mm/swapfile.c

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