swapfile.c revision 349f429eec36cb743fee20f4c193ecde97a3ed2e
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 39static bool swap_count_continued(struct swap_info_struct *, pgoff_t, 40 unsigned char); 41static void free_swap_count_continuations(struct swap_info_struct *); 42static sector_t map_swap_entry(swp_entry_t, struct block_device**); 43 44static DEFINE_SPINLOCK(swap_lock); 45static unsigned int nr_swapfiles; 46long nr_swap_pages; 47long total_swap_pages; 48static int least_priority; 49 50static bool swap_for_hibernation; 51 52static const char Bad_file[] = "Bad swap file entry "; 53static const char Unused_file[] = "Unused swap file entry "; 54static const char Bad_offset[] = "Bad swap offset entry "; 55static const char Unused_offset[] = "Unused swap offset entry "; 56 57static struct swap_list_t swap_list = {-1, -1}; 58 59static struct swap_info_struct *swap_info[MAX_SWAPFILES]; 60 61static DEFINE_MUTEX(swapon_mutex); 62 63static inline unsigned char swap_count(unsigned char ent) 64{ 65 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */ 66} 67 68/* returns 1 if swap entry is freed */ 69static int 70__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset) 71{ 72 swp_entry_t entry = swp_entry(si->type, offset); 73 struct page *page; 74 int ret = 0; 75 76 page = find_get_page(&swapper_space, entry.val); 77 if (!page) 78 return 0; 79 /* 80 * This function is called from scan_swap_map() and it's called 81 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here. 82 * We have to use trylock for avoiding deadlock. This is a special 83 * case and you should use try_to_free_swap() with explicit lock_page() 84 * in usual operations. 85 */ 86 if (trylock_page(page)) { 87 ret = try_to_free_swap(page); 88 unlock_page(page); 89 } 90 page_cache_release(page); 91 return ret; 92} 93 94/* 95 * We need this because the bdev->unplug_fn can sleep and we cannot 96 * hold swap_lock while calling the unplug_fn. And swap_lock 97 * cannot be turned into a mutex. 98 */ 99static DECLARE_RWSEM(swap_unplug_sem); 100 101void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page) 102{ 103 swp_entry_t entry; 104 105 down_read(&swap_unplug_sem); 106 entry.val = page_private(page); 107 if (PageSwapCache(page)) { 108 struct block_device *bdev = swap_info[swp_type(entry)]->bdev; 109 struct backing_dev_info *bdi; 110 111 /* 112 * If the page is removed from swapcache from under us (with a 113 * racy try_to_unuse/swapoff) we need an additional reference 114 * count to avoid reading garbage from page_private(page) above. 115 * If the WARN_ON triggers during a swapoff it maybe the race 116 * condition and it's harmless. However if it triggers without 117 * swapoff it signals a problem. 118 */ 119 WARN_ON(page_count(page) <= 1); 120 121 bdi = bdev->bd_inode->i_mapping->backing_dev_info; 122 blk_run_backing_dev(bdi, page); 123 } 124 up_read(&swap_unplug_sem); 125} 126 127/* 128 * swapon tell device that all the old swap contents can be discarded, 129 * to allow the swap device to optimize its wear-levelling. 130 */ 131static int discard_swap(struct swap_info_struct *si) 132{ 133 struct swap_extent *se; 134 sector_t start_block; 135 sector_t nr_blocks; 136 int err = 0; 137 138 /* Do not discard the swap header page! */ 139 se = &si->first_swap_extent; 140 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9); 141 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9); 142 if (nr_blocks) { 143 err = blkdev_issue_discard(si->bdev, start_block, 144 nr_blocks, GFP_KERNEL, BLKDEV_IFL_WAIT); 145 if (err) 146 return err; 147 cond_resched(); 148 } 149 150 list_for_each_entry(se, &si->first_swap_extent.list, list) { 151 start_block = se->start_block << (PAGE_SHIFT - 9); 152 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9); 153 154 err = blkdev_issue_discard(si->bdev, start_block, 155 nr_blocks, GFP_KERNEL, BLKDEV_IFL_WAIT); 156 if (err) 157 break; 158 159 cond_resched(); 160 } 161 return err; /* That will often be -EOPNOTSUPP */ 162} 163 164/* 165 * swap allocation tell device that a cluster of swap can now be discarded, 166 * to allow the swap device to optimize its wear-levelling. 167 */ 168static void discard_swap_cluster(struct swap_info_struct *si, 169 pgoff_t start_page, pgoff_t nr_pages) 170{ 171 struct swap_extent *se = si->curr_swap_extent; 172 int found_extent = 0; 173 174 while (nr_pages) { 175 struct list_head *lh; 176 177 if (se->start_page <= start_page && 178 start_page < se->start_page + se->nr_pages) { 179 pgoff_t offset = start_page - se->start_page; 180 sector_t start_block = se->start_block + offset; 181 sector_t nr_blocks = se->nr_pages - offset; 182 183 if (nr_blocks > nr_pages) 184 nr_blocks = nr_pages; 185 start_page += nr_blocks; 186 nr_pages -= nr_blocks; 187 188 if (!found_extent++) 189 si->curr_swap_extent = se; 190 191 start_block <<= PAGE_SHIFT - 9; 192 nr_blocks <<= PAGE_SHIFT - 9; 193 if (blkdev_issue_discard(si->bdev, start_block, 194 nr_blocks, GFP_NOIO, BLKDEV_IFL_WAIT)) 195 break; 196 } 197 198 lh = se->list.next; 199 se = list_entry(lh, struct swap_extent, list); 200 } 201} 202 203static int wait_for_discard(void *word) 204{ 205 schedule(); 206 return 0; 207} 208 209#define SWAPFILE_CLUSTER 256 210#define LATENCY_LIMIT 256 211 212static inline unsigned long scan_swap_map(struct swap_info_struct *si, 213 unsigned char usage) 214{ 215 unsigned long offset; 216 unsigned long scan_base; 217 unsigned long last_in_cluster = 0; 218 int latency_ration = LATENCY_LIMIT; 219 int found_free_cluster = 0; 220 221 /* 222 * We try to cluster swap pages by allocating them sequentially 223 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this 224 * way, however, we resort to first-free allocation, starting 225 * a new cluster. This prevents us from scattering swap pages 226 * all over the entire swap partition, so that we reduce 227 * overall disk seek times between swap pages. -- sct 228 * But we do now try to find an empty cluster. -Andrea 229 * And we let swap pages go all over an SSD partition. Hugh 230 */ 231 232 si->flags += SWP_SCANNING; 233 scan_base = offset = si->cluster_next; 234 235 if (unlikely(!si->cluster_nr--)) { 236 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) { 237 si->cluster_nr = SWAPFILE_CLUSTER - 1; 238 goto checks; 239 } 240 if (si->flags & SWP_DISCARDABLE) { 241 /* 242 * Start range check on racing allocations, in case 243 * they overlap the cluster we eventually decide on 244 * (we scan without swap_lock to allow preemption). 245 * It's hardly conceivable that cluster_nr could be 246 * wrapped during our scan, but don't depend on it. 247 */ 248 if (si->lowest_alloc) 249 goto checks; 250 si->lowest_alloc = si->max; 251 si->highest_alloc = 0; 252 } 253 spin_unlock(&swap_lock); 254 255 /* 256 * If seek is expensive, start searching for new cluster from 257 * start of partition, to minimize the span of allocated swap. 258 * But if seek is cheap, search from our current position, so 259 * that swap is allocated from all over the partition: if the 260 * Flash Translation Layer only remaps within limited zones, 261 * we don't want to wear out the first zone too quickly. 262 */ 263 if (!(si->flags & SWP_SOLIDSTATE)) 264 scan_base = offset = si->lowest_bit; 265 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 266 267 /* Locate the first empty (unaligned) cluster */ 268 for (; last_in_cluster <= si->highest_bit; offset++) { 269 if (si->swap_map[offset]) 270 last_in_cluster = offset + SWAPFILE_CLUSTER; 271 else if (offset == last_in_cluster) { 272 spin_lock(&swap_lock); 273 offset -= SWAPFILE_CLUSTER - 1; 274 si->cluster_next = offset; 275 si->cluster_nr = SWAPFILE_CLUSTER - 1; 276 found_free_cluster = 1; 277 goto checks; 278 } 279 if (unlikely(--latency_ration < 0)) { 280 cond_resched(); 281 latency_ration = LATENCY_LIMIT; 282 } 283 } 284 285 offset = si->lowest_bit; 286 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 287 288 /* Locate the first empty (unaligned) cluster */ 289 for (; last_in_cluster < scan_base; offset++) { 290 if (si->swap_map[offset]) 291 last_in_cluster = offset + SWAPFILE_CLUSTER; 292 else if (offset == last_in_cluster) { 293 spin_lock(&swap_lock); 294 offset -= SWAPFILE_CLUSTER - 1; 295 si->cluster_next = offset; 296 si->cluster_nr = SWAPFILE_CLUSTER - 1; 297 found_free_cluster = 1; 298 goto checks; 299 } 300 if (unlikely(--latency_ration < 0)) { 301 cond_resched(); 302 latency_ration = LATENCY_LIMIT; 303 } 304 } 305 306 offset = scan_base; 307 spin_lock(&swap_lock); 308 si->cluster_nr = SWAPFILE_CLUSTER - 1; 309 si->lowest_alloc = 0; 310 } 311 312checks: 313 if (!