swapfile.c revision 72788c385604523422592249c19cba0187021e9b
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#include <linux/poll.h> 34#include <linux/oom.h> 35 36#include <asm/pgtable.h> 37#include <asm/tlbflush.h> 38#include <linux/swapops.h> 39#include <linux/page_cgroup.h> 40 41static bool swap_count_continued(struct swap_info_struct *, pgoff_t, 42 unsigned char); 43static void free_swap_count_continuations(struct swap_info_struct *); 44static sector_t map_swap_entry(swp_entry_t, struct block_device**); 45 46static DEFINE_SPINLOCK(swap_lock); 47static unsigned int nr_swapfiles; 48long nr_swap_pages; 49long total_swap_pages; 50static int least_priority; 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 DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait); 64/* Activity counter to indicate that a swapon or swapoff has occurred */ 65static atomic_t proc_poll_event = ATOMIC_INIT(0); 66 67static inline unsigned char swap_count(unsigned char ent) 68{ 69 return ent & ~SWAP_HAS_CACHE; /* may include SWAP_HAS_CONT flag */ 70} 71 72/* returns 1 if swap entry is freed */ 73static int 74__try_to_reclaim_swap(struct swap_info_struct *si, unsigned long offset) 75{ 76 swp_entry_t entry = swp_entry(si->type, offset); 77 struct page *page; 78 int ret = 0; 79 80 page = find_get_page(&swapper_space, entry.val); 81 if (!page) 82 return 0; 83 /* 84 * This function is called from scan_swap_map() and it's called 85 * by vmscan.c at reclaiming pages. So, we hold a lock on a page, here. 86 * We have to use trylock for avoiding deadlock. This is a special 87 * case and you should use try_to_free_swap() with explicit lock_page() 88 * in usual operations. 89 */ 90 if (trylock_page(page)) { 91 ret = try_to_free_swap(page); 92 unlock_page(page); 93 } 94 page_cache_release(page); 95 return ret; 96} 97 98/* 99 * swapon tell device that all the old swap contents can be discarded, 100 * to allow the swap device to optimize its wear-levelling. 101 */ 102static int discard_swap(struct swap_info_struct *si) 103{ 104 struct swap_extent *se; 105 sector_t start_block; 106 sector_t nr_blocks; 107 int err = 0; 108 109 /* Do not discard the swap header page! */ 110 se = &si->first_swap_extent; 111 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9); 112 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9); 113 if (nr_blocks) { 114 err = blkdev_issue_discard(si->bdev, start_block, 115 nr_blocks, GFP_KERNEL, 0); 116 if (err) 117 return err; 118 cond_resched(); 119 } 120 121 list_for_each_entry(se, &si->first_swap_extent.list, list) { 122 start_block = se->start_block << (PAGE_SHIFT - 9); 123 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9); 124 125 err = blkdev_issue_discard(si->bdev, start_block, 126 nr_blocks, GFP_KERNEL, 0); 127 if (err) 128 break; 129 130 cond_resched(); 131 } 132 return err; /* That will often be -EOPNOTSUPP */ 133} 134 135/* 136 * swap allocation tell device that a cluster of swap can now be discarded, 137 * to allow the swap device to optimize its wear-levelling. 138 */ 139static void discard_swap_cluster(struct swap_info_struct *si, 140 pgoff_t start_page, pgoff_t nr_pages) 141{ 142 struct swap_extent *se = si->curr_swap_extent; 143 int found_extent = 0; 144 145 while (nr_pages) { 146 struct list_head *lh; 147 148 if (se->start_page <= start_page && 149 start_page < se->start_page + se->nr_pages) { 150 pgoff_t offset = start_page - se->start_page; 151 sector_t start_block = se->start_block + offset; 152 sector_t nr_blocks = se->nr_pages - offset; 153 154 if (nr_blocks > nr_pages) 155 nr_blocks = nr_pages; 156 start_page += nr_blocks; 157 nr_pages -= nr_blocks; 158 159 if (!found_extent++) 160 si->curr_swap_extent = se; 161 162 start_block <<= PAGE_SHIFT - 9; 163 nr_blocks <<= PAGE_SHIFT - 9; 164 if (blkdev_issue_discard(si->bdev, start_block, 165 nr_blocks, GFP_NOIO, 0)) 166 break; 167 } 168 169 lh = se->list.next; 170 se = list_entry(lh, struct swap_extent, list); 171 } 172} 173 174static int wait_for_discard(void *word) 175{ 176 schedule(); 177 return 0; 178} 179 180#define SWAPFILE_CLUSTER 256 181#define LATENCY_LIMIT 256 182 183static unsigned long scan_swap_map(struct swap_info_struct *si, 184 unsigned char usage) 185{ 186 unsigned long offset; 187 unsigned long scan_base; 188 unsigned long last_in_cluster = 0; 189 int latency_ration = LATENCY_LIMIT; 190 int found_free_cluster = 0; 191 192 /* 193 * We try to cluster swap pages by allocating them sequentially 194 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this 195 * way, however, we resort to first-free allocation, starting 196 * a new cluster. This prevents us from scattering swap pages 197 * all over the entire swap partition, so that we reduce 198 * overall disk seek times between swap pages. -- sct 199 * But we do now try to find an empty cluster. -Andrea 200 * And we let swap pages go all over an SSD partition. Hugh 201 */ 202 203 si->flags += SWP_SCANNING; 204 scan_base = offset = si->cluster_next; 205 206 if (unlikely(!si->cluster_nr--)) { 207 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) { 208 si->cluster_nr = SWAPFILE_CLUSTER - 1; 209 goto checks; 210 } 211 if (si->flags & SWP_DISCARDABLE) { 212 /* 213 * Start range check on racing allocations, in case 214 * they overlap the cluster we eventually decide on 215 * (we scan without swap_lock to allow preemption). 216 * It's hardly conceivable that cluster_nr could be 217 * wrapped during our scan, but don't depend on it. 218 */ 219 if (si->lowest_alloc) 220 goto checks; 221 si->lowest_alloc = si->max; 222 si->highest_alloc = 0; 223 } 224 spin_unlock(&swap_lock); 225 226 /* 227 * If seek is expensive, start searching for new cluster from 228 * start of partition, to minimize the span of allocated swap. 229 * But if seek is cheap, search from our current position, so 230 * that swap is allocated from all over the partition: if the 231 * Flash Translation Layer only remaps within limited zones, 232 * we don't want to wear out the first zone too quickly. 233 */ 234 if (!(si->flags & SWP_SOLIDSTATE)) 235 scan_base = offset = si->lowest_bit; 236 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 237 238 /* Locate the first empty (unaligned) cluster */ 239 for (; last_in_cluster <= si->highest_bit; offset++) { 240 if (si->swap_map[offset]) 241 last_in_cluster = offset + SWAPFILE_CLUSTER; 242 else if (offset == last_in_cluster) { 243 spin_lock(&swap_lock); 244 offset -= SWAPFILE_CLUSTER - 1; 245 si->cluster_next = offset; 246 si->cluster_nr = SWAPFILE_CLUSTER - 1; 247 found_free_cluster = 1; 248 goto checks; 249 } 250 if (unlikely(--latency_ration < 0)) { 251 cond_resched(); 252 latency_ration = LATENCY_LIMIT; 253 } 254 } 255 256 offset = si->lowest_bit; 257 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 258 259 /* Locate the first empty (unaligned) cluster */ 260 for (; last_in_cluster < scan_base; offset++) { 261 if (si->swap_map[offset]) 262 last_in_cluster = offset + SWAPFILE_CLUSTER; 263 else if (offset == last_in_cluster) { 264 spin_lock(&swap_lock); 265 offset -= SWAPFILE_CLUSTER - 1; 266 si->cluster_next = offset; 267 si->cluster_nr = SWAPFILE_CLUSTER - 1; 268 found_free_cluster = 1; 269 goto checks; 270 } 271 if (unlikely(--latency_ration < 0)) { 272 cond_resched(); 273 latency_ration = LATENCY_LIMIT; 274 } 275 } 276 277 offset = scan_base; 278 spin_lock(&swap_lock); 279 si->cluster_nr = SWAPFILE_CLUSTER - 1; 280 si->lowest_alloc = 0; 281 } 282 283checks: 284 if (!(si->flags & SWP_WRITEOK)) 285 goto no_page; 286 if (!si->highest_bit) 287 goto no_page; 288 if (offset > si->highest_bit) 289 scan_base = offset = si->lowest_bit; 290 291 /* reuse swap entry of cache-only swap if not busy. */ 292 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 293 int swap_was_freed; 294 spin_unlock(&swap_lock); 295 swap_was_freed = __try_to_reclaim_swap(si, offset); 296 spin_lock(&swap_lock); 297 /* entry was freed successfully, try to use this again */ 298 if (swap_was_freed) 299 goto checks; 300 goto scan; /* check next one */ 301 } 302 303 if (si->swap_map[offset]) 304 goto scan; 305 306 if (offset == si->lowest_bit) 307 si->lowest_bit++; 308 if (offset == si->highest_bit) 309 si->highest_bit--; 310 si->inuse_pages++; 311 if (si->inuse_pages == si->pages) { 312 si->lowest_bit = si->max; 313 si->highest_bit = 0; 314 } 315 si->swap_map[offset] = usage; 316 si->cluster_next = offset + 1; 317 si->flags -= SWP_SCANNING; 318 319 if (si->lowest_alloc) { 320 /* 321 * Only set when SWP_DISCARDABLE, and there's a scan 322 * for a free cluster in progress or just completed. 323 */ 324 if (found_free_cluster) { 325 /* 326 * To optimize wear-levelling, discard the 327 * old data of the cluster, taking care not to 328 * discard any of its pages that have already 329 * been allocated by racing tasks (offset has 330 * already stepped over any at the beginning). 