linux/vmalloc.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/namei.h>
  18 #include <linux/shm.h>
  19 #include <linux/blkdev.h>
  20 #include <linux/writeback.h>
  21 #include <linux/proc_fs.h>
  22 #include <linux/seq_file.h>
  23 #include <linux/init.h>
  24 #include <linux/module.h>
  25 #include <linux/rmap.h>
  26 #include <linux/security.h>
  27 #include <linux/backing-dev.h>
  28 #include <linux/syscalls.h>
  29
  30 #include <asm/pgtable.h>
  31 #include <asm/tlbflush.h>
  32 #include <linux/swapops.h>
  33
  34 DEFINE_SPINLOCK(swap_lock);
  35 unsigned int nr_swapfiles;
  36 long total_swap_pages;
  37 static int swap_overflow;
  38
  39 static const char Bad_file[] = "Bad swap file entry ";
  40 static const char Unused_file[] = "Unused swap file entry ";
  41 static const char Bad_offset[] = "Bad swap offset entry ";
  42 static const char Unused_offset[] = "Unused swap offset entry ";
  43
  44 struct swap_list_t swap_list = {-1, -1};
  45
  46 struct swap_info_struct swap_info[MAX_SWAPFILES];
  47
  48 static DECLARE_MUTEX(swapon_sem);
  49
  50 /*
  51  * We need this because the bdev->unplug_fn can sleep and we cannot
  52  * hold swap_lock while calling the unplug_fn. And swap_lock
  53  * cannot be turned into a semaphore.
  54  */
  55 static DECLARE_RWSEM(swap_unplug_sem);
  56
  57 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
  58 {
  59         swp_entry_t entry;
  60
  61         down_read(&swap_unplug_sem);
  62         entry.val = page_private(page);
  63         if (PageSwapCache(page)) {
  64                 struct block_device *bdev = swap_info[swp_type(entry)].bdev;
  65                 struct backing_dev_info *bdi;
  66
  67                 /*
  68                  * If the page is removed from swapcache from under us (with a
  69                  * racy try_to_unuse/swapoff) we need an additional reference
  70                  * count to avoid reading garbage from page_private(page) above.
  71                  * If the WARN_ON triggers during a swapoff it maybe the race
  72                  * condition and it's harmless. However if it triggers without
  73                  * swapoff it signals a problem.
  74                  */
  75                 WARN_ON(page_count(page) <= 1);
  76
  77                 bdi = bdev->bd_inode->i_mapping->backing_dev_info;
  78                 blk_run_backing_dev(bdi, page);
  79         }
  80         up_read(&swap_unplug_sem);
  81 }
  82
  83 #define SWAPFILE_CLUSTER        256
  84 #define LATENCY_LIMIT           256
  85
  86 static inline unsigned long scan_swap_map(struct swap_info_struct *si)
  87 {
  88         unsigned long offset, last_in_cluster;
  89         int latency_ration = LATENCY_LIMIT;
  90
  91         /*
  92          * We try to cluster swap pages by allocating them sequentially
  93          * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
  94          * way, however, we resort to first-free allocation, starting
  95          * a new cluster.  This prevents us from scattering swap pages
  96          * all over the entire swap partition, so that we reduce
  97          * overall disk seek times between swap pages.  -- sct
  98          * But we do now try to find an empty cluster.  -Andrea
  99          */
 100
 101         si->flags += SWP_SCANNING;
 102         if (unlikely(!si->cluster_nr)) {
 103                 si->cluster_nr = SWAPFILE_CLUSTER - 1;
 104                 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
 105                         goto lowest;
 106                 spin_unlock(&swap_lock);
 107
 108                 offset = si->lowest_bit;
 109                 last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
 110
 111                 /* Locate the first empty (unaligned) cluster */
 112                 for (; last_in_cluster <= si->highest_bit; offset++) {
 113                         if (si->swap_map[offset])
 114                                 last_in_cluster = offset + SWAPFILE_CLUSTER;
 115                         else if (offset == last_in_cluster) {
 116                                 spin_lock(&swap_lock);
 117                                 si->cluster_next = offset-SWAPFILE_CLUSTER-1;
 118                                 goto cluster;
 119                         }
 120                         if (unlikely(--latency_ration < 0)) {
 121                                 cond_resched();
 122                                 latency_ration = LATENCY_LIMIT;
 123                         }
 124                 }
 125                 spin_lock(&swap_lock);
 126                 goto lowest;
 127         }
 128
 129         si->cluster_nr--;
 130 cluster:
 131         offset = si->cluster_next;
 132         if (offset > si->highest_bit)
 133 lowest:         offset = si->lowest_bit;
 134 checks: if (!(si->flags & SWP_WRITEOK))
 135                 goto no_page;
 136         if (!si->highest_bit)
 137                 goto no_page;
 138         if (!si->swap_map[offset]) {
 139                 if (offset == si->lowest_bit)
 140                         si->lowest_bit++;
 141                 if (offset == si->highest_bit)
 142                         si->highest_bit--;
 143                 si->inuse_pages++;
 144                 if (si->inuse_pages == si->pages) {
 145                         si->lowest_bit = si->max;
 146                         si->highest_bit = 0;
 147                 }
 148                 si->swap_map[offset] = 1;
 149                 si->cluster_next = offset + 1;
 150                 si->flags -= SWP_SCANNING;
 151                 return offset;
 152         }
 153
 154         spin_unlock(&swap_lock);
 155         while (++offset <= si->highest_bit) {
 156                 if (!si->swap_map[offset]) {
 157                         spin_lock(&swap_lock);
 158                         goto checks;
 159                 }
 160                 if (unlikely(--latency_ration < 0)) {
 161                         cond_resched();
 162                         latency_ration = LATENCY_LIMIT;
 163                 }
 164         }
 165         spin_lock(&swap_lock);
 166         goto lowest;
 167
 168 no_page:
 169         si->flags -= SWP_SCANNING;
 170         return 0;
 171 }
 172
 173 swp_entry_t get_swap_page(void)
 174 {
 175         struct swap_info_struct *si;
 176         pgoff_t offset;
 177         int type, next;
 178         int wrapped = 0;
 179
 180         spin_lock(&swap_lock);
 181         if (nr_swap_pages <= 0)
 182                 goto noswap;
 183         nr_swap_pages--;
 184
 185         for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
 186                 si = swap_info + type;
 187                 next = si->next;
 188                 if (next < 0 ||
 189                     (!wrapped && si->prio != swap_info[next].prio)) {
 190                         next = swap_list.head;
 191                         wrapped++;
 192                 }
 193
 194                 if (!si->highest_bit)
 195                         continue;
 196                 if (!(si->flags & SWP_WRITEOK))
 197                         continue;
 198
 199                 swap_list.next = next;
 200                 offset = scan_swap_map(si);
 201                 if (offset) {
 202                         spin_unlock(&swap_lock);
 203                         return swp_entry(type, offset);
 204                 }
 205                 next = swap_list.next;
 206         }
 207
 208         nr_swap_pages++;
 209 noswap:
 210         spin_unlock(&swap_lock);
 211         return (swp_entry_t) {0};
 212 }
 213
 214 swp_entry_t get_swap_page_of_type(int type)
