1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * zswap.c - zswap driver file 4 * 5 * zswap is a cache that takes pages that are in the process 6 * of being swapped out and attempts to compress and store them in a 7 * RAM-based memory pool. This can result in a significant I/O reduction on 8 * the swap device and, in the case where decompressing from RAM is faster 9 * than reading from the swap device, can also improve workload performance. 10 * 11 * Copyright (C) 2012 Seth Jennings <sjenning@linux.vnet.ibm.com> 12 */ 13 14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 15 16 #include <linux/module.h> 17 #include <linux/cpu.h> 18 #include <linux/highmem.h> 19 #include <linux/slab.h> 20 #include <linux/spinlock.h> 21 #include <linux/types.h> 22 #include <linux/atomic.h> 23 #include <linux/swap.h> 24 #include <linux/crypto.h> 25 #include <linux/scatterlist.h> 26 #include <linux/mempolicy.h> 27 #include <linux/mempool.h> 28 #include <linux/zpool.h> 29 #include <crypto/acompress.h> 30 #include <linux/zswap.h> 31 #include <linux/mm_types.h> 32 #include <linux/page-flags.h> 33 #include <linux/swapops.h> 34 #include <linux/writeback.h> 35 #include <linux/pagemap.h> 36 #include <linux/workqueue.h> 37 #include <linux/list_lru.h> 38 39 #include "swap.h" 40 #include "internal.h" 41 42 /********************************* 43 * statistics 44 **********************************/ 45 /* The number of compressed pages currently stored in zswap */ 46 atomic_t zswap_stored_pages = ATOMIC_INIT(0); 47 /* The number of same-value filled pages currently stored in zswap */ 48 static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0); 49 50 /* 51 * The statistics below are not protected from concurrent access for 52 * performance reasons so they may not be a 100% accurate. However, 53 * they do provide useful information on roughly how many times a 54 * certain event is occurring. 55 */ 56 57 /* Pool limit was hit (see zswap_max_pool_percent) */ 58 static u64 zswap_pool_limit_hit; 59 /* Pages written back when pool limit was reached */ 60 static u64 zswap_written_back_pages; 61 /* Store failed due to a reclaim failure after pool limit was reached */ 62 static u64 zswap_reject_reclaim_fail; 63 /* Store failed due to compression algorithm failure */ 64 static u64 zswap_reject_compress_fail; 65 /* Compressed page was too big for the allocator to (optimally) store */ 66 static u64 zswap_reject_compress_poor; 67 /* Store failed because underlying allocator could not get memory */ 68 static u64 zswap_reject_alloc_fail; 69 /* Store failed because the entry metadata could not be allocated (rare) */ 70 static u64 zswap_reject_kmemcache_fail; 71 72 /* Shrinker work queue */ 73 static struct workqueue_struct *shrink_wq; 74 /* Pool limit was hit, we need to calm down */ 75 static bool zswap_pool_reached_full; 76 77 /********************************* 78 * tunables 79 **********************************/ 80 81 #define ZSWAP_PARAM_UNSET "" 82 83 static int zswap_setup(void); 84 85 /* Enable/disable zswap */ 86 static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON); 87 static int zswap_enabled_param_set(const char *, 88 const struct kernel_param *); 89 static const struct kernel_param_ops zswap_enabled_param_ops = { 90 .set = zswap_enabled_param_set, 91 .get = param_get_bool, 92 }; 93 module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644); 94 95 /* Crypto compressor to use */ 96 static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT; 97 static int zswap_compressor_param_set(const char *, 98 const struct kernel_param *); 99 static const struct kernel_param_ops zswap_compressor_param_ops = { 100 .set = zswap_compressor_param_set, 101 .get = param_get_charp, 102 .free = param_free_charp, 103 }; 104 module_param_cb(compressor, &zswap_compressor_param_ops, 105 &zswap_compressor, 0644); 106 107 /* Compressed storage zpool to use */ 108 static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT; 109 static int zswap_zpool_param_set(const char *, const struct kernel_param *); 110 static const struct kernel_param_ops zswap_zpool_param_ops = { 111 .set = zswap_zpool_param_set, 112 .get = param_get_charp, 113 .free = param_free_charp, 114 }; 115 module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644); 116 117 /* The maximum percentage of memory that the compressed pool can occupy */ 118 static unsigned int zswap_max_pool_percent = 20; 119 module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644); 120 121 /* The threshold for accepting new pages after the max_pool_percent was hit */ 122 static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */ 123 module_param_named(accept_threshold_percent, zswap_accept_thr_percent, 124 uint, 0644); 125 126 /* Number of zpools in zswap_pool (empirically determined for scalability) */ 127 #define ZSWAP_NR_ZPOOLS 32 128 129 /* Enable/disable memory pressure-based shrinker. */ 130 static bool zswap_shrinker_enabled = IS_ENABLED( 131 CONFIG_ZSWAP_SHRINKER_DEFAULT_ON); 132 module_param_named(shrinker_enabled, zswap_shrinker_enabled, bool, 0644); 133 134 bool is_zswap_enabled(void) 135 { 136 return zswap_enabled; 137 } 138 139 /********************************* 140 * data structures 141 **********************************/ 142 143 struct crypto_acomp_ctx { 144 struct crypto_acomp *acomp; 145 struct acomp_req *req; 146 struct crypto_wait wait; 147 u8 *buffer; 148 struct mutex mutex; 149 bool is_sleepable; 150 }; 151 152 /* 153 * The lock ordering is zswap_tree.lock -> zswap_pool.lru_lock. 154 * The only case where lru_lock is not acquired while holding tree.lock is 155 * when a zswap_entry is taken off the lru for writeback, in that case it 156 * needs to be verified that it's still valid in the tree. 157 */ 158 struct zswap_pool { 159 struct zpool *zpools[ZSWAP_NR_ZPOOLS]; 160 struct crypto_acomp_ctx __percpu *acomp_ctx; 161 struct percpu_ref ref; 162 struct list_head list; 163 struct work_struct release_work; 164 struct hlist_node node; 165 char tfm_name[CRYPTO_MAX_ALG_NAME]; 166 }; 167 168 /* Global LRU lists shared by all zswap pools. */ 169 static struct list_lru zswap_list_lru; 170 171 /* The lock protects zswap_next_shrink updates. */ 172 static DEFINE_SPINLOCK(zswap_shrink_lock); 173 static struct mem_cgroup *zswap_next_shrink; 174 static struct work_struct zswap_shrink_work; 175 static struct shrinker *zswap_shrinker; 176 177 /* 178 * struct zswap_entry 179 * 180 * This structure contains the metadata for tracking a single compressed 181 * page within zswap. 182 * 183 * swpentry - associated swap entry, the offset indexes into the red-black tree 184 * length - the length in bytes of the compressed page data. Needed during 185 * decompression. For a same value filled page length is 0, and both 186 * pool and lru are invalid and must be ignored. 