331 */ 332 if (offset < si->highest_alloc && 333 si->lowest_alloc <= last_in_cluster) 334 last_in_cluster = si->lowest_alloc - 1; 335 si->flags |= SWP_DISCARDING; 336 spin_unlock(&swap_lock); 337 338 if (offset < last_in_cluster) 339 discard_swap_cluster(si, offset, 340 last_in_cluster - offset + 1); 341 342 spin_lock(&swap_lock); 343 si->lowest_alloc = 0; 344 si->flags &= ~SWP_DISCARDING; 345 346 smp_mb(); /* wake_up_bit advises this */ 347 wake_up_bit(&si->flags, ilog2(SWP_DISCARDING)); 348 349 } else if (si->flags & SWP_DISCARDING) { 350 /* 351 * Delay using pages allocated by racing tasks 352 * until the whole discard has been issued. We 353 * could defer that delay until swap_writepage, 354 * but it's easier to keep this self-contained. 355 */ 356 spin_unlock(&swap_lock); 357 wait_on_bit(&si->flags, ilog2(SWP_DISCARDING), 358 wait_for_discard, TASK_UNINTERRUPTIBLE); 359 spin_lock(&swap_lock); 360 } else { 361 /* 362 * Note pages allocated by racing tasks while 363 * scan for a free cluster is in progress, so 364 * that its final discard can exclude them. 365 */ 366 if (offset < si->lowest_alloc) 367 si->lowest_alloc = offset; 368 if (offset > si->highest_alloc) 369 si->highest_alloc = offset; 370 } 371 } 372 return offset; 373 374scan: 375 spin_unlock(&swap_lock); 376 while (++offset <= si->highest_bit) { 377 if (!si->swap_map[offset]) { 378 spin_lock(&swap_lock); 379 goto checks; 380 } 381 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 382 spin_lock(&swap_lock); 383 goto checks; 384 } 385 if (unlikely(--latency_ration < 0)) { 386 cond_resched(); 387 latency_ration = LATENCY_LIMIT; 388 } 389 } 390 offset = si->lowest_bit; 391 while (++offset < scan_base) { 392 if (!si->swap_map[offset]) { 393 spin_lock(&swap_lock); 394 goto checks; 395 } 396 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 397 spin_lock(&swap_lock); 398 goto checks; 399 } 400 if (unlikely(--latency_ration < 0)) { 401 cond_resched(); 402 latency_ration = LATENCY_LIMIT; 403 } 404 } 405 spin_lock(&swap_lock); 406 407no_page: 408 si->flags -= SWP_SCANNING; 409 return 0; 410} 411 412swp_entry_t get_swap_page(void) 413{ 414 struct swap_info_struct *si; 415 pgoff_t offset; 416 int type, next; 417 int wrapped = 0; 418 419 spin_lock(&swap_lock); 420 if (nr_swap_pages <= 0) 421 goto noswap; 422 nr_swap_pages--; 423 424 for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { 425 si = swap_info[type]; 426 next = si->next; 427 if (next < 0 || 428 (!wrapped && si->prio != swap_info[next]->prio)) { 429 next = swap_list.head; 430 wrapped++; 431 } 432 433 if (!si->highest_bit) 434 continue; 435 if (!(si->flags & SWP_WRITEOK)) 436 continue; 437 438 swap_list.next = next; 439 /* This is called for allocating swap entry for cache */ 440 offset = scan_swap_map(si, SWAP_HAS_CACHE); 441 if (offset) { 442 spin_unlock(&swap_lock); 443 return swp_entry(type, offset); 444 } 445 next = swap_list.next; 446 } 447 448 nr_swap_pages++; 449noswap: 450 spin_unlock(&swap_lock); 451 return (swp_entry_t) {0}; 452} 453 454/* The only caller of this function is now susupend routine */ 455swp_entry_t get_swap_page_of_type(int type) 456{ 457 struct swap_info_struct *si; 458 pgoff_t offset; 459 460 spin_lock(&swap_lock); 461 si = swap_info[type]; 462 if (si && (si->flags & SWP_WRITEOK)) { 463 nr_swap_pages--; 464 /* This is called for allocating swap entry, not cache */ 465 offset = scan_swap_map(si, 1); 466 if (offset) { 467 spin_unlock(&swap_lock); 468 return swp_entry(type, offset); 469 } 470 nr_swap_pages++; 471 } 472 spin_unlock(&swap_lock); 473 return (swp_entry_t) {0}; 474} 475 476static struct swap_info_struct *swap_info_get(swp_entry_t entry) 477{ 478 struct swap_info_struct *p; 479 unsigned long offset, type; 480 481 if (!entry.val) 482 goto out; 483 type = swp_type(entry); 484 if (type >= nr_swapfiles) 485 goto bad_nofile; 486 p = swap_info[type]; 487 if (!(p->flags & SWP_USED)) 488 goto bad_device; 489 offset = swp_offset(entry); 490 if (offset >= p->max) 491 goto bad_offset; 492 if (!p->swap_map[offset]) 493 goto bad_free; 494 spin_lock(&swap_lock); 495 return p; 496 497bad_free: 498 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val); 499 goto out; 500bad_offset: 501 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val); 502 goto out; 503bad_device: 504 printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val); 505 goto out; 506bad_nofile: 507 printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val); 508out: 509 return NULL; 510} 511 512static unsigned char swap_entry_free(struct swap_info_struct *p, 513 swp_entry_t entry, unsigned char usage) 514{ 515 unsigned long offset = swp_offset(entry); 516 unsigned char count; 517 unsigned char has_cache; 518 519 count = p->swap_map[offset]; 520 has_cache = count & SWAP_HAS_CACHE; 521 count &= ~SWAP_HAS_CACHE; 522 523 if (usage == SWAP_HAS_CACHE) { 524 VM_BUG_ON(!has_cache); 525 has_cache = 0; 526 } else if (count == SWAP_MAP_SHMEM) { 527 /* 528 * Or we could insist on shmem.c using a special 529 * swap_shmem_free() and free_shmem_swap_and_cache()... 530 */ 531 count = 0; 532 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { 533 if (count == COUNT_CONTINUED) { 534 if (swap_count_continued(p, offset, count)) 535 count = SWAP_MAP_MAX | COUNT_CONTINUED; 536 else 537 count = SWAP_MAP_MAX; 538 } else 539 count--; 540 } 541 542 if (!count) 543 mem_cgroup_uncharge_swap(entry); 544 545 usage = count | has_cache; 546 p->swap_map[offset] = usage; 547 548 /* free if no reference */ 549 if (!usage) { 550 struct gendisk *disk = p->bdev->bd_disk; 551 if (offset < p->lowest_bit) 552 p->lowest_bit = offset; 553 if (offset > p->highest_bit) 554 p->highest_bit = offset; 555 if (swap_list.next >= 0 && 556 p->prio > swap_info[swap_list.next]->prio) 557 swap_list.next = p->type; 558 nr_swap_pages++; 559 p->inuse_pages--; 560 if ((p->flags & SWP_BLKDEV) && 561 disk->fops->swap_slot_free_notify) 562 disk->fops->swap_slot_free_notify(p->bdev, offset); 563 } 564 565 return usage; 566} 567 568/* 569 * Caller has made sure that the swapdevice corresponding to entry 570 * is still around or has not been recycled. 571 */ 572void swap_free(swp_entry_t entry) 573{ 574 struct swap_info_struct *p; 575 576 p = swap_info_get(entry); 577 if (p) { 578 swap_entry_free(p, entry, 1); 579 spin_unlock(&swap_lock); 580 } 581} 582 583/* 584 * Called after dropping swapcache to decrease refcnt to swap entries. 585 */ 586void swapcache_free(swp_entry_t entry, struct page *page) 587{ 588 struct swap_info_struct *p; 589 unsigned char count; 590 591 p = swap_info_get(entry); 592 if (p) { 593 count = swap_entry_free(p, entry, SWAP_HAS_CACHE); 594 if (page) 595 mem_cgroup_uncharge_swapcache(page, entry, count != 0); 596 spin_unlock(&swap_lock); 597 } 598} 599 600/* 601 * How many references to page are currently swapped out? 602 * This does not give an exact answer when swap count is continued, 603 * but does include the high COUNT_CONTINUED flag to allow for that. 604 */ 605static inline int page_swapcount(struct page *page) 606{ 607 int count = 0; 608 struct swap_info_struct *p; 609 swp_entry_t entry; 610 611 entry.val = page_private(page); 612 p = swap_info_get(entry); 613 if (p) { 614 count = swap_count(p->swap_map[swp_offset(entry)]); 615 spin_unlock(&swap_lock); 616 } 617 return count; 618} 619 620/* 621 * We can write to an anon page without COW if there are no other references 622 * to it. And as a side-effect, free up its swap: because the old content 623 * on disk will never be read, and seeking back there to write new content 624 * later would only waste time away from clustering. 625 */ 626int reuse_swap_page(struct page *page) 627{ 628 int count; 629 630 VM_BUG_ON(!PageLocked(page)); 631 if (unlikely(PageKsm(page))) 632 return 0; 633 count = page_mapcount(page); 634 if (count <= 1 && PageSwapCache(page)) { 635 count += page_swapcount(page); 636 if (count == 1 && !PageWriteback(page)) { 637 delete_from_swap_cache(page); 638 SetPageDirty(page); 639 } 640 } 641 return count <= 1; 642} 643 644/* 645 * If swap is getting full, or if there are no more mappings of this page, 646 * then try_to_free_swap is called to free its swap space. 647 */ 648int try_to_free_swap(struct page *page) 649{ 650 VM_BUG_ON(!PageLocked(page)); 651 652 if (!PageSwapCache(page)) 653 return 0; 654 if (PageWriteback(page)) 655 return 0; 656 if (page_swapcount(page)) 657 return 0; 658 659 /* 660 * Once hibernation has begun to create its image of memory, 661 * there's a danger that one of the calls to try_to_free_swap() 662 * - most probably a call from __try_to_reclaim_swap() while 663 * hibernation is allocating its own swap pages for the image, 664 * but conceivably even a call from memory reclaim - will free 665 * the swap from a page which has already been recorded in the 666 * image as a clean swapcache page, and then reuse its swap for 667 * another page of the image. On waking from hibernation, the 668 * original page might be freed under memory pressure, then 669 * later read back in from swap, now with the wrong data. 670 * 671 * Hibernation clears bits from gfp_allowed_mask to prevent 672 * memory reclaim from writing to disk, so check that here. 673 */ 674 if (!