 215 {
 216         struct swap_info_struct *si;
 217         pgoff_t offset;
 218
 219         spin_lock(&swap_lock);
 220         si = swap_info + type;
 221         if (si->flags & SWP_WRITEOK) {
 222                 nr_swap_pages--;
 223                 offset = scan_swap_map(si);
 224                 if (offset) {
 225                         spin_unlock(&swap_lock);
 226                         return swp_entry(type, offset);
 227                 }
 228                 nr_swap_pages++;
 229         }
 230         spin_unlock(&swap_lock);
 231         return (swp_entry_t) {0};
 232 }
 233
 234 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
 235 {
 236         struct swap_info_struct * p;
 237         unsigned long offset, type;
 238
 239         if (!entry.val)
 240                 goto out;
 241         type = swp_type(entry);
 242         if (type >= nr_swapfiles)
 243                 goto bad_nofile;
 244         p = & swap_info[type];
 245         if (!(p->flags & SWP_USED))
 246                 goto bad_device;
 247         offset = swp_offset(entry);
 248         if (offset >= p->max)
 249                 goto bad_offset;
 250         if (!p->swap_map[offset])
 251                 goto bad_free;
 252         spin_lock(&swap_lock);
 253         return p;
 254
 255 bad_free:
 256         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
 257         goto out;
 258 bad_offset:
 259         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
 260         goto out;
 261 bad_device:
 262         printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
 263         goto out;
 264 bad_nofile:
 265         printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
 266 out:
 267         return NULL;
 268 }
 269
 270 static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
 271 {
 272         int count = p->swap_map[offset];
 273
 274         if (count < SWAP_MAP_MAX) {
 275                 count--;
 276                 p->swap_map[offset] = count;
 277                 if (!count) {
 278                         if (offset < p->lowest_bit)
 279                                 p->lowest_bit = offset;
 280                         if (offset > p->highest_bit)
 281                                 p->highest_bit = offset;
 282                         if (p->prio > swap_info[swap_list.next].prio)
 283                                 swap_list.next = p - swap_info;
 284                         nr_swap_pages++;
 285                         p->inuse_pages--;
 286                 }
 287         }
 288         return count;
 289 }
 290
 291 /*
 292  * Caller has made sure that the swapdevice corresponding to entry
 293  * is still around or has not been recycled.
 294  */
 295 void swap_free(swp_entry_t entry)
 296 {
 297         struct swap_info_struct * p;
 298
 299         p = swap_info_get(entry);
 300         if (p) {
 301                 swap_entry_free(p, swp_offset(entry));
 302                 spin_unlock(&swap_lock);
 303         }
 304 }
 305
 306 /*
 307  * How many references to page are currently swapped out?
 308  */
 309 static inline int page_swapcount(struct page *page)
 310 {
 311         int count = 0;
 312         struct swap_info_struct *p;
 313         swp_entry_t entry;
 314
 315         entry.val = page_private(page);
 316         p = swap_info_get(entry);
 317         if (p) {
 318                 /* Subtract the 1 for the swap cache itself */
 319                 count = p->swap_map[swp_offset(entry)] - 1;
 320                 spin_unlock(&swap_lock);
 321         }
 322         return count;
 323 }
 324
 325 /*
 326  * We can use this swap cache entry directly
 327  * if there are no other references to it.
 328  */
 329 int can_share_swap_page(struct page *page)
 330 {
 331         int count;
 332
 333         BUG_ON(!PageLocked(page));
 334         count = page_mapcount(page);
 335         if (count <= 1 && PageSwapCache(page))
 336                 count += page_swapcount(page);
 337         return count == 1;
 338 }
 339
 340 /*
 341  * Work out if there are any other processes sharing this
 342  * swap cache page. Free it if you can. Return success.
 343  */
 344 int remove_exclusive_swap_page(struct page *page)
 345 {
 346         int retval;
 347         struct swap_info_struct * p;
 348         swp_entry_t entry;
 349
 350         BUG_ON(PagePrivate(page));
 351         BUG_ON(!PageLocked(page));
 352
 353         if (!PageSwapCache(page))
 354                 return 0;
 355         if (PageWriteback(page))
 356                 return 0;
 357         if (page_count(page) != 2) /* 2: us + cache */
 358                 return 0;
 359
 360         entry.val = page_private(page);
 361         p = swap_info_get(entry);
 362         if (!p)
 363                 return 0;
 364
 365         /* Is the only swap cache user the cache itself? */
 366         retval = 0;
 367         if (p->swap_map[swp_offset(entry)] == 1) {
 368                 /* Recheck the page count with the swapcache lock held.. */
 369                 write_lock_irq(&swapper_space.tree_lock);
 370                 if ((page_count(page) == 2) && !PageWriteback(page)) {
 371                         __delete_from_swap_cache(page);
 372                         SetPageDirty(page);
 373                         retval = 1;
 374                 }
 375                 write_unlock_irq(&swapper_space.tree_lock);
 376         }
 377         spin_unlock(&swap_lock);
 378
 379         if (retval) {
 380                 swap_free(entry);
 381                 page_cache_release(page);
 382         }
 383
 384         return retval;
 385 }
 386
 387 /*
 388  * Free the swap entry like above, but also try to
 389  * free the page cache entry if it is the last user.
 390  */
 391 void free_swap_and_cache(swp_entry_t entry)
 392 {
 393         struct swap_info_struct * p;
 394         struct page *page = NULL;
 395
 396         p = swap_info_get(entry);
 397         if (p) {
 398                 if (swap_entry_free(p, swp_offset(entry)) == 1)
 399                         page = find_trylock_page(&swapper_space, entry.val);
 400                 spin_unlock(&swap_lock);
 401         }
 402         if (page) {
 403                 int one_user;
 404
 405                 BUG_ON(PagePrivate(page));
 406                 page_cache_get(page);
 407                 one_user = (page_count(page) == 2);
 408                 /* Only cache user (+us), or swap space full? Free it! */
 409                 if (!PageWriteback(page) && (one_user || vm_swap_full())) {
 410                         delete_from_swap_cache(page);
 411                         SetPageDirty(page);
 412                 }
 413                 unlock_page(page);
 414                 page_cache_release(page);
 415         }
 416 }
 417
 418 /*
 419  * No need to decide whether this PTE shares the swap entry with others,
 420  * just let do_wp_page work it out if a write is requested later - to
 421  * force COW, vm_page_prot omits write permission from any private vma.
 422  */
 423 static void unuse_pte(struct vm_area_struct *vma, pte_t *pte,
 424                 unsigned long addr, swp_entry_t entry, struct page *page)
 425 {
 426         inc_mm_counter(vma->vm_mm, anon_rss);
 427         get_page(page);
 428         set_pte_at(vma->vm_mm, addr, pte,
 429                    pte_mkold(mk_pte(page, vma->vm_page_prot)));
 430         page_add_anon_rmap(page, vma, addr);
 431         swap_free(entry);
 432         /*
 433          * Move the page to the active list so it is not
 434          * immediately swapped out again after swapon.
