swapfile.c revision 68bdc8d64742ccc5e340c5d122ebbab3f0cf2a74
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#include <linux/memcontrol.h> 31 32#include <asm/pgtable.h> 33#include <asm/tlbflush.h> 34#include <linux/swapops.h> 35 36static DEFINE_SPINLOCK(swap_lock); 37static unsigned int nr_swapfiles; 38long total_swap_pages; 39static int swap_overflow; 40static int least_priority; 41 42static const char Bad_file[] = "Bad swap file entry "; 43static const char Unused_file[] = "Unused swap file entry "; 44static const char Bad_offset[] = "Bad swap offset entry "; 45static const char Unused_offset[] = "Unused swap offset entry "; 46 47static struct swap_list_t swap_list = {-1, -1}; 48 49static struct swap_info_struct swap_info[MAX_SWAPFILES]; 50 51static DEFINE_MUTEX(swapon_mutex); 52 53/* 54 * We need this because the bdev->unplug_fn can sleep and we cannot 55 * hold swap_lock while calling the unplug_fn. And swap_lock 56 * cannot be turned into a mutex. 57 */ 58static DECLARE_RWSEM(swap_unplug_sem); 59 60void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page) 61{ 62 swp_entry_t entry; 63 64 down_read(&swap_unplug_sem); 65 entry.val = page_private(page); 66 if (PageSwapCache(page)) { 67 struct block_device *bdev = swap_info[swp_type(entry)].bdev; 68 struct backing_dev_info *bdi; 69 70 /* 71 * If the page is removed from swapcache from under us (with a 72 * racy try_to_unuse/swapoff) we need an additional reference 73 * count to avoid reading garbage from page_private(page) above. 74 * If the WARN_ON triggers during a swapoff it maybe the race 75 * condition and it's harmless. However if it triggers without 76 * swapoff it signals a problem. 77 */ 78 WARN_ON(page_count(page) <= 1); 79 80 bdi = bdev->bd_inode->i_mapping->backing_dev_info; 81 blk_run_backing_dev(bdi, page); 82 } 83 up_read(&swap_unplug_sem); 84} 85 86#define SWAPFILE_CLUSTER 256 87#define LATENCY_LIMIT 256 88 89static inline unsigned long scan_swap_map(struct swap_info_struct *si) 90{ 91 unsigned long offset, last_in_cluster; 92 int latency_ration = LATENCY_LIMIT; 93 94 /* 95 * We try to cluster swap pages by allocating them sequentially 96 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this 97 * way, however, we resort to first-free allocation, starting 98 * a new cluster. This prevents us from scattering swap pages 99 * all over the entire swap partition, so that we reduce 100 * overall disk seek times between swap pages. -- sct 101 * But we do now try to find an empty cluster. -Andrea 102 */ 103 104 si->flags += SWP_SCANNING; 105 if (unlikely(!si->cluster_nr)) { 106 si->cluster_nr = SWAPFILE_CLUSTER - 1; 107 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) 108 goto lowest; 109 spin_unlock(&swap_lock); 110 111 offset = si->lowest_bit; 112 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 113 114 /* Locate the first empty (unaligned) cluster */ 115 for (; last_in_cluster <= si->highest_bit; offset++) { 116 if (si->swap_map[offset]) 117 last_in_cluster = offset + SWAPFILE_CLUSTER; 118 else if (offset == last_in_cluster) { 119 spin_lock(&swap_lock); 120 si->cluster_next = offset-SWAPFILE_CLUSTER+1; 121 goto cluster; 122 } 123 if (unlikely(--latency_ration < 0)) { 124 cond_resched(); 125 latency_ration = LATENCY_LIMIT; 126 } 127 } 128 spin_lock(&swap_lock); 129 goto lowest; 130 } 131 132 si->cluster_nr--; 133cluster: 134 offset = si->cluster_next; 135 if (offset > si->highest_bit) 136lowest: offset = si->lowest_bit; 137checks: if (!(si->flags & SWP_WRITEOK)) 138 goto no_page; 139 if (!si->highest_bit) 140 goto no_page; 141 if (!si->swap_map[offset]) { 142 if (offset == si->lowest_bit) 143 si->lowest_bit++; 144 if (offset == si->highest_bit) 145 si->highest_bit--; 146 si->inuse_pages++; 147 if (si->inuse_pages == si->pages) { 148 si->lowest_bit = si->max; 149 si->highest_bit = 0; 150 } 151 si->swap_map[offset] = 1; 152 si->cluster_next = offset + 1; 153 si->flags -= SWP_SCANNING; 154 return offset; 155 } 156 157 spin_unlock(&swap_lock); 158 while (++offset <= si->highest_bit) { 159 if (!si->swap_map[offset]) { 160 spin_lock(&swap_lock); 161 goto checks; 162 } 163 if (unlikely(--latency_ration < 0)) { 164 cond_resched(); 165 latency_ration = LATENCY_LIMIT; 166 } 167 } 168 spin_lock(&swap_lock); 169 goto lowest; 170 171no_page: 172 si->flags -= SWP_SCANNING; 173 return 0; 174} 175 176swp_entry_t get_swap_page(void) 177{ 178 struct swap_info_struct *si; 179 pgoff_t offset; 180 int type, next; 181 int wrapped = 0; 182 183 spin_lock(&swap_lock); 184 if (nr_swap_pages <= 0) 185 goto noswap; 186 nr_swap_pages--; 187 188 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { 189 si = swap_info + type; 190 next = si->next; 191 if (next < 0 || 192 (!wrapped && si->prio != swap_info[next].prio)) { 193 next = swap_list.head; 194 wrapped++; 195 } 196 197 if (!si->highest_bit) 198 continue; 199 if (!(si->flags & SWP_WRITEOK)) 200 continue; 201 202 swap_list.next = next; 203 offset = scan_swap_map(si); 204 if (offset) { 205 spin_unlock(&swap_lock); 206 return swp_entry(type, offset); 207 } 208 next = swap_list.next; 209 } 210 211 nr_swap_pages++; 212noswap: 213 spin_unlock(&swap_lock); 214 return (swp_entry_t) {0}; 215} 216 217swp_entry_t get_swap_page_of_type(int type) 218{ 219 struct swap_info_struct *si; 220 pgoff_t offset; 221 222 spin_lock(&swap_lock); 223 si = swap_info + type; 224 if (si->flags & SWP_WRITEOK) { 225 nr_swap_pages--; 226 offset = scan_swap_map(si); 227 if (offset) { 228 spin_unlock(&swap_lock); 229 return swp_entry(type, offset); 230 } 231 nr_swap_pages++; 232 } 233 spin_unlock(&swap_lock); 234 return (swp_entry_t) {0}; 235} 236 237static struct swap_info_struct * swap_info_get(swp_entry_t entry) 238{ 239 struct swap_info_struct * p; 240 unsigned long offset, type; 241 242 if (!entry.val) 243 goto out; 244 type = swp_type(entry); 245 if (type >= nr_swapfiles) 246 goto bad_nofile; 247 p = & swap_info[type]; 248 if (!