187 * pool - the zswap_pool the entry's data is in 188 * handle - zpool allocation handle that stores the compressed page data 189 * value - value of the same-value filled pages which have same content 190 * objcg - the obj_cgroup that the compressed memory is charged to 191 * lru - handle to the pool's lru used to evict pages. 192 */ 193 struct zswap_entry { 194 swp_entry_t swpentry; 195 unsigned int length; 196 struct zswap_pool *pool; 197 union { 198 unsigned long handle; 199 unsigned long value; 200 }; 201 struct obj_cgroup *objcg; 202 struct list_head lru; 203 }; 204 205 static struct xarray *zswap_trees[MAX_SWAPFILES]; 206 static unsigned int nr_zswap_trees[MAX_SWAPFILES]; 207 208 /* RCU-protected iteration */ 209 static LIST_HEAD(zswap_pools); 210 /* protects zswap_pools list modification */ 211 static DEFINE_SPINLOCK(zswap_pools_lock); 212 /* pool counter to provide unique names to zpool */ 213 static atomic_t zswap_pools_count = ATOMIC_INIT(0); 214 215 enum zswap_init_type { 216 ZSWAP_UNINIT, 217 ZSWAP_INIT_SUCCEED, 218 ZSWAP_INIT_FAILED 219 }; 220 221 static enum zswap_init_type zswap_init_state; 222 223 /* used to ensure the integrity of initialization */ 224 static DEFINE_MUTEX(zswap_init_lock); 225 226 /* init completed, but couldn't create the initial pool */ 227 static bool zswap_has_pool; 228 229 /********************************* 230 * helpers and fwd declarations 231 **********************************/ 232 233 static inline struct xarray *swap_zswap_tree(swp_entry_t swp) 234 { 235 return &zswap_trees[swp_type(swp)][swp_offset(swp) 236 >> SWAP_ADDRESS_SPACE_SHIFT]; 237 } 238 239 #define zswap_pool_debug(msg, p) \ 240 pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \ 241 zpool_get_type((p)->zpools[0])) 242 243 /********************************* 244 * pool functions 245 **********************************/ 246 static void __zswap_pool_empty(struct percpu_ref *ref); 247 248 static struct zswap_pool *zswap_pool_create(char *type, char *compressor) 249 { 250 int i; 251 struct zswap_pool *pool; 252 char name[38]; /* 'zswap' + 32 char (max) num + \0 */ 253 gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM; 254 int ret; 255 256 if (!zswap_has_pool) { 257 /* if either are unset, pool initialization failed, and we 258 * need both params to be set correctly before trying to 259 * create a pool. 260 */ 261 if (!strcmp(type, ZSWAP_PARAM_UNSET)) 262 return NULL; 263 if (!strcmp(compressor, ZSWAP_PARAM_UNSET)) 264 return NULL; 265 } 266 267 pool = kzalloc(sizeof(*pool), GFP_KERNEL); 268 if (!pool) 269 return NULL; 270 271 for (i = 0; i < ZSWAP_NR_ZPOOLS; i++) { 272 /* unique name for each pool specifically required by zsmalloc */ 273 snprintf(name, 38, "zswap%x", 274 atomic_inc_return(&zswap_pools_count)); 275 276 pool->zpools[i] = zpool_create_pool(type, name, gfp); 277 if (!pool->zpools[i]) { 278 pr_err("%s zpool not available\n", type); 279 goto error; 280 } 281 } 282 pr_debug("using %s zpool\n", zpool_get_type(pool->zpools[0])); 283 284 strscpy(pool->tfm_name, compressor, sizeof(pool->tfm_name)); 285 286 pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx); 287 if (!pool->acomp_ctx) { 288 pr_err("percpu alloc failed\n"); 289 goto error; 290 } 291 292 ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE, 293 &pool->node); 294 if (ret) 295 goto error; 296 297 /* being the current pool takes 1 ref; this func expects the 298 * caller to always add the new pool as the current pool 299 */ 300 ret = percpu_ref_init(&pool->ref, __zswap_pool_empty, 301 PERCPU_REF_ALLOW_REINIT, GFP_KERNEL); 302 if (ret) 303 goto ref_fail; 304 INIT_LIST_HEAD(&pool->list); 305 306 zswap_pool_debug("created", pool); 307 308 return pool; 309 310 ref_fail: 311 cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node); 312 error: 313 if (pool->acomp_ctx) 314 free_percpu(pool->acomp_ctx); 315 while (i--) 316 zpool_destroy_pool(pool->zpools[i]); 317 kfree(pool); 318 return NULL; 319 } 320 321 static struct zswap_pool *__zswap_pool_create_fallback(void) 322 { 323 bool has_comp, has_zpool; 324 325 has_comp = crypto_has_acomp(zswap_compressor, 0, 0); 326 if (!has_comp && strcmp(zswap_compressor, 327 CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) { 328 pr_err("compressor %s not available, using default %s\n", 329 zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT); 330 param_free_charp(&zswap_compressor); 331 zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT; 332 has_comp = crypto_has_acomp(zswap_compressor, 0, 0); 333 } 334 if (!has_comp) { 335 pr_err("default compressor %s not available\n", 336 zswap_compressor); 337 param_free_charp(&zswap_compressor); 338 zswap_compressor = ZSWAP_PARAM_UNSET; 339 } 340 341 has_zpool = zpool_has_pool(zswap_zpool_type); 342 if (!has_zpool && strcmp(zswap_zpool_type, 343 CONFIG_ZSWAP_ZPOOL_DEFAULT)) { 344 pr_err("zpool %s not available, using default %s\n", 345 zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT); 346 param_free_charp(&zswap_zpool_type); 347 zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT; 348 has_zpool = zpool_has_pool(zswap_zpool_type); 349 } 350 if (!has_zpool) { 351 pr_err("default zpool %s not available\n", 352 zswap_zpool_type); 353 param_free_charp(&zswap_zpool_type); 354 zswap_zpool_type = ZSWAP_PARAM_UNSET; 355 } 356 357 if (!has_comp || !has_zpool) 358 return NULL; 359 360 return zswap_pool_create(zswap_zpool_type, zswap_compressor); 361 } 362 363 static void zswap_pool_destroy(struct zswap_pool *pool) 364 { 365 int i; 366 367 zswap_pool_debug("destroying", pool); 368 369 cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node); 370 free_percpu(pool->acomp_ctx); 371 372 for (i = 0; i < ZSWAP_NR_ZPOOLS; i++) 373 zpool_destroy_pool(pool->zpools[i]); 374 kfree(pool); 375 } 376 377 static void __zswap_pool_release(struct work_struct *work) 378 { 379 struct zswap_pool *pool = container_of(work, typeof(*pool), 380 release_work); 381 382 synchronize_rcu(); 383 384 /* nobody should have been able to get a ref... */ 385 WARN_ON(!percpu_ref_is_zero(&pool->ref)); 386 percpu_ref_exit(&pool->ref); 387 388 /* pool is now off zswap_pools list and has no references. */ 389 zswap_pool_destroy(pool); 390 } 391 392 static struct zswap_pool *zswap_pool_current(void); 393 394 static void __zswap_pool_empty(struct percpu_ref *ref) 395 { 396 struct zswap_pool *pool; 397 398 pool = container_of(ref, typeof(*pool), ref); 399 400 spin_lock_bh(&zswap_pools_lock); 401 402 WARN_ON(pool == zswap_pool_current()); 403 404 list_del_rcu(&pool->list); 405 406 INIT_WORK(&pool->release_work, __zswap_pool_release); 407 schedule_work(&pool->release_work); 408 409 spin_unlock_bh(&zswap_pools_lock); 410 } 411 412 static int __must_check zswap_pool_get(struct zswap_pool *pool) 413 { 414 if (!pool) 415 return 0; 416 417 return percpu_ref_tryget(&pool->ref); 418 } 419 420 static void zswap_pool_put(struct zswap_pool *pool) 421 { 422 percpu_ref_put(&pool->ref); 423 } 424 425 static struct zswap_pool *__zswap_pool_current(void) 426 { 427 struct zswap_pool *pool; 428 429 pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list); 430 WARN_ONCE(!pool && zswap_has_pool, 431 "%s: no page storage pool!