 435          */
 436         activate_page(page);
 437 }
 438
 439 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 440                                 unsigned long addr, unsigned long end,
 441                                 swp_entry_t entry, struct page *page)
 442 {
 443         pte_t swp_pte = swp_entry_to_pte(entry);
 444         pte_t *pte;
 445         spinlock_t *ptl;
 446         int found = 0;
 447
 448         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 449         do {
 450                 /*
 451                  * swapoff spends a _lot_ of time in this loop!
 452                  * Test inline before going to call unuse_pte.
 453                  */
 454                 if (unlikely(pte_same(*pte, swp_pte))) {
 455                         unuse_pte(vma, pte++, addr, entry, page);
 456                         found = 1;
 457                         break;
 458                 }
 459         } while (pte++, addr += PAGE_SIZE, addr != end);
 460         pte_unmap_unlock(pte - 1, ptl);
 461         return found;
 462 }
 463
 464 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
 465                                 unsigned long addr, unsigned long end,
 466                                 swp_entry_t entry, struct page *page)
 467 {
 468         pmd_t *pmd;
 469         unsigned long next;
 470
 471         pmd = pmd_offset(pud, addr);
 472         do {
 473                 next = pmd_addr_end(addr, end);
 474                 if (pmd_none_or_clear_bad(pmd))
 475                         continue;
 476                 if (unuse_pte_range(vma, pmd, addr, next, entry, page))
 477                         return 1;
 478         } while (pmd++, addr = next, addr != end);
 479         return 0;
 480 }
 481
 482 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
 483                                 unsigned long addr, unsigned long end,
 484                                 swp_entry_t entry, struct page *page)
 485 {
 486         pud_t *pud;
 487         unsigned long next;
 488
 489         pud = pud_offset(pgd, addr);
 490         do {
 491                 next = pud_addr_end(addr, end);
 492                 if (pud_none_or_clear_bad(pud))
 493                         continue;
 494                 if (unuse_pmd_range(vma, pud, addr, next, entry, page))
 495                         return 1;
 496         } while (pud++, addr = next, addr != end);
 497         return 0;
 498 }
 499
 500 static int unuse_vma(struct vm_area_struct *vma,
 501                                 swp_entry_t entry, struct page *page)
 502 {
 503         pgd_t *pgd;
 504         unsigned long addr, end, next;
 505
 506         if (page->mapping) {
 507                 addr = page_address_in_vma(page, vma);
 508                 if (addr == -EFAULT)
 509                         return 0;
 510                 else
 511                         end = addr + PAGE_SIZE;
 512         } else {
 513                 addr = vma->vm_start;
 514                 end = vma->vm_end;
 515         }
 516
 517         pgd = pgd_offset(vma->vm_mm, addr);
 518         do {
 519                 next = pgd_addr_end(addr, end);
 520                 if (pgd_none_or_clear_bad(pgd))
 521                         continue;
 522                 if (unuse_pud_range(vma, pgd, addr, next, entry, page))
 523                         return 1;
 524         } while (pgd++, addr = next, addr != end);
 525         return 0;
 526 }
 527
 528 static int unuse_mm(struct mm_struct *mm,
 529                                 swp_entry_t entry, struct page *page)
 530 {
 531         struct vm_area_struct *vma;
 532
 533         if (!down_read_trylock(&mm->mmap_sem)) {
 534                 /*
 535                  * Activate page so shrink_cache is unlikely to unmap its
 536                  * ptes while lock is dropped, so swapoff can make progress.
 537                  */
 538                 activate_page(page);
 539                 unlock_page(page);
 540                 down_read(&mm->mmap_sem);
 541                 lock_page(page);
 542         }
 543         for (vma = mm->mmap; vma; vma = vma->vm_next) {
 544                 if (vma->anon_vma && unuse_vma(vma, entry, page))
 545                         break;
 546         }
 547         up_read(&mm->mmap_sem);
 548         /*
 549          * Currently unuse_mm cannot fail, but leave error handling
 550          * at call sites for now, since we change it from time to time.
 551          */
 552         return 0;
 553 }
 554
 555 /*
 556  * Scan swap_map from current position to next entry still in use.
 557  * Recycle to start on reaching the end, returning 0 when empty.
 558  */
 559 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
 560                                         unsigned int prev)
 561 {
 562         unsigned int max = si->max;
 563         unsigned int i = prev;
 564         int count;
 565
 566         /*
 567          * No need for swap_lock here: we're just looking
 568          * for whether an entry is in use, not modifying it; false
 569          * hits are okay, and sys_swapoff() has already prevented new
 570          * allocations from this area (while holding swap_lock).
 571          */
 572         for (;;) {
 573                 if (++i >= max) {
 574                         if (!prev) {
 575                                 i = 0;
 576                                 break;
 577                         }
 578                         /*
 579                          * No entries in use at top of swap_map,
 580                          * loop back to start and recheck there.
 581                          */
 582                         max = prev + 1;
 583                         prev = 0;
 584                         i = 1;
 585                 }
 586                 count = si->swap_map[i];
 587                 if (count && count != SWAP_MAP_BAD)
 588                         break;
 589         }
 590         return i;
 591 }
 592
 593 /*
 594  * We completely avoid races by reading each swap page in advance,
 595  * and then search for the process using it.  All the necessary
 596  * page table adjustments can then be made atomically.
 597  */
 598 static int try_to_unuse(unsigned int type)
 599 {
 600         struct swap_info_struct * si = &swap_info[type];
 601         struct mm_struct *start_mm;
 602         unsigned short *swap_map;
 603         unsigned short swcount;
 604         struct page *page;
 605         swp_entry_t entry;
 606         unsigned int i = 0;
 607         int retval = 0;
 608         int reset_overflow = 0;
 609         int shmem;
 610
 611         /*
 612          * When searching mms for an entry, a good strategy is to
 613          * start at the first mm we freed the previous entry from
 614          * (though actually we don't notice whether we or coincidence
 615          * freed the entry).  Initialize this start_mm with a hold.
 616          *
 617          * A simpler strategy would be to start at the last mm we
 618          * freed the previous entry from; but that would take less
 619          * advantage of mmlist ordering, which clusters forked mms
 620          * together, child after parent.  If we race with dup_mmap(), we
 621          * prefer to resolve parent before child, lest we miss entries
 622          * duplicated after we scanned child: using last mm would invert
 623          * that.  Though it's only a serious concern when an overflowed
 624          * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
 625          */
 626         start_mm = &init_mm;
 627         atomic_inc(&init_mm.mm_users);
 628
 629         /*
 630          * Keep on scanning until all entries have gone.  Usually,
 631          * one pass through swap_map is enough, but not necessarily:
 632          * there are races when an instance of an entry might be missed.
 633          */
 634         while ((i = find_next_to_unuse(si, i)) != 0) {
 635                 if (signal_pending(current)) {
 636                         retval = -EINTR;
 637                         break;
 638                 }
 639
 640                 /*
 641                  * Get a page for the entry, using the existing swap
 642                  * cache page if there is one.  Otherwise, get a clean
 643                  * page and read the swap into it.
 644                  */
 645                 swap_map = &si->swap_map[i];
 646                 entry = swp_entry(type, i);
 647                 page = read_swap_cache_async(entry, NULL, 0);
 648                 if (!page) {
 649                         /*
 650                          * Either swap_duplicate() failed because entry
 651                          * has been freed independently, and will not be
 652                          * reused since sys_swapoff() already disabled
 653                          * allocation from here, or alloc_page() failed.
