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/malloc.h>
   9 #include <linux/smp_lock.h>
  10 #include <linux/kernel_stat.h>
  11 #include <linux/swap.h>
  12 #include <linux/swapctl.h>
  13 #include <linux/blkdev.h> /* for blk_size */
  14 #include <linux/vmalloc.h>
  15 #include <linux/pagemap.h>
  16 #include <linux/shm.h>
  17
  18 #include <asm/pgtable.h>
  19
  20 spinlock_t swaplock = SPIN_LOCK_UNLOCKED;
  21 unsigned int nr_swapfiles;
  22
  23 struct swap_list_t swap_list = {-1, -1};
  24
  25 struct swap_info_struct swap_info[MAX_SWAPFILES];
  26
  27 #define SWAPFILE_CLUSTER 256
  28
  29 static inline int scan_swap_map(struct swap_info_struct *si, unsigned short count)
  30 {
  31         unsigned long offset;
  32         /*
  33          * We try to cluster swap pages by allocating them
  34          * sequentially in swap.  Once we've allocated
  35          * SWAPFILE_CLUSTER pages this way, however, we resort to
  36          * first-free allocation, starting a new cluster.  This
  37          * prevents us from scattering swap pages all over the entire
  38          * swap partition, so that we reduce overall disk seek times
  39          * between swap pages.  -- sct */
  40         if (si->cluster_nr) {
  41                 while (si->cluster_next <= si->highest_bit) {
  42                         offset = si->cluster_next++;
  43                         if (si->swap_map[offset])
  44                                 continue;
  45                         si->cluster_nr--;
  46                         goto got_page;
  47                 }
  48         }
  49         si->cluster_nr = SWAPFILE_CLUSTER;
  50
  51         /* try to find an empty (even not aligned) cluster. */
  52         offset = si->lowest_bit;
  53  check_next_cluster:
  54         if (offset+SWAPFILE_CLUSTER-1 <= si->highest_bit)
  55         {
  56                 int nr;
  57                 for (nr = offset; nr < offset+SWAPFILE_CLUSTER; nr++)
  58                         if (si->swap_map[nr])
  59                         {
  60                                 offset = nr+1;
  61                                 goto check_next_cluster;
  62                         }
  63                 /* We found a completly empty cluster, so start
  64                  * using it.
  65                  */
  66                 goto got_page;
  67         }
  68         /* No luck, so now go finegrined as usual. -Andrea */
  69         for (offset = si->lowest_bit; offset <= si->highest_bit ; offset++) {
  70                 if (si->swap_map[offset])
  71                         continue;
  72         got_page:
  73                 if (offset == si->lowest_bit)
  74                         si->lowest_bit++;
  75                 if (offset == si->highest_bit)
  76                         si->highest_bit--;
  77                 si->swap_map[offset] = count;
  78                 nr_swap_pages--;
  79                 si->cluster_next = offset+1;
  80                 return offset;
  81         }
  82         return 0;
  83 }
  84
  85 swp_entry_t __get_swap_page(unsigned short count)
  86 {
  87         struct swap_info_struct * p;
  88         unsigned long offset;
  89         swp_entry_t entry;
  90         int type, wrapped = 0;
  91
  92         entry.val = 0;  /* Out of memory */
  93         if (count >= SWAP_MAP_MAX)
  94                 goto bad_count;
  95         swap_list_lock();
  96         type = swap_list.next;
  97         if (type < 0)
  98                 goto out;
  99         if (nr_swap_pages == 0)
 100                 goto out;
 101
 102         while (1) {
 103                 p = &swap_info[type];
 104                 if ((p->flags & SWP_WRITEOK) == SWP_WRITEOK) {
 105                         swap_device_lock(p);
 106                         offset = scan_swap_map(p, count);
 107                         swap_device_unlock(p);
 108                         if (offset) {
 109                                 entry = SWP_ENTRY(type,offset);
 110                                 type = swap_info[type].next;
 111                                 if (type < 0 ||
 112                                         p->prio != swap_info[type].prio) {
 113                                                 swap_list.next = swap_list.head;
 114                                 } else {
 115                                         swap_list.next = type;
 116                                 }
 117                                 goto out;
 118                         }
 119                 }
 120                 type = p->next;
 121                 if (!wrapped) {
 122                         if (type < 0 || p->prio != swap_info[type].prio) {
 123                                 type = swap_list.head;
 124                                 wrapped = 1;
 125                         }
 126                 } else
 127                         if (type < 0)
 128                                 goto out;       /* out of swap space */
 129         }
 130 out:
 131         swap_list_unlock();
 132         return entry;
 133
 134 bad_count:
 135         printk(KERN_ERR "get_swap_page: bad count %hd from %p\n",
 136                count, __builtin_return_address(0));
 137         goto out;
 138 }
 139
 140
 141 /*
 142  * Caller has made sure that the swapdevice corresponding to entry
 143  * is still around or has not been recycled.