(si->flags & SWP_WRITEOK)) 314 goto no_page; 315 if (!si->highest_bit) 316 goto no_page; 317 if (offset > si->highest_bit) 318 scan_base = offset = si->lowest_bit; 319 320 /* reuse swap entry of cache-only swap if not hibernation. */ 321 if (vm_swap_full() 322 && usage == SWAP_HAS_CACHE 323 && si->swap_map[offset] == SWAP_HAS_CACHE) { 324 int swap_was_freed; 325 spin_unlock(&swap_lock); 326 swap_was_freed = __try_to_reclaim_swap(si, offset); 327 spin_lock(&swap_lock); 328 /* entry was freed successfully, try to use this again */ 329 if (swap_was_freed) 330 goto checks; 331 goto scan; /* check next one */ 332 } 333 334 if (si->swap_map[offset]) 335 goto scan; 336 337 if (offset == si->lowest_bit) 338 si->lowest_bit++; 339 if (offset == si->highest_bit) 340 si->highest_bit--; 341 si->inuse_pages++; 342 if (si->inuse_pages == si->pages) { 343 si->lowest_bit = si->max; 344 si->highest_bit = 0; 345 } 346 si->swap_map[offset] = usage; 347 si->cluster_next = offset + 1; 348 si->flags -= SWP_SCANNING; 349 350 if (si->lowest_alloc) { 351 /* 352 * Only set when SWP_DISCARDABLE, and there's a scan 353 * for a free cluster in progress or just completed. 354 */ 355 if (found_free_cluster) { 356 /* 357 * To optimize wear-levelling, discard the 358 * old data of the cluster, taking care not to 359 * discard any of its pages that have already 360 * been allocated by racing tasks (offset has 361 * already stepped over any at the beginning). 362 */ 363 if (offset < si->highest_alloc && 364 si->lowest_alloc <= last_in_cluster) 365 last_in_cluster = si->lowest_alloc - 1; 366 si->flags |= SWP_DISCARDING; 367 spin_unlock(&swap_lock); 368 369 if (offset < last_in_cluster) 370 discard_swap_cluster(si, offset, 371 last_in_cluster - offset + 1); 372 373 spin_lock(&swap_lock); 374 si->lowest_alloc = 0; 375 si->flags &= ~SWP_DISCARDING; 376 377 smp_mb(); /* wake_up_bit advises this */ 378 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING)); 379 380 } else if (si->flags & SWP_DISCARDING) { 381 /* 382 * Delay using pages allocated by racing tasks 383 * until the whole discard has been issued. We 384 * could defer that delay until swap_writepage, 385 * but it's easier to keep this self-contained. 386 */ 387 spin_unlock(&swap_lock); 388 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING), 389 wait_for_discard, TASK_UNINTERRUPTIBLE); 390 spin_lock(&swap_lock); 391 } else { 392 /* 393 * Note pages allocated by racing tasks while 394 * scan for a free cluster is in progress, so 395 * that its final discard can exclude them. 396 */ 397 if (offset < si->lowest_alloc) 398 si->lowest_alloc = offset; 399 if (offset > si->highest_alloc) 400 si->highest_alloc = offset; 401 } 402 } 403 return offset; 404 405scan: 406 spin_unlock(&swap_lock); 407 while (++offset <= si->highest_bit) { 408 if (!si->swap_map[offset]) { 409 spin_lock(&swap_lock); 410 goto checks; 411 } 412 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 413 spin_lock(&swap_lock); 414 goto checks; 415 } 416 if (unlikely(--latency_ration < 0)) { 417 cond_resched(); 418 latency_ration = LATENCY_LIMIT; 419 } 420 } 421 offset = si->lowest_bit; 422 while (++offset < scan_base) { 423 if (!si->swap_map[offset]) { 424 spin_lock(&swap_lock); 425 goto checks; 426 } 427 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 428 spin_lock(&swap_lock); 429 goto checks; 430 } 431 if (unlikely(--latency_ration < 0)) { 432 cond_resched(); 433 latency_ration = LATENCY_LIMIT; 434 } 435 } 436 spin_lock(&swap_lock); 437 438no_page: 439 si->flags -= SWP_SCANNING; 440 return 0; 441} 442 443swp_entry_t get_swap_page(void) 444{ 445 struct swap_info_struct *si; 446 pgoff_t offset; 447 int type, next; 448 int wrapped = 0; 449 450 spin_lock(&swap_lock); 451 if (nr_swap_pages <= 0) 452 goto noswap; 453 if (swap_for_hibernation) 454 goto noswap; 455 nr_swap_pages--; 456 457 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { 458 si = swap_info[type]; 459 next = si->next; 460 if (next < 0 || 461 (!wrapped && si->prio != swap_info[next]->prio)) { 462 next = swap_list.head; 463 wrapped++; 464 } 465 466 if (!si->highest_bit) 467 continue; 468 if (!(si->flags & SWP_WRITEOK)) 469 continue; 470 471 swap_list.next = next; 472 /* This is called for allocating swap entry for cache */ 473 offset = scan_swap_map(si, SWAP_HAS_CACHE); 474 if (offset) { 475 spin_unlock(&swap_lock); 476 return swp_entry(type, offset); 477 } 478 next = swap_list.next; 479 } 480 481 nr_swap_pages++; 482noswap: 483 spin_unlock(&swap_lock); 484 return (swp_entry_t) {0}; 485} 486 487static struct swap_info_struct *swap_info_get(swp_entry_t entry) 488{ 489 struct swap_info_struct *p; 490 unsigned long offset, type; 491 492 if (!entry.val) 493 goto out; 494 type = swp_type(entry); 495 if (type >= nr_swapfiles) 496 goto bad_nofile; 497 p = swap_info[type]; 498 if (!(p->flags & SWP_USED)) 499 goto bad_device; 500 offset = swp_offset(entry); 501 if (offset >= p->max) 502 goto bad_offset; 503 if (!p->swap_map[offset]) 504 goto bad_free; 505 spin_lock(&swap_lock); 506 return p; 507 508bad_free: 509 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val); 510 goto out; 511bad_offset: 512 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val); 513 goto out; 514bad_device: 515 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val); 516 goto out; 517bad_nofile: 518 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val); 519out: 520 return NULL; 521} 522 523static unsigned char swap_entry_free(struct swap_info_struct *p, 524 swp_entry_t entry, unsigned char usage) 525{ 526 unsigned long offset = swp_offset(entry); 527 unsigned char count; 528 unsigned char has_cache; 529 530 count = p->swap_map[offset]; 531 has_cache = count & SWAP_HAS_CACHE; 532 count &= ~SWAP_HAS_CACHE; 533 534 if (usage == SWAP_HAS_CACHE) { 535 VM_BUG_ON(!has_cache); 536 has_cache = 0; 537 } else if (count == SWAP_MAP_SHMEM) { 538 /* 539 * Or we could insist on shmem.c using a special 540 * swap_shmem_free() and free_shmem_swap_and_cache()... 541 */ 542 count = 0; 543 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { 544 if (count == COUNT_CONTINUED) { 545 if (swap_count_continued(p, offset, count)) 546 count = SWAP_MAP_MAX | COUNT_CONTINUED; 547 else 548 count = SWAP_MAP_MAX; 549 } else 550 count--; 551 } 552 553 if (!count) 554 mem_cgroup_uncharge_swap(entry); 555 556 usage = count | has_cache; 557 p->swap_map[offset] = usage; 558 559 /* free if no reference */ 560 if (!usage) { 561 struct gendisk *disk = p->bdev->bd_disk; 562 if (offset < p->lowest_bit) 563 p->lowest_bit = offset; 564 if (offset > p->highest_bit) 565 p->highest_bit = offset; 566 if (swap_list.next >= 0 && 567 p->prio > swap_info[swap_list.next]->prio) 568 swap_list.next = p->type; 569 nr_swap_pages++; 570 p->inuse_pages--; 571 if ((p->flags & SWP_BLKDEV) && 572 disk->fops->swap_slot_free_notify) 573 disk->fops->swap_slot_free_notify(p->bdev, offset); 574 } 575 576 return usage; 577} 578 579/* 580 * Caller has made sure that the swapdevice corresponding to entry 581 * is still around or has not been recycled. 582 */ 583void swap_free(swp_entry_t entry) 584{ 585 struct swap_info_struct *p; 586 587 p = swap_info_get(entry); 588 if (p) { 589 swap_entry_free(p, entry, 1); 590 spin_unlock(&swap_lock); 591 } 592} 593 594/* 595 * Called after dropping swapcache to decrease refcnt to swap entries. 596 */ 597void swapcache_free(swp_entry_t entry, struct page *page) 598{ 599 struct swap_info_struct *p; 600 unsigned char count; 601 602 p = swap_info_get(entry); 603 if (p) { 604 count = swap_entry_free(p, entry, SWAP_HAS_CACHE); 605 if (page) 606 mem_cgroup_uncharge_swapcache(page, entry, count != 0); 607 spin_unlock(&swap_lock); 608 } 609} 610 611/* 612 * How many references to page are currently swapped out? 613 * This does not give an exact answer when swap count is continued, 614 * but does include the high COUNT_CONTINUED flag to allow for that. 615 */ 616static inline int page_swapcount(struct page *page) 617{ 618 int count = 0; 619 struct swap_info_struct *p; 620 swp_entry_t entry; 621 622 entry.val = page_private(page); 623 p = swap_info_get(entry); 624 if (p) { 625 count = swap_count(p->swap_map[swp_offset(entry)]); 626 spin_unlock(&swap_lock); 627 } 628 return count; 629} 630 631/* 632 * We can write to an anon page without COW if there are no other references 633 * to it. And as a side-effect, free up its swap: because the old content 634 * on disk will never be read, and seeking back there to write new content 635 * later would only waste time away from clustering. 636 */ 637int reuse_swap_page(struct page *page) 638{ 639 int count; 640 641 VM_BUG_ON(!PageLocked(page)); 642 if (unlikely(PageKsm(page))) 643 return 0; 644 count = page_mapcount(page); 645 if (count <= 1 && PageSwapCache(page)) { 646 count += page_swapcount(page); 647 if (count == 1 && !PageWriteback(page)) { 648 delete_from_swap_cache(page); 649 SetPageDirty(page); 650 } 651 } 652 return count <= 1; 653} 654 655/* 656 * If swap is getting full, or if there are no more mappings of this page, 657 * then try_to_free_swap is called to free its swap space. 