 654                          */
 655                         if (!*swap_map)
 656                                 continue;
 657                         retval = -ENOMEM;
 658                         break;
 659                 }
 660
 661                 /*
 662                  * Don't hold on to start_mm if it looks like exiting.
 663                  */
 664                 if (atomic_read(&start_mm->mm_users) == 1) {
 665                         mmput(start_mm);
 666                         start_mm = &init_mm;
 667                         atomic_inc(&init_mm.mm_users);
 668                 }
 669
 670                 /*
 671                  * Wait for and lock page.  When do_swap_page races with
 672                  * try_to_unuse, do_swap_page can handle the fault much
 673                  * faster than try_to_unuse can locate the entry.  This
 674                  * apparently redundant "wait_on_page_locked" lets try_to_unuse
 675                  * defer to do_swap_page in such a case - in some tests,
 676                  * do_swap_page and try_to_unuse repeatedly compete.
 677                  */
 678                 wait_on_page_locked(page);
 679                 wait_on_page_writeback(page);
 680                 lock_page(page);
 681                 wait_on_page_writeback(page);
 682
 683                 /*
 684                  * Remove all references to entry.
 685                  * Whenever we reach init_mm, there's no address space
 686                  * to search, but use it as a reminder to search shmem.
 687                  */
 688                 shmem = 0;
 689                 swcount = *swap_map;
 690                 if (swcount > 1) {
 691                         if (start_mm == &init_mm)
 692                                 shmem = shmem_unuse(entry, page);
 693                         else
 694                                 retval = unuse_mm(start_mm, entry, page);
 695                 }
 696                 if (*swap_map > 1) {
 697                         int set_start_mm = (*swap_map >= swcount);
 698                         struct list_head *p = &start_mm->mmlist;
 699                         struct mm_struct *new_start_mm = start_mm;
 700                         struct mm_struct *prev_mm = start_mm;
 701                         struct mm_struct *mm;
 702
 703                         atomic_inc(&new_start_mm->mm_users);
 704                         atomic_inc(&prev_mm->mm_users);
 705                         spin_lock(&mmlist_lock);
 706                         while (*swap_map > 1 && !retval &&
 707                                         (p = p->next) != &start_mm->mmlist) {
 708                                 mm = list_entry(p, struct mm_struct, mmlist);
 709                                 if (atomic_inc_return(&mm->mm_users) == 1) {
 710                                         atomic_dec(&mm->mm_users);
 711                                         continue;
 712                                 }
 713                                 spin_unlock(&mmlist_lock);
 714                                 mmput(prev_mm);
 715                                 prev_mm = mm;
 716
 717                                 cond_resched();
 718
 719                                 swcount = *swap_map;
 720                                 if (swcount <= 1)
 721                                         ;
 722                                 else if (mm == &init_mm) {
 723                                         set_start_mm = 1;
 724                                         shmem = shmem_unuse(entry, page);
 725                                 } else
 726                                         retval = unuse_mm(mm, entry, page);
 727                                 if (set_start_mm && *swap_map < swcount) {
 728                                         mmput(new_start_mm);
 729                                         atomic_inc(&mm->mm_users);
 730                                         new_start_mm = mm;
 731                                         set_start_mm = 0;
 732                                 }
 733                                 spin_lock(&mmlist_lock);
 734                         }
 735                         spin_unlock(&mmlist_lock);
 736                         mmput(prev_mm);
 737                         mmput(start_mm);
 738                         start_mm = new_start_mm;
 739                 }
 740                 if (retval) {
 741                         unlock_page(page);
 742                         page_cache_release(page);
 743                         break;
 744                 }
 745
 746                 /*
 747                  * How could swap count reach 0x7fff when the maximum
 748                  * pid is 0x7fff, and there's no way to repeat a swap
 749                  * page within an mm (except in shmem, where it's the
 750                  * shared object which takes the reference count)?
 751                  * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
 752                  *
 753                  * If that's wrong, then we should worry more about
 754                  * exit_mmap() and do_munmap() cases described above:
 755                  * we might be resetting SWAP_MAP_MAX too early here.
 756                  * We know "Undead"s can happen, they're okay, so don't
 757                  * report them; but do report if we reset SWAP_MAP_MAX.
 758                  */
 759                 if (*swap_map == SWAP_MAP_MAX) {
 760                         spin_lock(&swap_lock);
 761                         *swap_map = 1;
 762                         spin_unlock(&swap_lock);
 763                         reset_overflow = 1;
 764                 }
 765
 766                 /*
 767                  * If a reference remains (rare), we would like to leave
 768                  * the page in the swap cache; but try_to_unmap could
 769                  * then re-duplicate the entry once we drop page lock,
 770                  * so we might loop indefinitely; also, that page could
 771                  * not be swapped out to other storage meanwhile.  So:
 772                  * delete from cache even if there's another reference,
 773                  * after ensuring that the data has been saved to disk -
 774                  * since if the reference remains (rarer), it will be
 775                  * read from disk into another page.  Splitting into two
 776                  * pages would be incorrect if swap supported "shared
 777                  * private" pages, but they are handled by tmpfs files.
 778                  *
 779                  * Note shmem_unuse already deleted a swappage from
 780                  * the swap cache, unless the move to filepage failed:
 781                  * in which case it left swappage in cache, lowered its
 782                  * swap count to pass quickly through the loops above,
 783                  * and now we must reincrement count to try again later.
 784                  */
 785                 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
 786                         struct writeback_control wbc = {
 787                                 .sync_mode = WB_SYNC_NONE,
 788                         };
 789
 790                         swap_writepage(page, &wbc);
 791                         lock_page(page);
 792                         wait_on_page_writeback(page);
 793                 }
 794                 if (PageSwapCache(page)) {
 795                         if (shmem)
 796                                 swap_duplicate(entry);
 797                         else
 798                                 delete_from_swap_cache(page);
 799                 }
 800
 801                 /*
 802                  * So we could skip searching mms once swap count went
 803                  * to 1, we did not mark any present ptes as dirty: must
 804                  * mark page dirty so shrink_list will preserve it.
 805                  */
 806                 SetPageDirty(page);
 807                 unlock_page(page);
 808                 page_cache_release(page);
 809
 810                 /*
 811                  * Make sure that we aren't completely killing
 812                  * interactive performance.
 813                  */
 814                 cond_resched();
 815         }
 816
 817         mmput(start_mm);
 818         if (reset_overflow) {
 819                 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
 820                 swap_overflow = 0;
 821         }
 822         return retval;
 823 }
 824
 825 /*
 826  * After a successful try_to_unuse, if no swap is now in use, we know
 827  * we can empty the mmlist.  swap_lock must be held on entry and exit.
 828  * Note that mmlist_lock nests inside swap_lock, and an mm must be
 829  * added to the mmlist just after page_duplicate - before would be racy.
 830  */
 831 static void drain_mmlist(void)
 832 {
 833         struct list_head *p, *next;
 834         unsigned int i;
 835
 836         for (i = 0; i < nr_swapfiles; i++)
 837                 if (swap_info[i].inuse_pages)
 838                         return;
 839         spin_lock(&mmlist_lock);
 840         list_for_each_safe(p, next, &init_mm.mmlist)
 841                 list_del_init(p);
 842         spin_unlock(&mmlist_lock);
 843 }
 844
 845 /*
 846  * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
 847  * corresponds to page offset `offset'.
