1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/mm/swapfile.c 4 * 5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 6 * Swap reorganised 29.12.95, Stephen Tweedie 7 */ 8 9 #include <linux/blkdev.h> 10 #include <linux/mm.h> 11 #include <linux/sched/mm.h> 12 #include <linux/sched/task.h> 13 #include <linux/hugetlb.h> 14 #include <linux/mman.h> 15 #include <linux/slab.h> 16 #include <linux/kernel_stat.h> 17 #include <linux/swap.h> 18 #include <linux/vmalloc.h> 19 #include <linux/pagemap.h> 20 #include <linux/namei.h> 21 #include <linux/shmem_fs.h> 22 #include <linux/blk-cgroup.h> 23 #include <linux/random.h> 24 #include <linux/writeback.h> 25 #include <linux/proc_fs.h> 26 #include <linux/seq_file.h> 27 #include <linux/init.h> 28 #include <linux/ksm.h> 29 #include <linux/rmap.h> 30 #include <linux/security.h> 31 #include <linux/backing-dev.h> 32 #include <linux/mutex.h> 33 #include <linux/capability.h> 34 #include <linux/syscalls.h> 35 #include <linux/memcontrol.h> 36 #include <linux/poll.h> 37 #include <linux/oom.h> 38 #include <linux/frontswap.h> 39 #include <linux/swapfile.h> 40 #include <linux/export.h> 41 #include <linux/swap_slots.h> 42 #include <linux/sort.h> 43 #include <linux/completion.h> 44 45 #include <asm/tlbflush.h> 46 #include <linux/swapops.h> 47 #include <linux/swap_cgroup.h> 48 #include "swap.h" 49 50 static bool swap_count_continued(struct swap_info_struct *, pgoff_t, 51 unsigned char); 52 static void free_swap_count_continuations(struct swap_info_struct *); 53 54 static DEFINE_SPINLOCK(swap_lock); 55 static unsigned int nr_swapfiles; 56 atomic_long_t nr_swap_pages; 57 /* 58 * Some modules use swappable objects and may try to swap them out under 59 * memory pressure (via the shrinker). Before doing so, they may wish to 60 * check to see if any swap space is available. 61 */ 62 EXPORT_SYMBOL_GPL(nr_swap_pages); 63 /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */ 64 long total_swap_pages; 65 static int least_priority = -1; 66 unsigned long swapfile_maximum_size; 67 #ifdef CONFIG_MIGRATION 68 bool swap_migration_ad_supported; 69 #endif /* CONFIG_MIGRATION */ 70 71 static const char Bad_file[] = "Bad swap file entry "; 72 static const char Unused_file[] = "Unused swap file entry "; 73 static const char Bad_offset[] = "Bad swap offset entry "; 74 static const char Unused_offset[] = "Unused swap offset entry "; 75 76 /* 77 * all active swap_info_structs 78 * protected with swap_lock, and ordered by priority. 79 */ 80 static PLIST_HEAD(swap_active_head); 81 82 /* 83 * all available (active, not full) swap_info_structs 84 * protected with swap_avail_lock, ordered by priority. 85 * This is used by folio_alloc_swap() instead of swap_active_head 86 * because swap_active_head includes all swap_info_structs, 87 * but folio_alloc_swap() doesn't need to look at full ones. 88 * This uses its own lock instead of swap_lock because when a 89 * swap_info_struct changes between not-full/full, it needs to 90 * add/remove itself to/from this list, but the swap_info_struct->lock 91 * is held and the locking order requires swap_lock to be taken 92 * before any swap_info_struct->lock. 93 */ 94 static struct plist_head *swap_avail_heads; 95 static DEFINE_SPINLOCK(swap_avail_lock); 96 97 struct swap_info_struct *swap_info[MAX_SWAPFILES]; 98 99 static DEFINE_MUTEX(swapon_mutex); 100 101 static DECLARE_WAIT_QUEUE_HEAD(proc_poll_wait); 102 /* Activity counter to indicate that a swapon or swapoff has occurred */ 103 static atomic_t proc_poll_event = ATOMIC_INIT(0); 104 105 atomic_t nr_rotate_swap = ATOMIC_INIT(0); 106 107 static struct swap_info_struct *swap_type_to_swap_info(int type) 108 { 109 if (type >= MAX_SWAPFILES) 110 return NULL; 111 112 return READ_ONCE(swap_info[type]); /* rcu_dereference() */ 113 } 114 115 static inline unsigned char swap_count(unsigned char ent) 116 { 117 return ent & ~SWAP_HAS_CACHE; /* may include COUNT_CONTINUED flag */ 118 } 119 120 /* Reclaim the swap entry anyway if possible */ 121 #define TTRS_ANYWAY 0x1 122 /* 123 * Reclaim the swap entry if there are no more mappings of the 124 * corresponding page 125 */ 126 #define TTRS_UNMAPPED 0x2 127 /* Reclaim the swap entry if swap is getting full*/ 128 #define TTRS_FULL 0x4 129 130 /* returns 1 if swap entry is freed */ 131 static int __try_to_reclaim_swap(struct swap_info_struct *si, 132 unsigned long offset, unsigned long flags) 133 { 134 swp_entry_t entry = swp_entry(si->type, offset); 135 struct folio *folio; 136 int ret = 0; 137 138 folio = filemap_get_folio(swap_address_space(entry), offset); 139 if (!folio) 140 return 0; 141 /* 142 * When this function is called from scan_swap_map_slots() and it's 143 * called by vmscan.c at reclaiming folios. So we hold a folio lock 144 * here. We have to use trylock for avoiding deadlock. This is a special 145 * case and you should use folio_free_swap() with explicit folio_lock() 146 * in usual operations. 147 */ 148 if (folio_trylock(folio)) { 149 if ((flags & TTRS_ANYWAY) || 150 ((flags & TTRS_UNMAPPED) && !folio_mapped(folio)) || 151 ((flags & TTRS_FULL) && mem_cgroup_swap_full(folio))) 152 ret = folio_free_swap(folio); 153 folio_unlock(folio); 154 } 155 folio_put(folio); 156 return ret; 157 } 158 159 static inline struct swap_extent *first_se(struct swap_info_struct *sis) 160 { 161 struct rb_node *rb = rb_first(&sis->swap_extent_root); 162 return rb_entry(rb, struct swap_extent, rb_node); 163 } 164 165 static inline struct swap_extent *next_se(struct swap_extent *se) 166 { 167 struct rb_node *rb = rb_next(&se->rb_node); 168 return rb ? rb_entry(rb, struct swap_extent, rb_node) : NULL; 169 } 170 171 /* 172 * swapon tell device that all the old swap contents can be discarded, 173 * to allow the swap device to optimize its wear-levelling. 174 */ 175 static int discard_swap(struct swap_info_struct *si) 176 { 177 struct swap_extent *se; 178 sector_t start_block; 179 sector_t nr_blocks; 180 int err = 0; 181 182 /* Do not discard the swap header page! */ 183 se = first_se(si); 184 start_block = (se->start_block + 1) << (PAGE_SHIFT - 9); 185 nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9); 186 if (nr_blocks) { 187 err = blkdev_issue_discard(si->bdev, start_block, 188 nr_blocks, GFP_KERNEL); 189 if (err) 190 return err; 191 cond_resched(); 192 } 193 194 for (se = next_se(se); se; se = next_se(se)) { 195 start_block = se->start_block << (PAGE_SHIFT - 9); 196 nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9); 197 198 err = blkdev_issue_discard(si->bdev, start_block, 199 nr_blocks, GFP_KERNEL); 200 if (err) 201 break; 202 203 cond_resched(); 204 } 205 return err; /* That will often be -EOPNOTSUPP */ 206 } 207 208 static struct swap_extent * 209 offset_to_swap_extent(struct swap_info_struct *sis, unsigned long offset) 210 { 211 struct swap_extent *se; 212 struct rb_node *rb; 213 214 rb = sis->swap_extent_root.rb_node; 215 while (rb) { 216 se = rb_entry(rb, struct swap_extent, rb_node); 217 if (offset < se->start_page) 218 rb = rb->rb_left; 219 else if (offset >= se->start_page + se->nr_pages) 220 rb = rb->rb_right; 221 else 222 return se; 223 } 224 /* It *must* be present */ 225 BUG(); 226 } 227 228 sector_t swap_page_sector(struct page *page) 229 { 230 struct swap_info_struct *sis = page_swap_info(page); 231 struct swap_extent *se; 232 sector_t sector; 233 pgoff_t offset; 234 235 offset = __page_file_index(page); 236 se = offset_to_swap_extent(sis, offset); 237 sector = se->start_block + (offset - se->start_page); 238 return sector << (PAGE_SHIFT - 9); 239 } 240 241 /* 242 * swap allocation tell device that a cluster of swap can now be discarded, 243 * to allow the swap device to optimize its wear-levelling. 244 */ 245 static void discard_swap_cluster(struct swap_info_struct *si, 246 pgoff_t start_page, pgoff_t nr_pages) 247 { 248 struct swap_extent *se = offset_to_swap_extent(si, start_page); 249 250 while (nr_pages) { 251 pgoff_t offset = start_page - se->start_page; 252 sector_t start_block = se->start_block + offset; 253 sector_t nr_blocks = se->nr_pages - offset; 254 255 if (nr_blocks > nr_pages) 256 nr_blocks = nr_pages; 257 start_page += nr_blocks; 258 nr_pages -= nr_blocks; 259 260 start_block <<= PAGE_SHIFT - 9; 261 nr_blocks <<= PAGE_SHIFT - 9; 262 if (blkdev_issue_discard(si->bdev, start_block, 263 nr_blocks, GFP_NOIO)) 264 break; 265 266 se = next_se(se); 267 } 268 } 269 270 #ifdef CONFIG_THP_SWAP 271 #define SWAPFILE_CLUSTER HPAGE_PMD_NR 272 273 #define swap_entry_size(size) (size) 274 #else 275 #define SWAPFILE_CLUSTER 256 276 277 /* 278 * Define swap_entry_size() as constant to let compiler to optimize 279 * out some code if !CONFIG_THP_SWAP 280 */ 281 #define swap_entry_size(size) 1 282 #endif 283 #define LATENCY_LIMIT 256 284 285 static inline void cluster_set_flag(struct swap_cluster_info *info, 286 unsigned int flag) 287 { 288 info->flags = flag; 289 } 290 291 static inline unsigned int cluster_count(struct swap_cluster_info *info) 292 { 293 return info->data; 294 } 295 296 static inline void cluster_set_count(struct swap_cluster_info *info, 297 unsigned int c) 298 { 299 info->data = c; 300 } 301 302 static inline void cluster_set_count_flag(struct swap_cluster_info *info, 303 unsigned int c, unsigned int f) 304 { 305 info->flags = f; 306 info->data = c; 307 } 308 309 static inline unsigned int cluster_next(struct swap_cluster_info *info) 310 { 311 return info->data; 312 } 313 314 static inline void cluster_set_next(struct swap_cluster_info *info, 315 unsigned int n) 316 { 317 info->data = n; 318 } 319 320 static inline void cluster_set_next_flag(struct swap_cluster_info *info, 321 unsigned int n, unsigned int f) 322 { 323 info->flags = f; 324 info->data = n; 325 } 326 327 static inline bool cluster_is_free(struct swap_cluster_info *info) 328 { 329 return info->flags & CLUSTER_FLAG_FREE; 330 } 331 332 static inline bool cluster_is_null(struct swap_cluster_info *info) 333 { 334 return info->flags & CLUSTER_FLAG_NEXT_NULL; 335 } 336 337 static inline void cluster_set_null(struct swap_cluster_info *info) 338 { 339 info->flags = CLUSTER_FLAG_NEXT_NULL; 340 info->data = 0; 341 } 342 343 static inline bool cluster_is_huge(struct swap_cluster_info *info) 344 { 345 if (IS_ENABLED(CONFIG_THP_SWAP)) 346 return info->flags & CLUSTER_FLAG_HUGE; 347 return false; 348 } 349 350 static inline void cluster_clear_huge(struct swap_cluster_info *info) 351 { 352 info->flags &= ~CLUSTER_FLAG_HUGE; 353 } 354 355 static inline struct swap_cluster_info *lock_cluster(struct swap_info_struct *si, 356 unsigned long offset) 357 { 358 struct swap_cluster_info *ci; 359 360 ci = si->cluster_info; 361 if (ci) { 362 ci += offset / SWAPFILE_CLUSTER; 363 spin_lock(&ci->lock); 364 } 365 return ci; 366 } 367 368 static inline void unlock_cluster(struct swap_cluster_info *ci) 369 { 370 if (ci) 371 spin_unlock(&ci->lock); 372 } 373 374 /* 375 * Determine the locking method in use for this device. Return 376 * swap_cluster_info if SSD-style cluster-based locking is in place. 377 */ 378 static inline struct swap_cluster_info *lock_cluster_or_swap_info( 379 struct swap_info_struct *si, unsigned long offset) 380 { 381 struct swap_cluster_info *ci; 382 383 /* Try to use fine-grained SSD-style locking if available: */ 384 ci = lock_cluster(si, offset); 385 /* Otherwise, fall back to traditional, coarse locking: */ 386 if (!ci) 387 spin_lock(&si->lock); 388 389 return ci; 390 } 391 392 static inline void unlock_cluster_or_swap_info(struct swap_info_struct *si, 393 struct swap_cluster_info *ci) 394 { 395 if (ci) 396 unlock_cluster(ci); 397 else 398 spin_unlock(&si->lock); 399 } 400 401 static inline bool cluster_list_empty(struct swap_cluster_list *list) 402 { 403 return cluster_is_null(&list->head); 404 } 405 406 static inline unsigned int cluster_list_first(struct swap_cluster_list *list) 407 { 408 return cluster_next(&list->head); 409 } 410 411 static void cluster_list_init(struct swap_cluster_list *list) 412 { 413 cluster_set_null(&list->head); 414 cluster_set_null(&list->tail); 415 } 416 417 static void cluster_list_add_tail(struct swap_cluster_list *list, 418 struct swap_cluster_info *ci, 419 unsigned int idx) 420 { 421 if (cluster_list_empty(list)) { 422 cluster_set_next_flag(&list->head, idx, 0); 423 cluster_set_next_flag(&list->tail, idx, 0); 424 } else { 425 struct swap_cluster_info *ci_tail; 426 unsigned int tail = cluster_next(&list->tail); 427 428 /* 429 * Nested cluster lock, but both cluster locks are 430 * only acquired when we held swap_info_struct->lock 431 */ 432 ci_tail = ci + tail; 433 spin_lock_nested(&ci_tail->lock, SINGLE_DEPTH_NESTING); 434 cluster_set_next(ci_tail, idx); 435 spin_unlock(&ci_tail->lock); 436 cluster_set_next_flag(&list->tail, idx, 0); 437 } 438 } 439 440 static unsigned int cluster_list_del_first(struct swap_cluster_list *list, 441 struct swap_cluster_info *ci) 442 { 443 unsigned int idx; 444 445 idx = cluster_next(&list->head); 446 if (cluster_next(&list->tail) == idx) { 447 cluster_set_null(&list->head); 448 cluster_set_null(&list->tail); 449 } else 450 cluster_set_next_flag(&list->head, 451 cluster_next(&ci[idx]), 0); 452 453 return idx; 454 } 455 456 /* Add a cluster to discard list and schedule it to do discard */ 457 static void swap_cluster_schedule_discard(struct swap_info_struct *si, 458 unsigned int idx) 459 { 460 /* 461 * If scan_swap_map_slots() can't find a free cluster, it will check 462 * si->swap_map directly. To make sure the discarding cluster isn't 463 * taken by scan_swap_map_slots(), mark the swap entries bad (occupied). 