\n", __func__); 432 433 return pool; 434 } 435 436 static struct zswap_pool *zswap_pool_current(void) 437 { 438 assert_spin_locked(&zswap_pools_lock); 439 440 return __zswap_pool_current(); 441 } 442 443 static struct zswap_pool *zswap_pool_current_get(void) 444 { 445 struct zswap_pool *pool; 446 447 rcu_read_lock(); 448 449 pool = __zswap_pool_current(); 450 if (!zswap_pool_get(pool)) 451 pool = NULL; 452 453 rcu_read_unlock(); 454 455 return pool; 456 } 457 458 /* type and compressor must be null-terminated */ 459 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor) 460 { 461 struct zswap_pool *pool; 462 463 assert_spin_locked(&zswap_pools_lock); 464 465 list_for_each_entry_rcu(pool, &zswap_pools, list) { 466 if (strcmp(pool->tfm_name, compressor)) 467 continue; 468 /* all zpools share the same type */ 469 if (strcmp(zpool_get_type(pool->zpools[0]), type)) 470 continue; 471 /* if we can't get it, it's about to be destroyed */ 472 if (!zswap_pool_get(pool)) 473 continue; 474 return pool; 475 } 476 477 return NULL; 478 } 479 480 static unsigned long zswap_max_pages(void) 481 { 482 return totalram_pages() * zswap_max_pool_percent / 100; 483 } 484 485 static unsigned long zswap_accept_thr_pages(void) 486 { 487 return zswap_max_pages() * zswap_accept_thr_percent / 100; 488 } 489 490 unsigned long zswap_total_pages(void) 491 { 492 struct zswap_pool *pool; 493 unsigned long total = 0; 494 495 rcu_read_lock(); 496 list_for_each_entry_rcu(pool, &zswap_pools, list) { 497 int i; 498 499 for (i = 0; i < ZSWAP_NR_ZPOOLS; i++) 500 total += zpool_get_total_pages(pool->zpools[i]); 501 } 502 rcu_read_unlock(); 503 504 return total; 505 } 506 507 static bool zswap_check_limits(void) 508 { 509 unsigned long cur_pages = zswap_total_pages(); 510 unsigned long max_pages = zswap_max_pages(); 511 512 if (cur_pages >= max_pages) { 513 zswap_pool_limit_hit++; 514 zswap_pool_reached_full = true; 515 } else if (zswap_pool_reached_full && 516 cur_pages <= zswap_accept_thr_pages()) { 517 zswap_pool_reached_full = false; 518 } 519 return zswap_pool_reached_full; 520 } 521 522 /********************************* 523 * param callbacks 524 **********************************/ 525 526 static bool zswap_pool_changed(const char *s, const struct kernel_param *kp) 527 { 528 /* no change required */ 529 if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool) 530 return false; 531 return true; 532 } 533 534 /* val must be a null-terminated string */ 535 static int __zswap_param_set(const char *val, const struct kernel_param *kp, 536 char *type, char *compressor) 537 { 538 struct zswap_pool *pool, *put_pool = NULL; 539 char *s = strstrip((char *)val); 540 int ret = 0; 541 bool new_pool = false; 542 543 mutex_lock(&zswap_init_lock); 544 switch (zswap_init_state) { 545 case ZSWAP_UNINIT: 546 /* if this is load-time (pre-init) param setting, 547 * don't create a pool; that's done during init. 548 */ 549 ret = param_set_charp(s, kp); 550 break; 551 case ZSWAP_INIT_SUCCEED: 552 new_pool = zswap_pool_changed(s, kp); 553 break; 554 case ZSWAP_INIT_FAILED: 555 pr_err("can't set param, initialization failed\n"); 556 ret = -ENODEV; 557 } 558 mutex_unlock(&zswap_init_lock); 559 560 /* no need to create a new pool, return directly */ 561 if (!new_pool) 562 return ret; 563 564 if (!type) { 565 if (!zpool_has_pool(s)) { 566 pr_err("zpool %s not available\n", s); 567 return -ENOENT; 568 } 569 type = s; 570 } else if (!compressor) { 571 if (!crypto_has_acomp(s, 0, 0)) { 572 pr_err("compressor %s not available\n", s); 573 return -ENOENT; 574 } 575 compressor = s; 576 } else { 577 WARN_ON(1); 578 return -EINVAL; 579 } 580 581 spin_lock_bh(&zswap_pools_lock); 582 583 pool = zswap_pool_find_get(type, compressor); 584 if (pool) { 585 zswap_pool_debug("using existing", pool); 586 WARN_ON(pool == zswap_pool_current()); 587 list_del_rcu(&pool->list); 588 } 589 590 spin_unlock_bh(&zswap_pools_lock); 591 592 if (!pool) 593 pool = zswap_pool_create(type, compressor); 594 else { 595 /* 596 * Restore the initial ref dropped by percpu_ref_kill() 597 * when the pool was decommissioned and switch it again 598 * to percpu mode. 599 */ 600 percpu_ref_resurrect(&pool->ref); 601 602 /* Drop the ref from zswap_pool_find_get(). */ 603 zswap_pool_put(pool); 604 } 605 606 if (pool) 607 ret = param_set_charp(s, kp); 608 else 609 ret = -EINVAL; 610 611 spin_lock_bh(&zswap_pools_lock); 612 613 if (!ret) { 614 put_pool = zswap_pool_current(); 615 list_add_rcu(&pool->list, &zswap_pools); 616 zswap_has_pool = true; 617 } else if (pool) { 618 /* add the possibly pre-existing pool to the end of the pools 619 * list; if it's new (and empty) then it'll be removed and 620 * destroyed by the put after we drop the lock 621 */ 622 list_add_tail_rcu(&pool->list, &zswap_pools); 623 put_pool = pool; 624 } 625 626 spin_unlock_bh(&zswap_pools_lock); 627 628 if (!zswap_has_pool && !pool) { 629 /* if initial pool creation failed, and this pool creation also 630 * failed, maybe both compressor and zpool params were bad. 631 * Allow changing this param, so pool creation will succeed 632 * when the other param is changed. We already verified this 633 * param is ok in the zpool_has_pool() or crypto_has_acomp() 634 * checks above. 635 */ 636 ret = param_set_charp(s, kp); 637 } 638 639 /* drop the ref from either the old current pool, 640 * or the new pool we failed to add 641 */ 642 if (put_pool) 643 percpu_ref_kill(&put_pool->ref); 644 645 return ret; 646 } 647 648 static int zswap_compressor_param_set(const char *val, 649 const struct kernel_param *kp) 650 { 651 return __zswap_param_set(val, kp, zswap_zpool_type, NULL); 652 } 653 654 static int zswap_zpool_param_set(const char *val, 655 const struct kernel_param *kp) 656 { 657 return __zswap_param_set(val, kp, NULL, zswap_compressor); 658 } 659 660 static int zswap_enabled_param_set(const char *val, 661 const struct kernel_param *kp) 662 { 663 int ret = -ENODEV; 664 665 /* if this is load-time (pre-init) param setting, only set param. */ 666 if (system_state != SYSTEM_RUNNING) 667 return param_set_bool(val, kp); 668 669 mutex_lock(&zswap_init_lock); 670 switch (zswap_init_state) { 671 case ZSWAP_UNINIT: 672 if (zswap_setup()) 673 break; 674 fallthrough; 675 case ZSWAP_INIT_SUCCEED: 676 if (!zswap_has_pool) 677 pr_err("can't enable, no pool configured\n"); 678 else 679 ret = param_set_bool(val, kp); 680 break; 681 case ZSWAP_INIT_FAILED: 682 pr_err("can't enable, initialization failed\n"); 683 } 684 mutex_unlock(&zswap_init_lock); 685 686 return ret; 687 } 688 689 /********************************* 690 * lru functions 691 **********************************/ 692 693 /* should be