swapfile.c revision 253d553ba75ab26b3e9e2f70cbf6fbf0813f7e86
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/rmap.h> 26#include <linux/security.h> 27#include <linux/backing-dev.h> 28#include <linux/mutex.h> 29#include <linux/capability.h> 30#include <linux/syscalls.h> 31#include <linux/memcontrol.h> 32 33#include <asm/pgtable.h> 34#include <asm/tlbflush.h> 35#include <linux/swapops.h> 36#include <linux/page_cgroup.h> 37 38static DEFINE_SPINLOCK(swap_lock); 39static unsigned int nr_swapfiles; 40long nr_swap_pages; 41long total_swap_pages; 42static int swap_overflow; 43static int least_priority; 44 45static const char Bad_file[] = "Bad swap file entry "; 46static const char Unused_file[] = "Unused swap file entry "; 47static const char Bad_offset[] = "Bad swap offset entry "; 48static const char Unused_offset[] = "Unused swap offset entry "; 49 50static struct swap_list_t swap_list = {-1, -1}; 51 52static struct swap_info_struct *swap_info[MAX_SWAPFILES]; 53 54static DEFINE_MUTEX(swapon_mutex); 55 56static inline int swap_count(unsigned short ent) 57{ 58 return ent & ~SWAP_HAS_CACHE; 59} 60 61/* returns 1 if swap entry is freed */ 62static int 63__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset) 64{ 65 swp_entry_t entry = swp_entry(si->type, offset); 66 struct page *page; 67 int ret = 0; 68 69 page = find_get_page(&swapper_space, entry.val); 70 if (!page) 71 return 0; 72 /* 73 * This function is called from scan_swap_map() and it's called 74 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here. 75 * We have to use trylock for avoiding deadlock. This is a special 76 * case and you should use try_to_free_swap() with explicit lock_page() 77 * in usual operations. 78 */ 79 if (trylock_page(page)) { 80 ret = try_to_free_swap(page); 81 unlock_page(page); 82 } 83 page_cache_release(page); 84 return ret; 85} 86 87/* 88 * We need this because the bdev->unplug_fn can sleep and we cannot 89 * hold swap_lock while calling the unplug_fn. And swap_lock 90 * cannot be turned into a mutex. 91 */ 92static DECLARE_RWSEM(swap_unplug_sem); 93 94void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page) 95{ 96 swp_entry_t entry; 97 98 down_read(&swap_unplug_sem); 99 entry.val = page_private(page); 100 if (PageSwapCache(page)) { 101 struct block_device *bdev = swap_info[swp_type(entry)]->bdev; 102 struct backing_dev_info *bdi; 103 104 /* 105 * If the page is removed from swapcache from under us (with a 106 * racy try_to_unuse/swapoff) we need an additional reference 107 * count to avoid reading garbage from page_private(page) above. 108 * If the WARN_ON triggers during a swapoff it maybe the race 109 * condition and it's harmless. However if it triggers without 110 * swapoff it signals a problem. 111 */ 112 WARN_ON(page_count(page) <= 1); 113 114 bdi = bdev->bd_inode->i_mapping->backing_dev_info; 115 blk_run_backing_dev(bdi, page); 116 } 117 up_read(&swap_unplug_sem); 118} 119 120/* 121 * swapon tell device that all the old swap contents can be discarded, 122 * to allow the swap device to optimize its wear-levelling. 123 */ 124static int discard_swap(struct swap_info_struct *si) 125{ 126 struct swap_extent *se; 127 sector_t start_block; 128 sector_t nr_blocks; 129 int err = 0; 130 131 /* Do not discard the swap header page! */ 132 se = &si->first_swap_extent; 133 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9); 134 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9); 135 if (nr_blocks) { 136 err = blkdev_issue_discard(si->bdev, start_block, 137 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER); 138 if (err) 139 return err; 140 cond_resched(); 141 } 142 143 list_for_each_entry(se, &si->first_swap_extent.list, list) { 144 start_block = se->start_block << (PAGE_SHIFT - 9); 145 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9); 146 147 err = blkdev_issue_discard(si->bdev, start_block, 148 nr_blocks, GFP_KERNEL, DISCARD_FL_BARRIER); 149 if (err) 150 break; 151 152 cond_resched(); 153 } 154 return err; /* That will often be -EOPNOTSUPP */ 155} 156 157/* 158 * swap allocation tell device that a cluster of swap can now be discarded, 159 * to allow the swap device to optimize its wear-levelling. 160 */ 161static void discard_swap_cluster(struct swap_info_struct *si, 162 pgoff_t start_page, pgoff_t nr_pages) 163{ 164 struct swap_extent *se = si->curr_swap_extent; 165 int found_extent = 0; 166 167 while (nr_pages) { 168 struct list_head *lh; 169 170 if (se->start_page <= start_page && 171 start_page < se->start_page + se->nr_pages) { 172 pgoff_t offset = start_page - se->start_page; 173 sector_t start_block = se->start_block + offset; 174 sector_t nr_blocks = se->nr_pages - offset; 175 176 if (nr_blocks > nr_pages) 177 nr_blocks = nr_pages; 178 start_page += nr_blocks; 179 nr_pages -= nr_blocks; 180 181 if (!found_extent++) 182 si->curr_swap_extent = se; 183 184 start_block <<= PAGE_SHIFT - 9; 185 nr_blocks <<= PAGE_SHIFT - 9; 186 if (blkdev_issue_discard(si->bdev, start_block, 187 nr_blocks, GFP_NOIO, DISCARD_FL_BARRIER)) 188 break; 189 } 190 191 lh = se->list.next; 192 se = list_entry(lh, struct swap_extent, list); 193 } 194} 195 196static int wait_for_discard(void *word) 197{ 198 schedule(); 199 return 0; 200} 201 202#define SWAPFILE_CLUSTER 256 203#define LATENCY_LIMIT 256 204 205static inline unsigned long scan_swap_map(struct swap_info_struct *si, 206 unsigned short usage) 207{ 208 unsigned long offset; 209 unsigned long scan_base; 210 unsigned long last_in_cluster = 0; 211 int latency_ration = LATENCY_LIMIT; 212 int found_free_cluster = 0; 213 214 /* 215 * We try to cluster swap pages by allocating them sequentially 216 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this 217 * way, however, we resort to first-free allocation, starting 218 * a new cluster. This prevents us from scattering swap pages 219 * all over the entire swap partition, so that we reduce 220 * overall disk seek times between swap pages. -- sct 221 * But we do now try to find an empty cluster. -Andrea 222 * And we let swap pages go all over an SSD partition. Hugh 223 */ 224 225 si->flags += SWP_SCANNING; 226 scan_base = offset = si->cluster_next; 227 228 if (unlikely(!si->cluster_nr--)) { 229 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) { 230 si->cluster_nr = SWAPFILE_CLUSTER - 1; 231 goto checks; 232 } 233 if (si->flags & SWP_DISCARDABLE) { 234 /* 235 * Start range check on racing allocations, in case 236 * they overlap the cluster we eventually decide on 237 * (we scan without swap_lock to allow preemption). 238 * It's hardly conceivable that cluster_nr could be 239 * wrapped during our scan, but don't depend on it. 240 */ 241 if (si->lowest_alloc) 242 goto checks; 243 si->lowest_alloc = si->max; 244 si->highest_alloc = 0; 245 } 246 spin_unlock(&swap_lock); 247 248 /* 249 * If seek is expensive, start searching for new cluster from 250 * start of partition, to minimize the span of allocated swap. 251 * But if seek is cheap, search from our current position, so 252 * that swap is allocated from all over the partition: if the 253 * Flash Translation Layer only remaps within limited zones, 254 * we don't want to wear out the first zone too quickly. 255 */ 256 if (!