(gfp_allowed_mask & __GFP_IO)) 675 return 0; 676 677 delete_from_swap_cache(page); 678 SetPageDirty(page); 679 return 1; 680} 681 682/* 683 * Free the swap entry like above, but also try to 684 * free the page cache entry if it is the last user. 685 */ 686int free_swap_and_cache(swp_entry_t entry) 687{ 688 struct swap_info_struct *p; 689 struct page *page = NULL; 690 691 if (non_swap_entry(entry)) 692 return 1; 693 694 p = swap_info_get(entry); 695 if (p) { 696 if (swap_entry_free(p, entry, 1) == SWAP_HAS_CACHE) { 697 page = find_get_page(&swapper_space, entry.val); 698 if (page && !trylock_page(page)) { 699 page_cache_release(page); 700 page = NULL; 701 } 702 } 703 spin_unlock(&swap_lock); 704 } 705 if (page) { 706 /* 707 * Not mapped elsewhere, or swap space full? Free it! 708 * Also recheck PageSwapCache now page is locked (above). 709 */ 710 if (PageSwapCache(page) && !PageWriteback(page) && 711 (!page_mapped(page) || vm_swap_full())) { 712 delete_from_swap_cache(page); 713 SetPageDirty(page); 714 } 715 unlock_page(page); 716 page_cache_release(page); 717 } 718 return p != NULL; 719} 720 721#ifdef CONFIG_CGROUP_MEM_RES_CTLR 722/** 723 * mem_cgroup_count_swap_user - count the user of a swap entry 724 * @ent: the swap entry to be checked 725 * @pagep: the pointer for the swap cache page of the entry to be stored 726 * 727 * Returns the number of the user of the swap entry. The number is valid only 728 * for swaps of anonymous pages. 729 * If the entry is found on swap cache, the page is stored to pagep with 730 * refcount of it being incremented. 731 */ 732int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep) 733{ 734 struct page *page; 735 struct swap_info_struct *p; 736 int count = 0; 737 738 page = find_get_page(&swapper_space, ent.val); 739 if (page) 740 count += page_mapcount(page); 741 p = swap_info_get(ent); 742 if (p) { 743 count += swap_count(p->swap_map[swp_offset(ent)]); 744 spin_unlock(&swap_lock); 745 } 746 747 *pagep = page; 748 return count; 749} 750#endif 751 752#ifdef CONFIG_HIBERNATION 753/* 754 * Find the swap type that corresponds to given device (if any). 755 * 756 * @offset - number of the PAGE_SIZE-sized block of the device, starting 757 * from 0, in which the swap header is expected to be located. 758 * 759 * This is needed for the suspend to disk (aka swsusp). 760 */ 761int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p) 762{ 763 struct block_device *bdev = NULL; 764 int type; 765 766 if (device) 767 bdev = bdget(device); 768 769 spin_lock(&swap_lock); 770 for (type = 0; type < nr_swapfiles; type++) { 771 struct swap_info_struct *sis = swap_info[type]; 772 773 if (!(sis->flags & SWP_WRITEOK)) 774 continue; 775 776 if (!bdev) { 777 if (bdev_p) 778 *bdev_p = bdgrab(sis->bdev); 779 780 spin_unlock(&swap_lock); 781 return type; 782 } 783 if (bdev == sis->bdev) { 784 struct swap_extent *se = &sis->first_swap_extent; 785 786 if (se->start_block == offset) { 787 if (bdev_p) 788 *bdev_p = bdgrab(sis->bdev); 789 790 spin_unlock(&swap_lock); 791 bdput(bdev); 792 return type; 793 } 794 } 795 } 796 spin_unlock(&swap_lock); 797 if (bdev) 798 bdput(bdev); 799 800 return -ENODEV; 801} 802 803/* 804 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev 805 * corresponding to given index in swap_info (swap type). 806 */ 807sector_t swapdev_block(int type, pgoff_t offset) 808{ 809 struct block_device *bdev; 810 811 if ((unsigned int)type >= nr_swapfiles) 812 return 0; 813 if (!(swap_info[type]->flags & SWP_WRITEOK)) 814 return 0; 815 return map_swap_entry(swp_entry(type, offset), &bdev); 816} 817 818/* 819 * Return either the total number of swap pages of given type, or the number 820 * of free pages of that type (depending on @free) 821 * 822 * This is needed for software suspend 823 */ 824unsigned int count_swap_pages(int type, int free) 825{ 826 unsigned int n = 0; 827 828 spin_lock(&swap_lock); 829 if ((unsigned int)type < nr_swapfiles) { 830 struct swap_info_struct *sis = swap_info[type]; 831 832 if (sis->flags & SWP_WRITEOK) { 833 n = sis->pages; 834 if (free) 835 n -= sis->inuse_pages; 836 } 837 } 838 spin_unlock(&swap_lock); 839 return n; 840} 841#endif /* CONFIG_HIBERNATION */ 842 843/* 844 * No need to decide whether this PTE shares the swap entry with others, 845 * just let do_wp_page work it out if a write is requested later - to 846 * force COW, vm_page_prot omits write permission from any private vma. 847 */ 848static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, 849 unsigned long addr, swp_entry_t entry, struct page *page) 850{ 851 struct mem_cgroup *ptr; 852 spinlock_t *ptl; 853 pte_t *pte; 854 int ret = 1; 855 856 if (mem_cgroup_try_charge_swapin(vma->vm_mm, page, GFP_KERNEL, &ptr)) { 857 ret = -ENOMEM; 858 goto out_nolock; 859 } 860 861 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 862 if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) { 863 if (ret > 0) 864 mem_cgroup_cancel_charge_swapin(ptr); 865 ret = 0; 866 goto out; 867 } 868 869 dec_mm_counter(vma->vm_mm, MM_SWAPENTS); 870 inc_mm_counter(vma->vm_mm, MM_ANONPAGES); 871 get_page(page); 872 set_pte_at(vma->vm_mm, addr, pte, 873 pte_mkold(mk_pte(page, vma->vm_page_prot))); 874 page_add_anon_rmap(page, vma, addr); 875 mem_cgroup_commit_charge_swapin(page, ptr); 876 swap_free(entry); 877 /* 878 * Move the page to the active list so it is not 879 * immediately swapped out again after swapon. 880 */ 881 activate_page(page); 882out: 883 pte_unmap_unlock(pte, ptl); 884out_nolock: 885 return ret; 886} 887 888static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 889 unsigned long addr, unsigned long end, 890 swp_entry_t entry, struct page *page) 891{ 892 pte_t swp_pte = swp_entry_to_pte(entry); 893 pte_t *pte; 894 int ret = 0; 895 896 /* 897 * We don't actually need pte lock while scanning for swp_pte: since 898 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the 899 * page table while we're scanning; though it could get zapped, and on 900 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse 901 * of unmatched parts which look like swp_pte, so unuse_pte must 902 * recheck under pte lock. Scanning without pte lock lets it be 903 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE. 904 */ 905 pte = pte_offset_map(pmd, addr); 906 do { 907 /* 908 * swapoff spends a _lot_ of time in this loop! 909 * Test inline before going to call unuse_pte. 910 */ 911 if (unlikely(pte_same(*pte, swp_pte))) { 912 pte_unmap(pte); 913 ret = unuse_pte(vma, pmd, addr, entry, page); 914 if (ret) 915 goto out; 916 pte = pte_offset_map(pmd, addr); 917 } 918 } while (pte++, addr += PAGE_SIZE, addr != end); 919 pte_unmap(pte - 1); 920out: 921 return ret; 922} 923 924static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, 925 unsigned long addr, unsigned long end, 926 swp_entry_t entry, struct page *page) 927{ 928 pmd_t *pmd; 929 unsigned long next; 930 int ret; 931 932 pmd = pmd_offset(pud, addr); 933 do { 934 next = pmd_addr_end(addr, end); 935 if (unlikely(pmd_trans_huge(*pmd))) 936 continue; 937 if (pmd_none_or_clear_bad(pmd)) 938 continue; 939 ret = unuse_pte_range(vma, pmd, addr, next, entry, page); 940 if (ret) 941 return ret; 942 } while (pmd++, addr = next, addr != end); 943 return 0; 944} 945 946static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd, 947 unsigned long addr, unsigned long end, 948 swp_entry_t entry, struct page *page) 949{ 950 pud_t *pud; 951 unsigned long next; 952 int ret; 953 954 pud = pud_offset(pgd, addr); 955 do { 956 next = pud_addr_end(addr, end); 957 if (pud_none_or_clear_bad(pud)) 958 continue; 959 ret = unuse_pmd_range(vma, pud, addr, next, entry, page); 960 if (ret) 961 return ret; 962 } while (pud++, addr = next, addr != end); 963 return 0; 964} 965 966static int unuse_vma(struct vm_area_struct *vma, 967 swp_entry_t entry, struct page *page) 968{ 969 pgd_t *pgd; 970 unsigned long addr, end, next; 971 int ret; 972 973 if (page_anon_vma(page)) { 974 addr = page_address_in_vma(page, vma); 975 if (addr == -EFAULT) 976 return 0; 977 else 978 end = addr + PAGE_SIZE; 979 } else { 980 addr = vma->vm_start; 981 end = vma->vm_end; 982 } 983 984 pgd = pgd_offset(vma->vm_mm, addr); 985 do { 986 next = pgd_addr_end(addr, end); 987 if (pgd_none_or_clear_bad(pgd)) 988 continue; 989 ret = unuse_pud_range(vma, pgd, addr, next, entry, page); 990 if (ret) 991 return ret; 992 } while (pgd++, addr = next, addr != end); 993 return 0; 994} 995 996static int unuse_mm(struct mm_struct *mm, 997 swp_entry_t entry, struct page *page) 998{ 999 struct vm_area_struct *vma; 1000 int ret = 0; 1001 1002 if (!down_read_trylock(&mm->mmap_sem)) { 1003 /* 1004 * Activate page so shrink_inactive_list is unlikely to unmap 1005 * its ptes while lock is dropped, so swapoff can make progress. 1006 */ 1007 activate_page(page); 1008 unlock_page(page); 1009 down_read(&mm->mmap_sem); 1010 lock_page(page); 1011 } 1012 for (vma = mm->mmap; vma; vma = vma->vm_next) { 1013 if (vma->anon_vma && (ret = unuse_vma(vma, entry, page))) 1014 break; 1015 } 1016 up_read(&mm->mmap_sem); 1017 return (ret < 0)? ret: 0; 1018} 1019 1020/* 1021 * Scan swap_map from current position to next entry still in use. 1022 * Recycle to start on reaching the end, returning 0 when empty. 