658 */ 659int try_to_free_swap(struct page *page) 660{ 661 VM_BUG_ON(!PageLocked(page)); 662 663 if (!PageSwapCache(page)) 664 return 0; 665 if (PageWriteback(page)) 666 return 0; 667 if (page_swapcount(page)) 668 return 0; 669 670 delete_from_swap_cache(page); 671 SetPageDirty(page); 672 return 1; 673} 674 675/* 676 * Free the swap entry like above, but also try to 677 * free the page cache entry if it is the last user. 678 */ 679int free_swap_and_cache(swp_entry_t entry) 680{ 681 struct swap_info_struct *p; 682 struct page *page = NULL; 683 684 if (non_swap_entry(entry)) 685 return 1; 686 687 p = swap_info_get(entry); 688 if (p) { 689 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) { 690 page = find_get_page(&swapper_space, entry.val); 691 if (page && !trylock_page(page)) { 692 page_cache_release(page); 693 page = NULL; 694 } 695 } 696 spin_unlock(&swap_lock); 697 } 698 if (page) { 699 /* 700 * Not mapped elsewhere, or swap space full? Free it! 701 * Also recheck PageSwapCache now page is locked (above). 702 */ 703 if (PageSwapCache(page) && !PageWriteback(page) && 704 (!page_mapped(page) || vm_swap_full())) { 705 delete_from_swap_cache(page); 706 SetPageDirty(page); 707 } 708 unlock_page(page); 709 page_cache_release(page); 710 } 711 return p != NULL; 712} 713 714#ifdef CONFIG_CGROUP_MEM_RES_CTLR 715/** 716 * mem_cgroup_count_swap_user - count the user of a swap entry 717 * @ent: the swap entry to be checked 718 * @pagep: the pointer for the swap cache page of the entry to be stored 719 * 720 * Returns the number of the user of the swap entry. The number is valid only 721 * for swaps of anonymous pages. 722 * If the entry is found on swap cache, the page is stored to pagep with 723 * refcount of it being incremented. 724 */ 725int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep) 726{ 727 struct page *page; 728 struct swap_info_struct *p; 729 int count = 0; 730 731 page = find_get_page(&swapper_space, ent.val); 732 if (page) 733 count += page_mapcount(page); 734 p = swap_info_get(ent); 735 if (p) { 736 count += swap_count(p->swap_map[swp_offset(ent)]); 737 spin_unlock(&swap_lock); 738 } 739 740 *pagep = page; 741 return count; 742} 743#endif 744 745#ifdef CONFIG_HIBERNATION 746 747static pgoff_t hibernation_offset[MAX_SWAPFILES]; 748/* 749 * Once hibernation starts to use swap, we freeze swap_map[]. Otherwise, 750 * saved swap_map[] image to the disk will be an incomplete because it's 751 * changing without synchronization with hibernation snap shot. 752 * At resume, we just make swap_for_hibernation=false. We can forget 753 * used maps easily. 754 */ 755void hibernation_freeze_swap(void) 756{ 757 int i; 758 759 spin_lock(&swap_lock); 760 761 printk(KERN_INFO "PM: Freeze Swap\n"); 762 swap_for_hibernation = true; 763 for (i = 0; i < MAX_SWAPFILES; i++) 764 hibernation_offset[i] = 1; 765 spin_unlock(&swap_lock); 766} 767 768void hibernation_thaw_swap(void) 769{ 770 spin_lock(&swap_lock); 771 if (swap_for_hibernation) { 772 printk(KERN_INFO "PM: Thaw Swap\n"); 773 swap_for_hibernation = false; 774 } 775 spin_unlock(&swap_lock); 776} 777 778/* 779 * Because updateing swap_map[] can make not-saved-status-change, 780 * we use our own easy allocator. 781 * Please see kernel/power/swap.c, Used swaps are recorded into 782 * RB-tree. 783 */ 784swp_entry_t get_swap_for_hibernation(int type) 785{ 786 pgoff_t off; 787 swp_entry_t val = {0}; 788 struct swap_info_struct *si; 789 790 spin_lock(&swap_lock); 791 792 si = swap_info[type]; 793 if (!si || !(si->flags & SWP_WRITEOK)) 794 goto done; 795 796 for (off = hibernation_offset[type]; off < si->max; ++off) { 797 if (!si->swap_map[off]) 798 break; 799 } 800 if (off < si->max) { 801 val = swp_entry(type, off); 802 hibernation_offset[type] = off + 1; 803 } 804done: 805 spin_unlock(&swap_lock); 806 return val; 807} 808 809void swap_free_for_hibernation(swp_entry_t ent) 810{ 811 /* Nothing to do */ 812} 813 814/* 815 * Find the swap type that corresponds to given device (if any). 816 * 817 * @offset - number of the PAGE_SIZE-sized block of the device, starting 818 * from 0, in which the swap header is expected to be located. 819 * 820 * This is needed for the suspend to disk (aka swsusp). 821 */ 822int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p) 823{ 824 struct block_device *bdev = NULL; 825 int type; 826 827 if (device) 828 bdev = bdget(device); 829 830 spin_lock(&swap_lock); 831 for (type = 0; type < nr_swapfiles; type++) { 832 struct swap_info_struct *sis = swap_info[type]; 833 834 if (!(sis->flags & SWP_WRITEOK)) 835 continue; 836 837 if (!bdev) { 838 if (bdev_p) 839 *bdev_p = bdgrab(sis->bdev); 840 841 spin_unlock(&swap_lock); 842 return type; 843 } 844 if (bdev == sis->bdev) { 845 struct swap_extent *se = &sis->first_swap_extent; 846 847 if (se->start_block == offset) { 848 if (bdev_p) 849 *bdev_p = bdgrab(sis->bdev); 850 851 spin_unlock(&swap_lock); 852 bdput(bdev); 853 return type; 854 } 855 } 856 } 857 spin_unlock(&swap_lock); 858 if (bdev) 859 bdput(bdev); 860 861 return -ENODEV; 862} 863 864/* 865 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev 866 * corresponding to given index in swap_info (swap type). 867 */ 868sector_t swapdev_block(int type, pgoff_t offset) 869{ 870 struct block_device *bdev; 871 872 if ((unsigned int)type >= nr_swapfiles) 873 return 0; 874 if (!(swap_info[type]->flags & SWP_WRITEOK)) 875 return 0; 876 return map_swap_entry(swp_entry(type, offset), &bdev); 877} 878 879/* 880 * Return either the total number of swap pages of given type, or the number 881 * of free pages of that type (depending on @free) 882 * 883 * This is needed for software suspend 884 */ 885unsigned int count_swap_pages(int type, int free) 886{ 887 unsigned int n = 0; 888 889 spin_lock(&swap_lock); 890 if ((unsigned int)type < nr_swapfiles) { 891 struct swap_info_struct *sis = swap_info[type]; 892 893 if (sis->flags & SWP_WRITEOK) { 894 n = sis->pages; 895 if (free) 896 n -= sis->inuse_pages; 897 } 898 } 899 spin_unlock(&swap_lock); 900 return n; 901} 902#endif /* CONFIG_HIBERNATION */ 903 904/* 905 * No need to decide whether this PTE shares the swap entry with others, 906 * just let do_wp_page work it out if a write is requested later - to 907 * force COW, vm_page_prot omits write permission from any private vma. 908 */ 909static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, 910 unsigned long addr, swp_entry_t entry, struct page *page) 911{ 912 struct mem_cgroup *ptr = NULL; 913 spinlock_t *ptl; 914 pte_t *pte; 915 int ret = 1; 916 917 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) { 918 ret = -ENOMEM; 919 goto out_nolock; 920 } 921 922 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 923 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) { 924 if (ret > 0) 925 mem_cgroup_cancel_charge_swapin(ptr); 926 ret = 0; 927 goto out; 928 } 929 930 dec_mm_counter(vma->vm_mm, MM_SWAPENTS); 931 inc_mm_counter(vma->vm_mm, MM_ANONPAGES); 932 get_page(page); 933 set_pte_at(vma->vm_mm, addr, pte, 934 pte_mkold(mk_pte(page, vma->vm_page_prot))); 935 page_add_anon_rmap(page, vma, addr); 936 mem_cgroup_commit_charge_swapin(page, ptr); 937 swap_free(entry); 938 /* 939 * Move the page to the active list so it is not 940 * immediately swapped out again after swapon. 941 */ 942 activate_page(page); 943out: 944 pte_unmap_unlock(pte, ptl); 945out_nolock: 946 return ret; 947} 948 949static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 950 unsigned long addr, unsigned long end, 951 swp_entry_t entry, struct page *page) 952{ 953 pte_t swp_pte = swp_entry_to_pte(entry); 954 pte_t *pte; 955 int ret = 0; 956 957 /* 958 * We don't actually need pte lock while scanning for swp_pte: since 959 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the 960 * page table while we're scanning; though it could get zapped, and on 961 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse 962 * of unmatched parts which look like swp_pte, so unuse_pte must 963 * recheck under pte lock. Scanning without pte lock lets it be 964 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE. 965 */ 966 pte = pte_offset_map(pmd, addr); 967 do { 968 /* 969 * swapoff spends a _lot_ of time in this loop! 970 * Test inline before going to call unuse_pte. 971 */ 972 if (unlikely(pte_same(*pte, swp_pte))) { 973 pte_unmap(pte); 974 ret = unuse_pte(vma, pmd, addr, entry, page); 975 if (ret) 976 goto out; 977 pte = pte_offset_map(pmd, addr); 978 } 979 } while (pte++, addr += PAGE_SIZE, addr != end); 980 pte_unmap(pte - 1); 981out: 982 return ret; 983} 984 985static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, 986 unsigned long addr, unsigned long end, 987 swp_entry_t entry, struct page *page) 988{ 989 pmd_t *pmd; 990 unsigned long next; 991 int ret; 992 993 pmd = pmd_offset(pud, addr); 994 do { 995 next = pmd_addr_end(addr, end); 996 if (pmd_none_or_clear_bad(pmd)) 997 continue; 998 ret = unuse_pte_range(vma, pmd, addr, next, entry, page); 999 if (ret) 1000 return ret; 1001 } while (pmd++, addr = next, addr != end); 1002 return 0; 1003} 1004 1005static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd, 1006 unsigned long addr, unsigned long end, 1007 swp_entry_t entry, struct page *page) 1008{ 1009 pud_t *pud; 1010 unsigned long next; 1011 int ret; 1012 1013 