(si->flags & SWP_SOLIDSTATE)) 257 scan_base = offset = si->lowest_bit; 258 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 259 260 /* Locate the first empty (unaligned) cluster */ 261 for (; last_in_cluster <= si->highest_bit; offset++) { 262 if (si->swap_map[offset]) 263 last_in_cluster = offset + SWAPFILE_CLUSTER; 264 else if (offset == last_in_cluster) { 265 spin_lock(&swap_lock); 266 offset -= SWAPFILE_CLUSTER - 1; 267 si->cluster_next = offset; 268 si->cluster_nr = SWAPFILE_CLUSTER - 1; 269 found_free_cluster = 1; 270 goto checks; 271 } 272 if (unlikely(--latency_ration < 0)) { 273 cond_resched(); 274 latency_ration = LATENCY_LIMIT; 275 } 276 } 277 278 offset = si->lowest_bit; 279 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 280 281 /* Locate the first empty (unaligned) cluster */ 282 for (; last_in_cluster < scan_base; offset++) { 283 if (si->swap_map[offset]) 284 last_in_cluster = offset + SWAPFILE_CLUSTER; 285 else if (offset == last_in_cluster) { 286 spin_lock(&swap_lock); 287 offset -= SWAPFILE_CLUSTER - 1; 288 si->cluster_next = offset; 289 si->cluster_nr = SWAPFILE_CLUSTER - 1; 290 found_free_cluster = 1; 291 goto checks; 292 } 293 if (unlikely(--latency_ration < 0)) { 294 cond_resched(); 295 latency_ration = LATENCY_LIMIT; 296 } 297 } 298 299 offset = scan_base; 300 spin_lock(&swap_lock); 301 si->cluster_nr = SWAPFILE_CLUSTER - 1; 302 si->lowest_alloc = 0; 303 } 304 305checks: 306 if (!(si->flags & SWP_WRITEOK)) 307 goto no_page; 308 if (!si->highest_bit) 309 goto no_page; 310 if (offset > si->highest_bit) 311 scan_base = offset = si->lowest_bit; 312 313 /* reuse swap entry of cache-only swap if not busy. */ 314 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 315 int swap_was_freed; 316 spin_unlock(&swap_lock); 317 swap_was_freed = __try_to_reclaim_swap(si, offset); 318 spin_lock(&swap_lock); 319 /* entry was freed successfully, try to use this again */ 320 if (swap_was_freed) 321 goto checks; 322 goto scan; /* check next one */ 323 } 324 325 if (si->swap_map[offset]) 326 goto scan; 327 328 if (offset == si->lowest_bit) 329 si->lowest_bit++; 330 if (offset == si->highest_bit) 331 si->highest_bit--; 332 si->inuse_pages++; 333 if (si->inuse_pages == si->pages) { 334 si->lowest_bit = si->max; 335 si->highest_bit = 0; 336 } 337 si->swap_map[offset] = usage; 338 si->cluster_next = offset + 1; 339 si->flags -= SWP_SCANNING; 340 341 if (si->lowest_alloc) { 342 /* 343 * Only set when SWP_DISCARDABLE, and there's a scan 344 * for a free cluster in progress or just completed. 345 */ 346 if (found_free_cluster) { 347 /* 348 * To optimize wear-levelling, discard the 349 * old data of the cluster, taking care not to 350 * discard any of its pages that have already 351 * been allocated by racing tasks (offset has 352 * already stepped over any at the beginning). 353 */ 354 if (offset < si->highest_alloc && 355 si->lowest_alloc <= last_in_cluster) 356 last_in_cluster = si->lowest_alloc - 1; 357 si->flags |= SWP_DISCARDING; 358 spin_unlock(&swap_lock); 359 360 if (offset < last_in_cluster) 361 discard_swap_cluster(si, offset, 362 last_in_cluster - offset + 1); 363 364 spin_lock(&swap_lock); 365 si->lowest_alloc = 0; 366 si->flags &= ~SWP_DISCARDING; 367 368 smp_mb(); /* wake_up_bit advises this */ 369 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING)); 370 371 } else if (si->flags & SWP_DISCARDING) { 372 /* 373 * Delay using pages allocated by racing tasks 374 * until the whole discard has been issued. We 375 * could defer that delay until swap_writepage, 376 * but it's easier to keep this self-contained. 377 */ 378 spin_unlock(&swap_lock); 379 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING), 380 wait_for_discard, TASK_UNINTERRUPTIBLE); 381 spin_lock(&swap_lock); 382 } else { 383 /* 384 * Note pages allocated by racing tasks while 385 * scan for a free cluster is in progress, so 386 * that its final discard can exclude them. 387 */ 388 if (offset < si->lowest_alloc) 389 si->lowest_alloc = offset; 390 if (offset > si->highest_alloc) 391 si->highest_alloc = offset; 392 } 393 } 394 return offset; 395 396scan: 397 spin_unlock(&swap_lock); 398 while (++offset <= si->highest_bit) { 399 if (!si->swap_map[offset]) { 400 spin_lock(&swap_lock); 401 goto checks; 402 } 403 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 404 spin_lock(&swap_lock); 405 goto checks; 406 } 407 if (unlikely(--latency_ration < 0)) { 408 cond_resched(); 409 latency_ration = LATENCY_LIMIT; 410 } 411 } 412 offset = si->lowest_bit; 413 while (++offset < scan_base) { 414 if (!si->swap_map[offset]) { 415 spin_lock(&swap_lock); 416 goto checks; 417 } 418 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 419 spin_lock(&swap_lock); 420 goto checks; 421 } 422 if (unlikely(--latency_ration < 0)) { 423 cond_resched(); 424 latency_ration = LATENCY_LIMIT; 425 } 426 } 427 spin_lock(&swap_lock); 428 429no_page: 430 si->flags -= SWP_SCANNING; 431 return 0; 432} 433 434swp_entry_t get_swap_page(void) 435{ 436 struct swap_info_struct *si; 437 pgoff_t offset; 438 int type, next; 439 int wrapped = 0; 440 441 spin_lock(&swap_lock); 442 if (nr_swap_pages <= 0) 443 goto noswap; 444 nr_swap_pages--; 445 446 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { 447 si = swap_info[type]; 448 next = si->next; 449 if (next < 0 || 450 (!wrapped && si->prio != swap_info[next]->prio)) { 451 next = swap_list.head; 452 wrapped++; 453 } 454 455 if (!si->highest_bit) 456 continue; 457 if (!(si->flags & SWP_WRITEOK)) 458 continue; 459 460 swap_list.next = next; 461 /* This is called for allocating swap entry for cache */ 462 offset = scan_swap_map(si, SWAP_HAS_CACHE); 463 if (offset) { 464 spin_unlock(&swap_lock); 465 return swp_entry(type, offset); 466 } 467 next = swap_list.next; 468 } 469 470 nr_swap_pages++; 471noswap: 472 spin_unlock(&swap_lock); 473 return (swp_entry_t) {0}; 474} 475 476/* The only caller of this function is now susupend routine */ 477swp_entry_t get_swap_page_of_type(int type) 478{ 479 struct swap_info_struct *si; 480 pgoff_t offset; 481 482 spin_lock(&swap_lock); 483 si = swap_info[type]; 484 if (si && (si->flags & SWP_WRITEOK)) { 485 nr_swap_pages--; 486 /* This is called for allocating swap entry, not cache */ 487 offset = scan_swap_map(si, 1); 488 if (offset) { 489 spin_unlock(&swap_lock); 490 return swp_entry(type, offset); 491 } 492 nr_swap_pages++; 493 } 494 spin_unlock(&swap_lock); 495 return (swp_entry_t) {0}; 496} 497 498static struct swap_info_struct *swap_info_get(swp_entry_t entry) 499{ 500 struct swap_info_struct *p; 501 unsigned long offset, type; 502 503 if (!entry.val) 504 goto out; 505 type = swp_type(entry); 506 if (type >= nr_swapfiles) 507 goto bad_nofile; 508 p = swap_info[type]; 509 if (!(p->flags & SWP_USED)) 510 goto bad_device; 511 offset = swp_offset(entry); 512 if (offset >= p->max) 513 goto bad_offset; 514 if (!p->swap_map[offset]) 515 goto bad_free; 516 spin_lock(&swap_lock); 517 return p; 518 519bad_free: 520 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val); 521 goto out; 522bad_offset: 523 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val); 524 goto out; 525bad_device: 526 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val); 527 goto out; 528bad_nofile: 529 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val); 530out: 531 return NULL; 532} 533 534static unsigned short swap_entry_free(struct swap_info_struct *p, 535 swp_entry_t entry, unsigned short usage) 536{ 537 unsigned long offset = swp_offset(entry); 538 unsigned short count; 539 unsigned short has_cache; 540 541 count = p->swap_map[offset]; 542 has_cache = count & SWAP_HAS_CACHE; 543 count &= ~SWAP_HAS_CACHE; 544 545 if (usage == SWAP_HAS_CACHE) { 546 VM_BUG_ON(!has_cache); 547 has_cache = 0; 548 } else if (count < SWAP_MAP_MAX) 549 count--; 550 551 if (!count) 552 mem_cgroup_uncharge_swap(entry); 553 554 usage = count | has_cache; 555 p->swap_map[offset] = usage; 556 557 /* free if no reference */ 558 if (!usage) { 559 if (offset < p->lowest_bit) 560 p->lowest_bit = offset; 561 if (offset > p->highest_bit) 562 p->highest_bit = offset; 563 if (swap_list.next >= 0 && 564 p->prio > swap_info[swap_list.next]->prio) 565 swap_list.next = p->type; 566 nr_swap_pages++; 567 p->inuse_pages--; 568 } 569 570 return usage; 571} 572 573/* 574 * Caller has made sure that the swapdevice corresponding to entry 575 * is still around or has not been recycled. 