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/random.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/ksm.h> 26 #include <linux/rmap.h> 27 #include <linux/security.h> 28 #include <linux/backing-dev.h> 29 #include <linux/mutex.h> 30 #include <linux/capability.h> 31 #include <linux/syscalls.h> 32 #include <linux/memcontrol.h> 33 34 #include <asm/pgtable.h> 35 #include <asm/tlbflush.h> 36 #include <linux/swapops.h> 37 #include <linux/page_cgroup.h> 38 39 static bool swap_count_continued(struct swap_info_struct *, pgoff_t, 40 unsigned char); 41 static void free_swap_count_continuations(struct swap_info_struct *); 42 static sector_t map_swap_entry(swp_entry_t, struct block_device**); 43 44 static DEFINE_SPINLOCK(swap_lock); 45 static unsigned int nr_swapfiles; 46 long nr_swap_pages; 47 long total_swap_pages; 48 static int least_priority; 49 50 static const char Bad_file[] = "Bad swap file entry "; 51 static const char Unused_file[] = "Unused swap file entry "; 52 static const char Bad_offset[] = "Bad swap offset entry "; 53 static const char Unused_offset[] = "Unused swap offset entry "; 54 55 static struct swap_list_t swap_list = {-1, -1}; 56 57 static struct swap_info_struct *swap_info[MAX_SWAPFILES]; 58 59 static DEFINE_MUTEX(swapon_mutex); 60 61 static inline unsigned char swap_count(unsigned char ent) 62 { 63 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */ 64 } 65 66 /* returns 1 if swap entry is freed */ 67 static int 68 __try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset) 69 { 70 swp_entry_t entry = swp_entry(si->type, offset); 71 struct page *page; 72 int ret = 0; 73 74 page = find_get_page(&swapper_space, entry.val); 75 if (!page) 76 return 0; 77 /* 78 * This function is called from scan_swap_map() and it's called 79 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here. 80 * We have to use trylock for avoiding deadlock. This is a special 81 * case and you should use try_to_free_swap() with explicit lock_page() 82 * in usual operations. 83 */ 84 if (trylock_page(page)) { 85 ret = try_to_free_swap(page); 86 unlock_page(page); 87 } 88 page_cache_release(page); 89 return ret; 90 } 91 92 /* 93 * We need this because the bdev->unplug_fn can sleep and we cannot 94 * hold swap_lock while calling the unplug_fn. And swap_lock 95 * cannot be turned into a mutex. 96 */ 97 static DECLARE_RWSEM(swap_unplug_sem); 98 99 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page) 100 { 101 swp_entry_t entry; 102 103 down_read(&swap_unplug_sem); 104 entry.val = page_private(page); 105 if (PageSwapCache(page)) { 106 struct block_device *bdev = swap_info[swp_type(entry)]->bdev; 107 struct backing_dev_info *bdi; 108 109 /* 110 * If the page is removed from swapcache from under us (with a 111 * racy try_to_unuse/swapoff) we need an additional reference 112 * count to avoid reading garbage from page_private(page) above. 113 * If the WARN_ON triggers during a swapoff it maybe the race 114 * condition and it's harmless. However if it triggers without 115 * swapoff it signals a problem. 116 */ 117 WARN_ON(page_count(page) <= 1); 118 119 bdi = bdev->bd_inode->i_mapping->backing_dev_info; 120 blk_run_backing_dev(bdi, page); 121 } 122 up_read(&swap_unplug_sem); 123 } 124 125 /* 126 * swapon tell device that all the old swap contents can be discarded, 127 * to allow the swap device to optimize its wear-levelling. 128 */ 129 static int discard_swap(struct swap_info_struct *si) 130 { 131 struct swap_extent *se; 132 sector_t start_block; 133 sector_t nr_blocks; 134 int err = 0; 135 136 /* Do not discard the swap header page! */ 137 se = &si->first_swap_extent; 138 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9); 139 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9); 140 if (nr_blocks) { 141 err = blkdev_issue_discard(si->bdev, start_block, 142 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER); 143 if (err) 144 return err; 145 cond_resched(); 146 } 147 148 list_for_each_entry(se, &si->first_swap_extent.list, list) { 149 start_block = se->start_block << (PAGE_SHIFT - 9); 150 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9); 151 152 err = blkdev_issue_discard(si->bdev, start_block, 153 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER); 154 if (err) 155 break; 156 157 cond_resched(); 158 } 159 return err; /* That will often be -EOPNOTSUPP */ 160 } 161 162 /* 163 * swap allocation tell device that a cluster of swap can now be discarded, 164 * to allow the swap device to optimize its wear-levelling. 165 */ 166 static void discard_swap_cluster(struct swap_info_struct *si, 167 pgoff_t start_page, pgoff_t nr_pages) 168 { 169 struct swap_extent *se = si->curr_swap_extent; 170 int found_extent = 0; 171 172 while (nr_pages) { 173 struct list_head *lh; 174 175 if (se->start_page <= start_page && 176 start_page < se->start_page + se->nr_pages) { 177 pgoff_t offset = start_page - se->start_page; 178 sector_t start_block = se->start_block + offset; 179 sector_t nr_blocks = se->nr_pages - offset; 180 181 if (nr_blocks > nr_pages) 182 nr_blocks = nr_pages; 183 start_page += nr_blocks; 184 nr_pages -= nr_blocks; 185 186 if (!found_extent++) 187 si->curr_swap_extent = se; 188 189 start_block <<= PAGE_SHIFT - 9; 190 nr_blocks <<= PAGE_SHIFT - 9; 191 if (blkdev_issue_discard(si->bdev, start_block, 192 nr_blocks, GFP_NOIO, DISCARD_FL_BARRIER)) 193 break; 194 } 195 196 lh = se->list.next; 197 se = list_entry(lh, struct swap_extent, list); 198 } 199 } 200 201 static int wait_for_discard(void *word) 202 { 203 schedule(); 204 return 0; 205 } 206 207 #define SWAPFILE_CLUSTER 256 208 #define LATENCY_LIMIT 256 209 210 static inline unsigned long scan_swap_map(struct swap_info_struct *si, 211 unsigned char usage) 212 { 213 unsigned long offset; 214 unsigned long scan_base; 215 unsigned long last_in_cluster = 0; 216 int latency_ration = LATENCY_LIMIT; 217 int found_free_cluster = 0; 218 219 /* 220 * We try to cluster swap pages by allocating them sequentially 221 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this 222 * way, however, we resort to first-free allocation, starting 223 * a new cluster. This prevents us from scattering swap pages 224 * all over the entire swap partition, so that we reduce 225 * overall disk seek times between swap pages. -- sct 226 * But we do now try to find an empty cluster. -Andrea 227 * And we let swap pages go all over an SSD partition. Hugh 228 */ 229 230 si->flags += SWP_SCANNING; 231 scan_base = offset = si->cluster_next; 232 233 if (unlikely(!si->cluster_nr--)) { 234 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) { 235 si->cluster_nr = SWAPFILE_CLUSTER - 1; 236 goto checks; 237 } 238 if (si->flags & SWP_DISCARDABLE) { 239 /* 240 * Start range check on racing allocations, in case 241 * they overlap the cluster we eventually decide on 242 * (we scan without swap_lock to allow preemption). 243 * It's hardly conceivable that cluster_nr could be 244 * wrapped during our scan, but don't depend on it. 245 */ 246 if (si->lowest_alloc) 247 goto checks; 248 si->lowest_alloc = si->max; 249 si->highest_alloc = 0; 250 } 251 spin_unlock(&swap_lock); 252 253 /* 254 * If seek is expensive, start searching for new cluster from 255 * start of partition, to minimize the span of allocated swap. 256 * But if seek is cheap, search from our current position, so 257 * that swap is allocated from all over the partition: if the 258 * Flash Translation Layer only remaps within limited zones, 259 * we don't want to wear out the first zone too quickly. 260 */ 261 if (!(si->flags & SWP_SOLIDSTATE)) 262 scan_base = offset = si->lowest_bit; 263 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 264 265 /* Locate the first empty (unaligned) cluster */ 266 for (; last_in_cluster <= si->highest_bit; offset++) { 267 if (si->swap_map[offset]) 268 last_in_cluster = offset + SWAPFILE_CLUSTER; 269 else if (offset == last_in_cluster) { 270 spin_lock(&swap_lock); 271 offset -= SWAPFILE_CLUSTER - 1; 272 si->cluster_next = offset; 273 si->cluster_nr = SWAPFILE_CLUSTER - 1; 274 found_free_cluster = 1; 275 goto checks; 276 } 277 if (unlikely(--latency_ration < 0)) { 278 cond_resched(); 279 latency_ration = LATENCY_LIMIT; 280 } 281 } 282 283 offset = si->lowest_bit; 284 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 285 286 /* Locate the first empty (unaligned) cluster */ 287 for (; last_in_cluster < scan_base; offset++) { 288 if (si->swap_map[offset]) 289 last_in_cluster = offset + SWAPFILE_CLUSTER; 290 else if (offset == last_in_cluster) { 291 spin_lock(&swap_lock); 292 offset -= SWAPFILE_CLUSTER - 1; 293 si->cluster_next = offset; 294 si->cluster_nr = SWAPFILE_CLUSTER - 1; 295 found_free_cluster = 1; 296 goto checks; 297 } 298 if (unlikely(--latency_ration < 0)) { 299 cond_resched(); 300 latency_ration = LATENCY_LIMIT; 301 } 302 } 303 304 offset = scan_base; 305 spin_lock(&swap_lock); 306 si->cluster_nr = SWAPFILE_CLUSTER - 1; 307 si->lowest_alloc = 0; 308 } 309 310 checks: 311 if (!