pud = pud_offset(pgd, addr); 1014 do { 1015 next = pud_addr_end(addr, end); 1016 if (pud_none_or_clear_bad(pud)) 1017 continue; 1018 ret = unuse_pmd_range(vma, pud, addr, next, entry, page); 1019 if (ret) 1020 return ret; 1021 } while (pud++, addr = next, addr != end); 1022 return 0; 1023} 1024 1025static int unuse_vma(struct vm_area_struct *vma, 1026 swp_entry_t entry, struct page *page) 1027{ 1028 pgd_t *pgd; 1029 unsigned long addr, end, next; 1030 int ret; 1031 1032 if (page_anon_vma(page)) { 1033 addr = page_address_in_vma(page, vma); 1034 if (addr == -EFAULT) 1035 return 0; 1036 else 1037 end = addr + PAGE_SIZE; 1038 } else { 1039 addr = vma->vm_start; 1040 end = vma->vm_end; 1041 } 1042 1043 pgd = pgd_offset(vma->vm_mm, addr); 1044 do { 1045 next = pgd_addr_end(addr, end); 1046 if (pgd_none_or_clear_bad(pgd)) 1047 continue; 1048 ret = unuse_pud_range(vma, pgd, addr, next, entry, page); 1049 if (ret) 1050 return ret; 1051 } while (pgd++, addr = next, addr != end); 1052 return 0; 1053} 1054 1055static int unuse_mm(struct mm_struct *mm, 1056 swp_entry_t entry, struct page *page) 1057{ 1058 struct vm_area_struct *vma; 1059 int ret = 0; 1060 1061 if (!down_read_trylock(&mm->mmap_sem)) { 1062 /* 1063 * Activate page so shrink_inactive_list is unlikely to unmap 1064 * its ptes while lock is dropped, so swapoff can make progress. 1065 */ 1066 activate_page(page); 1067 unlock_page(page); 1068 down_read(&mm->mmap_sem); 1069 lock_page(page); 1070 } 1071 for (vma = mm->mmap; vma; vma = vma->vm_next) { 1072 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page))) 1073 break; 1074 } 1075 up_read(&mm->mmap_sem); 1076 return (ret < 0)? ret: 0; 1077} 1078 1079/* 1080 * Scan swap_map from current position to next entry still in use. 1081 * Recycle to start on reaching the end, returning 0 when empty. 1082 */ 1083static unsigned int find_next_to_unuse(struct swap_info_struct *si, 1084 unsigned int prev) 1085{ 1086 unsigned int max = si->max; 1087 unsigned int i = prev; 1088 unsigned char count; 1089 1090 /* 1091 * No need for swap_lock here: we're just looking 1092 * for whether an entry is in use, not modifying it; false 1093 * hits are okay, and sys_swapoff() has already prevented new 1094 * allocations from this area (while holding swap_lock). 1095 */ 1096 for (;;) { 1097 if (++i >= max) { 1098 if (!prev) { 1099 i = 0; 1100 break; 1101 } 1102 /* 1103 * No entries in use at top of swap_map, 1104 * loop back to start and recheck there. 1105 */ 1106 max = prev + 1; 1107 prev = 0; 1108 i = 1; 1109 } 1110 count = si->swap_map[i]; 1111 if (count && swap_count(count) != SWAP_MAP_BAD) 1112 break; 1113 } 1114 return i; 1115} 1116 1117/* 1118 * We completely avoid races by reading each swap page in advance, 1119 * and then search for the process using it. All the necessary 1120 * page table adjustments can then be made atomically. 1121 */ 1122static int try_to_unuse(unsigned int type) 1123{ 1124 struct swap_info_struct *si = swap_info[type]; 1125 struct mm_struct *start_mm; 1126 unsigned char *swap_map; 1127 unsigned char swcount; 1128 struct page *page; 1129 swp_entry_t entry; 1130 unsigned int i = 0; 1131 int retval = 0; 1132 1133 /* 1134 * When searching mms for an entry, a good strategy is to 1135 * start at the first mm we freed the previous entry from 1136 * (though actually we don't notice whether we or coincidence 1137 * freed the entry). Initialize this start_mm with a hold. 1138 * 1139 * A simpler strategy would be to start at the last mm we 1140 * freed the previous entry from; but that would take less 1141 * advantage of mmlist ordering, which clusters forked mms 1142 * together, child after parent. If we race with dup_mmap(), we 1143 * prefer to resolve parent before child, lest we miss entries 1144 * duplicated after we scanned child: using last mm would invert 1145 * that. 1146 */ 1147 start_mm = &init_mm; 1148 atomic_inc(&init_mm.mm_users); 1149 1150 /* 1151 * Keep on scanning until all entries have gone. Usually, 1152 * one pass through swap_map is enough, but not necessarily: 1153 * there are races when an instance of an entry might be missed. 1154 */ 1155 while ((i = find_next_to_unuse(si, i)) != 0) { 1156 if (signal_pending(current)) { 1157 retval = -EINTR; 1158 break; 1159 } 1160 1161 /* 1162 * Get a page for the entry, using the existing swap 1163 * cache page if there is one. Otherwise, get a clean 1164 * page and read the swap into it. 1165 */ 1166 swap_map = &si->swap_map[i]; 1167 entry = swp_entry(type, i); 1168 page = read_swap_cache_async(entry, 1169 GFP_HIGHUSER_MOVABLE, NULL, 0); 1170 if (!page) { 1171 /* 1172 * Either swap_duplicate() failed because entry 1173 * has been freed independently, and will not be 1174 * reused since sys_swapoff() already disabled 1175 * allocation from here, or alloc_page() failed. 1176 */ 1177 if (!*swap_map) 1178 continue; 1179 retval = -ENOMEM; 1180 break; 1181 } 1182 1183 /* 1184 * Don't hold on to start_mm if it looks like exiting. 1185 */ 1186 if (atomic_read(&start_mm->mm_users) == 1) { 1187 mmput(start_mm); 1188 start_mm = &init_mm; 1189 atomic_inc(&init_mm.mm_users); 1190 } 1191 1192 /* 1193 * Wait for and lock page. When do_swap_page races with 1194 * try_to_unuse, do_swap_page can handle the fault much 1195 * faster than try_to_unuse can locate the entry. This 1196 * apparently redundant "wait_on_page_locked" lets try_to_unuse 1197 * defer to do_swap_page in such a case - in some tests, 1198 * do_swap_page and try_to_unuse repeatedly compete. 1199 */ 1200 wait_on_page_locked(page); 1201 wait_on_page_writeback(page); 1202 lock_page(page); 1203 wait_on_page_writeback(page); 1204 1205 /* 1206 * Remove all references to entry. 1207 */ 1208 swcount = *swap_map; 1209 if (swap_count(swcount) == SWAP_MAP_SHMEM) { 1210 retval = shmem_unuse(entry, page); 1211 /* page has already been unlocked and released */ 1212 if (retval < 0) 1213 break; 1214 continue; 1215 } 1216 if (swap_count(swcount) && start_mm != &init_mm) 1217 retval = unuse_mm(start_mm, entry, page); 1218 1219 if (swap_count(*swap_map)) { 1220 int set_start_mm = (*swap_map >= swcount); 1221 struct list_head *p = &start_mm->mmlist; 1222 struct mm_struct *new_start_mm = start_mm; 1223 struct mm_struct *prev_mm = start_mm; 1224 struct mm_struct *mm; 1225 1226 atomic_inc(&new_start_mm->mm_users); 1227 atomic_inc(&prev_mm->mm_users); 1228 spin_lock(&mmlist_lock); 1229 while (swap_count(*swap_map) && !retval && 1230 (p = p->next) != &start_mm->mmlist) { 1231 mm = list_entry(p, struct mm_struct, mmlist); 1232 if (!atomic_inc_not_zero(&mm->mm_users)) 1233 continue; 1234 spin_unlock(&mmlist_lock); 1235 mmput(prev_mm); 1236 prev_mm = mm; 1237 1238 cond_resched(); 1239 1240 swcount = *swap_map; 1241 if (!swap_count(swcount)) /* any usage ? */ 1242 ; 1243 else if (mm == &init_mm) 1244 set_start_mm = 1; 1245 else 1246 retval = unuse_mm(mm, entry, page); 1247 1248 if (set_start_mm && *swap_map < swcount) { 1249 mmput(new_start_mm); 1250 atomic_inc(&mm->mm_users); 1251 new_start_mm = mm; 1252 set_start_mm = 0; 1253 } 1254 spin_lock(&mmlist_lock); 1255 } 1256 spin_unlock(&mmlist_lock); 1257 mmput(prev_mm); 1258 mmput(start_mm); 1259 start_mm = new_start_mm; 1260 } 1261 if (retval) { 1262 unlock_page(page); 1263 page_cache_release(page); 1264 break; 1265 } 1266 1267 /* 1268 * If a reference remains (rare), we would like to leave 1269 * the page in the swap cache; but try_to_unmap could 1270 * then re-duplicate the entry once we drop page lock, 1271 * so we might loop indefinitely; also, that page could 1272 * not be swapped out to other storage meanwhile. So: 1273 * delete from cache even if there's another reference, 1274 * after ensuring that the data has been saved to disk - 1275 * since if the reference remains (rarer), it will be 1276 * read from disk into another page. Splitting into two 1277 * pages would be incorrect if swap supported "shared 1278 * private" pages, but they are handled by tmpfs files. 1279 * 1280 * Given how unuse_vma() targets one particular offset 1281 * in an anon_vma, once the anon_vma has been determined, 1282 * this splitting happens to be just what is needed to 1283 * handle where KSM pages have been swapped out: re-reading 1284 * is unnecessarily slow, but we can fix that later on. 1285 */ 1286 if (swap_count(*swap_map) && 1287 PageDirty(page) && PageSwapCache(page)) { 1288 struct writeback_control wbc = { 1289 .sync_mode = WB_SYNC_NONE, 1290 }; 1291 1292 swap_writepage(page, &wbc); 1293 lock_page(page); 1294 wait_on_page_writeback(page); 1295 } 1296 1297 /* 1298 * It is conceivable that a racing task removed this page from 1299 * swap cache just before we acquired the page lock at the top, 1300 * or while we dropped it in unuse_mm(). The page might even 1301 * be back in swap cache on another swap area: that we must not 1302 * delete, since it may not have been written out to swap yet. 1303 */ 1304 if (PageSwapCache(page) && 1305 likely(page_private(page) == entry.val)) 1306 delete_from_swap_cache(page); 1307 1308 /* 1309 * So we could skip searching mms once swap count went 1310 * to 1, we did not mark any present ptes as dirty: must 1311 * mark page dirty so shrink_page_list will preserve it. 1312 */ 1313 SetPageDirty(page); 1314 unlock_page(page); 1315 page_cache_release(page); 1316 1317 /* 1318 * Make sure that we aren't completely killing 1319 * interactive performance. 