swapfile.c revision 9b65ef59d42a56fa1358958ede77aaa5bac385a8
1/* 2 * linux/mm/swapfile.c 3 * 4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 5 * Swap reorganised 29.12.95, Stephen Tweedie 6 */ 7 8#include <linux/config.h> 9#include <linux/mm.h> 10#include <linux/hugetlb.h> 11#include <linux/mman.h> 12#include <linux/slab.h> 13#include <linux/kernel_stat.h> 14#include <linux/swap.h> 15#include <linux/vmalloc.h> 16#include <linux/pagemap.h> 17#include <linux/namei.h> 18#include <linux/shm.h> 19#include <linux/blkdev.h> 20#include <linux/writeback.h> 21#include <linux/proc_fs.h> 22#include <linux/seq_file.h> 23#include <linux/init.h> 24#include <linux/module.h> 25#include <linux/rmap.h> 26#include <linux/security.h> 27#include <linux/backing-dev.h> 28#include <linux/mutex.h> 29#include <linux/capability.h> 30#include <linux/syscalls.h> 31 32#include <asm/pgtable.h> 33#include <asm/tlbflush.h> 34#include <linux/swapops.h> 35 36DEFINE_SPINLOCK(swap_lock); 37unsigned int nr_swapfiles; 38long total_swap_pages; 39static int swap_overflow; 40 41static const char Bad_file[] = "Bad swap file entry "; 42static const char Unused_file[] = "Unused swap file entry "; 43static const char Bad_offset[] = "Bad swap offset entry "; 44static const char Unused_offset[] = "Unused swap offset entry "; 45 46struct swap_list_t swap_list = {-1, -1}; 47 48struct swap_info_struct swap_info[MAX_SWAPFILES]; 49 50static 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 */ 57static DECLARE_RWSEM(swap_unplug_sem); 58 59void 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 88static 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--; 132cluster: 133 offset = si->cluster_next; 134 if (offset > si->highest_bit) 135lowest: offset = si->lowest_bit; 136checks: 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 170no_page: 171 si->flags -= SWP_SCANNING; 172 return 0; 173} 174 175swp_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++; 211noswap: 212 spin_unlock(&swap_lock); 213 return (swp_entry_t) {0}; 214} 215 216swp_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 236static 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 257bad_free: 258 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val); 259 goto out; 260bad_offset: 261 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val); 262 goto out; 263bad_device: 264 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val); 265 goto out; 266bad_nofile: 267 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val); 268out: 269 return NULL; 270} 271 272static 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 */ 297void 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 */ 311static 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 */ 331int 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 */ 346int 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 */ 393void free_swap_and_cache(swp_entry_t entry) 394{ 395 struct swap_info_struct * p; 396 struct page *page = NULL; 397 398 p = swap_info_get(entry); 399 if (p) { 400 if (swap_entry_free(p, swp_offset(entry)) == 1) 401 page = find_trylock_page(&swapper_space, entry.val); 402 spin_unlock(&swap_lock); 403 } 404 if (page) { 405 int one_user; 406 407 BUG_ON(PagePrivate(page)); 408 page_cache_get(page); 409 one_user = (page_count(page) == 2); 410 /* Only cache user (+us), or swap space full? Free it! */ 411 if (!PageWriteback(page) && (one_user || vm_swap_full())) { 412 delete_from_swap_cache(page); 413 SetPageDirty(page); 414 } 415 unlock_page(page); 416 page_cache_release(page); 417 } 418} 419 420/* 421 * No need to decide whether this PTE shares the swap entry with others, 422 * just let do_wp_page work it out if a write is requested later - to 423 * force COW, vm_page_prot omits write permission from any private vma. 424 */ 425static void unuse_pte(struct vm_area_struct *vma, pte_t *pte, 426 unsigned long addr, swp_entry_t entry, struct page *page) 427{ 428 inc_mm_counter(vma->vm_mm, anon_rss); 429 get_page(page); 430 set_pte_at(vma->vm_mm, addr, pte, 431 pte_mkold(mk_pte(page, vma->vm_page_prot))); 432 page_add_anon_rmap(page, vma, addr); 433 swap_free(entry); 434 /* 435 * Move the page to the active list so it is not 436 * immediately swapped out again after swapon. 437 */ 438 activate_page(page); 439} 440 441static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 442 unsigned long addr, unsigned long end, 443 swp_entry_t entry, struct page *page) 444{ 445 pte_t swp_pte = swp_entry_to_pte(entry); 446 pte_t *pte; 447 spinlock_t *ptl; 448 int found = 0; 449 450 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 451 do { 452 /* 453 * swapoff spends a _lot_ of time in this loop! 454 * Test inline before going to call unuse_pte. 455 */ 456 if (unlikely(pte_same(*pte, swp_pte))) { 457 unuse_pte(vma, pte++, addr, entry, page); 458 found = 1; 459 break; 460 } 461 } while (pte++, addr += PAGE_SIZE, addr != end); 462 pte_unmap_unlock(pte - 1, ptl); 463 return found; 464} 465 466static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, 467 unsigned long addr, unsigned long end, 468 