(si->flags & SWP_WRITEOK)) 312 goto no_page; 313 if (!si->highest_bit) 314 goto no_page; 315 if (offset > si->highest_bit) 316 scan_base = offset = si->lowest_bit; 317 318 /* reuse swap entry of cache-only swap if not busy. */ 319 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 320 int swap_was_freed; 321 spin_unlock(&swap_lock); 322 swap_was_freed = __try_to_reclaim_swap(si, offset); 323 spin_lock(&swap_lock); 324 /* entry was freed successfully, try to use this again */ 325 if (swap_was_freed) 326 goto checks; 327 goto scan; /* check next one */ 328 } 329 330 if (si->swap_map[offset]) 331 goto scan; 332 333 if (offset == si->lowest_bit) 334 si->lowest_bit++; 335 if (offset == si->highest_bit) 336 si->highest_bit--; 337 si->inuse_pages++; 338 if (si->inuse_pages == si->pages) { 339 si->lowest_bit = si->max; 340 si->highest_bit = 0; 341 } 342 si->swap_map[offset] = usage; 343 si->cluster_next = offset + 1; 344 si->flags -= SWP_SCANNING; 345 346 if (si->lowest_alloc) { 347 /* 348 * Only set when SWP_DISCARDABLE, and there's a scan 349 * for a free cluster in progress or just completed. 350 */ 351 if (found_free_cluster) { 352 /* 353 * To optimize wear-levelling, discard the 354 * old data of the cluster, taking care not to 355 * discard any of its pages that have already 356 * been allocated by racing tasks (offset has 357 * already stepped over any at the beginning). 358 */ 359 if (offset < si->highest_alloc && 360 si->lowest_alloc <= last_in_cluster) 361 last_in_cluster = si->lowest_alloc - 1; 362 si->flags |= SWP_DISCARDING; 363 spin_unlock(&swap_lock); 364 365 if (offset < last_in_cluster) 366 discard_swap_cluster(si, offset, 367 last_in_cluster - offset + 1); 368 369 spin_lock(&swap_lock); 370 si->lowest_alloc = 0; 371 si->flags &= ~SWP_DISCARDING; 372 373 smp_mb(); /* wake_up_bit advises this */ 374 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING)); 375 376 } else if (si->flags & SWP_DISCARDING) { 377 /* 378 * Delay using pages allocated by racing tasks 379 * until the whole discard has been issued. We 380 * could defer that delay until swap_writepage, 381 * but it's easier to keep this self-contained. 382 */ 383 spin_unlock(&swap_lock); 384 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING), 385 wait_for_discard, TASK_UNINTERRUPTIBLE); 386 spin_lock(&swap_lock); 387 } else { 388 /* 389 * Note pages allocated by racing tasks while 390 * scan for a free cluster is in progress, so 391 * that its final discard can exclude them. 392 */ 393 if (offset < si->lowest_alloc) 394 si->lowest_alloc = offset; 395 if (offset > si->highest_alloc) 396 si->highest_alloc = offset; 397 } 398 } 399 return offset; 400 401 scan: 402 spin_unlock(&swap_lock); 403 while (++offset <= si->highest_bit) { 404 if (!si->swap_map[offset]) { 405 spin_lock(&swap_lock); 406 goto checks; 407 } 408 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 409 spin_lock(&swap_lock); 410 goto checks; 411 } 412 if (unlikely(--latency_ration < 0)) { 413 cond_resched(); 414 latency_ration = LATENCY_LIMIT; 415 } 416 } 417 offset = si->lowest_bit; 418 while (++offset < scan_base) { 419 if (!si->swap_map[offset]) { 420 spin_lock(&swap_lock); 421 goto checks; 422 } 423 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 424 spin_lock(&swap_lock); 425 goto checks; 426 } 427 if (unlikely(--latency_ration < 0)) { 428 cond_resched(); 429 latency_ration = LATENCY_LIMIT; 430 } 431 } 432 spin_lock(&swap_lock); 433 434 no_page: 435 si->flags -= SWP_SCANNING; 436 return 0; 437 } 438 439 swp_entry_t get_swap_page(void) 440 { 441 struct swap_info_struct *si; 442 pgoff_t offset; 443 int type, next; 444 int wrapped = 0; 445 446 spin_lock(&swap_lock); 447 if (nr_swap_pages <= 0) 448 goto noswap; 449 nr_swap_pages--; 450 451 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { 452 si = swap_info[type]; 453 next = si->next; 454 if (next < 0 || 455 (!wrapped && si->prio != swap_info[next]->prio)) { 456 next = swap_list.head; 457 wrapped++; 458 } 459 460 if (!si->highest_bit) 461 continue; 462 if (!(si->flags & SWP_WRITEOK)) 463 continue; 464 465 swap_list.next = next; 466 /* This is called for allocating swap entry for cache */ 467 offset = scan_swap_map(si, SWAP_HAS_CACHE); 468 if (offset) { 469 spin_unlock(&swap_lock); 470 return swp_entry(type, offset); 471 } 472 next = swap_list.next; 473 } 474 475 nr_swap_pages++; 476 noswap: 477 spin_unlock(&swap_lock); 478 return (swp_entry_t) {0}; 479 } 480 481 /* The only caller of this function is now susupend routine */ 482 swp_entry_t get_swap_page_of_type(int type) 483 { 484 struct swap_info_struct *si; 485 pgoff_t offset; 486 487 spin_lock(&swap_lock); 488 si = swap_info[type]; 489 if (si && (si->flags & SWP_WRITEOK)) { 490 nr_swap_pages--; 491 /* This is called for allocating swap entry, not cache */ 492 offset = scan_swap_map(si, 1); 493 if (offset) { 494 spin_unlock(&swap_lock); 495 return swp_entry(type, offset); 496 } 497 nr_swap_pages++; 498 } 499 spin_unlock(&swap_lock); 500 return (swp_entry_t) {0}; 501 } 502 503 static struct swap_info_struct *swap_info_get(swp_entry_t entry) 504 { 505 struct swap_info_struct *p; 506 unsigned long offset, type; 507 508 if (!entry.val) 509 goto out; 510 type = swp_type(entry); 511 if (type >= nr_swapfiles) 512 goto bad_nofile; 513 p = swap_info[type]; 514 if (!(p->flags & SWP_USED)) 515 goto bad_device; 516 offset = swp_offset(entry); 517 if (offset >= p->max) 518 goto bad_offset; 519 if (!p->swap_map[offset]) 520 goto bad_free; 521 spin_lock(&swap_lock); 522 return p; 523 524 bad_free: 525 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val); 526 goto out; 527 bad_offset: 528 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val); 529 goto out; 530 bad_device: 531 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val); 532 goto out; 533 bad_nofile: 534 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val); 535 out: 536 return NULL; 537 } 538 539 static unsigned char swap_entry_free(struct swap_info_struct *p, 540 swp_entry_t entry, unsigned char usage) 541 { 542 unsigned long offset = swp_offset(entry); 543 unsigned char count; 544 unsigned char has_cache; 545 546 count = p->swap_map[offset]; 547 has_cache = count & SWAP_HAS_CACHE; 548 count &= ~SWAP_HAS_CACHE; 549 550 if (usage == SWAP_HAS_CACHE) { 551 VM_BUG_ON(!has_cache); 552 has_cache = 0; 553 } else if (count == SWAP_MAP_SHMEM) { 554 /* 555 * Or we could insist on shmem.c using a special 556 * swap_shmem_free() and free_shmem_swap_and_cache()... 557 */ 558 count = 0; 559 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { 560 if (count == COUNT_CONTINUED) { 561 if (swap_count_continued(p, offset, count)) 562 count = SWAP_MAP_MAX | COUNT_CONTINUED; 563 else 564 count = SWAP_MAP_MAX; 565 } else 566 count--; 567 } 568 569 if (!count) 570 mem_cgroup_uncharge_swap(entry); 571 572 usage = count | has_cache; 573 p->swap_map[offset] = usage; 574 575 /* free if no reference */ 576 if (!usage) { 577 if (offset < p->lowest_bit) 578 p->lowest_bit = offset; 579 if (offset > p->highest_bit) 580 p->highest_bit = offset; 581 if (swap_list.next >= 0 && 582 p->prio > swap_info[swap_list.next]->prio) 583 swap_list.next = p->type; 584 nr_swap_pages++; 585 p->inuse_pages--; 586 } 587 588 return usage; 589 } 590 591 /* 592 * Caller has made sure that the swapdevice corresponding to entry 593 * is still around or has not been recycled. 594 */ 595 void swap_free(swp_entry_t entry) 596 { 597 struct swap_info_struct *p; 598 599 p = swap_info_get(entry); 600 if (p) { 601 swap_entry_free(p, entry, 1); 602 spin_unlock(&swap_lock); 603 } 604 } 605 606 /* 607 * Called after dropping swapcache to decrease refcnt to swap entries. 608 */ 609 void swapcache_free(swp_entry_t entry, struct page *page) 610 { 611 struct swap_info_struct *p; 612 unsigned char count; 613 614 p = swap_info_get(entry); 615 if (p) { 616 count = swap_entry_free(p, entry, SWAP_HAS_CACHE); 617 if (page) 618 mem_cgroup_uncharge_swapcache(page, entry, count != 0); 619 spin_unlock(&swap_lock); 620 } 621 } 622 623 /* 624 * How many references to page are currently swapped out? 625 * This does not give an exact answer when swap count is continued, 626 * but does include the high COUNT_CONTINUED flag to allow for that. 627 */ 628 static inline int page_swapcount(struct page *page) 629 { 630 int count = 0; 631 struct swap_info_struct *p; 632 swp_entry_t entry; 633 634 entry.val = page_private(page); 635 p = swap_info_get(entry); 636 if (p) { 637 count = swap_count(p->swap_map[swp_offset(entry)]); 638 spin_unlock(&swap_lock); 639 } 640 return count; 641 } 642 643 /* 644 * We can write to an anon page without COW if there are no other references 645 * to it. And as a side-effect, free up its swap: because the old content 646 * on disk will never be read, and seeking back there to write new content 647 * later would only waste time away from clustering. 