mm/zswap.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * zswap.c - zswap driver file
   4  *
   5  * zswap is a backend for frontswap 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/frontswap.h>
  24 #include <linux/rbtree.h>
  25 #include <linux/swap.h>
  26 #include <linux/crypto.h>
  27 #include <linux/scatterlist.h>
  28 #include <linux/mempool.h>
  29 #include <linux/zpool.h>
  30 #include <crypto/acompress.h>
  31
  32 #include <linux/mm_types.h>
  33 #include <linux/page-flags.h>
  34 #include <linux/swapops.h>
  35 #include <linux/writeback.h>
  36 #include <linux/pagemap.h>
  37 #include <linux/workqueue.h>
  38
  39 #include "swap.h"
  40
  41 /*********************************
  42 * statistics
  43 **********************************/
  44 /* Total bytes used by the compressed storage */
  45 u64 zswap_pool_total_size;
  46 /* The number of compressed pages currently stored in zswap */
  47 atomic_t zswap_stored_pages = ATOMIC_INIT(0);
  48 /* The number of same-value filled pages currently stored in zswap */
  49 static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
  50
  51 /*
  52  * The statistics below are not protected from concurrent access for
  53  * performance reasons so they may not be a 100% accurate.  However,
  54  * they do provide useful information on roughly how many times a
  55  * certain event is occurring.
  56 */
  57
  58 /* Pool limit was hit (see zswap_max_pool_percent) */
  59 static u64 zswap_pool_limit_hit;
  60 /* Pages written back when pool limit was reached */
  61 static u64 zswap_written_back_pages;
  62 /* Store failed due to a reclaim failure after pool limit was reached */
  63 static u64 zswap_reject_reclaim_fail;
  64 /* Compressed page was too big for the allocator to (optimally) store */
  65 static u64 zswap_reject_compress_poor;
  66 /* Store failed because underlying allocator could not get memory */
  67 static u64 zswap_reject_alloc_fail;
  68 /* Store failed because the entry metadata could not be allocated (rare) */
  69 static u64 zswap_reject_kmemcache_fail;
  70 /* Duplicate store was encountered (rare) */
  71 static u64 zswap_duplicate_entry;
  72
  73 /* Shrinker work queue */
  74 static struct workqueue_struct *shrink_wq;
  75 /* Pool limit was hit, we need to calm down */
  76 static bool zswap_pool_reached_full;
  77
  78 /*********************************
  79 * tunables
  80 **********************************/
  81
  82 #define ZSWAP_PARAM_UNSET ""
  83
  84 /* Enable/disable zswap */
  85 static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);
  86 static int zswap_enabled_param_set(const char *,
  87                                    const struct kernel_param *);
  88 static const struct kernel_param_ops zswap_enabled_param_ops = {
  89         .set =          zswap_enabled_param_set,
  90         .get =          param_get_bool,
  91 };
  92 module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
  93
  94 /* Crypto compressor to use */
  95 static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
  96 static int zswap_compressor_param_set(const char *,
  97                                       const struct kernel_param *);
  98 static const struct kernel_param_ops zswap_compressor_param_ops = {
  99         .set =          zswap_compressor_param_set,
 100         .get =          param_get_charp,
 101         .free =         param_free_charp,
 102 };
 103 module_param_cb(compressor, &zswap_compressor_param_ops,
 104                 &zswap_compressor, 0644);
 105
 106 /* Compressed storage zpool to use */
 107 static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
 108 static int zswap_zpool_param_set(const char *, const struct kernel_param *);
 109 static const struct kernel_param_ops zswap_zpool_param_ops = {
 110         .set =          zswap_zpool_param_set,
 111         .get =          param_get_charp,
 112         .free =         param_free_charp,
 113 };
 114 module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
 115
 116 /* The maximum percentage of memory that the compressed pool can occupy */
 117 static unsigned int zswap_max_pool_percent = 20;
 118 module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
 119
 120 /* The threshold for accepting new pages after the max_pool_percent was hit */
 121 static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */
 122 module_param_named(accept_threshold_percent, zswap_accept_thr_percent,
 123                    uint, 0644);
 124
 125 /*
 126  * Enable/disable handling same-value filled pages (enabled by default).
 127  * If disabled every page is considered non-same-value filled.
 128  */
 129 static bool zswap_same_filled_pages_enabled = true;
 130 module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
 131                    bool, 0644);
 132
 133 /* Enable/disable handling non-same-value filled pages (enabled by default) */
 134 static bool zswap_non_same_filled_pages_enabled = true;
 135 module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled,
 136                    bool, 0644);
 137
 138 /*********************************
 139 * data structures
 140 **********************************/
 141
 142 struct crypto_acomp_ctx {
 143         struct crypto_acomp *acomp;
 144         struct acomp_req *req;
 145         struct crypto_wait wait;
 146         u8 *dstmem;
 147         struct mutex *mutex;
 148 };
 149
 150 struct zswap_pool {
 151         struct zpool *zpool;
 152         struct crypto_acomp_ctx __percpu *acomp_ctx;
 153         struct kref kref;
 154         struct list_head list;
 155         struct work_struct release_work;
 156         struct work_struct shrink_work;
 157         struct hlist_node node;
 158         char tfm_name[CRYPTO_MAX_ALG_NAME];
 159 };
 160
 161 /*
 162  * struct zswap_entry
 163  *
 164  * This structure contains the metadata for tracking a single compressed
 165  * page within zswap.
 166  *
 167  * rbnode - links the entry into red-black tree for the appropriate swap type
 168  * offset - the swap offset for the entry.  Index into the red-black tree.
 169  * refcount - the number of outstanding reference to the entry. This is needed
 170  *            to protect against premature freeing of the entry by code
 171  *            concurrent calls to load, invalidate, and writeback.  The lock
 172  *            for the zswap_tree structure that contains the entry must
 173  *            be held while changing the refcount.  Since the lock must
 174  *            be held, there is no reason to also make refcount atomic.
 175  * length - the length in bytes of the compressed page data.  Needed during
 176  *          decompression. For a same value filled page length is 0.