(p->flags & SWP_USED)) 249 goto bad_device; 250 offset = swp_offset(entry); 251 if (offset >= p->max) 252 goto bad_offset; 253 if (!p->swap_map[offset]) 254 goto bad_free; 255 spin_lock(&swap_lock); 256 return p; 257 258bad_free: 259 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val); 260 goto out; 261bad_offset: 262 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val); 263 goto out; 264bad_device: 265 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val); 266 goto out; 267bad_nofile: 268 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val); 269out: 270 return NULL; 271} 272 273static int swap_entry_free(struct swap_info_struct *p, unsigned long offset) 274{ 275 int count = p->swap_map[offset]; 276 277 if (count < SWAP_MAP_MAX) { 278 count--; 279 p->swap_map[offset] = count; 280 if (!count) { 281 if (offset < p->lowest_bit) 282 p->lowest_bit = offset; 283 if (offset > p->highest_bit) 284 p->highest_bit = offset; 285 if (p->prio > swap_info[swap_list.next].prio) 286 swap_list.next = p - swap_info; 287 nr_swap_pages++; 288 p->inuse_pages--; 289 } 290 } 291 return count; 292} 293 294/* 295 * Caller has made sure that the swapdevice corresponding to entry 296 * is still around or has not been recycled. 297 */ 298void swap_free(swp_entry_t entry) 299{ 300 struct swap_info_struct * p; 301 302 p = swap_info_get(entry); 303 if (p) { 304 swap_entry_free(p, swp_offset(entry)); 305 spin_unlock(&swap_lock); 306 } 307} 308 309/* 310 * How many references to page are currently swapped out? 311 */ 312static inline int page_swapcount(struct page *page) 313{ 314 int count = 0; 315 struct swap_info_struct *p; 316 swp_entry_t entry; 317 318 entry.val = page_private(page); 319 p = swap_info_get(entry); 320 if (p) { 321 /* Subtract the 1 for the swap cache itself */ 322 count = p->swap_map[swp_offset(entry)] - 1; 323 spin_unlock(&swap_lock); 324 } 325 return count; 326} 327 328/* 329 * We can write to an anon page without COW if there are no other references 330 * to it. And as a side-effect, free up its swap: because the old content 331 * on disk will never be read, and seeking back there to write new content 332 * later would only waste time away from clustering. 333 */ 334int reuse_swap_page(struct page *page) 335{ 336 int count; 337 338 VM_BUG_ON(!PageLocked(page)); 339 count = page_mapcount(page); 340 if (count <= 1 && PageSwapCache(page)) { 341 count += page_swapcount(page); 342 if (count == 1 && !PageWriteback(page)) { 343 delete_from_swap_cache(page); 344 SetPageDirty(page); 345 } 346 } 347 return count == 1; 348} 349 350/* 351 * If swap is getting full, or if there are no more mappings of this page, 352 * then try_to_free_swap is called to free its swap space. 353 */ 354int try_to_free_swap(struct page *page) 355{ 356 VM_BUG_ON(!PageLocked(page)); 357 358 if (!PageSwapCache(page)) 359 return 0; 360 if (PageWriteback(page)) 361 return 0; 362 if (page_swapcount(page)) 363 return 0; 364 365 delete_from_swap_cache(page); 366 SetPageDirty(page); 367 return 1; 368} 369 370/* 371 * Free the swap entry like above, but also try to 372 * free the page cache entry if it is the last user. 373 */ 374void free_swap_and_cache(swp_entry_t entry) 375{ 376 struct swap_info_struct * p; 377 struct page *page = NULL; 378 379 if (is_migration_entry(entry)) 380 return; 381 382 p = swap_info_get(entry); 383 if (p) { 384 if (swap_entry_free(p, swp_offset(entry)) == 1) { 385 page = find_get_page(&swapper_space, entry.val); 386 if (page && !trylock_page(page)) { 387 page_cache_release(page); 388 page = NULL; 389 } 390 } 391 spin_unlock(&swap_lock); 392 } 393 if (page) { 394 /* 395 * Not mapped elsewhere, or swap space full? Free it! 396 * Also recheck PageSwapCache now page is locked (above). 397 */ 398 if (PageSwapCache(page) && !PageWriteback(page) && 399 (!page_mapped(page) || vm_swap_full())) { 400 delete_from_swap_cache(page); 401 SetPageDirty(page); 402 } 403 unlock_page(page); 404 page_cache_release(page); 405 } 406} 407 408#ifdef CONFIG_HIBERNATION 409/* 410 * Find the swap type that corresponds to given device (if any). 411 * 412 * @offset - number of the PAGE_SIZE-sized block of the device, starting 413 * from 0, in which the swap header is expected to be located. 414 * 415 * This is needed for the suspend to disk (aka swsusp). 416 */ 417int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p) 418{ 419 struct block_device *bdev = NULL; 420 int i; 421 422 if (device) 423 bdev = bdget(device); 424 425 spin_lock(&swap_lock); 426 for (i = 0; i < nr_swapfiles; i++) { 427 struct swap_info_struct *sis = swap_info + i; 428 429 if (!(sis->flags & SWP_WRITEOK)) 430 continue; 431 432 if (!bdev) { 433 if (bdev_p) 434 *bdev_p = sis->bdev; 435 436 spin_unlock(&swap_lock); 437 return i; 438 } 439 if (bdev == sis->bdev) { 440 struct swap_extent *se; 441 442 se = list_entry(sis->extent_list.next, 443 struct swap_extent, list); 444 if (se->start_block == offset) { 445 if (bdev_p) 446 *bdev_p = sis->bdev; 447 448 spin_unlock(&swap_lock); 449 bdput(bdev); 450 return i; 451 } 452 } 453 } 454 spin_unlock(&swap_lock); 455 if (bdev) 456 bdput(bdev); 457 458 return -ENODEV; 459} 460 461/* 462 * Return either the total number of swap pages of given type, or the number 463 * of free pages of that type (depending on @free) 464 * 465 * This is needed for software suspend 466 */ 467unsigned int count_swap_pages(int type, int free) 468{ 469 unsigned int n = 0; 470 471 if (type < nr_swapfiles) { 472 spin_lock(&swap_lock); 473 if (swap_info[type].flags & SWP_WRITEOK) { 474 n = swap_info[type].pages; 475 if (free) 476 n -= swap_info[type].inuse_pages; 477 } 478 spin_unlock(&swap_lock); 479 } 480 return n; 481} 482#endif 483 484/* 485 * No need to decide whether this PTE shares the swap entry with others, 486 * just let do_wp_page work it out if a write is requested later - to 487 * force COW, vm_page_prot omits write permission from any private vma. 488 */ 489static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, 490 unsigned long addr, swp_entry_t entry, struct page *page) 491{ 492 spinlock_t *ptl; 493 pte_t *pte; 494 int ret = 1; 495 496 if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL)) 497 ret = -ENOMEM; 498 499 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 500 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) { 501 if (ret > 0) 502 mem_cgroup_uncharge_page(page); 503 ret = 0; 504 goto out; 505 } 506 507 inc_mm_counter(vma->vm_mm, anon_rss); 508 get_page(page); 509 set_pte_at(vma->vm_mm, addr, pte, 510 pte_mkold(mk_pte(page, vma->vm_page_prot))); 511 page_add_anon_rmap(page, vma, addr); 512 swap_free(entry); 513 /* 514 * Move the page to the active list so it is not 515 * immediately swapped out again after swapon. 