swp_entry_t entry, struct page *page) 469{ 470 pmd_t *pmd; 471 unsigned long next; 472 473 pmd = pmd_offset(pud, addr); 474 do { 475 next = pmd_addr_end(addr, end); 476 if (pmd_none_or_clear_bad(pmd)) 477 continue; 478 if (unuse_pte_range(vma, pmd, addr, next, entry, page)) 479 return 1; 480 } while (pmd++, addr = next, addr != end); 481 return 0; 482} 483 484static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd, 485 unsigned long addr, unsigned long end, 486 swp_entry_t entry, struct page *page) 487{ 488 pud_t *pud; 489 unsigned long next; 490 491 pud = pud_offset(pgd, addr); 492 do { 493 next = pud_addr_end(addr, end); 494 if (pud_none_or_clear_bad(pud)) 495 continue; 496 if (unuse_pmd_range(vma, pud, addr, next, entry, page)) 497 return 1; 498 } while (pud++, addr = next, addr != end); 499 return 0; 500} 501 502static int unuse_vma(struct vm_area_struct *vma, 503 swp_entry_t entry, struct page *page) 504{ 505 pgd_t *pgd; 506 unsigned long addr, end, next; 507 508 if (page->mapping) { 509 addr = page_address_in_vma(page, vma); 510 if (addr == -EFAULT) 511 return 0; 512 else 513 end = addr + PAGE_SIZE; 514 } else { 515 addr = vma->vm_start; 516 end = vma->vm_end; 517 } 518 519 pgd = pgd_offset(vma->vm_mm, addr); 520 do { 521 next = pgd_addr_end(addr, end); 522 if (pgd_none_or_clear_bad(pgd)) 523 continue; 524 if (unuse_pud_range(vma, pgd, addr, next, entry, page)) 525 return 1; 526 } while (pgd++, addr = next, addr != end); 527 return 0; 528} 529 530static int unuse_mm(struct mm_struct *mm, 531 swp_entry_t entry, struct page *page) 532{ 533 struct vm_area_struct *vma; 534 535 if (!down_read_trylock(&mm->mmap_sem)) { 536 /* 537 * Activate page so shrink_cache is unlikely to unmap its 538 * ptes while lock is dropped, so swapoff can make progress. 539 */ 540 activate_page(page); 541 unlock_page(page); 542 down_read(&mm->mmap_sem); 543 lock_page(page); 544 } 545 for (vma = mm->mmap; vma; vma = vma->vm_next) { 546 if (vma->anon_vma && unuse_vma(vma, entry, page)) 547 break; 548 } 549 up_read(&mm->mmap_sem); 550 /* 551 * Currently unuse_mm cannot fail, but leave error handling 552 * at call sites for now, since we change it from time to time. 553 */ 554 return 0; 555} 556 557#ifdef CONFIG_MIGRATION 558int remove_vma_swap(struct vm_area_struct *vma, struct page *page) 559{ 560 swp_entry_t entry = { .val = page_private(page) }; 561 562 return unuse_vma(vma, entry, page); 563} 564#endif 565 566/* 567 * Scan swap_map from current position to next entry still in use. 568 * Recycle to start on reaching the end, returning 0 when empty. 569 */ 570static unsigned int find_next_to_unuse(struct swap_info_struct *si, 571 unsigned int prev) 572{ 573 unsigned int max = si->max; 574 unsigned int i = prev; 575 int count; 576 577 /* 578 * No need for swap_lock here: we're just looking 579 * for whether an entry is in use, not modifying it; false 580 * hits are okay, and sys_swapoff() has already prevented new 581 * allocations from this area (while holding swap_lock). 582 */ 583 for (;;) { 584 if (++i >= max) { 585 if (!prev) { 586 i = 0; 587 break; 588 } 589 /* 590 * No entries in use at top of swap_map, 591 * loop back to start and recheck there. 592 */ 593 max = prev + 1; 594 prev = 0; 595 i = 1; 596 } 597 count = si->swap_map[i]; 598 if (count && count != SWAP_MAP_BAD) 599 break; 600 } 601 return i; 602} 603 604/* 605 * We completely avoid races by reading each swap page in advance, 606 * and then search for the process using it. All the necessary 607 * page table adjustments can then be made atomically. 608 */ 609static int try_to_unuse(unsigned int type) 610{ 611 struct swap_info_struct * si = &swap_info[type]; 612 struct mm_struct *start_mm; 613 unsigned short *swap_map; 614 unsigned short swcount; 615 struct page *page; 616 swp_entry_t entry; 617 unsigned int i = 0; 618 int retval = 0; 619 int reset_overflow = 0; 620 int shmem; 621 622 /* 623 * When searching mms for an entry, a good strategy is to 624 * start at the first mm we freed the previous entry from 625 * (though actually we don't notice whether we or coincidence 626 * freed the entry). Initialize this start_mm with a hold. 627 * 628 * A simpler strategy would be to start at the last mm we 629 * freed the previous entry from; but that would take less 630 * advantage of mmlist ordering, which clusters forked mms 631 * together, child after parent. If we race with dup_mmap(), we 632 * prefer to resolve parent before child, lest we miss entries 633 * duplicated after we scanned child: using last mm would invert 634 * that. Though it's only a serious concern when an overflowed 635 * swap count is reset from SWAP_MAP_MAX, preventing a rescan. 636 */ 637 start_mm = &init_mm; 638 atomic_inc(&init_mm.mm_users); 639 640 /* 641 * Keep on scanning until all entries have gone. Usually, 642 * one pass through swap_map is enough, but not necessarily: 643 * there are races when an instance of an entry might be missed. 