648 */ 649 int reuse_swap_page(struct page *page) 650 { 651 int count; 652 653 VM_BUG_ON(!PageLocked(page)); 654 if (unlikely(PageKsm(page))) 655 return 0; 656 count = page_mapcount(page); 657 if (count <= 1 && PageSwapCache(page)) { 658 count += page_swapcount(page); 659 if (count == 1 && !PageWriteback(page)) { 660 delete_from_swap_cache(page); 661 SetPageDirty(page); 662 } 663 } 664 return count <= 1; 665 } 666 667 /* 668 * If swap is getting full, or if there are no more mappings of this page, 669 * then try_to_free_swap is called to free its swap space. 670 */ 671 int try_to_free_swap(struct page *page) 672 { 673 VM_BUG_ON(!PageLocked(page)); 674 675 if (!PageSwapCache(page)) 676 return 0; 677 if (PageWriteback(page)) 678 return 0; 679 if (page_swapcount(page)) 680 return 0; 681 682 delete_from_swap_cache(page); 683 SetPageDirty(page); 684 return 1; 685 } 686 687 /* 688 * Free the swap entry like above, but also try to 689 * free the page cache entry if it is the last user. 690 */ 691 int free_swap_and_cache(swp_entry_t entry) 692 { 693 struct swap_info_struct *p; 694 struct page *page = NULL; 695 696 if (non_swap_entry(entry)) 697 return 1; 698 699 p = swap_info_get(entry); 700 if (p) { 701 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) { 702 page = find_get_page(&swapper_space, entry.val); 703 if (page && !trylock_page(page)) { 704 page_cache_release(page); 705 page = NULL; 706 } 707 } 708 spin_unlock(&swap_lock); 709 } 710 if (page) { 711 /* 712 * Not mapped elsewhere, or swap space full? Free it! 713 * Also recheck PageSwapCache now page is locked (above). 714 */ 715 if (PageSwapCache(page) && !PageWriteback(page) && 716 (!page_mapped(page) || vm_swap_full())) { 717 delete_from_swap_cache(page); 718 SetPageDirty(page); 719 } 720 unlock_page(page); 721 page_cache_release(page); 722 } 723 return p != NULL; 724 } 725 726 #ifdef CONFIG_CGROUP_MEM_RES_CTLR 727 /** 728 * mem_cgroup_count_swap_user - count the user of a swap entry 729 * @ent: the swap entry to be checked 730 * @pagep: the pointer for the swap cache page of the entry to be stored 731 * 732 * Returns the number of the user of the swap entry. The number is valid only 733 * for swaps of anonymous pages. 734 * If the entry is found on swap cache, the page is stored to pagep with 735 * refcount of it being incremented. 736 */ 737 int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep) 738 { 739 struct page *page; 740 struct swap_info_struct *p; 741 int count = 0; 742 743 page = find_get_page(&swapper_space, ent.val); 744 if (page) 745 count += page_mapcount(page); 746 p = swap_info_get(ent); 747 if (p) { 748 count += swap_count(p->swap_map[swp_offset(ent)]); 749 spin_unlock(&swap_lock); 750 } 751 752 *pagep = page; 753 return count; 754 } 755 #endif 756 757 #ifdef CONFIG_HIBERNATION 758 /* 759 * Find the swap type that corresponds to given device (if any). 760 * 761 * @offset - number of the PAGE_SIZE-sized block of the device, starting 762 * from 0, in which the swap header is expected to be located. 763 * 764 * This is needed for the suspend to disk (aka swsusp). 765 */ 766 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p) 767 { 768 struct block_device *bdev = NULL; 769 int type; 770 771 if (device) 772 bdev = bdget(device); 773 774 spin_lock(&swap_lock); 775 for (type = 0; type < nr_swapfiles; type++) { 776 struct swap_info_struct *sis = swap_info[type]; 777 778 if (!(sis->flags & SWP_WRITEOK)) 779 continue; 780 781 if (!bdev) { 782 if (bdev_p) 783 *bdev_p = bdgrab(sis->bdev); 784 785 spin_unlock(&swap_lock); 786 return type; 787 } 788 if (bdev == sis->bdev) { 789 struct swap_extent *se = &sis->first_swap_extent; 790 791 if (se->start_block == offset) { 792 if (bdev_p) 793 *bdev_p = bdgrab(sis->bdev); 794 795 spin_unlock(&swap_lock); 796 bdput(bdev); 797 return type; 798 } 799 } 800 } 801 spin_unlock(&swap_lock); 802 if (bdev) 803 bdput(bdev); 804 805 return -ENODEV; 806 } 807 808 /* 809 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev 810 * corresponding to given index in swap_info (swap type). 811 */ 812 sector_t swapdev_block(int type, pgoff_t offset) 813 { 814 struct block_device *bdev; 815 816 if ((unsigned int)type >= nr_swapfiles) 817 return 0; 818 if (!(swap_info[type]->flags & SWP_WRITEOK)) 819 return 0; 820 return map_swap_entry(swp_entry(type, offset), &bdev); 821 } 822 823 /* 824 * Return either the total number of swap pages of given type, or the number 825 * of free pages of that type (depending on @free) 826 * 827 * This is needed for software suspend 828 */ 829 unsigned int count_swap_pages(int type, int free) 830 { 831 unsigned int n = 0; 832 833 spin_lock(&swap_lock); 834 if ((unsigned int)type < nr_swapfiles) { 835 struct swap_info_struct *sis = swap_info[type]; 836 837 if (sis->flags & SWP_WRITEOK) { 838 n = sis->pages; 839 if (free) 840 n -= sis->inuse_pages; 841 } 842 } 843 spin_unlock(&swap_lock); 844 return n; 845 } 846 #endif /* CONFIG_HIBERNATION */ 847 848 /* 849 * No need to decide whether this PTE shares the swap entry with others, 850 * just let do_wp_page work it out if a write is requested later - to 851 * force COW, vm_page_prot omits write permission from any private vma. 852 */ 853 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, 854 unsigned long addr, swp_entry_t entry, struct page *page) 855 { 856 struct mem_cgroup *ptr = NULL; 857 spinlock_t *ptl; 858 pte_t *pte; 859 int ret = 1; 860 861 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) { 862 ret = -ENOMEM; 863 goto out_nolock; 864 } 865 866 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 867 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) { 868 if (ret > 0) 869 mem_cgroup_cancel_charge_swapin(ptr); 870 ret = 0; 871 goto out; 872 } 873 874 dec_mm_counter(vma->vm_mm, MM_SWAPENTS); 875 inc_mm_counter(vma->vm_mm, MM_ANONPAGES); 876 get_page(page); 877 set_pte_at(vma->vm_mm, addr, pte, 878 pte_mkold(mk_pte(page, vma->vm_page_prot))); 879 page_add_anon_rmap(page, vma, addr); 880 mem_cgroup_commit_charge_swapin(page, ptr); 881 swap_free(entry); 882 /* 883 * Move the page to the active list so it is not 884 * immediately swapped out again after swapon. 885 */ 886 activate_page(page); 887 out: 888 pte_unmap_unlock(pte, ptl); 889 out_nolock: 890 return ret; 891 } 892 893 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 894 unsigned long addr, unsigned long end, 895 swp_entry_t entry, struct page *page) 896 { 897 pte_t swp_pte = swp_entry_to_pte(entry); 898 pte_t *pte; 899 int ret = 0; 900 901 /* 902 * We don't actually need pte lock while scanning for swp_pte: since 903 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the 904 * page table while we're scanning; though it could get zapped, and on 905 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse 906 * of unmatched parts which look like swp_pte, so unuse_pte must 907 * recheck under pte lock. Scanning without pte lock lets it be 908 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE. 909 */ 910 pte = pte_offset_map(pmd, addr); 911 do { 912 /* 913 * swapoff spends a _lot_ of time in this loop! 914 * Test inline before going to call unuse_pte. 915 */ 916 if (unlikely(pte_same(*pte, swp_pte))) { 917 pte_unmap(pte); 918 ret = unuse_pte(vma, pmd, addr, entry, page); 919 if (ret) 920 goto out; 921 pte = pte_offset_map(pmd, addr); 922 } 923 } while (pte++, addr += PAGE_SIZE, addr != end); 924 pte_unmap(pte - 1); 925 out: 926 return ret; 927 } 928 929 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, 930 unsigned long addr, unsigned long end, 931 swp_entry_t entry, struct page *page) 932 { 933 pmd_t *pmd; 934 unsigned long next; 935 int ret; 936 937 pmd = pmd_offset(pud, addr); 938 do { 939 next = pmd_addr_end(addr, end); 940 if (pmd_none_or_clear_bad(pmd)) 941 continue; 942 ret = unuse_pte_range(vma, pmd, addr, next, entry, page); 943 if (ret) 944 return ret; 945 } while (pmd++, addr = next, addr != end); 946 return 0; 947 } 948 949 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd, 950 unsigned long addr, unsigned long end, 951 swp_entry_t entry, struct page *page) 952 { 953 pud_t *pud; 954 unsigned long next; 955 int ret; 956 957 pud = pud_offset(pgd, addr); 958 do { 959 next = pud_addr_end(addr, end); 960 if (pud_none_or_clear_bad(pud)) 961 continue; 962 ret = unuse_pmd_range(vma, pud, addr, next, entry, page); 963 if (ret) 964 return ret; 965 } while (pud++, addr = next, addr != end); 966 return 0; 967 } 968 969 static int unuse_vma(struct vm_area_struct *vma, 970 swp_entry_t entry, struct page *page) 971 { 972 pgd_t *pgd; 973 unsigned long addr, end, next; 974 int ret; 975 976 if (page_anon_vma(page)) { 977 addr = page_address_in_vma(page, vma); 978 if (addr == -EFAULT) 979 return 0; 980 else 981 end = addr + PAGE_SIZE; 982 } else { 983 addr = vma->vm_start; 984 end = vma->vm_end; 985 } 986 987 pgd = pgd_offset(vma->vm_mm, addr); 988 do { 989 next = pgd_addr_end(addr, end); 990 if (pgd_none_or_clear_bad(pgd)) 991 continue; 992 ret = unuse_pud_range(vma, pgd, addr, next, entry, page); 993 if (ret) 994 return ret; 995 } while (pgd++, addr = next, addr != end); 996 return 0; 997 } 998 999 static int unuse_mm(struct mm_struct *mm, 1000 swp_entry_t entry, struct page *page) 1001 { 1002 struct vm_area_struct *vma; 1003 int ret = 0; 1004 1005 if (!down_read_trylock(&mm->mmap_sem)) { 1006 /* 1007 * Activate page so shrink_inactive_list is unlikely to unmap 1008 * its ptes while lock is dropped, so swapoff can make progress. 