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