464 * It will be cleared after discard 465 */ 466 memset(si->swap_map + idx * SWAPFILE_CLUSTER, 467 SWAP_MAP_BAD, SWAPFILE_CLUSTER); 468 469 cluster_list_add_tail(&si->discard_clusters, si->cluster_info, idx); 470 471 schedule_work(&si->discard_work); 472 } 473 474 static void __free_cluster(struct swap_info_struct *si, unsigned long idx) 475 { 476 struct swap_cluster_info *ci = si->cluster_info; 477 478 cluster_set_flag(ci + idx, CLUSTER_FLAG_FREE); 479 cluster_list_add_tail(&si->free_clusters, ci, idx); 480 } 481 482 /* 483 * Doing discard actually. After a cluster discard is finished, the cluster 484 * will be added to free cluster list. caller should hold si->lock. 485 */ 486 static void swap_do_scheduled_discard(struct swap_info_struct *si) 487 { 488 struct swap_cluster_info *info, *ci; 489 unsigned int idx; 490 491 info = si->cluster_info; 492 493 while (!cluster_list_empty(&si->discard_clusters)) { 494 idx = cluster_list_del_first(&si->discard_clusters, info); 495 spin_unlock(&si->lock); 496 497 discard_swap_cluster(si, idx * SWAPFILE_CLUSTER, 498 SWAPFILE_CLUSTER); 499 500 spin_lock(&si->lock); 501 ci = lock_cluster(si, idx * SWAPFILE_CLUSTER); 502 __free_cluster(si, idx); 503 memset(si->swap_map + idx * SWAPFILE_CLUSTER, 504 0, SWAPFILE_CLUSTER); 505 unlock_cluster(ci); 506 } 507 } 508 509 static void swap_discard_work(struct work_struct *work) 510 { 511 struct swap_info_struct *si; 512 513 si = container_of(work, struct swap_info_struct, discard_work); 514 515 spin_lock(&si->lock); 516 swap_do_scheduled_discard(si); 517 spin_unlock(&si->lock); 518 } 519 520 static void swap_users_ref_free(struct percpu_ref *ref) 521 { 522 struct swap_info_struct *si; 523 524 si = container_of(ref, struct swap_info_struct, users); 525 complete(&si->comp); 526 } 527 528 static void alloc_cluster(struct swap_info_struct *si, unsigned long idx) 529 { 530 struct swap_cluster_info *ci = si->cluster_info; 531 532 VM_BUG_ON(cluster_list_first(&si->free_clusters) != idx); 533 cluster_list_del_first(&si->free_clusters, ci); 534 cluster_set_count_flag(ci + idx, 0, 0); 535 } 536 537 static void free_cluster(struct swap_info_struct *si, unsigned long idx) 538 { 539 struct swap_cluster_info *ci = si->cluster_info + idx; 540 541 VM_BUG_ON(cluster_count(ci) != 0); 542 /* 543 * If the swap is discardable, prepare discard the cluster 544 * instead of free it immediately. The cluster will be freed 545 * after discard. 546 */ 547 if ((si->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) == 548 (SWP_WRITEOK | SWP_PAGE_DISCARD)) { 549 swap_cluster_schedule_discard(si, idx); 550 return; 551 } 552 553 __free_cluster(si, idx); 554 } 555 556 /* 557 * The cluster corresponding to page_nr will be used. The cluster will be 558 * removed from free cluster list and its usage counter will be increased. 559 */ 560 static void inc_cluster_info_page(struct swap_info_struct *p, 561 struct swap_cluster_info *cluster_info, unsigned long page_nr) 562 { 563 unsigned long idx = page_nr / SWAPFILE_CLUSTER; 564 565 if (!cluster_info) 566 return; 567 if (cluster_is_free(&cluster_info[idx])) 568 alloc_cluster(p, idx); 569 570 VM_BUG_ON(cluster_count(&cluster_info[idx]) >= SWAPFILE_CLUSTER); 571 cluster_set_count(&cluster_info[idx], 572 cluster_count(&cluster_info[idx]) + 1); 573 } 574 575 /* 576 * The cluster corresponding to page_nr decreases one usage. If the usage 577 * counter becomes 0, which means no page in the cluster is in using, we can 578 * optionally discard the cluster and add it to free cluster list. 579 */ 580 static void dec_cluster_info_page(struct swap_info_struct *p, 581 struct swap_cluster_info *cluster_info, unsigned long page_nr) 582 { 583 unsigned long idx = page_nr / SWAPFILE_CLUSTER; 584 585 if (!cluster_info) 586 return; 587 588 VM_BUG_ON(cluster_count(&cluster_info[idx]) == 0); 589 cluster_set_count(&cluster_info[idx], 590 cluster_count(&cluster_info[idx]) - 1); 591 592 if (cluster_count(&cluster_info[idx]) == 0) 593 free_cluster(p, idx); 594 } 595 596 /* 597 * It's possible scan_swap_map_slots() uses a free cluster in the middle of free 598 * cluster list. Avoiding such abuse to avoid list corruption. 599 */ 600 static bool 601 scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si, 602 unsigned long offset) 603 { 604 struct percpu_cluster *percpu_cluster; 605 bool conflict; 606 607 offset /= SWAPFILE_CLUSTER; 608 conflict = !cluster_list_empty(&si->free_clusters) && 609 offset != cluster_list_first(&si->free_clusters) && 610 cluster_is_free(&si->cluster_info[offset]); 611 612 if (!conflict) 613 return false; 614 615 percpu_cluster = this_cpu_ptr(si->percpu_cluster); 616 cluster_set_null(&percpu_cluster->index); 617 return true; 618 } 619 620 /* 621 * Try to get a swap entry from current cpu's swap entry pool (a cluster). This 622 * might involve allocating a new cluster for current CPU too. 623 */ 624 static bool scan_swap_map_try_ssd_cluster(struct swap_info_struct *si, 625 unsigned long *offset, unsigned long *scan_base) 626 { 627 struct percpu_cluster *cluster; 628 struct swap_cluster_info *ci; 629 unsigned long tmp, max; 630 631 new_cluster: 632 cluster = this_cpu_ptr(si->percpu_cluster); 633 if (cluster_is_null(&cluster->index)) { 634 if (!cluster_list_empty(&si->free_clusters)) { 635 cluster->index = si->free_clusters.head; 636 cluster->next = cluster_next(&cluster->index) * 637 SWAPFILE_CLUSTER; 638 } else if (!cluster_list_empty(&si->discard_clusters)) { 639 /* 640 * we don't have free cluster but have some clusters in 641 * discarding, do discard now and reclaim them, then 642 * reread cluster_next_cpu since we dropped si->lock 643 */ 644 swap_do_scheduled_discard(si); 645 *scan_base = this_cpu_read(*si->cluster_next_cpu); 646 *offset = *scan_base; 647 goto new_cluster; 648 } else 649 return false; 650 } 651 652 /* 653 * Other CPUs can use our cluster if they can't find a free cluster, 654 * check if there is still free entry in the cluster 655 */ 656 tmp = cluster->next; 657 max = min_t(unsigned long, si->max, 658 (cluster_next(&cluster->index) + 1) * SWAPFILE_CLUSTER); 659 if (tmp < max) { 660 ci = lock_cluster(si, tmp); 661 while (tmp < max) { 662 if (!si->swap_map[tmp]) 663 break; 664 tmp++; 665 } 666 unlock_cluster(ci); 667 } 668 if (tmp >= max) { 669 cluster_set_null(&cluster->index); 670 goto new_cluster; 671 } 672 cluster->next = tmp + 1; 673 *offset = tmp; 674 *scan_base = tmp; 675 return true; 676 } 677 678 static void __del_from_avail_list(struct swap_info_struct *p) 679 { 680 int nid; 681 682 for_each_node(nid) 683 plist_del(&p->avail_lists[nid], &swap_avail_heads[nid]); 684 } 685 686 static void del_from_avail_list(struct swap_info_struct *p) 687 { 688 spin_lock(&swap_avail_lock); 689 __del_from_avail_list(p); 690 spin_unlock(&swap_avail_lock); 691 } 692 693 static void swap_range_alloc(struct swap_info_struct *si, unsigned long offset, 694 unsigned int nr_entries) 695 { 696 unsigned int end = offset + nr_entries - 1; 697 698 if (offset == si->lowest_bit) 699 si->lowest_bit += nr_entries; 700 if (end == si->highest_bit) 701 WRITE_ONCE(si->highest_bit, si->highest_bit - nr_entries); 702 WRITE_ONCE(si->inuse_pages, si->inuse_pages + nr_entries); 703 if (si->inuse_pages == si->pages) { 704 si->lowest_bit = si->max; 705 si->highest_bit = 0; 706 del_from_avail_list(si); 707 } 708 } 709 710 static void add_to_avail_list(struct swap_info_struct *p) 711 { 712 int nid; 713 714 spin_lock(&swap_avail_lock); 715 for_each_node(nid) { 716 WARN_ON(!plist_node_empty(&p->avail_lists[nid])); 717 plist_add(&p->avail_lists[nid], &swap_avail_heads[nid]); 718 } 719 spin_unlock(&swap_avail_lock); 720 } 721 722 static void swap_range_free(struct swap_info_struct *si, unsigned long offset, 723 unsigned int nr_entries) 724 { 725 unsigned long begin = offset; 726 unsigned long end = offset + nr_entries - 1; 727 void (*swap_slot_free_notify)(struct block_device *, unsigned long); 728 729 if (offset < si->lowest_bit) 730 si->lowest_bit = offset; 731 if (end > si->highest_bit) { 732 bool was_full = !si->highest_bit; 733 734 WRITE_ONCE(si->highest_bit, end); 735 if (was_full && (si->flags & SWP_WRITEOK)) 736 add_to_avail_list(si); 737 } 738 atomic_long_add(nr_entries, &nr_swap_pages); 739 WRITE_ONCE(si->inuse_pages, si->inuse_pages - nr_entries); 740 if (si->flags & SWP_BLKDEV) 741 swap_slot_free_notify = 742 si->bdev->bd_disk->fops->swap_slot_free_notify; 743 else 744 swap_slot_free_notify = NULL; 745 while (offset <= end) { 746 arch_swap_invalidate_page(si->type, offset); 747 frontswap_invalidate_page(si->type, offset); 748 if (swap_slot_free_notify) 749 swap_slot_free_notify(si->bdev, offset); 750 offset++; 751 } 752 clear_shadow_from_swap_cache(si->type, begin, end); 753 } 754 755 static void set_cluster_next(struct swap_info_struct *si, unsigned long next) 756 { 757 unsigned long prev; 758 759 if (!(si->flags & SWP_SOLIDSTATE)) { 760 si->cluster_next = next; 761 return; 762 } 763 764 prev = this_cpu_read(*si->cluster_next_cpu); 765 /* 766 * Cross the swap address space size aligned trunk, choose 767 * another trunk randomly to avoid lock contention on swap 768 * address space if possible. 769 */ 770 if ((prev >> SWAP_ADDRESS_SPACE_SHIFT) != 771 (next >> SWAP_ADDRESS_SPACE_SHIFT)) { 772 /* No free swap slots available */ 773 if (si->highest_bit <= si->lowest_bit) 774 return; 775 next = si->lowest_bit + 776 prandom_u32_max(si->highest_bit - si->lowest_bit + 1); 777 next = ALIGN_DOWN(next, SWAP_ADDRESS_SPACE_PAGES); 778 next = max_t(unsigned int, next, si->lowest_bit); 779 } 780 this_cpu_write(*si->cluster_next_cpu, next); 781 } 782 783 static bool swap_offset_available_and_locked(struct swap_info_struct *si, 784 unsigned long offset) 785 { 786 if (data_race(!si->swap_map[offset])) { 787 spin_lock(&si->lock); 788 return true; 789 } 790 791 if (vm_swap_full() && READ_ONCE(si->swap_map[offset]) == SWAP_HAS_CACHE) { 792 spin_lock(&si->lock); 793 return true; 794 } 795 796 return false; 797 } 798 799 static int scan_swap_map_slots(struct swap_info_struct *si, 800 unsigned char usage, int nr, 801 swp_entry_t slots[]) 802 { 803 struct swap_cluster_info *ci; 804 unsigned long offset; 805 unsigned long scan_base; 806 unsigned long last_in_cluster = 0; 807 int latency_ration = LATENCY_LIMIT; 808 int n_ret = 0; 809 bool scanned_many = false; 810 811 /* 812 * We try to cluster swap pages by allocating them sequentially 813 * in swap. Once we've allocated SWAPFILE_CLUSTER pages this 814 * way, however, we resort to first-free allocation, starting 815 * a new cluster. This prevents us from scattering swap pages 816 * all over the entire swap partition, so that we reduce 817 * overall disk seek times between swap pages. -- sct 818 * But we do now try to find an empty cluster. -Andrea 819 * And we let swap pages go all over an SSD partition. Hugh 820 */ 821 822 si->flags += SWP_SCANNING; 823 /* 824 * Use percpu scan base for SSD to reduce lock contention on 825 * cluster and swap cache. For HDD, sequential access is more 826 * important. 827 */ 828 if (si->flags & SWP_SOLIDSTATE) 829 scan_base = this_cpu_read(*si->cluster_next_cpu); 830 else 831 scan_base = si->cluster_next; 832 offset = scan_base; 833 834 /* SSD algorithm */ 835 if (si->cluster_info) { 836 if (!scan_swap_map_try_ssd_cluster(si, &offset, &scan_base)) 837 goto scan; 838 } else if (unlikely(!si->cluster_nr--)) { 839 if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) { 840 si->cluster_nr = SWAPFILE_CLUSTER - 1; 841 goto checks; 842 } 843 844 spin_unlock(&si->lock); 845 846 /* 847 * If seek is expensive, start searching for new cluster from 848 * start of partition, to minimize the span of allocated swap. 849 * If seek is cheap, that is the SWP_SOLIDSTATE si->cluster_info 850 * case, just handled by scan_swap_map_try_ssd_cluster() above. 851 */ 852 scan_base = offset = si->lowest_bit; 853 last_in_cluster = offset + SWAPFILE_CLUSTER - 1; 854 855 /* Locate the first empty (unaligned) cluster */ 856 for (; last_in_cluster <= si->highest_bit; offset++) { 857 if (si->swap_map[offset]) 858 last_in_cluster = offset + SWAPFILE_CLUSTER; 859 else if (offset == last_in_cluster) { 860 spin_lock(&si->lock); 861 offset -= SWAPFILE_CLUSTER - 1; 862 si->cluster_next = offset; 863 si->cluster_nr = SWAPFILE_CLUSTER - 1; 864 goto checks; 865 } 866 if (unlikely(--latency_ration < 0)) { 867 cond_resched(); 868 latency_ration = LATENCY_LIMIT; 869 } 870 } 871 872 offset = scan_base; 873 spin_lock(&si->lock); 874 si->cluster_nr = SWAPFILE_CLUSTER - 1; 875 } 876 877 checks: 878 if (si->cluster_info) { 879 while (scan_swap_map_ssd_cluster_conflict(si, offset)) { 880 /* take a break if we already got some slots */ 881 if (n_ret) 882 goto done; 883 if (!scan_swap_map_try_ssd_cluster(si, &offset, 884 &scan_base)) 885 goto scan; 886 } 887 } 888 if (!