1009 */ 1010 activate_page(page); 1011 unlock_page(page); 1012 down_read(&mm->mmap_sem); 1013 lock_page(page); 1014 } 1015 for (vma = mm->mmap; vma; vma = vma->vm_next) { 1016 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page))) 1017 break; 1018 } 1019 up_read(&mm->mmap_sem); 1020 return (ret < 0)? ret: 0; 1021 } 1022 1023 /* 1024 * Scan swap_map from current position to next entry still in use. 1025 * Recycle to start on reaching the end, returning 0 when empty. 1026 */ 1027 static unsigned int find_next_to_unuse(struct swap_info_struct *si, 1028 unsigned int prev) 1029 { 1030 unsigned int max = si->max; 1031 unsigned int i = prev; 1032 unsigned char count; 1033 1034 /* 1035 * No need for swap_lock here: we're just looking 1036 * for whether an entry is in use, not modifying it; false 1037 * hits are okay, and sys_swapoff() has already prevented new 1038 * allocations from this area (while holding swap_lock). 1039 */ 1040 for (;;) { 1041 if (++i >= max) { 1042 if (!prev) { 1043 i = 0; 1044 break; 1045 } 1046 /* 1047 * No entries in use at top of swap_map, 1048 * loop back to start and recheck there. 1049 */ 1050 max = prev + 1; 1051 prev = 0; 1052 i = 1; 1053 } 1054 count = si->swap_map[i]; 1055 if (count && swap_count(count) != SWAP_MAP_BAD) 1056 break; 1057 } 1058 return i; 1059 } 1060 1061 /* 1062 * We completely avoid races by reading each swap page in advance, 1063 * and then search for the process using it. All the necessary 1064 * page table adjustments can then be made atomically. 1065 */ 1066 static int try_to_unuse(unsigned int type) 1067 { 1068 struct swap_info_struct *si = swap_info[type]; 1069 struct mm_struct *start_mm; 1070 unsigned char *swap_map; 1071 unsigned char swcount; 1072 struct page *page; 1073 swp_entry_t entry; 1074 unsigned int i = 0; 1075 int retval = 0; 1076 1077 /* 1078 * When searching mms for an entry, a good strategy is to 1079 * start at the first mm we freed the previous entry from 1080 * (though actually we don't notice whether we or coincidence 1081 * freed the entry). Initialize this start_mm with a hold. 1082 * 1083 * A simpler strategy would be to start at the last mm we 1084 * freed the previous entry from; but that would take less 1085 * advantage of mmlist ordering, which clusters forked mms 1086 * together, child after parent. If we race with dup_mmap(), we 1087 * prefer to resolve parent before child, lest we miss entries 1088 * duplicated after we scanned child: using last mm would invert 1089 * that. 1090 */ 1091 start_mm = &init_mm; 1092 atomic_inc(&init_mm.mm_users); 1093 1094 /* 1095 * Keep on scanning until all entries have gone. Usually, 1096 * one pass through swap_map is enough, but not necessarily: 1097 * there are races when an instance of an entry might be missed. 1098 */ 1099 while ((i = find_next_to_unuse(si, i)) != 0) { 1100 if (signal_pending(current)) { 1101 retval = -EINTR; 1102 break; 1103 } 1104 1105 /* 1106 * Get a page for the entry, using the existing swap 1107 * cache page if there is one. Otherwise, get a clean 1108 * page and read the swap into it. 1109 */ 1110 swap_map = &si->swap_map[i]; 1111 entry = swp_entry(type, i); 1112 page = read_swap_cache_async(entry, 1113 GFP_HIGHUSER_MOVABLE, NULL, 0); 1114 if (!page) { 1115 /* 1116 * Either swap_duplicate() failed because entry 1117 * has been freed independently, and will not be 1118 * reused since sys_swapoff() already disabled 1119 * allocation from here, or alloc_page() failed. 1120 */ 1121 if (!*swap_map) 1122 continue; 1123 retval = -ENOMEM; 1124 break; 1125 } 1126 1127 /* 1128 * Don't hold on to start_mm if it looks like exiting. 1129 */ 1130 if (atomic_read(&start_mm->mm_users) == 1) { 1131 mmput(start_mm); 1132 start_mm = &init_mm; 1133 atomic_inc(&init_mm.mm_users); 1134 } 1135 1136 /* 1137 * Wait for and lock page. When do_swap_page races with 1138 * try_to_unuse, do_swap_page can handle the fault much 1139 * faster than try_to_unuse can locate the entry. This 1140 * apparently redundant "wait_on_page_locked" lets try_to_unuse 1141 * defer to do_swap_page in such a case - in some tests, 1142 * do_swap_page and try_to_unuse repeatedly compete. 1143 */ 1144 wait_on_page_locked(page); 1145 wait_on_page_writeback(page); 1146 lock_page(page); 1147 wait_on_page_writeback(page); 1148 1149 /* 1150 * Remove all references to entry. 1151 */ 1152 swcount = *swap_map; 1153 if (swap_count(swcount) == SWAP_MAP_SHMEM) { 1154 retval = shmem_unuse(entry, page); 1155 /* page has already been unlocked and released */ 1156 if (retval < 0) 1157 break; 1158 continue; 1159 } 1160 if (swap_count(swcount) && start_mm != &init_mm) 1161 retval = unuse_mm(start_mm, entry, page); 1162 1163 if (swap_count(*swap_map)) { 1164 int set_start_mm = (*swap_map >= swcount); 1165 struct list_head *p = &start_mm->mmlist; 1166 struct mm_struct *new_start_mm = start_mm; 1167 struct mm_struct *prev_mm = start_mm; 1168 struct mm_struct *mm; 1169 1170 atomic_inc(&new_start_mm->mm_users); 1171 atomic_inc(&prev_mm->mm_users); 1172 spin_lock(&mmlist_lock); 1173 while (swap_count(*swap_map) && !retval && 1174 (p = p->next) != &start_mm->mmlist) { 1175 mm = list_entry(p, struct mm_struct, mmlist); 1176 if (!atomic_inc_not_zero(&mm->mm_users)) 1177 continue; 1178 spin_unlock(&mmlist_lock); 1179 mmput(prev_mm); 1180 prev_mm = mm; 1181 1182 cond_resched(); 1183 1184 swcount = *swap_map; 1185 if (!swap_count(swcount)) /* any usage ? */ 1186 ; 1187 else if (mm == &init_mm) 1188 set_start_mm = 1; 1189 else 1190 retval = unuse_mm(mm, entry, page); 1191 1192 if (set_start_mm && *swap_map < swcount) { 1193 mmput(new_start_mm); 1194 atomic_inc(&mm->mm_users); 1195 new_start_mm = mm; 1196 set_start_mm = 0; 1197 } 1198 spin_lock(&mmlist_lock); 1199 } 1200 spin_unlock(&mmlist_lock); 1201 mmput(prev_mm); 1202 mmput(start_mm); 1203 start_mm = new_start_mm; 1204 } 1205 if (retval) { 1206 unlock_page(page); 1207 page_cache_release(page); 1208 break; 1209 } 1210 1211 /* 1212 * If a reference remains (rare), we would like to leave 1213 * the page in the swap cache; but try_to_unmap could 1214 * then re-duplicate the entry once we drop page lock, 1215 * so we might loop indefinitely; also, that page could 1216 * not be swapped out to other storage meanwhile. So: 1217 * delete from cache even if there's another reference, 1218 * after ensuring that the data has been saved to disk - 1219 * since if the reference remains (rarer), it will be 1220 * read from disk into another page. Splitting into two 1221 * pages would be incorrect if swap supported "shared 1222 * private" pages, but they are handled by tmpfs files. 1223 * 1224 * Given how unuse_vma() targets one particular offset 1225 * in an anon_vma, once the anon_vma has been determined, 1226 * this splitting happens to be just what is needed to 1227 * handle where KSM pages have been swapped out: re-reading 1228 * is unnecessarily slow, but we can fix that later on. 1229 */ 1230 if (swap_count(*swap_map) && 1231 PageDirty(page) && PageSwapCache(page)) { 1232 struct writeback_control wbc = { 1233 .sync_mode = WB_SYNC_NONE, 1234 }; 1235 1236 swap_writepage(page, &wbc); 1237 lock_page(page); 1238 wait_on_page_writeback(page); 1239 } 1240 1241 /* 1242 * It is conceivable that a racing task removed this page from 1243 * swap cache just before we acquired the page lock at the top, 1244 * or while we dropped it in unuse_mm(). The page might even 1245 * be back in swap cache on another swap area: that we must not 1246 * delete, since it may not have been written out to swap yet. 1247 */ 1248 if (PageSwapCache(page) && 1249 likely(page_private(page) == entry.val)) 1250 delete_from_swap_cache(page); 1251 1252 /* 1253 * So we could skip searching mms once swap count went 1254 * to 1, we did not mark any present ptes as dirty: must 1255 * mark page dirty so shrink_page_list will preserve it. 1256 */ 1257 SetPageDirty(page); 1258 unlock_page(page); 1259 page_cache_release(page); 1260 1261 /* 1262 * Make sure that we aren't completely killing 1263 * interactive performance. 