516 */ 517 activate_page(page); 518out: 519 pte_unmap_unlock(pte, ptl); 520 return ret; 521} 522 523static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 524 unsigned long addr, unsigned long end, 525 swp_entry_t entry, struct page *page) 526{ 527 pte_t swp_pte = swp_entry_to_pte(entry); 528 pte_t *pte; 529 int ret = 0; 530 531 /* 532 * We don't actually need pte lock while scanning for swp_pte: since 533 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the 534 * page table while we're scanning; though it could get zapped, and on 535 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse 536 * of unmatched parts which look like swp_pte, so unuse_pte must 537 * recheck under pte lock. Scanning without pte lock lets it be 538 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE. 539 */ 540 pte = pte_offset_map(pmd, addr); 541 do { 542 /* 543 * swapoff spends a _lot_ of time in this loop! 544 * Test inline before going to call unuse_pte. 545 */ 546 if (unlikely(pte_same(*pte, swp_pte))) { 547 pte_unmap(pte); 548 ret = unuse_pte(vma, pmd, addr, entry, page); 549 if (ret) 550 goto out; 551 pte = pte_offset_map(pmd, addr); 552 } 553 } while (pte++, addr += PAGE_SIZE, addr != end); 554 pte_unmap(pte - 1); 555out: 556 return ret; 557} 558 559static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, 560 unsigned long addr, unsigned long end, 561 swp_entry_t entry, struct page *page) 562{ 563 pmd_t *pmd; 564 unsigned long next; 565 int ret; 566 567 pmd = pmd_offset(pud, addr); 568 do { 569 next = pmd_addr_end(addr, end); 570 if (pmd_none_or_clear_bad(pmd)) 571 continue; 572 ret = unuse_pte_range(vma, pmd, addr, next, entry, page); 573 if (ret) 574 return ret; 575 } while (pmd++, addr = next, addr != end); 576 return 0; 577} 578 579static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd, 580 unsigned long addr, unsigned long end, 581 swp_entry_t entry, struct page *page) 582{ 583 pud_t *pud; 584 unsigned long next; 585 int ret; 586 587 pud = pud_offset(pgd, addr); 588 do { 589 next = pud_addr_end(addr, end); 590 if (pud_none_or_clear_bad(pud)) 591 continue; 592 ret = unuse_pmd_range(vma, pud, addr, next, entry, page); 593 if (ret) 594 return ret; 595 } while (pud++, addr = next, addr != end); 596 return 0; 597} 598 599static int unuse_vma(struct vm_area_struct *vma, 600 swp_entry_t entry, struct page *page) 601{ 602 pgd_t *pgd; 603 unsigned long addr, end, next; 604 int ret; 605 606 if (page->mapping) { 607 addr = page_address_in_vma(page, vma); 608 if (addr == -EFAULT) 609 return 0; 610 else 611 end = addr + PAGE_SIZE; 612 } else { 613 addr = vma->vm_start; 614 end = vma->vm_end; 615 } 616 617 pgd = pgd_offset(vma->vm_mm, addr); 618 do { 619 next = pgd_addr_end(addr, end); 620 if (pgd_none_or_clear_bad(pgd)) 621 continue; 622 ret = unuse_pud_range(vma, pgd, addr, next, entry, page); 623 if (ret) 624 return ret; 625 } while (pgd++, addr = next, addr != end); 626 return 0; 627} 628 629static int unuse_mm(struct mm_struct *mm, 630 swp_entry_t entry, struct page *page) 631{ 632 struct vm_area_struct *vma; 633 int ret = 0; 634 635 if (!down_read_trylock(&mm->mmap_sem)) { 636 /* 637 * Activate page so shrink_inactive_list is unlikely to unmap 638 * its ptes while lock is dropped, so swapoff can make progress. 639 */ 640 activate_page(page); 641 unlock_page(page); 642 down_read(&mm->mmap_sem); 643 lock_page(page); 644 } 645 for (vma = mm->mmap; vma; vma = vma->vm_next) { 646 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page))) 647 break; 648 } 649 up_read(&mm->mmap_sem); 650 return (ret < 0)? ret: 0; 651} 652 653/* 654 * Scan swap_map from current position to next entry still in use. 655 * Recycle to start on reaching the end, returning 0 when empty. 656 */ 657static unsigned int find_next_to_unuse(struct swap_info_struct *si, 658 unsigned int prev) 659{ 660 unsigned int max = si->max; 661 unsigned int i = prev; 662 int count; 663 664 /* 665 * No need for swap_lock here: we're just looking 666 * for whether an entry is in use, not modifying it; false 667 * hits are okay, and sys_swapoff() has already prevented new 668 * allocations from this area (while holding swap_lock). 669 */ 670 for (;;) { 671 if (++i >= max) { 672 if (!prev) { 673 i = 0; 674 break; 675 } 676 /* 677 * No entries in use at top of swap_map, 678 * loop back to start and recheck there. 679 */ 680 max = prev + 1; 681 prev = 0; 682 i = 1; 683 } 684 count = si->swap_map[i]; 685 if (count && count != SWAP_MAP_BAD) 686 break; 687 } 688 return i; 689} 690 691/* 692 * We completely avoid races by reading each swap page in advance, 693 * and then search for the process using it. All the necessary 694 * page table adjustments can then be made atomically. 695 */ 696static int try_to_unuse(unsigned int type) 697{ 698 struct swap_info_struct * si = &swap_info[type]; 699 struct mm_struct *start_mm; 700 unsigned short *swap_map; 701 unsigned short swcount; 702 struct page *page; 703 swp_entry_t entry; 704 unsigned int i = 0; 705 int retval = 0; 706 int reset_overflow = 0; 707 int shmem; 708 709 /* 710 * When searching mms for an entry, a good strategy is to 711 * start at the first mm we freed the previous entry from 712 * (though actually we don't notice whether we or coincidence 713 * freed the entry). Initialize this start_mm with a hold. 714 * 715 * A simpler strategy would be to start at the last mm we 716 * freed the previous entry from; but that would take less 717 * advantage of mmlist ordering, which clusters forked mms 718 * together, child after parent. If we race with dup_mmap(), we 719 * prefer to resolve parent before child, lest we miss entries 720 * duplicated after we scanned child: using last mm would invert 721 * that. Though it's only a serious concern when an overflowed 722 * swap count is reset from SWAP_MAP_MAX, preventing a rescan. 723 */ 724 start_mm = &init_mm; 725 atomic_inc(&init_mm.mm_users); 726 727 /* 728 * Keep on scanning until all entries have gone. Usually, 729 * one pass through swap_map is enough, but not necessarily: 730 * there are races when an instance of an entry might be missed. 