 144  */
 145 void __swap_free(swp_entry_t entry, unsigned short count)
 146 {
 147         struct swap_info_struct * p;
 148         unsigned long offset, type;
 149
 150         if (!entry.val)
 151                 goto out;
 152
 153         type = SWP_TYPE(entry);
 154         if (type >= nr_swapfiles)
 155                 goto bad_nofile;
 156         p = & swap_info[type];
 157         if (!(p->flags & SWP_USED))
 158                 goto bad_device;
 159         offset = SWP_OFFSET(entry);
 160         if (offset >= p->max)
 161                 goto bad_offset;
 162         if (!p->swap_map[offset])
 163                 goto bad_free;
 164         swap_list_lock();
 165         if (p->prio > swap_info[swap_list.next].prio)
 166                 swap_list.next = type;
 167         swap_device_lock(p);
 168         if (p->swap_map[offset] < SWAP_MAP_MAX) {
 169                 if (p->swap_map[offset] < count)
 170                         goto bad_count;
 171                 if (!(p->swap_map[offset] -= count)) {
 172                         if (offset < p->lowest_bit)
 173                                 p->lowest_bit = offset;
 174                         if (offset > p->highest_bit)
 175                                 p->highest_bit = offset;
 176                         nr_swap_pages++;
 177                 }
 178         }
 179         swap_device_unlock(p);
 180         swap_list_unlock();
 181 out:
 182         return;
 183
 184 bad_nofile:
 185         printk("swap_free: Trying to free nonexistent swap-page\n");
 186         goto out;
 187 bad_device:
 188         printk("swap_free: Trying to free swap from unused swap-device\n");
 189         goto out;
 190 bad_offset:
 191         printk("swap_free: offset exceeds max\n");
 192         goto out;
 193 bad_free:
 194         printk("VM: Bad swap entry %08lx\n", entry.val);
 195         goto out;
 196 bad_count:
 197         swap_device_unlock(p);
 198         swap_list_unlock();
 199         printk(KERN_ERR "VM: Bad count %hd current count %hd\n", count, p->swap_map[offset]);
 200         goto out;
 201 }
 202
 203 /*
 204  * The swap entry has been read in advance, and we return 1 to indicate
 205  * that the page has been used or is no longer needed.
 206  *
 207  * Always set the resulting pte to be nowrite (the same as COW pages
 208  * after one process has exited).  We don't know just how many PTEs will
 209  * share this swap entry, so be cautious and let do_wp_page work out
 210  * what to do if a write is requested later.
 211  */
 212 static inline void unuse_pte(struct vm_area_struct * vma, unsigned long address,
 213         pte_t *dir, swp_entry_t entry, struct page* page)
 214 {
 215         pte_t pte = *dir;
 216
 217         if (pte_none(pte))
 218                 return;
 219         if (pte_present(pte)) {
 220                 /* If this entry is swap-cached, then page must already
 221                    hold the right address for any copies in physical
 222                    memory */
 223                 if (pte_page(pte) != page)
 224                         return;
 225                 /* We will be removing the swap cache in a moment, so... */
 226                 ptep_mkdirty(dir);
 227                 return;
 228         }
 229         if (pte_to_swp_entry(pte).val != entry.val)
 230                 return;
 231         set_pte(dir, pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
 232         swap_free(entry);
 233         get_page(page);
 234         ++vma->vm_mm->rss;
 235 }
 236
 237 static inline void unuse_pmd(struct vm_area_struct * vma, pmd_t *dir,
 238         unsigned long address, unsigned long size, unsigned long offset,
 239         swp_entry_t entry, struct page* page)
 240 {
 241         pte_t * pte;
 242         unsigned long end;
 243
 244         if (pmd_none(*dir))
 245                 return;
 246         if (pmd_bad(*dir)) {
 247                 pmd_ERROR(*dir);
 248                 pmd_clear(dir);
 249                 return;
 250         }
 251         pte = pte_offset(dir, address);
 252         offset += address & PMD_MASK;
 253         address &= ~PMD_MASK;
 254         end = address + size;
 255         if (end > PMD_SIZE)
 256                 end = PMD_SIZE;
 257         do {
 258                 unuse_pte(vma, offset+address-vma->vm_start, pte, entry, page);
 259                 address += PAGE_SIZE;
 260                 pte++;
 261         } while (address && (address < end));
 262 }
 263
 264 static inline void unuse_pgd(struct vm_area_struct * vma, pgd_t *dir,
 265         unsigned long address, unsigned long size,
 266         swp_entry_t entry, struct page* page)
 267 {
 268         pmd_t * pmd;