1264 */ 1265 cond_resched(); 1266 } 1267 1268 mmput(start_mm); 1269 return retval; 1270 } 1271 1272 /* 1273 * After a successful try_to_unuse, if no swap is now in use, we know 1274 * we can empty the mmlist. swap_lock must be held on entry and exit. 1275 * Note that mmlist_lock nests inside swap_lock, and an mm must be 1276 * added to the mmlist just after page_duplicate - before would be racy. 1277 */ 1278 static void drain_mmlist(void) 1279 { 1280 struct list_head *p, *next; 1281 unsigned int type; 1282 1283 for (type = 0; type < nr_swapfiles; type++) 1284 if (swap_info[type]->inuse_pages) 1285 return; 1286 spin_lock(&mmlist_lock); 1287 list_for_each_safe(p, next, &init_mm.mmlist) 1288 list_del_init(p); 1289 spin_unlock(&mmlist_lock); 1290 } 1291 1292 /* 1293 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which 1294 * corresponds to page offset for the specified swap entry. 1295 * Note that the type of this function is sector_t, but it returns page offset 1296 * into the bdev, not sector offset. 1297 */ 1298 static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev) 1299 { 1300 struct swap_info_struct *sis; 1301 struct swap_extent *start_se; 1302 struct swap_extent *se; 1303 pgoff_t offset; 1304 1305 sis = swap_info[swp_type(entry)]; 1306 *bdev = sis->bdev; 1307 1308 offset = swp_offset(entry); 1309 start_se = sis->curr_swap_extent; 1310 se = start_se; 1311 1312 for ( ; ; ) { 1313 struct list_head *lh; 1314 1315 if (se->start_page <= offset && 1316 offset < (se->start_page + se->nr_pages)) { 1317 return se->start_block + (offset - se->start_page); 1318 } 1319 lh = se->list.next; 1320 se = list_entry(lh, struct swap_extent, list); 1321 sis->curr_swap_extent = se; 1322 BUG_ON(se == start_se); /* It *must* be present */ 1323 } 1324 } 1325 1326 /* 1327 * Returns the page offset into bdev for the specified page's swap entry. 1328 */ 1329 sector_t map_swap_page(struct page *page, struct block_device **bdev) 1330 { 1331 swp_entry_t entry; 1332 entry.val = page_private(page); 1333 return map_swap_entry(entry, bdev); 1334 } 1335 1336 /* 1337 * Free all of a swapdev's extent information 1338 */ 1339 static void destroy_swap_extents(struct swap_info_struct *sis) 1340 { 1341 while (!list_empty(&sis->first_swap_extent.list)) { 1342 struct swap_extent *se; 1343 1344 se = list_entry(sis->first_swap_extent.list.next, 1345 struct swap_extent, list); 1346 list_del(&se->list); 1347 kfree(se); 1348 } 1349 } 1350 1351 /* 1352 * Add a block range (and the corresponding page range) into this swapdev's 1353 * extent list. The extent list is kept sorted in page order. 1354 * 1355 * This function rather assumes that it is called in ascending page order. 1356 */ 1357 static int 1358 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, 1359 unsigned long nr_pages, sector_t start_block) 1360 { 1361 struct swap_extent *se; 1362 struct swap_extent *new_se; 1363 struct list_head *lh; 1364 1365 if (start_page == 0) { 1366 se = &sis->first_swap_extent; 1367 sis->curr_swap_extent = se; 1368 se->start_page = 0; 1369 se->nr_pages = nr_pages; 1370 se->start_block = start_block; 1371 return 1; 1372 } else { 1373 lh = sis->first_swap_extent.list.prev; /* Highest extent */ 1374 se = list_entry(lh, struct swap_extent, list); 1375 BUG_ON(se->start_page + se->nr_pages != start_page); 1376 if (se->start_block + se->nr_pages == start_block) { 1377 /* Merge it */ 1378 se->nr_pages += nr_pages; 1379 return 0; 1380 } 1381 } 1382 1383 /* 1384 * No merge. Insert a new extent, preserving ordering. 1385 */ 1386 new_se = kmalloc(sizeof(*se), GFP_KERNEL); 1387 if (new_se == NULL) 1388 return -ENOMEM; 1389 new_se->start_page = start_page; 1390 new_se->nr_pages = nr_pages; 1391 new_se->start_block = start_block; 1392 1393 list_add_tail(&new_se->list, &sis->first_swap_extent.list); 1394 return 1; 1395 } 1396 1397 /* 1398 * A `swap extent' is a simple thing which maps a contiguous range of pages 1399 * onto a contiguous range of disk blocks. An ordered list of swap extents 1400 * is built at swapon time and is then used at swap_writepage/swap_readpage 1401 * time for locating where on disk a page belongs. 1402 * 1403 * If the swapfile is an S_ISBLK block device, a single extent is installed. 1404 * This is done so that the main operating code can treat S_ISBLK and S_ISREG 1405 * swap files identically. 1406 * 1407 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap 1408 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK 1409 * swapfiles are handled *identically* after swapon time. 1410 * 1411 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks 1412 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If 1413 * some stray blocks are found which do not fall within the PAGE_SIZE alignment 1414 * requirements, they are simply tossed out - we will never use those blocks 1415 * for swapping. 1416 * 1417 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This 1418 * prevents root from shooting her foot off by ftruncating an in-use swapfile, 1419 * which will scribble on the fs. 1420 * 1421 * The amount of disk space which a single swap extent represents varies. 1422 * Typically it is in the 1-4 megabyte range. So we can have hundreds of 1423 * extents in the list. To avoid much list walking, we cache the previous 1424 * search location in `curr_swap_extent', and start new searches from there. 1425 * This is extremely effective. The average number of iterations in 1426 * map_swap_page() has been measured at about 0.3 per page. - akpm. 1427 */ 1428 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) 1429 { 1430 struct inode *inode; 1431 unsigned blocks_per_page; 1432 unsigned long page_no; 1433 unsigned blkbits; 1434 sector_t probe_block; 1435 sector_t last_block; 1436 sector_t lowest_block = -1; 1437 sector_t highest_block = 0; 1438 int nr_extents = 0; 1439 int ret; 1440 1441 inode = sis->swap_file->f_mapping->host; 1442 if (S_ISBLK(inode->i_mode)) { 1443 ret = add_swap_extent(sis, 0, sis->max, 0); 1444 *span = sis->pages; 1445 goto out; 1446 } 1447 1448 blkbits = inode->i_blkbits; 1449 blocks_per_page = PAGE_SIZE >> blkbits; 1450 1451 /* 1452 * Map all the blocks into the extent list. This code doesn't try 1453 * to be very smart. 1454 */ 1455 probe_block = 0; 1456 page_no = 0; 1457 last_block = i_size_read(inode) >> blkbits; 1458 while ((probe_block + blocks_per_page) <= last_block && 1459 page_no < sis->max) { 1460 unsigned block_in_page; 1461 sector_t first_block; 1462 1463 first_block = bmap(inode, probe_block); 1464 if (first_block == 0) 1465 goto bad_bmap; 1466 1467 /* 1468 * It must be PAGE_SIZE aligned on-disk 1469 */ 1470 if (first_block & (blocks_per_page - 1)) { 1471 probe_block++; 1472 goto reprobe; 1473 } 1474 1475 for (block_in_page = 1; block_in_page < blocks_per_page; 1476 block_in_page++) { 1477 sector_t block; 1478 1479 block = bmap(inode, probe_block + block_in_page); 1480 if (block == 0) 1481 goto bad_bmap; 1482 if (block != first_block + block_in_page) { 1483 /* Discontiguity */ 1484 probe_block++; 1485 goto reprobe; 1486 } 1487 } 1488 1489 first_block >>= (PAGE_SHIFT - blkbits); 1490 if (page_no) { /* exclude the header page */ 1491 if (first_block < lowest_block) 1492 lowest_block = first_block; 1493 if (first_block > highest_block) 1494 highest_block = first_block; 1495 } 1496 1497 /* 1498 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 1499 */ 1500 ret = add_swap_extent(sis, page_no, 1, first_block); 1501 if (ret < 0) 1502 goto out; 1503 nr_extents += ret; 1504 page_no++; 1505 probe_block += blocks_per_page; 1506 reprobe: 1507 continue; 1508 } 1509 ret = nr_extents; 1510 *span = 1 + highest_block - lowest_block; 1511 if (page_no == 0) 1512 page_no = 1; /* force Empty message */ 1513 sis->max = page_no; 1514 sis->pages = page_no - 1; 1515 sis->highest_bit = page_no - 1; 1516 out: 1517 return ret; 1518 bad_bmap: 1519 printk(KERN_ERR "swapon: swapfile has holes\n"); 1520 ret = -EINVAL; 1521 goto out; 1522 } 1523 1524 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) 1525 { 1526 struct swap_info_struct *p = NULL; 1527 unsigned char *swap_map; 1528 struct file *swap_file, *victim; 1529 struct address_space *mapping; 1530 struct inode *inode; 1531 char *pathname; 1532 int i, type, prev; 1533 int err; 1534 1535 if (!capable(CAP_SYS_ADMIN)) 1536 return -EPERM; 1537 1538 pathname = getname(specialfile); 1539 err = PTR_ERR(pathname); 1540 if (IS_ERR(pathname)) 1541 goto out; 1542 1543 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0); 1544 putname(pathname); 1545 err = PTR_ERR(victim); 1546 if (IS_ERR(victim)) 1547 goto out; 1548 1549 mapping = victim->f_mapping; 1550 prev = -1; 1551 spin_lock(&swap_lock); 1552 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) { 1553 p = swap_info[type]; 1554 if (p->flags & SWP_WRITEOK) { 1555 if (p->swap_file->f_mapping == mapping) 1556 break; 1557 } 1558 prev = type; 1559 } 1560 if (type < 0) { 1561 err = -EINVAL; 1562 spin_unlock(&swap_lock); 1563 goto out_dput; 1564 } 1565 if (!security_vm_enough_memory(p->pages)) 