(si->flags & SWP_WRITEOK)) 889 goto no_page; 890 if (!si->highest_bit) 891 goto no_page; 892 if (offset > si->highest_bit) 893 scan_base = offset = si->lowest_bit; 894 895 ci = lock_cluster(si, offset); 896 /* reuse swap entry of cache-only swap if not busy. */ 897 if (vm_swap_full() && si->swap_map[offset] == SWAP_HAS_CACHE) { 898 int swap_was_freed; 899 unlock_cluster(ci); 900 spin_unlock(&si->lock); 901 swap_was_freed = __try_to_reclaim_swap(si, offset, TTRS_ANYWAY); 902 spin_lock(&si->lock); 903 /* entry was freed successfully, try to use this again */ 904 if (swap_was_freed) 905 goto checks; 906 goto scan; /* check next one */ 907 } 908 909 if (si->swap_map[offset]) { 910 unlock_cluster(ci); 911 if (!n_ret) 912 goto scan; 913 else 914 goto done; 915 } 916 WRITE_ONCE(si->swap_map[offset], usage); 917 inc_cluster_info_page(si, si->cluster_info, offset); 918 unlock_cluster(ci); 919 920 swap_range_alloc(si, offset, 1); 921 slots[n_ret++] = swp_entry(si->type, offset); 922 923 /* got enough slots or reach max slots? */ 924 if ((n_ret == nr) || (offset >= si->highest_bit)) 925 goto done; 926 927 /* search for next available slot */ 928 929 /* time to take a break? */ 930 if (unlikely(--latency_ration < 0)) { 931 if (n_ret) 932 goto done; 933 spin_unlock(&si->lock); 934 cond_resched(); 935 spin_lock(&si->lock); 936 latency_ration = LATENCY_LIMIT; 937 } 938 939 /* try to get more slots in cluster */ 940 if (si->cluster_info) { 941 if (scan_swap_map_try_ssd_cluster(si, &offset, &scan_base)) 942 goto checks; 943 } else if (si->cluster_nr && !si->swap_map[++offset]) { 944 /* non-ssd case, still more slots in cluster? */ 945 --si->cluster_nr; 946 goto checks; 947 } 948 949 /* 950 * Even if there's no free clusters available (fragmented), 951 * try to scan a little more quickly with lock held unless we 952 * have scanned too many slots already. 953 */ 954 if (!scanned_many) { 955 unsigned long scan_limit; 956 957 if (offset < scan_base) 958 scan_limit = scan_base; 959 else 960 scan_limit = si->highest_bit; 961 for (; offset <= scan_limit && --latency_ration > 0; 962 offset++) { 963 if (!si->swap_map[offset]) 964 goto checks; 965 } 966 } 967 968 done: 969 set_cluster_next(si, offset + 1); 970 si->flags -= SWP_SCANNING; 971 return n_ret; 972 973 scan: 974 spin_unlock(&si->lock); 975 while (++offset <= READ_ONCE(si->highest_bit)) { 976 if (unlikely(--latency_ration < 0)) { 977 cond_resched(); 978 latency_ration = LATENCY_LIMIT; 979 scanned_many = true; 980 } 981 if (swap_offset_available_and_locked(si, offset)) 982 goto checks; 983 } 984 offset = si->lowest_bit; 985 while (offset < scan_base) { 986 if (unlikely(--latency_ration < 0)) { 987 cond_resched(); 988 latency_ration = LATENCY_LIMIT; 989 scanned_many = true; 990 } 991 if (swap_offset_available_and_locked(si, offset)) 992 goto checks; 993 offset++; 994 } 995 spin_lock(&si->lock); 996 997 no_page: 998 si->flags -= SWP_SCANNING; 999 return n_ret; 1000 } 1001 1002 static int swap_alloc_cluster(struct swap_info_struct *si, swp_entry_t *slot) 1003 { 1004 unsigned long idx; 1005 struct swap_cluster_info *ci; 1006 unsigned long offset; 1007 1008 /* 1009 * Should not even be attempting cluster allocations when huge 1010 * page swap is disabled. Warn and fail the allocation. 1011 */ 1012 if (!IS_ENABLED(CONFIG_THP_SWAP)) { 1013 VM_WARN_ON_ONCE(1); 1014 return 0; 1015 } 1016 1017 if (cluster_list_empty(&si->free_clusters)) 1018 return 0; 1019 1020 idx = cluster_list_first(&si->free_clusters); 1021 offset = idx * SWAPFILE_CLUSTER; 1022 ci = lock_cluster(si, offset); 1023 alloc_cluster(si, idx); 1024 cluster_set_count_flag(ci, SWAPFILE_CLUSTER, CLUSTER_FLAG_HUGE); 1025 1026 memset(si->swap_map + offset, SWAP_HAS_CACHE, SWAPFILE_CLUSTER); 1027 unlock_cluster(ci); 1028 swap_range_alloc(si, offset, SWAPFILE_CLUSTER); 1029 *slot = swp_entry(si->type, offset); 1030 1031 return 1; 1032 } 1033 1034 static void swap_free_cluster(struct swap_info_struct *si, unsigned long idx) 1035 { 1036 unsigned long offset = idx * SWAPFILE_CLUSTER; 1037 struct swap_cluster_info *ci; 1038 1039 ci = lock_cluster(si, offset); 1040 memset(si->swap_map + offset, 0, SWAPFILE_CLUSTER); 1041 cluster_set_count_flag(ci, 0, 0); 1042 free_cluster(si, idx); 1043 unlock_cluster(ci); 1044 swap_range_free(si, offset, SWAPFILE_CLUSTER); 1045 } 1046 1047 int get_swap_pages(int n_goal, swp_entry_t swp_entries[], int entry_size) 1048 { 1049 unsigned long size = swap_entry_size(entry_size); 1050 struct swap_info_struct *si, *next; 1051 long avail_pgs; 1052 int n_ret = 0; 1053 int node; 1054 1055 /* Only single cluster request supported */ 1056 WARN_ON_ONCE(n_goal > 1 && size == SWAPFILE_CLUSTER); 1057 1058 spin_lock(&swap_avail_lock); 1059 1060 avail_pgs = atomic_long_read(&nr_swap_pages) / size; 1061 if (avail_pgs <= 0) { 1062 spin_unlock(&swap_avail_lock); 1063 goto noswap; 1064 } 1065 1066 n_goal = min3((long)n_goal, (long)SWAP_BATCH, avail_pgs); 1067 1068 atomic_long_sub(n_goal * size, &nr_swap_pages); 1069 1070 start_over: 1071 node = numa_node_id(); 1072 plist_for_each_entry_safe(si, next, &swap_avail_heads[node], avail_lists[node]) { 1073 /* requeue si to after same-priority siblings */ 1074 plist_requeue(&si->avail_lists[node], &swap_avail_heads[node]); 1075 spin_unlock(&swap_avail_lock); 1076 spin_lock(&si->lock); 1077 if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) { 1078 spin_lock(&swap_avail_lock); 1079 if (plist_node_empty(&si->avail_lists[node])) { 1080 spin_unlock(&si->lock); 1081 goto nextsi; 1082 } 1083 WARN(!si->highest_bit, 1084 "swap_info %d in list but !highest_bit\n", 1085 si->type); 1086 WARN(!(si->flags & SWP_WRITEOK), 1087 "swap_info %d in list but !SWP_WRITEOK\n", 1088 si->type); 1089 __del_from_avail_list(si); 1090 spin_unlock(&si->lock); 1091 goto nextsi; 1092 } 1093 if (size == SWAPFILE_CLUSTER) { 1094 if (si->flags & SWP_BLKDEV) 1095 n_ret = swap_alloc_cluster(si, swp_entries); 1096 } else 1097 n_ret = scan_swap_map_slots(si, SWAP_HAS_CACHE, 1098 n_goal, swp_entries); 1099 spin_unlock(&si->lock); 1100 if (n_ret || size == SWAPFILE_CLUSTER) 1101 goto check_out; 1102 pr_debug("scan_swap_map of si %d failed to find offset\n", 1103 si->type); 1104 1105 spin_lock(&swap_avail_lock); 1106 nextsi: 1107 /* 1108 * if we got here, it's likely that si was almost full before, 1109 * and since scan_swap_map_slots() can drop the si->lock, 1110 * multiple callers probably all tried to get a page from the 1111 * same si and it filled up before we could get one; or, the si 1112 * filled up between us dropping swap_avail_lock and taking 1113 * si->lock. Since we dropped the swap_avail_lock, the 1114 * swap_avail_head list may have been modified; so if next is 1115 * still in the swap_avail_head list then try it, otherwise 1116 * start over if we have not gotten any slots. 1117 */ 1118 if (plist_node_empty(&next->avail_lists[node])) 1119 goto start_over; 1120 } 1121 1122 spin_unlock(&swap_avail_lock); 1123 1124 check_out: 1125 if (n_ret < n_goal) 1126 atomic_long_add((long)(n_goal - n_ret) * size, 1127 &nr_swap_pages); 1128 noswap: 1129 return n_ret; 1130 } 1131 1132 static struct swap_info_struct *_swap_info_get(swp_entry_t entry) 1133 { 1134 struct swap_info_struct *p; 1135 unsigned long offset; 1136 1137 if (!entry.val) 1138 goto out; 1139 p = swp_swap_info(entry); 1140 if (!p) 1141 goto bad_nofile; 1142 if (data_race(!(p->flags & SWP_USED))) 1143 goto bad_device; 1144 offset = swp_offset(entry); 1145 if (offset >= p->max) 1146 goto bad_offset; 1147 if (data_race(!p->swap_map[swp_offset(entry)])) 1148 goto bad_free; 1149 return p; 1150 1151 bad_free: 1152 pr_err("%s: %s%08lx\n", __func__, Unused_offset, entry.val); 1153 goto out; 1154 bad_offset: 1155 pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val); 1156 goto out; 1157 bad_device: 1158 pr_err("%s: %s%08lx\n", __func__, Unused_file, entry.val); 1159 goto out; 1160 bad_nofile: 1161 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val); 1162 out: 1163 return NULL; 1164 } 1165 1166 static struct swap_info_struct *swap_info_get_cont(swp_entry_t entry, 1167 struct swap_info_struct *q) 1168 { 1169 struct swap_info_struct *p; 1170 1171 p = _swap_info_get(entry); 1172 1173 if (p != q) { 1174 if (q != NULL) 1175 spin_unlock(&q->lock); 1176 if (p != NULL) 1177 spin_lock(&p->lock); 1178 } 1179 return p; 1180 } 1181 1182 static unsigned char __swap_entry_free_locked(struct swap_info_struct *p, 1183 unsigned long offset, 1184 unsigned char usage) 1185 { 1186 unsigned char count; 1187 unsigned char has_cache; 1188 1189 count = p->swap_map[offset]; 1190 1191 has_cache = count & SWAP_HAS_CACHE; 1192 count &= ~SWAP_HAS_CACHE; 1193 1194 if (usage == SWAP_HAS_CACHE) { 1195 VM_BUG_ON(!has_cache); 1196 has_cache = 0; 1197 } else if (count == SWAP_MAP_SHMEM) { 1198 /* 1199 * Or we could insist on shmem.c using a special 1200 * swap_shmem_free() and free_shmem_swap_and_cache()... 1201 */ 1202 count = 0; 1203 } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { 1204 if (count == COUNT_CONTINUED) { 1205 if (swap_count_continued(p, offset, count)) 1206 count = SWAP_MAP_MAX | COUNT_CONTINUED; 1207 else 1208 count = SWAP_MAP_MAX; 1209 } else 1210 count--; 1211 } 1212 1213 usage = count | has_cache; 1214 if (usage) 1215 WRITE_ONCE(p->swap_map[offset], usage); 1216 else 1217 WRITE_ONCE(p->swap_map[offset], SWAP_HAS_CACHE); 1218 1219 return usage; 1220 } 1221 1222 /* 1223 * Check whether swap entry is valid in the swap device. If so, 1224 * return pointer to swap_info_struct, and keep the swap entry valid 1225 * via preventing the swap device from being swapoff, until 1226 * put_swap_device() is called. Otherwise return NULL. 1227 * 1228 * Notice that swapoff or swapoff+swapon can still happen before the 1229 * percpu_ref_tryget_live() in get_swap_device() or after the 1230 * percpu_ref_put() in put_swap_device() if there isn't any other way 1231 * to prevent swapoff, such as page lock, page table lock, etc. The 1232 * caller must be prepared for that. For example, the following 1233 * situation is possible. 1234 * 1235 * CPU1 CPU2 1236 * do_swap_page() 1237 * ... swapoff+swapon 1238 * __read_swap_cache_async() 1239 * swapcache_prepare() 1240 * __swap_duplicate() 1241 * // check swap_map 1242 * // verify PTE not changed 1243 * 1244 * In __swap_duplicate(), the swap_map need to be checked before 1245 * changing partly because the specified swap entry may be for another 1246 * swap device which has been swapoff. And in do_swap_page(), after 1247 * the page is read from the swap device, the PTE is verified not 1248 * changed with the page table locked to check whether the swap device 1249 * has been swapoff or swapoff+swapon. 1250 */ 1251 struct swap_info_struct *get_swap_device(swp_entry_t entry) 1252 { 1253 struct swap_info_struct *si; 1254 unsigned long offset; 1255 1256 if (!entry.val) 1257 goto out; 1258 si = swp_swap_info(entry); 1259 if (!si) 1260 goto bad_nofile; 1261 if (!percpu_ref_tryget_live(&si->users)) 1262 goto out; 1263 /* 1264 * Guarantee the si->users are checked before accessing other 1265 * fields of swap_info_struct. 1266 * 1267 * Paired with the spin_unlock() after setup_swap_info() in 1268 * enable_swap_info(). 1269 */ 1270 smp_rmb(); 1271 offset = swp_offset(entry); 1272 if (offset >= si->max) 1273 goto put_out; 1274 1275 return si; 1276 bad_nofile: 1277 pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val); 1278 out: 1279 return NULL; 1280 put_out: 1281 pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val); 1282 percpu_ref_put(&si->users); 1283 return NULL; 1284 } 1285 1286 static unsigned char __swap_entry_free(struct swap_info_struct *p, 1287 swp_entry_t entry) 1288 { 1289 struct swap_cluster_info *ci; 1290 unsigned long offset = swp_offset(entry); 1291 unsigned char usage; 1292 1293 ci = lock_cluster_or_swap_info(p, offset); 1294 usage = __swap_entry_free_locked(p, offset, 1); 1295 unlock_cluster_or_swap_info(p, ci); 1296 if (!usage) 1297 free_swap_slot(entry); 1298 1299 return usage; 1300 } 1301 1302 static void swap_entry_free(struct swap_info_struct *p, swp_entry_t entry) 1303 { 1304 struct swap_cluster_info *ci; 1305 unsigned long offset = swp_offset(entry); 1306 unsigned char count; 1307 1308 ci = lock_cluster(p, offset); 1309 count = p->swap_map[offset]; 1310 VM_BUG_ON(count != SWAP_HAS_CACHE); 1311 p->swap_map[offset] = 0; 1312 dec_cluster_info_page(p, p->cluster_info, offset); 1313 unlock_cluster(ci); 1314 1315 mem_cgroup_uncharge_swap(entry, 1); 1316 swap_range_free(p, offset, 1); 1317 } 1318 1319 /* 1320 * Caller has made sure that the swap device corresponding to entry 1321 * is still around or has not been recycled. 1322 */ 1323 void swap_free(swp_entry_t entry) 1324 { 1325 struct swap_info_struct *p; 1326 1327 p = _swap_info_get(entry); 1328 if (p) 1329 __swap_entry_free(p, entry); 1330 } 1331 1332 /* 1333 * Called after dropping swapcache to decrease refcnt to swap entries. 1334 */ 1335 void put_swap_folio(struct folio *folio, swp_entry_t entry) 1336 { 1337 unsigned long offset = swp_offset(entry); 1338 unsigned long idx = offset / SWAPFILE_CLUSTER; 1339 struct swap_cluster_info *ci; 1340 struct swap_info_struct *si; 1341 unsigned char *map; 1342 unsigned int i, free_entries = 0; 1343 unsigned char val; 1344 int size = swap_entry_size(folio_nr_pages(folio)); 1345 1346 si = _swap_info_get(entry); 1347 if (!si) 1348 return; 1349 1350 ci = lock_cluster_or_swap_info(si, offset); 1351 if (size == SWAPFILE_CLUSTER) { 1352 VM_BUG_ON(!cluster_is_huge(ci)); 1353 map = si->swap_map + offset; 1354 for (i = 0; i < SWAPFILE_CLUSTER; i++) { 1355 val = map[i]; 1356 VM_BUG_ON(!