 848  */
 849 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
 850 {
 851         struct swap_extent *se = sis->curr_swap_extent;
 852         struct swap_extent *start_se = se;
 853
 854         for ( ; ; ) {
 855                 struct list_head *lh;
 856
 857                 if (se->start_page <= offset &&
 858                                 offset < (se->start_page + se->nr_pages)) {
 859                         return se->start_block + (offset - se->start_page);
 860                 }
 861                 lh = se->list.next;
 862                 if (lh == &sis->extent_list)
 863                         lh = lh->next;
 864                 se = list_entry(lh, struct swap_extent, list);
 865                 sis->curr_swap_extent = se;
 866                 BUG_ON(se == start_se);         /* It *must* be present */
 867         }
 868 }
 869
 870 /*
 871  * Free all of a swapdev's extent information
 872  */
 873 static void destroy_swap_extents(struct swap_info_struct *sis)
 874 {
 875         while (!list_empty(&sis->extent_list)) {
 876                 struct swap_extent *se;
 877
 878                 se = list_entry(sis->extent_list.next,
 879                                 struct swap_extent, list);
 880                 list_del(&se->list);
 881                 kfree(se);
 882         }
 883 }
 884
 885 /*
 886  * Add a block range (and the corresponding page range) into this swapdev's
 887  * extent list.  The extent list is kept sorted in page order.
 888  *
 889  * This function rather assumes that it is called in ascending page order.
 890  */
 891 static int
 892 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
 893                 unsigned long nr_pages, sector_t start_block)
 894 {
 895         struct swap_extent *se;
 896         struct swap_extent *new_se;
 897         struct list_head *lh;
 898
 899         lh = sis->extent_list.prev;     /* The highest page extent */
 900         if (lh != &sis->extent_list) {
 901                 se = list_entry(lh, struct swap_extent, list);
 902                 BUG_ON(se->start_page + se->nr_pages != start_page);
 903                 if (se->start_block + se->nr_pages == start_block) {
 904                         /* Merge it */
 905                         se->nr_pages += nr_pages;
 906                         return 0;
 907                 }
 908         }
 909
 910         /*
 911          * No merge.  Insert a new extent, preserving ordering.
 912          */
 913         new_se = kmalloc(sizeof(*se), GFP_KERNEL);
 914         if (new_se == NULL)
 915                 return -ENOMEM;
 916         new_se->start_page = start_page;
 917         new_se->nr_pages = nr_pages;
 918         new_se->start_block = start_block;
 919
 920         list_add_tail(&new_se->list, &sis->extent_list);
 921         return 1;
 922 }
 923
 924 /*
 925  * A `swap extent' is a simple thing which maps a contiguous range of pages
 926  * onto a contiguous range of disk blocks.  An ordered list of swap extents
 927  * is built at swapon time and is then used at swap_writepage/swap_readpage
 928  * time for locating where on disk a page belongs.
 929  *
 930  * If the swapfile is an S_ISBLK block device, a single extent is installed.
 931  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
 932  * swap files identically.
 933  *
 934  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
 935  * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
 936  * swapfiles are handled *identically* after swapon time.
 937  *
 938  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
 939  * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
 940  * some stray blocks are found which do not fall within the PAGE_SIZE alignment
 941  * requirements, they are simply tossed out - we will never use those blocks
 942  * for swapping.
 943  *
 944  * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
 945  * prevents root from shooting her foot off by ftruncating an in-use swapfile,
 946  * which will scribble on the fs.
 947  *
 948  * The amount of disk space which a single swap extent represents varies.
 949  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
 950  * extents in the list.  To avoid much list walking, we cache the previous
 951  * search location in `curr_swap_extent', and start new searches from there.
 952  * This is extremely effective.  The average number of iterations in
 953  * map_swap_page() has been measured at about 0.3 per page.  - akpm.
 954  */
 955 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
 956 {
 957         struct inode *inode;
 958         unsigned blocks_per_page;
 959         unsigned long page_no;
 960         unsigned blkbits;
 961         sector_t probe_block;
 962         sector_t last_block;
 963         sector_t lowest_block = -1;
 964         sector_t highest_block = 0;
 965         int nr_extents = 0;
 966         int ret;
 967
 968         inode = sis->swap_file->f_mapping->host;
 969         if (S_ISBLK(inode->i_mode)) {
 970                 ret = add_swap_extent(sis, 0, sis->max, 0);
 971                 *span = sis->pages;
 972                 goto done;
 973         }
 974
 975         blkbits = inode->i_blkbits;
 976         blocks_per_page = PAGE_SIZE >> blkbits;
 977
 978         /*
 979          * Map all the blocks into the extent list.  This code doesn't try
 980          * to be very smart.
 981          */
 982         probe_block = 0;
 983         page_no = 0;
 984         last_block = i_size_read(inode) >> blkbits;
 985         while ((probe_block + blocks_per_page) <= last_block &&
 986                         page_no < sis->max) {
 987                 unsigned block_in_page;
 988                 sector_t first_block;
 989
 990                 first_block = bmap(inode, probe_block);
 991                 if (first_block == 0)
 992                         goto bad_bmap;
 993
 994                 /*
 995                  * It must be PAGE_SIZE aligned on-disk
 996                  */
 997                 if (first_block & (blocks_per_page - 1)) {
 998                         probe_block++;
 999                         goto reprobe;
1000                 }
1001
1002                 for (block_in_page = 1; block_in_page < blocks_per_page;
1003                                         block_in_page++) {
1004                         sector_t block;
1005
1006                         block = bmap(inode, probe_block + block_in_page);
1007                         if (block == 0)
1008                                 goto bad_bmap;
1009                         if (block != first_block + block_in_page) {
1010                                 /* Discontiguity */
1011                                 probe_block++;
1012                                 goto reprobe;
1013                         }
1014                 }
1015
1016                 first_block >>= (PAGE_SHIFT - blkbits);
1017                 if (page_no) {  /* exclude the header page */
1018                         if (first_block < lowest_block)
1019                                 lowest_block = first_block;
1020                         if (first_block > highest_block)
1021                                 highest_block = first_block;
1022                 }
1023
1024                 /*
1025                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1026                  */
1027                 ret = add_swap_extent(sis, page_no, 1, first_block);
1028                 if (ret < 0)
1029                         goto out;
1030                 nr_extents += ret;
1031                 page_no++;
1032                 probe_block += blocks_per_page;
1033 reprobe:
1034                 continue;