called under RCU */ 694 #ifdef CONFIG_MEMCG 695 static inline struct mem_cgroup *mem_cgroup_from_entry(struct zswap_entry *entry) 696 { 697 return entry->objcg ? obj_cgroup_memcg(entry->objcg) : NULL; 698 } 699 #else 700 static inline struct mem_cgroup *mem_cgroup_from_entry(struct zswap_entry *entry) 701 { 702 return NULL; 703 } 704 #endif 705 706 static inline int entry_to_nid(struct zswap_entry *entry) 707 { 708 return page_to_nid(virt_to_page(entry)); 709 } 710 711 static void zswap_lru_add(struct list_lru *list_lru, struct zswap_entry *entry) 712 { 713 atomic_long_t *nr_zswap_protected; 714 unsigned long lru_size, old, new; 715 int nid = entry_to_nid(entry); 716 struct mem_cgroup *memcg; 717 struct lruvec *lruvec; 718 719 /* 720 * Note that it is safe to use rcu_read_lock() here, even in the face of 721 * concurrent memcg offlining. Thanks to the memcg->kmemcg_id indirection 722 * used in list_lru lookup, only two scenarios are possible: 723 * 724 * 1. list_lru_add() is called before memcg->kmemcg_id is updated. The 725 * new entry will be reparented to memcg's parent's list_lru. 726 * 2. list_lru_add() is called after memcg->kmemcg_id is updated. The 727 * new entry will be added directly to memcg's parent's list_lru. 728 * 729 * Similar reasoning holds for list_lru_del(). 730 */ 731 rcu_read_lock(); 732 memcg = mem_cgroup_from_entry(entry); 733 /* will always succeed */ 734 list_lru_add(list_lru, &entry->lru, nid, memcg); 735 736 /* Update the protection area */ 737 lru_size = list_lru_count_one(list_lru, nid, memcg); 738 lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(nid)); 739 nr_zswap_protected = &lruvec->zswap_lruvec_state.nr_zswap_protected; 740 old = atomic_long_inc_return(nr_zswap_protected); 741 /* 742 * Decay to avoid overflow and adapt to changing workloads. 743 * This is based on LRU reclaim cost decaying heuristics. 744 */ 745 do { 746 new = old > lru_size / 4 ? old / 2 : old; 747 } while (!atomic_long_try_cmpxchg(nr_zswap_protected, &old, new)); 748 rcu_read_unlock(); 749 } 750 751 static void zswap_lru_del(struct list_lru *list_lru, struct zswap_entry *entry) 752 { 753 int nid = entry_to_nid(entry); 754 struct mem_cgroup *memcg; 755 756 rcu_read_lock(); 757 memcg = mem_cgroup_from_entry(entry); 758 /* will always succeed */ 759 list_lru_del(list_lru, &entry->lru, nid, memcg); 760 rcu_read_unlock(); 761 } 762 763 void zswap_lruvec_state_init(struct lruvec *lruvec) 764 { 765 atomic_long_set(&lruvec->zswap_lruvec_state.nr_zswap_protected, 0); 766 } 767 768 void zswap_folio_swapin(struct folio *folio) 769 { 770 struct lruvec *lruvec; 771 772 if (folio) { 773 lruvec = folio_lruvec(folio); 774 atomic_long_inc(&lruvec->zswap_lruvec_state.nr_zswap_protected); 775 } 776 } 777 778 void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg) 779 { 780 /* lock out zswap shrinker walking memcg tree */ 781 spin_lock(&zswap_shrink_lock); 782 if (zswap_next_shrink == memcg) 783 zswap_next_shrink = mem_cgroup_iter(NULL, zswap_next_shrink, NULL); 784 spin_unlock(&zswap_shrink_lock); 785 } 786 787 /********************************* 788 * zswap entry functions 789 **********************************/ 790 static struct kmem_cache *zswap_entry_cache; 791 792 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp, int nid) 793 { 794 struct zswap_entry *entry; 795 entry = kmem_cache_alloc_node(zswap_entry_cache, gfp, nid); 796 if (!entry) 797 return NULL; 798 return entry; 799 } 800 801 static void zswap_entry_cache_free(struct zswap_entry *entry) 802 { 803 kmem_cache_free(zswap_entry_cache, entry); 804 } 805 806 static struct zpool *zswap_find_zpool(struct zswap_entry *entry) 807 { 808 return entry->pool->zpools[hash_ptr(entry, ilog2(ZSWAP_NR_ZPOOLS))]; 809 } 810 811 /* 812 * Carries out the common pattern of freeing and entry's zpool allocation, 813 * freeing the entry itself, and decrementing the number of stored pages. 814 */ 815 static void zswap_entry_free(struct zswap_entry *entry) 816 { 817 if (!entry->length) 818 atomic_dec(&zswap_same_filled_pages); 819 else { 820 zswap_lru_del(&zswap_list_lru, entry); 821 zpool_free(zswap_find_zpool(entry), entry->handle); 822 zswap_pool_put(entry->pool); 823 } 824 if (entry->objcg) { 825 obj_cgroup_uncharge_zswap(entry->objcg, entry->length); 826 obj_cgroup_put(entry->objcg); 827 } 828 zswap_entry_cache_free(entry); 829 atomic_dec(&zswap_stored_pages); 830 } 831 832 /********************************* 833 * compressed storage functions 834 **********************************/ 835 static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node) 836 { 837 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node); 838 struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu); 839 struct crypto_acomp *acomp; 840 struct acomp_req *req; 841 int ret; 842 843 mutex_init(&acomp_ctx->mutex); 844 845 acomp_ctx->buffer = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu)); 846 if (!acomp_ctx->buffer) 847 return -ENOMEM; 848 849 acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu)); 850 if (IS_ERR(acomp)) { 851 pr_err("could not alloc crypto acomp %s : %ld\n", 852 pool->tfm_name, PTR_ERR(acomp)); 853 ret = PTR_ERR(acomp); 854 goto acomp_fail; 855 } 856 acomp_ctx->acomp = acomp; 857 acomp_ctx->is_sleepable = acomp_is_async(acomp); 858 859 req = acomp_request_alloc(acomp_ctx->acomp); 860 if (!req) { 861 pr_err("could not alloc crypto acomp_request %s\n", 862 pool->tfm_name); 863 ret = -ENOMEM; 864 goto req_fail; 865 } 866 acomp_ctx->req = req; 867 868 crypto_init_wait(&acomp_ctx->wait); 869 /* 870 * if the backend of acomp is async zip, crypto_req_done() will wakeup 871 * crypto_wait_req(); if the backend of acomp is scomp, the callback 872 * won't be called, crypto_wait_req() will return without blocking. 873 */ 874 acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, 875 crypto_req_done, &acomp_ctx->wait); 876 877 return 0; 878 879 req_fail: 880 crypto_free_acomp(acomp_ctx->acomp); 881 acomp_fail: 882 kfree(acomp_ctx->buffer); 883 return ret; 884 } 885 886 static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node) 887 { 888 struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node); 889 struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu); 890 891 if (!IS_ERR_OR_NULL(acomp_ctx)) { 892 if (!IS_ERR_OR_NULL(acomp_ctx->req)) 893 acomp_request_free(acomp_ctx->req); 894 if (!IS_ERR_OR_NULL(acomp_ctx->acomp)) 895 crypto_free_acomp(acomp_ctx->acomp); 896 kfree(acomp_ctx->buffer); 897 } 898 899 return 0; 900 } 901 902 static bool zswap_compress(struct folio *folio, struct zswap_entry *entry) 903 { 904 struct crypto_acomp_ctx *acomp_ctx; 905 struct scatterlist input, output; 906 int comp_ret = 0, alloc_ret = 0; 907 unsigned int dlen = PAGE_SIZE; 908 unsigned long handle; 909 struct zpool *zpool; 910 char *buf; 911 gfp_t gfp; 912 u8 *dst; 913 914 acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx); 915 916 mutex_lock(&acomp_ctx->mutex); 917 918 dst = acomp_ctx->buffer; 919 sg_init_table(&input, 1); 920 sg_set_page(&input, &folio->page, PAGE_SIZE, 0); 921 922 /* 923 * We need PAGE_SIZE * 2 here since there maybe over-compression case, 924 * and hardware-accelerators may won't check the dst buffer size, so 925 * giving the dst buffer with enough length to avoid buffer overflow. 