1320 */ 1321 cond_resched(); 1322 } 1323 1324 mmput(start_mm); 1325 return retval; 1326} 1327 1328/* 1329 * After a successful try_to_unuse, if no swap is now in use, we know 1330 * we can empty the mmlist. swap_lock must be held on entry and exit. 1331 * Note that mmlist_lock nests inside swap_lock, and an mm must be 1332 * added to the mmlist just after page_duplicate - before would be racy. 1333 */ 1334static void drain_mmlist(void) 1335{ 1336 struct list_head *p, *next; 1337 unsigned int type; 1338 1339 for (type = 0; type < nr_swapfiles; type++) 1340 if (swap_info[type]->inuse_pages) 1341 return; 1342 spin_lock(&mmlist_lock); 1343 list_for_each_safe(p, next, &init_mm.mmlist) 1344 list_del_init(p); 1345 spin_unlock(&mmlist_lock); 1346} 1347 1348/* 1349 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which 1350 * corresponds to page offset for the specified swap entry. 1351 * Note that the type of this function is sector_t, but it returns page offset 1352 * into the bdev, not sector offset. 1353 */ 1354static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev) 1355{ 1356 struct swap_info_struct *sis; 1357 struct swap_extent *start_se; 1358 struct swap_extent *se; 1359 pgoff_t offset; 1360 1361 sis = swap_info[swp_type(entry)]; 1362 *bdev = sis->bdev; 1363 1364 offset = swp_offset(entry); 1365 start_se = sis->curr_swap_extent; 1366 se = start_se; 1367 1368 for ( ; ; ) { 1369 struct list_head *lh; 1370 1371 if (se->start_page <= offset && 1372 offset < (se->start_page + se->nr_pages)) { 1373 return se->start_block + (offset - se->start_page); 1374 } 1375 lh = se->list.next; 1376 se = list_entry(lh, struct swap_extent, list); 1377 sis->curr_swap_extent = se; 1378 BUG_ON(se == start_se); /* It *must* be present */ 1379 } 1380} 1381 1382/* 1383 * Returns the page offset into bdev for the specified page's swap entry. 1384 */ 1385sector_t map_swap_page(struct page *page, struct block_device **bdev) 1386{ 1387 swp_entry_t entry; 1388 entry.val = page_private(page); 1389 return map_swap_entry(entry, bdev); 1390} 1391 1392/* 1393 * Free all of a swapdev's extent information 1394 */ 1395static void destroy_swap_extents(struct swap_info_struct *sis) 1396{ 1397 while (!list_empty(&sis->first_swap_extent.list)) { 1398 struct swap_extent *se; 1399 1400 se = list_entry(sis->first_swap_extent.list.next, 1401 struct swap_extent, list); 1402 list_del(&se->list); 1403 kfree(se); 1404 } 1405} 1406 1407/* 1408 * Add a block range (and the corresponding page range) into this swapdev's 1409 * extent list. The extent list is kept sorted in page order. 1410 * 1411 * This function rather assumes that it is called in ascending page order. 1412 */ 1413static int 1414add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, 1415 unsigned long nr_pages, sector_t start_block) 1416{ 1417 struct swap_extent *se; 1418 struct swap_extent *new_se; 1419 struct list_head *lh; 1420 1421 if (start_page == 0) { 1422 se = &sis->first_swap_extent; 1423 sis->curr_swap_extent = se; 1424 se->start_page = 0; 1425 se->nr_pages = nr_pages; 1426 se->start_block = start_block; 1427 return 1; 1428 } else { 1429 lh = sis->first_swap_extent.list.prev; /* Highest extent */ 1430 se = list_entry(lh, struct swap_extent, list); 1431 BUG_ON(se->start_page + se->nr_pages != start_page); 1432 if (se->start_block + se->nr_pages == start_block) { 1433 /* Merge it */ 1434 se->nr_pages += nr_pages; 1435 return 0; 1436 } 1437 } 1438 1439 /* 1440 * No merge. Insert a new extent, preserving ordering. 1441 */ 1442 new_se = kmalloc(sizeof(*se), GFP_KERNEL); 1443 if (new_se == NULL) 1444 return -ENOMEM; 1445 new_se->start_page = start_page; 1446 new_se->nr_pages = nr_pages; 1447 new_se->start_block = start_block; 1448 1449 list_add_tail(&new_se->list, &sis->first_swap_extent.list); 1450 return 1; 1451} 1452 1453/* 1454 * A `swap extent' is a simple thing which maps a contiguous range of pages 1455 * onto a contiguous range of disk blocks. An ordered list of swap extents 1456 * is built at swapon time and is then used at swap_writepage/swap_readpage 1457 * time for locating where on disk a page belongs. 1458 * 1459 * If the swapfile is an S_ISBLK block device, a single extent is installed. 1460 * This is done so that the main operating code can treat S_ISBLK and S_ISREG 1461 * swap files identically. 1462 * 1463 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap 1464 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK 1465 * swapfiles are handled *identically* after swapon time. 1466 * 1467 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks 1468 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If 1469 * some stray blocks are found which do not fall within the PAGE_SIZE alignment 1470 * requirements, they are simply tossed out - we will never use those blocks 1471 * for swapping. 1472 * 1473 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This 1474 * prevents root from shooting her foot off by ftruncating an in-use swapfile, 1475 * which will scribble on the fs. 1476 * 1477 * The amount of disk space which a single swap extent represents varies. 1478 * Typically it is in the 1-4 megabyte range. So we can have hundreds of 1479 * extents in the list. To avoid much list walking, we cache the previous 1480 * search location in `curr_swap_extent', and start new searches from there. 1481 * This is extremely effective. The average number of iterations in 1482 * map_swap_page() has been measured at about 0.3 per page. - akpm. 1483 */ 1484static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) 1485{ 1486 struct inode *inode; 1487 unsigned blocks_per_page; 1488 unsigned long page_no; 1489 unsigned blkbits; 1490 sector_t probe_block; 1491 sector_t last_block; 1492 sector_t lowest_block = -1; 1493 sector_t highest_block = 0; 1494 int nr_extents = 0; 1495 int ret; 1496 1497 inode = sis->swap_file->f_mapping->host; 1498 if (S_ISBLK(inode->i_mode)) { 1499 ret = add_swap_extent(sis, 0, sis->max, 0); 1500 *span = sis->pages; 1501 goto out; 1502 } 1503 1504 blkbits = inode->i_blkbits; 1505 blocks_per_page = PAGE_SIZE >> blkbits; 1506 1507 /* 1508 * Map all the blocks into the extent list. This code doesn't try 1509 * to be very smart. 1510 */ 1511 probe_block = 0; 1512 page_no = 0; 1513 last_block = i_size_read(inode) >> blkbits; 1514 while ((probe_block + blocks_per_page) <= last_block && 1515 page_no < sis->max) { 1516 unsigned block_in_page; 1517 sector_t first_block; 1518 1519 first_block = bmap(inode, probe_block); 1520 if (first_block == 0) 1521 goto bad_bmap; 1522 1523 /* 1524 * It must be PAGE_SIZE aligned on-disk 1525 */ 1526 if (first_block & (blocks_per_page - 1)) { 1527 probe_block++; 1528 goto reprobe; 1529 } 1530 1531 for (block_in_page = 1; block_in_page < blocks_per_page; 1532 block_in_page++) { 1533 sector_t block; 1534 1535 block = bmap(inode, probe_block + block_in_page); 1536 if (block == 0) 1537 goto bad_bmap; 1538 if (block != first_block + block_in_page) { 1539 /* Discontiguity */ 1540 probe_block++; 1541 goto reprobe; 1542 } 1543 } 1544 1545 first_block >>= (PAGE_SHIFT - blkbits); 1546 if (page_no) { /* exclude the header page */ 1547 if (first_block < lowest_block) 1548 lowest_block = first_block; 1549 if (first_block > highest_block) 1550 highest_block = first_block; 1551 } 1552 1553 /* 1554 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 1555 */ 1556 ret = add_swap_extent(sis, page_no, 1, first_block); 1557 if (ret < 0) 1558 goto out; 1559 nr_extents += ret; 1560 page_no++; 1561 probe_block += blocks_per_page; 1562reprobe: 1563 continue; 1564 } 1565 ret = nr_extents; 1566 *span = 1 + highest_block - lowest_block; 1567 if (page_no == 0) 1568 page_no = 1; /* force Empty message */ 1569 sis->max = page_no; 1570 sis->pages = page_no - 1; 1571 sis->highest_bit = page_no - 1; 1572out: 1573 return ret; 1574bad_bmap: 1575 printk(KERN_ERR "swapon: swapfile has holes\n"); 1576 ret = -EINVAL; 1577 goto out; 1578} 1579 1580SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) 1581{ 1582 struct swap_info_struct *p = NULL; 1583 unsigned char *swap_map; 1584 struct file *swap_file, *victim; 1585 struct address_space *mapping; 1586 struct inode *inode; 1587 char *pathname; 1588 int i, type, prev; 1589 int err; 1590 1591 if (!capable(CAP_SYS_ADMIN)) 1592 return -EPERM; 1593 1594 pathname = getname(specialfile); 1595 err = PTR_ERR(pathname); 1596 if (IS_ERR(pathname)) 1597 goto out; 1598 1599 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0); 1600 putname(pathname); 1601 err = PTR_ERR(victim); 1602 if (IS_ERR(victim)) 1603 goto out; 1604 1605 mapping = victim->f_mapping; 1606 