1023 */ 1024static unsigned int find_next_to_unuse(struct swap_info_struct *si, 1025 unsigned int prev) 1026{ 1027 unsigned int max = si->max; 1028 unsigned int i = prev; 1029 unsigned char count; 1030 1031 /* 1032 * No need for swap_lock here: we're just looking 1033 * for whether an entry is in use, not modifying it; false 1034 * hits are okay, and sys_swapoff() has already prevented new 1035 * allocations from this area (while holding swap_lock). 1036 */ 1037 for (;;) { 1038 if (++i >= max) { 1039 if (!prev) { 1040 i = 0; 1041 break; 1042 } 1043 /* 1044 * No entries in use at top of swap_map, 1045 * loop back to start and recheck there. 1046 */ 1047 max = prev + 1; 1048 prev = 0; 1049 i = 1; 1050 } 1051 count = si->swap_map[i]; 1052 if (count && swap_count(count) != SWAP_MAP_BAD) 1053 break; 1054 } 1055 return i; 1056} 1057 1058/* 1059 * We completely avoid races by reading each swap page in advance, 1060 * and then search for the process using it. All the necessary 1061 * page table adjustments can then be made atomically. 1062 */ 1063static int try_to_unuse(unsigned int type) 1064{ 1065 struct swap_info_struct *si = swap_info[type]; 1066 struct mm_struct *start_mm; 1067 unsigned char *swap_map; 1068 unsigned char swcount; 1069 struct page *page; 1070 swp_entry_t entry; 1071 unsigned int i = 0; 1072 int retval = 0; 1073 1074 /* 1075 * When searching mms for an entry, a good strategy is to 1076 * start at the first mm we freed the previous entry from 1077 * (though actually we don't notice whether we or coincidence 1078 * freed the entry). Initialize this start_mm with a hold. 1079 * 1080 * A simpler strategy would be to start at the last mm we 1081 * freed the previous entry from; but that would take less 1082 * advantage of mmlist ordering, which clusters forked mms 1083 * together, child after parent. If we race with dup_mmap(), we 1084 * prefer to resolve parent before child, lest we miss entries 1085 * duplicated after we scanned child: using last mm would invert 1086 * that. 1087 */ 1088 start_mm = &init_mm; 1089 atomic_inc(&init_mm.mm_users); 1090 1091 /* 1092 * Keep on scanning until all entries have gone. Usually, 1093 * one pass through swap_map is enough, but not necessarily: 1094 * there are races when an instance of an entry might be missed. 1095 */ 1096 while ((i = find_next_to_unuse(si, i)) != 0) { 1097 if (signal_pending(current)) { 1098 retval = -EINTR; 1099 break; 1100 } 1101 1102 /* 1103 * Get a page for the entry, using the existing swap 1104 * cache page if there is one. Otherwise, get a clean 1105 * page and read the swap into it. 1106 */ 1107 swap_map = &si->swap_map[i]; 1108 entry = swp_entry(type, i); 1109 page = read_swap_cache_async(entry, 1110 GFP_HIGHUSER_MOVABLE, NULL, 0); 1111 if (!page) { 1112 /* 1113 * Either swap_duplicate() failed because entry 1114 * has been freed independently, and will not be 1115 * reused since sys_swapoff() already disabled 1116 * allocation from here, or alloc_page() failed. 1117 */ 1118 if (!*swap_map) 1119 continue; 1120 retval = -ENOMEM; 1121 break; 1122 } 1123 1124 /* 1125 * Don't hold on to start_mm if it looks like exiting. 1126 */ 1127 if (atomic_read(&start_mm->mm_users) == 1) { 1128 mmput(start_mm); 1129 start_mm = &init_mm; 1130 atomic_inc(&init_mm.mm_users); 1131 } 1132 1133 /* 1134 * Wait for and lock page. When do_swap_page races with 1135 * try_to_unuse, do_swap_page can handle the fault much 1136 * faster than try_to_unuse can locate the entry. This 1137 * apparently redundant "wait_on_page_locked" lets try_to_unuse 1138 * defer to do_swap_page in such a case - in some tests, 1139 * do_swap_page and try_to_unuse repeatedly compete. 1140 */ 1141 wait_on_page_locked(page); 1142 wait_on_page_writeback(page); 1143 lock_page(page); 1144 wait_on_page_writeback(page); 1145 1146 /* 1147 * Remove all references to entry. 1148 */ 1149 swcount = *swap_map; 1150 if (swap_count(swcount) == SWAP_MAP_SHMEM) { 1151 retval = shmem_unuse(entry, page); 1152 /* page has already been unlocked and released */ 1153 if (retval < 0) 1154 break; 1155 continue; 1156 } 1157 if (swap_count(swcount) && start_mm != &init_mm) 1158 retval = unuse_mm(start_mm, entry, page); 1159 1160 if (swap_count(*swap_map)) { 1161 int set_start_mm = (*swap_map >= swcount); 1162 struct list_head *p = &start_mm->mmlist; 1163 struct mm_struct *new_start_mm = start_mm; 1164 struct mm_struct *prev_mm = start_mm; 1165 struct mm_struct *mm; 1166 1167 atomic_inc(&new_start_mm->mm_users); 1168 atomic_inc(&prev_mm->mm_users); 1169 spin_lock(&mmlist_lock); 1170 while (swap_count(*swap_map) && !retval && 1171 (p = p->next) != &start_mm->mmlist) { 1172 mm = list_entry(p, struct mm_struct, mmlist); 1173 if (!atomic_inc_not_zero(&mm->mm_users)) 1174 continue; 1175 spin_unlock(&mmlist_lock); 1176 mmput(prev_mm); 1177 prev_mm = mm; 1178 1179 cond_resched(); 1180 1181 swcount = *swap_map; 1182 if (!swap_count(swcount)) /* any usage ? */ 1183 ; 1184 else if (mm == &init_mm) 1185 set_start_mm = 1; 1186 else 1187 retval = unuse_mm(mm, entry, page); 1188 1189 if (set_start_mm && *swap_map < swcount) { 1190 mmput(new_start_mm); 1191 atomic_inc(&mm->mm_users); 1192 new_start_mm = mm; 1193 set_start_mm = 0; 1194 } 1195 spin_lock(&mmlist_lock); 1196 } 1197 spin_unlock(&mmlist_lock); 1198 mmput(prev_mm); 1199 mmput(start_mm); 1200 start_mm = new_start_mm; 1201 } 1202 if (retval) { 1203 unlock_page(page); 1204 page_cache_release(page); 1205 break; 1206 } 1207 1208 /* 1209 * If a reference remains (rare), we would like to leave 1210 * the page in the swap cache; but try_to_unmap could 1211 * then re-duplicate the entry once we drop page lock, 1212 * so we might loop indefinitely; also, that page could 1213 * not be swapped out to other storage meanwhile. So: 1214 * delete from cache even if there's another reference, 1215 * after ensuring that the data has been saved to disk - 1216 * since if the reference remains (rarer), it will be 1217 * read from disk into another page. Splitting into two 1218 * pages would be incorrect if swap supported "shared 1219 * private" pages, but they are handled by tmpfs files. 1220 * 1221 * Given how unuse_vma() targets one particular offset 1222 * in an anon_vma, once the anon_vma has been determined, 1223 * this splitting happens to be just what is needed to 1224 * handle where KSM pages have been swapped out: re-reading 1225 * is unnecessarily slow, but we can fix that later on. 1226 */ 1227 if (swap_count(*swap_map) && 1228 PageDirty(page) && PageSwapCache(page)) { 1229 struct writeback_control wbc = { 1230 .sync_mode = WB_SYNC_NONE, 1231 }; 1232 1233 swap_writepage(page, &wbc); 1234 lock_page(page); 1235 wait_on_page_writeback(page); 1236 } 1237 1238 /* 1239 * It is conceivable that a racing task removed this page from 1240 * swap cache just before we acquired the page lock at the top, 1241 * or while we dropped it in unuse_mm(). The page might even 1242 * be back in swap cache on another swap area: that we must not 1243 * delete, since it may not have been written out to swap yet. 1244 */ 1245 if (PageSwapCache(page) && 1246 likely(page_private(page) == entry.val)) 1247 delete_from_swap_cache(page); 1248 1249 /* 1250 * So we could skip searching mms once swap count went 1251 * to 1, we did not mark any present ptes as dirty: must 1252 * mark page dirty so shrink_page_list will preserve it. 1253 */ 1254 SetPageDirty(page); 1255 unlock_page(page); 1256 page_cache_release(page); 1257 1258 /* 1259 * Make sure that we aren't completely killing 1260 * interactive performance. 1261 */ 1262 cond_resched(); 1263 } 1264 1265 mmput(start_mm); 1266 return retval; 1267} 1268 1269/* 1270 * After a successful try_to_unuse, if no swap is now in use, we know 1271 * we can empty the mmlist. swap_lock must be held on entry and exit. 1272 * Note that mmlist_lock nests inside swap_lock, and an mm must be 1273 * added to the mmlist just after page_duplicate - before would be racy. 1274 */ 1275static void drain_mmlist(void) 1276{ 1277 struct list_head *p, *next; 1278 unsigned int type; 1279 1280 for (type = 0; type < nr_swapfiles; type++) 1281 if (swap_info[type]->inuse_pages) 1282 return; 1283 spin_lock(&mmlist_lock); 1284 list_for_each_safe(p, next, &init_mm.mmlist) 1285 list_del_init(p); 1286 spin_unlock(&mmlist_lock); 1287} 1288 1289/* 1290 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which 1291 * corresponds to page offset for the specified swap entry. 1292 * Note that the type of this function is sector_t, but it returns page offset 1293 * into the bdev, not sector offset. 