576 */ 577void swap_free(swp_entry_t entry) 578{ 579 struct swap_info_struct *p; 580 581 p = swap_info_get(entry); 582 if (p) { 583 swap_entry_free(p, entry, 1); 584 spin_unlock(&swap_lock); 585 } 586} 587 588/* 589 * Called after dropping swapcache to decrease refcnt to swap entries. 590 */ 591void swapcache_free(swp_entry_t entry, struct page *page) 592{ 593 struct swap_info_struct *p; 594 unsigned short count; 595 596 p = swap_info_get(entry); 597 if (p) { 598 count = swap_entry_free(p, entry, SWAP_HAS_CACHE); 599 if (page) 600 mem_cgroup_uncharge_swapcache(page, entry, count != 0); 601 spin_unlock(&swap_lock); 602 } 603} 604 605/* 606 * How many references to page are currently swapped out? 607 */ 608static inline int page_swapcount(struct page *page) 609{ 610 int count = 0; 611 struct swap_info_struct *p; 612 swp_entry_t entry; 613 614 entry.val = page_private(page); 615 p = swap_info_get(entry); 616 if (p) { 617 count = swap_count(p->swap_map[swp_offset(entry)]); 618 spin_unlock(&swap_lock); 619 } 620 return count; 621} 622 623/* 624 * We can write to an anon page without COW if there are no other references 625 * to it. And as a side-effect, free up its swap: because the old content 626 * on disk will never be read, and seeking back there to write new content 627 * later would only waste time away from clustering. 628 */ 629int reuse_swap_page(struct page *page) 630{ 631 int count; 632 633 VM_BUG_ON(!PageLocked(page)); 634 count = page_mapcount(page); 635 if (count <= 1 && PageSwapCache(page)) { 636 count += page_swapcount(page); 637 if (count == 1 && !PageWriteback(page)) { 638 delete_from_swap_cache(page); 639 SetPageDirty(page); 640 } 641 } 642 return count == 1; 643} 644 645/* 646 * If swap is getting full, or if there are no more mappings of this page, 647 * then try_to_free_swap is called to free its swap space. 648 */ 649int try_to_free_swap(struct page *page) 650{ 651 VM_BUG_ON(!PageLocked(page)); 652 653 if (!PageSwapCache(page)) 654 return 0; 655 if (PageWriteback(page)) 656 return 0; 657 if (page_swapcount(page)) 658 return 0; 659 660 delete_from_swap_cache(page); 661 SetPageDirty(page); 662 return 1; 663} 664 665/* 666 * Free the swap entry like above, but also try to 667 * free the page cache entry if it is the last user. 668 */ 669int free_swap_and_cache(swp_entry_t entry) 670{ 671 struct swap_info_struct *p; 672 struct page *page = NULL; 673 674 if (non_swap_entry(entry)) 675 return 1; 676 677 p = swap_info_get(entry); 678 if (p) { 679 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) { 680 page = find_get_page(&swapper_space, entry.val); 681 if (page && !trylock_page(page)) { 682 page_cache_release(page); 683 page = NULL; 684 } 685 } 686 spin_unlock(&swap_lock); 687 } 688 if (page) { 689 /* 690 * Not mapped elsewhere, or swap space full? Free it! 691 * Also recheck PageSwapCache now page is locked (above). 692 */ 693 if (PageSwapCache(page) && !PageWriteback(page) && 694 (!page_mapped(page) || vm_swap_full())) { 695 delete_from_swap_cache(page); 696 SetPageDirty(page); 697 } 698 unlock_page(page); 699 page_cache_release(page); 700 } 701 return p != NULL; 702} 703 704#ifdef CONFIG_HIBERNATION 705/* 706 * Find the swap type that corresponds to given device (if any). 707 * 708 * @offset - number of the PAGE_SIZE-sized block of the device, starting 709 * from 0, in which the swap header is expected to be located. 710 * 711 * This is needed for the suspend to disk (aka swsusp). 712 */ 713int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p) 714{ 715 struct block_device *bdev = NULL; 716 int type; 717 718 if (device) 719 bdev = bdget(device); 720 721 spin_lock(&swap_lock); 722 for (type = 0; type < nr_swapfiles; type++) { 723 struct swap_info_struct *sis = swap_info[type]; 724 725 if (!(sis->flags & SWP_WRITEOK)) 726 continue; 727 728 if (!bdev) { 729 if (bdev_p) 730 *bdev_p = bdgrab(sis->bdev); 731 732 spin_unlock(&swap_lock); 733 return type; 734 } 735 if (bdev == sis->bdev) { 736 struct swap_extent *se = &sis->first_swap_extent; 737 738 if (se->start_block == offset) { 739 if (bdev_p) 740 *bdev_p = bdgrab(sis->bdev); 741 742 spin_unlock(&swap_lock); 743 bdput(bdev); 744 return type; 745 } 746 } 747 } 748 spin_unlock(&swap_lock); 749 if (bdev) 750 bdput(bdev); 751 752 return -ENODEV; 753} 754 755/* 756 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev 757 * corresponding to given index in swap_info (swap type). 758 */ 759sector_t swapdev_block(int type, pgoff_t offset) 760{ 761 struct block_device *bdev; 762 763 if ((unsigned int)type >= nr_swapfiles) 764 return 0; 765 if (!(swap_info[type]->flags & SWP_WRITEOK)) 766 return 0; 767 return map_swap_page(swp_entry(type, offset), &bdev); 768} 769 770/* 771 * Return either the total number of swap pages of given type, or the number 772 * of free pages of that type (depending on @free) 773 * 774 * This is needed for software suspend 775 */ 776unsigned int count_swap_pages(int type, int free) 777{ 778 unsigned int n = 0; 779 780 spin_lock(&swap_lock); 781 if ((unsigned int)type < nr_swapfiles) { 782 struct swap_info_struct *sis = swap_info[type]; 783 784 if (sis->flags & SWP_WRITEOK) { 785 n = sis->pages; 786 if (free) 787 n -= sis->inuse_pages; 788 } 789 } 790 spin_unlock(&swap_lock); 791 return n; 792} 793#endif /* CONFIG_HIBERNATION */ 794 795/* 796 * No need to decide whether this PTE shares the swap entry with others, 797 * just let do_wp_page work it out if a write is requested later - to 798 * force COW, vm_page_prot omits write permission from any private vma. 799 */ 800static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, 801 unsigned long addr, swp_entry_t entry, struct page *page) 802{ 803 struct mem_cgroup *ptr = NULL; 804 spinlock_t *ptl; 805 pte_t *pte; 806 int ret = 1; 807 808 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) { 809 ret = -ENOMEM; 810 goto out_nolock; 811 } 812 813 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 814 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) { 815 if (ret > 0) 816 mem_cgroup_cancel_charge_swapin(ptr); 817 ret = 0; 818 goto out; 819 } 820 821 inc_mm_counter(vma->vm_mm, anon_rss); 822 get_page(page); 823 set_pte_at(vma->vm_mm, addr, pte, 824 pte_mkold(mk_pte(page, vma->vm_page_prot))); 825 page_add_anon_rmap(page, vma, addr); 826 mem_cgroup_commit_charge_swapin(page, ptr); 827 swap_free(entry); 828 /* 829 * Move the page to the active list so it is not 830 * immediately swapped out again after swapon. 