1566 vm_unacct_memory(p->pages); 1567 else { 1568 err = -ENOMEM; 1569 spin_unlock(&swap_lock); 1570 goto out_dput; 1571 } 1572 if (prev < 0) 1573 swap_list.head = p->next; 1574 else 1575 swap_info[prev]->next = p->next; 1576 if (type == swap_list.next) { 1577 /* just pick something that's safe... */ 1578 swap_list.next = swap_list.head; 1579 } 1580 if (p->prio < 0) { 1581 for (i = p->next; i >= 0; i = swap_info[i]->next) 1582 swap_info[i]->prio = p->prio--; 1583 least_priority++; 1584 } 1585 nr_swap_pages -= p->pages; 1586 total_swap_pages -= p->pages; 1587 p->flags &= ~SWP_WRITEOK; 1588 spin_unlock(&swap_lock); 1589 1590 current->flags |= PF_OOM_ORIGIN; 1591 err = try_to_unuse(type); 1592 current->flags &= ~PF_OOM_ORIGIN; 1593 1594 if (err) { 1595 /* re-insert swap space back into swap_list */ 1596 spin_lock(&swap_lock); 1597 if (p->prio < 0) 1598 p->prio = --least_priority; 1599 prev = -1; 1600 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { 1601 if (p->prio >= swap_info[i]->prio) 1602 break; 1603 prev = i; 1604 } 1605 p->next = i; 1606 if (prev < 0) 1607 swap_list.head = swap_list.next = type; 1608 else 1609 swap_info[prev]->next = type; 1610 nr_swap_pages += p->pages; 1611 total_swap_pages += p->pages; 1612 p->flags |= SWP_WRITEOK; 1613 spin_unlock(&swap_lock); 1614 goto out_dput; 1615 } 1616 1617 /* wait for any unplug function to finish */ 1618 down_write(&swap_unplug_sem); 1619 up_write(&swap_unplug_sem); 1620 1621 destroy_swap_extents(p); 1622 if (p->flags & SWP_CONTINUED) 1623 free_swap_count_continuations(p); 1624 1625 mutex_lock(&swapon_mutex); 1626 spin_lock(&swap_lock); 1627 drain_mmlist(); 1628 1629 /* wait for anyone still in scan_swap_map */ 1630 p->highest_bit = 0; /* cuts scans short */ 1631 while (p->flags >= SWP_SCANNING) { 1632 spin_unlock(&swap_lock); 1633 schedule_timeout_uninterruptible(1); 1634 spin_lock(&swap_lock); 1635 } 1636 1637 swap_file = p->swap_file; 1638 p->swap_file = NULL; 1639 p->max = 0; 1640 swap_map = p->swap_map; 1641 p->swap_map = NULL; 1642 p->flags = 0; 1643 spin_unlock(&swap_lock); 1644 mutex_unlock(&swapon_mutex); 1645 vfree(swap_map); 1646 /* Destroy swap account informatin */ 1647 swap_cgroup_swapoff(type); 1648 1649 inode = mapping->host; 1650 if (S_ISBLK(inode->i_mode)) { 1651 struct block_device *bdev = I_BDEV(inode); 1652 set_blocksize(bdev, p->old_block_size); 1653 bd_release(bdev); 1654 } else { 1655 mutex_lock(&inode->i_mutex); 1656 inode->i_flags &= ~S_SWAPFILE; 1657 mutex_unlock(&inode->i_mutex); 1658 } 1659 filp_close(swap_file, NULL); 1660 err = 0; 1661 1662 out_dput: 1663 filp_close(victim, NULL); 1664 out: 1665 return err; 1666 } 1667 1668 #ifdef CONFIG_PROC_FS 1669 /* iterator */ 1670 static void *swap_start(struct seq_file *swap, loff_t *pos) 1671 { 1672 struct swap_info_struct *si; 1673 int type; 1674 loff_t l = *pos; 1675 1676 mutex_lock(&swapon_mutex); 1677 1678 if (!l) 1679 return SEQ_START_TOKEN; 1680 1681 for (type = 0; type < nr_swapfiles; type++) { 1682 smp_rmb(); /* read nr_swapfiles before swap_info[type] */ 1683 si = swap_info[type]; 1684 if (!(si->flags & SWP_USED) || !si->swap_map) 1685 continue; 1686 if (!--l) 1687 return si; 1688 } 1689 1690 return NULL; 1691 } 1692 1693 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) 1694 { 1695 struct swap_info_struct *si = v; 1696 int type; 1697 1698 if (v == SEQ_START_TOKEN) 1699 type = 0; 1700 else 1701 type = si->type + 1; 1702 1703 for (; type < nr_swapfiles; type++) { 1704 smp_rmb(); /* read nr_swapfiles before swap_info[type] */ 1705 si = swap_info[type]; 1706 if (!(si->flags & SWP_USED) || !si->swap_map) 1707 continue; 1708 ++*pos; 1709 return si; 1710 } 1711 1712 return NULL; 1713 } 1714 1715 static void swap_stop(struct seq_file *swap, void *v) 1716 { 1717 mutex_unlock(&swapon_mutex); 1718 } 1719 1720 static int swap_show(struct seq_file *swap, void *v) 1721 { 1722 struct swap_info_struct *si = v; 1723 struct file *file; 1724 int len; 1725 1726 if (si == SEQ_START_TOKEN) { 1727 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); 1728 return 0; 1729 } 1730 1731 file = si->swap_file; 1732 len = seq_path(swap, &file->f_path, " \t\n\\"); 1733 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n", 1734 len < 40 ? 40 - len : 1, " ", 1735 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ? 1736 "partition" : "file\t", 1737 si->pages << (PAGE_SHIFT - 10), 1738 si->inuse_pages << (PAGE_SHIFT - 10), 1739 si->prio); 1740 return 0; 1741 } 1742 1743 static const struct seq_operations swaps_op = { 1744 .start = swap_start, 1745 .next = swap_next, 1746 .stop = swap_stop, 1747 .show = swap_show 1748 }; 1749 1750 static int swaps_open(struct inode *inode, struct file *file) 1751 { 1752 return seq_open(file, &swaps_op); 1753 } 1754 1755 static const struct file_operations proc_swaps_operations = { 1756 .open = swaps_open, 1757 .read = seq_read, 1758 .llseek = seq_lseek, 1759 .release = seq_release, 1760 }; 1761 1762 static int __init procswaps_init(void) 1763 { 1764 proc_create("swaps", 0, NULL, &proc_swaps_operations); 1765 return 0; 1766 } 1767 __initcall(procswaps_init); 1768 #endif /* CONFIG_PROC_FS */ 1769 1770 #ifdef MAX_SWAPFILES_CHECK 1771 static int __init max_swapfiles_check(void) 1772 { 1773 MAX_SWAPFILES_CHECK(); 1774 return 0; 1775 } 1776 late_initcall(max_swapfiles_check); 1777 #endif 1778 1779 /* 1780 * Written 01/25/92 by Simmule Turner, heavily changed by Linus. 1781 * 1782 * The swapon system call 1783 */ 1784 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 1785 { 1786 struct swap_info_struct *p; 1787 char *name = NULL; 1788 struct block_device *bdev = NULL; 1789 struct file *swap_file = NULL; 1790 struct address_space *mapping; 1791 unsigned int type; 1792 int i, prev; 1793 int error; 1794 union swap_header *swap_header; 1795 unsigned int nr_good_pages; 1796 int nr_extents = 0; 1797 sector_t span; 1798 unsigned long maxpages; 1799 unsigned long swapfilepages; 1800 unsigned char *swap_map = NULL; 1801 struct page *page = NULL; 1802 struct inode *inode = NULL; 1803 int did_down = 0; 1804 1805 if (!capable(CAP_SYS_ADMIN)) 1806 return -EPERM; 1807 1808 p = kzalloc(sizeof(*p), GFP_KERNEL); 1809 if (!p) 1810 return -ENOMEM; 1811 1812 spin_lock(&swap_lock); 1813 for (type = 0; type < nr_swapfiles; type++) { 1814 if (!(swap_info[type]->flags & SWP_USED)) 1815 break; 1816 } 1817 error = -EPERM; 1818 if (type >= MAX_SWAPFILES) { 1819 spin_unlock(&swap_lock); 1820 kfree(p); 1821 goto out; 1822 } 1823 if (type >= nr_swapfiles) { 1824 p->type = type; 1825 swap_info[type] = p; 1826 /* 1827 * Write swap_info[type] before nr_swapfiles, in case a 1828 * racing procfs swap_start() or swap_next() is reading them. 1829 * (We never shrink nr_swapfiles, we never free this entry.) 1830 */ 1831 smp_wmb(); 1832 nr_swapfiles++; 1833 } else { 1834 kfree(p); 1835 p = swap_info[type]; 1836 /* 1837 * Do not memset this entry: a racing procfs swap_next() 1838 * would be relying on p->type to remain valid. 1839 */ 1840 } 1841 INIT_LIST_HEAD(&p->first_swap_extent.list); 1842 p->flags = SWP_USED; 1843 p->next = -1; 1844 spin_unlock(&swap_lock); 1845 1846 name = getname(specialfile); 1847 error = PTR_ERR(name); 1848 if (IS_ERR(name)) { 1849 name = NULL; 1850 goto bad_swap_2; 1851 } 1852 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0); 1853 error = PTR_ERR(swap_file); 1854 if (IS_ERR(swap_file)) { 1855 swap_file = NULL; 1856 goto bad_swap_2; 1857 } 1858 1859 p->swap_file = swap_file; 1860 mapping = swap_file->f_mapping; 1861 inode = mapping->host; 1862 1863 error = -EBUSY; 1864 for (i = 0; i < nr_swapfiles; i++) { 1865 struct swap_info_struct *q = swap_info[i]; 1866 1867 if (i == type || !q->swap_file) 1868 continue; 1869 if (mapping == q->swap_file->f_mapping) 1870 goto bad_swap; 1871 } 1872 1873 error = -EINVAL; 1874 if (S_ISBLK(inode->i_mode)) { 1875 bdev = I_BDEV(inode); 1876 error = bd_claim(bdev, sys_swapon); 1877 if (error < 0) { 1878 bdev = NULL; 1879 error = -EINVAL; 1880 goto bad_swap; 1881 } 1882 p->old_block_size = block_size(bdev); 1883 error = set_blocksize(bdev, PAGE_SIZE); 1884 if (error < 0) 1885 goto bad_swap; 1886 p->bdev = bdev; 1887 } else if (S_ISREG(inode->i_mode)) { 1888 p->bdev = inode->i_sb->s_bdev; 1889 mutex_lock(&inode->i_mutex); 1890 did_down = 1; 1891 if (IS_SWAPFILE(inode)) { 1892 error = -EBUSY; 1893 goto bad_swap; 1894 } 1895 } else { 1896 goto bad_swap; 1897 } 1898 1899 swapfilepages = i_size_read(inode) >> PAGE_SHIFT; 1900 1901 /* 1902 * Read the swap header. 