 177  * pool - the zswap_pool the entry's data is in
 178  * handle - zpool allocation handle that stores the compressed page data
 179  * value - value of the same-value filled pages which have same content
 180  */
 181 struct zswap_entry {
 182         struct rb_node rbnode;
 183         pgoff_t offset;
 184         int refcount;
 185         unsigned int length;
 186         struct zswap_pool *pool;
 187         union {
 188                 unsigned long handle;
 189                 unsigned long value;
 190         };
 191         struct obj_cgroup *objcg;
 192 };
 193
 194 struct zswap_header {
 195         swp_entry_t swpentry;
 196 };
 197
 198 /*
 199  * The tree lock in the zswap_tree struct protects a few things:
 200  * - the rbtree
 201  * - the refcount field of each entry in the tree
 202  */
 203 struct zswap_tree {
 204         struct rb_root rbroot;
 205         spinlock_t lock;
 206 };
 207
 208 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
 209
 210 /* RCU-protected iteration */
 211 static LIST_HEAD(zswap_pools);
 212 /* protects zswap_pools list modification */
 213 static DEFINE_SPINLOCK(zswap_pools_lock);
 214 /* pool counter to provide unique names to zpool */
 215 static atomic_t zswap_pools_count = ATOMIC_INIT(0);
 216
 217 /* used by param callback function */
 218 static bool zswap_init_started;
 219
 220 /* fatal error during init */
 221 static bool zswap_init_failed;
 222
 223 /* init completed, but couldn't create the initial pool */
 224 static bool zswap_has_pool;
 225
 226 /*********************************
 227 * helpers and fwd declarations
 228 **********************************/
 229
 230 #define zswap_pool_debug(msg, p)                                \
 231         pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,         \
 232                  zpool_get_type((p)->zpool))
 233
 234 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
 235 static int zswap_pool_get(struct zswap_pool *pool);
 236 static void zswap_pool_put(struct zswap_pool *pool);
 237
 238 static const struct zpool_ops zswap_zpool_ops = {
 239         .evict = zswap_writeback_entry
 240 };
 241
 242 static bool zswap_is_full(void)
 243 {
 244         return totalram_pages() * zswap_max_pool_percent / 100 <
 245                         DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
 246 }
 247
 248 static bool zswap_can_accept(void)
 249 {
 250         return totalram_pages() * zswap_accept_thr_percent / 100 *
 251                                 zswap_max_pool_percent / 100 >
 252                         DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
 253 }
 254
 255 static void zswap_update_total_size(void)
 256 {
 257         struct zswap_pool *pool;
 258         u64 total = 0;
 259
 260         rcu_read_lock();
 261
 262         list_for_each_entry_rcu(pool, &zswap_pools, list)
 263                 total += zpool_get_total_size(pool->zpool);
 264
 265         rcu_read_unlock();
 266
 267         zswap_pool_total_size = total;
 268 }
 269
 270 /*********************************
 271 * zswap entry functions
 272 **********************************/
 273 static struct kmem_cache *zswap_entry_cache;
 274
 275 static int __init zswap_entry_cache_create(void)
 276 {
 277         zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
 278         return zswap_entry_cache == NULL;
 279 }
 280
 281 static void __init zswap_entry_cache_destroy(void)
 282 {
 283         kmem_cache_destroy(zswap_entry_cache);
 284 }
 285
 286 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
 287 {
 288         struct zswap_entry *entry;
 289         entry = kmem_cache_alloc(zswap_entry_cache, gfp);
 290         if (!entry)
 291                 return NULL;
 292         entry->refcount = 1;
 293         RB_CLEAR_NODE(&entry->rbnode);
 294         return entry;
 295 }
 296
 297 static void zswap_entry_cache_free(struct zswap_entry *entry)
 298 {
 299         kmem_cache_free(zswap_entry_cache, entry);
 300 }
 301
 302 /*********************************
 303 * rbtree functions
 304 **********************************/
 305 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
 306 {
 307         struct rb_node *node = root->rb_node;
 308         struct zswap_entry *entry;
 309
 310         while (node) {
 311                 entry = rb_entry(node, struct zswap_entry, rbnode);
 312                 if (entry->offset > offset)
 313                         node = node->rb_left;
 314                 else if (entry->offset < offset)
 315                         node = node->rb_right;
 316                 else
 317                         return entry;
 318         }
 319         return NULL;
 320 }
 321
 322 /*
 323  * In the case that a entry with the same offset is found, a pointer to
 324  * the existing entry is stored in dupentry and the function returns -EEXIST
 325  */
 326 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
 327                         struct zswap_entry **dupentry)
 328 {
 329         struct rb_node **link = &root->rb_node, *parent = NULL;
 330         struct zswap_entry *myentry;
 331
 332         while (*link) {
 333                 parent = *link;
 334                 myentry = rb_entry(parent, struct zswap_entry, rbnode);
 335                 if (myentry->offset > entry->offset)
 336                         link = &(*link)->rb_left;
 337                 else if (myentry->offset < entry->offset)
 338                         link = &(*link)->rb_right;
 339                 else {
 340                         *dupentry = myentry;
 341                         return -EEXIST;
 342                 }
 343         }
 344         rb_link_node(&entry->rbnode, parent, link);
 345         rb_insert_color(&entry->rbnode, root);
 346         return 0;
 347 }
 348
 349 static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
 350 {
 351         if (!RB_EMPTY_NODE(&entry->rbnode)) {
 352                 rb_erase(&entry->rbnode, root);
 353                 RB_CLEAR_NODE(&entry->rbnode);
 354         }
 355 }
 356
 357 /*
 358  * Carries out the common pattern of freeing and entry's zpool allocation,
 359  * freeing the entry itself, and decrementing the number of stored pages.
 360  */
 361 static void zswap_free_entry(struct zswap_entry *entry)
 362 {
 363         if (entry->objcg) {
 364                 obj_cgroup_uncharge_zswap(entry->objcg, entry->length);
 365                 obj_cgroup_put(entry->objcg);
 366         }
 367         if (!entry->length)
 368                 atomic_dec(&zswap_same_filled_pages);
 369         else {
 370                 zpool_free(entry->pool->zpool, entry->handle);
 371                 zswap_pool_put(entry->pool);
 372         }
 373         zswap_entry_cache_free(entry);
 374         atomic_dec(&zswap_stored_pages);
 375         zswap_update_total_size();
 376 }
 377
 378 /* caller must hold the tree lock */
 379 static void zswap_entry_get(struct zswap_entry *entry)
 380 {
 381         entry->refcount++;
 382 }
 383
 384 /* caller must hold the tree lock
 385 * remove from the tree and free it, if nobody reference the entry
 386 */
 387 static void zswap_entry_put(struct zswap_tree *tree,
 388                         struct zswap_entry *entry)
 389 {
 390         int refcount = --entry->refcount;
 391
 392         BUG_ON(refcount < 0);
 393         if (refcount == 0) {
 394                 zswap_rb_erase(&tree->rbroot, entry);
 395                 zswap_free_entry(entry);
 396         }
 397 }
 398
 399 /* caller must hold the tree lock */
 400 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
 401                                 pgoff_t offset)
 402 {
 403         struct zswap_entry *entry;
 404
 405         entry = zswap_rb_search(root, offset);
 406         if (entry)
 407                 zswap_entry_get(entry);
 408
 409         return entry;
 410 }
 411
 412 /*********************************
 413 * per-cpu code
 414 **********************************/
 415 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
 416 /*
 417  * If users dynamically change the zpool type and compressor at runtime, i.e.