(val & SWAP_HAS_CACHE)); 1357 if (val == SWAP_HAS_CACHE) 1358 free_entries++; 1359 } 1360 cluster_clear_huge(ci); 1361 if (free_entries == SWAPFILE_CLUSTER) { 1362 unlock_cluster_or_swap_info(si, ci); 1363 spin_lock(&si->lock); 1364 mem_cgroup_uncharge_swap(entry, SWAPFILE_CLUSTER); 1365 swap_free_cluster(si, idx); 1366 spin_unlock(&si->lock); 1367 return; 1368 } 1369 } 1370 for (i = 0; i < size; i++, entry.val++) { 1371 if (!__swap_entry_free_locked(si, offset + i, SWAP_HAS_CACHE)) { 1372 unlock_cluster_or_swap_info(si, ci); 1373 free_swap_slot(entry); 1374 if (i == size - 1) 1375 return; 1376 lock_cluster_or_swap_info(si, offset); 1377 } 1378 } 1379 unlock_cluster_or_swap_info(si, ci); 1380 } 1381 1382 #ifdef CONFIG_THP_SWAP 1383 int split_swap_cluster(swp_entry_t entry) 1384 { 1385 struct swap_info_struct *si; 1386 struct swap_cluster_info *ci; 1387 unsigned long offset = swp_offset(entry); 1388 1389 si = _swap_info_get(entry); 1390 if (!si) 1391 return -EBUSY; 1392 ci = lock_cluster(si, offset); 1393 cluster_clear_huge(ci); 1394 unlock_cluster(ci); 1395 return 0; 1396 } 1397 #endif 1398 1399 static int swp_entry_cmp(const void *ent1, const void *ent2) 1400 { 1401 const swp_entry_t *e1 = ent1, *e2 = ent2; 1402 1403 return (int)swp_type(*e1) - (int)swp_type(*e2); 1404 } 1405 1406 void swapcache_free_entries(swp_entry_t *entries, int n) 1407 { 1408 struct swap_info_struct *p, *prev; 1409 int i; 1410 1411 if (n <= 0) 1412 return; 1413 1414 prev = NULL; 1415 p = NULL; 1416 1417 /* 1418 * Sort swap entries by swap device, so each lock is only taken once. 1419 * nr_swapfiles isn't absolutely correct, but the overhead of sort() is 1420 * so low that it isn't necessary to optimize further. 1421 */ 1422 if (nr_swapfiles > 1) 1423 sort(entries, n, sizeof(entries[0]), swp_entry_cmp, NULL); 1424 for (i = 0; i < n; ++i) { 1425 p = swap_info_get_cont(entries[i], prev); 1426 if (p) 1427 swap_entry_free(p, entries[i]); 1428 prev = p; 1429 } 1430 if (p) 1431 spin_unlock(&p->lock); 1432 } 1433 1434 int __swap_count(swp_entry_t entry) 1435 { 1436 struct swap_info_struct *si; 1437 pgoff_t offset = swp_offset(entry); 1438 int count = 0; 1439 1440 si = get_swap_device(entry); 1441 if (si) { 1442 count = swap_count(si->swap_map[offset]); 1443 put_swap_device(si); 1444 } 1445 return count; 1446 } 1447 1448 /* 1449 * How many references to @entry are currently swapped out? 1450 * This does not give an exact answer when swap count is continued, 1451 * but does include the high COUNT_CONTINUED flag to allow for that. 1452 */ 1453 static int swap_swapcount(struct swap_info_struct *si, swp_entry_t entry) 1454 { 1455 pgoff_t offset = swp_offset(entry); 1456 struct swap_cluster_info *ci; 1457 int count; 1458 1459 ci = lock_cluster_or_swap_info(si, offset); 1460 count = swap_count(si->swap_map[offset]); 1461 unlock_cluster_or_swap_info(si, ci); 1462 return count; 1463 } 1464 1465 /* 1466 * How many references to @entry are currently swapped out? 1467 * This does not give an exact answer when swap count is continued, 1468 * but does include the high COUNT_CONTINUED flag to allow for that. 1469 */ 1470 int __swp_swapcount(swp_entry_t entry) 1471 { 1472 int count = 0; 1473 struct swap_info_struct *si; 1474 1475 si = get_swap_device(entry); 1476 if (si) { 1477 count = swap_swapcount(si, entry); 1478 put_swap_device(si); 1479 } 1480 return count; 1481 } 1482 1483 /* 1484 * How many references to @entry are currently swapped out? 1485 * This considers COUNT_CONTINUED so it returns exact answer. 1486 */ 1487 int swp_swapcount(swp_entry_t entry) 1488 { 1489 int count, tmp_count, n; 1490 struct swap_info_struct *p; 1491 struct swap_cluster_info *ci; 1492 struct page *page; 1493 pgoff_t offset; 1494 unsigned char *map; 1495 1496 p = _swap_info_get(entry); 1497 if (!p) 1498 return 0; 1499 1500 offset = swp_offset(entry); 1501 1502 ci = lock_cluster_or_swap_info(p, offset); 1503 1504 count = swap_count(p->swap_map[offset]); 1505 if (!(count & COUNT_CONTINUED)) 1506 goto out; 1507 1508 count &= ~COUNT_CONTINUED; 1509 n = SWAP_MAP_MAX + 1; 1510 1511 page = vmalloc_to_page(p->swap_map + offset); 1512 offset &= ~PAGE_MASK; 1513 VM_BUG_ON(page_private(page) != SWP_CONTINUED); 1514 1515 do { 1516 page = list_next_entry(page, lru); 1517 map = kmap_atomic(page); 1518 tmp_count = map[offset]; 1519 kunmap_atomic(map); 1520 1521 count += (tmp_count & ~COUNT_CONTINUED) * n; 1522 n *= (SWAP_CONT_MAX + 1); 1523 } while (tmp_count & COUNT_CONTINUED); 1524 out: 1525 unlock_cluster_or_swap_info(p, ci); 1526 return count; 1527 } 1528 1529 static bool swap_page_trans_huge_swapped(struct swap_info_struct *si, 1530 swp_entry_t entry) 1531 { 1532 struct swap_cluster_info *ci; 1533 unsigned char *map = si->swap_map; 1534 unsigned long roffset = swp_offset(entry); 1535 unsigned long offset = round_down(roffset, SWAPFILE_CLUSTER); 1536 int i; 1537 bool ret = false; 1538 1539 ci = lock_cluster_or_swap_info(si, offset); 1540 if (!ci || !cluster_is_huge(ci)) { 1541 if (swap_count(map[roffset])) 1542 ret = true; 1543 goto unlock_out; 1544 } 1545 for (i = 0; i < SWAPFILE_CLUSTER; i++) { 1546 if (swap_count(map[offset + i])) { 1547 ret = true; 1548 break; 1549 } 1550 } 1551 unlock_out: 1552 unlock_cluster_or_swap_info(si, ci); 1553 return ret; 1554 } 1555 1556 static bool folio_swapped(struct folio *folio) 1557 { 1558 swp_entry_t entry = folio_swap_entry(folio); 1559 struct swap_info_struct *si = _swap_info_get(entry); 1560 1561 if (!si) 1562 return false; 1563 1564 if (!IS_ENABLED(CONFIG_THP_SWAP) || likely(!folio_test_large(folio))) 1565 return swap_swapcount(si, entry) != 0; 1566 1567 return swap_page_trans_huge_swapped(si, entry); 1568 } 1569 1570 /** 1571 * folio_free_swap() - Free the swap space used for this folio. 1572 * @folio: The folio to remove. 1573 * 1574 * If swap is getting full, or if there are no more mappings of this folio, 1575 * then call folio_free_swap to free its swap space. 1576 * 1577 * Return: true if we were able to release the swap space. 1578 */ 1579 bool folio_free_swap(struct folio *folio) 1580 { 1581 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); 1582 1583 if (!folio_test_swapcache(folio)) 1584 return false; 1585 if (folio_test_writeback(folio)) 1586 return false; 1587 if (folio_swapped(folio)) 1588 return false; 1589 1590 /* 1591 * Once hibernation has begun to create its image of memory, 1592 * there's a danger that one of the calls to folio_free_swap() 1593 * - most probably a call from __try_to_reclaim_swap() while 1594 * hibernation is allocating its own swap pages for the image, 1595 * but conceivably even a call from memory reclaim - will free 1596 * the swap from a folio which has already been recorded in the 1597 * image as a clean swapcache folio, and then reuse its swap for 1598 * another page of the image. On waking from hibernation, the 1599 * original folio might be freed under memory pressure, then 1600 * later read back in from swap, now with the wrong data. 1601 * 1602 * Hibernation suspends storage while it is writing the image 1603 * to disk so check that here. 1604 */ 1605 if (pm_suspended_storage()) 1606 return false; 1607 1608 delete_from_swap_cache(folio); 1609 folio_set_dirty(folio); 1610 return true; 1611 } 1612 1613 /* 1614 * Free the swap entry like above, but also try to 1615 * free the page cache entry if it is the last user. 1616 */ 1617 int free_swap_and_cache(swp_entry_t entry) 1618 { 1619 struct swap_info_struct *p; 1620 unsigned char count; 1621 1622 if (non_swap_entry(entry)) 1623 return 1; 1624 1625 p = _swap_info_get(entry); 1626 if (p) { 1627 count = __swap_entry_free(p, entry); 1628 if (count == SWAP_HAS_CACHE && 1629 !swap_page_trans_huge_swapped(p, entry)) 1630 __try_to_reclaim_swap(p, swp_offset(entry), 1631 TTRS_UNMAPPED | TTRS_FULL); 1632 } 1633 return p != NULL; 1634 } 1635 1636 #ifdef CONFIG_HIBERNATION 1637 1638 swp_entry_t get_swap_page_of_type(int type) 1639 { 1640 struct swap_info_struct *si = swap_type_to_swap_info(type); 1641 swp_entry_t entry = {0}; 1642 1643 if (!si) 1644 goto fail; 1645 1646 /* This is called for allocating swap entry, not cache */ 1647 spin_lock(&si->lock); 1648 if ((si->flags & SWP_WRITEOK) && scan_swap_map_slots(si, 1, 1, &entry)) 1649 atomic_long_dec(&nr_swap_pages); 1650 spin_unlock(&si->lock); 1651 fail: 1652 return entry; 1653 } 1654 1655 /* 1656 * Find the swap type that corresponds to given device (if any). 1657 * 1658 * @offset - number of the PAGE_SIZE-sized block of the device, starting 1659 * from 0, in which the swap header is expected to be located. 1660 * 1661 * This is needed for the suspend to disk (aka swsusp). 1662 */ 1663 int swap_type_of(dev_t device, sector_t offset) 1664 { 1665 int type; 1666 1667 if (!device) 1668 return -1; 1669 1670 spin_lock(&swap_lock); 1671 for (type = 0; type < nr_swapfiles; type++) { 1672 struct swap_info_struct *sis = swap_info[type]; 1673 1674 if (!(sis->flags & SWP_WRITEOK)) 1675 continue; 1676 1677 if (device == sis->bdev->bd_dev) { 1678 struct swap_extent *se = first_se(sis); 1679 1680 if (se->start_block == offset) { 1681 spin_unlock(&swap_lock); 1682 return type; 1683 } 1684 } 1685 } 1686 spin_unlock(&swap_lock); 1687 return -ENODEV; 1688 } 1689 1690 int find_first_swap(dev_t *device) 1691 { 1692 int type; 1693 1694 spin_lock(&swap_lock); 1695 for (type = 0; type < nr_swapfiles; type++) { 1696 struct swap_info_struct *sis = swap_info[type]; 1697 1698 if (!(sis->flags & SWP_WRITEOK)) 1699 continue; 1700 *device = sis->bdev->bd_dev; 1701 spin_unlock(&swap_lock); 1702 return type; 1703 } 1704 spin_unlock(&swap_lock); 1705 return -ENODEV; 1706 } 1707 1708 /* 1709 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev 1710 * corresponding to given index in swap_info (swap type). 1711 */ 1712 sector_t swapdev_block(int type, pgoff_t offset) 1713 { 1714 struct swap_info_struct *si = swap_type_to_swap_info(type); 1715 struct swap_extent *se; 1716 1717 if (!si || !(si->flags & SWP_WRITEOK)) 1718 return 0; 1719 se = offset_to_swap_extent(si, offset); 1720 return se->start_block + (offset - se->start_page); 1721 } 1722 1723 /* 1724 * Return either the total number of swap pages of given type, or the number 1725 * of free pages of that type (depending on @free) 1726 * 1727 * This is needed for software suspend 1728 */ 1729 unsigned int count_swap_pages(int type, int free) 1730 { 1731 unsigned int n = 0; 1732 1733 spin_lock(&swap_lock); 1734 if ((unsigned int)type < nr_swapfiles) { 1735 struct swap_info_struct *sis = swap_info[type]; 1736 1737 spin_lock(&sis->lock); 1738 if (sis->flags & SWP_WRITEOK) { 1739 n = sis->pages; 1740 if (free) 1741 n -= sis->inuse_pages; 1742 } 1743 spin_unlock(&sis->lock); 1744 } 1745 spin_unlock(&swap_lock); 1746 return n; 1747 } 1748 #endif /* CONFIG_HIBERNATION */ 1749 1750 static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte) 1751 { 1752 return pte_same(pte_swp_clear_flags(pte), swp_pte); 1753 } 1754 1755 /* 1756 * No need to decide whether this PTE shares the swap entry with others, 1757 * just let do_wp_page work it out if a write is requested later - to 1758 * force COW, vm_page_prot omits write permission from any private vma. 1759 */ 1760 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, 1761 unsigned long addr, swp_entry_t entry, struct folio *folio) 1762 { 1763 struct page *page = folio_file_page(folio, swp_offset(entry)); 1764 struct page *swapcache; 1765 spinlock_t *ptl; 1766 pte_t *pte, new_pte; 1767 int ret = 1; 1768 1769 swapcache = page; 1770 page = ksm_might_need_to_copy(page, vma, addr); 1771 if (unlikely(!page)) 1772 return -ENOMEM; 1773 1774 pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 1775 if (unlikely(!pte_same_as_swp(*pte, swp_entry_to_pte(entry)))) { 1776 ret = 0; 1777 goto out; 1778 } 1779 1780 if (unlikely(!PageUptodate(page))) { 1781 pte_t pteval; 1782 1783 dec_mm_counter(vma->vm_mm, MM_SWAPENTS); 1784 pteval = swp_entry_to_pte(make_swapin_error_entry()); 1785 set_pte_at(vma->vm_mm, addr, pte, pteval); 1786 swap_free(entry); 1787 ret = 0; 1788 goto out; 1789 } 1790 1791 /* See do_swap_page() */ 1792 BUG_ON(!PageAnon(page) && PageMappedToDisk(page)); 1793 BUG_ON(PageAnon(page) && PageAnonExclusive(page)); 1794 1795 dec_mm_counter(vma->vm_mm, MM_SWAPENTS); 1796 inc_mm_counter(vma->vm_mm, MM_ANONPAGES); 1797 get_page(page); 1798 if (page == swapcache) { 1799 rmap_t rmap_flags = RMAP_NONE; 1800 1801 /* 1802 * See do_swap_page(): PageWriteback() would be problematic. 1803 * However, we do a wait_on_page_writeback() just before this 1804 * call and have the page locked. 