831 */ 832 activate_page(page); 833out: 834 pte_unmap_unlock(pte, ptl); 835out_nolock: 836 return ret; 837} 838 839static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 840 unsigned long addr, unsigned long end, 841 swp_entry_t entry, struct page *page) 842{ 843 pte_t swp_pte = swp_entry_to_pte(entry); 844 pte_t *pte; 845 int ret = 0; 846 847 /* 848 * We don't actually need pte lock while scanning for swp_pte: since 849 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the 850 * page table while we're scanning; though it could get zapped, and on 851 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse 852 * of unmatched parts which look like swp_pte, so unuse_pte must 853 * recheck under pte lock. Scanning without pte lock lets it be 854 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE. 855 */ 856 pte = pte_offset_map(pmd, addr); 857 do { 858 /* 859 * swapoff spends a _lot_ of time in this loop! 860 * Test inline before going to call unuse_pte. 861 */ 862 if (unlikely(pte_same(*pte, swp_pte))) { 863 pte_unmap(pte); 864 ret = unuse_pte(vma, pmd, addr, entry, page); 865 if (ret) 866 goto out; 867 pte = pte_offset_map(pmd, addr); 868 } 869 } while (pte++, addr += PAGE_SIZE, addr != end); 870 pte_unmap(pte - 1); 871out: 872 return ret; 873} 874 875static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, 876 unsigned long addr, unsigned long end, 877 swp_entry_t entry, struct page *page) 878{ 879 pmd_t *pmd; 880 unsigned long next; 881 int ret; 882 883 pmd = pmd_offset(pud, addr); 884 do { 885 next = pmd_addr_end(addr, end); 886 if (pmd_none_or_clear_bad(pmd)) 887 continue; 888 ret = unuse_pte_range(vma, pmd, addr, next, entry, page); 889 if (ret) 890 return ret; 891 } while (pmd++, addr = next, addr != end); 892 return 0; 893} 894 895static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd, 896 unsigned long addr, unsigned long end, 897 swp_entry_t entry, struct page *page) 898{ 899 pud_t *pud; 900 unsigned long next; 901 int ret; 902 903 pud = pud_offset(pgd, addr); 904 do { 905 next = pud_addr_end(addr, end); 906 if (pud_none_or_clear_bad(pud)) 907 continue; 908 ret = unuse_pmd_range(vma, pud, addr, next, entry, page); 909 if (ret) 910 return ret; 911 } while (pud++, addr = next, addr != end); 912 return 0; 913} 914 915static int unuse_vma(struct vm_area_struct *vma, 916 swp_entry_t entry, struct page *page) 917{ 918 pgd_t *pgd; 919 unsigned long addr, end, next; 920 int ret; 921 922 if (page->mapping) { 923 addr = page_address_in_vma(page, vma); 924 if (addr == -EFAULT) 925 return 0; 926 else 927 end = addr + PAGE_SIZE; 928 } else { 929 addr = vma->vm_start; 930 end = vma->vm_end; 931 } 932 933 pgd = pgd_offset(vma->vm_mm, addr); 934 do { 935 next = pgd_addr_end(addr, end); 936 if (pgd_none_or_clear_bad(pgd)) 937 continue; 938 ret = unuse_pud_range(vma, pgd, addr, next, entry, page); 939 if (ret) 940 return ret; 941 } while (pgd++, addr = next, addr != end); 942 return 0; 943} 944 945static int unuse_mm(struct mm_struct *mm, 946 swp_entry_t entry, struct page *page) 947{ 948 struct vm_area_struct *vma; 949 int ret = 0; 950 951 if (!down_read_trylock(&mm->mmap_sem)) { 952 /* 953 * Activate page so shrink_inactive_list is unlikely to unmap 954 * its ptes while lock is dropped, so swapoff can make progress. 955 */ 956 activate_page(page); 957 unlock_page(page); 958 down_read(&mm->mmap_sem); 959 lock_page(page); 960 } 961 for (vma = mm->mmap; vma; vma = vma->vm_next) { 962 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page))) 963 break; 964 } 965 up_read(&mm->mmap_sem); 966 return (ret < 0)? ret: 0; 967} 968 969/* 970 * Scan swap_map from current position to next entry still in use. 971 * Recycle to start on reaching the end, returning 0 when empty. 972 */ 973static unsigned int find_next_to_unuse(struct swap_info_struct *si, 974 unsigned int prev) 975{ 976 unsigned int max = si->max; 977 unsigned int i = prev; 978 int count; 979 980 /* 981 * No need for swap_lock here: we're just looking 982 * for whether an entry is in use, not modifying it; false 983 * hits are okay, and sys_swapoff() has already prevented new 984 * allocations from this area (while holding swap_lock). 985 */ 986 for (;;) { 987 if (++i >= max) { 988 if (!prev) { 989 i = 0; 990 break; 991 } 992 /* 993 * No entries in use at top of swap_map, 994 * loop back to start and recheck there. 995 */ 996 max = prev + 1; 997 prev = 0; 998 i = 1; 999 } 1000 count = si->swap_map[i]; 1001 if (count && swap_count(count) != SWAP_MAP_BAD) 1002 break; 1003 } 1004 return i; 1005} 1006 1007/* 1008 * We completely avoid races by reading each swap page in advance, 1009 * and then search for the process using it. All the necessary 1010 * page table adjustments can then be made atomically. 1011 */ 1012static int try_to_unuse(unsigned int type) 1013{ 1014 struct swap_info_struct *si = swap_info[type]; 1015 struct mm_struct *start_mm; 1016 unsigned short *swap_map; 1017 unsigned short swcount; 1018 struct page *page; 1019 swp_entry_t entry; 1020 unsigned int i = 0; 1021 int retval = 0; 1022 int reset_overflow = 0; 1023 int shmem; 1024 1025 /* 1026 * When searching mms for an entry, a good strategy is to 1027 * start at the first mm we freed the previous entry from 1028 * (though actually we don't notice whether we or coincidence 1029 * freed the entry). Initialize this start_mm with a hold. 1030 * 1031 * A simpler strategy would be to start at the last mm we 1032 * freed the previous entry from; but that would take less 1033 * advantage of mmlist ordering, which clusters forked mms 1034 * together, child after parent. If we race with dup_mmap(), we 1035 * prefer to resolve parent before child, lest we miss entries 1036 * duplicated after we scanned child: using last mm would invert 1037 * that. Though it's only a serious concern when an overflowed 1038 * swap count is reset from SWAP_MAP_MAX, preventing a rescan. 1039 */ 1040 start_mm = &init_mm; 1041 atomic_inc(&init_mm.mm_users); 1042 1043 /* 1044 * Keep on scanning until all entries have gone. Usually, 1045 * one pass through swap_map is enough, but not necessarily: 1046 * there are races when an instance of an entry might be missed. 1047 */ 1048 while ((i = find_next_to_unuse(si, i)) != 0) { 1049 if (signal_pending(current)) { 1050 retval = -EINTR; 1051 break; 1052 } 1053 1054 /* 1055 * Get a page for the entry, using the existing swap 1056 * cache page if there is one. Otherwise, get a clean 1057 * page and read the swap into it. 1058 */ 1059 swap_map = &si->swap_map[i]; 1060 entry = swp_entry(type, i); 1061 page = read_swap_cache_async(entry, 1062 GFP_HIGHUSER_MOVABLE, NULL, 0); 1063 if (!page) { 1064 /* 1065 * Either swap_duplicate() failed because entry 1066 * has been freed independently, and will not be 1067 * reused since sys_swapoff() already disabled 1068 * allocation from here, or alloc_page() failed. 1069 */ 1070 if (!*swap_map) 1071 continue; 1072 retval = -ENOMEM; 1073 break; 1074 } 1075 1076 /* 1077 * Don't hold on to start_mm if it looks like exiting. 1078 */ 1079 if (atomic_read(&start_mm->mm_users) == 1) { 1080 mmput(start_mm); 1081 start_mm = &init_mm; 1082 atomic_inc(&init_mm.mm_users); 1083 } 1084 1085 /* 1086 * Wait for and lock page. When do_swap_page races with 1087 * try_to_unuse, do_swap_page can handle the fault much 1088 * faster than try_to_unuse can locate the entry. This 1089 * apparently redundant "wait_on_page_locked" lets try_to_unuse 1090 * defer to do_swap_page in such a case - in some tests, 1091 * do_swap_page and try_to_unuse repeatedly compete. 1092 */ 1093 wait_on_page_locked(page); 1094 wait_on_page_writeback(page); 1095 lock_page(page); 1096 wait_on_page_writeback(page); 1097 1098 /* 1099 * Remove all references to entry. 1100 * Whenever we reach init_mm, there's no address space 1101 * to search, but use it as a reminder to search shmem. 1102 */ 1103 shmem = 0; 1104 swcount = *swap_map; 1105 if (swap_count(swcount)) { 1106 if (start_mm == &init_mm) 1107 shmem = shmem_unuse(entry, page); 1108 else 1109 retval = unuse_mm(start_mm, entry, page); 1110 } 1111 if (swap_count(*swap_map)) { 1112 int set_start_mm = (*swap_map >= swcount); 1113 struct list_head *p = &start_mm->mmlist; 1114 struct mm_struct *new_start_mm = start_mm; 1115 struct mm_struct *prev_mm = start_mm; 1116 struct mm_struct *mm; 1117 1118 atomic_inc(&new_start_mm->mm_users); 1119 atomic_inc(&prev_mm->mm_users); 1120 spin_lock(&mmlist_lock); 1121 while (swap_count(*swap_map) && !retval && !shmem && 1122 (p = p->next) != &start_mm->mmlist) { 1123 mm = list_entry(p, struct mm_struct, mmlist); 1124 if (!atomic_inc_not_zero(&mm->mm_users)) 1125 continue; 1126 spin_unlock(&mmlist_lock); 1127 mmput(prev_mm); 1128 prev_mm = mm; 1129 1130 cond_resched(); 1131 1132 swcount = *swap_map; 1133 if (!swap_count(swcount)) /* any usage ? */ 1134 ; 1135 else if (mm == &init_mm) { 1136 set_start_mm = 1; 1137 shmem = shmem_unuse(entry, page); 1138 } else 1139 retval = unuse_mm(mm, entry, page); 1140 1141 if (set_start_mm && *swap_map < swcount) { 1142 mmput(new_start_mm); 1143 atomic_inc(&mm->mm_users); 1144 new_start_mm = mm; 1145 set_start_mm = 0; 1146 } 1147 spin_lock(&mmlist_lock); 1148 } 1149 spin_unlock(&mmlist_lock); 1150 mmput(prev_mm); 1151 mmput(start_mm); 1152 start_mm = new_start_mm; 1153 } 1154 if (shmem) { 1155 /* page has already been unlocked and released */ 1156 if (shmem > 0) 1157 continue; 1158 retval = shmem; 1159 break; 1160 } 1161 if (retval) { 1162 unlock_page(page); 1163 page_cache_release(page); 1164 break; 1165 } 1166 1167 /* 1168 * How could swap count reach 0x7ffe ? 