prev = -1; 1607 spin_lock(&swap_lock); 1608 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) { 1609 p = swap_info[type]; 1610 if (p->flags & SWP_WRITEOK) { 1611 if (p->swap_file->f_mapping == mapping) 1612 break; 1613 } 1614 prev = type; 1615 } 1616 if (type < 0) { 1617 err = -EINVAL; 1618 spin_unlock(&swap_lock); 1619 goto out_dput; 1620 } 1621 if (!security_vm_enough_memory(p->pages)) 1622 vm_unacct_memory(p->pages); 1623 else { 1624 err = -ENOMEM; 1625 spin_unlock(&swap_lock); 1626 goto out_dput; 1627 } 1628 if (prev < 0) 1629 swap_list.head = p->next; 1630 else 1631 swap_info[prev]->next = p->next; 1632 if (type == swap_list.next) { 1633 /* just pick something that's safe... */ 1634 swap_list.next = swap_list.head; 1635 } 1636 if (p->prio < 0) { 1637 for (i = p->next; i >= 0; i = swap_info[i]->next) 1638 swap_info[i]->prio = p->prio--; 1639 least_priority++; 1640 } 1641 nr_swap_pages -= p->pages; 1642 total_swap_pages -= p->pages; 1643 p->flags &= ~SWP_WRITEOK; 1644 spin_unlock(&swap_lock); 1645 1646 current->flags |= PF_OOM_ORIGIN; 1647 err = try_to_unuse(type); 1648 current->flags &= ~PF_OOM_ORIGIN; 1649 1650 if (err) { 1651 /* re-insert swap space back into swap_list */ 1652 spin_lock(&swap_lock); 1653 if (p->prio < 0) 1654 p->prio = --least_priority; 1655 prev = -1; 1656 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { 1657 if (p->prio >= swap_info[i]->prio) 1658 break; 1659 prev = i; 1660 } 1661 p->next = i; 1662 if (prev < 0) 1663 swap_list.head = swap_list.next = type; 1664 else 1665 swap_info[prev]->next = type; 1666 nr_swap_pages += p->pages; 1667 total_swap_pages += p->pages; 1668 p->flags |= SWP_WRITEOK; 1669 spin_unlock(&swap_lock); 1670 goto out_dput; 1671 } 1672 1673 /* wait for any unplug function to finish */ 1674 down_write(&swap_unplug_sem); 1675 up_write(&swap_unplug_sem); 1676 1677 destroy_swap_extents(p); 1678 if (p->flags & SWP_CONTINUED) 1679 free_swap_count_continuations(p); 1680 1681 mutex_lock(&swapon_mutex); 1682 spin_lock(&swap_lock); 1683 drain_mmlist(); 1684 1685 /* wait for anyone still in scan_swap_map */ 1686 p->highest_bit = 0; /* cuts scans short */ 1687 while (p->flags >= SWP_SCANNING) { 1688 spin_unlock(&swap_lock); 1689 schedule_timeout_uninterruptible(1); 1690 spin_lock(&swap_lock); 1691 } 1692 1693 swap_file = p->swap_file; 1694 p->swap_file = NULL; 1695 p->max = 0; 1696 swap_map = p->swap_map; 1697 p->swap_map = NULL; 1698 p->flags = 0; 1699 spin_unlock(&swap_lock); 1700 mutex_unlock(&swapon_mutex); 1701 vfree(swap_map); 1702 /* Destroy swap account informatin */ 1703 swap_cgroup_swapoff(type); 1704 1705 inode = mapping->host; 1706 if (S_ISBLK(inode->i_mode)) { 1707 struct block_device *bdev = I_BDEV(inode); 1708 set_blocksize(bdev, p->old_block_size); 1709 bd_release(bdev); 1710 } else { 1711 mutex_lock(&inode->i_mutex); 1712 inode->i_flags &= ~S_SWAPFILE; 1713 mutex_unlock(&inode->i_mutex); 1714 } 1715 filp_close(swap_file, NULL); 1716 err = 0; 1717 1718out_dput: 1719 filp_close(victim, NULL); 1720out: 1721 return err; 1722} 1723 1724#ifdef CONFIG_PROC_FS 1725/* iterator */ 1726static void *swap_start(struct seq_file *swap, loff_t *pos) 1727{ 1728 struct swap_info_struct *si; 1729 int type; 1730 loff_t l = *pos; 1731 1732 mutex_lock(&swapon_mutex); 1733 1734 if (!l) 1735 return SEQ_START_TOKEN; 1736 1737 for (type = 0; type < nr_swapfiles; type++) { 1738 smp_rmb(); /* read nr_swapfiles before swap_info[type] */ 1739 si = swap_info[type]; 1740 if (!(si->flags & SWP_USED) || !si->swap_map) 1741 continue; 1742 if (!--l) 1743 return si; 1744 } 1745 1746 return NULL; 1747} 1748 1749static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) 1750{ 1751 struct swap_info_struct *si = v; 1752 int type; 1753 1754 if (v == SEQ_START_TOKEN) 1755 type = 0; 1756 else 1757 type = si->type + 1; 1758 1759 for (; type < nr_swapfiles; type++) { 1760 smp_rmb(); /* read nr_swapfiles before swap_info[type] */ 1761 si = swap_info[type]; 1762 if (!(si->flags & SWP_USED) || !si->swap_map) 1763 continue; 1764 ++*pos; 1765 return si; 1766 } 1767 1768 return NULL; 1769} 1770 1771static void swap_stop(struct seq_file *swap, void *v) 1772{ 1773 mutex_unlock(&swapon_mutex); 1774} 1775 1776static int swap_show(struct seq_file *swap, void *v) 1777{ 1778 struct swap_info_struct *si = v; 1779 struct file *file; 1780 int len; 1781 1782 if (si == SEQ_START_TOKEN) { 1783 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); 1784 return 0; 1785 } 1786 1787 file = si->swap_file; 1788 len = seq_path(swap, &file->f_path, " \t\n\\"); 1789 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n", 1790 len < 40 ? 40 - len : 1, " ", 1791 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ? 1792 "partition" : "file\t", 1793 si->pages << (PAGE_SHIFT - 10), 1794 si->inuse_pages << (PAGE_SHIFT - 10), 1795 si->prio); 1796 return 0; 1797} 1798 1799static const struct seq_operations swaps_op = { 1800 .start = swap_start, 1801 .next = swap_next, 1802 .stop = swap_stop, 1803 .show = swap_show 1804}; 1805 1806static int swaps_open(struct inode *inode, struct file *file) 1807{ 1808 return seq_open(file, &swaps_op); 1809} 1810 1811static const struct file_operations proc_swaps_operations = { 1812 .open = swaps_open, 1813 .read = seq_read, 1814 .llseek = seq_lseek, 1815 .release = seq_release, 1816}; 1817 1818static int __init procswaps_init(void) 1819{ 1820 proc_create("swaps", 0, NULL, &proc_swaps_operations); 1821 return 0; 1822} 1823__initcall(procswaps_init); 1824#endif /* CONFIG_PROC_FS */ 1825 1826#ifdef MAX_SWAPFILES_CHECK 1827static int __init max_swapfiles_check(void) 1828{ 1829 MAX_SWAPFILES_CHECK(); 1830 return 0; 1831} 1832late_initcall(max_swapfiles_check); 1833#endif 1834 1835/* 1836 * Written 01/25/92 by Simmule Turner, heavily changed by Linus. 1837 * 1838 * The swapon system call 1839 */ 1840SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 1841{ 1842 struct swap_info_struct *p; 1843 char *name = NULL; 1844 struct block_device *bdev = NULL; 1845 struct file *swap_file = NULL; 1846 struct address_space *mapping; 1847 unsigned int type; 1848 int i, prev; 1849 int error; 1850 union swap_header *swap_header; 1851 unsigned int nr_good_pages; 1852 int nr_extents = 0; 1853 sector_t span; 1854 unsigned long maxpages; 1855 unsigned long swapfilepages; 1856 unsigned char *swap_map = NULL; 1857 struct page *page = NULL; 1858 struct inode *inode = NULL; 1859 int did_down = 0; 1860 1861 if (!capable(CAP_SYS_ADMIN)) 1862 return -EPERM; 1863 1864 p = kzalloc(sizeof(*p), GFP_KERNEL); 1865 if (!p) 1866 return -ENOMEM; 1867 1868 spin_lock(&swap_lock); 1869 for (type = 0; type < nr_swapfiles; type++) { 1870 if (!(swap_info[type]->flags & SWP_USED)) 1871 break; 1872 } 1873 error = -EPERM; 1874 if (type >= MAX_SWAPFILES) { 1875 spin_unlock(&swap_lock); 1876 kfree(p); 1877 goto out; 1878 } 1879 if (type >= nr_swapfiles) { 1880 p->type = type; 1881 swap_info[type] = p; 1882 /* 1883 * Write swap_info[type] before nr_swapfiles, in case a 1884 * racing procfs swap_start() or swap_next() is reading them. 1885 * (We never shrink nr_swapfiles, we never free this entry.) 1886 */ 1887 smp_wmb(); 1888 nr_swapfiles++; 1889 } else { 1890 kfree(p); 1891 p = swap_info[type]; 1892 /* 1893 * Do not memset this entry: a racing procfs swap_next() 1894 * would be relying on p->type to remain valid. 1895 */ 1896 } 1897 INIT_LIST_HEAD(&p->first_swap_extent.list); 1898 p->flags = SWP_USED; 1899 p->next = -1; 1900 spin_unlock(&swap_lock); 1901 1902 name = getname(specialfile); 1903 error = PTR_ERR(name); 1904 if (IS_ERR(name)) { 1905 name = NULL; 1906 goto bad_swap_2; 1907 } 1908 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0); 1909 error = PTR_ERR(swap_file); 1910 if (IS_ERR(swap_file)) { 1911 swap_file = NULL; 1912 goto bad_swap_2; 1913 } 1914 1915 p->swap_file = swap_file; 1916 mapping = swap_file->f_mapping; 1917 inode = mapping->host; 1918 1919 error = -EBUSY; 1920 for (i = 0; i < nr_swapfiles; i++) { 1921 struct swap_info_struct *q = swap_info[i]; 1922 1923 if (i == type || !q->swap_file) 1924 continue; 1925 if (mapping == q->swap_file->f_mapping) 1926 goto bad_swap; 1927 } 1928 1929 error = -EINVAL; 1930 if (S_ISBLK(inode->i_mode)) { 1931 bdev = I_BDEV(inode); 1932 error = bd_claim(bdev, sys_swapon); 1933 if (error < 0) { 1934 bdev = NULL; 1935 error = -EINVAL; 1936 goto bad_swap; 1937 } 1938 p->old_block_size = block_size(bdev); 1939 error = set_blocksize(bdev, PAGE_SIZE); 1940 if (error < 0) 1941 goto bad_swap; 1942 p->bdev = bdev; 1943 p->flags |= SWP_BLKDEV; 1944 } else if (S_ISREG(inode->i_mode)) { 1945 p->bdev = inode->i_sb->s_bdev; 1946 mutex_lock(&inode->i_mutex); 1947 did_down = 1; 1948 if (IS_SWAPFILE(inode)) { 1949 error = -EBUSY; 1950 goto bad_swap; 1951 } 1952 } else { 1953 goto bad_swap; 1954 } 1955 1956 swapfilepages = i_size_read(inode) >> PAGE_SHIFT; 1957 1958 /* 1959 * Read the swap header. 