 418  * zswap is running, zswap can have more than one zpool on one cpu, but they
 419  * are sharing dtsmem. So we need this mutex to be per-cpu.
 420  */
 421 static DEFINE_PER_CPU(struct mutex *, zswap_mutex);
 422
 423 static int zswap_dstmem_prepare(unsigned int cpu)
 424 {
 425         struct mutex *mutex;
 426         u8 *dst;
 427
 428         dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
 429         if (!dst)
 430                 return -ENOMEM;
 431
 432         mutex = kmalloc_node(sizeof(*mutex), GFP_KERNEL, cpu_to_node(cpu));
 433         if (!mutex) {
 434                 kfree(dst);
 435                 return -ENOMEM;
 436         }
 437
 438         mutex_init(mutex);
 439         per_cpu(zswap_dstmem, cpu) = dst;
 440         per_cpu(zswap_mutex, cpu) = mutex;
 441         return 0;
 442 }
 443
 444 static int zswap_dstmem_dead(unsigned int cpu)
 445 {
 446         struct mutex *mutex;
 447         u8 *dst;
 448
 449         mutex = per_cpu(zswap_mutex, cpu);
 450         kfree(mutex);
 451         per_cpu(zswap_mutex, cpu) = NULL;
 452
 453         dst = per_cpu(zswap_dstmem, cpu);
 454         kfree(dst);
 455         per_cpu(zswap_dstmem, cpu) = NULL;
 456
 457         return 0;
 458 }
 459
 460 static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 461 {
 462         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 463         struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
 464         struct crypto_acomp *acomp;
 465         struct acomp_req *req;
 466
 467         acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
 468         if (IS_ERR(acomp)) {
 469                 pr_err("could not alloc crypto acomp %s : %ld\n",
 470                                 pool->tfm_name, PTR_ERR(acomp));
 471                 return PTR_ERR(acomp);
 472         }
 473         acomp_ctx->acomp = acomp;
 474
 475         req = acomp_request_alloc(acomp_ctx->acomp);
 476         if (!req) {
 477                 pr_err("could not alloc crypto acomp_request %s\n",
 478                        pool->tfm_name);
 479                 crypto_free_acomp(acomp_ctx->acomp);
 480                 return -ENOMEM;
 481         }
 482         acomp_ctx->req = req;
 483
 484         crypto_init_wait(&acomp_ctx->wait);
 485         /*
 486          * if the backend of acomp is async zip, crypto_req_done() will wakeup
 487          * crypto_wait_req(); if the backend of acomp is scomp, the callback
 488          * won't be called, crypto_wait_req() will return without blocking.
 489          */
 490         acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
 491                                    crypto_req_done, &acomp_ctx->wait);
 492
 493         acomp_ctx->mutex = per_cpu(zswap_mutex, cpu);
 494         acomp_ctx->dstmem = per_cpu(zswap_dstmem, cpu);
 495
 496         return 0;
 497 }
 498
 499 static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 500 {
 501         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 502         struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
 503
 504         if (!IS_ERR_OR_NULL(acomp_ctx)) {
 505                 if (!IS_ERR_OR_NULL(acomp_ctx->req))
 506                         acomp_request_free(acomp_ctx->req);
 507                 if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
 508                         crypto_free_acomp(acomp_ctx->acomp);
 509         }
 510
 511         return 0;
 512 }
 513
 514 /*********************************
 515 * pool functions
 516 **********************************/
 517
 518 static struct zswap_pool *__zswap_pool_current(void)
 519 {
 520         struct zswap_pool *pool;
 521
 522         pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
 523         WARN_ONCE(!pool && zswap_has_pool,
 524                   "%s: no page storage pool!\n", __func__);
 525
 526         return pool;
 527 }
 528
 529 static struct zswap_pool *zswap_pool_current(void)
 530 {
 531         assert_spin_locked(&zswap_pools_lock);
 532
 533         return __zswap_pool_current();
 534 }
 535
 536 static struct zswap_pool *zswap_pool_current_get(void)
 537 {
 538         struct zswap_pool *pool;
 539
 540         rcu_read_lock();
 541
 542         pool = __zswap_pool_current();
 543         if (!zswap_pool_get(pool))
 544                 pool = NULL;
 545
 546         rcu_read_unlock();
 547
 548         return pool;
 549 }
 550
 551 static struct zswap_pool *zswap_pool_last_get(void)
 552 {
 553         struct zswap_pool *pool, *last = NULL;
 554
 555         rcu_read_lock();
 556
 557         list_for_each_entry_rcu(pool, &zswap_pools, list)
 558                 last = pool;
 559         WARN_ONCE(!last && zswap_has_pool,
 560                   "%s: no page storage pool!\n", __func__);
 561         if (!zswap_pool_get(last))
 562                 last = NULL;
 563
 564         rcu_read_unlock();
 565
 566         return last;
 567 }
 568
 569 /* type and compressor must be null-terminated */
 570 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
 571 {
 572         struct zswap_pool *pool;
 573
 574         assert_spin_locked(&zswap_pools_lock);
 575
 576         list_for_each_entry_rcu(pool, &zswap_pools, list) {
 577                 if (strcmp(pool->tfm_name, compressor))
 578                         continue;
 579                 if (strcmp(zpool_get_type(pool->zpool), type))
 580                         continue;
 581                 /* if we can't get it, it's about to be destroyed */
 582                 if (!zswap_pool_get(pool))
 583                         continue;
 584                 return pool;
 585         }
 586
 587         return NULL;
 588 }
 589
 590 static void shrink_worker(struct work_struct *w)
 591 {
 592         struct zswap_pool *pool = container_of(w, typeof(*pool),
 593                                                 shrink_work);
 594
 595         if (zpool_shrink(pool->zpool, 1, NULL))
 596                 zswap_reject_reclaim_fail++;
 597         zswap_pool_put(pool);
 598 }
 599
 600 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
 601 {
 602         struct zswap_pool *pool;
 603         char name[38]; /* 'zswap' + 32 char (max) num + \0 */
 604         gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
 605         int ret;
 606
 607         if (!zswap_has_pool) {
 608                 /* if either are unset, pool initialization failed, and we
 609                  * need both params to be set correctly before trying to
 610                  * create a pool.