1294 */ 1295static sector_t map_swap_entry(swp_entry_t entry, struct block_device **bdev) 1296{ 1297 struct swap_info_struct *sis; 1298 struct swap_extent *start_se; 1299 struct swap_extent *se; 1300 pgoff_t offset; 1301 1302 sis = swap_info[swp_type(entry)]; 1303 *bdev = sis->bdev; 1304 1305 offset = swp_offset(entry); 1306 start_se = sis->curr_swap_extent; 1307 se = start_se; 1308 1309 for ( ; ; ) { 1310 struct list_head *lh; 1311 1312 if (se->start_page <= offset && 1313 offset < (se->start_page + se->nr_pages)) { 1314 return se->start_block + (offset - se->start_page); 1315 } 1316 lh = se->list.next; 1317 se = list_entry(lh, struct swap_extent, list); 1318 sis->curr_swap_extent = se; 1319 BUG_ON(se == start_se); /* It *must* be present */ 1320 } 1321} 1322 1323/* 1324 * Returns the page offset into bdev for the specified page's swap entry. 1325 */ 1326sector_t map_swap_page(struct page *page, struct block_device **bdev) 1327{ 1328 swp_entry_t entry; 1329 entry.val = page_private(page); 1330 return map_swap_entry(entry, bdev); 1331} 1332 1333/* 1334 * Free all of a swapdev's extent information 1335 */ 1336static void destroy_swap_extents(struct swap_info_struct *sis) 1337{ 1338 while (!list_empty(&sis->first_swap_extent.list)) { 1339 struct swap_extent *se; 1340 1341 se = list_entry(sis->first_swap_extent.list.next, 1342 struct swap_extent, list); 1343 list_del(&se->list); 1344 kfree(se); 1345 } 1346} 1347 1348/* 1349 * Add a block range (and the corresponding page range) into this swapdev's 1350 * extent list. The extent list is kept sorted in page order. 1351 * 1352 * This function rather assumes that it is called in ascending page order. 1353 */ 1354static int 1355add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, 1356 unsigned long nr_pages, sector_t start_block) 1357{ 1358 struct swap_extent *se; 1359 struct swap_extent *new_se; 1360 struct list_head *lh; 1361 1362 if (start_page == 0) { 1363 se = &sis->first_swap_extent; 1364 sis->curr_swap_extent = se; 1365 se->start_page = 0; 1366 se->nr_pages = nr_pages; 1367 se->start_block = start_block; 1368 return 1; 1369 } else { 1370 lh = sis->first_swap_extent.list.prev; /* Highest extent */ 1371 se = list_entry(lh, struct swap_extent, list); 1372 BUG_ON(se->start_page + se->nr_pages != start_page); 1373 if (se->start_block + se->nr_pages == start_block) { 1374 /* Merge it */ 1375 se->nr_pages += nr_pages; 1376 return 0; 1377 } 1378 } 1379 1380 /* 1381 * No merge. Insert a new extent, preserving ordering. 1382 */ 1383 new_se = kmalloc(sizeof(*se), GFP_KERNEL); 1384 if (new_se == NULL) 1385 return -ENOMEM; 1386 new_se->start_page = start_page; 1387 new_se->nr_pages = nr_pages; 1388 new_se->start_block = start_block; 1389 1390 list_add_tail(&new_se->list, &sis->first_swap_extent.list); 1391 return 1; 1392} 1393 1394/* 1395 * A `swap extent' is a simple thing which maps a contiguous range of pages 1396 * onto a contiguous range of disk blocks. An ordered list of swap extents 1397 * is built at swapon time and is then used at swap_writepage/swap_readpage 1398 * time for locating where on disk a page belongs. 1399 * 1400 * If the swapfile is an S_ISBLK block device, a single extent is installed. 1401 * This is done so that the main operating code can treat S_ISBLK and S_ISREG 1402 * swap files identically. 1403 * 1404 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap 1405 * extent list operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK 1406 * swapfiles are handled *identically* after swapon time. 1407 * 1408 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks 1409 * and will parse them into an ordered extent list, in PAGE_SIZE chunks. If 1410 * some stray blocks are found which do not fall within the PAGE_SIZE alignment 1411 * requirements, they are simply tossed out - we will never use those blocks 1412 * for swapping. 1413 * 1414 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This 1415 * prevents root from shooting her foot off by ftruncating an in-use swapfile, 1416 * which will scribble on the fs. 1417 * 1418 * The amount of disk space which a single swap extent represents varies. 1419 * Typically it is in the 1-4 megabyte range. So we can have hundreds of 1420 * extents in the list. To avoid much list walking, we cache the previous 1421 * search location in `curr_swap_extent', and start new searches from there. 1422 * This is extremely effective. The average number of iterations in 1423 * map_swap_page() has been measured at about 0.3 per page. - akpm. 1424 */ 1425static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) 1426{ 1427 struct inode *inode; 1428 unsigned blocks_per_page; 1429 unsigned long page_no; 1430 unsigned blkbits; 1431 sector_t probe_block; 1432 sector_t last_block; 1433 sector_t lowest_block = -1; 1434 sector_t highest_block = 0; 1435 int nr_extents = 0; 1436 int ret; 1437 1438 inode = sis->swap_file->f_mapping->host; 1439 if (S_ISBLK(inode->i_mode)) { 1440 ret = add_swap_extent(sis, 0, sis->max, 0); 1441 *span = sis->pages; 1442 goto out; 1443 } 1444 1445 blkbits = inode->i_blkbits; 1446 blocks_per_page = PAGE_SIZE >> blkbits; 1447 1448 /* 1449 * Map all the blocks into the extent list. This code doesn't try 1450 * to be very smart. 1451 */ 1452 probe_block = 0; 1453 page_no = 0; 1454 last_block = i_size_read(inode) >> blkbits; 1455 while ((probe_block + blocks_per_page) <= last_block && 1456 page_no < sis->max) { 1457 unsigned block_in_page; 1458 sector_t first_block; 1459 1460 first_block = bmap(inode, probe_block); 1461 if (first_block == 0) 1462 goto bad_bmap; 1463 1464 /* 1465 * It must be PAGE_SIZE aligned on-disk 1466 */ 1467 if (first_block & (blocks_per_page - 1)) { 1468 probe_block++; 1469 goto reprobe; 1470 } 1471 1472 for (block_in_page = 1; block_in_page < blocks_per_page; 1473 block_in_page++) { 1474 sector_t block; 1475 1476 block = bmap(inode, probe_block + block_in_page); 1477 if (block == 0) 1478 goto bad_bmap; 1479 if (block != first_block + block_in_page) { 1480 /* Discontiguity */ 1481 probe_block++; 1482 goto reprobe; 1483 } 1484 } 1485 1486 first_block >>= (PAGE_SHIFT - blkbits); 1487 if (page_no) { /* exclude the header page */ 1488 if (first_block < lowest_block) 1489 lowest_block = first_block; 1490 if (first_block > highest_block) 1491 highest_block = first_block; 1492 } 1493 1494 /* 1495 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks 1496 */ 1497 ret = add_swap_extent(sis, page_no, 1, first_block); 1498 if (ret < 0) 1499 goto out; 1500 nr_extents += ret; 1501 page_no++; 1502 probe_block += blocks_per_page; 1503reprobe: 1504 continue; 1505 } 1506 ret = nr_extents; 1507 *span = 1 + highest_block - lowest_block; 1508 if (page_no == 0) 1509 page_no = 1; /* force Empty message */ 1510 sis->max = page_no; 1511 sis->pages = page_no - 1; 1512 sis->highest_bit = page_no - 1; 1513out: 1514 return ret; 1515bad_bmap: 1516 printk(KERN_ERR "swapon: swapfile has holes\n"); 1517 ret = -EINVAL; 1518 goto out; 1519} 1520 1521static void enable_swap_info(struct swap_info_struct *p, int prio, 1522 unsigned char *swap_map) 1523{ 1524 int i, prev; 1525 1526 spin_lock(&swap_lock); 1527 if (prio >= 0) 1528 p->prio = prio; 1529 else 1530 p->prio = --least_priority; 1531 p->swap_map = swap_map; 1532 p->flags |= SWP_WRITEOK; 1533 nr_swap_pages += p->pages; 1534 total_swap_pages += p->pages; 1535 1536 /* insert swap space into swap_list: */ 1537 prev = -1; 1538 for (i = swap_list.head; i >= 0; i = swap_info[i]->next) { 1539 if (p->prio >= swap_info[i]->prio) 1540 break; 1541 prev = i; 1542 } 1543 p->next = i; 1544 if (prev < 0) 1545 swap_list.head = swap_list.next = p->type; 1546 else 1547 swap_info[prev]->next = p->type; 1548 spin_unlock(&swap_lock); 1549} 1550 1551SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) 1552{ 1553 struct swap_info_struct *p = NULL; 1554 unsigned char *swap_map; 1555 struct file *swap_file, *victim; 1556 struct address_space *mapping; 1557 struct inode *inode; 1558 char *pathname; 1559 int oom_score_adj; 1560 int i, type, prev; 1561 int err; 1562 1563 if (!capable(CAP_SYS_ADMIN)) 1564 return -EPERM; 1565 1566 pathname = getname(specialfile); 1567 err = PTR_ERR(pathname); 1568 if (IS_ERR(pathname)) 1569 goto out; 1570 1571 victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0); 1572 putname(pathname); 1573 err = PTR_ERR(victim); 1574 if (IS_ERR(victim)) 1575 goto out; 1576 1577 mapping = victim->f_mapping; 1578 prev = -1; 1579 spin_lock(&swap_lock); 1580 for (type = swap_list.head; type >= 0; type = swap_info[type]->next) { 1581 p = swap_info[type]; 1582 if (p->flags & SWP_WRITEOK) { 1583 if (p->swap_file->f_mapping == mapping) 1584 break; 1585 } 1586 prev = type; 1587 } 1588 if (type < 0) { 1589 err = -EINVAL; 1590 spin_unlock(&swap_lock); 1591 goto out_dput; 1592 } 1593 if (!security_vm_enough_memory(p->pages)) 1594 vm_unacct_memory(p->pages); 1595 else { 1596 err = -ENOMEM; 1597 spin_unlock(&swap_lock); 1598 goto out_dput; 1599 } 1600 if (prev < 0) 1601 swap_list.head = p->next; 1602 else 1603 swap_info[prev]->next = p->next; 1604 if (type == swap_list.next) { 1605 /* just pick something that's safe... */ 1606 swap_list.next = swap_list.head; 1607 } 1608 if (p->prio < 0) { 1609 for (i = p->next; i >= 0; i = swap_info[i]->next) 1610 swap_info[i]->prio = p->prio--; 1611 least_priority++; 1612 } 1613 nr_swap_pages -= p->pages; 1614 total_swap_pages -= p->pages; 1615 p->flags &= ~SWP_WRITEOK; 1616 spin_unlock(&swap_lock); 1617 1618 oom_score_adj = test_set_oom_score_adj(OOM_SCORE_ADJ_MAX); 1619 err = try_to_unuse(type); 1620 test_set_oom_score_adj(oom_score_adj); 1621 1622 if (err) { 1623 /* 1624 * reading p->prio and p->swap_map outside the lock is 1625 * safe here because only sys_swapon and sys_swapoff 1626 * change them, and there can be no other sys_swapon or 1627 * sys_swapoff for this swap_info_struct at this point. 