731 */ 732 while ((i = find_next_to_unuse(si, i)) != 0) { 733 if (signal_pending(current)) { 734 retval = -EINTR; 735 break; 736 } 737 738 /* 739 * Get a page for the entry, using the existing swap 740 * cache page if there is one. Otherwise, get a clean 741 * page and read the swap into it. 742 */ 743 swap_map = &si->swap_map[i]; 744 entry = swp_entry(type, i); 745 page = read_swap_cache_async(entry, 746 GFP_HIGHUSER_MOVABLE, NULL, 0); 747 if (!page) { 748 /* 749 * Either swap_duplicate() failed because entry 750 * has been freed independently, and will not be 751 * reused since sys_swapoff() already disabled 752 * allocation from here, or alloc_page() failed. 753 */ 754 if (!*swap_map) 755 continue; 756 retval = -ENOMEM; 757 break; 758 } 759 760 /* 761 * Don't hold on to start_mm if it looks like exiting. 762 */ 763 if (atomic_read(&start_mm->mm_users) == 1) { 764 mmput(start_mm); 765 start_mm = &init_mm; 766 atomic_inc(&init_mm.mm_users); 767 } 768 769 /* 770 * Wait for and lock page. When do_swap_page races with 771 * try_to_unuse, do_swap_page can handle the fault much 772 * faster than try_to_unuse can locate the entry. This 773 * apparently redundant "wait_on_page_locked" lets try_to_unuse 774 * defer to do_swap_page in such a case - in some tests, 775 * do_swap_page and try_to_unuse repeatedly compete. 776 */ 777 wait_on_page_locked(page); 778 wait_on_page_writeback(page); 779 lock_page(page); 780 wait_on_page_writeback(page); 781 782 /* 783 * Remove all references to entry. 784 * Whenever we reach init_mm, there's no address space 785 * to search, but use it as a reminder to search shmem. 786 */ 787 shmem = 0; 788 swcount = *swap_map; 789 if (swcount > 1) { 790 if (start_mm == &init_mm) 791 shmem = shmem_unuse(entry, page); 792 else 793 retval = unuse_mm(start_mm, entry, page); 794 } 795 if (*swap_map > 1) { 796 int set_start_mm = (*swap_map >= swcount); 797 struct list_head *p = &start_mm->mmlist; 798 struct mm_struct *new_start_mm = start_mm; 799 struct mm_struct *prev_mm = start_mm; 800 struct mm_struct *mm; 801 802 atomic_inc(&new_start_mm->mm_users); 803 atomic_inc(&prev_mm->mm_users); 804 spin_lock(&mmlist_lock); 805 while (*swap_map > 1 && !retval && !shmem && 806 (p = p->next) != &start_mm->mmlist) { 807 mm = list_entry(p, struct mm_struct, mmlist); 808 if (!atomic_inc_not_zero(&mm->mm_users)) 809 continue; 810 spin_unlock(&mmlist_lock); 811 mmput(prev_mm); 812 prev_mm = mm; 813 814 cond_resched(); 815 816 swcount = *swap_map; 817 if (swcount <= 1) 818 ; 819 else if (mm == &init_mm) { 820 set_start_mm = 1; 821 shmem = shmem_unuse(entry, page); 822 } else 823 retval = unuse_mm(mm, entry, page); 824 if (set_start_mm && *swap_map < swcount) { 825 mmput(new_start_mm); 826 atomic_inc(&mm->mm_users); 827 new_start_mm = mm; 828 set_start_mm = 0; 829 } 830 spin_lock(&mmlist_lock); 831 } 832 spin_unlock(&mmlist_lock); 833 mmput(prev_mm); 834 mmput(start_mm); 835 start_mm = new_start_mm; 836 } 837 if (shmem) { 838 /* page has already been unlocked and released */ 839 if (shmem > 0) 840 continue; 841 retval = shmem; 842 break; 843 } 844 if (retval) { 845 unlock_page(page); 846 page_cache_release(page); 847 break; 848 } 849 850 /* 851 * How could swap count reach 0x7fff when the maximum 852 * pid is 0x7fff, and there's no way to repeat a swap 853 * page within an mm (except in shmem, where it's the 854 * shared object which takes the reference count)? 855 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4. 856 * 857 * If that's wrong, then we should worry more about 858 * exit_mmap() and do_munmap() cases described above: 859 * we might be resetting SWAP_MAP_MAX too early here. 860 * We know "Undead"s can happen, they're okay, so don't 861 * report them; but do report if we reset SWAP_MAP_MAX. 862 */ 863 if (*swap_map == SWAP_MAP_MAX) { 864 spin_lock(&swap_lock); 865 *swap_map = 1; 866 spin_unlock(&swap_lock); 867 reset_overflow = 1; 868 } 869 870 /* 871 * If a reference remains (rare), we would like to leave 872 * the page in the swap cache; but try_to_unmap could 873 * then re-duplicate the entry once we drop page lock, 874 * so we might loop indefinitely; also, that page could 875 * not be swapped out to other storage meanwhile. So: 876 * delete from cache even if there's another reference, 877 * after ensuring that the data has been saved to disk - 878 * since if the reference remains (rarer), it will be 879 * read from disk into another page. Splitting into two 880 * pages would be incorrect if swap supported "shared 881 * private" pages, but they are handled by tmpfs files. 882 */ 883 if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) { 884 struct writeback_control wbc = { 885 .sync_mode = WB_SYNC_NONE, 886 }; 887 888 swap_writepage(page, &wbc); 889 lock_page(page); 890 wait_on_page_writeback(page); 891 } 892 893 /* 894 * It is conceivable that a racing task removed this page from 895 * swap cache just before we acquired the page lock at the top, 896 * or while we dropped it in unuse_mm(). The page might even 897 * be back in swap cache on another swap area: that we must not 898 * delete, since it may not have been written out to swap yet. 899 */ 900 if (PageSwapCache(page) && 901 likely(page_private(page) == entry.val)) 902 delete_from_swap_cache(page); 903 904 /* 905 * So we could skip searching mms once swap count went 906 * to 1, we did not mark any present ptes as dirty: must 907 * mark page dirty so shrink_page_list will preserve it. 908 */ 909 SetPageDirty(page); 910 unlock_page(page); 911 page_cache_release(page); 912 913 /* 914 * Make sure that we aren't completely killing 915 * interactive performance. 916 */ 917 cond_resched(); 918 } 919 920 mmput(start_mm); 921 if (reset_overflow) { 922 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n"); 923 swap_overflow = 0; 924 } 925 return retval; 926} 927 928/* 929 * After a successful try_to_unuse, if no swap is now in use, we know 930 * we can empty the mmlist. swap_lock must be held on entry and exit. 931 * Note that mmlist_lock nests inside swap_lock, and an mm must be 932 * added to the mmlist just after page_duplicate - before would be racy. 933 */ 934static void drain_mmlist(void) 935{ 936 struct list_head *p, *next; 937 unsigned int i; 938 939 for (i = 0; i < nr_swapfiles; i++) 940 if (swap_info[i].inuse_pages) 941 return; 942 spin_lock(&mmlist_lock); 943 list_for_each_safe(p, next, &init_mm.mmlist) 944 list_del_init(p); 945 spin_unlock(&mmlist_lock); 946} 947 948/* 949 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which 950 * corresponds to page offset `offset'. 