 611                  */
 612                 if (!strcmp(type, ZSWAP_PARAM_UNSET))
 613                         return NULL;
 614                 if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
 615                         return NULL;
 616         }
 617
 618         pool = kzalloc(sizeof(*pool), GFP_KERNEL);
 619         if (!pool)
 620                 return NULL;
 621
 622         /* unique name for each pool specifically required by zsmalloc */
 623         snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
 624
 625         pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
 626         if (!pool->zpool) {
 627                 pr_err("%s zpool not available\n", type);
 628                 goto error;
 629         }
 630         pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
 631
 632         strscpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
 633
 634         pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx);
 635         if (!pool->acomp_ctx) {
 636                 pr_err("percpu alloc failed\n");
 637                 goto error;
 638         }
 639
 640         ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
 641                                        &pool->node);
 642         if (ret)
 643                 goto error;
 644         pr_debug("using %s compressor\n", pool->tfm_name);
 645
 646         /* being the current pool takes 1 ref; this func expects the
 647          * caller to always add the new pool as the current pool
 648          */
 649         kref_init(&pool->kref);
 650         INIT_LIST_HEAD(&pool->list);
 651         INIT_WORK(&pool->shrink_work, shrink_worker);
 652
 653         zswap_pool_debug("created", pool);
 654
 655         return pool;
 656
 657 error:
 658         if (pool->acomp_ctx)
 659                 free_percpu(pool->acomp_ctx);
 660         if (pool->zpool)
 661                 zpool_destroy_pool(pool->zpool);
 662         kfree(pool);
 663         return NULL;
 664 }
 665
 666 static __init struct zswap_pool *__zswap_pool_create_fallback(void)
 667 {
 668         bool has_comp, has_zpool;
 669
 670         has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
 671         if (!has_comp && strcmp(zswap_compressor,
 672                                 CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
 673                 pr_err("compressor %s not available, using default %s\n",
 674                        zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
 675                 param_free_charp(&zswap_compressor);
 676                 zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
 677                 has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
 678         }
 679         if (!has_comp) {
 680                 pr_err("default compressor %s not available\n",
 681                        zswap_compressor);
 682                 param_free_charp(&zswap_compressor);
 683                 zswap_compressor = ZSWAP_PARAM_UNSET;
 684         }
 685
 686         has_zpool = zpool_has_pool(zswap_zpool_type);
 687         if (!has_zpool && strcmp(zswap_zpool_type,
 688                                  CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
 689                 pr_err("zpool %s not available, using default %s\n",
 690                        zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
 691                 param_free_charp(&zswap_zpool_type);
 692                 zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
 693                 has_zpool = zpool_has_pool(zswap_zpool_type);
 694         }
 695         if (!has_zpool) {
 696                 pr_err("default zpool %s not available\n",
 697                        zswap_zpool_type);
 698                 param_free_charp(&zswap_zpool_type);
 699                 zswap_zpool_type = ZSWAP_PARAM_UNSET;
 700         }
 701
 702         if (!has_comp || !has_zpool)
 703                 return NULL;
 704
 705         return zswap_pool_create(zswap_zpool_type, zswap_compressor);
 706 }
 707
 708 static void zswap_pool_destroy(struct zswap_pool *pool)
 709 {
 710         zswap_pool_debug("destroying", pool);
 711
 712         cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
 713         free_percpu(pool->acomp_ctx);
 714         zpool_destroy_pool(pool->zpool);
 715         kfree(pool);
 716 }
 717
 718 static int __must_check zswap_pool_get(struct zswap_pool *pool)
 719 {
 720         if (!pool)
 721                 return 0;
 722
 723         return kref_get_unless_zero(&pool->kref);
 724 }
 725
 726 static void __zswap_pool_release(struct work_struct *work)
 727 {
 728         struct zswap_pool *pool = container_of(work, typeof(*pool),
 729                                                 release_work);
 730
 731         synchronize_rcu();
 732
 733         /* nobody should have been able to get a kref... */
 734         WARN_ON(kref_get_unless_zero(&pool->kref));
 735
 736         /* pool is now off zswap_pools list and has no references. */
 737         zswap_pool_destroy(pool);
 738 }
 739
 740 static void __zswap_pool_empty(struct kref *kref)
 741 {
 742         struct zswap_pool *pool;
 743
 744         pool = container_of(kref, typeof(*pool), kref);
 745
 746         spin_lock(&zswap_pools_lock);
 747
 748         WARN_ON(pool == zswap_pool_current());
 749
 750         list_del_rcu(&pool->list);
 751
 752         INIT_WORK(&pool->release_work, __zswap_pool_release);
 753         schedule_work(&pool->release_work);
 754
 755         spin_unlock(&zswap_pools_lock);
 756 }
 757
 758 static void zswap_pool_put(struct zswap_pool *pool)
 759 {
 760         kref_put(&pool->kref, __zswap_pool_empty);
 761 }
 762
 763 /*********************************
 764 * param callbacks
 765 **********************************/
 766
 767 /* val must be a null-terminated string */
 768 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
 769                              char *type, char *compressor)
 770 {
 771         struct zswap_pool *pool, *put_pool = NULL;
 772         char *s = strstrip((char *)val);
 773         int ret;
 774
 775         if (zswap_init_failed) {
 776                 pr_err("can't set param, initialization failed\n");
 777                 return -ENODEV;
 778         }
 779
 780         /* no change required */
 781         if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
 782                 return 0;
 783
 784         /* if this is load-time (pre-init) param setting,
 785          * don't create a pool; that's done during init.