 269         unsigned long offset, end;
 270
 271         if (pgd_none(*dir))
 272                 return;
 273         if (pgd_bad(*dir)) {
 274                 pgd_ERROR(*dir);
 275                 pgd_clear(dir);
 276                 return;
 277         }
 278         pmd = pmd_offset(dir, address);
 279         offset = address & PGDIR_MASK;
 280         address &= ~PGDIR_MASK;
 281         end = address + size;
 282         if (end > PGDIR_SIZE)
 283                 end = PGDIR_SIZE;
 284         if (address >= end)
 285                 BUG();
 286         do {
 287                 unuse_pmd(vma, pmd, address, end - address, offset, entry,
 288                           page);
 289                 address = (address + PMD_SIZE) & PMD_MASK;
 290                 pmd++;
 291         } while (address && (address < end));
 292 }
 293
 294 static void unuse_vma(struct vm_area_struct * vma, pgd_t *pgdir,
 295                         swp_entry_t entry, struct page* page)
 296 {
 297         unsigned long start = vma->vm_start, end = vma->vm_end;
 298
 299         if (start >= end)
 300                 BUG();
 301         do {
 302                 unuse_pgd(vma, pgdir, start, end - start, entry, page);
 303                 start = (start + PGDIR_SIZE) & PGDIR_MASK;
 304                 pgdir++;
 305         } while (start && (start < end));
 306 }
 307
 308 static void unuse_process(struct mm_struct * mm,
 309                         swp_entry_t entry, struct page* page)
 310 {
 311         struct vm_area_struct* vma;
 312
 313         /*
 314          * Go through process' page directory.
 315          */
 316         if (!mm)
 317                 return;
 318         spin_lock(&mm->page_table_lock);
 319         for (vma = mm->mmap; vma; vma = vma->vm_next) {
 320                 pgd_t * pgd = pgd_offset(mm, vma->vm_start);
 321                 unuse_vma(vma, pgd, entry, page);
 322         }
 323         spin_unlock(&mm->page_table_lock);
 324         return;
 325 }
 326
 327 /*
 328  * We completely avoid races by reading each swap page in advance,
 329  * and then search for the process using it.  All the necessary
 330  * page table adjustments can then be made atomically.
 331  */
 332 static int try_to_unuse(unsigned int type)
 333 {
 334         struct swap_info_struct * si = &swap_info[type];
 335         struct task_struct *p;
 336         struct page *page;
 337         swp_entry_t entry;
 338         int i;
 339
 340         while (1) {
 341                 /*
 342                  * Find a swap page in use and read it in.
 343                  */
 344                 swap_device_lock(si);
 345                 for (i = 1; i < si->max ; i++) {
 346                         if (si->swap_map[i] > 0 && si->swap_map[i] != SWAP_MAP_BAD) {
 347                                 /*
 348                                  * Prevent swaphandle from being completely
 349                                  * unused by swap_free while we are trying
 350                                  * to read in the page - this prevents warning
 351                                  * messages from rw_swap_page_base.
 352                                  */
 353                                 if (si->swap_map[i] != SWAP_MAP_MAX)
 354                                         si->swap_map[i]++;
 355                                 swap_device_unlock(si);
 356                                 goto found_entry;
 357                         }
 358                 }
 359                 swap_device_unlock(si);
 360                 break;
 361
 362         found_entry:
 363                 entry = SWP_ENTRY(type, i);
 364
 365                 /* Get a page for the entry, using the existing swap
 366                    cache page if there is one.  Otherwise, get a clean
 367                    page and read the swap into it. */
 368                 page = read_swap_cache(entry);
 369                 if (!page) {
 370                         swap_free(entry);
 371                         return -ENOMEM;
 372                 }
 373                 if (PageSwapCache(page))
 374                         delete_from_swap_cache(page);
 375                 read_lock(&tasklist_lock);
 376                 for_each_task(p)
 377                         unuse_process(p->mm, entry, page);
 378                 read_unlock(&tasklist_lock);
 379                 shmem_unuse(entry, page);
 380                 /* Now get rid of the extra reference to the temporary
 381                    page we've been using. */
 382                 page_cache_release(page);
 383                 /*
 384                  * Check for and clear any overflowed swap map counts.