644 */ 645 while ((i = find_next_to_unuse(si, i)) != 0) { 646 if (signal_pending(current)) { 647 retval = -EINTR; 648 break; 649 } 650 651 /* 652 * Get a page for the entry, using the existing swap 653 * cache page if there is one. Otherwise, get a clean 654 * page and read the swap into it. 655 */ 656 swap_map = &si->swap_map[i]; 657 entry = swp_entry(type, i); 658again: 659 page = read_swap_cache_async(entry, NULL, 0); 660 if (!page) { 661 /* 662 * Either swap_duplicate() failed because entry 663 * has been freed independently, and will not be 664 * reused since sys_swapoff() already disabled 665 * allocation from here, or alloc_page() failed. 666 */ 667 if (!*swap_map) 668 continue; 669 retval = -ENOMEM; 670 break; 671 } 672 673 /* 674 * Don't hold on to start_mm if it looks like exiting. 675 */ 676 if (atomic_read(&start_mm->mm_users) == 1) { 677 mmput(start_mm); 678 start_mm = &init_mm; 679 atomic_inc(&init_mm.mm_users); 680 } 681 682 /* 683 * Wait for and lock page. When do_swap_page races with 684 * try_to_unuse, do_swap_page can handle the fault much 685 * faster than try_to_unuse can locate the entry. This 686 * apparently redundant "wait_on_page_locked" lets try_to_unuse 687 * defer to do_swap_page in such a case - in some tests, 688 * do_swap_page and try_to_unuse repeatedly compete. 689 */ 690 wait_on_page_locked(page); 691 wait_on_page_writeback(page); 692 lock_page(page); 693 if (!PageSwapCache(page)) { 694 /* Page migration has occured */ 695 unlock_page(page); 696 page_cache_release(page); 697 goto again; 698 } 699 wait_on_page_writeback(page); 700 701 /* 702 * Remove all references to entry. 703 * Whenever we reach init_mm, there's no address space 704 * to search, but use it as a reminder to search shmem. 705 */ 706 shmem = 0; 707 swcount = *swap_map; 708 if (swcount > 1) { 709 if (start_mm == &init_mm) 710 shmem = shmem_unuse(entry, page); 711 else 712 retval = unuse_mm(start_mm, entry, page); 713 } 714 if (*swap_map > 1) { 715 int set_start_mm = (*swap_map >= swcount); 716 struct list_head *p = &start_mm->mmlist; 717 struct mm_struct *new_start_mm = start_mm; 718 struct mm_struct *prev_mm = start_mm; 719 struct mm_struct *mm; 720 721 atomic_inc(&new_start_mm->mm_users); 722 atomic_inc(&prev_mm->mm_users); 723 spin_lock(&mmlist_lock); 724 while (*swap_map > 1 && !retval && 725 (p = p->next) != &start_mm->mmlist) { 726 mm = list_entry(p, struct mm_struct, mmlist); 727 if (atomic_inc_return(&mm->mm_users) == 1) { 728 atomic_dec(&mm->mm_users); 729 continue; 730 } 731 spin_unlock(&mmlist_lock); 732 mmput(prev_mm); 733 prev_mm = mm; 734 735 cond_resched(); 736 737 swcount = *swap_map; 738 if (swcount <= 1) 739 ; 740 else if (mm == &init_mm) { 741 set_start_mm = 1; 742 shmem = shmem_unuse(entry, page); 743 } else 744 retval = unuse_mm(mm, entry, page); 745 if (set_start_mm && *swap_map < swcount) { 746 mmput(new_start_mm); 747 atomic_inc(&mm->mm_users); 748 new_start_mm = mm; 749 set_start_mm = 0; 750 } 751 spin_lock(&mmlist_lock); 752 } 753 spin_unlock(&mmlist_lock); 754 mmput(prev_mm); 755 mmput(start_mm); 756 start_mm = new_start_mm; 757 } 758 if (retval) { 759 unlock_page(page); 760 page_cache_release(page); 761 break; 762 } 763 764 /* 765 * How could swap count reach 0x7fff when the maximum 766 * pid is 0x7fff, and there's no way to repeat a swap 767 * page within an mm (except in shmem, where it's the 768 * shared object which takes the reference count)? 769 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4. 770 * 771 * If that's wrong, then we should worry more about 772 * exit_mmap() and do_munmap() cases described above: 773 * we might be resetting SWAP_MAP_MAX too early here. 774 * We know "Undead"s can happen, they're okay, so don't 775 * report them; but do report if we reset SWAP_MAP_MAX. 776 */ 777 if (*swap_map == SWAP_MAP_MAX) { 778 spin_lock(&swap_lock); 779 *swap_map = 1; 780 spin_unlock(&swap_lock); 781 reset_overflow = 1; 782 } 783 784 /* 785 * If a reference remains (rare), we would like to leave 786 * the page in the swap cache; but try_to_unmap could 787 * then re-duplicate the entry once we drop page lock, 788 * so we might loop indefinitely; also, that page could 789 * not be swapped out to other storage meanwhile. So: 790 * delete from cache even if there's another reference, 791 * after ensuring that the data has been saved to disk - 792 * since if the reference remains (rarer), it will be 793 * read from disk into another page. Splitting into two 794 * pages would be incorrect if swap supported "shared 795 * private" pages, but they are handled by tmpfs files. 796 * 797 * Note shmem_unuse already deleted a swappage from 798 * the swap cache, unless the move to filepage failed: 799 * in which case it left swappage in cache, lowered its 800 * swap count to pass quickly through the loops above, 801 * and now we must reincrement count to try again later. 