 786          */
 787         if (!zswap_init_started)
 788                 return param_set_charp(s, kp);
 789
 790         if (!type) {
 791                 if (!zpool_has_pool(s)) {
 792                         pr_err("zpool %s not available\n", s);
 793                         return -ENOENT;
 794                 }
 795                 type = s;
 796         } else if (!compressor) {
 797                 if (!crypto_has_acomp(s, 0, 0)) {
 798                         pr_err("compressor %s not available\n", s);
 799                         return -ENOENT;
 800                 }
 801                 compressor = s;
 802         } else {
 803                 WARN_ON(1);
 804                 return -EINVAL;
 805         }
 806
 807         spin_lock(&zswap_pools_lock);
 808
 809         pool = zswap_pool_find_get(type, compressor);
 810         if (pool) {
 811                 zswap_pool_debug("using existing", pool);
 812                 WARN_ON(pool == zswap_pool_current());
 813                 list_del_rcu(&pool->list);
 814         }
 815
 816         spin_unlock(&zswap_pools_lock);
 817
 818         if (!pool)
 819                 pool = zswap_pool_create(type, compressor);
 820
 821         if (pool)
 822                 ret = param_set_charp(s, kp);
 823         else
 824                 ret = -EINVAL;
 825
 826         spin_lock(&zswap_pools_lock);
 827
 828         if (!ret) {
 829                 put_pool = zswap_pool_current();
 830                 list_add_rcu(&pool->list, &zswap_pools);
 831                 zswap_has_pool = true;
 832         } else if (pool) {
 833                 /* add the possibly pre-existing pool to the end of the pools
 834                  * list; if it's new (and empty) then it'll be removed and
 835                  * destroyed by the put after we drop the lock
 836                  */
 837                 list_add_tail_rcu(&pool->list, &zswap_pools);
 838                 put_pool = pool;
 839         }
 840
 841         spin_unlock(&zswap_pools_lock);
 842
 843         if (!zswap_has_pool && !pool) {
 844                 /* if initial pool creation failed, and this pool creation also
 845                  * failed, maybe both compressor and zpool params were bad.
 846                  * Allow changing this param, so pool creation will succeed
 847                  * when the other param is changed. We already verified this
 848                  * param is ok in the zpool_has_pool() or crypto_has_acomp()
 849                  * checks above.
 850                  */
 851                 ret = param_set_charp(s, kp);
 852         }
 853
 854         /* drop the ref from either the old current pool,
 855          * or the new pool we failed to add
 856          */
 857         if (put_pool)
 858                 zswap_pool_put(put_pool);
 859
 860         return ret;
 861 }
 862
 863 static int zswap_compressor_param_set(const char *val,
 864                                       const struct kernel_param *kp)
 865 {
 866         return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
 867 }
 868
 869 static int zswap_zpool_param_set(const char *val,
 870                                  const struct kernel_param *kp)
 871 {
 872         return __zswap_param_set(val, kp, NULL, zswap_compressor);
 873 }
 874
 875 static int zswap_enabled_param_set(const char *val,
 876                                    const struct kernel_param *kp)
 877 {
 878         if (zswap_init_failed) {
 879                 pr_err("can't enable, initialization failed\n");
 880                 return -ENODEV;
 881         }
 882         if (!zswap_has_pool && zswap_init_started) {
 883                 pr_err("can't enable, no pool configured\n");
 884                 return -ENODEV;
 885         }
 886
 887         return param_set_bool(val, kp);
 888 }
 889
 890 /*********************************
 891 * writeback code
 892 **********************************/
 893 /* return enum for zswap_get_swap_cache_page */
 894 enum zswap_get_swap_ret {
 895         ZSWAP_SWAPCACHE_NEW,
 896         ZSWAP_SWAPCACHE_EXIST,
 897         ZSWAP_SWAPCACHE_FAIL,
 898 };
 899
 900 /*
 901  * zswap_get_swap_cache_page
 902  *
 903  * This is an adaption of read_swap_cache_async()
 904  *
 905  * This function tries to find a page with the given swap entry
 906  * in the swapper_space address space (the swap cache).  If the page
 907  * is found, it is returned in retpage.  Otherwise, a page is allocated,
 908  * added to the swap cache, and returned in retpage.
 909  *
 910  * If success, the swap cache page is returned in retpage
 911  * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
 912  * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
 913  *     the new page is added to swapcache and locked
 914  * Returns ZSWAP_SWAPCACHE_FAIL on error
 915  */
 916 static int zswap_get_swap_cache_page(swp_entry_t entry,
 917                                 struct page **retpage)
 918 {
 919         bool page_was_allocated;
 920
 921         *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
 922                         NULL, 0, &page_was_allocated);
 923         if (page_was_allocated)
 924                 return ZSWAP_SWAPCACHE_NEW;
 925         if (!*retpage)
 926                 return ZSWAP_SWAPCACHE_FAIL;
 927         return ZSWAP_SWAPCACHE_EXIST;
 928 }
 929
 930 /*
 931  * Attempts to free an entry by adding a page to the swap cache,
 932  * decompressing the entry data into the page, and issuing a
 933  * bio write to write the page back to the swap device.
 934  *
 935  * This can be thought of as a "resumed writeback" of the page
 936  * to the swap device.  We are basically resuming the same swap
 937  * writeback path that was intercepted with the frontswap_store()
 938  * in the first place.  After the page has been decompressed into
 939  * the swap cache, the compressed version stored by zswap can be
 940  * freed.