 385                  */
 386                 swap_free(entry);
 387                 swap_list_lock();
 388                 swap_device_lock(si);
 389                 if (si->swap_map[i] > 0) {
 390                         if (si->swap_map[i] != SWAP_MAP_MAX)
 391                                 printk("VM: Undead swap entry %08lx\n",
 392                                                                 entry.val);
 393                         nr_swap_pages++;
 394                         si->swap_map[i] = 0;
 395                 }
 396                 swap_device_unlock(si);
 397                 swap_list_unlock();
 398         }
 399         return 0;
 400 }
 401
 402 asmlinkage long sys_swapoff(const char * specialfile)
 403 {
 404         struct swap_info_struct * p = NULL;
 405         struct nameidata nd;
 406         int i, type, prev;
 407         int err;
 408
 409         if (!capable(CAP_SYS_ADMIN))
 410                 return -EPERM;
 411
 412         err = user_path_walk(specialfile, &nd);
 413         if (err)
 414                 goto out;
 415
 416         lock_kernel();
 417         prev = -1;
 418         swap_list_lock();
 419         for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
 420                 p = swap_info + type;
 421                 if ((p->flags & SWP_WRITEOK) == SWP_WRITEOK) {
 422                         if (p->swap_file) {
 423                                 if (p->swap_file == nd.dentry)
 424                                   break;
 425                         } else {
 426                                 if (S_ISBLK(nd.dentry->d_inode->i_mode)
 427                                     && (p->swap_device == nd.dentry->d_inode->i_rdev))
 428                                   break;
 429                         }
 430                 }
 431                 prev = type;
 432         }
 433         err = -EINVAL;
 434         if (type < 0) {
 435                 swap_list_unlock();
 436                 goto out_dput;
 437         }
 438
 439         if (prev < 0) {
 440                 swap_list.head = p->next;
 441         } else {
 442                 swap_info[prev].next = p->next;
 443         }
 444         if (type == swap_list.next) {
 445                 /* just pick something that's safe... */
 446                 swap_list.next = swap_list.head;
 447         }
 448         nr_swap_pages -= p->pages;
 449         swap_list_unlock();
 450         p->flags = SWP_USED;
 451         err = try_to_unuse(type);
 452         if (err) {
 453                 /* re-insert swap space back into swap_list */
 454                 swap_list_lock();
 455                 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
 456                         if (p->prio >= swap_info[i].prio)
 457                                 break;
 458                 p->next = i;
 459                 if (prev < 0)
 460                         swap_list.head = swap_list.next = p - swap_info;
 461                 else
 462                         swap_info[prev].next = p - swap_info;
 463                 nr_swap_pages += p->pages;
 464                 swap_list_unlock();
 465                 p->flags = SWP_WRITEOK;
 466                 goto out_dput;
 467         }
 468         if (p->swap_device)
 469                 blkdev_put(nd.dentry->d_inode->i_bdev, BDEV_SWAP);
 470         path_release(&nd);
 471
 472         nd.dentry = p->swap_file;
 473         p->swap_file = NULL;
 474         nd.mnt = p->swap_vfsmnt;
 475         p->swap_vfsmnt = NULL;
 476         p->swap_device = 0;
 477         vfree(p->swap_map);
 478         p->swap_map = NULL;
 479         p->flags = 0;
 480         err = 0;
 481
 482 out_dput:
 483         unlock_kernel();
 484         path_release(&nd);
 485 out:
 486         return err;
 487 }
 488
 489 int get_swaparea_info(char *buf)
 490 {
 491         char * page = (char *) __get_free_page(GFP_KERNEL);
 492         struct swap_info_struct *ptr = swap_info;
 493         int i, j, len = 0, usedswap;
 494
 495         if (!page)
 496                 return -ENOMEM;
 497
 498         len += sprintf(buf, "Filename\t\t\tType\t\tSize\tUsed\tPriority\n");
 499         for (i = 0 ; i < nr_swapfiles ; i++, ptr++) {
 500                 if (ptr->flags & SWP_USED) {
 501                         char * path = d_path(ptr->swap_file, ptr->swap_vfsmnt,
 502                                                 page, PAGE_SIZE);
 503
 504                         len += sprintf(buf + len, "%-31s ", path);
 505
 506                         if (!ptr->swap_device)