1035         }
1036         ret = nr_extents;
1037         *span = 1 + highest_block - lowest_block;
1038         if (page_no == 0)
1039                 page_no = 1;    /* force Empty message */
1040         sis->max = page_no;
1041         sis->pages = page_no - 1;
1042         sis->highest_bit = page_no - 1;
1043 done:
1044         sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1045                                         struct swap_extent, list);
1046         goto out;
1047 bad_bmap:
1048         printk(KERN_ERR "swapon: swapfile has holes\n");
1049         ret = -EINVAL;
1050 out:
1051         return ret;
1052 }
1053
1054 #if 0   /* We don't need this yet */
1055 #include <linux/backing-dev.h>
1056 int page_queue_congested(struct page *page)
1057 {
1058         struct backing_dev_info *bdi;
1059
1060         BUG_ON(!PageLocked(page));      /* It pins the swap_info_struct */
1061
1062         if (PageSwapCache(page)) {
1063                 swp_entry_t entry = { .val = page_private(page) };
1064                 struct swap_info_struct *sis;
1065
1066                 sis = get_swap_info_struct(swp_type(entry));
1067                 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1068         } else
1069                 bdi = page->mapping->backing_dev_info;
1070         return bdi_write_congested(bdi);
1071 }
1072 #endif
1073
1074 asmlinkage long sys_swapoff(const char __user * specialfile)
1075 {
1076         struct swap_info_struct * p = NULL;
1077         unsigned short *swap_map;
1078         struct file *swap_file, *victim;
1079         struct address_space *mapping;
1080         struct inode *inode;
1081         char * pathname;
1082         int i, type, prev;
1083         int err;
1084
1085         if (!capable(CAP_SYS_ADMIN))
1086                 return -EPERM;
1087
1088         pathname = getname(specialfile);
1089         err = PTR_ERR(pathname);
1090         if (IS_ERR(pathname))
1091                 goto out;
1092
1093         victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1094         putname(pathname);
1095         err = PTR_ERR(victim);
1096         if (IS_ERR(victim))
1097                 goto out;
1098
1099         mapping = victim->f_mapping;
1100         prev = -1;
1101         spin_lock(&swap_lock);
1102         for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1103                 p = swap_info + type;
1104                 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
1105                         if (p->swap_file->f_mapping == mapping)
1106                                 break;
1107                 }
1108                 prev = type;
1109         }
1110         if (type < 0) {
1111                 err = -EINVAL;
1112                 spin_unlock(&swap_lock);
1113                 goto out_dput;
1114         }
1115         if (!security_vm_enough_memory(p->pages))
1116                 vm_unacct_memory(p->pages);
1117         else {
1118                 err = -ENOMEM;
1119                 spin_unlock(&swap_lock);
1120                 goto out_dput;
1121         }
1122         if (prev < 0) {
1123                 swap_list.head = p->next;
1124         } else {
1125                 swap_info[prev].next = p->next;
1126         }
1127         if (type == swap_list.next) {
1128                 /* just pick something that's safe... */
1129                 swap_list.next = swap_list.head;
1130         }
1131         nr_swap_pages -= p->pages;
1132         total_swap_pages -= p->pages;
1133         p->flags &= ~SWP_WRITEOK;
1134         spin_unlock(&swap_lock);
1135
1136         current->flags |= PF_SWAPOFF;
1137         err = try_to_unuse(type);
1138         current->flags &= ~PF_SWAPOFF;
1139
1140         if (err) {
1141                 /* re-insert swap space back into swap_list */
1142                 spin_lock(&swap_lock);
1143                 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
1144                         if (p->prio >= swap_info[i].prio)
1145                                 break;
1146                 p->next = i;
1147                 if (prev < 0)
1148                         swap_list.head = swap_list.next = p - swap_info;
1149                 else
1150                         swap_info[prev].next = p - swap_info;
1151                 nr_swap_pages += p->pages;
1152                 total_swap_pages += p->pages;
1153                 p->flags |= SWP_WRITEOK;
1154                 spin_unlock(&swap_lock);
1155                 goto out_dput;
1156         }
1157
1158         /* wait for any unplug function to finish */
1159         down_write(&swap_unplug_sem);
1160         up_write(&swap_unplug_sem);
1161
1162         destroy_swap_extents(p);
1163         down(&swapon_sem);
1164         spin_lock(&swap_lock);
1165         drain_mmlist();
1166
1167         /* wait for anyone still in scan_swap_map */
1168         p->highest_bit = 0;             /* cuts scans short */
1169         while (p->flags >= SWP_SCANNING) {
1170                 spin_unlock(&swap_lock);
1171                 schedule_timeout_uninterruptible(1);
1172                 spin_lock(&swap_lock);
1173         }
1174
1175         swap_file = p->swap_file;
1176         p->swap_file = NULL;
1177         p->max = 0;
1178         swap_map = p->swap_map;
1179         p->swap_map = NULL;
1180         p->flags = 0;
1181         spin_unlock(&swap_lock);
1182         up(&swapon_sem);
1183         vfree(swap_map);
1184         inode = mapping->host;
1185         if (S_ISBLK(inode->i_mode)) {
1186                 struct block_device *bdev = I_BDEV(inode);
1187                 set_blocksize(bdev, p->old_block_size);
1188                 bd_release(bdev);
1189         } else {
1190                 down(&inode->i_sem);
1191                 inode->i_flags &= ~S_SWAPFILE;
1192                 up(&inode->i_sem);
1193         }
1194         filp_close(swap_file, NULL);
1195         err = 0;
1196
1197 out_dput:
1198         filp_close(victim, NULL);
1199 out:
1200         return err;
1201 }
1202
1203 #ifdef CONFIG_PROC_FS
1204 /* iterator */
1205 static void *swap_start(struct seq_file *swap, loff_t *pos)
1206 {
1207         struct swap_info_struct *ptr = swap_info;
1208         int i;
1209         loff_t l = *pos;
1210
1211         down(&swapon_sem);
1212
1213         for (i = 0; i < nr_swapfiles; i++, ptr++) {
1214                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1215                         continue;
1216                 if (!l--)
1217                         return ptr;
1218         }
1219
1220         return NULL;
1221 }
1222
1223 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1224 {
1225         struct swap_info_struct *ptr = v;
1226         struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1227
1228         for (++ptr; ptr < endptr; ptr++) {
1229                 if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1230                         continue;
1231                 ++*pos;
1232                 return ptr;
1233         }
1234
1235         return NULL;
1236 }
1237
1238 static void swap_stop(struct seq_file *swap, void *v)
1239 {
1240         up(&swapon_sem);
1241 }
1242
1243 static int swap_show(struct seq_file *swap, void *v)
1244 {
1245         struct swap_info_struct *ptr = v;
1246         struct file *file;
1247         int len;
1248
1249         if (v == swap_info)
1250                 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1251
1252         file = ptr->swap_file;
1253         len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\");
1254         seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1255                        len < 40 ? 40 - len : 1, " ",