 941  */
 942 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 943 {
 944         struct zswap_header *zhdr;
 945         swp_entry_t swpentry;
 946         struct zswap_tree *tree;
 947         pgoff_t offset;
 948         struct zswap_entry *entry;
 949         struct page *page;
 950         struct scatterlist input, output;
 951         struct crypto_acomp_ctx *acomp_ctx;
 952
 953         u8 *src, *tmp = NULL;
 954         unsigned int dlen;
 955         int ret;
 956         struct writeback_control wbc = {
 957                 .sync_mode = WB_SYNC_NONE,
 958         };
 959
 960         if (!zpool_can_sleep_mapped(pool)) {
 961                 tmp = kmalloc(PAGE_SIZE, GFP_KERNEL);
 962                 if (!tmp)
 963                         return -ENOMEM;
 964         }
 965
 966         /* extract swpentry from data */
 967         zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
 968         swpentry = zhdr->swpentry; /* here */
 969         tree = zswap_trees[swp_type(swpentry)];
 970         offset = swp_offset(swpentry);
 971         zpool_unmap_handle(pool, handle);
 972
 973         /* find and ref zswap entry */
 974         spin_lock(&tree->lock);
 975         entry = zswap_entry_find_get(&tree->rbroot, offset);
 976         if (!entry) {
 977                 /* entry was invalidated */
 978                 spin_unlock(&tree->lock);
 979                 kfree(tmp);
 980                 return 0;
 981         }
 982         spin_unlock(&tree->lock);
 983         BUG_ON(offset != entry->offset);
 984
 985         /* try to allocate swap cache page */
 986         switch (zswap_get_swap_cache_page(swpentry, &page)) {
 987         case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
 988                 ret = -ENOMEM;
 989                 goto fail;
 990
 991         case ZSWAP_SWAPCACHE_EXIST:
 992                 /* page is already in the swap cache, ignore for now */
 993                 put_page(page);
 994                 ret = -EEXIST;
 995                 goto fail;
 996
 997         case ZSWAP_SWAPCACHE_NEW: /* page is locked */
 998                 /* decompress */
 999                 acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1000                 dlen = PAGE_SIZE;
1001
1002                 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
1003                 src = (u8 *)zhdr + sizeof(struct zswap_header);
1004                 if (!zpool_can_sleep_mapped(pool)) {
1005                         memcpy(tmp, src, entry->length);
1006                         src = tmp;
1007                         zpool_unmap_handle(pool, handle);
1008                 }
1009
1010                 mutex_lock(acomp_ctx->mutex);
1011                 sg_init_one(&input, src, entry->length);
1012                 sg_init_table(&output, 1);
1013                 sg_set_page(&output, page, PAGE_SIZE, 0);
1014                 acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1015                 ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1016                 dlen = acomp_ctx->req->dlen;
1017                 mutex_unlock(acomp_ctx->mutex);
1018
1019                 if (!zpool_can_sleep_mapped(pool))
1020                         kfree(tmp);
1021                 else
1022                         zpool_unmap_handle(pool, handle);
1023
1024                 BUG_ON(ret);
1025                 BUG_ON(dlen != PAGE_SIZE);
1026
1027                 /* page is up to date */
1028                 SetPageUptodate(page);
1029         }
1030
1031         /* move it to the tail of the inactive list after end_writeback */
1032         SetPageReclaim(page);
1033
1034         /* start writeback */
1035         __swap_writepage(page, &wbc);
1036         put_page(page);
1037         zswap_written_back_pages++;
1038
1039         spin_lock(&tree->lock);
1040         /* drop local reference */
1041         zswap_entry_put(tree, entry);
1042
1043         /*
1044         * There are two possible situations for entry here:
1045         * (1) refcount is 1(normal case),  entry is valid and on the tree
1046         * (2) refcount is 0, entry is freed and not on the tree
1047         *     because invalidate happened during writeback
1048         *  search the tree and free the entry if find entry
1049         */
1050         if (entry == zswap_rb_search(&tree->rbroot, offset))
1051                 zswap_entry_put(tree, entry);
1052         spin_unlock(&tree->lock);
1053
1054         return ret;
1055
1056 fail:
1057         if (!zpool_can_sleep_mapped(pool))
1058                 kfree(tmp);
1059
1060         /*
1061         * if we get here due to ZSWAP_SWAPCACHE_EXIST
1062         * a load may be happening concurrently.
1063         * it is safe and okay to not free the entry.
1064         * if we free the entry in the following put
1065         * it is also okay to return !0
1066         */
1067         spin_lock(&tree->lock);
1068         zswap_entry_put(tree, entry);
1069         spin_unlock(&tree->lock);
1070
1071         return ret;
1072 }
1073
1074 static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
1075 {
1076         unsigned int pos;
1077         unsigned long *page;
1078
1079         page = (unsigned long *)ptr;
1080         for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
1081                 if (page[pos] != page[0])
1082                         return 0;
1083         }
1084         *value = page[0];
1085         return 1;
1086 }
1087
1088 static void zswap_fill_page(void *ptr, unsigned long value)
1089 {
1090         unsigned long *page;
1091
1092         page = (unsigned long *)ptr;
1093         memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
1094 }
1095
1096 /*********************************
1097 * frontswap hooks
1098 **********************************/
1099 /* attempts to compress and store an single page */
1100 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
1101                                 struct page *page)
1102 {
1103         struct zswap_tree *tree = zswap_trees[type];
1104         struct zswap_entry *entry, *dupentry;
1105         struct scatterlist input, output;
1106         struct crypto_acomp_ctx *acomp_ctx;
1107         struct obj_cgroup *objcg = NULL;
1108         struct zswap_pool *pool;
1109         int ret;
1110         unsigned int hlen, dlen = PAGE_SIZE;
1111         unsigned long handle, value;
1112         char *buf;
1113         u8 *src, *dst;
1114         struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
1115         gfp_t gfp;
1116
1117         /* THP isn't supported */
1118         if (PageTransHuge(page)) {
1119                 ret = -EINVAL;
1120                 goto reject;
1121         }
1122
1123         if (!zswap_enabled || !tree) {
1124                 ret = -ENODEV;
1125                 goto reject;
1126         }
1127
1128         objcg = get_obj_cgroup_from_page(page);
1129         if (objcg && !obj_cgroup_may_zswap(objcg))
1130                 goto shrink;
1131
1132         /* reclaim space if needed */
1133         if (zswap_is_full()) {
1134                 zswap_pool_limit_hit++;
1135                 zswap_pool_reached_full = true;
1136                 goto shrink;
1137         }
1138
1139         if (zswap_pool_reached_full) {
1140                if (!zswap_can_accept()) {
1141                         ret = -ENOMEM;
1142                         goto reject;
1143                 } else
1144                         zswap_pool_reached_full = false;
1145         }
1146
1147         /* allocate entry */
1148         entry = zswap_entry_cache_alloc(GFP_KERNEL);
1149         if (!entry) {
1150                 zswap_reject_kmemcache_fail++;
1151                 ret = -ENOMEM;
1152                 goto reject;
1153         }
1154
1155         if (zswap_same_filled_pages_enabled) {
1156                 src = kmap_atomic(page);
1157                 if (zswap_is_page_same_filled(src, &value)) {
1158                         kunmap_atomic(src);
1159                         entry->offset = offset;
1160                         entry->length = 0;
1161                         entry->value = value;
1162                         atomic_inc(&zswap_same_filled_pages);
1163                         goto insert_entry;
1164                 }
1165                 kunmap_atomic(src);
1166         }
1167
1168         if (!zswap_non_same_filled_pages_enabled) {
1169                 ret = -EINVAL;
1170                 goto freepage;
1171         }
1172
1173         /* if entry is successfully added, it keeps the reference */
1174         entry->pool = zswap_pool_current_get();
1175         if (!entry->pool) {
1176                 ret = -EINVAL;
1177                 goto freepage;
1178         }
1179
1180         /* compress */
1181         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1182
1183         mutex_lock(acomp_ctx->mutex);
1184
1185         dst = acomp_ctx->dstmem;
1186         sg_init_table(&input, 1);
1187         sg_set_page(&input, page, PAGE_SIZE, 0);
1188
1189         /* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
1190         sg_init_one(&output, dst, PAGE_SIZE * 2);
1191         acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
1192         /*
1193          * it maybe looks a little bit silly that we send an asynchronous request,
1194          * then wait for its completion synchronously. This makes the process look
1195          * synchronous in fact.