 507                                 len += sprintf(buf + len, "file\t\t");
 508                         else
 509                                 len += sprintf(buf + len, "partition\t");
 510
 511                         usedswap = 0;
 512                         for (j = 0; j < ptr->max; ++j)
 513                                 switch (ptr->swap_map[j]) {
 514                                         case SWAP_MAP_BAD:
 515                                         case 0:
 516                                                 continue;
 517                                         default:
 518                                                 usedswap++;
 519                                 }
 520                         len += sprintf(buf + len, "%d\t%d\t%d\n", ptr->pages << (PAGE_SHIFT - 10),
 521                                 usedswap << (PAGE_SHIFT - 10), ptr->prio);
 522                 }
 523         }
 524         free_page((unsigned long) page);
 525         return len;
 526 }
 527
 528 int is_swap_partition(kdev_t dev) {
 529         struct swap_info_struct *ptr = swap_info;
 530         int i;
 531
 532         for (i = 0 ; i < nr_swapfiles ; i++, ptr++) {
 533                 if (ptr->flags & SWP_USED)
 534                         if (ptr->swap_device == dev)
 535                                 return 1;
 536         }
 537         return 0;
 538 }
 539
 540 /*
 541  * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
 542  *
 543  * The swapon system call
 544  */
 545 asmlinkage long sys_swapon(const char * specialfile, int swap_flags)
 546 {
 547         struct swap_info_struct * p;
 548         struct nameidata nd;
 549         struct inode * swap_inode;
 550         unsigned int type;
 551         int i, j, prev;
 552         int error;
 553         static int least_priority = 0;
 554         union swap_header *swap_header = 0;
 555         int swap_header_version;
 556         int nr_good_pages = 0;
 557         unsigned long maxpages;
 558         int swapfilesize;
 559         struct block_device *bdev = NULL;
 560
 561         if (!capable(CAP_SYS_ADMIN))
 562                 return -EPERM;
 563         lock_kernel();
 564         p = swap_info;
 565         for (type = 0 ; type < nr_swapfiles ; type++,p++)
 566                 if (!(p->flags & SWP_USED))
 567                         break;
 568         error = -EPERM;
 569         if (type >= MAX_SWAPFILES)
 570                 goto out;
 571         if (type >= nr_swapfiles)
 572                 nr_swapfiles = type+1;
 573         p->flags = SWP_USED;
 574         p->swap_file = NULL;
 575         p->swap_vfsmnt = NULL;
 576         p->swap_device = 0;
 577         p->swap_map = NULL;
 578         p->lowest_bit = 0;
 579         p->highest_bit = 0;
 580         p->cluster_nr = 0;
 581         p->sdev_lock = SPIN_LOCK_UNLOCKED;
 582         p->max = 1;
 583         p->next = -1;
 584         if (swap_flags & SWAP_FLAG_PREFER) {
 585                 p->prio =
 586                   (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
 587         } else {
 588                 p->prio = --least_priority;
 589         }
 590         error = user_path_walk(specialfile, &nd);
 591         if (error)
 592                 goto bad_swap_2;
 593
 594         p->swap_file = nd.dentry;
 595         p->swap_vfsmnt = nd.mnt;
 596         swap_inode = nd.dentry->d_inode;
 597         error = -EINVAL;
 598
 599         if (S_ISBLK(swap_inode->i_mode)) {
 600                 kdev_t dev = swap_inode->i_rdev;
 601                 struct block_device_operations *bdops;
 602
 603                 p->swap_device = dev;
 604                 set_blocksize(dev, PAGE_SIZE);
 605
 606                 bdev = swap_inode->i_bdev;
 607                 bdops = devfs_get_ops(devfs_get_handle_from_inode(swap_inode));
 608                 if (bdops) bdev->bd_op = bdops;
 609
 610                 error = blkdev_get(bdev, FMODE_READ|FMODE_WRITE, 0, BDEV_SWAP);
 611                 if (error)
 612                         goto bad_swap_2;
 613                 set_blocksize(dev, PAGE_SIZE);
 614                 error = -ENODEV;
 615                 if (!dev || (blk_size[MAJOR(dev)] &&
 616                      !blk_size[MAJOR(dev)][MINOR(dev)]))
 617                         goto bad_swap;
 618                 error = -EBUSY;
 619                 for (i = 0 ; i < nr_swapfiles ; i++) {
 620                         if (i == type)
 621                                 continue;
 622                         if (dev == swap_info[i].swap_device)