802 */ 803 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) { 804 struct writeback_control wbc = { 805 .sync_mode = WB_SYNC_NONE, 806 }; 807 808 swap_writepage(page, &wbc); 809 lock_page(page); 810 wait_on_page_writeback(page); 811 } 812 if (PageSwapCache(page)) { 813 if (shmem) 814 swap_duplicate(entry); 815 else 816 delete_from_swap_cache(page); 817 } 818 819 /* 820 * So we could skip searching mms once swap count went 821 * to 1, we did not mark any present ptes as dirty: must 822 * mark page dirty so shrink_list will preserve it. 823 */ 824 SetPageDirty(page); 825 unlock_page(page); 826 page_cache_release(page); 827 828 /* 829 * Make sure that we aren't completely killing 830 * interactive performance. 831 */ 832 cond_resched(); 833 } 834 835 mmput(start_mm); 836 if (reset_overflow) { 837 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n"); 838 swap_overflow = 0; 839 } 840 return retval; 841} 842 843/* 844 * After a successful try_to_unuse, if no swap is now in use, we know 845 * we can empty the mmlist. swap_lock must be held on entry and exit. 846 * Note that mmlist_lock nests inside swap_lock, and an mm must be 847 * added to the mmlist just after page_duplicate - before would be racy. 848 */ 849static void drain_mmlist(void) 850{ 851 struct list_head *p, *next; 852 unsigned int i; 853 854 for (i = 0; i < nr_swapfiles; i++) 855 if (swap_info[i].inuse_pages) 856 return; 857 spin_lock(&mmlist_lock); 858 list_for_each_safe(p, next, &init_mm.mmlist) 859 list_del_init(p); 860 spin_unlock(&mmlist_lock); 861} 862 863/* 864 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which 865 * corresponds to page offset `offset'. 866 */ 867sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset) 868{ 869 struct swap_extent *se = sis->curr_swap_extent; 870 struct swap_extent *start_se = se; 871 872 for ( ; ; ) { 873 struct list_head *lh; 874 875 if (se->start_page <= offset && 876 offset < (se->start_page + se->nr_pages)) { 877 return se->start_block + (offset - se->start_page); 878 } 879 lh = se->list.next; 880 if (lh == &sis->extent_list) 881 lh = lh->next; 882 se = list_entry(lh, struct swap_extent, list); 883 sis->curr_swap_extent = se; 884 BUG_ON(se == start_se); /* It *must* be present */ 885 } 886} 887 888/* 889 * Free all of a swapdev's extent information 890 */ 891static void destroy_swap_extents(struct swap_info_struct *sis) 892{ 893 while (!list_empty(&sis->extent_list)) { 894 struct swap_extent *se; 895 896 se = list_entry(sis->extent_list.next, 897 struct swap_extent, list); 898 list_del(&se->list); 899 kfree(se); 900 } 901} 902 903/* 904 * Add a block range (and the corresponding page range) into this swapdev's 905 * extent list. The extent list is kept sorted in page order. 906 * 907 * This function rather assumes that it is called in ascending page order. 908 */ 909static int 910add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, 911 unsigned long nr_pages, sector_t start_block) 912{ 913 struct swap_extent *se; 914 struct swap_extent *new_se; 915 struct list_head *lh; 916 917 lh = sis->extent_list.prev; /* The highest page extent */ 918 if (lh != &sis->extent_list) { 919 se = list_entry(lh, struct swap_extent, list); 920 BUG_ON(se->start_page + se->nr_pages != start_page); 921 if (se->start_block + se->nr_pages == start_block) { 922 /* Merge it */ 923 se->nr_pages += nr_pages; 924 return 0; 925 } 926 } 927 928 /* 929 * No merge. Insert a new extent, preserving ordering. 930 */ 931 new_se = kmalloc(sizeof(*se), GFP_KERNEL); 932 if (new_se == NULL) 933 return -ENOMEM; 934 new_se->start_page = start_page; 935 new_se->nr_pages = nr_pages; 936 new_se->start_block = start_block; 937 938 list_add_tail(&new_se->list, &sis->extent_list); 939 return 1; 940} 941 942/* 943 * A `swap extent' is a simple thing which maps a contiguous range of pages 944 * onto a contiguous range of disk blocks. An ordered list of swap extents 945 * is built at swapon time and is then used at swap_writepage/swap_readpage 946 * time for locating where on disk a page belongs. 947 * 948 * If the swapfile is an S_ISBLK block device, a single extent is installed. 949 * This is done so that the main operating code can treat S_ISBLK and S_ISREG 950 * swap files identically. 951 * 952 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap 953 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK 954 * swapfiles are handled *identically* after swapon time. 955 * 956 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks 957 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If 958 * some stray blocks are found which do not fall within the PAGE_SIZE alignment 959 * requirements, they are simply tossed out - we will never use those blocks 960 * for swapping. 961 * 962 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This 963 * prevents root from shooting her foot off by ftruncating an in-use swapfile, 964 * which will scribble on the fs. 965 * 966 * The amount of disk space which a single swap extent represents varies. 967 * Typically it is in the 1-4 megabyte range. So we can have hundreds of 968 * extents in the list. To avoid much list walking, we cache the previous 969 * search location in `curr_swap_extent', and start new searches from there. 