1960 */ 1961 if (!mapping->a_ops->readpage) { 1962 error = -EINVAL; 1963 goto bad_swap; 1964 } 1965 page = read_mapping_page(mapping, 0, swap_file); 1966 if (IS_ERR(page)) { 1967 error = PTR_ERR(page); 1968 goto bad_swap; 1969 } 1970 swap_header = kmap(page); 1971 1972 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { 1973 printk(KERN_ERR "Unable to find swap-space signature\n"); 1974 error = -EINVAL; 1975 goto bad_swap; 1976 } 1977 1978 /* swap partition endianess hack... */ 1979 if (swab32(swap_header->info.version) == 1) { 1980 swab32s(&swap_header->info.version); 1981 swab32s(&swap_header->info.last_page); 1982 swab32s(&swap_header->info.nr_badpages); 1983 for (i = 0; i < swap_header->info.nr_badpages; i++) 1984 swab32s(&swap_header->info.badpages[i]); 1985 } 1986 /* Check the swap header's sub-version */ 1987 if (swap_header->info.version != 1) { 1988 printk(KERN_WARNING 1989 "Unable to handle swap header version %d\n", 1990 swap_header->info.version); 1991 error = -EINVAL; 1992 goto bad_swap; 1993 } 1994 1995 p->lowest_bit = 1; 1996 p->cluster_next = 1; 1997 p->cluster_nr = 0; 1998 1999 /* 2000 * Find out how many pages are allowed for a single swap 2001 * device. There are two limiting factors: 1) the number of 2002 * bits for the swap offset in the swp_entry_t type and 2003 * 2) the number of bits in the a swap pte as defined by 2004 * the different architectures. In order to find the 2005 * largest possible bit mask a swap entry with swap type 0 2006 * and swap offset ~0UL is created, encoded to a swap pte, 2007 * decoded to a swp_entry_t again and finally the swap 2008 * offset is extracted. This will mask all the bits from 2009 * the initial ~0UL mask that can't be encoded in either 2010 * the swp_entry_t or the architecture definition of a 2011 * swap pte. 2012 */ 2013 maxpages = swp_offset(pte_to_swp_entry( 2014 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; 2015 if (maxpages > swap_header->info.last_page) { 2016 maxpages = swap_header->info.last_page + 1; 2017 /* p->max is an unsigned int: don't overflow it */ 2018 if ((unsigned int)maxpages == 0) 2019 maxpages = UINT_MAX; 2020 } 2021 p->highest_bit = maxpages - 1; 2022 2023 error = -EINVAL; 2024 if (!maxpages) 2025 goto bad_swap; 2026 if (swapfilepages && maxpages > swapfilepages) { 2027 printk(KERN_WARNING 2028 "Swap area shorter than signature indicates\n"); 2029 goto bad_swap; 2030 } 2031 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) 2032 goto bad_swap; 2033 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) 2034 goto bad_swap; 2035 2036 /* OK, set up the swap map and apply the bad block list */ 2037 swap_map = vmalloc(maxpages); 2038 if (!swap_map) { 2039 error = -ENOMEM; 2040 goto bad_swap; 2041 } 2042 2043 memset(swap_map, 0, maxpages); 2044 nr_good_pages = maxpages - 1; /* omit header page */ 2045 2046 for (i = 0; i < swap_header->info.nr_badpages; i++) { 2047 unsigned int page_nr = swap_header->info.badpages[i]; 2048 if (page_nr == 0 || page_nr > swap_header->info.last_page) { 2049 error = -EINVAL; 2050 goto bad_swap; 2051 } 2052 if (page_nr < maxpages) { 2053 swap_map[page_nr] = SWAP_MAP_BAD; 2054 nr_good_pages--; 2055 } 2056 } 2057 2058 error = swap_cgroup_swapon(type, maxpages); 2059 if (error) 2060 goto bad_swap; 2061 2062 if (nr_good_pages) { 2063 swap_map[0] = SWAP_MAP_BAD; 2064 p->max = maxpages; 2065 p->pages = nr_good_pages; 2066 nr_extents = setup_swap_extents(p, &span); 2067 if (nr_extents < 0) { 2068 error = nr_extents; 2069 goto bad_swap; 2070 } 2071 nr_good_pages = p->pages; 2072 } 2073 if (!nr_good_pages) { 2074 printk(KERN_WARNING "Empty swap-file\n"); 2075 error = -EINVAL; 2076 goto bad_swap; 2077 } 2078 2079 if (p->bdev) { 2080 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { 2081 p->flags |= SWP_SOLIDSTATE; 2082 p->cluster_next = 1 + (random32() % p->highest_bit); 2083 } 2084 if (discard_swap(p) == 0) 2085 p->flags |= SWP_DISCARDABLE; 2086 } 2087 2088 mutex_lock(&swapon_mutex); 2089 spin_lock(&swap_lock); 2090 if (swap_flags & SWAP_FLAG_PREFER) 2091 p->prio = 2092 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; 2093 else 2094 p->prio = --least_priority; 2095 p->swap_map = swap_map; 2096 p->flags |= SWP_WRITEOK; 2097 nr_swap_pages += nr_good_pages; 2098 total_swap_pages += nr_good_pages; 2099 2100 printk(KERN_INFO "Adding %uk swap on %s. " 2101 "Priority:%d extents:%d across:%lluk %s%s\n", 2102 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio, 2103 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10), 2104 (p->flags & SWP_SOLIDSTATE) ? "SS" : "", 2105 (p->flags & SWP_DISCARDABLE) ? "D" : ""); 2106 2107 /* insert swap space into swap_list: */ 2108 prev = -1; 2109 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { 2110 if (p->prio >= swap_info[i]->prio) 2111 break; 2112 prev = i; 2113 } 2114 p->next = i; 2115 if (prev < 0) 2116 swap_list.head = swap_list.next = type; 2117 else 2118 swap_info[prev]->next = type; 2119 spin_unlock(&swap_lock); 2120 mutex_unlock(&swapon_mutex); 2121 error = 0; 2122 goto out; 2123bad_swap: 2124 if (bdev) { 2125 set_blocksize(bdev, p->old_block_size); 2126 bd_release(bdev); 2127 } 2128 destroy_swap_extents(p); 2129 swap_cgroup_swapoff(type); 2130bad_swap_2: 2131 spin_lock(&swap_lock); 2132 p->swap_file = NULL; 2133 p->flags = 0; 2134 spin_unlock(&swap_lock); 2135 vfree(swap_map); 2136 if (swap_file) 2137 filp_close(swap_file, NULL); 2138out: 2139 if (page && !IS_ERR(page)) { 2140 kunmap(page); 2141 page_cache_release(page); 2142 } 2143 if (name) 2144 putname(name); 2145 if (did_down) { 2146 if (!error) 2147 inode->i_flags |= S_SWAPFILE; 2148 mutex_unlock(&inode->i_mutex); 2149 } 2150 return error; 2151} 2152 2153void si_swapinfo(struct sysinfo *val) 2154{ 2155 unsigned int type; 2156 unsigned long nr_to_be_unused = 0; 2157 2158 spin_lock(&swap_lock); 2159 for (type = 0; type < nr_swapfiles; type++) { 2160 struct swap_info_struct *si = swap_info[type]; 2161 2162 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) 2163 nr_to_be_unused += si->inuse_pages; 2164 } 2165 val->freeswap = nr_swap_pages + nr_to_be_unused; 2166 val->totalswap = total_swap_pages + nr_to_be_unused; 2167 spin_unlock(&swap_lock); 2168} 2169 2170/* 2171 * Verify that a swap entry is valid and increment its swap map count. 2172 * 2173 * Returns error code in following case. 2174 * - success -> 0 2175 * - swp_entry is invalid -> EINVAL 2176 * - swp_entry is migration entry -> EINVAL 2177 * - swap-cache reference is requested but there is already one. -> EEXIST 2178 * - swap-cache reference is requested but the entry is not used. -> ENOENT 2179 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM 2180 */ 2181static int __swap_duplicate(swp_entry_t entry, unsigned char usage) 2182{ 2183 struct swap_info_struct *p; 2184 unsigned long offset, type; 2185 unsigned char count; 2186 unsigned char has_cache; 2187 int err = -EINVAL; 2188 2189 if (non_swap_entry(entry)) 2190 goto out; 2191 2192 type = swp_type(entry); 2193 if (type >= nr_swapfiles) 2194 goto bad_file; 2195 p = swap_info[type]; 2196 offset = swp_offset(entry); 2197 2198 spin_lock(&swap_lock); 2199 if (unlikely(offset >= p->max)) 2200 goto unlock_out; 2201 2202 count = p->swap_map[offset]; 2203 has_cache = count & SWAP_HAS_CACHE; 2204 count &= ~SWAP_HAS_CACHE; 2205 err = 0; 2206 2207 if (usage == SWAP_HAS_CACHE) { 2208 2209 /* set SWAP_HAS_CACHE if there is no cache and entry is used */ 2210 if (!has_cache && count) 2211 has_cache = SWAP_HAS_CACHE; 2212 else if (has_cache) /* someone else added cache */ 2213 err = -EEXIST; 2214 else /* no users remaining */ 2215 err = -ENOENT; 2216 2217 } else if (count || has_cache) { 2218 2219 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) 2220 count += usage; 2221 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) 2222 err = -EINVAL; 2223 else if (swap_count_continued(p, offset, count)) 2224 count = COUNT_CONTINUED; 2225 else 2226 err = -ENOMEM; 2227 } else 2228 err = -ENOENT; /* unused swap entry */ 2229 2230 p->swap_map[offset] = count | has_cache; 2231 2232unlock_out: 2233 spin_unlock(&swap_lock); 2234out: 2235 return err; 2236 2237bad_file: 2238 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); 2239 goto out; 2240} 2241 2242/* 2243 * Help swapoff by noting that swap entry belongs to shmem/tmpfs 2244 * (in which case its reference count is never incremented). 2245 */ 2246void swap_shmem_alloc(swp_entry_t entry) 2247{ 2248 __swap_duplicate(entry, SWAP_MAP_SHMEM); 2249} 2250 2251/* 2252 * Increase reference count of swap entry by 1. 2253 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required 2254 * but could not be atomically allocated. Returns 0, just as if it succeeded, 2255 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which 2256 * might occur if a page table entry has got corrupted. 2257 */ 2258int swap_duplicate(swp_entry_t entry) 2259{ 2260 int err = 0; 2261 2262 while (!err && __swap_duplicate(entry, 1) == -ENOMEM) 2263 err = add_swap_count_continuation(entry, GFP_ATOMIC); 2264 return err; 2265} 2266 2267/* 2268 * @entry: swap entry for which we allocate swap cache. 