1805 */ 1806 VM_BUG_ON_PAGE(PageWriteback(page), page); 1807 if (pte_swp_exclusive(*pte)) 1808 rmap_flags |= RMAP_EXCLUSIVE; 1809 1810 page_add_anon_rmap(page, vma, addr, rmap_flags); 1811 } else { /* ksm created a completely new copy */ 1812 page_add_new_anon_rmap(page, vma, addr); 1813 lru_cache_add_inactive_or_unevictable(page, vma); 1814 } 1815 new_pte = pte_mkold(mk_pte(page, vma->vm_page_prot)); 1816 if (pte_swp_soft_dirty(*pte)) 1817 new_pte = pte_mksoft_dirty(new_pte); 1818 if (pte_swp_uffd_wp(*pte)) 1819 new_pte = pte_mkuffd_wp(new_pte); 1820 set_pte_at(vma->vm_mm, addr, pte, new_pte); 1821 swap_free(entry); 1822 out: 1823 pte_unmap_unlock(pte, ptl); 1824 if (page != swapcache) { 1825 unlock_page(page); 1826 put_page(page); 1827 } 1828 return ret; 1829 } 1830 1831 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd, 1832 unsigned long addr, unsigned long end, 1833 unsigned int type) 1834 { 1835 swp_entry_t entry; 1836 pte_t *pte; 1837 struct swap_info_struct *si; 1838 int ret = 0; 1839 volatile unsigned char *swap_map; 1840 1841 si = swap_info[type]; 1842 pte = pte_offset_map(pmd, addr); 1843 do { 1844 struct folio *folio; 1845 unsigned long offset; 1846 1847 if (!is_swap_pte(*pte)) 1848 continue; 1849 1850 entry = pte_to_swp_entry(*pte); 1851 if (swp_type(entry) != type) 1852 continue; 1853 1854 offset = swp_offset(entry); 1855 pte_unmap(pte); 1856 swap_map = &si->swap_map[offset]; 1857 folio = swap_cache_get_folio(entry, vma, addr); 1858 if (!folio) { 1859 struct page *page; 1860 struct vm_fault vmf = { 1861 .vma = vma, 1862 .address = addr, 1863 .real_address = addr, 1864 .pmd = pmd, 1865 }; 1866 1867 page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE, 1868 &vmf); 1869 if (page) 1870 folio = page_folio(page); 1871 } 1872 if (!folio) { 1873 if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD) 1874 goto try_next; 1875 return -ENOMEM; 1876 } 1877 1878 folio_lock(folio); 1879 folio_wait_writeback(folio); 1880 ret = unuse_pte(vma, pmd, addr, entry, folio); 1881 if (ret < 0) { 1882 folio_unlock(folio); 1883 folio_put(folio); 1884 goto out; 1885 } 1886 1887 folio_free_swap(folio); 1888 folio_unlock(folio); 1889 folio_put(folio); 1890 try_next: 1891 pte = pte_offset_map(pmd, addr); 1892 } while (pte++, addr += PAGE_SIZE, addr != end); 1893 pte_unmap(pte - 1); 1894 1895 ret = 0; 1896 out: 1897 return ret; 1898 } 1899 1900 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud, 1901 unsigned long addr, unsigned long end, 1902 unsigned int type) 1903 { 1904 pmd_t *pmd; 1905 unsigned long next; 1906 int ret; 1907 1908 pmd = pmd_offset(pud, addr); 1909 do { 1910 cond_resched(); 1911 next = pmd_addr_end(addr, end); 1912 if (pmd_none_or_trans_huge_or_clear_bad(pmd)) 1913 continue; 1914 ret = unuse_pte_range(vma, pmd, addr, next, type); 1915 if (ret) 1916 return ret; 1917 } while (pmd++, addr = next, addr != end); 1918 return 0; 1919 } 1920 1921 static inline int unuse_pud_range(struct vm_area_struct *vma, p4d_t *p4d, 1922 unsigned long addr, unsigned long end, 1923 unsigned int type) 1924 { 1925 pud_t *pud; 1926 unsigned long next; 1927 int ret; 1928 1929 pud = pud_offset(p4d, addr); 1930 do { 1931 next = pud_addr_end(addr, end); 1932 if (pud_none_or_clear_bad(pud)) 1933 continue; 1934 ret = unuse_pmd_range(vma, pud, addr, next, type); 1935 if (ret) 1936 return ret; 1937 } while (pud++, addr = next, addr != end); 1938 return 0; 1939 } 1940 1941 static inline int unuse_p4d_range(struct vm_area_struct *vma, pgd_t *pgd, 1942 unsigned long addr, unsigned long end, 1943 unsigned int type) 1944 { 1945 p4d_t *p4d; 1946 unsigned long next; 1947 int ret; 1948 1949 p4d = p4d_offset(pgd, addr); 1950 do { 1951 next = p4d_addr_end(addr, end); 1952 if (p4d_none_or_clear_bad(p4d)) 1953 continue; 1954 ret = unuse_pud_range(vma, p4d, addr, next, type); 1955 if (ret) 1956 return ret; 1957 } while (p4d++, addr = next, addr != end); 1958 return 0; 1959 } 1960 1961 static int unuse_vma(struct vm_area_struct *vma, unsigned int type) 1962 { 1963 pgd_t *pgd; 1964 unsigned long addr, end, next; 1965 int ret; 1966 1967 addr = vma->vm_start; 1968 end = vma->vm_end; 1969 1970 pgd = pgd_offset(vma->vm_mm, addr); 1971 do { 1972 next = pgd_addr_end(addr, end); 1973 if (pgd_none_or_clear_bad(pgd)) 1974 continue; 1975 ret = unuse_p4d_range(vma, pgd, addr, next, type); 1976 if (ret) 1977 return ret; 1978 } while (pgd++, addr = next, addr != end); 1979 return 0; 1980 } 1981 1982 static int unuse_mm(struct mm_struct *mm, unsigned int type) 1983 { 1984 struct vm_area_struct *vma; 1985 int ret = 0; 1986 VMA_ITERATOR(vmi, mm, 0); 1987 1988 mmap_read_lock(mm); 1989 for_each_vma(vmi, vma) { 1990 if (vma->anon_vma) { 1991 ret = unuse_vma(vma, type); 1992 if (ret) 1993 break; 1994 } 1995 1996 cond_resched(); 1997 } 1998 mmap_read_unlock(mm); 1999 return ret; 2000 } 2001 2002 /* 2003 * Scan swap_map from current position to next entry still in use. 2004 * Return 0 if there are no inuse entries after prev till end of 2005 * the map. 2006 */ 2007 static unsigned int find_next_to_unuse(struct swap_info_struct *si, 2008 unsigned int prev) 2009 { 2010 unsigned int i; 2011 unsigned char count; 2012 2013 /* 2014 * No need for swap_lock here: we're just looking 2015 * for whether an entry is in use, not modifying it; false 2016 * hits are okay, and sys_swapoff() has already prevented new 2017 * allocations from this area (while holding swap_lock). 2018 */ 2019 for (i = prev + 1; i < si->max; i++) { 2020 count = READ_ONCE(si->swap_map[i]); 2021 if (count && swap_count(count) != SWAP_MAP_BAD) 2022 break; 2023 if ((i % LATENCY_LIMIT) == 0) 2024 cond_resched(); 2025 } 2026 2027 if (i == si->max) 2028 i = 0; 2029 2030 return i; 2031 } 2032 2033 static int try_to_unuse(unsigned int type) 2034 { 2035 struct mm_struct *prev_mm; 2036 struct mm_struct *mm; 2037 struct list_head *p; 2038 int retval = 0; 2039 struct swap_info_struct *si = swap_info[type]; 2040 struct folio *folio; 2041 swp_entry_t entry; 2042 unsigned int i; 2043 2044 if (!READ_ONCE(si->inuse_pages)) 2045 return 0; 2046 2047 retry: 2048 retval = shmem_unuse(type); 2049 if (retval) 2050 return retval; 2051 2052 prev_mm = &init_mm; 2053 mmget(prev_mm); 2054 2055 spin_lock(&mmlist_lock); 2056 p = &init_mm.mmlist; 2057 while (READ_ONCE(si->inuse_pages) && 2058 !signal_pending(current) && 2059 (p = p->next) != &init_mm.mmlist) { 2060 2061 mm = list_entry(p, struct mm_struct, mmlist); 2062 if (!mmget_not_zero(mm)) 2063 continue; 2064 spin_unlock(&mmlist_lock); 2065 mmput(prev_mm); 2066 prev_mm = mm; 2067 retval = unuse_mm(mm, type); 2068 if (retval) { 2069 mmput(prev_mm); 2070 return retval; 2071 } 2072 2073 /* 2074 * Make sure that we aren't completely killing 2075 * interactive performance. 2076 */ 2077 cond_resched(); 2078 spin_lock(&mmlist_lock); 2079 } 2080 spin_unlock(&mmlist_lock); 2081 2082 mmput(prev_mm); 2083 2084 i = 0; 2085 while (READ_ONCE(si->inuse_pages) && 2086 !signal_pending(current) && 2087 (i = find_next_to_unuse(si, i)) != 0) { 2088 2089 entry = swp_entry(type, i); 2090 folio = filemap_get_folio(swap_address_space(entry), i); 2091 if (!folio) 2092 continue; 2093 2094 /* 2095 * It is conceivable that a racing task removed this folio from 2096 * swap cache just before we acquired the page lock. The folio 2097 * might even be back in swap cache on another swap area. But 2098 * that is okay, folio_free_swap() only removes stale folios. 2099 */ 2100 folio_lock(folio); 2101 folio_wait_writeback(folio); 2102 folio_free_swap(folio); 2103 folio_unlock(folio); 2104 folio_put(folio); 2105 } 2106 2107 /* 2108 * Lets check again to see if there are still swap entries in the map. 2109 * If yes, we would need to do retry the unuse logic again. 2110 * Under global memory pressure, swap entries can be reinserted back 2111 * into process space after the mmlist loop above passes over them. 2112 * 2113 * Limit the number of retries? No: when mmget_not_zero() 2114 * above fails, that mm is likely to be freeing swap from 2115 * exit_mmap(), which proceeds at its own independent pace; 2116 * and even shmem_writepage() could have been preempted after 2117 * folio_alloc_swap(), temporarily hiding that swap. It's easy 2118 * and robust (though cpu-intensive) just to keep retrying. 2119 */ 2120 if (READ_ONCE(si->inuse_pages)) { 2121 if (!signal_pending(current)) 2122 goto retry; 2123 return -EINTR; 2124 } 2125 2126 return 0; 2127 } 2128 2129 /* 2130 * After a successful try_to_unuse, if no swap is now in use, we know 2131 * we can empty the mmlist. swap_lock must be held on entry and exit. 2132 * Note that mmlist_lock nests inside swap_lock, and an mm must be 2133 * added to the mmlist just after page_duplicate - before would be racy. 2134 */ 2135 static void drain_mmlist(void) 2136 { 2137 struct list_head *p, *next; 2138 unsigned int type; 2139 2140 for (type = 0; type < nr_swapfiles; type++) 2141 if (swap_info[type]->inuse_pages) 2142 return; 2143 spin_lock(&mmlist_lock); 2144 list_for_each_safe(p, next, &init_mm.mmlist) 2145 list_del_init(p); 2146 spin_unlock(&mmlist_lock); 2147 } 2148 2149 /* 2150 * Free all of a swapdev's extent information 2151 */ 2152 static void destroy_swap_extents(struct swap_info_struct *sis) 2153 { 2154 while (!RB_EMPTY_ROOT(&sis->swap_extent_root)) { 2155 struct rb_node *rb = sis->swap_extent_root.rb_node; 2156 struct swap_extent *se = rb_entry(rb, struct swap_extent, rb_node); 2157 2158 rb_erase(rb, &sis->swap_extent_root); 2159 kfree(se); 2160 } 2161 2162 if (sis->flags & SWP_ACTIVATED) { 2163 struct file *swap_file = sis->swap_file; 2164 struct address_space *mapping = swap_file->f_mapping; 2165 2166 sis->flags &= ~SWP_ACTIVATED; 2167 if (mapping->a_ops->swap_deactivate) 2168 mapping->a_ops->swap_deactivate(swap_file); 2169 } 2170 } 2171 2172 /* 2173 * Add a block range (and the corresponding page range) into this swapdev's 2174 * extent tree. 2175 * 2176 * This function rather assumes that it is called in ascending page order. 2177 */ 2178 int 2179 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page, 2180 unsigned long nr_pages, sector_t start_block) 2181 { 2182 struct rb_node **link = &sis->swap_extent_root.rb_node, *parent = NULL; 2183 struct swap_extent *se; 2184 struct swap_extent *new_se; 2185 2186 /* 2187 * place the new node at the right most since the 2188 * function is called in ascending page order. 2189 */ 2190 while (*link) { 2191 parent = *link; 2192 link = &parent->rb_right; 2193 } 2194 2195 if (parent) { 2196 se = rb_entry(parent, struct swap_extent, rb_node); 2197 BUG_ON(se->start_page + se->nr_pages != start_page); 2198 if (se->start_block + se->nr_pages == start_block) { 2199 /* Merge it */ 2200 se->nr_pages += nr_pages; 2201 return 0; 2202 } 2203 } 2204 2205 /* No merge, insert a new extent. */ 2206 new_se = kmalloc(sizeof(*se), GFP_KERNEL); 2207 if (new_se == NULL) 2208 return -ENOMEM; 2209 new_se->start_page = start_page; 2210 new_se->nr_pages = nr_pages; 2211 new_se->start_block = start_block; 2212 2213 rb_link_node(&new_se->rb_node, parent, link); 2214 rb_insert_color(&new_se->rb_node, &sis->swap_extent_root); 2215 return 1; 2216 } 2217 EXPORT_SYMBOL_GPL(add_swap_extent); 2218 2219 /* 2220 * A `swap extent' is a simple thing which maps a contiguous range of pages 2221 * onto a contiguous range of disk blocks. A rbtree of swap extents is 2222 * built at swapon time and is then used at swap_writepage/swap_readpage 2223 * time for locating where on disk a page belongs. 2224 * 2225 * If the swapfile is an S_ISBLK block device, a single extent is installed. 2226 * This is done so that the main operating code can treat S_ISBLK and S_ISREG 2227 * swap files identically. 2228 * 2229 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap 2230 * extent rbtree operates in PAGE_SIZE disk blocks. Both S_ISREG and S_ISBLK 2231 * swapfiles are handled *identically* after swapon time. 2232 * 2233 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks 2234 * and will parse them into a rbtree, in PAGE_SIZE chunks. If some stray 2235 * blocks are found which do not fall within the PAGE_SIZE alignment 2236 * requirements, they are simply tossed out - we will never use those blocks 2237 * for swapping. 2238 * 2239 * For all swap devices we set S_SWAPFILE across the life of the swapon. This 2240 * prevents users from writing to the swap device, which will corrupt memory. 2241 * 2242 * The amount of disk space which a single swap extent represents varies. 2243 * Typically it is in the 1-4 megabyte range. So we can have hundreds of 2244 * extents in the rbtree. - akpm. 2245 */ 2246 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span) 2247 { 2248 struct file *swap_file = sis->swap_file; 2249 struct address_space *mapping = swap_file->f_mapping; 2250 struct inode *inode = mapping->host; 2251 int ret; 2252 2253 if (S_ISBLK(inode->i_mode)) { 2254 ret = add_swap_extent(sis, 0, sis->max, 0); 2255 *span = sis->pages; 2256 return ret; 2257 } 2258 2259 if (mapping->a_ops->swap_activate) { 2260 ret = mapping->a_ops->swap_activate(sis, swap_file, span); 2261 if (ret < 0) 2262 return ret; 2263 sis->flags |= SWP_ACTIVATED; 2264 if ((sis->flags & SWP_FS_OPS) && 2265 sio_pool_init() != 0) { 2266 destroy_swap_extents(sis); 2267 return -ENOMEM; 2268 } 2269 return ret; 2270 } 2271 2272 return generic_swapfile_activate(sis, swap_file, span); 2273 } 2274 2275 static int swap_node(struct swap_info_struct *p) 2276 { 2277 struct block_device *bdev; 2278 2279 if (p->bdev) 2280 bdev = p->bdev; 2281 else 2282 bdev = p->swap_file->f_inode->i_sb->s_bdev; 2283 2284 return bdev ? bdev->bd_disk->node_id : NUMA_NO_NODE; 2285 } 2286 2287 static void setup_swap_info(struct swap_info_struct *p, int prio, 2288 unsigned char *swap_map, 2289 struct swap_cluster_info *cluster_info) 2290 { 2291 int i; 2292 2293 if (prio >= 0) 2294 p->prio = prio; 2295 else 2296 p->prio = --least_priority; 2297 /* 2298 * the plist prio is negated because plist ordering is 2299 * low-to-high, while swap ordering is high-to-low 2300 */ 2301 p->list.prio = -p->prio; 2302 for_each_node(i) { 2303 if (p->prio >= 0) 2304 p->avail_lists[i].prio = -p->prio; 2305 else { 2306 if (swap_node(p) == i) 2307 p->avail_lists[i].prio = 1; 2308 else 2309 p->avail_lists[i].prio = -p->prio; 2310 } 2311 } 2312 p->swap_map = swap_map; 2313 p->cluster_info = cluster_info; 2314 } 2315 2316 static void _enable_swap_info(struct swap_info_struct *p) 2317 { 2318 p->flags |= SWP_WRITEOK; 2319 atomic_long_add(p->pages, &nr_swap_pages); 2320 total_swap_pages += p->pages; 2321 2322 assert_spin_locked(&swap_lock); 2323 /* 2324 * both lists are plists, and thus priority ordered. 