970 * This is extremely effective. The average number of iterations in 971 * map_swap_page() has been measured at about 0.3 per page. - akpm. 972 */ 973static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) 974{ 975 struct inode *inode; 976 unsigned blocks_per_page; 977 unsigned long page_no; 978 unsigned blkbits; 979 sector_t probe_block; 980 sector_t last_block; 981 sector_t lowest_block = -1; 982 sector_t highest_block = 0; 983 int nr_extents = 0; 984 int ret; 985 986 inode = sis->swap_file->f_mapping->host; 987 if (S_ISBLK(inode->i_mode)) { 988 ret = add_swap_extent(sis, 0, sis->max, 0); 989 *span = sis->pages; 990 goto done; 991 } 992 993 blkbits = inode->i_blkbits; 994 blocks_per_page = PAGE_SIZE >> blkbits; 995 996 /* 997 * Map all the blocks into the extent list. This code doesn't try 998 * to be very smart. 999 */ 1000 probe_block = 0; 1001 page_no = 0; 1002 last_block = i_size_read(inode) >> blkbits; 1003 while ((probe_block + blocks_per_page) <= last_block && 1004 page_no < sis->max) { 1005 unsigned block_in_page; 1006 sector_t first_block; 1007 1008 first_block = bmap(inode, probe_block); 1009 if (first_block == 0) 1010 goto bad_bmap; 1011 1012 /* 1013 * It must be PAGE_SIZE aligned on-disk 1014 */ 1015 if (first_block & (blocks_per_page - 1)) { 1016 probe_block++; 1017 goto reprobe; 1018 } 1019 1020 for (block_in_page = 1; block_in_page < blocks_per_page; 1021 block_in_page++) { 1022 sector_t block; 1023 1024 block = bmap(inode, probe_block + block_in_page); 1025 if (block == 0) 1026 goto bad_bmap; 1027 if (block != first_block + block_in_page) { 1028 /* Discontiguity */ 1029 probe_block++; 1030 goto reprobe; 1031 } 1032 } 1033 1034 first_block >>= (PAGE_SHIFT - blkbits); 1035 if (page_no) { /* exclude the header page */ 1036 if (first_block < lowest_block) 1037 lowest_block = first_block; 1038 if (first_block > highest_block) 1039 highest_block = first_block; 1040 } 1041 1042 /* 1043 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 1044 */ 1045 ret = add_swap_extent(sis, page_no, 1, first_block); 1046 if (ret < 0) 1047 goto out; 1048 nr_extents += ret; 1049 page_no++; 1050 probe_block += blocks_per_page; 1051reprobe: 1052 continue; 1053 } 1054 ret = nr_extents; 1055 *span = 1 + highest_block - lowest_block; 1056 if (page_no == 0) 1057 page_no = 1; /* force Empty message */ 1058 sis->max = page_no; 1059 sis->pages = page_no - 1; 1060 sis->highest_bit = page_no - 1; 1061done: 1062 sis->curr_swap_extent = list_entry(sis->extent_list.prev, 1063 struct swap_extent, list); 1064 goto out; 1065bad_bmap: 1066 printk(KERN_ERR "swapon: swapfile has holes\n"); 1067 ret = -EINVAL; 1068out: 1069 return ret; 1070} 1071 1072#if 0 /* We don't need this yet */ 1073#include <linux/backing-dev.h> 1074int page_queue_congested(struct page *page) 1075{ 1076 struct backing_dev_info *bdi; 1077 1078 BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */ 1079 1080 if (PageSwapCache(page)) { 1081 swp_entry_t entry = { .val = page_private(page) }; 1082 struct swap_info_struct *sis; 1083 1084 sis = get_swap_info_struct(swp_type(entry)); 1085 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info; 1086 } else 1087 bdi = page->mapping->backing_dev_info; 1088 return bdi_write_congested(bdi); 1089} 1090#endif 1091 1092asmlinkage long sys_swapoff(const char __user * specialfile) 1093{ 1094 struct swap_info_struct * p = NULL; 1095 unsigned short *swap_map; 1096 struct file *swap_file, *victim; 1097 struct address_space *mapping; 1098 struct inode *inode; 1099 char * pathname; 1100 int i, type, prev; 1101 int err; 1102 1103 if (!capable(CAP_SYS_ADMIN)) 1104 return -EPERM; 1105 1106 pathname = getname(specialfile); 1107 err = PTR_ERR(pathname); 1108 if (IS_ERR(pathname)) 1109 goto out; 1110 1111 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0); 1112 putname(pathname); 1113 err = PTR_ERR(victim); 1114 if (IS_ERR(victim)) 1115 goto out; 1116 1117 mapping = victim->f_mapping; 1118 prev = -1; 1119 spin_lock(&swap_lock); 1120 for (type = swap_list.head; type >= 0; type = swap_info[type].next) { 1121 p = swap_info + type; 1122 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) { 1123 if (p->swap_file->f_mapping == mapping) 1124 break; 1125 } 1126 prev = type; 1127 } 1128 if (type < 0) { 1129 err = -EINVAL; 1130 spin_unlock(&swap_lock); 1131 goto out_dput; 1132 } 1133 if (!security_vm_enough_memory(p->pages)) 1134 vm_unacct_memory(p->pages); 1135 else { 1136 err = -ENOMEM; 1137 spin_unlock(&swap_lock); 1138 goto out_dput; 1139 } 1140 if (prev < 0) { 1141 swap_list.head = p->next; 1142 } else { 1143 swap_info[prev].next = p->next; 1144 } 1145 if (type == swap_list.next) { 1146 /* just pick something that's safe... */ 1147 swap_list.next = swap_list.head; 1148 } 1149 nr_swap_pages -= p->pages; 1150 total_swap_pages -= p->pages; 1151 p->flags &= ~SWP_WRITEOK; 1152 spin_unlock(&swap_lock); 1153 1154 current->flags |= PF_SWAPOFF; 1155 err = try_to_unuse(type); 1156 current->flags &= ~PF_SWAPOFF; 1157 1158 if (err) { 1159 /* re-insert swap space back into swap_list */ 1160 spin_lock(&swap_lock); 1161 for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next) 1162 if (p->prio >= swap_info[i].prio) 1163 break; 1164 p->next = i; 1165 if (prev < 0) 1166 swap_list.head = swap_list.next = p - swap_info; 1167 else 