926 */ 927 sg_init_one(&output, dst, PAGE_SIZE * 2); 928 acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen); 929 930 /* 931 * it maybe looks a little bit silly that we send an asynchronous request, 932 * then wait for its completion synchronously. This makes the process look 933 * synchronous in fact. 934 * Theoretically, acomp supports users send multiple acomp requests in one 935 * acomp instance, then get those requests done simultaneously. but in this 936 * case, zswap actually does store and load page by page, there is no 937 * existing method to send the second page before the first page is done 938 * in one thread doing zwap. 939 * but in different threads running on different cpu, we have different 940 * acomp instance, so multiple threads can do (de)compression in parallel. 941 */ 942 comp_ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait); 943 dlen = acomp_ctx->req->dlen; 944 if (comp_ret) 945 goto unlock; 946 947 zpool = zswap_find_zpool(entry); 948 gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM; 949 if (zpool_malloc_support_movable(zpool)) 950 gfp |= __GFP_HIGHMEM | __GFP_MOVABLE; 951 alloc_ret = zpool_malloc(zpool, dlen, gfp, &handle); 952 if (alloc_ret) 953 goto unlock; 954 955 buf = zpool_map_handle(zpool, handle, ZPOOL_MM_WO); 956 memcpy(buf, dst, dlen); 957 zpool_unmap_handle(zpool, handle); 958 959 entry->handle = handle; 960 entry->length = dlen; 961 962 unlock: 963 if (comp_ret == -ENOSPC || alloc_ret == -ENOSPC) 964 zswap_reject_compress_poor++; 965 else if (comp_ret) 966 zswap_reject_compress_fail++; 967 else if (alloc_ret) 968 zswap_reject_alloc_fail++; 969 970 mutex_unlock(&acomp_ctx->mutex); 971 return comp_ret == 0 && alloc_ret == 0; 972 } 973 974 static void zswap_decompress(struct zswap_entry *entry, struct page *page) 975 { 976 struct zpool *zpool = zswap_find_zpool(entry); 977 struct scatterlist input, output; 978 struct crypto_acomp_ctx *acomp_ctx; 979 u8 *src; 980 981 acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx); 982 mutex_lock(&acomp_ctx->mutex); 983 984 src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO); 985 /* 986 * If zpool_map_handle is atomic, we cannot reliably utilize its mapped buffer 987 * to do crypto_acomp_decompress() which might sleep. In such cases, we must 988 * resort to copying the buffer to a temporary one. 989 * Meanwhile, zpool_map_handle() might return a non-linearly mapped buffer, 990 * such as a kmap address of high memory or even ever a vmap address. 991 * However, sg_init_one is only equipped to handle linearly mapped low memory. 992 * In such cases, we also must copy the buffer to a temporary and lowmem one. 993 */ 994 if ((acomp_ctx->is_sleepable && !zpool_can_sleep_mapped(zpool)) || 995 !virt_addr_valid(src)) { 996 memcpy(acomp_ctx->buffer, src, entry->length); 997 src = acomp_ctx->buffer; 998 zpool_unmap_handle(zpool, entry->handle); 999 } 1000 1001 sg_init_one(&input, src, entry->length); 1002 sg_init_table(&output, 1); 1003 sg_set_page(&output, page, PAGE_SIZE, 0); 1004 acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, PAGE_SIZE); 1005 BUG_ON(crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait)); 1006 BUG_ON(acomp_ctx->req->dlen != PAGE_SIZE); 1007 mutex_unlock(&acomp_ctx->mutex); 1008 1009 if (src != acomp_ctx->buffer) 1010 zpool_unmap_handle(zpool, entry->handle); 1011 } 1012 1013 /********************************* 1014 * writeback code 1015 **********************************/ 1016 /* 1017 * Attempts to free an entry by adding a folio to the swap cache, 1018 * decompressing the entry data into the folio, and issuing a 1019 * bio write to write the folio back to the swap device. 1020 * 1021 * This can be thought of as a "resumed writeback" of the folio 1022 * to the swap device. We are basically resuming the same swap 1023 * writeback path that was intercepted with the zswap_store() 1024 * in the first place. After the folio has been decompressed into 1025 * the swap cache, the compressed version stored by zswap can be 1026 * freed. 1027 */ 1028 static int zswap_writeback_entry(struct zswap_entry *entry, 1029 swp_entry_t swpentry) 1030 { 1031 struct xarray *tree; 1032 pgoff_t offset = swp_offset(swpentry); 1033 struct folio *folio; 1034 struct mempolicy *mpol; 1035 bool folio_was_allocated; 1036 struct writeback_control wbc = { 1037 .sync_mode = WB_SYNC_NONE, 1038 }; 1039 1040 /* try to allocate swap cache folio */ 1041 mpol = get_task_policy(current); 1042 folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol, 1043 NO_INTERLEAVE_INDEX, &folio_was_allocated, true); 1044 if (!folio) 1045 return -ENOMEM; 1046 1047 /* 1048 * Found an existing folio, we raced with swapin or concurrent 1049 * shrinker. We generally writeback cold folios from zswap, and 1050 * swapin means the folio just became hot, so skip this folio. 1051 * For unlikely concurrent shrinker case, it will be unlinked 1052 * and freed when invalidated by the concurrent shrinker anyway. 1053 */ 1054 if (!folio_was_allocated) { 1055 folio_put(folio); 1056 return -EEXIST; 1057 } 1058 1059 /* 1060 * folio is locked, and the swapcache is now secured against 1061 * concurrent swapping to and from the slot, and concurrent 1062 * swapoff so we can safely dereference the zswap tree here. 1063 * Verify that the swap entry hasn't been invalidated and recycled 1064 * behind our backs, to avoid overwriting a new swap folio with 1065 * old compressed data. Only when this is successful can the entry 1066 * be dereferenced. 1067 */ 1068 tree = swap_zswap_tree(swpentry); 1069 if (entry != xa_cmpxchg(tree, offset, entry, NULL, GFP_KERNEL)) { 1070 delete_from_swap_cache(folio); 1071 folio_unlock(folio); 1072 folio_put(folio); 1073 return -ENOMEM; 1074 } 1075 1076 zswap_decompress(entry, &folio->page); 1077 1078 count_vm_event(ZSWPWB); 1079 if (entry->objcg) 1080 count_objcg_event(entry->objcg, ZSWPWB); 1081 1082 zswap_entry_free(entry); 1083 1084 /* folio is up to date */ 1085 folio_mark_uptodate(folio); 1086 1087 /* move it to the tail of the inactive list after end_writeback */ 1088 folio_set_reclaim(folio); 1089 1090 /* start writeback */ 1091 __swap_writepage(folio, &wbc); 1092 folio_put(folio); 1093 1094 return 0; 1095 } 1096 1097 /********************************* 1098 * shrinker functions 1099 **********************************/ 1100 static enum lru_status shrink_memcg_cb(struct list_head *item, struct list_lru_one *l, 1101 spinlock_t *lock, void *arg) 1102 { 1103 struct zswap_entry *entry = container_of(item, struct zswap_entry, lru); 1104 bool *encountered_page_in_swapcache = (bool *)arg; 1105 swp_entry_t swpentry; 1106 enum lru_status ret = LRU_REMOVED_RETRY; 1107 int writeback_result; 1108 1109 /* 1110 * As soon as we drop the LRU lock, the entry can be freed by 1111 * a concurrent invalidation. This means the following: 1112 * 1113 * 1. We extract the swp_entry_t to the stack, allowing 1114 * zswap_writeback_entry() to pin the swap entry and 1115 * then validate the zwap entry against that swap entry's 1116 * tree using pointer value comparison. Only when that 1117 * is successful can the entry be dereferenced. 