951 */ 952sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset) 953{ 954 struct swap_extent *se = sis->curr_swap_extent; 955 struct swap_extent *start_se = se; 956 957 for ( ; ; ) { 958 struct list_head *lh; 959 960 if (se->start_page <= offset && 961 offset < (se->start_page + se->nr_pages)) { 962 return se->start_block + (offset - se->start_page); 963 } 964 lh = se->list.next; 965 if (lh == &sis->extent_list) 966 lh = lh->next; 967 se = list_entry(lh, struct swap_extent, list); 968 sis->curr_swap_extent = se; 969 BUG_ON(se == start_se); /* It *must* be present */ 970 } 971} 972 973#ifdef CONFIG_HIBERNATION 974/* 975 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev 976 * corresponding to given index in swap_info (swap type). 977 */ 978sector_t swapdev_block(int swap_type, pgoff_t offset) 979{ 980 struct swap_info_struct *sis; 981 982 if (swap_type >= nr_swapfiles) 983 return 0; 984 985 sis = swap_info + swap_type; 986 return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0; 987} 988#endif /* CONFIG_HIBERNATION */ 989 990/* 991 * Free all of a swapdev's extent information 992 */ 993static void destroy_swap_extents(struct swap_info_struct *sis) 994{ 995 while (!list_empty(&sis->extent_list)) { 996 struct swap_extent *se; 997 998 se = list_entry(sis->extent_list.next, 999 struct swap_extent, list); 1000 list_del(&se->list); 1001 kfree(se); 1002 } 1003} 1004 1005/* 1006 * Add a block range (and the corresponding page range) into this swapdev's 1007 * extent list. The extent list is kept sorted in page order. 1008 * 1009 * This function rather assumes that it is called in ascending page order. 1010 */ 1011static int 1012add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, 1013 unsigned long nr_pages, sector_t start_block) 1014{ 1015 struct swap_extent *se; 1016 struct swap_extent *new_se; 1017 struct list_head *lh; 1018 1019 lh = sis->extent_list.prev; /* The highest page extent */ 1020 if (lh != &sis->extent_list) { 1021 se = list_entry(lh, struct swap_extent, list); 1022 BUG_ON(se->start_page + se->nr_pages != start_page); 1023 if (se->start_block + se->nr_pages == start_block) { 1024 /* Merge it */ 1025 se->nr_pages += nr_pages; 1026 return 0; 1027 } 1028 } 1029 1030 /* 1031 * No merge. Insert a new extent, preserving ordering. 1032 */ 1033 new_se = kmalloc(sizeof(*se), GFP_KERNEL); 1034 if (new_se == NULL) 1035 return -ENOMEM; 1036 new_se->start_page = start_page; 1037 new_se->nr_pages = nr_pages; 1038 new_se->start_block = start_block; 1039 1040 list_add_tail(&new_se->list, &sis->extent_list); 1041 return 1; 1042} 1043 1044/* 1045 * A `swap extent' is a simple thing which maps a contiguous range of pages 1046 * onto a contiguous range of disk blocks. An ordered list of swap extents 1047 * is built at swapon time and is then used at swap_writepage/swap_readpage 1048 * time for locating where on disk a page belongs. 1049 * 1050 * If the swapfile is an S_ISBLK block device, a single extent is installed. 1051 * This is done so that the main operating code can treat S_ISBLK and S_ISREG 1052 * swap files identically. 1053 * 1054 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap 1055 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK 1056 * swapfiles are handled *identically* after swapon time. 1057 * 1058 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks 1059 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If 1060 * some stray blocks are found which do not fall within the PAGE_SIZE alignment 1061 * requirements, they are simply tossed out - we will never use those blocks 1062 * for swapping. 1063 * 1064 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This 1065 * prevents root from shooting her foot off by ftruncating an in-use swapfile, 1066 * which will scribble on the fs. 1067 * 1068 * The amount of disk space which a single swap extent represents varies. 1069 * Typically it is in the 1-4 megabyte range. So we can have hundreds of 1070 * extents in the list. To avoid much list walking, we cache the previous 1071 * search location in `curr_swap_extent', and start new searches from there. 1072 * This is extremely effective. The average number of iterations in 1073 * map_swap_page() has been measured at about 0.3 per page. - akpm. 1074 */ 1075static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) 1076{ 1077 struct inode *inode; 1078 unsigned blocks_per_page; 1079 unsigned long page_no; 1080 unsigned blkbits; 1081 sector_t probe_block; 1082 sector_t last_block; 1083 sector_t lowest_block = -1; 1084 sector_t highest_block = 0; 1085 int nr_extents = 0; 1086 int ret; 1087 1088 inode = sis->swap_file->f_mapping->host; 1089 if (S_ISBLK(inode->i_mode)) { 1090 ret = add_swap_extent(sis, 0, sis->max, 0); 1091 *span = sis->pages; 1092 goto done; 1093 } 1094 1095 blkbits = inode->i_blkbits; 1096 blocks_per_page = PAGE_SIZE >> blkbits; 1097 1098 /* 1099 * Map all the blocks into the extent list. This code doesn't try 1100 * to be very smart. 1101 */ 1102 probe_block = 0; 1103 page_no = 0; 1104 last_block = i_size_read(inode) >> blkbits; 1105 while ((probe_block + blocks_per_page) <= last_block && 1106 page_no < sis->max) { 1107 unsigned block_in_page; 1108 sector_t first_block; 1109 1110 first_block = bmap(inode, probe_block); 1111 if (first_block == 0) 1112 goto bad_bmap; 1113 1114 /* 1115 * It must be PAGE_SIZE aligned on-disk 1116 */ 1117 if (first_block & (blocks_per_page - 1)) { 1118 probe_block++; 1119 goto reprobe; 1120 } 1121 1122 for (block_in_page = 1; block_in_page < blocks_per_page; 1123 block_in_page++) { 1124 sector_t block; 1125 1126 block = bmap(inode, probe_block + block_in_page); 1127 if (block == 0) 1128 goto bad_bmap; 1129 if (block != first_block + block_in_page) { 1130 /* Discontiguity */ 1131 probe_block++; 1132 goto reprobe; 1133 } 1134 } 1135 1136 first_block >>= (PAGE_SHIFT - blkbits); 1137 if (page_no) { /* exclude the header page */ 1138 if (first_block < lowest_block) 1139 lowest_block = first_block; 1140 if (first_block > highest_block) 1141 highest_block = first_block; 1142 } 1143 1144 /* 1145 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 1146 */ 1147 ret = add_swap_extent(sis, page_no, 