 623                                 goto bad_swap;
 624                 }
 625                 swapfilesize = 0;
 626                 if (blk_size[MAJOR(dev)])
 627                         swapfilesize = blk_size[MAJOR(dev)][MINOR(dev)]
 628                                 >> (PAGE_SHIFT - 10);
 629         } else if (S_ISREG(swap_inode->i_mode)) {
 630                 error = -EBUSY;
 631                 for (i = 0 ; i < nr_swapfiles ; i++) {
 632                         if (i == type || !swap_info[i].swap_file)
 633                                 continue;
 634                         if (swap_inode == swap_info[i].swap_file->d_inode)
 635                                 goto bad_swap;
 636                 }
 637                 swapfilesize = swap_inode->i_size >> PAGE_SHIFT;
 638         } else
 639                 goto bad_swap;
 640
 641         swap_header = (void *) __get_free_page(GFP_USER);
 642         if (!swap_header) {
 643                 printk("Unable to start swapping: out of memory :-)\n");
 644                 error = -ENOMEM;
 645                 goto bad_swap;
 646         }
 647
 648         lock_page(virt_to_page(swap_header));
 649         rw_swap_page_nolock(READ, SWP_ENTRY(type,0), (char *) swap_header, 1);
 650
 651         if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
 652                 swap_header_version = 1;
 653         else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
 654                 swap_header_version = 2;
 655         else {
 656                 printk("Unable to find swap-space signature\n");
 657                 error = -EINVAL;
 658                 goto bad_swap;
 659         }
 660
 661         switch (swap_header_version) {
 662         case 1:
 663                 memset(((char *) swap_header)+PAGE_SIZE-10,0,10);
 664                 j = 0;
 665                 p->lowest_bit = 0;
 666                 p->highest_bit = 0;
 667                 for (i = 1 ; i < 8*PAGE_SIZE ; i++) {
 668                         if (test_bit(i,(char *) swap_header)) {
 669                                 if (!p->lowest_bit)
 670                                         p->lowest_bit = i;
 671                                 p->highest_bit = i;
 672                                 p->max = i+1;
 673                                 j++;
 674                         }
 675                 }
 676                 nr_good_pages = j;
 677                 p->swap_map = vmalloc(p->max * sizeof(short));
 678                 if (!p->swap_map) {
 679                         error = -ENOMEM;
 680                         goto bad_swap;
 681                 }
 682                 for (i = 1 ; i < p->max ; i++) {
 683                         if (test_bit(i,(char *) swap_header))
 684                                 p->swap_map[i] = 0;
 685                         else
 686                                 p->swap_map[i] = SWAP_MAP_BAD;
 687                 }
 688                 break;
 689
 690         case 2:
 691                 /* Check the swap header's sub-version and the size of
 692                    the swap file and bad block lists */
 693                 if (swap_header->info.version != 1) {
 694                         printk(KERN_WARNING
 695                                "Unable to handle swap header version %d\n",
 696                                swap_header->info.version);
 697                         error = -EINVAL;
 698                         goto bad_swap;
 699                 }
 700
 701                 p->lowest_bit  = 1;
 702                 p->highest_bit = swap_header->info.last_page - 1;
 703                 p->max         = swap_header->info.last_page;
 704
 705                 maxpages = SWP_OFFSET(SWP_ENTRY(0,~0UL));
 706                 if (p->max >= maxpages)
 707                         p->max = maxpages-1;
 708
 709                 error = -EINVAL;
 710                 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
 711                         goto bad_swap;
 712
 713                 /* OK, set up the swap map and apply the bad block list */
 714                 if (!(p->swap_map = vmalloc (p->max * sizeof(short)))) {
 715                         error = -ENOMEM;
 716                         goto bad_swap;
 717                 }
 718
 719                 error = 0;
 720                 memset(p->swap_map, 0, p->max * sizeof(short));
 721                 for (i=0; i<swap_header->info.nr_badpages; i++) {
 722                         int page = swap_header->info.badpages[i];
 723                         if (page <= 0 || page >= swap_header->info.last_page)