2325 * swap_active_head needs to be priority ordered for swapoff(), 2326 * which on removal of any swap_info_struct with an auto-assigned 2327 * (i.e. negative) priority increments the auto-assigned priority 2328 * of any lower-priority swap_info_structs. 2329 * swap_avail_head needs to be priority ordered for folio_alloc_swap(), 2330 * which allocates swap pages from the highest available priority 2331 * swap_info_struct. 2332 */ 2333 plist_add(&p->list, &swap_active_head); 2334 add_to_avail_list(p); 2335 } 2336 2337 static void enable_swap_info(struct swap_info_struct *p, int prio, 2338 unsigned char *swap_map, 2339 struct swap_cluster_info *cluster_info, 2340 unsigned long *frontswap_map) 2341 { 2342 if (IS_ENABLED(CONFIG_FRONTSWAP)) 2343 frontswap_init(p->type, frontswap_map); 2344 spin_lock(&swap_lock); 2345 spin_lock(&p->lock); 2346 setup_swap_info(p, prio, swap_map, cluster_info); 2347 spin_unlock(&p->lock); 2348 spin_unlock(&swap_lock); 2349 /* 2350 * Finished initializing swap device, now it's safe to reference it. 2351 */ 2352 percpu_ref_resurrect(&p->users); 2353 spin_lock(&swap_lock); 2354 spin_lock(&p->lock); 2355 _enable_swap_info(p); 2356 spin_unlock(&p->lock); 2357 spin_unlock(&swap_lock); 2358 } 2359 2360 static void reinsert_swap_info(struct swap_info_struct *p) 2361 { 2362 spin_lock(&swap_lock); 2363 spin_lock(&p->lock); 2364 setup_swap_info(p, p->prio, p->swap_map, p->cluster_info); 2365 _enable_swap_info(p); 2366 spin_unlock(&p->lock); 2367 spin_unlock(&swap_lock); 2368 } 2369 2370 bool has_usable_swap(void) 2371 { 2372 bool ret = true; 2373 2374 spin_lock(&swap_lock); 2375 if (plist_head_empty(&swap_active_head)) 2376 ret = false; 2377 spin_unlock(&swap_lock); 2378 return ret; 2379 } 2380 2381 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) 2382 { 2383 struct swap_info_struct *p = NULL; 2384 unsigned char *swap_map; 2385 struct swap_cluster_info *cluster_info; 2386 unsigned long *frontswap_map; 2387 struct file *swap_file, *victim; 2388 struct address_space *mapping; 2389 struct inode *inode; 2390 struct filename *pathname; 2391 int err, found = 0; 2392 unsigned int old_block_size; 2393 2394 if (!capable(CAP_SYS_ADMIN)) 2395 return -EPERM; 2396 2397 BUG_ON(!current->mm); 2398 2399 pathname = getname(specialfile); 2400 if (IS_ERR(pathname)) 2401 return PTR_ERR(pathname); 2402 2403 victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0); 2404 err = PTR_ERR(victim); 2405 if (IS_ERR(victim)) 2406 goto out; 2407 2408 mapping = victim->f_mapping; 2409 spin_lock(&swap_lock); 2410 plist_for_each_entry(p, &swap_active_head, list) { 2411 if (p->flags & SWP_WRITEOK) { 2412 if (p->swap_file->f_mapping == mapping) { 2413 found = 1; 2414 break; 2415 } 2416 } 2417 } 2418 if (!found) { 2419 err = -EINVAL; 2420 spin_unlock(&swap_lock); 2421 goto out_dput; 2422 } 2423 if (!security_vm_enough_memory_mm(current->mm, p->pages)) 2424 vm_unacct_memory(p->pages); 2425 else { 2426 err = -ENOMEM; 2427 spin_unlock(&swap_lock); 2428 goto out_dput; 2429 } 2430 del_from_avail_list(p); 2431 spin_lock(&p->lock); 2432 if (p->prio < 0) { 2433 struct swap_info_struct *si = p; 2434 int nid; 2435 2436 plist_for_each_entry_continue(si, &swap_active_head, list) { 2437 si->prio++; 2438 si->list.prio--; 2439 for_each_node(nid) { 2440 if (si->avail_lists[nid].prio != 1) 2441 si->avail_lists[nid].prio--; 2442 } 2443 } 2444 least_priority++; 2445 } 2446 plist_del(&p->list, &swap_active_head); 2447 atomic_long_sub(p->pages, &nr_swap_pages); 2448 total_swap_pages -= p->pages; 2449 p->flags &= ~SWP_WRITEOK; 2450 spin_unlock(&p->lock); 2451 spin_unlock(&swap_lock); 2452 2453 disable_swap_slots_cache_lock(); 2454 2455 set_current_oom_origin(); 2456 err = try_to_unuse(p->type); 2457 clear_current_oom_origin(); 2458 2459 if (err) { 2460 /* re-insert swap space back into swap_list */ 2461 reinsert_swap_info(p); 2462 reenable_swap_slots_cache_unlock(); 2463 goto out_dput; 2464 } 2465 2466 reenable_swap_slots_cache_unlock(); 2467 2468 /* 2469 * Wait for swap operations protected by get/put_swap_device() 2470 * to complete. 2471 * 2472 * We need synchronize_rcu() here to protect the accessing to 2473 * the swap cache data structure. 2474 */ 2475 percpu_ref_kill(&p->users); 2476 synchronize_rcu(); 2477 wait_for_completion(&p->comp); 2478 2479 flush_work(&p->discard_work); 2480 2481 destroy_swap_extents(p); 2482 if (p->flags & SWP_CONTINUED) 2483 free_swap_count_continuations(p); 2484 2485 if (!p->bdev || !bdev_nonrot(p->bdev)) 2486 atomic_dec(&nr_rotate_swap); 2487 2488 mutex_lock(&swapon_mutex); 2489 spin_lock(&swap_lock); 2490 spin_lock(&p->lock); 2491 drain_mmlist(); 2492 2493 /* wait for anyone still in scan_swap_map_slots */ 2494 p->highest_bit = 0; /* cuts scans short */ 2495 while (p->flags >= SWP_SCANNING) { 2496 spin_unlock(&p->lock); 2497 spin_unlock(&swap_lock); 2498 schedule_timeout_uninterruptible(1); 2499 spin_lock(&swap_lock); 2500 spin_lock(&p->lock); 2501 } 2502 2503 swap_file = p->swap_file; 2504 old_block_size = p->old_block_size; 2505 p->swap_file = NULL; 2506 p->max = 0; 2507 swap_map = p->swap_map; 2508 p->swap_map = NULL; 2509 cluster_info = p->cluster_info; 2510 p->cluster_info = NULL; 2511 frontswap_map = frontswap_map_get(p); 2512 spin_unlock(&p->lock); 2513 spin_unlock(&swap_lock); 2514 arch_swap_invalidate_area(p->type); 2515 frontswap_invalidate_area(p->type); 2516 frontswap_map_set(p, NULL); 2517 mutex_unlock(&swapon_mutex); 2518 free_percpu(p->percpu_cluster); 2519 p->percpu_cluster = NULL; 2520 free_percpu(p->cluster_next_cpu); 2521 p->cluster_next_cpu = NULL; 2522 vfree(swap_map); 2523 kvfree(cluster_info); 2524 kvfree(frontswap_map); 2525 /* Destroy swap account information */ 2526 swap_cgroup_swapoff(p->type); 2527 exit_swap_address_space(p->type); 2528 2529 inode = mapping->host; 2530 if (S_ISBLK(inode->i_mode)) { 2531 struct block_device *bdev = I_BDEV(inode); 2532 2533 set_blocksize(bdev, old_block_size); 2534 blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); 2535 } 2536 2537 inode_lock(inode); 2538 inode->i_flags &= ~S_SWAPFILE; 2539 inode_unlock(inode); 2540 filp_close(swap_file, NULL); 2541 2542 /* 2543 * Clear the SWP_USED flag after all resources are freed so that swapon 2544 * can reuse this swap_info in alloc_swap_info() safely. It is ok to 2545 * not hold p->lock after we cleared its SWP_WRITEOK. 2546 */ 2547 spin_lock(&swap_lock); 2548 p->flags = 0; 2549 spin_unlock(&swap_lock); 2550 2551 err = 0; 2552 atomic_inc(&proc_poll_event); 2553 wake_up_interruptible(&proc_poll_wait); 2554 2555 out_dput: 2556 filp_close(victim, NULL); 2557 out: 2558 putname(pathname); 2559 return err; 2560 } 2561 2562 #ifdef CONFIG_PROC_FS 2563 static __poll_t swaps_poll(struct file *file, poll_table *wait) 2564 { 2565 struct seq_file *seq = file->private_data; 2566 2567 poll_wait(file, &proc_poll_wait, wait); 2568 2569 if (seq->poll_event != atomic_read(&proc_poll_event)) { 2570 seq->poll_event = atomic_read(&proc_poll_event); 2571 return EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI; 2572 } 2573 2574 return EPOLLIN | EPOLLRDNORM; 2575 } 2576 2577 /* iterator */ 2578 static void *swap_start(struct seq_file *swap, loff_t *pos) 2579 { 2580 struct swap_info_struct *si; 2581 int type; 2582 loff_t l = *pos; 2583 2584 mutex_lock(&swapon_mutex); 2585 2586 if (!l) 2587 return SEQ_START_TOKEN; 2588 2589 for (type = 0; (si = swap_type_to_swap_info(type)); type++) { 2590 if (!(si->flags & SWP_USED) || !si->swap_map) 2591 continue; 2592 if (!--l) 2593 return si; 2594 } 2595 2596 return NULL; 2597 } 2598 2599 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos) 2600 { 2601 struct swap_info_struct *si = v; 2602 int type; 2603 2604 if (v == SEQ_START_TOKEN) 2605 type = 0; 2606 else 2607 type = si->type + 1; 2608 2609 ++(*pos); 2610 for (; (si = swap_type_to_swap_info(type)); type++) { 2611 if (!(si->flags & SWP_USED) || !si->swap_map) 2612 continue; 2613 return si; 2614 } 2615 2616 return NULL; 2617 } 2618 2619 static void swap_stop(struct seq_file *swap, void *v) 2620 { 2621 mutex_unlock(&swapon_mutex); 2622 } 2623 2624 static int swap_show(struct seq_file *swap, void *v) 2625 { 2626 struct swap_info_struct *si = v; 2627 struct file *file; 2628 int len; 2629 unsigned long bytes, inuse; 2630 2631 if (si == SEQ_START_TOKEN) { 2632 seq_puts(swap, "Filename\t\t\t\tType\t\tSize\t\tUsed\t\tPriority\n"); 2633 return 0; 2634 } 2635 2636 bytes = si->pages << (PAGE_SHIFT - 10); 2637 inuse = READ_ONCE(si->inuse_pages) << (PAGE_SHIFT - 10); 2638 2639 file = si->swap_file; 2640 len = seq_file_path(swap, file, " \t\n\\"); 2641 seq_printf(swap, "%*s%s\t%lu\t%s%lu\t%s%d\n", 2642 len < 40 ? 40 - len : 1, " ", 2643 S_ISBLK(file_inode(file)->i_mode) ? 2644 "partition" : "file\t", 2645 bytes, bytes < 10000000 ? "\t" : "", 2646 inuse, inuse < 10000000 ? "\t" : "", 2647 si->prio); 2648 return 0; 2649 } 2650 2651 static const struct seq_operations swaps_op = { 2652 .start = swap_start, 2653 .next = swap_next, 2654 .stop = swap_stop, 2655 .show = swap_show 2656 }; 2657 2658 static int swaps_open(struct inode *inode, struct file *file) 2659 { 2660 struct seq_file *seq; 2661 int ret; 2662 2663 ret = seq_open(file, &swaps_op); 2664 if (ret) 2665 return ret; 2666 2667 seq = file->private_data; 2668 seq->poll_event = atomic_read(&proc_poll_event); 2669 return 0; 2670 } 2671 2672 static const struct proc_ops swaps_proc_ops = { 2673 .proc_flags = PROC_ENTRY_PERMANENT, 2674 .proc_open = swaps_open, 2675 .proc_read = seq_read, 2676 .proc_lseek = seq_lseek, 2677 .proc_release = seq_release, 2678 .proc_poll = swaps_poll, 2679 }; 2680 2681 static int __init procswaps_init(void) 2682 { 2683 proc_create("swaps", 0, NULL, &swaps_proc_ops); 2684 return 0; 2685 } 2686 __initcall(procswaps_init); 2687 #endif /* CONFIG_PROC_FS */ 2688 2689 #ifdef MAX_SWAPFILES_CHECK 2690 static int __init max_swapfiles_check(void) 2691 { 2692 MAX_SWAPFILES_CHECK(); 2693 return 0; 2694 } 2695 late_initcall(max_swapfiles_check); 2696 #endif 2697 2698 static struct swap_info_struct *alloc_swap_info(void) 2699 { 2700 struct swap_info_struct *p; 2701 struct swap_info_struct *defer = NULL; 2702 unsigned int type; 2703 int i; 2704 2705 p = kvzalloc(struct_size(p, avail_lists, nr_node_ids), GFP_KERNEL); 2706 if (!p) 2707 return ERR_PTR(-ENOMEM); 2708 2709 if (percpu_ref_init(&p->users, swap_users_ref_free, 2710 PERCPU_REF_INIT_DEAD, GFP_KERNEL)) { 2711 kvfree(p); 2712 return ERR_PTR(-ENOMEM); 2713 } 2714 2715 spin_lock(&swap_lock); 2716 for (type = 0; type < nr_swapfiles; type++) { 2717 if (!(swap_info[type]->flags & SWP_USED)) 2718 break; 2719 } 2720 if (type >= MAX_SWAPFILES) { 2721 spin_unlock(&swap_lock); 2722 percpu_ref_exit(&p->users); 2723 kvfree(p); 2724 return ERR_PTR(-EPERM); 2725 } 2726 if (type >= nr_swapfiles) { 2727 p->type = type; 2728 /* 2729 * Publish the swap_info_struct after initializing it. 2730 * Note that kvzalloc() above zeroes all its fields. 2731 */ 2732 smp_store_release(&swap_info[type], p); /* rcu_assign_pointer() */ 2733 nr_swapfiles++; 2734 } else { 2735 defer = p; 2736 p = swap_info[type]; 2737 /* 2738 * Do not memset this entry: a racing procfs swap_next() 2739 * would be relying on p->type to remain valid. 2740 */ 2741 } 2742 p->swap_extent_root = RB_ROOT; 2743 plist_node_init(&p->list, 0); 2744 for_each_node(i) 2745 plist_node_init(&p->avail_lists[i], 0); 2746 p->flags = SWP_USED; 2747 spin_unlock(&swap_lock); 2748 if (defer) { 2749 percpu_ref_exit(&defer->users); 2750 kvfree(defer); 2751 } 2752 spin_lock_init(&p->lock); 2753 spin_lock_init(&p->cont_lock); 2754 init_completion(&p->comp); 2755 2756 return p; 2757 } 2758 2759 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) 2760 { 2761 int error; 2762 2763 if (S_ISBLK(inode->i_mode)) { 2764 p->bdev = blkdev_get_by_dev(inode->i_rdev, 2765 FMODE_READ | FMODE_WRITE | FMODE_EXCL, p); 2766 if (IS_ERR(p->bdev)) { 2767 error = PTR_ERR(p->bdev); 2768 p->bdev = NULL; 2769 return error; 2770 } 2771 p->old_block_size = block_size(p->bdev); 2772 error = set_blocksize(p->bdev, PAGE_SIZE); 2773 if (error < 0) 2774 return error; 2775 /* 2776 * Zoned block devices contain zones that have a sequential 2777 * write only restriction. Hence zoned block devices are not 2778 * suitable for swapping. Disallow them here. 2779 */ 2780 if (bdev_is_zoned(p->bdev)) 2781 return -EINVAL; 2782 p->flags |= SWP_BLKDEV; 2783 } else if (S_ISREG(inode->i_mode)) { 2784 p->bdev = inode->i_sb->s_bdev; 2785 } 2786 2787 return 0; 2788 } 2789 2790 2791 /* 2792 * Find out how many pages are allowed for a single swap device. There 2793 * are two limiting factors: 2794 * 1) the number of bits for the swap offset in the swp_entry_t type, and 2795 * 2) the number of bits in the swap pte, as defined by the different 2796 * architectures. 