1169 * There's no way to repeat a swap page within an mm 1170 * (except in shmem, where it's the shared object which takes 1171 * the reference count)? 1172 * We believe SWAP_MAP_MAX cannot occur.(if occur, unsigned 1173 * short is too small....) 1174 * If that's wrong, then we should worry more about 1175 * exit_mmap() and do_munmap() cases described above: 1176 * we might be resetting SWAP_MAP_MAX too early here. 1177 * We know "Undead"s can happen, they're okay, so don't 1178 * report them; but do report if we reset SWAP_MAP_MAX. 1179 */ 1180 /* We might release the lock_page() in unuse_mm(). */ 1181 if (!PageSwapCache(page) || page_private(page) != entry.val) 1182 goto retry; 1183 1184 if (swap_count(*swap_map) == SWAP_MAP_MAX) { 1185 spin_lock(&swap_lock); 1186 *swap_map = SWAP_HAS_CACHE; 1187 spin_unlock(&swap_lock); 1188 reset_overflow = 1; 1189 } 1190 1191 /* 1192 * If a reference remains (rare), we would like to leave 1193 * the page in the swap cache; but try_to_unmap could 1194 * then re-duplicate the entry once we drop page lock, 1195 * so we might loop indefinitely; also, that page could 1196 * not be swapped out to other storage meanwhile. So: 1197 * delete from cache even if there's another reference, 1198 * after ensuring that the data has been saved to disk - 1199 * since if the reference remains (rarer), it will be 1200 * read from disk into another page. Splitting into two 1201 * pages would be incorrect if swap supported "shared 1202 * private" pages, but they are handled by tmpfs files. 1203 */ 1204 if (swap_count(*swap_map) && 1205 PageDirty(page) && PageSwapCache(page)) { 1206 struct writeback_control wbc = { 1207 .sync_mode = WB_SYNC_NONE, 1208 }; 1209 1210 swap_writepage(page, &wbc); 1211 lock_page(page); 1212 wait_on_page_writeback(page); 1213 } 1214 1215 /* 1216 * It is conceivable that a racing task removed this page from 1217 * swap cache just before we acquired the page lock at the top, 1218 * or while we dropped it in unuse_mm(). The page might even 1219 * be back in swap cache on another swap area: that we must not 1220 * delete, since it may not have been written out to swap yet. 1221 */ 1222 if (PageSwapCache(page) && 1223 likely(page_private(page) == entry.val)) 1224 delete_from_swap_cache(page); 1225 1226 /* 1227 * So we could skip searching mms once swap count went 1228 * to 1, we did not mark any present ptes as dirty: must 1229 * mark page dirty so shrink_page_list will preserve it. 1230 */ 1231 SetPageDirty(page); 1232retry: 1233 unlock_page(page); 1234 page_cache_release(page); 1235 1236 /* 1237 * Make sure that we aren't completely killing 1238 * interactive performance. 1239 */ 1240 cond_resched(); 1241 } 1242 1243 mmput(start_mm); 1244 if (reset_overflow) { 1245 printk(KERN_WARNING "swapoff: cleared swap entry overflow\n"); 1246 swap_overflow = 0; 1247 } 1248 return retval; 1249} 1250 1251/* 1252 * After a successful try_to_unuse, if no swap is now in use, we know 1253 * we can empty the mmlist. swap_lock must be held on entry and exit. 1254 * Note that mmlist_lock nests inside swap_lock, and an mm must be 1255 * added to the mmlist just after page_duplicate - before would be racy. 1256 */ 1257static void drain_mmlist(void) 1258{ 1259 struct list_head *p, *next; 1260 unsigned int type; 1261 1262 for (type = 0; type < nr_swapfiles; type++) 1263 if (swap_info[type]->inuse_pages) 1264 return; 1265 spin_lock(&mmlist_lock); 1266 list_for_each_safe(p, next, &init_mm.mmlist) 1267 list_del_init(p); 1268 spin_unlock(&mmlist_lock); 1269} 1270 1271/* 1272 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which 1273 * corresponds to page offset `offset'. Note that the type of this function 1274 * is sector_t, but it returns page offset into the bdev, not sector offset. 1275 */ 1276sector_t map_swap_page(swp_entry_t entry, struct block_device **bdev) 1277{ 1278 struct swap_info_struct *sis; 1279 struct swap_extent *start_se; 1280 struct swap_extent *se; 1281 pgoff_t offset; 1282 1283 sis = swap_info[swp_type(entry)]; 1284 *bdev = sis->bdev; 1285 1286 offset = swp_offset(entry); 1287 start_se = sis->curr_swap_extent; 1288 se = start_se; 1289 1290 for ( ; ; ) { 1291 struct list_head *lh; 1292 1293 if (se->start_page <= offset && 1294 offset < (se->start_page + se->nr_pages)) { 1295 return se->start_block + (offset - se->start_page); 1296 } 1297 lh = se->list.next; 1298 se = list_entry(lh, struct swap_extent, list); 1299 sis->curr_swap_extent = se; 1300 BUG_ON(se == start_se); /* It *must* be present */ 1301 } 1302} 1303 1304/* 1305 * Free all of a swapdev's extent information 1306 */ 1307static void destroy_swap_extents(struct swap_info_struct *sis) 1308{ 1309 while (!list_empty(&sis->first_swap_extent.list)) { 1310 struct swap_extent *se; 1311 1312 se = list_entry(sis->first_swap_extent.list.next, 1313 struct swap_extent, list); 1314 list_del(&se->list); 1315 kfree(se); 1316 } 1317} 1318 1319/* 1320 * Add a block range (and the corresponding page range) into this swapdev's 1321 * extent list. The extent list is kept sorted in page order. 1322 * 1323 * This function rather assumes that it is called in ascending page order. 1324 */ 1325static int 1326add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, 1327 unsigned long nr_pages, sector_t start_block) 1328{ 1329 struct swap_extent *se; 1330 struct swap_extent *new_se; 1331 struct list_head *lh; 1332 1333 if (start_page == 0) { 1334 se = &sis->first_swap_extent; 1335 sis->curr_swap_extent = se; 1336 se->start_page = 0; 1337 se->nr_pages = nr_pages; 1338 se->start_block = start_block; 1339 return 1; 1340 } else { 1341 lh = sis->first_swap_extent.list.prev; /* Highest extent */ 1342 se = list_entry(lh, struct swap_extent, list); 1343 BUG_ON(se->start_page + se->nr_pages != start_page); 1344 if (se->start_block + se->nr_pages == start_block) { 1345 /* Merge it */ 1346 se->nr_pages += nr_pages; 1347 return 0; 1348 } 1349 } 1350 1351 /* 1352 * No merge. Insert a new extent, preserving ordering. 1353 */ 1354 new_se = kmalloc(sizeof(*se), GFP_KERNEL); 1355 if (new_se == NULL) 1356 return -ENOMEM; 1357 new_se->start_page = start_page; 1358 new_se->nr_pages = nr_pages; 1359 new_se->start_block = start_block; 1360 1361 list_add_tail(&new_se->list, &sis->first_swap_extent.list); 1362 return 1; 1363} 1364 1365/* 1366 * A `swap extent' is a simple thing which maps a contiguous range of pages 1367 * onto a contiguous range of disk blocks. An ordered list of swap extents 1368 * is built at swapon time and is then used at swap_writepage/swap_readpage 1369 * time for locating where on disk a page belongs. 1370 * 1371 * If the swapfile is an S_ISBLK block device, a single extent is installed. 1372 * This is done so that the main operating code can treat S_ISBLK and S_ISREG 1373 * swap files identically. 