1903 */ 1904 if (!mapping->a_ops->readpage) { 1905 error = -EINVAL; 1906 goto bad_swap; 1907 } 1908 page = read_mapping_page(mapping, 0, swap_file); 1909 if (IS_ERR(page)) { 1910 error = PTR_ERR(page); 1911 goto bad_swap; 1912 } 1913 swap_header = kmap(page); 1914 1915 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { 1916 printk(KERN_ERR "Unable to find swap-space signature\n"); 1917 error = -EINVAL; 1918 goto bad_swap; 1919 } 1920 1921 /* swap partition endianess hack... */ 1922 if (swab32(swap_header->info.version) == 1) { 1923 swab32s(&swap_header->info.version); 1924 swab32s(&swap_header->info.last_page); 1925 swab32s(&swap_header->info.nr_badpages); 1926 for (i = 0; i < swap_header->info.nr_badpages; i++) 1927 swab32s(&swap_header->info.badpages[i]); 1928 } 1929 /* Check the swap header's sub-version */ 1930 if (swap_header->info.version != 1) { 1931 printk(KERN_WARNING 1932 "Unable to handle swap header version %d\n", 1933 swap_header->info.version); 1934 error = -EINVAL; 1935 goto bad_swap; 1936 } 1937 1938 p->lowest_bit = 1; 1939 p->cluster_next = 1; 1940 p->cluster_nr = 0; 1941 1942 /* 1943 * Find out how many pages are allowed for a single swap 1944 * device. There are two limiting factors: 1) the number of 1945 * bits for the swap offset in the swp_entry_t type and 1946 * 2) the number of bits in the a swap pte as defined by 1947 * the different architectures. In order to find the 1948 * largest possible bit mask a swap entry with swap type 0 1949 * and swap offset ~0UL is created, encoded to a swap pte, 1950 * decoded to a swp_entry_t again and finally the swap 1951 * offset is extracted. This will mask all the bits from 1952 * the initial ~0UL mask that can't be encoded in either 1953 * the swp_entry_t or the architecture definition of a 1954 * swap pte. 1955 */ 1956 maxpages = swp_offset(pte_to_swp_entry( 1957 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; 1958 if (maxpages > swap_header->info.last_page) { 1959 maxpages = swap_header->info.last_page + 1; 1960 /* p->max is an unsigned int: don't overflow it */ 1961 if ((unsigned int)maxpages == 0) 1962 maxpages = UINT_MAX; 1963 } 1964 p->highest_bit = maxpages - 1; 1965 1966 error = -EINVAL; 1967 if (!maxpages) 1968 goto bad_swap; 1969 if (swapfilepages && maxpages > swapfilepages) { 1970 printk(KERN_WARNING 1971 "Swap area shorter than signature indicates\n"); 1972 goto bad_swap; 1973 } 1974 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) 1975 goto bad_swap; 1976 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) 1977 goto bad_swap; 1978 1979 /* OK, set up the swap map and apply the bad block list */ 1980 swap_map = vmalloc(maxpages); 1981 if (!swap_map) { 1982 error = -ENOMEM; 1983 goto bad_swap; 1984 } 1985 1986 memset(swap_map, 0, maxpages); 1987 nr_good_pages = maxpages - 1; /* omit header page */ 1988 1989 for (i = 0; i < swap_header->info.nr_badpages; i++) { 1990 unsigned int page_nr = swap_header->info.badpages[i]; 1991 if (page_nr == 0 || page_nr > swap_header->info.last_page) { 1992 error = -EINVAL; 1993 goto bad_swap; 1994 } 1995 if (page_nr < maxpages) { 1996 swap_map[page_nr] = SWAP_MAP_BAD; 1997 nr_good_pages--; 1998 } 1999 } 2000 2001 error = swap_cgroup_swapon(type, maxpages); 2002 if (error) 2003 goto bad_swap; 2004 2005 if (nr_good_pages) { 2006 swap_map[0] = SWAP_MAP_BAD; 2007 p->max = maxpages; 2008 p->pages = nr_good_pages; 2009 nr_extents = setup_swap_extents(p, &span); 2010 if (nr_extents < 0) { 2011 error = nr_extents; 2012 goto bad_swap; 2013 } 2014 nr_good_pages = p->pages; 2015 } 2016 if (!nr_good_pages) { 2017 printk(KERN_WARNING "Empty swap-file\n"); 2018 error = -EINVAL; 2019 goto bad_swap; 2020 } 2021 2022 if (p->bdev) { 2023 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { 2024 p->flags |= SWP_SOLIDSTATE; 2025 p->cluster_next = 1 + (random32() % p->highest_bit); 2026 } 2027 if (discard_swap(p) == 0) 2028 p->flags |= SWP_DISCARDABLE; 2029 } 2030 2031 mutex_lock(&swapon_mutex); 2032 spin_lock(&swap_lock); 2033 if (swap_flags & SWAP_FLAG_PREFER) 2034 p->prio = 2035 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; 2036 else 2037 p->prio = --least_priority; 2038 p->swap_map = swap_map; 2039 p->flags |= SWP_WRITEOK; 2040 nr_swap_pages += nr_good_pages; 2041 total_swap_pages += nr_good_pages; 2042 2043 printk(KERN_INFO "Adding %uk swap on %s. " 2044 "Priority:%d extents:%d across:%lluk %s%s\n", 2045 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio, 2046 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10), 2047 (p->flags & SWP_SOLIDSTATE) ? "SS" : "", 2048 (p->flags & SWP_DISCARDABLE) ? "D" : ""); 2049 2050 /* insert swap space into swap_list: */ 2051 prev = -1; 2052 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { 2053 if (p->prio >= swap_info[i]->prio) 2054 break; 2055 prev = i; 2056 } 2057 p->next = i; 2058 if (prev < 0) 2059 swap_list.head = swap_list.next = type; 2060 else 2061 swap_info[prev]->next = type; 2062 spin_unlock(&swap_lock); 2063 mutex_unlock(&swapon_mutex); 2064 error = 0; 2065 goto out; 2066 bad_swap: 2067 if (bdev) { 2068 set_blocksize(bdev, p->old_block_size); 2069 bd_release(bdev); 2070 } 2071 destroy_swap_extents(p); 2072 swap_cgroup_swapoff(type); 2073 bad_swap_2: 2074 spin_lock(&swap_lock); 2075 p->swap_file = NULL; 2076 p->flags = 0; 2077 spin_unlock(&swap_lock); 2078 vfree(swap_map); 2079 if (swap_file) 2080 filp_close(swap_file, NULL); 2081 out: 2082 if (page && !IS_ERR(page)) { 2083 kunmap(page); 2084 page_cache_release(page); 2085 } 2086 if (name) 2087 putname(name); 2088 if (did_down) { 2089 if (!error) 2090 inode->i_flags |= S_SWAPFILE; 2091 mutex_unlock(&inode->i_mutex); 2092 } 2093 return error; 2094 } 2095 2096 void si_swapinfo(struct sysinfo *val) 2097 { 2098 unsigned int type; 2099 unsigned long nr_to_be_unused = 0; 2100 2101 spin_lock(&swap_lock); 2102 for (type = 0; type < nr_swapfiles; type++) { 2103 struct swap_info_struct *si = swap_info[type]; 2104 2105 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) 2106 nr_to_be_unused += si->inuse_pages; 2107 } 2108 val->freeswap = nr_swap_pages + nr_to_be_unused; 2109 val->totalswap = total_swap_pages + nr_to_be_unused; 2110 spin_unlock(&swap_lock); 2111 } 2112 2113 /* 2114 * Verify that a swap entry is valid and increment its swap map count. 2115 * 2116 * Returns error code in following case. 2117 * - success -> 0 2118 * - swp_entry is invalid -> EINVAL 2119 * - swp_entry is migration entry -> EINVAL 2120 * - swap-cache reference is requested but there is already one. -> EEXIST 2121 * - swap-cache reference is requested but the entry is not used. -> ENOENT 2122 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM 2123 */ 2124 static int __swap_duplicate(swp_entry_t entry, unsigned char usage) 2125 { 2126 struct swap_info_struct *p; 2127 unsigned long offset, type; 2128 unsigned char count; 2129 unsigned char has_cache; 2130 int err = -EINVAL; 2131 2132 if (non_swap_entry(entry)) 2133 goto out; 2134 2135 type = swp_type(entry); 2136 if (type >= nr_swapfiles) 2137 goto bad_file; 2138 p = swap_info[type]; 2139 offset = swp_offset(entry); 2140 2141 spin_lock(&swap_lock); 2142 if (unlikely(offset >= p->max)) 2143 goto unlock_out; 2144 2145 count = p->swap_map[offset]; 2146 has_cache = count & SWAP_HAS_CACHE; 2147 count &= ~SWAP_HAS_CACHE; 2148 err = 0; 2149 2150 if (usage == SWAP_HAS_CACHE) { 2151 2152 /* set SWAP_HAS_CACHE if there is no cache and entry is used */ 2153 if (!has_cache && count) 2154 has_cache = SWAP_HAS_CACHE; 2155 else if (has_cache) /* someone else added cache */ 2156 err = -EEXIST; 2157 else /* no users remaining */ 2158 err = -ENOENT; 2159 2160 } else if (count || has_cache) { 2161 2162 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) 2163 count += usage; 2164 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) 2165 err = -EINVAL; 2166 else if (swap_count_continued(p, offset, count)) 2167 count = COUNT_CONTINUED; 2168 else 2169 err = -ENOMEM; 2170 } else 2171 err = -ENOENT; /* unused swap entry */ 2172 2173 p->swap_map[offset] = count | has_cache; 2174 2175 unlock_out: 2176 spin_unlock(&swap_lock); 2177 out: 2178 return err; 2179 2180 bad_file: 2181 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); 2182 goto out; 2183 } 2184 2185 /* 2186 * Help swapoff by noting that swap entry belongs to shmem/tmpfs 2187 * (in which case its reference count is never incremented). 2188 */ 2189 void swap_shmem_alloc(swp_entry_t entry) 2190 { 2191 __swap_duplicate(entry, SWAP_MAP_SHMEM); 2192 } 2193 2194 /* 2195 * Increase reference count of swap entry by 1. 2196 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required 2197 * but could not be atomically allocated. Returns 0, just as if it succeeded, 2198 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which 2199 * might occur if a page table entry has got corrupted. 2200 */ 2201 int swap_duplicate(swp_entry_t entry) 2202 { 2203 int err = 0; 2204 2205 while (!err && __swap_duplicate(entry, 1) == -ENOMEM) 2206 err = add_swap_count_continuation(entry, GFP_ATOMIC); 2207 return err; 2208 } 2209 2210 /* 2211 * @entry: swap entry for which we allocate swap cache. 2212 * 2213 * Called when allocating swap cache for existing swap entry, 2214 * This can return error codes. Returns 0 at success. 