1628 */ 1629 /* re-insert swap space back into swap_list */ 1630 enable_swap_info(p, p->prio, p->swap_map); 1631 goto out_dput; 1632 } 1633 1634 destroy_swap_extents(p); 1635 if (p->flags & SWP_CONTINUED) 1636 free_swap_count_continuations(p); 1637 1638 mutex_lock(&swapon_mutex); 1639 spin_lock(&swap_lock); 1640 drain_mmlist(); 1641 1642 /* wait for anyone still in scan_swap_map */ 1643 p->highest_bit = 0; /* cuts scans short */ 1644 while (p->flags >= SWP_SCANNING) { 1645 spin_unlock(&swap_lock); 1646 schedule_timeout_uninterruptible(1); 1647 spin_lock(&swap_lock); 1648 } 1649 1650 swap_file = p->swap_file; 1651 p->swap_file = NULL; 1652 p->max = 0; 1653 swap_map = p->swap_map; 1654 p->swap_map = NULL; 1655 p->flags = 0; 1656 spin_unlock(&swap_lock); 1657 mutex_unlock(&swapon_mutex); 1658 vfree(swap_map); 1659 /* Destroy swap account informatin */ 1660 swap_cgroup_swapoff(type); 1661 1662 inode = mapping->host; 1663 if (S_ISBLK(inode->i_mode)) { 1664 struct block_device *bdev = I_BDEV(inode); 1665 set_blocksize(bdev, p->old_block_size); 1666 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); 1667 } else { 1668 mutex_lock(&inode->i_mutex); 1669 inode->i_flags &= ~S_SWAPFILE; 1670 mutex_unlock(&inode->i_mutex); 1671 } 1672 filp_close(swap_file, NULL); 1673 err = 0; 1674 atomic_inc(&proc_poll_event); 1675 wake_up_interruptible(&proc_poll_wait); 1676 1677out_dput: 1678 filp_close(victim, NULL); 1679out: 1680 return err; 1681} 1682 1683#ifdef CONFIG_PROC_FS 1684struct proc_swaps { 1685 struct seq_file seq; 1686 int event; 1687}; 1688 1689static unsigned swaps_poll(struct file *file, poll_table *wait) 1690{ 1691 struct proc_swaps *s = file->private_data; 1692 1693 poll_wait(file, &proc_poll_wait, wait); 1694 1695 if (s->event != atomic_read(&proc_poll_event)) { 1696 s->event = atomic_read(&proc_poll_event); 1697 return POLLIN | POLLRDNORM | POLLERR | POLLPRI; 1698 } 1699 1700 return POLLIN | POLLRDNORM; 1701} 1702 1703/* iterator */ 1704static void *swap_start(struct seq_file *swap, loff_t *pos) 1705{ 1706 struct swap_info_struct *si; 1707 int type; 1708 loff_t l = *pos; 1709 1710 mutex_lock(&swapon_mutex); 1711 1712 if (!l) 1713 return SEQ_START_TOKEN; 1714 1715 for (type = 0; type < nr_swapfiles; type++) { 1716 smp_rmb(); /* read nr_swapfiles before swap_info[type] */ 1717 si = swap_info[type]; 1718 if (!(si->flags & SWP_USED) || !si->swap_map) 1719 continue; 1720 if (!--l) 1721 return si; 1722 } 1723 1724 return NULL; 1725} 1726 1727static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) 1728{ 1729 struct swap_info_struct *si = v; 1730 int type; 1731 1732 if (v == SEQ_START_TOKEN) 1733 type = 0; 1734 else 1735 type = si->type + 1; 1736 1737 for (; 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 ++*pos; 1743 return si; 1744 } 1745 1746 return NULL; 1747} 1748 1749static void swap_stop(struct seq_file *swap, void *v) 1750{ 1751 mutex_unlock(&swapon_mutex); 1752} 1753 1754static int swap_show(struct seq_file *swap, void *v) 1755{ 1756 struct swap_info_struct *si = v; 1757 struct file *file; 1758 int len; 1759 1760 if (si == SEQ_START_TOKEN) { 1761 seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n"); 1762 return 0; 1763 } 1764 1765 file = si->swap_file; 1766 len = seq_path(swap, &file->f_path, " \t\n\\"); 1767 seq_printf(swap, "%*s%s\t%u\t%u\t%d\n", 1768 len < 40 ? 40 - len : 1, " ", 1769 S_ISBLK(file->f_path.dentry->d_inode->i_mode) ? 1770 "partition" : "file\t", 1771 si->pages << (PAGE_SHIFT - 10), 1772 si->inuse_pages << (PAGE_SHIFT - 10), 1773 si->prio); 1774 return 0; 1775} 1776 1777static const struct seq_operations swaps_op = { 1778 .start = swap_start, 1779 .next = swap_next, 1780 .stop = swap_stop, 1781 .show = swap_show 1782}; 1783 1784static int swaps_open(struct inode *inode, struct file *file) 1785{ 1786 struct proc_swaps *s; 1787 int ret; 1788 1789 s = kmalloc(sizeof(struct proc_swaps), GFP_KERNEL); 1790 if (!s) 1791 return -ENOMEM; 1792 1793 file->private_data = s; 1794 1795 ret = seq_open(file, &swaps_op); 1796 if (ret) { 1797 kfree(s); 1798 return ret; 1799 } 1800 1801 s->seq.private = s; 1802 s->event = atomic_read(&proc_poll_event); 1803 return ret; 1804} 1805 1806static const struct file_operations proc_swaps_operations = { 1807 .open = swaps_open, 1808 .read = seq_read, 1809 .llseek = seq_lseek, 1810 .release = seq_release, 1811 .poll = swaps_poll, 1812}; 1813 1814static int __init procswaps_init(void) 1815{ 1816 proc_create("swaps", 0, NULL, &proc_swaps_operations); 1817 return 0; 1818} 1819__initcall(procswaps_init); 1820#endif /* CONFIG_PROC_FS */ 1821 1822#ifdef MAX_SWAPFILES_CHECK 1823static int __init max_swapfiles_check(void) 1824{ 1825 MAX_SWAPFILES_CHECK(); 1826 return 0; 1827} 1828late_initcall(max_swapfiles_check); 1829#endif 1830 1831static struct swap_info_struct *alloc_swap_info(void) 1832{ 1833 struct swap_info_struct *p; 1834 unsigned int type; 1835 1836 p = kzalloc(sizeof(*p), GFP_KERNEL); 1837 if (!p) 1838 return ERR_PTR(-ENOMEM); 1839 1840 spin_lock(&swap_lock); 1841 for (type = 0; type < nr_swapfiles; type++) { 1842 if (!(swap_info[type]->flags & SWP_USED)) 1843 break; 1844 } 1845 if (type >= MAX_SWAPFILES) { 1846 spin_unlock(&swap_lock); 1847 kfree(p); 1848 return ERR_PTR(-EPERM); 1849 } 1850 if (type >= nr_swapfiles) { 1851 p->type = type; 1852 swap_info[type] = p; 1853 /* 1854 * Write swap_info[type] before nr_swapfiles, in case a 1855 * racing procfs swap_start() or swap_next() is reading them. 1856 * (We never shrink nr_swapfiles, we never free this entry.) 1857 */ 1858 smp_wmb(); 1859 nr_swapfiles++; 1860 } else { 1861 kfree(p); 1862 p = swap_info[type]; 1863 /* 1864 * Do not memset this entry: a racing procfs swap_next() 1865 * would be relying on p->type to remain valid. 1866 */ 1867 } 1868 INIT_LIST_HEAD(&p->first_swap_extent.list); 1869 p->flags = SWP_USED; 1870 p->next = -1; 1871 spin_unlock(&swap_lock); 1872 1873 return p; 1874} 1875 1876static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) 1877{ 1878 int error; 1879 1880 if (S_ISBLK(inode->i_mode)) { 1881 p->bdev = bdgrab(I_BDEV(inode)); 1882 error = blkdev_get(p->bdev, 1883 FMODE_READ | FMODE_WRITE | FMODE_EXCL, 1884 sys_swapon); 1885 if (error < 0) { 1886 p->bdev = NULL; 1887 return -EINVAL; 1888 } 1889 p->old_block_size = block_size(p->bdev); 1890 error = set_blocksize(p->bdev, PAGE_SIZE); 1891 if (error < 0) 1892 return error; 1893 p->flags |= SWP_BLKDEV; 1894 } else if (S_ISREG(inode->i_mode)) { 1895 p->bdev = inode->i_sb->s_bdev; 1896 mutex_lock(&inode->i_mutex); 1897 if (IS_SWAPFILE(inode)) 1898 return -EBUSY; 1899 } else 1900 return -EINVAL; 1901 1902 return 0; 1903} 1904 1905static unsigned long read_swap_header(struct swap_info_struct *p, 1906 union swap_header *swap_header, 1907 struct inode *inode) 1908{ 1909 int i; 1910 unsigned long maxpages; 1911 unsigned long swapfilepages; 1912 1913 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { 1914 printk(KERN_ERR "Unable to find swap-space signature\n"); 1915 return 0; 1916 } 1917 1918 /* swap partition endianess hack... */ 1919 if (swab32(swap_header->info.version) == 1) { 1920 swab32s(&swap_header->info.version); 1921 swab32s(&swap_header->info.last_page); 1922 swab32s(&swap_header->info.nr_badpages); 1923 for (i = 0; i < swap_header->info.nr_badpages; i++) 1924 swab32s(&swap_header->info.badpages[i]); 1925 } 1926 /* Check the swap header's sub-version */ 1927 if (swap_header->info.version != 1) { 1928 printk(KERN_WARNING 1929 "Unable to handle swap header version %d\n", 1930 swap_header->info.version); 1931 return 0; 1932 } 1933 1934 p->lowest_bit = 1; 1935 p->cluster_next = 1; 1936 p->cluster_nr = 0; 1937 1938 /* 1939 * Find out how many pages are allowed for a single swap 1940 * device. There are two limiting factors: 1) the number of 1941 * bits for the swap offset in the swp_entry_t type and 1942 * 2) the number of bits in the a swap pte as defined by 1943 * the different architectures. In order to find the 1944 * largest possible bit mask a swap entry with swap type 0 1945 * and swap offset ~0UL is created, encoded to a swap pte, 1946 * decoded to a swp_entry_t again and finally the swap 1947 * offset is extracted. This will mask all the bits from 1948 * the initial ~0UL mask that can't be encoded in either 1949 * the swp_entry_t or the architecture definition of a 1950 * swap pte. 1951 */ 1952 maxpages = swp_offset(pte_to_swp_entry( 1953 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; 1954 if (maxpages > swap_header->info.last_page) { 1955 maxpages = swap_header->info.last_page + 1; 1956 /* p->max is an unsigned int: don't overflow it */ 1957 if ((unsigned