2797 * 2798 * In order to find the largest possible bit mask, a swap entry with 2799 * swap type 0 and swap offset ~0UL is created, encoded to a swap pte, 2800 * decoded to a swp_entry_t again, and finally the swap offset is 2801 * extracted. 2802 * 2803 * This will mask all the bits from the initial ~0UL mask that can't 2804 * be encoded in either the swp_entry_t or the architecture definition 2805 * of a swap pte. 2806 */ 2807 unsigned long generic_max_swapfile_size(void) 2808 { 2809 return swp_offset(pte_to_swp_entry( 2810 swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1; 2811 } 2812 2813 /* Can be overridden by an architecture for additional checks. */ 2814 __weak unsigned long arch_max_swapfile_size(void) 2815 { 2816 return generic_max_swapfile_size(); 2817 } 2818 2819 static unsigned long read_swap_header(struct swap_info_struct *p, 2820 union swap_header *swap_header, 2821 struct inode *inode) 2822 { 2823 int i; 2824 unsigned long maxpages; 2825 unsigned long swapfilepages; 2826 unsigned long last_page; 2827 2828 if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) { 2829 pr_err("Unable to find swap-space signature\n"); 2830 return 0; 2831 } 2832 2833 /* swap partition endianness hack... */ 2834 if (swab32(swap_header->info.version) == 1) { 2835 swab32s(&swap_header->info.version); 2836 swab32s(&swap_header->info.last_page); 2837 swab32s(&swap_header->info.nr_badpages); 2838 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) 2839 return 0; 2840 for (i = 0; i < swap_header->info.nr_badpages; i++) 2841 swab32s(&swap_header->info.badpages[i]); 2842 } 2843 /* Check the swap header's sub-version */ 2844 if (swap_header->info.version != 1) { 2845 pr_warn("Unable to handle swap header version %d\n", 2846 swap_header->info.version); 2847 return 0; 2848 } 2849 2850 p->lowest_bit = 1; 2851 p->cluster_next = 1; 2852 p->cluster_nr = 0; 2853 2854 maxpages = swapfile_maximum_size; 2855 last_page = swap_header->info.last_page; 2856 if (!last_page) { 2857 pr_warn("Empty swap-file\n"); 2858 return 0; 2859 } 2860 if (last_page > maxpages) { 2861 pr_warn("Truncating oversized swap area, only using %luk out of %luk\n", 2862 maxpages << (PAGE_SHIFT - 10), 2863 last_page << (PAGE_SHIFT - 10)); 2864 } 2865 if (maxpages > last_page) { 2866 maxpages = last_page + 1; 2867 /* p->max is an unsigned int: don't overflow it */ 2868 if ((unsigned int)maxpages == 0) 2869 maxpages = UINT_MAX; 2870 } 2871 p->highest_bit = maxpages - 1; 2872 2873 if (!maxpages) 2874 return 0; 2875 swapfilepages = i_size_read(inode) >> PAGE_SHIFT; 2876 if (swapfilepages && maxpages > swapfilepages) { 2877 pr_warn("Swap area shorter than signature indicates\n"); 2878 return 0; 2879 } 2880 if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode)) 2881 return 0; 2882 if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES) 2883 return 0; 2884 2885 return maxpages; 2886 } 2887 2888 #define SWAP_CLUSTER_INFO_COLS \ 2889 DIV_ROUND_UP(L1_CACHE_BYTES, sizeof(struct swap_cluster_info)) 2890 #define SWAP_CLUSTER_SPACE_COLS \ 2891 DIV_ROUND_UP(SWAP_ADDRESS_SPACE_PAGES, SWAPFILE_CLUSTER) 2892 #define SWAP_CLUSTER_COLS \ 2893 max_t(unsigned int, SWAP_CLUSTER_INFO_COLS, SWAP_CLUSTER_SPACE_COLS) 2894 2895 static int setup_swap_map_and_extents(struct swap_info_struct *p, 2896 union swap_header *swap_header, 2897 unsigned char *swap_map, 2898 struct swap_cluster_info *cluster_info, 2899 unsigned long maxpages, 2900 sector_t *span) 2901 { 2902 unsigned int j, k; 2903 unsigned int nr_good_pages; 2904 int nr_extents; 2905 unsigned long nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER); 2906 unsigned long col = p->cluster_next / SWAPFILE_CLUSTER % SWAP_CLUSTER_COLS; 2907 unsigned long i, idx; 2908 2909 nr_good_pages = maxpages - 1; /* omit header page */ 2910 2911 cluster_list_init(&p->free_clusters); 2912 cluster_list_init(&p->discard_clusters); 2913 2914 for (i = 0; i < swap_header->info.nr_badpages; i++) { 2915 unsigned int page_nr = swap_header->info.badpages[i]; 2916 if (page_nr == 0 || page_nr > swap_header->info.last_page) 2917 return -EINVAL; 2918 if (page_nr < maxpages) { 2919 swap_map[page_nr] = SWAP_MAP_BAD; 2920 nr_good_pages--; 2921 /* 2922 * Haven't marked the cluster free yet, no list 2923 * operation involved 2924 */ 2925 inc_cluster_info_page(p, cluster_info, page_nr); 2926 } 2927 } 2928 2929 /* Haven't marked the cluster free yet, no list operation involved */ 2930 for (i = maxpages; i < round_up(maxpages, SWAPFILE_CLUSTER); i++) 2931 inc_cluster_info_page(p, cluster_info, i); 2932 2933 if (nr_good_pages) { 2934 swap_map[0] = SWAP_MAP_BAD; 2935 /* 2936 * Not mark the cluster free yet, no list 2937 * operation involved 2938 */ 2939 inc_cluster_info_page(p, cluster_info, 0); 2940 p->max = maxpages; 2941 p->pages = nr_good_pages; 2942 nr_extents = setup_swap_extents(p, span); 2943 if (nr_extents < 0) 2944 return nr_extents; 2945 nr_good_pages = p->pages; 2946 } 2947 if (!nr_good_pages) { 2948 pr_warn("Empty swap-file\n"); 2949 return -EINVAL; 2950 } 2951 2952 if (!cluster_info) 2953 return nr_extents; 2954 2955 2956 /* 2957 * Reduce false cache line sharing between cluster_info and 2958 * sharing same address space. 2959 */ 2960 for (k = 0; k < SWAP_CLUSTER_COLS; k++) { 2961 j = (k + col) % SWAP_CLUSTER_COLS; 2962 for (i = 0; i < DIV_ROUND_UP(nr_clusters, SWAP_CLUSTER_COLS); i++) { 2963 idx = i * SWAP_CLUSTER_COLS + j; 2964 if (idx >= nr_clusters) 2965 continue; 2966 if (cluster_count(&cluster_info[idx])) 2967 continue; 2968 cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE); 2969 cluster_list_add_tail(&p->free_clusters, cluster_info, 2970 idx); 2971 } 2972 } 2973 return nr_extents; 2974 } 2975 2976 SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 2977 { 2978 struct swap_info_struct *p; 2979 struct filename *name; 2980 struct file *swap_file = NULL; 2981 struct address_space *mapping; 2982 struct dentry *dentry; 2983 int prio; 2984 int error; 2985 union swap_header *swap_header; 2986 int nr_extents; 2987 sector_t span; 2988 unsigned long maxpages; 2989 unsigned char *swap_map = NULL; 2990 struct swap_cluster_info *cluster_info = NULL; 2991 unsigned long *frontswap_map = NULL; 2992 struct page *page = NULL; 2993 struct inode *inode = NULL; 2994 bool inced_nr_rotate_swap = false; 2995 2996 if (swap_flags & ~SWAP_FLAGS_VALID) 2997 return -EINVAL; 2998 2999 if (!capable(CAP_SYS_ADMIN)) 3000 return -EPERM; 3001 3002 if (!swap_avail_heads) 3003 return -ENOMEM; 3004 3005 p = alloc_swap_info(); 3006 if (IS_ERR(p)) 3007 return PTR_ERR(p); 3008 3009 INIT_WORK(&p->discard_work, swap_discard_work); 3010 3011 name = getname(specialfile); 3012 if (IS_ERR(name)) { 3013 error = PTR_ERR(name); 3014 name = NULL; 3015 goto bad_swap; 3016 } 3017 swap_file = file_open_name(name, O_RDWR|O_LARGEFILE, 0); 3018 if (IS_ERR(swap_file)) { 3019 error = PTR_ERR(swap_file); 3020 swap_file = NULL; 3021 goto bad_swap; 3022 } 3023 3024 p->swap_file = swap_file; 3025 mapping = swap_file->f_mapping; 3026 dentry = swap_file->f_path.dentry; 3027 inode = mapping->host; 3028 3029 error = claim_swapfile(p, inode); 3030 if (unlikely(error)) 3031 goto bad_swap; 3032 3033 inode_lock(inode); 3034 if (d_unlinked(dentry) || cant_mount(dentry)) { 3035 error = -ENOENT; 3036 goto bad_swap_unlock_inode; 3037 } 3038 if (IS_SWAPFILE(inode)) { 3039 error = -EBUSY; 3040 goto bad_swap_unlock_inode; 3041 } 3042 3043 /* 3044 * Read the swap header. 3045 */ 3046 if (!mapping->a_ops->read_folio) { 3047 error = -EINVAL; 3048 goto bad_swap_unlock_inode; 3049 } 3050 page = read_mapping_page(mapping, 0, swap_file); 3051 if (IS_ERR(page)) { 3052 error = PTR_ERR(page); 3053 goto bad_swap_unlock_inode; 3054 } 3055 swap_header = kmap(page); 3056 3057 maxpages = read_swap_header(p, swap_header, inode); 3058 if (unlikely(!maxpages)) { 3059 error = -EINVAL; 3060 goto bad_swap_unlock_inode; 3061 } 3062 3063 /* OK, set up the swap map and apply the bad block list */ 3064 swap_map = vzalloc(maxpages); 3065 if (!swap_map) { 3066 error = -ENOMEM; 3067 goto bad_swap_unlock_inode; 3068 } 3069 3070 if (p->bdev && bdev_stable_writes(p->bdev)) 3071 p->flags |= SWP_STABLE_WRITES; 3072 3073 if (p->bdev && p->bdev->bd_disk->fops->rw_page) 3074 p->flags |= SWP_SYNCHRONOUS_IO; 3075 3076 if (p->bdev && bdev_nonrot(p->bdev)) { 3077 int cpu; 3078 unsigned long ci, nr_cluster; 3079 3080 p->flags |= SWP_SOLIDSTATE; 3081 p->cluster_next_cpu = alloc_percpu(unsigned int); 3082 if (!p->cluster_next_cpu) { 3083 error = -ENOMEM; 3084 goto bad_swap_unlock_inode; 3085 } 3086 /* 3087 * select a random position to start with to help wear leveling 3088 * SSD 3089 */ 3090 for_each_possible_cpu(cpu) { 3091 per_cpu(*p->cluster_next_cpu, cpu) = 3092 1 + prandom_u32_max(p->highest_bit); 3093 } 3094 nr_cluster = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER); 3095 3096 cluster_info = kvcalloc(nr_cluster, sizeof(*cluster_info), 3097 GFP_KERNEL); 3098 if (!cluster_info) { 3099 error = -ENOMEM; 3100 goto bad_swap_unlock_inode; 3101 } 3102 3103 for (ci = 0; ci < nr_cluster; ci++) 3104 spin_lock_init(&((cluster_info + ci)->lock)); 3105 3106 p->percpu_cluster = alloc_percpu(struct percpu_cluster); 3107 if (!p->percpu_cluster) { 3108 error = -ENOMEM; 3109 goto bad_swap_unlock_inode; 3110 } 3111 for_each_possible_cpu(cpu) { 3112 struct percpu_cluster *cluster; 3113 cluster = per_cpu_ptr(p->percpu_cluster, cpu); 3114 cluster_set_null(&cluster->index); 3115 } 3116 } else { 3117 atomic_inc(&nr_rotate_swap); 3118 inced_nr_rotate_swap = true; 3119 } 3120 3121 error = swap_cgroup_swapon(p->type, maxpages); 3122 if (error) 3123 goto bad_swap_unlock_inode; 3124 3125 nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map, 3126 cluster_info, maxpages, &span); 3127 if (unlikely(nr_extents < 0)) { 3128 error = nr_extents; 3129 goto bad_swap_unlock_inode; 3130 } 3131 /* frontswap enabled? set up bit-per-page map for frontswap */ 3132 if (IS_ENABLED(CONFIG_FRONTSWAP)) 3133 frontswap_map = kvcalloc(BITS_TO_LONGS(maxpages), 3134 sizeof(long), 3135 GFP_KERNEL); 3136 3137 if ((swap_flags & SWAP_FLAG_DISCARD) && 3138 p->bdev && bdev_max_discard_sectors(p->bdev)) { 3139 /* 3140 * When discard is enabled for swap with no particular 3141 * policy flagged, we set all swap discard flags here in 3142 * order to sustain backward compatibility with older 3143 * swapon(8) releases. 3144 */ 3145 p->flags |= (SWP_DISCARDABLE | SWP_AREA_DISCARD | 3146 SWP_PAGE_DISCARD); 3147 3148 /* 3149 * By flagging sys_swapon, a sysadmin can tell us to 3150 * either do single-time area discards only, or to just 3151 * perform discards for released swap page-clusters. 3152 * Now it's time to adjust the p->flags accordingly. 3153 */ 3154 if (swap_flags & SWAP_FLAG_DISCARD_ONCE) 3155 p->flags &= ~SWP_PAGE_DISCARD; 3156 else if (swap_flags & SWAP_FLAG_DISCARD_PAGES) 3157 p->flags &= ~SWP_AREA_DISCARD; 3158 3159 /* issue a swapon-time discard if it's still required */ 3160 if (p->flags & SWP_AREA_DISCARD) { 3161 int err = discard_swap(p); 3162 if (unlikely(err)) 3163 pr_err("swapon: discard_swap(%p): %d\n", 3164 p, err); 3165 } 3166 } 3167 3168 error = init_swap_address_space(p->type, maxpages); 3169 if (error) 3170 goto bad_swap_unlock_inode; 3171 3172 /* 3173 * Flush any pending IO and dirty mappings before we start using this 3174 * swap device. 3175 */ 3176 inode->i_flags |= S_SWAPFILE; 3177 error = inode_drain_writes(inode); 3178 if (error) { 3179 inode->i_flags &= ~S_SWAPFILE; 3180 goto free_swap_address_space; 3181 } 3182 3183 mutex_lock(&swapon_mutex); 3184 prio = -1; 3185 if (swap_flags & SWAP_FLAG_PREFER) 3186 prio = 3187 (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT; 3188 enable_swap_info(p, prio, swap_map, cluster_info, frontswap_map); 3189 3190 pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s%s\n", 3191 p->pages<<(PAGE_SHIFT-10), name->name, p->prio, 3192 nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10), 3193 (p->flags & SWP_SOLIDSTATE) ? "SS" : "", 3194 (p->flags & SWP_DISCARDABLE) ? "D" : "", 3195 (p->flags & SWP_AREA_DISCARD) ? "s" : "", 3196 (p->flags & SWP_PAGE_DISCARD) ? "c" : "", 3197 (frontswap_map) ? "FS" : ""); 3198 3199 mutex_unlock(&swapon_mutex); 3200 atomic_inc(&proc_poll_event); 3201 wake_up_interruptible(&proc_poll_wait); 3202 3203 error = 0; 3204 goto out; 3205 free_swap_address_space: 3206 exit_swap_address_space(p->type); 3207 bad_swap_unlock_inode: 3208 inode_unlock(inode); 3209 bad_swap: 3210 free_percpu(p->percpu_cluster); 3211 p->percpu_cluster = NULL; 3212 free_percpu(p->cluster_next_cpu); 3213 p->cluster_next_cpu = NULL; 3214 if (inode && S_ISBLK(inode->i_mode) && p->bdev) { 3215 set_blocksize(p->bdev, p->old_block_size); 3216 blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); 3217 } 3218 inode = NULL; 3219 destroy_swap_extents(p); 3220 swap_cgroup_swapoff(p->type); 3221 spin_lock(&swap_lock); 3222 p->swap_file = NULL; 3223 p->flags = 0; 3224 spin_unlock(&swap_lock); 3225 vfree(swap_map); 3226 kvfree(cluster_info); 3227 kvfree(frontswap_map); 3228 if (inced_nr_rotate_swap) 3229 atomic_dec(&nr_rotate_swap); 3230 if (swap_file) 3231 filp_close(swap_file, NULL); 3232 out: 3233 if (page && !IS_ERR(page)) { 3234 kunmap(page); 3235 put_page(page); 3236 } 3237 if (name) 3238 putname(name); 3239 if (inode) 3240 inode_unlock(inode); 3241 if (!error) 3242 enable_swap_slots_cache(); 3243 return error; 3244 } 3245 3246 void si_swapinfo(struct sysinfo *val) 3247 { 3248 unsigned int type; 3249 unsigned long nr_to_be_unused = 0; 3250 3251 spin_lock(&swap_lock); 3252 for (type = 0; type < nr_swapfiles; type++) { 3253 struct swap_info_struct *si = swap_info[type]; 3254 3255 if ((si->flags & SWP_USED) && !