1, first_block); 1148 if (ret < 0) 1149 goto out; 1150 nr_extents += ret; 1151 page_no++; 1152 probe_block += blocks_per_page; 1153reprobe: 1154 continue; 1155 } 1156 ret = nr_extents; 1157 *span = 1 + highest_block - lowest_block; 1158 if (page_no == 0) 1159 page_no = 1; /* force Empty message */ 1160 sis->max = page_no; 1161 sis->pages = page_no - 1; 1162 sis->highest_bit = page_no - 1; 1163done: 1164 sis->curr_swap_extent = list_entry(sis->extent_list.prev, 1165 struct swap_extent, list); 1166 goto out; 1167bad_bmap: 1168 printk(KERN_ERR "swapon: swapfile has holes\n"); 1169 ret = -EINVAL; 1170out: 1171 return ret; 1172} 1173 1174#if 0 /* We don't need this yet */ 1175#include <linux/backing-dev.h> 1176int page_queue_congested(struct page *page) 1177{ 1178 struct backing_dev_info *bdi; 1179 1180 VM_BUG_ON(!PageLocked(page)); /* It pins the swap_info_struct */ 1181 1182 if (PageSwapCache(page)) { 1183 swp_entry_t entry = { .val = page_private(page) }; 1184 struct swap_info_struct *sis; 1185 1186 sis = get_swap_info_struct(swp_type(entry)); 1187 bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info; 1188 } else 1189 bdi = page->mapping->backing_dev_info; 1190 return bdi_write_congested(bdi); 1191} 1192#endif 1193 1194asmlinkage long sys_swapoff(const char __user * specialfile) 1195{ 1196 struct swap_info_struct * p = NULL; 1197 unsigned short *swap_map; 1198 struct file *swap_file, *victim; 1199 struct address_space *mapping; 1200 struct inode *inode; 1201 char * pathname; 1202 int i, type, prev; 1203 int err; 1204 1205 if (!capable(CAP_SYS_ADMIN)) 1206 return -EPERM; 1207 1208 pathname = getname(specialfile); 1209 err = PTR_ERR(pathname); 1210 if (IS_ERR(pathname)) 1211 goto out; 1212 1213 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0); 1214 putname(pathname); 1215 err = PTR_ERR(victim); 1216 if (IS_ERR(victim)) 1217 goto out; 1218 1219 mapping = victim->f_mapping; 1220 prev = -1; 1221 spin_lock(&swap_lock); 1222 for (type = swap_list.head; type >= 0; type = swap_info[type].next) { 1223 p = swap_info + type; 1224 if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) { 1225 if (p->swap_file->f_mapping == mapping) 1226 break; 1227 } 1228 prev = type; 1229 } 1230 if (type < 0) { 1231 err = -EINVAL; 1232 spin_unlock(&swap_lock); 1233 goto out_dput; 1234 } 1235 if (!security_vm_enough_memory(p->pages)) 1236 vm_unacct_memory(p->pages); 1237 else { 1238 err = -ENOMEM; 1239 spin_unlock(&swap_lock); 1240 goto out_dput; 1241 } 1242 if (prev < 0) { 1243 swap_list.head = p->next; 1244 } else { 1245 swap_info[prev].next = p->next; 1246 } 1247 if (type == swap_list.next) { 1248 /* just pick something that's safe... */ 1249 swap_list.next = swap_list.head; 1250 } 1251 if (p->prio < 0) { 1252 for (i = p->next; i >= 0; i = swap_info[i].next) 1253 swap_info[i].prio = p->prio--; 1254 least_priority++; 1255 } 1256 nr_swap_pages -= p->pages; 1257 total_swap_pages -= p->pages; 1258 p->flags &= ~SWP_WRITEOK; 1259 spin_unlock(&swap_lock); 1260 1261 current->flags |= PF_SWAPOFF; 1262 err = try_to_unuse(type); 1263 current->flags &= ~PF_SWAPOFF; 1264 1265 if (err) { 1266 /* re-insert swap space back into swap_list */ 1267 spin_lock(&swap_lock); 1268 if (p->prio < 0) 1269 p->prio = --least_priority; 1270 prev = -1; 1271 for (i = swap_list.head; i >= 0; i = swap_info[i].next) { 1272 if (p->prio >= swap_info[i].prio) 1273 break; 1274 prev = i; 1275 } 1276 p->next = i; 1277 if (prev < 0) 1278 swap_list.head = swap_list.next = p - swap_info; 1279 else 1280 swap_info[prev].next = p - swap_info; 1281 nr_swap_pages += p->pages; 1282 total_swap_pages += p->pages; 1283 p->flags |= SWP_WRITEOK; 1284 spin_unlock(&swap_lock); 1285 goto out_dput; 1286 } 1287 1288 /* wait for any unplug function to finish */ 1289 down_write(&swap_unplug_sem); 1290 up_write(&swap_unplug_sem); 1291 1292 destroy_swap_extents(p); 1293 mutex_lock(&swapon_mutex); 1294 spin_lock(&swap_lock); 1295 drain_mmlist(); 1296 1297 /* wait for anyone still in scan_swap_map */ 1298 p->highest_bit = 0; /* cuts scans short */ 1299 while (p->flags >= SWP_SCANNING) { 1300 spin_unlock(&swap_lock); 1301 schedule_timeout_uninterruptible(1); 1302 spin_lock(&swap_lock); 1303 } 1304 1305 swap_file = p->swap_file; 1306 p->swap_file = NULL; 1307 p->max = 0; 1308 swap_map = p->swap_map; 1309 p->swap_map = NULL; 1310 p->flags = 0; 1311 spin_unlock(&swap_lock); 1312 mutex_unlock(&swapon_mutex); 1313 vfree(swap_map); 1314 inode = mapping->host; 1315 if (S_ISBLK(inode->i_mode)) { 1316 struct block_device *bdev = I_BDEV(inode); 1317 set_blocksize(bdev, p->old_block_size); 1318 bd_release(bdev); 1319 } else { 1320 mutex_lock(&inode->i_mutex); 1321 inode->i_flags &= ~S_SWAPFILE; 1322 mutex_unlock(&inode->i_mutex); 1323 } 1324 filp_close(swap_file, NULL); 1325 err = 0; 1326 1327out_dput: 1328 filp_close(victim, NULL); 1329out: 1330 return err; 1331} 1332 1333#ifdef CONFIG_PROC_FS 1334/* iterator */ 1335static void *swap_start(struct seq_file *swap, loff_t *pos) 1336{ 1337 struct swap_info_struct *ptr = swap_info; 1338 int i; 1339 loff_t l = *pos; 1340 1341 mutex_lock(&swapon_mutex); 1342 1343 if (!l) 1344 return SEQ_START_TOKEN; 1345 1346 for (i = 0; i < nr_swapfiles; i++, ptr++) { 1347 if (!(ptr->flags & SWP_USED) || !ptr->swap_map) 1348 continue; 1349 if (!--l) 1350 return ptr; 1351 } 1352 1353 return NULL; 1354} 1355 1356static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) 1357{ 1358 struct swap_info_struct *ptr; 1359 struct swap_info_struct *endptr = swap_info + nr_swapfiles; 1360 1361 if (v == SEQ_START_TOKEN) 1362 ptr = swap_info; 1363 else { 1364 ptr = v; 1365 ptr++; 1366 } 1367 1368 for (; ptr < endptr; ptr++) { 1369 if (!(ptr->flags & SWP_USED) || !ptr->swap_map) 1370 continue; 1371 ++*pos; 1372 return ptr; 1373 } 1374 1375 return NULL; 1376} 1377 1378static void swap_stop(struct seq_file *swap, void *v) 1379{ 1380 mutex_unlock(&swapon_mutex); 1381} 1382 1383static int swap_show(struct seq_file *swap, void *v) 1384{ 1385 struct swap_info_struct *ptr = v; 1386 struct file *file; 1387 int len; 1388 1389 if (ptr == SEQ_START_TOKEN) { 1390 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); 1391 return 0; 1392 } 1393 1394 file = ptr->swap_file; 1395 len = seq_path(swap, &file->f_path, " \t\n\\"); 1396 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n", 1397 len < 40 ? 