1118 * 1119 * 2. Usually, objects are taken off the LRU for reclaim. In 1120 * this case this isn't possible, because if reclaim fails 1121 * for whatever reason, we have no means of knowing if the 1122 * entry is alive to put it back on the LRU. 1123 * 1124 * So rotate it before dropping the lock. If the entry is 1125 * written back or invalidated, the free path will unlink 1126 * it. For failures, rotation is the right thing as well. 1127 * 1128 * Temporary failures, where the same entry should be tried 1129 * again immediately, almost never happen for this shrinker. 1130 * We don't do any trylocking; -ENOMEM comes closest, 1131 * but that's extremely rare and doesn't happen spuriously 1132 * either. Don't bother distinguishing this case. 1133 */ 1134 list_move_tail(item, &l->list); 1135 1136 /* 1137 * Once the lru lock is dropped, the entry might get freed. The 1138 * swpentry is copied to the stack, and entry isn't deref'd again 1139 * until the entry is verified to still be alive in the tree. 1140 */ 1141 swpentry = entry->swpentry; 1142 1143 /* 1144 * It's safe to drop the lock here because we return either 1145 * LRU_REMOVED_RETRY or LRU_RETRY. 1146 */ 1147 spin_unlock(lock); 1148 1149 writeback_result = zswap_writeback_entry(entry, swpentry); 1150 1151 if (writeback_result) { 1152 zswap_reject_reclaim_fail++; 1153 ret = LRU_RETRY; 1154 1155 /* 1156 * Encountering a page already in swap cache is a sign that we are shrinking 1157 * into the warmer region. We should terminate shrinking (if we're in the dynamic 1158 * shrinker context). 1159 */ 1160 if (writeback_result == -EEXIST && encountered_page_in_swapcache) { 1161 ret = LRU_STOP; 1162 *encountered_page_in_swapcache = true; 1163 } 1164 } else { 1165 zswap_written_back_pages++; 1166 } 1167 1168 spin_lock(lock); 1169 return ret; 1170 } 1171 1172 static unsigned long zswap_shrinker_scan(struct shrinker *shrinker, 1173 struct shrink_control *sc) 1174 { 1175 struct lruvec *lruvec = mem_cgroup_lruvec(sc->memcg, NODE_DATA(sc->nid)); 1176 unsigned long shrink_ret, nr_protected, lru_size; 1177 bool encountered_page_in_swapcache = false; 1178 1179 if (!zswap_shrinker_enabled || 1180 !mem_cgroup_zswap_writeback_enabled(sc->memcg)) { 1181 sc->nr_scanned = 0; 1182 return SHRINK_STOP; 1183 } 1184 1185 nr_protected = 1186 atomic_long_read(&lruvec->zswap_lruvec_state.nr_zswap_protected); 1187 lru_size = list_lru_shrink_count(&zswap_list_lru, sc); 1188 1189 /* 1190 * Abort if we are shrinking into the protected region. 1191 * 1192 * This short-circuiting is necessary because if we have too many multiple 1193 * concurrent reclaimers getting the freeable zswap object counts at the 1194 * same time (before any of them made reasonable progress), the total 1195 * number of reclaimed objects might be more than the number of unprotected 1196 * objects (i.e the reclaimers will reclaim into the protected area of the 1197 * zswap LRU). 1198 */ 1199 if (nr_protected >= lru_size - sc->nr_to_scan) { 1200 sc->nr_scanned = 0; 1201 return SHRINK_STOP; 1202 } 1203 1204 shrink_ret = list_lru_shrink_walk(&zswap_list_lru, sc, &shrink_memcg_cb, 1205 &encountered_page_in_swapcache); 1206 1207 if (encountered_page_in_swapcache) 1208 return SHRINK_STOP; 1209 1210 return shrink_ret ? shrink_ret : SHRINK_STOP; 1211 } 1212 1213 static unsigned long zswap_shrinker_count(struct shrinker *shrinker, 1214 struct shrink_control *sc) 1215 { 1216 struct mem_cgroup *memcg = sc->memcg; 1217 struct lruvec *lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(sc->nid)); 1218 unsigned long nr_backing, nr_stored, nr_freeable, nr_protected; 1219 1220 if (!zswap_shrinker_enabled || !mem_cgroup_zswap_writeback_enabled(memcg)) 1221 return 0; 1222 1223 /* 1224 * The shrinker resumes swap writeback, which will enter block 1225 * and may enter fs. XXX: Harmonize with vmscan.c __GFP_FS 1226 * rules (may_enter_fs()), which apply on a per-folio basis. 1227 */ 1228 if (!gfp_has_io_fs(sc->gfp_mask)) 1229 return 0; 1230 1231 /* 1232 * For memcg, use the cgroup-wide ZSWAP stats since we don't 1233 * have them per-node and thus per-lruvec. Careful if memcg is 1234 * runtime-disabled: we can get sc->memcg == NULL, which is ok 1235 * for the lruvec, but not for memcg_page_state(). 1236 * 1237 * Without memcg, use the zswap pool-wide metrics. 1238 */ 1239 if (!mem_cgroup_disabled()) { 1240 mem_cgroup_flush_stats(memcg); 1241 nr_backing = memcg_page_state(memcg, MEMCG_ZSWAP_B) >> PAGE_SHIFT; 1242 nr_stored = memcg_page_state(memcg, MEMCG_ZSWAPPED); 1243 } else { 1244 nr_backing = zswap_total_pages(); 1245 nr_stored = atomic_read(&zswap_stored_pages); 1246 } 1247 1248 if (!nr_stored) 1249 return 0; 1250 1251 nr_protected = 1252 atomic_long_read(&lruvec->zswap_lruvec_state.nr_zswap_protected); 1253 nr_freeable = list_lru_shrink_count(&zswap_list_lru, sc); 1254 /* 1255 * Subtract the lru size by an estimate of the number of pages 1256 * that should be protected. 1257 */ 1258 nr_freeable = nr_freeable > nr_protected ? nr_freeable - nr_protected : 0; 1259 1260 /* 1261 * Scale the number of freeable pages by the memory saving factor. 1262 * This ensures that the better zswap compresses memory, the fewer 1263 * pages we will evict to swap (as it will otherwise incur IO for 1264 * relatively small memory saving). 1265 * 1266 * The memory saving factor calculated here takes same-filled pages into 1267 * account, but those are not freeable since they almost occupy no 1268 * space. Hence, we may scale nr_freeable down a little bit more than we 1269 * should if we have a lot of same-filled pages. 1270 */ 1271 return mult_frac(nr_freeable, nr_backing, nr_stored); 1272 } 1273 1274 static struct shrinker *zswap_alloc_shrinker(void) 1275 { 1276 struct shrinker *shrinker; 1277 1278 shrinker = 1279 shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE, "mm-zswap"); 1280 if (!shrinker) 1281 return NULL; 1282 1283 shrinker->scan_objects = zswap_shrinker_scan; 1284 shrinker->count_objects = zswap_shrinker_count; 1285 shrinker->batch = 0; 1286 shrinker->seeks = DEFAULT_SEEKS; 1287 return shrinker; 1288 } 1289 1290 static int shrink_memcg(struct mem_cgroup *memcg) 1291 { 1292 int nid, shrunk = 0; 1293 1294 if (!mem_cgroup_zswap_writeback_enabled(memcg)) 1295 return -EINVAL; 1296 1297 /* 1298 * Skip zombies because their LRUs are reparented and we would be 1299 * reclaiming from the parent instead of the dead memcg. 