 724                                 error = -EINVAL;
 725                         else
 726                                 p->swap_map[page] = SWAP_MAP_BAD;
 727                 }
 728                 nr_good_pages = swap_header->info.last_page -
 729                                 swap_header->info.nr_badpages -
 730                                 1 /* header page */;
 731                 if (error)
 732                         goto bad_swap;
 733         }
 734
 735         if (swapfilesize && p->max > swapfilesize) {
 736                 printk(KERN_WARNING
 737                        "Swap area shorter than signature indicates\n");
 738                 error = -EINVAL;
 739                 goto bad_swap;
 740         }
 741         if (!nr_good_pages) {
 742                 printk(KERN_WARNING "Empty swap-file\n");
 743                 error = -EINVAL;
 744                 goto bad_swap;
 745         }
 746         p->swap_map[0] = SWAP_MAP_BAD;
 747         p->flags = SWP_WRITEOK;
 748         p->pages = nr_good_pages;
 749         swap_list_lock();
 750         nr_swap_pages += nr_good_pages;
 751         printk(KERN_INFO "Adding Swap: %dk swap-space (priority %d)\n",
 752                nr_good_pages<<(PAGE_SHIFT-10), p->prio);
 753
 754         /* insert swap space into swap_list: */
 755         prev = -1;
 756         for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
 757                 if (p->prio >= swap_info[i].prio) {
 758                         break;
 759                 }
 760                 prev = i;
 761         }
 762         p->next = i;
 763         if (prev < 0) {
 764                 swap_list.head = swap_list.next = p - swap_info;
 765         } else {
 766                 swap_info[prev].next = p - swap_info;
 767         }
 768         swap_list_unlock();
 769         error = 0;
 770         goto out;
 771 bad_swap:
 772         if (bdev)
 773                 blkdev_put(bdev, BDEV_SWAP);
 774 bad_swap_2:
 775         if (p->swap_map)
 776                 vfree(p->swap_map);
 777         nd.mnt = p->swap_vfsmnt;
 778         nd.dentry = p->swap_file;
 779         p->swap_device = 0;
 780         p->swap_file = NULL;
 781         p->swap_vfsmnt = NULL;
 782         p->swap_map = NULL;
 783         p->flags = 0;
 784         if (!(swap_flags & SWAP_FLAG_PREFER))
 785                 ++least_priority;
 786         path_release(&nd);
 787 out:
 788         if (swap_header)
 789                 free_page((long) swap_header);
 790         unlock_kernel();
 791         return error;
 792 }
 793
 794 void si_swapinfo(struct sysinfo *val)
 795 {
 796         unsigned int i;
 797         unsigned long freeswap = 0;
 798         unsigned long totalswap = 0;
 799
 800         for (i = 0; i < nr_swapfiles; i++) {
 801                 unsigned int j;
 802                 if ((swap_info[i].flags & SWP_WRITEOK) != SWP_WRITEOK)
 803                         continue;
 804                 for (j = 0; j < swap_info[i].max; ++j) {
 805                         switch (swap_info[i].swap_map[j]) {
 806                                 case SWAP_MAP_BAD:
 807                                         continue;
 808                                 case 0:
 809                                         freeswap++;
 810                                 default:
 811                                         totalswap++;
 812                         }
 813                 }
 814         }
 815         val->freeswap = freeswap;
 816         val->totalswap = totalswap;
 817         return;
 818 }
 819
 820 /*
 821  * Verify that a swap entry is valid and increment its swap map count.
 822  * Kernel_lock is held, which guarantees existance of swap device.
 823  *
 824  * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
 825  * "permanent", but will be reclaimed by the next swapoff.
 826  */
 827 int swap_duplicate(swp_entry_t entry)
 828 {
 829         struct swap_info_struct * p;
 830         unsigned long offset, type;
 831         int result = 0;
 832
 833         /* Swap entry 0 is illegal */
 834         if (!entry.val)
 835                 goto out;
 836         type = SWP_TYPE(entry);
 837         if (type >= nr_swapfiles)
 838                 goto bad_file;
 839         p = type + swap_info;
 840         offset = SWP_OFFSET(entry);
 841         if (offset >= p->max)
 842                 goto bad_offset;
 843         if (!p->swap_map[offset])
 844                 goto bad_unused;
 845         /*
 846          * Entry is valid, so increment the map count.