40 - len : 1, " ", 1398 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ? 1399 "partition" : "file\t", 1400 ptr->pages << (PAGE_SHIFT - 10), 1401 ptr->inuse_pages << (PAGE_SHIFT - 10), 1402 ptr->prio); 1403 return 0; 1404} 1405 1406static const struct seq_operations swaps_op = { 1407 .start = swap_start, 1408 .next = swap_next, 1409 .stop = swap_stop, 1410 .show = swap_show 1411}; 1412 1413static int swaps_open(struct inode *inode, struct file *file) 1414{ 1415 return seq_open(file, &swaps_op); 1416} 1417 1418static const struct file_operations proc_swaps_operations = { 1419 .open = swaps_open, 1420 .read = seq_read, 1421 .llseek = seq_lseek, 1422 .release = seq_release, 1423}; 1424 1425static int __init procswaps_init(void) 1426{ 1427 proc_create("swaps", 0, NULL, &proc_swaps_operations); 1428 return 0; 1429} 1430__initcall(procswaps_init); 1431#endif /* CONFIG_PROC_FS */ 1432 1433#ifdef MAX_SWAPFILES_CHECK 1434static int __init max_swapfiles_check(void) 1435{ 1436 MAX_SWAPFILES_CHECK(); 1437 return 0; 1438} 1439late_initcall(max_swapfiles_check); 1440#endif 1441 1442/* 1443 * Written 01/25/92 by Simmule Turner, heavily changed by Linus. 1444 * 1445 * The swapon system call 1446 */ 1447asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags) 1448{ 1449 struct swap_info_struct * p; 1450 char *name = NULL; 1451 struct block_device *bdev = NULL; 1452 struct file *swap_file = NULL; 1453 struct address_space *mapping; 1454 unsigned int type; 1455 int i, prev; 1456 int error; 1457 union swap_header *swap_header = NULL; 1458 int swap_header_version; 1459 unsigned int nr_good_pages = 0; 1460 int nr_extents = 0; 1461 sector_t span; 1462 unsigned long maxpages = 1; 1463 int swapfilesize; 1464 unsigned short *swap_map = NULL; 1465 struct page *page = NULL; 1466 struct inode *inode = NULL; 1467 int did_down = 0; 1468 1469 if (!capable(CAP_SYS_ADMIN)) 1470 return -EPERM; 1471 spin_lock(&swap_lock); 1472 p = swap_info; 1473 for (type = 0 ; type < nr_swapfiles ; type++,p++) 1474 if (!(p->flags & SWP_USED)) 1475 break; 1476 error = -EPERM; 1477 if (type >= MAX_SWAPFILES) { 1478 spin_unlock(&swap_lock); 1479 goto out; 1480 } 1481 if (type >= nr_swapfiles) 1482 nr_swapfiles = type+1; 1483 memset(p, 0, sizeof(*p)); 1484 INIT_LIST_HEAD(&p->extent_list); 1485 p->flags = SWP_USED; 1486 p->next = -1; 1487 spin_unlock(&swap_lock); 1488 name = getname(specialfile); 1489 error = PTR_ERR(name); 1490 if (IS_ERR(name)) { 1491 name = NULL; 1492 goto bad_swap_2; 1493 } 1494 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0); 1495 error = PTR_ERR(swap_file); 1496 if (IS_ERR(swap_file)) { 1497 swap_file = NULL; 1498 goto bad_swap_2; 1499 } 1500 1501 p->swap_file = swap_file; 1502 mapping = swap_file->f_mapping; 1503 inode = mapping->host; 1504 1505 error = -EBUSY; 1506 for (i = 0; i < nr_swapfiles; i++) { 1507 struct swap_info_struct *q = &swap_info[i]; 1508 1509 if (i == type || !q->swap_file) 1510 continue; 1511 if (mapping == q->swap_file->f_mapping) 1512 goto bad_swap; 1513 } 1514 1515 error = -EINVAL; 1516 if (S_ISBLK(inode->i_mode)) { 1517 bdev = I_BDEV(inode); 1518 error = bd_claim(bdev, sys_swapon); 1519 if (error < 0) { 1520 bdev = NULL; 1521 error = -EINVAL; 1522 goto bad_swap; 1523 } 1524 p->old_block_size = block_size(bdev); 1525 error = set_blocksize(bdev, PAGE_SIZE); 1526 if (error < 0) 1527 goto bad_swap; 1528 p->bdev = bdev; 1529 } else if (S_ISREG(inode->i_mode)) { 1530 p->bdev = inode->i_sb->s_bdev; 1531 mutex_lock(&inode->i_mutex); 1532 did_down = 1; 1533 if (IS_SWAPFILE(inode)) { 1534 error = -EBUSY; 1535 goto bad_swap; 1536 } 1537 } else { 1538 goto bad_swap; 1539 } 1540 1541 swapfilesize = i_size_read(inode) >> PAGE_SHIFT; 1542 1543 /* 1544 * Read the swap header. 1545 */ 1546 if (!mapping->a_ops->readpage) { 1547 error = -EINVAL; 1548 goto bad_swap; 1549 } 1550 page = read_mapping_page(mapping, 0, swap_file); 1551 if (IS_ERR(page)) { 1552 error = PTR_ERR(page); 1553 goto bad_swap; 1554 } 1555 kmap(page); 1556 swap_header = page_address(page); 1557 1558 if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10)) 1559 swap_header_version = 1; 1560 else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10)) 1561 swap_header_version = 2; 1562 else { 1563 printk(KERN_ERR "Unable to find swap-space signature\n"); 1564 error = -EINVAL; 1565 goto bad_swap; 1566 } 1567 1568 switch (swap_header_version) { 1569 case 1: 1570 printk(KERN_ERR "version 0 swap is no longer supported. " 1571 "Use mkswap -v1 %s\n", name); 1572 error = -EINVAL; 1573 goto bad_swap; 1574 case 2: 1575 /* swap partition endianess hack... */ 1576 if (swab32(swap_header->info.version) == 1) { 1577 swab32s(&swap_header->info.version); 1578 swab32s(&swap_header->info.last_page); 1579 swab32s(&swap_header->info.nr_badpages); 1580 for (i = 0; i < swap_header->info.nr_badpages; i++) 1581 swab32s(&swap_header->info.badpages[i]); 1582 } 1583 /* Check the swap header's sub-version and the size of 1584 the swap file and bad block lists */ 1585 if (swap_header->info.version != 1) { 1586 printk(KERN_WARNING 1587 "Unable to handle swap header version %d\n", 1588 swap_header->info.version); 1589 error = -EINVAL; 1590 goto bad_swap; 1591 } 1592 1593 p->lowest_bit = 1; 1594 p->cluster_next = 1; 1595 1596 /* 1597 * Find out how many pages are allowed for a single swap 1598 * device. There are two limiting factors: 1) the number of 1599 * bits for the swap offset in the swp_entry_t type and 1600 * 2) the number of bits in the a swap pte as defined by 1601 * the different architectures. In order to find the 1602 * largest possible bit mask a swap entry with swap type 0 1603 * and swap offset ~0UL is created, encoded to a swap pte, 1604 * decoded to a swp_entry_t again and finally the swap 1605 * offset is extracted. This will mask all the bits from 1606 * the initial ~0UL mask that can't be encoded in either 1607 * the swp_entry_t or the architecture definition of a 1608 * swap pte. 1609 */ 1610 maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1; 1611 if (maxpages > swap_header->info.last_page) 1612 maxpages = swap_header->info.last_page; 1613 p->highest_bit = maxpages - 1; 1614 1615 error = -EINVAL; 1616 if (!maxpages) 1617 goto bad_swap; 1618 if (swapfilesize && maxpages > swapfilesize) { 1619 printk(KERN_WARNING 