2215 * -EBUSY means there is a swap cache. 2216 * Note: return code is different from swap_duplicate(). 2217 */ 2218 int swapcache_prepare(swp_entry_t entry) 2219 { 2220 return __swap_duplicate(entry, SWAP_HAS_CACHE); 2221 } 2222 2223 /* 2224 * swap_lock prevents swap_map being freed. Don't grab an extra 2225 * reference on the swaphandle, it doesn't matter if it becomes unused. 2226 */ 2227 int valid_swaphandles(swp_entry_t entry, unsigned long *offset) 2228 { 2229 struct swap_info_struct *si; 2230 int our_page_cluster = page_cluster; 2231 pgoff_t target, toff; 2232 pgoff_t base, end; 2233 int nr_pages = 0; 2234 2235 if (!our_page_cluster) /* no readahead */ 2236 return 0; 2237 2238 si = swap_info[swp_type(entry)]; 2239 target = swp_offset(entry); 2240 base = (target >> our_page_cluster) << our_page_cluster; 2241 end = base + (1 << our_page_cluster); 2242 if (!base) /* first page is swap header */ 2243 base++; 2244 2245 spin_lock(&swap_lock); 2246 if (end > si->max) /* don't go beyond end of map */ 2247 end = si->max; 2248 2249 /* Count contiguous allocated slots above our target */ 2250 for (toff = target; ++toff < end; nr_pages++) { 2251 /* Don't read in free or bad pages */ 2252 if (!si->swap_map[toff]) 2253 break; 2254 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) 2255 break; 2256 } 2257 /* Count contiguous allocated slots below our target */ 2258 for (toff = target; --toff >= base; nr_pages++) { 2259 /* Don't read in free or bad pages */ 2260 if (!si->swap_map[toff]) 2261 break; 2262 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) 2263 break; 2264 } 2265 spin_unlock(&swap_lock); 2266 2267 /* 2268 * Indicate starting offset, and return number of pages to get: 2269 * if only 1, say 0, since there's then no readahead to be done. 2270 */ 2271 *offset = ++toff; 2272 return nr_pages? ++nr_pages: 0; 2273 } 2274 2275 /* 2276 * add_swap_count_continuation - called when a swap count is duplicated 2277 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's 2278 * page of the original vmalloc'ed swap_map, to hold the continuation count 2279 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called 2280 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc. 2281 * 2282 * These continuation pages are seldom referenced: the common paths all work 2283 * on the original swap_map, only referring to a continuation page when the 2284 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX. 2285 * 2286 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding 2287 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL) 2288 * can be called after dropping locks. 2289 */ 2290 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask) 2291 { 2292 struct swap_info_struct *si; 2293 struct page *head; 2294 struct page *page; 2295 struct page *list_page; 2296 pgoff_t offset; 2297 unsigned char count; 2298 2299 /* 2300 * When debugging, it's easier to use __GFP_ZERO here; but it's better 2301 * for latency not to zero a page while GFP_ATOMIC and holding locks. 2302 */ 2303 page = alloc_page(gfp_mask | __GFP_HIGHMEM); 2304 2305 si = swap_info_get(entry); 2306 if (!si) { 2307 /* 2308 * An acceptable race has occurred since the failing 2309 * __swap_duplicate(): the swap entry has been freed, 2310 * perhaps even the whole swap_map cleared for swapoff. 2311 */ 2312 goto outer; 2313 } 2314 2315 offset = swp_offset(entry); 2316 count = si->swap_map[offset] & ~SWAP_HAS_CACHE; 2317 2318 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) { 2319 /* 2320 * The higher the swap count, the more likely it is that tasks 2321 * will race to add swap count continuation: we need to avoid 2322 * over-provisioning. 2323 */ 2324 goto out; 2325 } 2326 2327 if (!page) { 2328 spin_unlock(&swap_lock); 2329 return -ENOMEM; 2330 } 2331 2332 /* 2333 * We are fortunate that although vmalloc_to_page uses pte_offset_map, 2334 * no architecture is using highmem pages for kernel pagetables: so it 2335 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps. 2336 */ 2337 head = vmalloc_to_page(si->swap_map + offset); 2338 offset &= ~PAGE_MASK; 2339 2340 /* 2341 * Page allocation does not initialize the page's lru field, 2342 * but it does always reset its private field. 2343 */ 2344 if (!page_private(head)) { 2345 BUG_ON(count & COUNT_CONTINUED); 2346 INIT_LIST_HEAD(&head->lru); 2347 set_page_private(head, SWP_CONTINUED); 2348 si->flags |= SWP_CONTINUED; 2349 } 2350 2351 list_for_each_entry(list_page, &head->lru, lru) { 2352 unsigned char *map; 2353 2354 /* 2355 * If the previous map said no continuation, but we've found 2356 * a continuation page, free our allocation and use this one. 2357 */ 2358 if (!(count & COUNT_CONTINUED)) 2359 goto out; 2360 2361 map = kmap_atomic(list_page, KM_USER0) + offset; 2362 count = *map; 2363 kunmap_atomic(map, KM_USER0); 2364 2365 /* 2366 * If this continuation count now has some space in it, 2367 * free our allocation and use this one. 2368 */ 2369 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX) 2370 goto out; 2371 } 2372 2373 list_add_tail(&page->lru, &head->lru); 2374 page = NULL; /* now it's attached, don't free it */ 2375 out: 2376 spin_unlock(&swap_lock); 2377 outer: 2378 if (page) 2379 __free_page(page); 2380 return 0; 2381 } 2382 2383 /* 2384 * swap_count_continued - when the original swap_map count is incremented 2385 * from SWAP_MAP_MAX, check if there is already a continuation page to carry 2386 * into, carry if so, or else fail until a new continuation page is allocated; 2387 * when the original swap_map count is decremented from 0 with continuation, 2388 * borrow from the continuation and report whether it still holds more. 2389 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock. 2390 */ 2391 static bool swap_count_continued(struct swap_info_struct *si, 2392 pgoff_t offset, unsigned char count) 2393 { 2394 struct page *head; 2395 struct page *page; 2396 unsigned char *map; 2397 2398 head = vmalloc_to_page(si->swap_map + offset); 2399 if (page_private(head) != SWP_CONTINUED) { 2400 BUG_ON(count & COUNT_CONTINUED); 2401 return false; /* need to add count continuation */ 2402 } 2403 2404 offset &= ~PAGE_MASK; 2405 page = list_entry(head->lru.next, struct page, lru); 2406 map = kmap_atomic(page, KM_USER0) + offset; 2407 2408 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ 2409 goto init_map; /* jump over SWAP_CONT_MAX checks */ 2410 2411 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */ 2412 /* 2413 * Think of how you add 1 to 999 2414 */ 2415 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { 2416 kunmap_atomic(map, KM_USER0); 2417 page = list_entry(page->lru.next, struct page, lru); 2418 BUG_ON(page == head); 2419 map = kmap_atomic(page, KM_USER0) + offset; 2420 } 2421 if (*map == SWAP_CONT_MAX) { 2422 kunmap_atomic(map, KM_USER0); 2423 page = list_entry(page->lru.next, struct page, lru); 2424 if (page == head) 2425 return false; /* add count continuation */ 2426 map = kmap_atomic(page, KM_USER0) + offset; 2427 init_map: *map = 0; /* we didn't zero the page */ 2428 } 2429 *map += 1; 2430 kunmap_atomic(map, KM_USER0); 2431 page = list_entry(page->lru.prev, struct page, lru); 2432 while (page != head) { 2433 map = kmap_atomic(page, KM_USER0) + offset; 2434 *map = COUNT_CONTINUED; 2435 kunmap_atomic(map, KM_USER0); 2436 page = list_entry(page->lru.prev, struct page, lru); 2437 } 2438 return true; /* incremented */ 2439 2440 } else { /* decrementing */ 2441 /* 2442 * Think of how you subtract 1 from 1000 2443 */ 2444 BUG_ON(count != COUNT_CONTINUED); 2445 while (*map == COUNT_CONTINUED) { 2446 kunmap_atomic(map, KM_USER0); 2447 page = list_entry(page->lru.next, struct page, lru); 2448 BUG_ON(page == head); 2449 map = kmap_atomic(page, KM_USER0) + offset; 2450 } 2451 BUG_ON(*map == 0); 2452 *map -= 1; 2453 if (*map == 0) 2454 count = 0; 2455 kunmap_atomic(map, KM_USER0); 2456 page = list_entry(page->lru.prev, struct page, lru); 2457 while (page != head) { 2458 map = kmap_atomic(page, KM_USER0) + offset; 2459 *map = SWAP_CONT_MAX | count; 2460 count = COUNT_CONTINUED; 2461 kunmap_atomic(map, KM_USER0); 2462 page = list_entry(page->lru.prev, struct page, lru); 2463 } 2464 return count == COUNT_CONTINUED; 2465 } 2466 } 2467 2468 /* 2469 * free_swap_count_continuations - swapoff free all the continuation pages 2470 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it. 2471 */ 2472 static void free_swap_count_continuations(struct swap_info_struct *si) 2473 { 2474 pgoff_t offset; 2475 2476 for (offset = 0; offset < si->max; offset += PAGE_SIZE) { 2477 struct page *head; 2478 head = vmalloc_to_page(si->swap_map + offset); 2479 if (page_private(head)) { 2480 struct list_head *this, *next; 2481 list_for_each_safe(this, next, &head->lru) { 2482 struct page *page; 2483 page = list_entry(this, struct page, lru); 2484 list_del(this); 2485 __free_page(page); 2486 } 2487 } 2488 } 2489 } 2490