1168 swap_info[prev].next = p - swap_info; 1169 nr_swap_pages += p->pages; 1170 total_swap_pages += p->pages; 1171 p->flags |= SWP_WRITEOK; 1172 spin_unlock(&swap_lock); 1173 goto out_dput; 1174 } 1175 1176 /* wait for any unplug function to finish */ 1177 down_write(&swap_unplug_sem); 1178 up_write(&swap_unplug_sem); 1179 1180 destroy_swap_extents(p); 1181 mutex_lock(&swapon_mutex); 1182 spin_lock(&swap_lock); 1183 drain_mmlist(); 1184 1185 /* wait for anyone still in scan_swap_map */ 1186 p->highest_bit = 0; /* cuts scans short */ 1187 while (p->flags >= SWP_SCANNING) { 1188 spin_unlock(&swap_lock); 1189 schedule_timeout_uninterruptible(1); 1190 spin_lock(&swap_lock); 1191 } 1192 1193 swap_file = p->swap_file; 1194 p->swap_file = NULL; 1195 p->max = 0; 1196 swap_map = p->swap_map; 1197 p->swap_map = NULL; 1198 p->flags = 0; 1199 spin_unlock(&swap_lock); 1200 mutex_unlock(&swapon_mutex); 1201 vfree(swap_map); 1202 inode = mapping->host; 1203 if (S_ISBLK(inode->i_mode)) { 1204 struct block_device *bdev = I_BDEV(inode); 1205 set_blocksize(bdev, p->old_block_size); 1206 bd_release(bdev); 1207 } else { 1208 mutex_lock(&inode->i_mutex); 1209 inode->i_flags &= ~S_SWAPFILE; 1210 mutex_unlock(&inode->i_mutex); 1211 } 1212 filp_close(swap_file, NULL); 1213 err = 0; 1214 1215out_dput: 1216 filp_close(victim, NULL); 1217out: 1218 return err; 1219} 1220 1221#ifdef CONFIG_PROC_FS 1222/* iterator */ 1223static void *swap_start(struct seq_file *swap, loff_t *pos) 1224{ 1225 struct swap_info_struct *ptr = swap_info; 1226 int i; 1227 loff_t l = *pos; 1228 1229 mutex_lock(&swapon_mutex); 1230 1231 for (i = 0; i < nr_swapfiles; i++, ptr++) { 1232 if (!(ptr->flags & SWP_USED) || !ptr->swap_map) 1233 continue; 1234 if (!l--) 1235 return ptr; 1236 } 1237 1238 return NULL; 1239} 1240 1241static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) 1242{ 1243 struct swap_info_struct *ptr = v; 1244 struct swap_info_struct *endptr = swap_info + nr_swapfiles; 1245 1246 for (++ptr; ptr < endptr; ptr++) { 1247 if (!(ptr->flags & SWP_USED) || !ptr->swap_map) 1248 continue; 1249 ++*pos; 1250 return ptr; 1251 } 1252 1253 return NULL; 1254} 1255 1256static void swap_stop(struct seq_file *swap, void *v) 1257{ 1258 mutex_unlock(&swapon_mutex); 1259} 1260 1261static int swap_show(struct seq_file *swap, void *v) 1262{ 1263 struct swap_info_struct *ptr = v; 1264 struct file *file; 1265 int len; 1266 1267 if (v == swap_info) 1268 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); 1269 1270 file = ptr->swap_file; 1271 len = seq_path(swap, file->f_vfsmnt, file->f_dentry, " \t\n\\"); 1272 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n", 1273 len < 40 ? 40 - len : 1, " ", 1274 S_ISBLK(file->f_dentry->d_inode->i_mode) ? 1275 "partition" : "file\t", 1276 ptr->pages << (PAGE_SHIFT - 10), 1277 ptr->inuse_pages << (PAGE_SHIFT - 10), 1278 ptr->prio); 1279 return 0; 1280} 1281 1282static struct seq_operations swaps_op = { 1283 .start = swap_start, 1284 .next = swap_next, 1285 .stop = swap_stop, 1286 .show = swap_show 1287}; 1288 1289static int swaps_open(struct inode *inode, struct file *file) 1290{ 1291 return seq_open(file, &swaps_op); 1292} 1293 1294static struct file_operations proc_swaps_operations = { 1295 .open = swaps_open, 1296 .read = seq_read, 1297 .llseek = seq_lseek, 1298 .release = seq_release, 1299}; 1300 1301static int __init procswaps_init(void) 1302{ 1303 struct proc_dir_entry *entry; 1304 1305 entry = create_proc_entry("swaps", 0, NULL); 1306 if (entry) 1307 entry->proc_fops = &proc_swaps_operations; 1308 return 0; 1309} 1310__initcall(procswaps_init); 1311#endif /* CONFIG_PROC_FS */ 1312 1313/* 1314 * Written 01/25/92 by Simmule Turner, heavily changed by Linus. 1315 * 1316 * The swapon system call 1317 */ 1318asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags) 1319{ 1320 struct swap_info_struct * p; 1321 char *name = NULL; 1322 struct block_device *bdev = NULL; 1323 struct file *swap_file = NULL; 1324 struct address_space *mapping; 1325 unsigned int type; 1326 int i, prev; 1327 int error; 1328 static int least_priority; 1329 union swap_header *swap_header = NULL; 1330 int swap_header_version; 1331 unsigned int nr_good_pages = 0; 1332 int nr_extents = 0; 1333 sector_t span; 1334 unsigned long maxpages = 1; 1335 int swapfilesize; 1336 unsigned short *swap_map; 1337 struct page *page = NULL; 1338 struct inode *inode = NULL; 1339 int did_down = 0; 1340 1341 if (!capable(CAP_SYS_ADMIN)) 1342 return -EPERM; 1343 spin_lock(&swap_lock); 1344 p = swap_info; 1345 for (type = 0 ; type < nr_swapfiles ; type++,p++) 1346 if (!