1620 "Swap area shorter than signature indicates\n"); 1621 goto bad_swap; 1622 } 1623 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) 1624 goto bad_swap; 1625 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) 1626 goto bad_swap; 1627 1628 /* OK, set up the swap map and apply the bad block list */ 1629 swap_map = vmalloc(maxpages * sizeof(short)); 1630 if (!swap_map) { 1631 error = -ENOMEM; 1632 goto bad_swap; 1633 } 1634 1635 error = 0; 1636 memset(swap_map, 0, maxpages * sizeof(short)); 1637 for (i = 0; i < swap_header->info.nr_badpages; i++) { 1638 int page_nr = swap_header->info.badpages[i]; 1639 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) 1640 error = -EINVAL; 1641 else 1642 swap_map[page_nr] = SWAP_MAP_BAD; 1643 } 1644 nr_good_pages = swap_header->info.last_page - 1645 swap_header->info.nr_badpages - 1646 1 /* header page */; 1647 if (error) 1648 goto bad_swap; 1649 } 1650 1651 if (nr_good_pages) { 1652 swap_map[0] = SWAP_MAP_BAD; 1653 p->max = maxpages; 1654 p->pages = nr_good_pages; 1655 nr_extents = setup_swap_extents(p, &span); 1656 if (nr_extents < 0) { 1657 error = nr_extents; 1658 goto bad_swap; 1659 } 1660 nr_good_pages = p->pages; 1661 } 1662 if (!nr_good_pages) { 1663 printk(KERN_WARNING "Empty swap-file\n"); 1664 error = -EINVAL; 1665 goto bad_swap; 1666 } 1667 1668 mutex_lock(&swapon_mutex); 1669 spin_lock(&swap_lock); 1670 if (swap_flags & SWAP_FLAG_PREFER) 1671 p->prio = 1672 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; 1673 else 1674 p->prio = --least_priority; 1675 p->swap_map = swap_map; 1676 p->flags = SWP_ACTIVE; 1677 nr_swap_pages += nr_good_pages; 1678 total_swap_pages += nr_good_pages; 1679 1680 printk(KERN_INFO "Adding %uk swap on %s. " 1681 "Priority:%d extents:%d across:%lluk\n", 1682 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio, 1683 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10)); 1684 1685 /* insert swap space into swap_list: */ 1686 prev = -1; 1687 for (i = swap_list.head; i >= 0; i = swap_info[i].next) { 1688 if (p->prio >= swap_info[i].prio) { 1689 break; 1690 } 1691 prev = i; 1692 } 1693 p->next = i; 1694 if (prev < 0) { 1695 swap_list.head = swap_list.next = p - swap_info; 1696 } else { 1697 swap_info[prev].next = p - swap_info; 1698 } 1699 spin_unlock(&swap_lock); 1700 mutex_unlock(&swapon_mutex); 1701 error = 0; 1702 goto out; 1703bad_swap: 1704 if (bdev) { 1705 set_blocksize(bdev, p->old_block_size); 1706 bd_release(bdev); 1707 } 1708 destroy_swap_extents(p); 1709bad_swap_2: 1710 spin_lock(&swap_lock); 1711 p->swap_file = NULL; 1712 p->flags = 0; 1713 spin_unlock(&swap_lock); 1714 vfree(swap_map); 1715 if (swap_file) 1716 filp_close(swap_file, NULL); 1717out: 1718 if (page && !IS_ERR(page)) { 1719 kunmap(page); 1720 page_cache_release(page); 1721 } 1722 if (name) 1723 putname(name); 1724 if (did_down) { 1725 if (!error) 1726 inode->i_flags |= S_SWAPFILE; 1727 mutex_unlock(&inode->i_mutex); 1728 } 1729 return error; 1730} 1731 1732void si_swapinfo(struct sysinfo *val) 1733{ 1734 unsigned int i; 1735 unsigned long nr_to_be_unused = 0; 1736 1737 spin_lock(&swap_lock); 1738 for (i = 0; i < nr_swapfiles; i++) { 1739 if (!(swap_info[i].flags & SWP_USED) || 1740 (swap_info[i].flags & SWP_WRITEOK)) 1741 continue; 1742 nr_to_be_unused += swap_info[i].inuse_pages; 1743 } 1744 val->freeswap = nr_swap_pages + nr_to_be_unused; 1745 val->totalswap = total_swap_pages + nr_to_be_unused; 1746 spin_unlock(&swap_lock); 1747} 1748 1749/* 1750 * Verify that a swap entry is valid and increment its swap map count. 1751 * 1752 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as 1753 * "permanent", but will be reclaimed by the next swapoff. 1754 */ 1755int swap_duplicate(swp_entry_t entry) 1756{ 1757 struct swap_info_struct * p; 1758 unsigned long offset, type; 1759 int result = 0; 1760 1761 if (is_migration_entry(entry)) 1762 return 1; 1763 1764 type = swp_type(entry); 1765 if (type >= nr_swapfiles) 1766 goto bad_file; 1767 p = type + swap_info; 1768 offset = swp_offset(entry); 1769 1770 spin_lock(&swap_lock); 1771 if (offset < p->max && p->swap_map[offset]) { 1772 if (p->swap_map[offset] < SWAP_MAP_MAX - 1) { 1773 p->swap_map[offset]++; 1774 result = 1; 1775 } else if (p->swap_map[offset] <= SWAP_MAP_MAX) { 1776 if (swap_overflow++ < 5) 1777 printk(KERN_WARNING "swap_dup: swap entry overflow\n"); 1778 p->swap_map[offset] = SWAP_MAP_MAX; 1779 result = 1; 1780 } 1781 } 1782 spin_unlock(&swap_lock); 1783out: 1784 return result; 1785 1786bad_file: 1787 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); 1788 goto out; 1789} 1790 1791struct swap_info_struct * 1792get_swap_info_struct(unsigned type) 1793{ 1794 return &swap_info[type]; 1795} 1796 1797/* 1798 * swap_lock prevents swap_map being freed. Don't grab an extra 1799 * reference on the swaphandle, it doesn't matter if it becomes unused. 1800 */ 1801int valid_swaphandles(swp_entry_t entry, unsigned long *offset) 1802{ 1803 struct swap_info_struct *si; 1804 int our_page_cluster = page_cluster; 1805 pgoff_t target, toff; 1806 pgoff_t base, end; 1807 int nr_pages = 0; 1808 1809 if (!our_page_cluster) /* no readahead */ 1810 return 0; 1811 1812 si = &swap_info[swp_type(entry)]; 1813 target = swp_offset(entry); 1814 base = (target >> our_page_cluster) << our_page_cluster; 1815 end = base + (1 << our_page_cluster); 1816 if (!base) /* first page is swap header */ 1817 base++; 1818 1819 spin_lock(&swap_lock); 1820 if (end > si->max) /* don't go beyond end of map */ 1821 end = si->max; 1822 1823 /* Count contiguous allocated slots above our target */ 1824 for (toff = target; ++toff < end; nr_pages++) { 1825 /* Don't read in free or bad pages */ 1826 if (!si->swap_map[toff]) 1827 break; 1828 if (si->swap_map[toff] == SWAP_MAP_BAD) 1829 break; 1830 } 1831 /* Count contiguous allocated slots below our target */ 1832 for (toff = target; --toff >= base; nr_pages++) { 1833 /* Don't read in free or bad pages */ 1834 if (!si->swap_map[toff]) 1835 break; 1836 if (si->swap_map[toff] == SWAP_MAP_BAD) 1837 break; 1838 } 1839 spin_unlock(&swap_lock); 1840 1841 /* 1842 * Indicate starting offset, and return number of pages to get: 1843 * if only 1, say 0, since there's then no readahead to be done. 1844 */ 1845 *offset = ++toff; 1846 return nr_pages? ++nr_pages: 0; 1847} 1848