(si->flags & SWP_WRITEOK)) 3256 nr_to_be_unused += READ_ONCE(si->inuse_pages); 3257 } 3258 val->freeswap = atomic_long_read(&nr_swap_pages) + nr_to_be_unused; 3259 val->totalswap = total_swap_pages + nr_to_be_unused; 3260 spin_unlock(&swap_lock); 3261 } 3262 3263 /* 3264 * Verify that a swap entry is valid and increment its swap map count. 3265 * 3266 * Returns error code in following case. 3267 * - success -> 0 3268 * - swp_entry is invalid -> EINVAL 3269 * - swp_entry is migration entry -> EINVAL 3270 * - swap-cache reference is requested but there is already one. -> EEXIST 3271 * - swap-cache reference is requested but the entry is not used. -> ENOENT 3272 * - swap-mapped reference requested but needs continued swap count. -> ENOMEM 3273 */ 3274 static int __swap_duplicate(swp_entry_t entry, unsigned char usage) 3275 { 3276 struct swap_info_struct *p; 3277 struct swap_cluster_info *ci; 3278 unsigned long offset; 3279 unsigned char count; 3280 unsigned char has_cache; 3281 int err; 3282 3283 p = get_swap_device(entry); 3284 if (!p) 3285 return -EINVAL; 3286 3287 offset = swp_offset(entry); 3288 ci = lock_cluster_or_swap_info(p, offset); 3289 3290 count = p->swap_map[offset]; 3291 3292 /* 3293 * swapin_readahead() doesn't check if a swap entry is valid, so the 3294 * swap entry could be SWAP_MAP_BAD. Check here with lock held. 3295 */ 3296 if (unlikely(swap_count(count) == SWAP_MAP_BAD)) { 3297 err = -ENOENT; 3298 goto unlock_out; 3299 } 3300 3301 has_cache = count & SWAP_HAS_CACHE; 3302 count &= ~SWAP_HAS_CACHE; 3303 err = 0; 3304 3305 if (usage == SWAP_HAS_CACHE) { 3306 3307 /* set SWAP_HAS_CACHE if there is no cache and entry is used */ 3308 if (!has_cache && count) 3309 has_cache = SWAP_HAS_CACHE; 3310 else if (has_cache) /* someone else added cache */ 3311 err = -EEXIST; 3312 else /* no users remaining */ 3313 err = -ENOENT; 3314 3315 } else if (count || has_cache) { 3316 3317 if ((count & ~COUNT_CONTINUED) < SWAP_MAP_MAX) 3318 count += usage; 3319 else if ((count & ~COUNT_CONTINUED) > SWAP_MAP_MAX) 3320 err = -EINVAL; 3321 else if (swap_count_continued(p, offset, count)) 3322 count = COUNT_CONTINUED; 3323 else 3324 err = -ENOMEM; 3325 } else 3326 err = -ENOENT; /* unused swap entry */ 3327 3328 WRITE_ONCE(p->swap_map[offset], count | has_cache); 3329 3330 unlock_out: 3331 unlock_cluster_or_swap_info(p, ci); 3332 put_swap_device(p); 3333 return err; 3334 } 3335 3336 /* 3337 * Help swapoff by noting that swap entry belongs to shmem/tmpfs 3338 * (in which case its reference count is never incremented). 3339 */ 3340 void swap_shmem_alloc(swp_entry_t entry) 3341 { 3342 __swap_duplicate(entry, SWAP_MAP_SHMEM); 3343 } 3344 3345 /* 3346 * Increase reference count of swap entry by 1. 3347 * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required 3348 * but could not be atomically allocated. Returns 0, just as if it succeeded, 3349 * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which 3350 * might occur if a page table entry has got corrupted. 3351 */ 3352 int swap_duplicate(swp_entry_t entry) 3353 { 3354 int err = 0; 3355 3356 while (!err && __swap_duplicate(entry, 1) == -ENOMEM) 3357 err = add_swap_count_continuation(entry, GFP_ATOMIC); 3358 return err; 3359 } 3360 3361 /* 3362 * @entry: swap entry for which we allocate swap cache. 3363 * 3364 * Called when allocating swap cache for existing swap entry, 3365 * This can return error codes. Returns 0 at success. 3366 * -EEXIST means there is a swap cache. 3367 * Note: return code is different from swap_duplicate(). 3368 */ 3369 int swapcache_prepare(swp_entry_t entry) 3370 { 3371 return __swap_duplicate(entry, SWAP_HAS_CACHE); 3372 } 3373 3374 struct swap_info_struct *swp_swap_info(swp_entry_t entry) 3375 { 3376 return swap_type_to_swap_info(swp_type(entry)); 3377 } 3378 3379 struct swap_info_struct *page_swap_info(struct page *page) 3380 { 3381 swp_entry_t entry = { .val = page_private(page) }; 3382 return swp_swap_info(entry); 3383 } 3384 3385 /* 3386 * out-of-line methods to avoid include hell. 3387 */ 3388 struct address_space *swapcache_mapping(struct folio *folio) 3389 { 3390 return page_swap_info(&folio->page)->swap_file->f_mapping; 3391 } 3392 EXPORT_SYMBOL_GPL(swapcache_mapping); 3393 3394 pgoff_t __page_file_index(struct page *page) 3395 { 3396 swp_entry_t swap = { .val = page_private(page) }; 3397 return swp_offset(swap); 3398 } 3399 EXPORT_SYMBOL_GPL(__page_file_index); 3400 3401 /* 3402 * add_swap_count_continuation - called when a swap count is duplicated 3403 * beyond SWAP_MAP_MAX, it allocates a new page and links that to the entry's 3404 * page of the original vmalloc'ed swap_map, to hold the continuation count 3405 * (for that entry and for its neighbouring PAGE_SIZE swap entries). Called 3406 * again when count is duplicated beyond SWAP_MAP_MAX * SWAP_CONT_MAX, etc. 3407 * 3408 * These continuation pages are seldom referenced: the common paths all work 3409 * on the original swap_map, only referring to a continuation page when the 3410 * low "digit" of a count is incremented or decremented through SWAP_MAP_MAX. 3411 * 3412 * add_swap_count_continuation(, GFP_ATOMIC) can be called while holding 3413 * page table locks; if it fails, add_swap_count_continuation(, GFP_KERNEL) 3414 * can be called after dropping locks. 3415 */ 3416 int add_swap_count_continuation(swp_entry_t entry, gfp_t gfp_mask) 3417 { 3418 struct swap_info_struct *si; 3419 struct swap_cluster_info *ci; 3420 struct page *head; 3421 struct page *page; 3422 struct page *list_page; 3423 pgoff_t offset; 3424 unsigned char count; 3425 int ret = 0; 3426 3427 /* 3428 * When debugging, it's easier to use __GFP_ZERO here; but it's better 3429 * for latency not to zero a page while GFP_ATOMIC and holding locks. 3430 */ 3431 page = alloc_page(gfp_mask | __GFP_HIGHMEM); 3432 3433 si = get_swap_device(entry); 3434 if (!si) { 3435 /* 3436 * An acceptable race has occurred since the failing 3437 * __swap_duplicate(): the swap device may be swapoff 3438 */ 3439 goto outer; 3440 } 3441 spin_lock(&si->lock); 3442 3443 offset = swp_offset(entry); 3444 3445 ci = lock_cluster(si, offset); 3446 3447 count = swap_count(si->swap_map[offset]); 3448 3449 if ((count & ~COUNT_CONTINUED) != SWAP_MAP_MAX) { 3450 /* 3451 * The higher the swap count, the more likely it is that tasks 3452 * will race to add swap count continuation: we need to avoid 3453 * over-provisioning. 3454 */ 3455 goto out; 3456 } 3457 3458 if (!page) { 3459 ret = -ENOMEM; 3460 goto out; 3461 } 3462 3463 /* 3464 * We are fortunate that although vmalloc_to_page uses pte_offset_map, 3465 * no architecture is using highmem pages for kernel page tables: so it 3466 * will not corrupt the GFP_ATOMIC caller's atomic page table kmaps. 3467 */ 3468 head = vmalloc_to_page(si->swap_map + offset); 3469 offset &= ~PAGE_MASK; 3470 3471 spin_lock(&si->cont_lock); 3472 /* 3473 * Page allocation does not initialize the page's lru field, 3474 * but it does always reset its private field. 3475 */ 3476 if (!page_private(head)) { 3477 BUG_ON(count & COUNT_CONTINUED); 3478 INIT_LIST_HEAD(&head->lru); 3479 set_page_private(head, SWP_CONTINUED); 3480 si->flags |= SWP_CONTINUED; 3481 } 3482 3483 list_for_each_entry(list_page, &head->lru, lru) { 3484 unsigned char *map; 3485 3486 /* 3487 * If the previous map said no continuation, but we've found 3488 * a continuation page, free our allocation and use this one. 3489 */ 3490 if (!(count & COUNT_CONTINUED)) 3491 goto out_unlock_cont; 3492 3493 map = kmap_atomic(list_page) + offset; 3494 count = *map; 3495 kunmap_atomic(map); 3496 3497 /* 3498 * If this continuation count now has some space in it, 3499 * free our allocation and use this one. 3500 */ 3501 if ((count & ~COUNT_CONTINUED) != SWAP_CONT_MAX) 3502 goto out_unlock_cont; 3503 } 3504 3505 list_add_tail(&page->lru, &head->lru); 3506 page = NULL; /* now it's attached, don't free it */ 3507 out_unlock_cont: 3508 spin_unlock(&si->cont_lock); 3509 out: 3510 unlock_cluster(ci); 3511 spin_unlock(&si->lock); 3512 put_swap_device(si); 3513 outer: 3514 if (page) 3515 __free_page(page); 3516 return ret; 3517 } 3518 3519 /* 3520 * swap_count_continued - when the original swap_map count is incremented 3521 * from SWAP_MAP_MAX, check if there is already a continuation page to carry 3522 * into, carry if so, or else fail until a new continuation page is allocated; 3523 * when the original swap_map count is decremented from 0 with continuation, 3524 * borrow from the continuation and report whether it still holds more. 3525 * Called while __swap_duplicate() or swap_entry_free() holds swap or cluster 3526 * lock. 3527 */ 3528 static bool swap_count_continued(struct swap_info_struct *si, 3529 pgoff_t offset, unsigned char count) 3530 { 3531 struct page *head; 3532 struct page *page; 3533 unsigned char *map; 3534 bool ret; 3535 3536 head = vmalloc_to_page(si->swap_map + offset); 3537 if (page_private(head) != SWP_CONTINUED) { 3538 BUG_ON(count & COUNT_CONTINUED); 3539 return false; /* need to add count continuation */ 3540 } 3541 3542 spin_lock(&si->cont_lock); 3543 offset &= ~PAGE_MASK; 3544 page = list_next_entry(head, lru); 3545 map = kmap_atomic(page) + offset; 3546 3547 if (count == SWAP_MAP_MAX) /* initial increment from swap_map */ 3548 goto init_map; /* jump over SWAP_CONT_MAX checks */ 3549 3550 if (count == (SWAP_MAP_MAX | COUNT_CONTINUED)) { /* incrementing */ 3551 /* 3552 * Think of how you add 1 to 999 3553 */ 3554 while (*map == (SWAP_CONT_MAX | COUNT_CONTINUED)) { 3555 kunmap_atomic(map); 3556 page = list_next_entry(page, lru); 3557 BUG_ON(page == head); 3558 map = kmap_atomic(page) + offset; 3559 } 3560 if (*map == SWAP_CONT_MAX) { 3561 kunmap_atomic(map); 3562 page = list_next_entry(page, lru); 3563 if (page == head) { 3564 ret = false; /* add count continuation */ 3565 goto out; 3566 } 3567 map = kmap_atomic(page) + offset; 3568 init_map: *map = 0; /* we didn't zero the page */ 3569 } 3570 *map += 1; 3571 kunmap_atomic(map); 3572 while ((page = list_prev_entry(page, lru)) != head) { 3573 map = kmap_atomic(page) + offset; 3574 *map = COUNT_CONTINUED; 3575 kunmap_atomic(map); 3576 } 3577 ret = true; /* incremented */ 3578 3579 } else { /* decrementing */ 3580 /* 3581 * Think of how you subtract 1 from 1000 3582 */ 3583 BUG_ON(count != COUNT_CONTINUED); 3584 while (*map == COUNT_CONTINUED) { 3585 kunmap_atomic(map); 3586 page = list_next_entry(page, lru); 3587 BUG_ON(page == head); 3588 map = kmap_atomic(page) + offset; 3589 } 3590 BUG_ON(*map == 0); 3591 *map -= 1; 3592 if (*map == 0) 3593 count = 0; 3594 kunmap_atomic(map); 3595 while ((page = list_prev_entry(page, lru)) != head) { 3596 map = kmap_atomic(page) + offset; 3597 *map = SWAP_CONT_MAX | count; 3598 count = COUNT_CONTINUED; 3599 kunmap_atomic(map); 3600 } 3601 ret = count == COUNT_CONTINUED; 3602 } 3603 out: 3604 spin_unlock(&si->cont_lock); 3605 return ret; 3606 } 3607 3608 /* 3609 * free_swap_count_continuations - swapoff free all the continuation pages 3610 * appended to the swap_map, after swap_map is quiesced, before vfree'ing it. 3611 */ 3612 static void free_swap_count_continuations(struct swap_info_struct *si) 3613 { 3614 pgoff_t offset; 3615 3616 for (offset = 0; offset < si->max; offset += PAGE_SIZE) { 3617 struct page *head; 3618 head = vmalloc_to_page(si->swap_map + offset); 3619 if (page_private(head)) { 3620 struct page *page, *next; 3621 3622 list_for_each_entry_safe(page, next, &head->lru, lru) { 3623 list_del(&page->lru); 3624 __free_page(page); 3625 } 3626 } 3627 } 3628 } 3629 3630 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP) 3631 void __cgroup_throttle_swaprate(struct page *page, gfp_t gfp_mask) 3632 { 3633 struct swap_info_struct *si, *next; 3634 int nid = page_to_nid(page); 3635 3636 if (!(gfp_mask & __GFP_IO)) 3637 return; 3638 3639 if (!blk_cgroup_congested()) 3640 return; 3641 3642 /* 3643 * We've already scheduled a throttle, avoid taking the global swap 3644 * lock. 3645 */ 3646 if (current->throttle_queue) 3647 return; 3648 3649 spin_lock(&swap_avail_lock); 3650 plist_for_each_entry_safe(si, next, &swap_avail_heads[nid], 3651 avail_lists[nid]) { 3652 if (si->bdev) { 3653 blkcg_schedule_throttle(si->bdev->bd_disk, true); 3654 break; 3655 } 3656 } 3657 spin_unlock(&swap_avail_lock); 3658 } 3659 #endif 3660 3661 static int __init swapfile_init(void) 3662 { 3663 int nid; 3664 3665 swap_avail_heads = kmalloc_array(nr_node_ids, sizeof(struct plist_head), 3666 GFP_KERNEL); 3667 if (!swap_avail_heads) { 3668 pr_emerg("Not enough memory for swap heads, swap is disabled\n"); 3669 return -ENOMEM; 3670 } 3671 3672 for_each_node(nid) 3673 plist_head_init(&swap_avail_heads[nid]); 3674 3675 swapfile_maximum_size = arch_max_swapfile_size(); 3676 3677 #ifdef CONFIG_MIGRATION 3678 if (swapfile_maximum_size >= (1UL << SWP_MIG_TOTAL_BITS)) 3679 swap_migration_ad_supported = true; 3680 #endif /* CONFIG_MIGRATION */ 3681 3682 return 0; 3683 } 3684 subsys_initcall(swapfile_init); 3685