2269 * 2270 * Called when allocating swap cache for existing swap entry, 2271 * This can return error codes. Returns 0 at success. 2272 * -EBUSY means there is a swap cache. 2273 * Note: return code is different from swap_duplicate(). 2274 */ 2275int swapcache_prepare(swp_entry_t entry) 2276{ 2277 return __swap_duplicate(entry, SWAP_HAS_CACHE); 2278} 2279 2280/* 2281 * swap_lock prevents swap_map being freed. Don't grab an extra 2282 * reference on the swaphandle, it doesn't matter if it becomes unused. 2283 */ 2284int valid_swaphandles(swp_entry_t entry, unsigned long *offset) 2285{ 2286 struct swap_info_struct *si; 2287 int our_page_cluster = page_cluster; 2288 pgoff_t target, toff; 2289 pgoff_t base, end; 2290 int nr_pages = 0; 2291 2292 if (!our_page_cluster) /* no readahead */ 2293 return 0; 2294 2295 si = swap_info[swp_type(entry)]; 2296 target = swp_offset(entry); 2297 base = (target >> our_page_cluster) << our_page_cluster; 2298 end = base + (1 << our_page_cluster); 2299 if (!base) /* first page is swap header */ 2300 base++; 2301 2302 spin_lock(&swap_lock); 2303 if (end > si->max) /* don't go beyond end of map */ 2304 end = si->max; 2305 2306 /* Count contiguous allocated slots above our target */ 2307 for (toff = target; ++toff < end; nr_pages++) { 2308 /* Don't read in free or bad pages */ 2309 if (!si->swap_map[toff]) 2310 break; 2311 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) 2312 break; 2313 } 2314 /* Count contiguous allocated slots below our target */ 2315 for (toff = target; --toff >= base; nr_pages++) { 2316 /* Don't read in free or bad pages */ 2317 if (!si->swap_map[toff]) 2318 break; 2319 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) 2320 break; 2321 } 2322 spin_unlock(&swap_lock); 2323 2324 /* 2325 * Indicate starting offset, and return number of pages to get: 2326 * if only 1, say 0, since there's then no readahead to be done. 2327 */ 2328 *offset = ++toff; 2329 return nr_pages? ++nr_pages: 0; 2330} 2331 2332/* 2333 * add_swap_count_continuation - called when a swap count is duplicated 2334 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's 2335 * page of the original vmalloc'ed swap_map, to hold the continuation count 2336 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called 2337 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc. 2338 * 2339 * These continuation pages are seldom referenced: the common paths all work 2340 * on the original swap_map, only referring to a continuation page when the 2341 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX. 2342 * 2343 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding 2344 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL) 2345 * can be called after dropping locks. 2346 */ 2347int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask) 2348{ 2349 struct swap_info_struct *si; 2350 struct page *head; 2351 struct page *page; 2352 struct page *list_page; 2353 pgoff_t offset; 2354 unsigned char count; 2355 2356 /* 2357 * When debugging, it's easier to use __GFP_ZERO here; but it's better 2358 * for latency not to zero a page while GFP_ATOMIC and holding locks. 2359 */ 2360 page = alloc_page(gfp_mask | __GFP_HIGHMEM); 2361 2362 si = swap_info_get(entry); 2363 if (!si) { 2364 /* 2365 * An acceptable race has occurred since the failing 2366 * __swap_duplicate(): the swap entry has been freed, 2367 * perhaps even the whole swap_map cleared for swapoff. 2368 */ 2369 goto outer; 2370 } 2371 2372 offset = swp_offset(entry); 2373 count = si->swap_map[offset] & ~SWAP_HAS_CACHE; 2374 2375 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) { 2376 /* 2377 * The higher the swap count, the more likely it is that tasks 2378 * will race to add swap count continuation: we need to avoid 2379 * over-provisioning. 2380 */ 2381 goto out; 2382 } 2383 2384 if (!page) { 2385 spin_unlock(&swap_lock); 2386 return -ENOMEM; 2387 } 2388 2389 /* 2390 * We are fortunate that although vmalloc_to_page uses pte_offset_map, 2391 * no architecture is using highmem pages for kernel pagetables: so it 2392 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps. 2393 */ 2394 head = vmalloc_to_page(si->swap_map + offset); 2395 offset &= ~PAGE_MASK; 2396 2397 /* 2398 * Page allocation does not initialize the page's lru field, 2399 * but it does always reset its private field. 2400 */ 2401 if (!page_private(head)) { 2402 BUG_ON(count & COUNT_CONTINUED); 2403 INIT_LIST_HEAD(&head->lru); 2404 set_page_private(head, SWP_CONTINUED); 2405 si->flags |= SWP_CONTINUED; 2406 } 2407 2408 list_for_each_entry(list_page, &head->lru, lru) { 2409 unsigned char *map; 2410 2411 /* 2412 * If the previous map said no continuation, but we've found 2413 * a continuation page, free our allocation and use this one. 2414 */ 2415 if (!(count & COUNT_CONTINUED)) 2416 goto out; 2417 2418 map = kmap_atomic(list_page, KM_USER0) + offset; 2419 count = *map; 2420 kunmap_atomic(map, KM_USER0); 2421 2422 /* 2423 * If this continuation count now has some space in it, 2424 * free our allocation and use this one. 2425 */ 2426 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX) 2427 goto out; 2428 } 2429 2430 list_add_tail(&page->lru, &head->lru); 2431 page = NULL; /* now it's attached, don't free it */ 2432out: 2433 spin_unlock(&swap_lock); 2434outer: 2435 if (page) 2436 __free_page(page); 2437 return 0; 2438} 2439 2440/* 2441 * swap_count_continued - when the original swap_map count is incremented 2442 * from SWAP_MAP_MAX, check if there is already a continuation page to carry 2443 * into, carry if so, or else fail until a new continuation page is allocated; 2444 * when the original swap_map count is decremented from 0 with continuation, 2445 * borrow from the continuation and report whether it still holds more. 2446 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock. 2447 */ 2448static bool swap_count_continued(struct swap_info_struct *si, 2449 pgoff_t offset, unsigned char count) 2450{ 2451 struct page *head; 2452 struct page *page; 2453 unsigned char *map; 2454 2455 head = vmalloc_to_page(si->swap_map + offset); 2456 if (page_private(head) != SWP_CONTINUED) { 2457 BUG_ON(count & COUNT_CONTINUED); 2458 return false; /* need to add count continuation */ 2459 } 2460 2461 offset &= ~PAGE_MASK; 2462 page = list_entry(head->lru.next, struct page, lru); 2463 map = kmap_atomic(page, KM_USER0) + offset; 2464 2465 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ 2466 goto init_map; /* jump over SWAP_CONT_MAX checks */ 2467 2468 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */ 2469 /* 2470 * Think of how you add 1 to 999 2471 */ 2472 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { 2473 kunmap_atomic(map, KM_USER0); 2474 page = list_entry(page->lru.next, struct page, lru); 2475 BUG_ON(page == head); 2476 map = kmap_atomic(page, KM_USER0) + offset; 2477 } 2478 if (*map == SWAP_CONT_MAX) { 2479 kunmap_atomic(map, KM_USER0); 2480 page = list_entry(page->lru.next, struct page, lru); 2481 if (page == head) 2482 return false; /* add count continuation */ 2483 map = kmap_atomic(page, KM_USER0) + offset; 2484init_map: *map = 0; /* we didn't zero the page */ 2485 } 2486 *map += 1; 2487 kunmap_atomic(map, KM_USER0); 2488 page = list_entry(page->lru.prev, struct page, lru); 2489 while (page != head) { 2490 map = kmap_atomic(page, KM_USER0) + offset; 2491 *map = COUNT_CONTINUED; 2492 kunmap_atomic(map, KM_USER0); 2493 page = list_entry(page->lru.prev, struct page, lru); 2494 } 2495 return true; /* incremented */ 2496 2497 } else { /* decrementing */ 2498 /* 2499 * Think of how you subtract 1 from 1000 2500 */ 2501 BUG_ON(count != COUNT_CONTINUED); 2502 while (*map == COUNT_CONTINUED) { 2503 kunmap_atomic(map, KM_USER0); 2504 page = list_entry(page->lru.next, struct page, lru); 2505 BUG_ON(page == head); 2506 map = kmap_atomic(page, KM_USER0) + offset; 2507 } 2508 BUG_ON(*map == 0); 2509 *map -= 1; 2510 if (*map == 0) 2511 count = 0; 2512 kunmap_atomic(map, KM_USER0); 2513 page = list_entry(page->lru.prev, struct page, lru); 2514 while (page != head) { 2515 map = kmap_atomic(page, KM_USER0) + offset; 2516 *map = SWAP_CONT_MAX | count; 2517 count = COUNT_CONTINUED; 2518 kunmap_atomic(map, KM_USER0); 2519 page = list_entry(page->lru.prev, struct page, lru); 2520 } 2521 return count == COUNT_CONTINUED; 2522 } 2523} 2524 2525/* 2526 * free_swap_count_continuations - swapoff free all the continuation pages 2527 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it. 2528 */ 2529static void free_swap_count_continuations(struct swap_info_struct *si) 2530{ 2531 pgoff_t offset; 2532 2533 for (offset = 0; offset < si->max; offset += PAGE_SIZE) { 2534 struct page *head; 2535 head = vmalloc_to_page(si->swap_map + offset); 2536 if (page_private(head)) { 2537 struct list_head *this, *next; 2538 list_for_each_safe(this, next, &head->lru) { 2539 struct page *page; 2540 page = list_entry(this, struct page, lru); 2541 list_del(this); 2542 __free_page(page); 2543 } 2544 } 2545 } 2546} 2547