1374 * 1375 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap 1376 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK 1377 * swapfiles are handled *identically* after swapon time. 1378 * 1379 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks 1380 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If 1381 * some stray blocks are found which do not fall within the PAGE_SIZE alignment 1382 * requirements, they are simply tossed out - we will never use those blocks 1383 * for swapping. 1384 * 1385 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This 1386 * prevents root from shooting her foot off by ftruncating an in-use swapfile, 1387 * which will scribble on the fs. 1388 * 1389 * The amount of disk space which a single swap extent represents varies. 1390 * Typically it is in the 1-4 megabyte range. So we can have hundreds of 1391 * extents in the list. To avoid much list walking, we cache the previous 1392 * search location in `curr_swap_extent', and start new searches from there. 1393 * This is extremely effective. The average number of iterations in 1394 * map_swap_page() has been measured at about 0.3 per page. - akpm. 1395 */ 1396static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) 1397{ 1398 struct inode *inode; 1399 unsigned blocks_per_page; 1400 unsigned long page_no; 1401 unsigned blkbits; 1402 sector_t probe_block; 1403 sector_t last_block; 1404 sector_t lowest_block = -1; 1405 sector_t highest_block = 0; 1406 int nr_extents = 0; 1407 int ret; 1408 1409 inode = sis->swap_file->f_mapping->host; 1410 if (S_ISBLK(inode->i_mode)) { 1411 ret = add_swap_extent(sis, 0, sis->max, 0); 1412 *span = sis->pages; 1413 goto out; 1414 } 1415 1416 blkbits = inode->i_blkbits; 1417 blocks_per_page = PAGE_SIZE >> blkbits; 1418 1419 /* 1420 * Map all the blocks into the extent list. This code doesn't try 1421 * to be very smart. 1422 */ 1423 probe_block = 0; 1424 page_no = 0; 1425 last_block = i_size_read(inode) >> blkbits; 1426 while ((probe_block + blocks_per_page) <= last_block && 1427 page_no < sis->max) { 1428 unsigned block_in_page; 1429 sector_t first_block; 1430 1431 first_block = bmap(inode, probe_block); 1432 if (first_block == 0) 1433 goto bad_bmap; 1434 1435 /* 1436 * It must be PAGE_SIZE aligned on-disk 1437 */ 1438 if (first_block & (blocks_per_page - 1)) { 1439 probe_block++; 1440 goto reprobe; 1441 } 1442 1443 for (block_in_page = 1; block_in_page < blocks_per_page; 1444 block_in_page++) { 1445 sector_t block; 1446 1447 block = bmap(inode, probe_block + block_in_page); 1448 if (block == 0) 1449 goto bad_bmap; 1450 if (block != first_block + block_in_page) { 1451 /* Discontiguity */ 1452 probe_block++; 1453 goto reprobe; 1454 } 1455 } 1456 1457 first_block >>= (PAGE_SHIFT - blkbits); 1458 if (page_no) { /* exclude the header page */ 1459 if (first_block < lowest_block) 1460 lowest_block = first_block; 1461 if (first_block > highest_block) 1462 highest_block = first_block; 1463 } 1464 1465 /* 1466 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 1467 */ 1468 ret = add_swap_extent(sis, page_no, 1, first_block); 1469 if (ret < 0) 1470 goto out; 1471 nr_extents += ret; 1472 page_no++; 1473 probe_block += blocks_per_page; 1474reprobe: 1475 continue; 1476 } 1477 ret = nr_extents; 1478 *span = 1 + highest_block - lowest_block; 1479 if (page_no == 0) 1480 page_no = 1; /* force Empty message */ 1481 sis->max = page_no; 1482 sis->pages = page_no - 1; 1483 sis->highest_bit = page_no - 1; 1484out: 1485 return ret; 1486bad_bmap: 1487 printk(KERN_ERR "swapon: swapfile has holes\n"); 1488 ret = -EINVAL; 1489 goto out; 1490} 1491 1492SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) 1493{ 1494 struct swap_info_struct *p = NULL; 1495 unsigned short *swap_map; 1496 struct file *swap_file, *victim; 1497 struct address_space *mapping; 1498 struct inode *inode; 1499 char *pathname; 1500 int i, type, prev; 1501 int err; 1502 1503 if (!capable(CAP_SYS_ADMIN)) 1504 return -EPERM; 1505 1506 pathname = getname(specialfile); 1507 err = PTR_ERR(pathname); 1508 if (IS_ERR(pathname)) 1509 goto out; 1510 1511 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0); 1512 putname(pathname); 1513 err = PTR_ERR(victim); 1514 if (IS_ERR(victim)) 1515 goto out; 1516 1517 mapping = victim->f_mapping; 1518 prev = -1; 1519 spin_lock(&swap_lock); 1520 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) { 1521 p = swap_info[type]; 1522 if (p->flags & SWP_WRITEOK) { 1523 if (p->swap_file->f_mapping == mapping) 1524 break; 1525 } 1526 prev = type; 1527 } 1528 if (type < 0) { 1529 err = -EINVAL; 1530 spin_unlock(&swap_lock); 1531 goto out_dput; 1532 } 1533 if (!security_vm_enough_memory(p->pages)) 1534 vm_unacct_memory(p->pages); 1535 else { 1536 err = -ENOMEM; 1537 spin_unlock(&swap_lock); 1538 goto out_dput; 1539 } 1540 if (prev < 0) 1541 swap_list.head = p->next; 1542 else 1543 swap_info[prev]->next = p->next; 1544 if (type == swap_list.next) { 1545 /* just pick something that's safe... */ 1546 swap_list.next = swap_list.head; 1547 } 1548 if (p->prio < 0) { 1549 for (i = p->next; i >= 0; i = swap_info[i]->next) 1550 swap_info[i]->prio = p->prio--; 1551 least_priority++; 1552 } 1553 nr_swap_pages -= p->pages; 1554 total_swap_pages -= p->pages; 1555 p->flags &= ~SWP_WRITEOK; 1556 spin_unlock(&swap_lock); 1557 1558 current->flags |= PF_OOM_ORIGIN; 1559 err = try_to_unuse(type); 1560 current->flags &= ~PF_OOM_ORIGIN; 1561 1562 if (err) { 1563 /* re-insert swap space back into swap_list */ 1564 spin_lock(&swap_lock); 1565 if (p->prio < 0) 1566 p->prio = --least_priority; 1567 prev = -1; 1568 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { 1569 if (p->prio >= swap_info[i]->prio) 1570 break; 1571 prev = i; 1572 } 1573 p->next = i; 1574 if (prev < 0) 1575 swap_list.head = swap_list.next = type; 1576 else 1577 swap_info[prev]->next = type; 1578 nr_swap_pages += p->pages; 1579 total_swap_pages += p->pages; 1580 p->flags |= SWP_WRITEOK; 1581 spin_unlock(&swap_lock); 1582 goto out_dput; 1583 } 1584 1585 /* wait for any unplug function to finish */ 1586 down_write(&swap_unplug_sem); 1587 up_write(&swap_unplug_sem); 1588 1589 destroy_swap_extents(p); 1590 mutex_lock(&swapon_mutex); 1591 spin_lock(&swap_lock); 1592 drain_mmlist(); 1593 1594 /* wait for anyone still in scan_swap_map */ 1595 p->highest_bit = 0; /* cuts scans short */ 1596 while (p->flags >= SWP_SCANNING) { 1597 spin_unlock(&swap_lock); 1598 schedule_timeout_uninterruptible(1); 1599 spin_lock(&swap_lock); 1600 } 1601 1602 swap_file = p->swap_file; 1603 p->swap_file = NULL; 1604 p->max = 0; 1605 swap_map = p->swap_map; 1606 p->swap_map = NULL; 1607 p->flags = 0; 1608 spin_unlock(&swap_lock); 1609 mutex_unlock(&swapon_mutex); 1610 vfree(swap_map); 1611 /* Destroy swap account informatin */ 1612 swap_cgroup_swapoff(type); 1613 1614 inode = mapping->host; 1615 if (S_ISBLK(inode->i_mode)) { 1616 struct block_device *bdev = I_BDEV(inode); 1617 set_blocksize(bdev, p->old_block_size); 1618 bd_release(bdev); 1619 } else { 1620 mutex_lock(&inode->i_mutex); 1621 inode->i_flags &= ~S_SWAPFILE; 1622 mutex_unlock(&inode->i_mutex); 1623 } 1624 filp_close(swap_file, NULL); 1625 err = 0; 1626 1627out_dput: 1628 filp_close(victim, NULL); 1629out: 1630 return err; 1631} 1632 1633#ifdef CONFIG_PROC_FS 1634/* iterator */ 1635static void *swap_start(struct seq_file *swap, loff_t *pos) 1636{ 1637 struct swap_info_struct *si; 1638 int type; 1639 loff_t l = *pos; 1640 1641 mutex_lock(&swapon_mutex); 1642 1643 if (!l) 1644 return SEQ_START_TOKEN; 1645 1646 for (type = 0; type < nr_swapfiles; type++) { 1647 smp_rmb(); /* read nr_swapfiles before swap_info[type] */ 1648 si = swap_info[type]; 1649 if (!(si->flags & SWP_USED) || !si->swap_map) 1650 continue; 1651 if (!