int)maxpages == 0) 1958 maxpages = UINT_MAX; 1959 } 1960 p->highest_bit = maxpages - 1; 1961 1962 if (!maxpages) 1963 return 0; 1964 swapfilepages = i_size_read(inode) >> PAGE_SHIFT; 1965 if (swapfilepages && maxpages > swapfilepages) { 1966 printk(KERN_WARNING 1967 "Swap area shorter than signature indicates\n"); 1968 return 0; 1969 } 1970 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) 1971 return 0; 1972 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) 1973 return 0; 1974 1975 return maxpages; 1976} 1977 1978static int setup_swap_map_and_extents(struct swap_info_struct *p, 1979 union swap_header *swap_header, 1980 unsigned char *swap_map, 1981 unsigned long maxpages, 1982 sector_t *span) 1983{ 1984 int i; 1985 unsigned int nr_good_pages; 1986 int nr_extents; 1987 1988 nr_good_pages = maxpages - 1; /* omit header page */ 1989 1990 for (i = 0; i < swap_header->info.nr_badpages; i++) { 1991 unsigned int page_nr = swap_header->info.badpages[i]; 1992 if (page_nr == 0 || page_nr > swap_header->info.last_page) 1993 return -EINVAL; 1994 if (page_nr < maxpages) { 1995 swap_map[page_nr] = SWAP_MAP_BAD; 1996 nr_good_pages--; 1997 } 1998 } 1999 2000 if (nr_good_pages) { 2001 swap_map[0] = SWAP_MAP_BAD; 2002 p->max = maxpages; 2003 p->pages = nr_good_pages; 2004 nr_extents = setup_swap_extents(p, span); 2005 if (nr_extents < 0) 2006 return nr_extents; 2007 nr_good_pages = p->pages; 2008 } 2009 if (!nr_good_pages) { 2010 printk(KERN_WARNING "Empty swap-file\n"); 2011 return -EINVAL; 2012 } 2013 2014 return nr_extents; 2015} 2016 2017SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 2018{ 2019 struct swap_info_struct *p; 2020 char *name; 2021 struct file *swap_file = NULL; 2022 struct address_space *mapping; 2023 int i; 2024 int prio; 2025 int error; 2026 union swap_header *swap_header; 2027 int nr_extents; 2028 sector_t span; 2029 unsigned long maxpages; 2030 unsigned char *swap_map = NULL; 2031 struct page *page = NULL; 2032 struct inode *inode = NULL; 2033 2034 if (!capable(CAP_SYS_ADMIN)) 2035 return -EPERM; 2036 2037 p = alloc_swap_info(); 2038 if (IS_ERR(p)) 2039 return PTR_ERR(p); 2040 2041 name = getname(specialfile); 2042 if (IS_ERR(name)) { 2043 error = PTR_ERR(name); 2044 name = NULL; 2045 goto bad_swap; 2046 } 2047 swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0); 2048 if (IS_ERR(swap_file)) { 2049 error = PTR_ERR(swap_file); 2050 swap_file = NULL; 2051 goto bad_swap; 2052 } 2053 2054 p->swap_file = swap_file; 2055 mapping = swap_file->f_mapping; 2056 2057 for (i = 0; i < nr_swapfiles; i++) { 2058 struct swap_info_struct *q = swap_info[i]; 2059 2060 if (q == p || !q->swap_file) 2061 continue; 2062 if (mapping == q->swap_file->f_mapping) { 2063 error = -EBUSY; 2064 goto bad_swap; 2065 } 2066 } 2067 2068 inode = mapping->host; 2069 /* If S_ISREG(inode->i_mode) will do mutex_lock(&inode->i_mutex); */ 2070 error = claim_swapfile(p, inode); 2071 if (unlikely(error)) 2072 goto bad_swap; 2073 2074 /* 2075 * Read the swap header. 2076 */ 2077 if (!mapping->a_ops->readpage) { 2078 error = -EINVAL; 2079 goto bad_swap; 2080 } 2081 page = read_mapping_page(mapping, 0, swap_file); 2082 if (IS_ERR(page)) { 2083 error = PTR_ERR(page); 2084 goto bad_swap; 2085 } 2086 swap_header = kmap(page); 2087 2088 maxpages = read_swap_header(p, swap_header, inode); 2089 if (unlikely(!maxpages)) { 2090 error = -EINVAL; 2091 goto bad_swap; 2092 } 2093 2094 /* OK, set up the swap map and apply the bad block list */ 2095 swap_map = vzalloc(maxpages); 2096 if (!swap_map) { 2097 error = -ENOMEM; 2098 goto bad_swap; 2099 } 2100 2101 error = swap_cgroup_swapon(p->type, maxpages); 2102 if (error) 2103 goto bad_swap; 2104 2105 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map, 2106 maxpages, &span); 2107 if (unlikely(nr_extents < 0)) { 2108 error = nr_extents; 2109 goto bad_swap; 2110 } 2111 2112 if (p->bdev) { 2113 if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { 2114 p->flags |= SWP_SOLIDSTATE; 2115 p->cluster_next = 1 + (random32() % p->highest_bit); 2116 } 2117 if (discard_swap(p) == 0 && (swap_flags & SWAP_FLAG_DISCARD)) 2118 p->flags |= SWP_DISCARDABLE; 2119 } 2120 2121 mutex_lock(&swapon_mutex); 2122 prio = -1; 2123 if (swap_flags & SWAP_FLAG_PREFER) 2124 prio = 2125 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; 2126 enable_swap_info(p, prio, swap_map); 2127 2128 printk(KERN_INFO "Adding %uk swap on %s. " 2129 "Priority:%d extents:%d across:%lluk %s%s\n", 2130 p->pages<<(PAGE_SHIFT-10), name, p->prio, 2131 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10), 2132 (p->flags & SWP_SOLIDSTATE) ? "SS" : "", 2133 (p->flags & SWP_DISCARDABLE) ? "D" : ""); 2134 2135 mutex_unlock(&swapon_mutex); 2136 atomic_inc(&proc_poll_event); 2137 wake_up_interruptible(&proc_poll_wait); 2138 2139 if (S_ISREG(inode->i_mode)) 2140 inode->i_flags |= S_SWAPFILE; 2141 error = 0; 2142 goto out; 2143bad_swap: 2144 if (inode && S_ISBLK(inode->i_mode) && p->bdev) { 2145 set_blocksize(p->bdev, p->old_block_size); 2146 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); 2147 } 2148 destroy_swap_extents(p); 2149 swap_cgroup_swapoff(p->type); 2150 spin_lock(&swap_lock); 2151 p->swap_file = NULL; 2152 p->flags = 0; 2153 spin_unlock(&swap_lock); 2154 vfree(swap_map); 2155 if (swap_file) { 2156 if (inode && S_ISREG(inode->i_mode)) { 2157 mutex_unlock(&inode->i_mutex); 2158 inode = NULL; 2159 } 2160 filp_close(swap_file, NULL); 2161 } 2162out: 2163 if (page && !IS_ERR(page)) { 2164 kunmap(page); 2165 page_cache_release(page); 2166 } 2167 if (name) 2168 putname(name); 2169 if (inode && S_ISREG(inode->i_mode)) 2170 mutex_unlock(&inode->i_mutex); 2171 return error; 2172} 2173 2174void si_swapinfo(struct sysinfo *val) 2175{ 2176 unsigned int type; 2177 unsigned long nr_to_be_unused = 0; 2178 2179 spin_lock(&swap_lock); 2180 for (type = 0; type < nr_swapfiles; type++) { 2181 struct swap_info_struct *si = swap_info[type]; 2182 2183 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) 2184 nr_to_be_unused += si->inuse_pages; 2185 } 2186 val->freeswap = nr_swap_pages + nr_to_be_unused; 2187 val->totalswap = total_swap_pages + nr_to_be_unused; 2188 spin_unlock(&swap_lock); 2189} 2190 2191/* 2192 * Verify that a swap entry is valid and increment its swap map count. 2193 * 2194 * Returns error code in following case. 2195 * - success -> 0 2196 * - swp_entry is invalid -> EINVAL 2197 * - swp_entry is migration entry -> EINVAL 2198 * - swap-cache reference is requested but there is already one. -> EEXIST 2199 * - swap-cache reference is requested but the entry is not used. -> ENOENT 2200 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM 2201 */ 2202static int __swap_duplicate(swp_entry_t entry, unsigned char usage) 2203{ 2204 struct swap_info_struct *p; 2205 unsigned long offset, type; 2206 unsigned char count; 2207 unsigned char has_cache; 2208 int err = -EINVAL; 2209 2210 if (non_swap_entry(entry)) 2211 goto out; 2212 2213 type = swp_type(entry); 2214 if (type >= nr_swapfiles) 2215 goto bad_file; 2216 p = swap_info[type]; 2217 offset = swp_offset(entry); 2218 2219 spin_lock(&swap_lock); 2220 if (unlikely(offset >= p->max)) 2221 goto unlock_out; 2222 2223 count = p->swap_map[offset]; 2224 has_cache = count & SWAP_HAS_CACHE; 2225 count &= ~SWAP_HAS_CACHE; 2226 err = 0; 2227 2228 if (usage == SWAP_HAS_CACHE) { 2229 2230 /* set SWAP_HAS_CACHE if there is no cache and entry is used */ 2231 if (!has_cache && count) 2232 has_cache = SWAP_HAS_CACHE; 2233 else if (has_cache) /* someone else added cache */ 2234 err = -EEXIST; 2235 else /* no users remaining */ 2236 err = -ENOENT; 2237 2238 } else if (count || has_cache) { 2239 2240 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) 2241 count += usage; 2242 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) 2243 err = -EINVAL; 2244 else if (swap_count_continued(p, offset, count)) 2245 count = COUNT_CONTINUED; 2246 else 2247 err = -ENOMEM; 2248 } else 2249 err = -ENOENT; /* unused swap entry */ 2250 2251 p->swap_map[offset] = count | has_cache; 2252 2253unlock_out: 2254 spin_unlock(&swap_lock); 2255out: 2256 return err; 2257 2258bad_file: 2259 printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val); 2260 goto out; 2261} 2262 2263/* 2264 * Help swapoff by noting that swap entry belongs to shmem/tmpfs 2265 * (in which case its reference count is never incremented). 2266 */ 2267void swap_shmem_alloc(swp_entry_t entry) 2268{ 2269 __swap_duplicate(entry, SWAP_MAP_SHMEM); 2270} 2271 2272/* 2273 * Increase reference count of swap entry by 1. 2274 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required 2275 * but could not be atomically allocated. Returns 0, just as if it succeeded, 2276 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which 2277 * might occur if a page table entry has got corrupted. 2278 */ 2279int swap_duplicate(swp_entry_t entry) 2280{ 2281 int err = 0; 2282 2283 while (!err && __swap_duplicate(entry, 1) == -ENOMEM) 2284 err = add_swap_count_continuation(entry, GFP_ATOMIC); 2285 return err; 2286} 2287 2288/* 2289 * @entry: swap entry for which we allocate swap cache. 