 847          */
 848         swap_device_lock(p);
 849         if (p->swap_map[offset] < SWAP_MAP_MAX)
 850                 p->swap_map[offset]++;
 851         else {
 852                 static int overflow = 0;
 853                 if (overflow++ < 5)
 854                         printk("VM: swap entry overflow\n");
 855                 p->swap_map[offset] = SWAP_MAP_MAX;
 856         }
 857         swap_device_unlock(p);
 858         result = 1;
 859 out:
 860         return result;
 861
 862 bad_file:
 863         printk("Bad swap file entry %08lx\n", entry.val);
 864         goto out;
 865 bad_offset:
 866         printk("Bad swap offset entry %08lx\n", entry.val);
 867         goto out;
 868 bad_unused:
 869         printk("Unused swap offset entry in swap_dup %08lx\n", entry.val);
 870         goto out;
 871 }
 872
 873 /*
 874  * Page lock needs to be held in all cases to prevent races with
 875  * swap file deletion.
 876  */
 877 int swap_count(struct page *page)
 878 {
 879         struct swap_info_struct * p;
 880         unsigned long offset, type;
 881         swp_entry_t entry;
 882         int retval = 0;
 883
 884         entry.val = page->index;
 885         if (!entry.val)
 886                 goto bad_entry;
 887         type = SWP_TYPE(entry);
 888         if (type >= nr_swapfiles)
 889                 goto bad_file;
 890         p = type + swap_info;
 891         offset = SWP_OFFSET(entry);
 892         if (offset >= p->max)
 893                 goto bad_offset;
 894         if (!p->swap_map[offset])
 895                 goto bad_unused;
 896         retval = p->swap_map[offset];
 897 out:
 898         return retval;
 899
 900 bad_entry:
 901         printk(KERN_ERR "swap_count: null entry!\n");
 902         goto out;
 903 bad_file:
 904         printk("Bad swap file entry %08lx\n", entry.val);
 905         goto out;
 906 bad_offset:
 907         printk("Bad swap offset entry %08lx\n", entry.val);
 908         goto out;
 909 bad_unused:
 910         printk("Unused swap offset entry in swap_count %08lx\n", entry.val);
 911         goto out;
 912 }
 913
 914 /*
 915  * Kernel_lock protects against swap device deletion.
 916  */
 917 void get_swaphandle_info(swp_entry_t entry, unsigned long *offset,
 918                         kdev_t *dev, struct inode **swapf)
 919 {
 920         unsigned long type;
 921         struct swap_info_struct *p;
 922
 923         type = SWP_TYPE(entry);
 924         if (type >= nr_swapfiles) {
 925                 printk("Internal error: bad swap-device\n");
 926                 return;
 927         }
 928
 929         p = &swap_info[type];
 930         *offset = SWP_OFFSET(entry);
 931         if (*offset >= p->max) {
 932                 printk("rw_swap_page: weirdness\n");
 933                 return;
 934         }
 935         if (p->swap_map && !p->swap_map[*offset]) {
 936                 printk("VM: Bad swap entry %08lx\n", entry.val);
 937                 return;
 938         }
 939         if (!(p->flags & SWP_USED)) {
 940                 printk(KERN_ERR "rw_swap_page: "
 941                         "Trying to swap to unused swap-device\n");
 942                 return;
 943         }
 944
 945         if (p->swap_device) {
 946                 *dev = p->swap_device;
 947         } else if (p->swap_file) {
 948                 *swapf = p->swap_file->d_inode;
 949         } else {
 950                 printk(KERN_ERR "rw_swap_page: no swap file or device\n");
 951         }
 952         return;
 953 }
 954
 955 /*
 956  * Kernel_lock protects against swap device deletion. Grab an extra
 957  * reference on the swaphandle so that it dos not become unused.
 958  */
 959 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
 960 {
 961         int ret = 0, i = 1 << page_cluster;
 962         unsigned long toff;
 963         struct swap_info_struct *swapdev = SWP_TYPE(entry) + swap_info;
 964
 965         *offset = SWP_OFFSET(entry);
 966         toff = *offset = (*offset >> page_cluster) << page_cluster;
 967
 968         swap_device_lock(swapdev);
 969         do {
 970                 /* Don't read-ahead past the end of the swap area */
 971                 if (toff >= swapdev->max)
 972                         break;
 973                 /* Don't read in bad or busy pages */
 974                 if (!swapdev->swap_map[toff])
 975                         break;
 976                 if (swapdev->swap_map[toff] == SWAP_MAP_BAD)
 977                         break;
 978                 swapdev->swap_map[toff]++;
 979                 toff++;
 980                 ret++;
 981         } while (--i);
 982         swap_device_unlock(swapdev);
 983         return ret;
 984 }