--l) 1652 return si; 1653 } 1654 1655 return NULL; 1656} 1657 1658static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) 1659{ 1660 struct swap_info_struct *si = v; 1661 int type; 1662 1663 if (v == SEQ_START_TOKEN) 1664 type = 0; 1665 else 1666 type = si->type + 1; 1667 1668 for (; type < nr_swapfiles; type++) { 1669 smp_rmb(); /* read nr_swapfiles before swap_info[type] */ 1670 si = swap_info[type]; 1671 if (!(si->flags & SWP_USED) || !si->swap_map) 1672 continue; 1673 ++*pos; 1674 return si; 1675 } 1676 1677 return NULL; 1678} 1679 1680static void swap_stop(struct seq_file *swap, void *v) 1681{ 1682 mutex_unlock(&swapon_mutex); 1683} 1684 1685static int swap_show(struct seq_file *swap, void *v) 1686{ 1687 struct swap_info_struct *si = v; 1688 struct file *file; 1689 int len; 1690 1691 if (si == SEQ_START_TOKEN) { 1692 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); 1693 return 0; 1694 } 1695 1696 file = si->swap_file; 1697 len = seq_path(swap, &file->f_path, " \t\n\\"); 1698 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n", 1699 len < 40 ? 40 - len : 1, " ", 1700 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ? 1701 "partition" : "file\t", 1702 si->pages << (PAGE_SHIFT - 10), 1703 si->inuse_pages << (PAGE_SHIFT - 10), 1704 si->prio); 1705 return 0; 1706} 1707 1708static const struct seq_operations swaps_op = { 1709 .start = swap_start, 1710 .next = swap_next, 1711 .stop = swap_stop, 1712 .show = swap_show 1713}; 1714 1715static int swaps_open(struct inode *inode, struct file *file) 1716{ 1717 return seq_open(file, &swaps_op); 1718} 1719 1720static const struct file_operations proc_swaps_operations = { 1721 .open = swaps_open, 1722 .read = seq_read, 1723 .llseek = seq_lseek, 1724 .release = seq_release, 1725}; 1726 1727static int __init procswaps_init(void) 1728{ 1729 proc_create("swaps", 0, NULL, &proc_swaps_operations); 1730 return 0; 1731} 1732__initcall(procswaps_init); 1733#endif /* CONFIG_PROC_FS */ 1734 1735#ifdef MAX_SWAPFILES_CHECK 1736static int __init max_swapfiles_check(void) 1737{ 1738 MAX_SWAPFILES_CHECK(); 1739 return 0; 1740} 1741late_initcall(max_swapfiles_check); 1742#endif 1743 1744/* 1745 * Written 01/25/92 by Simmule Turner, heavily changed by Linus. 1746 * 1747 * The swapon system call 1748 */ 1749SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 1750{ 1751 struct swap_info_struct *p; 1752 char *name = NULL; 1753 struct block_device *bdev = NULL; 1754 struct file *swap_file = NULL; 1755 struct address_space *mapping; 1756 unsigned int type; 1757 int i, prev; 1758 int error; 1759 union swap_header *swap_header = NULL; 1760 unsigned int nr_good_pages = 0; 1761 int nr_extents = 0; 1762 sector_t span; 1763 unsigned long maxpages = 1; 1764 unsigned long swapfilepages; 1765 unsigned short *swap_map = NULL; 1766 struct page *page = NULL; 1767 struct inode *inode = NULL; 1768 int did_down = 0; 1769 1770 if (!capable(CAP_SYS_ADMIN)) 1771 return -EPERM; 1772 1773 p = kzalloc(sizeof(*p), GFP_KERNEL); 1774 if (!p) 1775 return -ENOMEM; 1776 1777 spin_lock(&swap_lock); 1778 for (type = 0; type < nr_swapfiles; type++) { 1779 if (!(swap_info[type]->flags & SWP_USED)) 1780 break; 1781 } 1782 error = -EPERM; 1783 if (type >= MAX_SWAPFILES) { 1784 spin_unlock(&swap_lock); 1785 kfree(p); 1786 goto out; 1787 } 1788 if (type >= nr_swapfiles) { 1789 p->type = type; 1790 swap_info[type] = p; 1791 /* 1792 * Write swap_info[type] before nr_swapfiles, in case a 1793 * racing procfs swap_start() or swap_next() is reading them. 1794 * (We never shrink nr_swapfiles, we never free this entry.) 1795 */ 1796 smp_wmb(); 1797 nr_swapfiles++; 1798 } else { 1799 kfree(p); 1800 p = swap_info[type]; 1801 /* 1802 * Do not memset this entry: a racing procfs swap_next() 1803 * would be relying on p->type to remain valid. 1804 */ 1805 } 1806 INIT_LIST_HEAD(&p->first_swap_extent.list); 1807 p->flags = SWP_USED; 1808 p->next = -1; 1809 spin_unlock(&swap_lock); 1810 1811 name = getname(specialfile); 1812 error = PTR_ERR(name); 1813 if (IS_ERR(name)) { 1814 name = NULL; 1815 goto bad_swap_2; 1816 } 1817 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0); 1818 error = PTR_ERR(swap_file); 1819 if (IS_ERR(swap_file)) { 1820 swap_file = NULL; 1821 goto bad_swap_2; 1822 } 1823 1824 p->swap_file = swap_file; 1825 mapping = swap_file->f_mapping; 1826 inode = mapping->host; 1827 1828 error = -EBUSY; 1829 for (i = 0; i < nr_swapfiles; i++) { 1830 struct swap_info_struct *q = swap_info[i]; 1831 1832 if (i == type || !q->swap_file) 1833 continue; 1834 if (mapping == q->swap_file->f_mapping) 1835 goto bad_swap; 1836 } 1837 1838 error = -EINVAL; 1839 if (S_ISBLK(inode->i_mode)) { 1840 bdev = I_BDEV(inode); 1841 error = bd_claim(bdev, sys_swapon); 1842 if (error < 0) { 1843 bdev = NULL; 1844 error = -EINVAL; 1845 goto bad_swap; 1846 } 1847 p->old_block_size = block_size(bdev); 1848 error = set_blocksize(bdev, PAGE_SIZE); 1849 if (error < 0) 1850 goto bad_swap; 1851 p->bdev = bdev; 1852 } else if (S_ISREG(inode->i_mode)) { 1853 p->bdev = inode->i_sb->s_bdev; 1854 mutex_lock(&inode->i_mutex); 1855 did_down = 1; 1856 if (IS_SWAPFILE(inode)) { 1857 error = -EBUSY; 1858 goto bad_swap; 1859 } 1860 } else { 1861 goto bad_swap; 1862 } 1863 1864 swapfilepages = i_size_read(inode) >> PAGE_SHIFT; 1865 1866 /* 1867 * Read the swap header. 1868 */ 1869 if (!mapping->a_ops->readpage) { 1870 error = -EINVAL; 1871 goto bad_swap; 1872 } 1873 page = read_mapping_page(mapping, 0, swap_file); 1874 if (IS_ERR(page)) { 1875 error = PTR_ERR(page); 1876 goto bad_swap; 1877 } 1878 swap_header = kmap(page); 1879 1880 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { 1881 printk(KERN_ERR "Unable to find swap-space signature\n"); 1882 error = -EINVAL; 1883 goto bad_swap; 1884 } 1885 1886 /* swap partition endianess hack... */ 1887 if (swab32(swap_header->info.version) == 1) { 1888 swab32s(&swap_header->info.version); 1889 swab32s(&swap_header->info.last_page); 1890 swab32s(&swap_header->info.nr_badpages); 1891 for (i = 0; i < swap_header->info.nr_badpages; i++) 1892 swab32s(&swap_header->info.badpages[i]); 1893 } 1894 /* Check the swap header's sub-version */ 1895 if (swap_header->info.version != 1) { 1896 printk(KERN_WARNING 1897 "Unable to handle swap header version %d\n", 1898 swap_header->info.version); 1899 error = -EINVAL; 1900 goto bad_swap; 1901 } 1902 1903 p->lowest_bit = 1; 1904 p->cluster_next = 1; 1905 p->cluster_nr = 0; 1906 1907 /* 1908 * Find out how many pages are allowed for a single swap 1909 * device. There are two limiting factors: 1) the number of 1910 * bits for the swap offset in the swp_entry_t type and 1911 * 2) the number of bits in the a swap pte as defined by 1912 * the different architectures. In order to find the 1913 * largest possible bit mask a swap entry with swap type 0 1914 * and swap offset ~0UL is created, encoded to a swap pte, 1915 * decoded to a swp_entry_t again and finally the swap 1916 * offset is extracted. This will mask all the bits from 1917 * the initial ~0UL mask that can't be encoded in either 1918 * the swp_entry_t or the architecture definition of a 1919 * swap pte. 1920 */ 1921 maxpages = swp_offset(pte_to_swp_entry( 1922 swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1; 1923 if (maxpages > swap_header->info.last_page) 1924 maxpages = swap_header->info.last_page; 1925 p->highest_bit = maxpages - 1; 1926 1927 error = -EINVAL; 1928 if (!maxpages) 1929 goto bad_swap; 1930 if (swapfilepages && maxpages > swapfilepages) { 1931 printk(KERN_WARNING 1932 "Swap area shorter than signature indicates\n"); 1933 goto bad_swap; 1934 } 1935 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) 1936 goto bad_swap; 1937 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) 1938 goto bad_swap; 1939 1940 /* OK, set up the swap map and apply the bad block list */ 1941 swap_map = vmalloc(maxpages * sizeof(short)); 1942 if (!swap_map) { 1943 error = -ENOMEM; 1944 goto