1256                        S_ISBLK(file->f_dentry->d_inode->i_mode) ?
1257                                 "partition" : "file\t",
1258                        ptr->pages << (PAGE_SHIFT - 10),
1259                        ptr->inuse_pages << (PAGE_SHIFT - 10),
1260                        ptr->prio);
1261         return 0;
1262 }
1263
1264 static struct seq_operations swaps_op = {
1265         .start =        swap_start,
1266         .next =         swap_next,
1267         .stop =         swap_stop,
1268         .show =         swap_show
1269 };
1270
1271 static int swaps_open(struct inode *inode, struct file *file)
1272 {
1273         return seq_open(file, &swaps_op);
1274 }
1275
1276 static struct file_operations proc_swaps_operations = {
1277         .open           = swaps_open,
1278         .read           = seq_read,
1279         .llseek         = seq_lseek,
1280         .release        = seq_release,
1281 };
1282
1283 static int __init procswaps_init(void)
1284 {
1285         struct proc_dir_entry *entry;
1286
1287         entry = create_proc_entry("swaps", 0, NULL);
1288         if (entry)
1289                 entry->proc_fops = &proc_swaps_operations;
1290         return 0;
1291 }
1292 __initcall(procswaps_init);
1293 #endif /* CONFIG_PROC_FS */
1294
1295 /*
1296  * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1297  *
1298  * The swapon system call
1299  */
1300 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1301 {
1302         struct swap_info_struct * p;
1303         char *name = NULL;
1304         struct block_device *bdev = NULL;
1305         struct file *swap_file = NULL;
1306         struct address_space *mapping;
1307         unsigned int type;
1308         int i, prev;
1309         int error;
1310         static int least_priority;
1311         union swap_header *swap_header = NULL;
1312         int swap_header_version;
1313         unsigned int nr_good_pages = 0;
1314         int nr_extents = 0;
1315         sector_t span;
1316         unsigned long maxpages = 1;
1317         int swapfilesize;
1318         unsigned short *swap_map;
1319         struct page *page = NULL;
1320         struct inode *inode = NULL;
1321         int did_down = 0;
1322
1323         if (!capable(CAP_SYS_ADMIN))
1324                 return -EPERM;
1325         spin_lock(&swap_lock);
1326         p = swap_info;
1327         for (type = 0 ; type < nr_swapfiles ; type++,p++)
1328                 if (!(p->flags & SWP_USED))
1329                         break;
1330         error = -EPERM;
1331         /*
1332          * Test if adding another swap device is possible. There are
1333          * two limiting factors: 1) the number of bits for the swap
1334          * type swp_entry_t definition and 2) the number of bits for
1335          * the swap type in the swap ptes as defined by the different
1336          * architectures. To honor both limitations a swap entry
1337          * with swap offset 0 and swap type ~0UL is created, encoded
1338          * to a swap pte, decoded to a swp_entry_t again and finally
1339          * the swap type part is extracted. This will mask all bits
1340          * from the initial ~0UL that can't be encoded in either the
1341          * swp_entry_t or the architecture definition of a swap pte.
1342          */
1343         if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) {
1344                 spin_unlock(&swap_lock);
1345                 goto out;
1346         }
1347         if (type >= nr_swapfiles)
1348                 nr_swapfiles = type+1;
1349         INIT_LIST_HEAD(&p->extent_list);
1350         p->flags = SWP_USED;
1351         p->swap_file = NULL;
1352         p->old_block_size = 0;
1353         p->swap_map = NULL;
1354         p->lowest_bit = 0;
1355         p->highest_bit = 0;
1356         p->cluster_nr = 0;
1357         p->inuse_pages = 0;
1358         p->next = -1;
1359         if (swap_flags & SWAP_FLAG_PREFER) {
1360                 p->prio =
1361                   (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
1362         } else {
1363                 p->prio = --least_priority;
1364         }
1365         spin_unlock(&swap_lock);
1366         name = getname(specialfile);
1367         error = PTR_ERR(name);
1368         if (IS_ERR(name)) {
1369                 name = NULL;
1370                 goto bad_swap_2;
1371         }
1372         swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1373         error = PTR_ERR(swap_file);
1374         if (IS_ERR(swap_file)) {
1375                 swap_file = NULL;
1376                 goto bad_swap_2;
1377         }
1378
1379         p->swap_file = swap_file;
1380         mapping = swap_file->f_mapping;
1381         inode = mapping->host;
1382
1383         error = -EBUSY;
1384         for (i = 0; i < nr_swapfiles; i++) {
1385                 struct swap_info_struct *q = &swap_info[i];
1386
1387                 if (i == type || !q->swap_file)
1388                         continue;
1389                 if (mapping == q->swap_file->f_mapping)
1390                         goto bad_swap;
1391         }
1392
1393         error = -EINVAL;
1394         if (S_ISBLK(inode->i_mode)) {
1395                 bdev = I_BDEV(inode);
1396                 error = bd_claim(bdev, sys_swapon);
1397                 if (error < 0) {
1398                         bdev = NULL;
1399                         error = -EINVAL;
1400                         goto bad_swap;
1401                 }
1402                 p->old_block_size = block_size(bdev);
1403                 error = set_blocksize(bdev, PAGE_SIZE);
1404                 if (error < 0)
1405                         goto bad_swap;
1406                 p->bdev = bdev;
1407         } else if (S_ISREG(inode->i_mode)) {
1408                 p->bdev = inode->i_sb->s_bdev;
1409                 down(&inode->i_sem);
1410                 did_down = 1;
1411                 if (IS_SWAPFILE(inode)) {
1412                         error = -EBUSY;
1413                         goto bad_swap;
1414                 }
1415         } else {
1416                 goto bad_swap;
1417         }
1418
1419         swapfilesize = i_size_read(inode) >> PAGE_SHIFT;
1420
1421         /*
1422          * Read the swap header.
1423          */
1424         if (!mapping->a_ops->readpage) {
1425                 error = -EINVAL;
1426                 goto bad_swap;
1427         }
1428         page = read_cache_page(mapping, 0,
1429                         (filler_t *)mapping->a_ops->readpage, swap_file);
1430         if (IS_ERR(page)) {
1431                 error = PTR_ERR(page);
1432                 goto bad_swap;
1433         }
1434         wait_on_page_locked(page);
1435         if (!PageUptodate(page))
1436                 goto bad_swap;
1437         kmap(page);
1438         swap_header = page_address(page);
1439
1440         if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
1441                 swap_header_version = 1;
1442         else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
1443                 swap_header_version = 2;
1444         else {
1445                 printk("Unable to find swap-space signature\n");
1446                 error = -EINVAL;
1447                 goto bad_swap;
1448         }
1449
1450         switch (swap_header_version) {
1451         case 1:
1452                 printk(KERN_ERR "version 0 swap is no longer supported. "
1453                         "Use mkswap -v1 %s\n", name);
1454                 error = -EINVAL;
1455                 goto bad_swap;
1456         case 2:
1457                 /* Check the swap header's sub-version and the size of
1458                    the swap file and bad block lists */
1459                 if (swap_header->info.version != 1) {
1460                         printk(KERN_WARNING
1461                                "Unable to handle swap header version %d\n",
1462                                swap_header->info.version);
1463                         error = -EINVAL;
1464                         goto bad_swap;
1465                 }
1466
1467                 p->lowest_bit  = 1;
1468                 p->cluster_next = 1;
1469
1470                 /*
1471                  * Find out how many pages are allowed for a single swap
1472                  * device. There are two limiting factors: 1) the number of
1473                  * bits for the swap offset in the swp_entry_t type and
1474                  * 2) the number of bits in the a swap pte as defined by
1475                  * the different architectures. In order to find the
1476                  * largest possible bit mask a swap entry with swap type 0
1477                  * and swap offset ~0UL is created, encoded to a swap pte,
1478                  * decoded to a swp_entry_t again and finally the swap
1479                  * offset is extracted. This will mask all the bits from
1480                  * the initial ~0UL mask that can't be encoded in either
1481                  * the swp_entry_t or the architecture definition of a
1482                  * swap pte.