1196          * Theoretically, acomp supports users send multiple acomp requests in one
1197          * acomp instance, then get those requests done simultaneously. but in this
1198          * case, frontswap actually does store and load page by page, there is no
1199          * existing method to send the second page before the first page is done
1200          * in one thread doing frontswap.
1201          * but in different threads running on different cpu, we have different
1202          * acomp instance, so multiple threads can do (de)compression in parallel.
1203          */
1204         ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
1205         dlen = acomp_ctx->req->dlen;
1206
1207         if (ret) {
1208                 ret = -EINVAL;
1209                 goto put_dstmem;
1210         }
1211
1212         /* store */
1213         hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1214         gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1215         if (zpool_malloc_support_movable(entry->pool->zpool))
1216                 gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1217         ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
1218         if (ret == -ENOSPC) {
1219                 zswap_reject_compress_poor++;
1220                 goto put_dstmem;
1221         }
1222         if (ret) {
1223                 zswap_reject_alloc_fail++;
1224                 goto put_dstmem;
1225         }
1226         buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_WO);
1227         memcpy(buf, &zhdr, hlen);
1228         memcpy(buf + hlen, dst, dlen);
1229         zpool_unmap_handle(entry->pool->zpool, handle);
1230         mutex_unlock(acomp_ctx->mutex);
1231
1232         /* populate entry */
1233         entry->offset = offset;
1234         entry->handle = handle;
1235         entry->length = dlen;
1236
1237 insert_entry:
1238         entry->objcg = objcg;
1239         if (objcg) {
1240                 obj_cgroup_charge_zswap(objcg, entry->length);
1241                 /* Account before objcg ref is moved to tree */
1242                 count_objcg_event(objcg, ZSWPOUT);
1243         }
1244
1245         /* map */
1246         spin_lock(&tree->lock);
1247         do {
1248                 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1249                 if (ret == -EEXIST) {
1250                         zswap_duplicate_entry++;
1251                         /* remove from rbtree */
1252                         zswap_rb_erase(&tree->rbroot, dupentry);
1253                         zswap_entry_put(tree, dupentry);
1254                 }
1255         } while (ret == -EEXIST);
1256         spin_unlock(&tree->lock);
1257
1258         /* update stats */
1259         atomic_inc(&zswap_stored_pages);
1260         zswap_update_total_size();
1261         count_vm_event(ZSWPOUT);
1262
1263         return 0;
1264
1265 put_dstmem:
1266         mutex_unlock(acomp_ctx->mutex);
1267         zswap_pool_put(entry->pool);
1268 freepage:
1269         zswap_entry_cache_free(entry);
1270 reject:
1271         if (objcg)
1272                 obj_cgroup_put(objcg);
1273         return ret;
1274
1275 shrink:
1276         pool = zswap_pool_last_get();
1277         if (pool)
1278                 queue_work(shrink_wq, &pool->shrink_work);
1279         ret = -ENOMEM;
1280         goto reject;
1281 }
1282
1283 /*
1284  * returns 0 if the page was successfully decompressed
1285  * return -1 on entry not found or error
1286 */
1287 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1288                                 struct page *page)
1289 {
1290         struct zswap_tree *tree = zswap_trees[type];
1291         struct zswap_entry *entry;
1292         struct scatterlist input, output;
1293         struct crypto_acomp_ctx *acomp_ctx;
1294         u8 *src, *dst, *tmp;
1295         unsigned int dlen;
1296         int ret;
1297
1298         /* find */
1299         spin_lock(&tree->lock);
1300         entry = zswap_entry_find_get(&tree->rbroot, offset);
1301         if (!entry) {
1302                 /* entry was written back */
1303                 spin_unlock(&tree->lock);
1304                 return -1;
1305         }
1306         spin_unlock(&tree->lock);
1307
1308         if (!entry->length) {
1309                 dst = kmap_atomic(page);
1310                 zswap_fill_page(dst, entry->value);
1311                 kunmap_atomic(dst);
1312                 ret = 0;
1313                 goto stats;
1314         }
1315
1316         if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1317                 tmp = kmalloc(entry->length, GFP_KERNEL);
1318                 if (!tmp) {
1319                         ret = -ENOMEM;
1320                         goto freeentry;
1321                 }
1322         }
1323
1324         /* decompress */
1325         dlen = PAGE_SIZE;
1326         src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1327         if (zpool_evictable(entry->pool->zpool))
1328                 src += sizeof(struct zswap_header);
1329
1330         if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1331                 memcpy(tmp, src, entry->length);
1332                 src = tmp;
1333                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1334         }
1335
1336         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1337         mutex_lock(acomp_ctx->mutex);
1338         sg_init_one(&input, src, entry->length);
1339         sg_init_table(&output, 1);
1340         sg_set_page(&output, page, PAGE_SIZE, 0);
1341         acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1342         ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1343         mutex_unlock(acomp_ctx->mutex);
1344
1345         if (zpool_can_sleep_mapped(entry->pool->zpool))
1346                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1347         else
1348                 kfree(tmp);
1349
1350         BUG_ON(ret);
1351 stats:
1352         count_vm_event(ZSWPIN);
1353         if (entry->objcg)
1354                 count_objcg_event(entry->objcg, ZSWPIN);
1355 freeentry:
1356         spin_lock(&tree->lock);
1357         zswap_entry_put(tree, entry);
1358         spin_unlock(&tree->lock);
1359
1360         return ret;
1361 }
1362
1363 /* frees an entry in zswap */
1364 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1365 {
1366         struct zswap_tree *tree = zswap_trees[type];
1367         struct zswap_entry *entry;
1368
1369         /* find */
1370         spin_lock(&tree->lock);