1300 */ 1301 if (memcg && !mem_cgroup_online(memcg)) 1302 return -ENOENT; 1303 1304 for_each_node_state(nid, N_NORMAL_MEMORY) { 1305 unsigned long nr_to_walk = 1; 1306 1307 shrunk += list_lru_walk_one(&zswap_list_lru, nid, memcg, 1308 &shrink_memcg_cb, NULL, &nr_to_walk); 1309 } 1310 return shrunk ? 0 : -EAGAIN; 1311 } 1312 1313 static void shrink_worker(struct work_struct *w) 1314 { 1315 struct mem_cgroup *memcg; 1316 int ret, failures = 0; 1317 unsigned long thr; 1318 1319 /* Reclaim down to the accept threshold */ 1320 thr = zswap_accept_thr_pages(); 1321 1322 /* global reclaim will select cgroup in a round-robin fashion. */ 1323 do { 1324 spin_lock(&zswap_shrink_lock); 1325 zswap_next_shrink = mem_cgroup_iter(NULL, zswap_next_shrink, NULL); 1326 memcg = zswap_next_shrink; 1327 1328 /* 1329 * We need to retry if we have gone through a full round trip, or if we 1330 * got an offline memcg (or else we risk undoing the effect of the 1331 * zswap memcg offlining cleanup callback). This is not catastrophic 1332 * per se, but it will keep the now offlined memcg hostage for a while. 1333 * 1334 * Note that if we got an online memcg, we will keep the extra 1335 * reference in case the original reference obtained by mem_cgroup_iter 1336 * is dropped by the zswap memcg offlining callback, ensuring that the 1337 * memcg is not killed when we are reclaiming. 1338 */ 1339 if (!memcg) { 1340 spin_unlock(&zswap_shrink_lock); 1341 if (++failures == MAX_RECLAIM_RETRIES) 1342 break; 1343 1344 goto resched; 1345 } 1346 1347 if (!mem_cgroup_tryget_online(memcg)) { 1348 /* drop the reference from mem_cgroup_iter() */ 1349 mem_cgroup_iter_break(NULL, memcg); 1350 zswap_next_shrink = NULL; 1351 spin_unlock(&zswap_shrink_lock); 1352 1353 if (++failures == MAX_RECLAIM_RETRIES) 1354 break; 1355 1356 goto resched; 1357 } 1358 spin_unlock(&zswap_shrink_lock); 1359 1360 ret = shrink_memcg(memcg); 1361 /* drop the extra reference */ 1362 mem_cgroup_put(memcg); 1363 1364 if (ret == -EINVAL) 1365 break; 1366 if (ret && ++failures == MAX_RECLAIM_RETRIES) 1367 break; 1368 resched: 1369 cond_resched(); 1370 } while (zswap_total_pages() > thr); 1371 } 1372 1373 /********************************* 1374 * same-filled functions 1375 **********************************/ 1376 static bool zswap_is_folio_same_filled(struct folio *folio, unsigned long *value) 1377 { 1378 unsigned long *page; 1379 unsigned long val; 1380 unsigned int pos, last_pos = PAGE_SIZE / sizeof(*page) - 1; 1381 bool ret = false; 1382 1383 page = kmap_local_folio(folio, 0); 1384 val = page[0]; 1385 1386 if (val != page[last_pos]) 1387 goto out; 1388 1389 for (pos = 1; pos < last_pos; pos++) { 1390 if (val != page[pos]) 1391 goto out; 1392 } 1393 1394 *value = val; 1395 ret = true; 1396 out: 1397 kunmap_local(page); 1398 return ret; 1399 } 1400 1401 static void zswap_fill_page(void *ptr, unsigned long value) 1402 { 1403 unsigned long *page; 1404 1405 page = (unsigned long *)ptr; 1406 memset_l(page, value, PAGE_SIZE / sizeof(unsigned long)); 1407 } 1408 1409 /********************************* 1410 * main API 1411 **********************************/ 1412 bool zswap_store(struct folio *folio) 1413 { 1414 swp_entry_t swp = folio->swap; 1415 pgoff_t offset = swp_offset(swp); 1416 struct xarray *tree = swap_zswap_tree(swp); 1417 struct zswap_entry *entry, *old; 1418 struct obj_cgroup *objcg = NULL; 1419 struct mem_cgroup *memcg = NULL; 1420 unsigned long value; 1421 1422 VM_WARN_ON_ONCE(!folio_test_locked(folio)); 1423 VM_WARN_ON_ONCE(!folio_test_swapcache(folio)); 1424 1425 /* Large folios aren't supported */ 1426 if (folio_test_large(folio)) 1427 return false; 1428 1429 if (!zswap_enabled) 1430 goto check_old; 1431 1432 /* Check cgroup limits */ 1433 objcg = get_obj_cgroup_from_folio(folio); 1434 if (objcg && !obj_cgroup_may_zswap(objcg)) { 1435 memcg = get_mem_cgroup_from_objcg(objcg); 1436 if (shrink_memcg(memcg)) { 1437 mem_cgroup_put(memcg); 1438 goto reject; 1439 } 1440 mem_cgroup_put(memcg); 1441 } 1442 1443 if (zswap_check_limits()) 1444 goto reject; 1445 1446 /* allocate entry */ 1447 entry = zswap_entry_cache_alloc(GFP_KERNEL, folio_nid(folio)); 1448 if (!entry) { 1449 zswap_reject_kmemcache_fail++; 1450 goto reject; 1451 } 1452 1453 if (zswap_is_folio_same_filled(folio, &value)) { 1454 entry->length = 0; 1455 entry->value = value; 1456 atomic_inc(&zswap_same_filled_pages); 1457 goto store_entry; 1458 } 1459 1460 /* if entry is successfully added, it keeps the reference */ 1461 entry->pool = zswap_pool_current_get(); 1462 if (!entry->pool) 1463 goto freepage; 1464 1465 if (objcg) { 1466 memcg = get_mem_cgroup_from_objcg(objcg); 1467 if (memcg_list_lru_alloc(memcg, &zswap_list_lru, GFP_KERNEL)) { 1468 mem_cgroup_put(memcg); 1469 goto put_pool; 1470 } 1471 mem_cgroup_put(memcg); 1472 } 1473 1474 if (!zswap_compress(folio, entry)) 1475 goto put_pool; 1476 1477 store_entry: 1478 entry->swpentry = swp; 1479 entry->objcg = objcg; 1480 1481 old = xa_store(tree, offset, entry, GFP_KERNEL); 1482 if (xa_is_err(old)) { 1483 int err = xa_err(old); 1484 1485 WARN_ONCE(err != -ENOMEM, "unexpected xarray error: %d\n", err); 1486 zswap_reject_alloc_fail++; 1487 goto store_failed; 1488 } 1489 1490 /* 1491 * We may have had an existing entry that became stale when 1492 * the folio was redirtied and now the new version is being 1493 * swapped out. Get rid of the old. 1494 */ 1495 if (old) 1496 zswap_entry_free(old); 1497 1498 if (objcg) { 1499 obj_cgroup_charge_zswap(objcg, entry->length); 1500 count_objcg_event(objcg, ZSWPOUT); 1501 } 1502 1503 /* 1504 * We finish initializing the entry while it's already in xarray. 1505 * This is safe because: 1506 * 1507 * 1. Concurrent stores and invalidations are excluded by folio lock. 1508 * 1509 * 2. Writeback is excluded by the entry not being on the LRU yet. 1510 * The publishing order matters to prevent writeback from seeing 1511 * an incoherent entry. 1512 */ 1513 if (entry->length) { 1514 INIT_LIST_HEAD(&entry->lru); 1515 zswap_lru_add(&zswap_list_lru, entry); 1516 } 1517 1518 /* update stats */ 1519 atomic_inc(&zswap_stored_pages); 1520 count_vm_event(ZSWPOUT); 1521 1522 return true; 1523 1524 store_failed: 1525 if (!entry->length) 1526 atomic_dec(&zswap_same_filled_pages); 1527 else { 1528 zpool_free(zswap_find_zpool(entry), entry->handle); 1529 put_pool: 1530 zswap_pool_put(entry->pool); 1531 } 1532 freepage: 1533 zswap_entry_cache_free(entry); 1534 reject: 1535 obj_cgroup_put(objcg); 1536 if (zswap_pool_reached_full) 1537 queue_work(shrink_wq, &zswap_shrink_work); 1538 check_old: 1539 /* 1540 * If the zswap store fails or zswap is disabled, we must invalidate the 1541 * possibly stale entry which was previously stored at this offset. 