(p->flags & SWP_USED)) 1347 break; 1348 error = -EPERM; 1349 /* 1350 * Test if adding another swap device is possible. There are 1351 * two limiting factors: 1) the number of bits for the swap 1352 * type swp_entry_t definition and 2) the number of bits for 1353 * the swap type in the swap ptes as defined by the different 1354 * architectures. To honor both limitations a swap entry 1355 * with swap offset 0 and swap type ~0UL is created, encoded 1356 * to a swap pte, decoded to a swp_entry_t again and finally 1357 * the swap type part is extracted. This will mask all bits 1358 * from the initial ~0UL that can't be encoded in either the 1359 * swp_entry_t or the architecture definition of a swap pte. 1360 */ 1361 if (type > swp_type(pte_to_swp_entry(swp_entry_to_pte(swp_entry(~0UL,0))))) { 1362 spin_unlock(&swap_lock); 1363 goto out; 1364 } 1365 if (type >= nr_swapfiles) 1366 nr_swapfiles = type+1; 1367 INIT_LIST_HEAD(&p->extent_list); 1368 p->flags = SWP_USED; 1369 p->swap_file = NULL; 1370 p->old_block_size = 0; 1371 p->swap_map = NULL; 1372 p->lowest_bit = 0; 1373 p->highest_bit = 0; 1374 p->cluster_nr = 0; 1375 p->inuse_pages = 0; 1376 p->next = -1; 1377 if (swap_flags & SWAP_FLAG_PREFER) { 1378 p->prio = 1379 (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT; 1380 } else { 1381 p->prio = --least_priority; 1382 } 1383 spin_unlock(&swap_lock); 1384 name = getname(specialfile); 1385 error = PTR_ERR(name); 1386 if (IS_ERR(name)) { 1387 name = NULL; 1388 goto bad_swap_2; 1389 } 1390 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0); 1391 error = PTR_ERR(swap_file); 1392 if (IS_ERR(swap_file)) { 1393 swap_file = NULL; 1394 goto bad_swap_2; 1395 } 1396 1397 p->swap_file = swap_file; 1398 mapping = swap_file->f_mapping; 1399 inode = mapping->host; 1400 1401 error = -EBUSY; 1402 for (i = 0; i < nr_swapfiles; i++) { 1403 struct swap_info_struct *q = &swap_info[i]; 1404 1405 if (i == type || !q->swap_file) 1406 continue; 1407 if (mapping == q->swap_file->f_mapping) 1408 goto bad_swap; 1409 } 1410 1411 error = -EINVAL; 1412 if (S_ISBLK(inode->i_mode)) { 1413 bdev = I_BDEV(inode); 1414 error = bd_claim(bdev, sys_swapon); 1415 if (error < 0) { 1416 bdev = NULL; 1417 error = -EINVAL; 1418 goto bad_swap; 1419 } 1420 p->old_block_size = block_size(bdev); 1421 error = set_blocksize(bdev, PAGE_SIZE); 1422 if (error < 0) 1423 goto bad_swap; 1424 p->bdev = bdev; 1425 } else if (S_ISREG(inode->i_mode)) { 1426 p->bdev = inode->i_sb->s_bdev; 1427 mutex_lock(&inode->i_mutex); 1428 did_down = 1; 1429 if (IS_SWAPFILE(inode)) { 1430 error = -EBUSY; 1431 goto bad_swap; 1432 } 1433 } else { 1434 goto bad_swap; 1435 } 1436 1437 swapfilesize = i_size_read(inode) >> PAGE_SHIFT; 1438 1439 /* 1440 * Read the swap header. 1441 */ 1442 if (!mapping->a_ops->readpage) { 1443 error = -EINVAL; 1444 goto bad_swap; 1445 } 1446 page = read_cache_page(mapping, 0, 1447 (filler_t *)mapping->a_ops->readpage, swap_file); 1448 if (IS_ERR(page)) { 1449 error = PTR_ERR(page); 1450 goto bad_swap; 1451 } 1452 wait_on_page_locked(page); 1453 if (!PageUptodate(page)) 1454 goto bad_swap; 1455 kmap(page); 1456 swap_header = page_address(page); 1457 1458 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10)) 1459 swap_header_version = 1; 1460 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10)) 1461 swap_header_version = 2; 1462 else { 1463 printk(KERN_ERR "Unable to find swap-space signature\n"); 1464 error = -EINVAL; 1465 goto bad_swap; 1466 } 1467 1468 switch (swap_header_version) { 1469 case 1: 1470 printk(KERN_ERR "version 0 swap is no longer supported. " 1471 "Use mkswap -v1 %s\n", name); 1472 error = -EINVAL; 1473 goto bad_swap; 1474 case 2: 1475 /* Check the swap header's sub-version and the size of 1476 the swap file and bad block lists */ 1477 if (swap_header->info.version != 1) { 1478 printk(KERN_WARNING 1479 "Unable to handle swap header version %d\n", 1480 swap_header->info.version); 1481 error = -EINVAL; 1482 goto bad_swap; 1483 } 1484 1485 p->lowest_bit = 1; 1486 p->cluster_next = 1; 1487 1488 /* 1489 * Find out how many pages are allowed for a single swap 1490 * device. There are two limiting factors: 1) the number of 1491 * bits for the swap offset in the swp_entry_t type and 1492 * 2) the number of bits in the a swap pte as defined by 1493 * the different architectures. In order to find the 1494 * largest possible bit mask a swap entry with swap type 0 1495 * and swap offset ~0UL is created, encoded to a swap pte, 1496 * decoded to a swp_entry_t again and finally the swap 1497 * offset is extracted. This will mask all the bits from 1498 * the initial ~0UL mask that can't be encoded in either 1499 * the swp_entry_t or the architecture definition of a 1500 * swap pte. 1501 */ 1502 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1; 1503 if (maxpages > swap_header->info.last_page) 1504 maxpages = swap_header->info.last_page; 1505 p->highest_bit = maxpages - 1; 1506 1507 error = -EINVAL; 1508 if (!maxpages) 1509 goto bad_swap; 1510 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) 1511 goto bad_swap; 1512 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) 1513 goto bad_swap; 1514 1515 /* OK, set up the swap map and apply the bad block list */ 1516 if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) { 1517 error = -ENOMEM; 1518 goto bad_swap; 1519 } 1520 1521 error = 0; 1522 memset(p->swap_map, 0, maxpages * sizeof(short)); 1523 for (i = 0; i < swap_header->info.nr_badpages; i++) { 1524 int page_nr = swap_header->info.badpages[i]; 1525 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) 