1483                  */
1484                 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
1485                 if (maxpages > swap_header->info.last_page)
1486                         maxpages = swap_header->info.last_page;
1487                 p->highest_bit = maxpages - 1;
1488
1489                 error = -EINVAL;
1490                 if (!maxpages)
1491                         goto bad_swap;
1492                 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1493                         goto bad_swap;
1494                 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1495                         goto bad_swap;
1496
1497                 /* OK, set up the swap map and apply the bad block list */
1498                 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
1499                         error = -ENOMEM;
1500                         goto bad_swap;
1501                 }
1502
1503                 error = 0;
1504                 memset(p->swap_map, 0, maxpages * sizeof(short));
1505                 for (i = 0; i < swap_header->info.nr_badpages; i++) {
1506                         int page_nr = swap_header->info.badpages[i];
1507                         if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
1508                                 error = -EINVAL;
1509                         else
1510                                 p->swap_map[page_nr] = SWAP_MAP_BAD;
1511                 }
1512                 nr_good_pages = swap_header->info.last_page -
1513                                 swap_header->info.nr_badpages -
1514                                 1 /* header page */;
1515                 if (error)
1516                         goto bad_swap;
1517         }
1518
1519         if (swapfilesize && maxpages > swapfilesize) {
1520                 printk(KERN_WARNING
1521                        "Swap area shorter than signature indicates\n");
1522                 error = -EINVAL;
1523                 goto bad_swap;
1524         }
1525         if (nr_good_pages) {
1526                 p->swap_map[0] = SWAP_MAP_BAD;
1527                 p->max = maxpages;
1528                 p->pages = nr_good_pages;
1529                 nr_extents = setup_swap_extents(p, &span);
1530                 if (nr_extents < 0) {
1531                         error = nr_extents;
1532                         goto bad_swap;
1533                 }
1534                 nr_good_pages = p->pages;
1535         }
1536         if (!nr_good_pages) {
1537                 printk(KERN_WARNING "Empty swap-file\n");
1538                 error = -EINVAL;
1539                 goto bad_swap;
1540         }
1541
1542         down(&swapon_sem);
1543         spin_lock(&swap_lock);
1544         p->flags = SWP_ACTIVE;
1545         nr_swap_pages += nr_good_pages;
1546         total_swap_pages += nr_good_pages;
1547
1548         printk(KERN_INFO "Adding %uk swap on %s.  "
1549                         "Priority:%d extents:%d across:%lluk\n",
1550                 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1551                 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
1552
1553         /* insert swap space into swap_list: */
1554         prev = -1;
1555         for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1556                 if (p->prio >= swap_info[i].prio) {
1557                         break;
1558                 }
1559                 prev = i;
1560         }
1561         p->next = i;
1562         if (prev < 0) {
1563                 swap_list.head = swap_list.next = p - swap_info;
1564         } else {
1565                 swap_info[prev].next = p - swap_info;
1566         }
1567         spin_unlock(&swap_lock);
1568         up(&swapon_sem);
1569         error = 0;
1570         goto out;
1571 bad_swap:
1572         if (bdev) {
1573                 set_blocksize(bdev, p->old_block_size);
1574                 bd_release(bdev);
1575         }
1576         destroy_swap_extents(p);
1577 bad_swap_2:
1578         spin_lock(&swap_lock);
1579         swap_map = p->swap_map;
1580         p->swap_file = NULL;
1581         p->swap_map = NULL;
1582         p->flags = 0;
1583         if (!(swap_flags & SWAP_FLAG_PREFER))
1584                 ++least_priority;
1585         spin_unlock(&swap_lock);
1586         vfree(swap_map);
1587         if (swap_file)
1588                 filp_close(swap_file, NULL);
1589 out:
1590         if (page && !IS_ERR(page)) {
1591                 kunmap(page);
1592                 page_cache_release(page);
1593         }
1594         if (name)
1595                 putname(name);
1596         if (did_down) {
1597                 if (!error)
1598                         inode->i_flags |= S_SWAPFILE;
1599                 up(&inode->i_sem);
1600         }
1601         return error;
1602 }
1603
1604 void si_swapinfo(struct sysinfo *val)
1605 {
1606         unsigned int i;
1607         unsigned long nr_to_be_unused = 0;
1608
1609         spin_lock(&swap_lock);
1610         for (i = 0; i < nr_swapfiles; i++) {
1611                 if (!(swap_info[i].flags & SWP_USED) ||
1612                      (swap_info[i].flags & SWP_WRITEOK))
1613                         continue;
1614                 nr_to_be_unused += swap_info[i].inuse_pages;
1615         }
1616         val->freeswap = nr_swap_pages + nr_to_be_unused;
1617         val->totalswap = total_swap_pages + nr_to_be_unused;
1618         spin_unlock(&swap_lock);
1619 }
1620
1621 /*
1622  * Verify that a swap entry is valid and increment its swap map count.
1623  *
1624  * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1625  * "permanent", but will be reclaimed by the next swapoff.
1626  */
1627 int swap_duplicate(swp_entry_t entry)
1628 {
1629         struct swap_info_struct * p;
1630         unsigned long offset, type;
1631         int result = 0;
1632
1633         type = swp_type(entry);
1634         if (type >= nr_swapfiles)
1635                 goto bad_file;
1636         p = type + swap_info;
1637         offset = swp_offset(entry);
1638
1639         spin_lock(&swap_lock);
1640         if (offset < p->max && p->swap_map[offset]) {
1641                 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1642                         p->swap_map[offset]++;
1643                         result = 1;
1644                 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1645                         if (swap_overflow++ < 5)
1646                                 printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1647                         p->swap_map[offset] = SWAP_MAP_MAX;
1648                         result = 1;
1649                 }
1650         }
1651         spin_unlock(&swap_lock);
1652 out:
1653         return result;
1654
1655 bad_file:
1656         printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1657         goto out;
1658 }
1659
1660 struct swap_info_struct *
1661 get_swap_info_struct(unsigned type)
1662 {
1663         return &swap_info[type];
1664 }
1665
1666 /*
1667  * swap_lock prevents swap_map being freed. Don't grab an extra
1668  * reference on the swaphandle, it doesn't matter if it becomes unused.
1669  */
1670 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1671 {
1672         int ret = 0, i = 1 << page_cluster;
1673         unsigned long toff;
1674         struct swap_info_struct *swapdev = swp_type(entry) + swap_info;
1675
1676         if (!page_cluster)      /* no readahead */
1677                 return 0;
1678         toff = (swp_offset(entry) >> page_cluster) << page_cluster;
1679         if (!toff)              /* first page is swap header */
1680                 toff++, i--;
1681         *offset = toff;
1682
1683         spin_lock(&swap_lock);
1684         do {
1685                 /* Don't read-ahead past the end of the swap area */
1686                 if (toff >= swapdev->max)
1687                         break;
1688                 /* Don't read in free or bad pages */
1689                 if (!swapdev->swap_map[toff])
1690                         break;
1691                 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
1692                         break;
1693                 toff++;
1694                 ret++;
1695         } while (--i);
1696         spin_unlock(&swap_lock);
1697         return ret;
1698 }