1542 * Otherwise, writeback could overwrite the new data in the swapfile. 1543 */ 1544 entry = xa_erase(tree, offset); 1545 if (entry) 1546 zswap_entry_free(entry); 1547 return false; 1548 } 1549 1550 bool zswap_load(struct folio *folio) 1551 { 1552 swp_entry_t swp = folio->swap; 1553 pgoff_t offset = swp_offset(swp); 1554 struct page *page = &folio->page; 1555 bool swapcache = folio_test_swapcache(folio); 1556 struct xarray *tree = swap_zswap_tree(swp); 1557 struct zswap_entry *entry; 1558 u8 *dst; 1559 1560 VM_WARN_ON_ONCE(!folio_test_locked(folio)); 1561 1562 /* 1563 * When reading into the swapcache, invalidate our entry. The 1564 * swapcache can be the authoritative owner of the page and 1565 * its mappings, and the pressure that results from having two 1566 * in-memory copies outweighs any benefits of caching the 1567 * compression work. 1568 * 1569 * (Most swapins go through the swapcache. The notable 1570 * exception is the singleton fault on SWP_SYNCHRONOUS_IO 1571 * files, which reads into a private page and may free it if 1572 * the fault fails. We remain the primary owner of the entry.) 1573 */ 1574 if (swapcache) 1575 entry = xa_erase(tree, offset); 1576 else 1577 entry = xa_load(tree, offset); 1578 1579 if (!entry) 1580 return false; 1581 1582 if (entry->length) 1583 zswap_decompress(entry, page); 1584 else { 1585 dst = kmap_local_page(page); 1586 zswap_fill_page(dst, entry->value); 1587 kunmap_local(dst); 1588 } 1589 1590 count_vm_event(ZSWPIN); 1591 if (entry->objcg) 1592 count_objcg_event(entry->objcg, ZSWPIN); 1593 1594 if (swapcache) { 1595 zswap_entry_free(entry); 1596 folio_mark_dirty(folio); 1597 } 1598 1599 return true; 1600 } 1601 1602 void zswap_invalidate(swp_entry_t swp) 1603 { 1604 pgoff_t offset = swp_offset(swp); 1605 struct xarray *tree = swap_zswap_tree(swp); 1606 struct zswap_entry *entry; 1607 1608 entry = xa_erase(tree, offset); 1609 if (entry) 1610 zswap_entry_free(entry); 1611 } 1612 1613 int zswap_swapon(int type, unsigned long nr_pages) 1614 { 1615 struct xarray *trees, *tree; 1616 unsigned int nr, i; 1617 1618 nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES); 1619 trees = kvcalloc(nr, sizeof(*tree), GFP_KERNEL); 1620 if (!trees) { 1621 pr_err("alloc failed, zswap disabled for swap type %d\n", type); 1622 return -ENOMEM; 1623 } 1624 1625 for (i = 0; i < nr; i++) 1626 xa_init(trees + i); 1627 1628 nr_zswap_trees[type] = nr; 1629 zswap_trees[type] = trees; 1630 return 0; 1631 } 1632 1633 void zswap_swapoff(int type) 1634 { 1635 struct xarray *trees = zswap_trees[type]; 1636 unsigned int i; 1637 1638 if (!trees) 1639 return; 1640 1641 /* try_to_unuse() invalidated all the entries already */ 1642 for (i = 0; i < nr_zswap_trees[type]; i++) 1643 WARN_ON_ONCE(!xa_empty(trees + i)); 1644 1645 kvfree(trees); 1646 nr_zswap_trees[type] = 0; 1647 zswap_trees[type] = NULL; 1648 } 1649 1650 /********************************* 1651 * debugfs functions 1652 **********************************/ 1653 #ifdef CONFIG_DEBUG_FS 1654 #include <linux/debugfs.h> 1655 1656 static struct dentry *zswap_debugfs_root; 1657 1658 static int debugfs_get_total_size(void *data, u64 *val) 1659 { 1660 *val = zswap_total_pages() * PAGE_SIZE; 1661 return 0; 1662 } 1663 DEFINE_DEBUGFS_ATTRIBUTE(total_size_fops, debugfs_get_total_size, NULL, "%llu\n"); 1664 1665 static int zswap_debugfs_init(void) 1666 { 1667 if (!debugfs_initialized()) 1668 return -ENODEV; 1669 1670 zswap_debugfs_root = debugfs_create_dir("zswap", NULL); 1671 1672 debugfs_create_u64("pool_limit_hit", 0444, 1673 zswap_debugfs_root, &zswap_pool_limit_hit); 1674 debugfs_create_u64("reject_reclaim_fail", 0444, 1675 zswap_debugfs_root, &zswap_reject_reclaim_fail); 1676 debugfs_create_u64("reject_alloc_fail", 0444, 1677 zswap_debugfs_root, &zswap_reject_alloc_fail); 1678 debugfs_create_u64("reject_kmemcache_fail", 0444, 1679 zswap_debugfs_root, &zswap_reject_kmemcache_fail); 1680 debugfs_create_u64("reject_compress_fail", 0444, 1681 zswap_debugfs_root, &zswap_reject_compress_fail); 1682 debugfs_create_u64("reject_compress_poor", 0444, 1683 zswap_debugfs_root, &zswap_reject_compress_poor); 1684 debugfs_create_u64("written_back_pages", 0444, 1685 zswap_debugfs_root, &zswap_written_back_pages); 1686 debugfs_create_file("pool_total_size", 0444, 1687 zswap_debugfs_root, NULL, &total_size_fops); 1688 debugfs_create_atomic_t("stored_pages", 0444, 1689 zswap_debugfs_root, &zswap_stored_pages); 1690 debugfs_create_atomic_t("same_filled_pages", 0444, 1691 zswap_debugfs_root, &zswap_same_filled_pages); 1692 1693 return 0; 1694 } 1695 #else 1696 static int zswap_debugfs_init(void) 1697 { 1698 return 0; 1699 } 1700 #endif 1701 1702 /********************************* 1703 * module init and exit 1704 **********************************/ 1705 static int zswap_setup(void) 1706 { 1707 struct zswap_pool *pool; 1708 int ret; 1709 1710 zswap_entry_cache = KMEM_CACHE(zswap_entry, 0); 1711 if (!zswap_entry_cache) { 1712 pr_err("entry cache creation failed\n"); 1713 goto cache_fail; 1714 } 1715 1716 ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE, 1717 "mm/zswap_pool:prepare", 1718 zswap_cpu_comp_prepare, 1719 zswap_cpu_comp_dead); 1720 if (ret) 1721 goto hp_fail; 1722 1723 shrink_wq = alloc_workqueue("zswap-shrink", 1724 WQ_UNBOUND|WQ_MEM_RECLAIM, 1); 1725 if (!shrink_wq) 1726 goto shrink_wq_fail; 1727 1728 zswap_shrinker = zswap_alloc_shrinker(); 1729 if (!zswap_shrinker) 1730 goto shrinker_fail; 1731 if (list_lru_init_memcg(&zswap_list_lru, zswap_shrinker)) 1732 goto lru_fail; 1733 shrinker_register(zswap_shrinker); 1734 1735 INIT_WORK(&zswap_shrink_work, shrink_worker); 1736 1737 pool = __zswap_pool_create_fallback(); 1738 if (pool) { 1739 pr_info("loaded using pool %s/%s\n", pool->tfm_name, 1740 zpool_get_type(pool->zpools[0])); 1741 list_add(&pool->list, &zswap_pools); 1742 zswap_has_pool = true; 1743 } else { 1744 pr_err("pool creation failed\n"); 1745 zswap_enabled = false; 1746 } 1747 1748 if (zswap_debugfs_init()) 1749 pr_warn("debugfs initialization failed\n"); 1750 zswap_init_state = ZSWAP_INIT_SUCCEED; 1751 return 0; 1752 1753 lru_fail: 1754 shrinker_free(zswap_shrinker); 1755 shrinker_fail: 1756 destroy_workqueue(shrink_wq); 1757 shrink_wq_fail: 1758 cpuhp_remove_multi_state(CPUHP_MM_ZSWP_POOL_PREPARE); 1759 hp_fail: 1760 kmem_cache_destroy(zswap_entry_cache); 1761 cache_fail: 1762 /* if built-in, we aren't unloaded on failure; don't allow use */ 1763 zswap_init_state = ZSWAP_INIT_FAILED; 1764 zswap_enabled = false; 1765 return -ENOMEM; 1766 } 1767 1768 static int __init zswap_init(void) 1769 { 1770 if (!zswap_enabled) 1771 return 0; 1772 return zswap_setup(); 1773 } 1774 /* must be late so crypto has time to come up */ 1775 late_initcall(zswap_init); 1776 1777 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>"); 1778 MODULE_DESCRIPTION("Compressed cache for swap pages"); 1779