1526 error = -EINVAL; 1527 else 1528 p->swap_map[page_nr] = SWAP_MAP_BAD; 1529 } 1530 nr_good_pages = swap_header->info.last_page - 1531 swap_header->info.nr_badpages - 1532 1 /* header page */; 1533 if (error) 1534 goto bad_swap; 1535 } 1536 1537 if (swapfilesize && maxpages > swapfilesize) { 1538 printk(KERN_WARNING 1539 "Swap area shorter than signature indicates\n"); 1540 error = -EINVAL; 1541 goto bad_swap; 1542 } 1543 if (nr_good_pages) { 1544 p->swap_map[0] = SWAP_MAP_BAD; 1545 p->max = maxpages; 1546 p->pages = nr_good_pages; 1547 nr_extents = setup_swap_extents(p, &span); 1548 if (nr_extents < 0) { 1549 error = nr_extents; 1550 goto bad_swap; 1551 } 1552 nr_good_pages = p->pages; 1553 } 1554 if (!nr_good_pages) { 1555 printk(KERN_WARNING "Empty swap-file\n"); 1556 error = -EINVAL; 1557 goto bad_swap; 1558 } 1559 1560 mutex_lock(&swapon_mutex); 1561 spin_lock(&swap_lock); 1562 p->flags = SWP_ACTIVE; 1563 nr_swap_pages += nr_good_pages; 1564 total_swap_pages += nr_good_pages; 1565 1566 printk(KERN_INFO "Adding %uk swap on %s. " 1567 "Priority:%d extents:%d across:%lluk\n", 1568 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio, 1569 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10)); 1570 1571 /* insert swap space into swap_list: */ 1572 prev = -1; 1573 for (i = swap_list.head; i >= 0; i = swap_info[i].next) { 1574 if (p->prio >= swap_info[i].prio) { 1575 break; 1576 } 1577 prev = i; 1578 } 1579 p->next = i; 1580 if (prev < 0) { 1581 swap_list.head = swap_list.next = p - swap_info; 1582 } else { 1583 swap_info[prev].next = p - swap_info; 1584 } 1585 spin_unlock(&swap_lock); 1586 mutex_unlock(&swapon_mutex); 1587 error = 0; 1588 goto out; 1589bad_swap: 1590 if (bdev) { 1591 set_blocksize(bdev, p->old_block_size); 1592 bd_release(bdev); 1593 } 1594 destroy_swap_extents(p); 1595bad_swap_2: 1596 spin_lock(&swap_lock); 1597 swap_map = p->swap_map; 1598 p->swap_file = NULL; 1599 p->swap_map = NULL; 1600 p->flags = 0; 1601 if (!(swap_flags & SWAP_FLAG_PREFER)) 1602 ++least_priority; 1603 spin_unlock(&swap_lock); 1604 vfree(swap_map); 1605 if (swap_file) 1606 filp_close(swap_file, NULL); 1607out: 1608 if (page && !IS_ERR(page)) { 1609 kunmap(page); 1610 page_cache_release(page); 1611 } 1612 if (name) 1613 putname(name); 1614 if (did_down) { 1615 if (!error) 1616 inode->i_flags |= S_SWAPFILE; 1617 mutex_unlock(&inode->i_mutex); 1618 } 1619 return error; 1620} 1621 1622void si_swapinfo(struct sysinfo *val) 1623{ 1624 unsigned int i; 1625 unsigned long nr_to_be_unused = 0; 1626 1627 spin_lock(&swap_lock); 1628 for (i = 0; i < nr_swapfiles; i++) { 1629 if (!(swap_info[i].flags & SWP_USED) || 1630 (swap_info[i].flags & SWP_WRITEOK)) 1631 continue; 1632 nr_to_be_unused += swap_info[i].inuse_pages; 1633 } 1634 val->freeswap = nr_swap_pages + nr_to_be_unused; 1635 val->totalswap = total_swap_pages + nr_to_be_unused; 1636 spin_unlock(&swap_lock); 1637} 1638 1639/* 1640 * Verify that a swap entry is valid and increment its swap map count. 1641 * 1642 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as 1643 * "permanent", but will be reclaimed by the next swapoff. 1644 */ 1645int swap_duplicate(swp_entry_t entry) 1646{ 1647 struct swap_info_struct * p; 1648 unsigned long offset, type; 1649 int result = 0; 1650 1651 type = swp_type(entry); 1652 if (type >= nr_swapfiles) 1653 goto bad_file; 1654 p = type + swap_info; 1655 offset = swp_offset(entry); 1656 1657 spin_lock(&swap_lock); 1658 if (offset < p->max && p->swap_map[offset]) { 1659 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) { 1660 p->swap_map[offset]++; 1661 result = 1; 1662 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) { 1663 if (swap_overflow++ < 5) 1664 printk(KERN_WARNING "swap_dup: swap entry overflow\n"); 1665 p->swap_map[offset] = SWAP_MAP_MAX; 1666 result = 1; 1667 } 1668 } 1669 spin_unlock(&swap_lock); 1670out: 1671 return result; 1672 1673bad_file: 1674 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); 1675 goto out; 1676} 1677 1678struct swap_info_struct * 1679get_swap_info_struct(unsigned type) 1680{ 1681 return &swap_info[type]; 1682} 1683 1684/* 1685 * swap_lock prevents swap_map being freed. Don't grab an extra 1686 * reference on the swaphandle, it doesn't matter if it becomes unused. 1687 */ 1688int valid_swaphandles(swp_entry_t entry, unsigned long *offset) 1689{ 1690 int ret = 0, i = 1 << page_cluster; 1691 unsigned long toff; 1692 struct swap_info_struct *swapdev = swp_type(entry) + swap_info; 1693 1694 if (!page_cluster) /* no readahead */ 1695 return 0; 1696 toff = (swp_offset(entry) >> page_cluster) << page_cluster; 1697 if (!toff) /* first page is swap header */ 1698 toff++, i--; 1699 *offset = toff; 1700 1701 spin_lock(&swap_lock); 1702 do { 1703 /* Don't read-ahead past the end of the swap area */ 1704 if (toff >= swapdev->max) 1705 break; 1706 /* Don't read in free or bad pages */ 1707 if (!swapdev->swap_map[toff]) 1708 break; 1709 if (swapdev->swap_map[toff] == SWAP_MAP_BAD) 1710 break; 1711 toff++; 1712 ret++; 1713 } while (--i); 1714 spin_unlock(&swap_lock); 1715 return ret; 1716} 1717