bad_swap; 1945 } 1946 1947 memset(swap_map, 0, maxpages * sizeof(short)); 1948 for (i = 0; i < swap_header->info.nr_badpages; i++) { 1949 int page_nr = swap_header->info.badpages[i]; 1950 if (page_nr <= 0 || page_nr >= swap_header->info.last_page) { 1951 error = -EINVAL; 1952 goto bad_swap; 1953 } 1954 swap_map[page_nr] = SWAP_MAP_BAD; 1955 } 1956 1957 error = swap_cgroup_swapon(type, maxpages); 1958 if (error) 1959 goto bad_swap; 1960 1961 nr_good_pages = swap_header->info.last_page - 1962 swap_header->info.nr_badpages - 1963 1 /* header page */; 1964 1965 if (nr_good_pages) { 1966 swap_map[0] = SWAP_MAP_BAD; 1967 p->max = maxpages; 1968 p->pages = nr_good_pages; 1969 nr_extents = setup_swap_extents(p, &span); 1970 if (nr_extents < 0) { 1971 error = nr_extents; 1972 goto bad_swap; 1973 } 1974 nr_good_pages = p->pages; 1975 } 1976 if (!nr_good_pages) { 1977 printk(KERN_WARNING "Empty swap-file\n"); 1978 error = -EINVAL; 1979 goto bad_swap; 1980 } 1981 1982 if (p->bdev) { 1983 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { 1984 p->flags |= SWP_SOLIDSTATE; 1985 p->cluster_next = 1 + (random32() % p->highest_bit); 1986 } 1987 if (discard_swap(p) == 0) 1988 p->flags |= SWP_DISCARDABLE; 1989 } 1990 1991 mutex_lock(&swapon_mutex); 1992 spin_lock(&swap_lock); 1993 if (swap_flags & SWAP_FLAG_PREFER) 1994 p->prio = 1995 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; 1996 else 1997 p->prio = --least_priority; 1998 p->swap_map = swap_map; 1999 p->flags |= SWP_WRITEOK; 2000 nr_swap_pages += nr_good_pages; 2001 total_swap_pages += nr_good_pages; 2002 2003 printk(KERN_INFO "Adding %uk swap on %s. " 2004 "Priority:%d extents:%d across:%lluk %s%s\n", 2005 nr_good_pages<<(PAGE_SHIFT-10), name, p->prio, 2006 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10), 2007 (p->flags & SWP_SOLIDSTATE) ? "SS" : "", 2008 (p->flags & SWP_DISCARDABLE) ? "D" : ""); 2009 2010 /* insert swap space into swap_list: */ 2011 prev = -1; 2012 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { 2013 if (p->prio >= swap_info[i]->prio) 2014 break; 2015 prev = i; 2016 } 2017 p->next = i; 2018 if (prev < 0) 2019 swap_list.head = swap_list.next = type; 2020 else 2021 swap_info[prev]->next = type; 2022 spin_unlock(&swap_lock); 2023 mutex_unlock(&swapon_mutex); 2024 error = 0; 2025 goto out; 2026bad_swap: 2027 if (bdev) { 2028 set_blocksize(bdev, p->old_block_size); 2029 bd_release(bdev); 2030 } 2031 destroy_swap_extents(p); 2032 swap_cgroup_swapoff(type); 2033bad_swap_2: 2034 spin_lock(&swap_lock); 2035 p->swap_file = NULL; 2036 p->flags = 0; 2037 spin_unlock(&swap_lock); 2038 vfree(swap_map); 2039 if (swap_file) 2040 filp_close(swap_file, NULL); 2041out: 2042 if (page && !IS_ERR(page)) { 2043 kunmap(page); 2044 page_cache_release(page); 2045 } 2046 if (name) 2047 putname(name); 2048 if (did_down) { 2049 if (!error) 2050 inode->i_flags |= S_SWAPFILE; 2051 mutex_unlock(&inode->i_mutex); 2052 } 2053 return error; 2054} 2055 2056void si_swapinfo(struct sysinfo *val) 2057{ 2058 unsigned int type; 2059 unsigned long nr_to_be_unused = 0; 2060 2061 spin_lock(&swap_lock); 2062 for (type = 0; type < nr_swapfiles; type++) { 2063 struct swap_info_struct *si = swap_info[type]; 2064 2065 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) 2066 nr_to_be_unused += si->inuse_pages; 2067 } 2068 val->freeswap = nr_swap_pages + nr_to_be_unused; 2069 val->totalswap = total_swap_pages + nr_to_be_unused; 2070 spin_unlock(&swap_lock); 2071} 2072 2073/* 2074 * Verify that a swap entry is valid and increment its swap map count. 2075 * 2076 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as 2077 * "permanent", but will be reclaimed by the next swapoff. 2078 * Returns error code in following case. 2079 * - success -> 0 2080 * - swp_entry is invalid -> EINVAL 2081 * - swp_entry is migration entry -> EINVAL 2082 * - swap-cache reference is requested but there is already one. -> EEXIST 2083 * - swap-cache reference is requested but the entry is not used. -> ENOENT 2084 */ 2085static int __swap_duplicate(swp_entry_t entry, unsigned short usage) 2086{ 2087 struct swap_info_struct *p; 2088 unsigned long offset, type; 2089 unsigned short count; 2090 unsigned short has_cache; 2091 int err = -EINVAL; 2092 2093 if (non_swap_entry(entry)) 2094 goto out; 2095 2096 type = swp_type(entry); 2097 if (type >= nr_swapfiles) 2098 goto bad_file; 2099 p = swap_info[type]; 2100 offset = swp_offset(entry); 2101 2102 spin_lock(&swap_lock); 2103 if (unlikely(offset >= p->max)) 2104 goto unlock_out; 2105 2106 count = p->swap_map[offset]; 2107 has_cache = count & SWAP_HAS_CACHE; 2108 count &= ~SWAP_HAS_CACHE; 2109 err = 0; 2110 2111 if (usage == SWAP_HAS_CACHE) { 2112 2113 /* set SWAP_HAS_CACHE if there is no cache and entry is used */ 2114 if (!has_cache && count) 2115 has_cache = SWAP_HAS_CACHE; 2116 else if (has_cache) /* someone else added cache */ 2117 err = -EEXIST; 2118 else /* no users remaining */ 2119 err = -ENOENT; 2120 2121 } else if (count || has_cache) { 2122 2123 if (count < SWAP_MAP_MAX - 1) 2124 count++; 2125 else if (count <= SWAP_MAP_MAX) { 2126 if (swap_overflow++ < 5) 2127 printk(KERN_WARNING 2128 "swap_dup: swap entry overflow\n"); 2129 count = SWAP_MAP_MAX; 2130 } else 2131 err = -EINVAL; 2132 } else 2133 err = -ENOENT; /* unused swap entry */ 2134 2135 p->swap_map[offset] = count | has_cache; 2136 2137unlock_out: 2138 spin_unlock(&swap_lock); 2139out: 2140 return err; 2141 2142bad_file: 2143 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); 2144 goto out; 2145} 2146 2147/* 2148 * increase reference count of swap entry by 1. 2149 */ 2150void swap_duplicate(swp_entry_t entry) 2151{ 2152 __swap_duplicate(entry, 1); 2153} 2154 2155/* 2156 * @entry: swap entry for which we allocate swap cache. 2157 * 2158 * Called when allocating swap cache for existing swap entry, 2159 * This can return error codes. Returns 0 at success. 2160 * -EBUSY means there is a swap cache. 2161 * Note: return code is different from swap_duplicate(). 2162 */ 2163int swapcache_prepare(swp_entry_t entry) 2164{ 2165 return __swap_duplicate(entry, SWAP_HAS_CACHE); 2166} 2167 2168/* 2169 * swap_lock prevents swap_map being freed. Don't grab an extra 2170 * reference on the swaphandle, it doesn't matter if it becomes unused. 2171 */ 2172int valid_swaphandles(swp_entry_t entry, unsigned long *offset) 2173{ 2174 struct swap_info_struct *si; 2175 int our_page_cluster = page_cluster; 2176 pgoff_t target, toff; 2177 pgoff_t base, end; 2178 int nr_pages = 0; 2179 2180 if (!our_page_cluster) /* no readahead */ 2181 return 0; 2182 2183 si = swap_info[swp_type(entry)]; 2184 target = swp_offset(entry); 2185 base = (target >> our_page_cluster) << our_page_cluster; 2186 end = base + (1 << our_page_cluster); 2187 if (!base) /* first page is swap header */ 2188 base++; 2189 2190 spin_lock(&swap_lock); 2191 if (end > si->max) /* don't go beyond end of map */ 2192 end = si->max; 2193 2194 /* Count contiguous allocated slots above our target */ 2195 for (toff = target; ++toff < end; nr_pages++) { 2196 /* Don't read in free or bad pages */ 2197 if (!si->swap_map[toff]) 2198 break; 2199 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) 2200 break; 2201 } 2202 /* Count contiguous allocated slots below our target */ 2203 for (toff = target; --toff >= base; nr_pages++) { 2204 /* Don't read in free or bad pages */ 2205 if (!si->swap_map[toff]) 2206 break; 2207 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) 2208 break; 2209 } 2210 spin_unlock(&swap_lock); 2211 2212 /* 2213 * Indicate starting offset, and return number of pages to get: 2214 * if only 1, say 0, since there's then no readahead to be done. 2215 */ 2216 *offset = ++toff; 2217 return nr_pages? ++nr_pages: 0; 2218} 2219