2290 * 2291 * Called when allocating swap cache for existing swap entry, 2292 * This can return error codes. Returns 0 at success. 2293 * -EBUSY means there is a swap cache. 2294 * Note: return code is different from swap_duplicate(). 2295 */ 2296int swapcache_prepare(swp_entry_t entry) 2297{ 2298 return __swap_duplicate(entry, SWAP_HAS_CACHE); 2299} 2300 2301/* 2302 * swap_lock prevents swap_map being freed. Don't grab an extra 2303 * reference on the swaphandle, it doesn't matter if it becomes unused. 2304 */ 2305int valid_swaphandles(swp_entry_t entry, unsigned long *offset) 2306{ 2307 struct swap_info_struct *si; 2308 int our_page_cluster = page_cluster; 2309 pgoff_t target, toff; 2310 pgoff_t base, end; 2311 int nr_pages = 0; 2312 2313 if (!our_page_cluster) /* no readahead */ 2314 return 0; 2315 2316 si = swap_info[swp_type(entry)]; 2317 target = swp_offset(entry); 2318 base = (target >> our_page_cluster) << our_page_cluster; 2319 end = base + (1 << our_page_cluster); 2320 if (!base) /* first page is swap header */ 2321 base++; 2322 2323 spin_lock(&swap_lock); 2324 if (end > si->max) /* don't go beyond end of map */ 2325 end = si->max; 2326 2327 /* Count contiguous allocated slots above our target */ 2328 for (toff = target; ++toff < end; nr_pages++) { 2329 /* Don't read in free or bad pages */ 2330 if (!si->swap_map[toff]) 2331 break; 2332 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) 2333 break; 2334 } 2335 /* Count contiguous allocated slots below our target */ 2336 for (toff = target; --toff >= base; nr_pages++) { 2337 /* Don't read in free or bad pages */ 2338 if (!si->swap_map[toff]) 2339 break; 2340 if (swap_count(si->swap_map[toff]) == SWAP_MAP_BAD) 2341 break; 2342 } 2343 spin_unlock(&swap_lock); 2344 2345 /* 2346 * Indicate starting offset, and return number of pages to get: 2347 * if only 1, say 0, since there's then no readahead to be done. 2348 */ 2349 *offset = ++toff; 2350 return nr_pages? ++nr_pages: 0; 2351} 2352 2353/* 2354 * add_swap_count_continuation - called when a swap count is duplicated 2355 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's 2356 * page of the original vmalloc'ed swap_map, to hold the continuation count 2357 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called 2358 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc. 2359 * 2360 * These continuation pages are seldom referenced: the common paths all work 2361 * on the original swap_map, only referring to a continuation page when the 2362 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX. 2363 * 2364 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding 2365 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL) 2366 * can be called after dropping locks. 2367 */ 2368int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask) 2369{ 2370 struct swap_info_struct *si; 2371 struct page *head; 2372 struct page *page; 2373 struct page *list_page; 2374 pgoff_t offset; 2375 unsigned char count; 2376 2377 /* 2378 * When debugging, it's easier to use __GFP_ZERO here; but it's better 2379 * for latency not to zero a page while GFP_ATOMIC and holding locks. 2380 */ 2381 page = alloc_page(gfp_mask | __GFP_HIGHMEM); 2382 2383 si = swap_info_get(entry); 2384 if (!si) { 2385 /* 2386 * An acceptable race has occurred since the failing 2387 * __swap_duplicate(): the swap entry has been freed, 2388 * perhaps even the whole swap_map cleared for swapoff. 2389 */ 2390 goto outer; 2391 } 2392 2393 offset = swp_offset(entry); 2394 count = si->swap_map[offset] & ~SWAP_HAS_CACHE; 2395 2396 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) { 2397 /* 2398 * The higher the swap count, the more likely it is that tasks 2399 * will race to add swap count continuation: we need to avoid 2400 * over-provisioning. 2401 */ 2402 goto out; 2403 } 2404 2405 if (!page) { 2406 spin_unlock(&swap_lock); 2407 return -ENOMEM; 2408 } 2409 2410 /* 2411 * We are fortunate that although vmalloc_to_page uses pte_offset_map, 2412 * no architecture is using highmem pages for kernel pagetables: so it 2413 * will not corrupt the GFP_ATOMIC caller's atomic pagetable kmaps. 2414 */ 2415 head = vmalloc_to_page(si->swap_map + offset); 2416 offset &= ~PAGE_MASK; 2417 2418 /* 2419 * Page allocation does not initialize the page's lru field, 2420 * but it does always reset its private field. 2421 */ 2422 if (!page_private(head)) { 2423 BUG_ON(count & COUNT_CONTINUED); 2424 INIT_LIST_HEAD(&head->lru); 2425 set_page_private(head, SWP_CONTINUED); 2426 si->flags |= SWP_CONTINUED; 2427 } 2428 2429 list_for_each_entry(list_page, &head->lru, lru) { 2430 unsigned char *map; 2431 2432 /* 2433 * If the previous map said no continuation, but we've found 2434 * a continuation page, free our allocation and use this one. 2435 */ 2436 if (!(count & COUNT_CONTINUED)) 2437 goto out; 2438 2439 map = kmap_atomic(list_page, KM_USER0) + offset; 2440 count = *map; 2441 kunmap_atomic(map, KM_USER0); 2442 2443 /* 2444 * If this continuation count now has some space in it, 2445 * free our allocation and use this one. 2446 */ 2447 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX) 2448 goto out; 2449 } 2450 2451 list_add_tail(&page->lru, &head->lru); 2452 page = NULL; /* now it's attached, don't free it */ 2453out: 2454 spin_unlock(&swap_lock); 2455outer: 2456 if (page) 2457 __free_page(page); 2458 return 0; 2459} 2460 2461/* 2462 * swap_count_continued - when the original swap_map count is incremented 2463 * from SWAP_MAP_MAX, check if there is already a continuation page to carry 2464 * into, carry if so, or else fail until a new continuation page is allocated; 2465 * when the original swap_map count is decremented from 0 with continuation, 2466 * borrow from the continuation and report whether it still holds more. 2467 * Called while __swap_duplicate() or swap_entry_free() holds swap_lock. 2468 */ 2469static bool swap_count_continued(struct swap_info_struct *si, 2470 pgoff_t offset, unsigned char count) 2471{ 2472 struct page *head; 2473 struct page *page; 2474 unsigned char *map; 2475 2476 head = vmalloc_to_page(si->swap_map + offset); 2477 if (page_private(head) != SWP_CONTINUED) { 2478 BUG_ON(count & COUNT_CONTINUED); 2479 return false; /* need to add count continuation */ 2480 } 2481 2482 offset &= ~PAGE_MASK; 2483 page = list_entry(head->lru.next, struct page, lru); 2484 map = kmap_atomic(page, KM_USER0) + offset; 2485 2486 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ 2487 goto init_map; /* jump over SWAP_CONT_MAX checks */ 2488 2489 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */ 2490 /* 2491 * Think of how you add 1 to 999 2492 */ 2493 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { 2494 kunmap_atomic(map, KM_USER0); 2495 page = list_entry(page->lru.next, struct page, lru); 2496 BUG_ON(page == head); 2497 map = kmap_atomic(page, KM_USER0) + offset; 2498 } 2499 if (*map == SWAP_CONT_MAX) { 2500 kunmap_atomic(map, KM_USER0); 2501 page = list_entry(page->lru.next, struct page, lru); 2502 if (page == head) 2503 return false; /* add count continuation */ 2504 map = kmap_atomic(page, KM_USER0) + offset; 2505init_map: *map = 0; /* we didn't zero the page */ 2506 } 2507 *map += 1; 2508 kunmap_atomic(map, KM_USER0); 2509 page = list_entry(page->lru.prev, struct page, lru); 2510 while (page != head) { 2511 map = kmap_atomic(page, KM_USER0) + offset; 2512 *map = COUNT_CONTINUED; 2513 kunmap_atomic(map, KM_USER0); 2514 page = list_entry(page->lru.prev, struct page, lru); 2515 } 2516 return true; /* incremented */ 2517 2518 } else { /* decrementing */ 2519 /* 2520 * Think of how you subtract 1 from 1000 2521 */ 2522 BUG_ON(count != COUNT_CONTINUED); 2523 while (*map == COUNT_CONTINUED) { 2524 kunmap_atomic(map, KM_USER0); 2525 page = list_entry(page->lru.next, struct page, lru); 2526 BUG_ON(page == head); 2527 map = kmap_atomic(page, KM_USER0) + offset; 2528 } 2529 BUG_ON(*map == 0); 2530 *map -= 1; 2531 if (*map == 0) 2532 count = 0; 2533 kunmap_atomic(map, KM_USER0); 2534 page = list_entry(page->lru.prev, struct page, lru); 2535 while (page != head) { 2536 map = kmap_atomic(page, KM_USER0) + offset; 2537 *map = SWAP_CONT_MAX | count; 2538 count = COUNT_CONTINUED; 2539 kunmap_atomic(map, KM_USER0); 2540 page = list_entry(page->lru.prev, struct page, lru); 2541 } 2542 return count == COUNT_CONTINUED; 2543 } 2544} 2545 2546/* 2547 * free_swap_count_continuations - swapoff free all the continuation pages 2548 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it. 2549 */ 2550static void free_swap_count_continuations(struct swap_info_struct *si) 2551{ 2552 pgoff_t offset; 2553 2554 for (offset = 0; offset < si->max; offset += PAGE_SIZE) { 2555 struct page *head; 2556 head = vmalloc_to_page(si->swap_map + offset); 2557 if (page_private(head)) { 2558 struct list_head *this, *next; 2559 list_for_each_safe(this, next, &head->lru) { 2560 struct page *page; 2561 page = list_entry(this, struct page, lru); 2562 list_del(this); 2563 __free_page(page); 2564 } 2565 } 2566 } 2567} 2568