1371         entry = zswap_rb_search(&tree->rbroot, offset);
1372         if (!entry) {
1373                 /* entry was written back */
1374                 spin_unlock(&tree->lock);
1375                 return;
1376         }
1377
1378         /* remove from rbtree */
1379         zswap_rb_erase(&tree->rbroot, entry);
1380
1381         /* drop the initial reference from entry creation */
1382         zswap_entry_put(tree, entry);
1383
1384         spin_unlock(&tree->lock);
1385 }
1386
1387 /* frees all zswap entries for the given swap type */
1388 static void zswap_frontswap_invalidate_area(unsigned type)
1389 {
1390         struct zswap_tree *tree = zswap_trees[type];
1391         struct zswap_entry *entry, *n;
1392
1393         if (!tree)
1394                 return;
1395
1396         /* walk the tree and free everything */
1397         spin_lock(&tree->lock);
1398         rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1399                 zswap_free_entry(entry);
1400         tree->rbroot = RB_ROOT;
1401         spin_unlock(&tree->lock);
1402         kfree(tree);
1403         zswap_trees[type] = NULL;
1404 }
1405
1406 static void zswap_frontswap_init(unsigned type)
1407 {
1408         struct zswap_tree *tree;
1409
1410         tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1411         if (!tree) {
1412                 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1413                 return;
1414         }
1415
1416         tree->rbroot = RB_ROOT;
1417         spin_lock_init(&tree->lock);
1418         zswap_trees[type] = tree;
1419 }
1420
1421 static const struct frontswap_ops zswap_frontswap_ops = {
1422         .store = zswap_frontswap_store,
1423         .load = zswap_frontswap_load,
1424         .invalidate_page = zswap_frontswap_invalidate_page,
1425         .invalidate_area = zswap_frontswap_invalidate_area,
1426         .init = zswap_frontswap_init
1427 };
1428
1429 /*********************************
1430 * debugfs functions
1431 **********************************/
1432 #ifdef CONFIG_DEBUG_FS
1433 #include <linux/debugfs.h>
1434
1435 static struct dentry *zswap_debugfs_root;
1436
1437 static int __init zswap_debugfs_init(void)
1438 {
1439         if (!debugfs_initialized())
1440                 return -ENODEV;
1441
1442         zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1443
1444         debugfs_create_u64("pool_limit_hit", 0444,
1445                            zswap_debugfs_root, &zswap_pool_limit_hit);
1446         debugfs_create_u64("reject_reclaim_fail", 0444,
1447                            zswap_debugfs_root, &zswap_reject_reclaim_fail);
1448         debugfs_create_u64("reject_alloc_fail", 0444,
1449                            zswap_debugfs_root, &zswap_reject_alloc_fail);
1450         debugfs_create_u64("reject_kmemcache_fail", 0444,
1451                            zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1452         debugfs_create_u64("reject_compress_poor", 0444,
1453                            zswap_debugfs_root, &zswap_reject_compress_poor);
1454         debugfs_create_u64("written_back_pages", 0444,
1455                            zswap_debugfs_root, &zswap_written_back_pages);
1456         debugfs_create_u64("duplicate_entry", 0444,
1457                            zswap_debugfs_root, &zswap_duplicate_entry);
1458         debugfs_create_u64("pool_total_size", 0444,
1459                            zswap_debugfs_root, &zswap_pool_total_size);
1460         debugfs_create_atomic_t("stored_pages", 0444,
1461                                 zswap_debugfs_root, &zswap_stored_pages);
1462         debugfs_create_atomic_t("same_filled_pages", 0444,
1463                                 zswap_debugfs_root, &zswap_same_filled_pages);
1464
1465         return 0;
1466 }
1467 #else
1468 static int __init zswap_debugfs_init(void)
1469 {
1470         return 0;
1471 }
1472 #endif
1473
1474 /*********************************
1475 * module init and exit
1476 **********************************/
1477 static int __init init_zswap(void)
1478 {
1479         struct zswap_pool *pool;
1480         int ret;
1481
1482         zswap_init_started = true;
1483
1484         if (zswap_entry_cache_create()) {
1485                 pr_err("entry cache creation failed\n");
1486                 goto cache_fail;
1487         }
1488
1489         ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1490                                 zswap_dstmem_prepare, zswap_dstmem_dead);
1491         if (ret) {
1492                 pr_err("dstmem alloc failed\n");
1493                 goto dstmem_fail;
1494         }
1495
1496         ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1497                                       "mm/zswap_pool:prepare",
1498                                       zswap_cpu_comp_prepare,
1499                                       zswap_cpu_comp_dead);
1500         if (ret)
1501                 goto hp_fail;
1502
1503         pool = __zswap_pool_create_fallback();
1504         if (pool) {
1505                 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1506                         zpool_get_type(pool->zpool));
1507                 list_add(&pool->list, &zswap_pools);
1508                 zswap_has_pool = true;
1509         } else {
1510                 pr_err("pool creation failed\n");
1511                 zswap_enabled = false;
1512         }
1513
1514         shrink_wq = create_workqueue("zswap-shrink");
1515         if (!shrink_wq)
1516                 goto fallback_fail;
1517
1518         ret = frontswap_register_ops(&zswap_frontswap_ops);
1519         if (ret)
1520                 goto destroy_wq;
1521         if (zswap_debugfs_init())
1522                 pr_warn("debugfs initialization failed\n");
1523         return 0;
1524
1525 destroy_wq:
1526         destroy_workqueue(shrink_wq);
1527 fallback_fail:
1528         if (pool)
1529                 zswap_pool_destroy(pool);
1530 hp_fail:
1531         cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1532 dstmem_fail:
1533         zswap_entry_cache_destroy();
1534 cache_fail:
1535         /* if built-in, we aren't unloaded on failure; don't allow use */
1536         zswap_init_failed = true;
1537         zswap_enabled = false;
1538         return -ENOMEM;
1539 }
1540 /* must be late so crypto has time to come up */
1541 late_initcall(init_zswap);
1542
1543 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1544 MODULE_DESCRIPTION("Compressed cache for swap pages");