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_ATOMIC);
 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
 972         /* find and ref zswap entry */
 973         spin_lock(&tree->lock);
 974         entry = zswap_entry_find_get(&tree->rbroot, offset);
 975         if (!entry) {
 976                 /* entry was invalidated */
 977                 spin_unlock(&tree->lock);
 978                 zpool_unmap_handle(pool, handle);
 979                 kfree(tmp);
 980                 return 0;
 981         }
 982         spin_unlock(&tree->lock);
 983         BUG_ON(offset != entry->offset);
 984
 985         src = (u8 *)zhdr + sizeof(struct zswap_header);
 986         if (!zpool_can_sleep_mapped(pool)) {
 987                 memcpy(tmp, src, entry->length);
 988                 src = tmp;
 989                 zpool_unmap_handle(pool, handle);
 990         }
 991
 992         /* try to allocate swap cache page */
 993         switch (zswap_get_swap_cache_page(swpentry, &page)) {
 994         case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
 995                 ret = -ENOMEM;
 996                 goto fail;
 997
 998         case ZSWAP_SWAPCACHE_EXIST:
 999                 /* page is already in the swap cache, ignore for now */
1000                 put_page(page);
1001                 ret = -EEXIST;
1002                 goto fail;
1003
1004         case ZSWAP_SWAPCACHE_NEW: /* page is locked */
1005                 /* decompress */
1006                 acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1007                 dlen = PAGE_SIZE;
1008
1009                 mutex_lock(acomp_ctx->mutex);
1010                 sg_init_one(&input, src, entry->length);
1011                 sg_init_table(&output, 1);
1012                 sg_set_page(&output, page, PAGE_SIZE, 0);
1013                 acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1014                 ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1015                 dlen = acomp_ctx->req->dlen;
1016                 mutex_unlock(acomp_ctx->mutex);
1017
1018                 BUG_ON(ret);
1019                 BUG_ON(dlen != PAGE_SIZE);
1020
1021                 /* page is up to date */
1022                 SetPageUptodate(page);
1023         }
1024
1025         /* move it to the tail of the inactive list after end_writeback */
1026         SetPageReclaim(page);
1027
1028         /* start writeback */
1029         __swap_writepage(page, &wbc);
1030         put_page(page);
1031         zswap_written_back_pages++;
1032
1033         spin_lock(&tree->lock);
1034         /* drop local reference */
1035         zswap_entry_put(tree, entry);
1036
1037         /*
1038         * There are two possible situations for entry here:
1039         * (1) refcount is 1(normal case),  entry is valid and on the tree
1040         * (2) refcount is 0, entry is freed and not on the tree
1041         *     because invalidate happened during writeback
1042         *  search the tree and free the entry if find entry
1043         */
1044         if (entry == zswap_rb_search(&tree->rbroot, offset))
1045                 zswap_entry_put(tree, entry);
1046         spin_unlock(&tree->lock);
1047
1048         goto end;
1049
1050         /*
1051         * if we get here due to ZSWAP_SWAPCACHE_EXIST
1052         * a load may be happening concurrently.
1053         * it is safe and okay to not free the entry.
1054         * if we free the entry in the following put
1055         * it is also okay to return !0
1056         */
1057 fail:
1058         spin_lock(&tree->lock);
1059         zswap_entry_put(tree, entry);
1060         spin_unlock(&tree->lock);
1061
1062 end:
1063         if (zpool_can_sleep_mapped(pool))
1064                 zpool_unmap_handle(pool, handle);
1065         else
1066                 kfree(tmp);
1067
1068         return ret;
1069 }
1070
1071 static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
1072 {
1073         unsigned int pos;
1074         unsigned long *page;
1075
1076         page = (unsigned long *)ptr;
1077         for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
1078                 if (page[pos] != page[0])
1079                         return 0;
1080         }
1081         *value = page[0];
1082         return 1;
1083 }
1084
1085 static void zswap_fill_page(void *ptr, unsigned long value)
1086 {
1087         unsigned long *page;
1088
1089         page = (unsigned long *)ptr;
1090         memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
1091 }
1092
1093 /*********************************
1094 * frontswap hooks
1095 **********************************/
1096 /* attempts to compress and store an single page */
1097 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
1098                                 struct page *page)
1099 {
1100         struct zswap_tree *tree = zswap_trees[type];
1101         struct zswap_entry *entry, *dupentry;
1102         struct scatterlist input, output;
1103         struct crypto_acomp_ctx *acomp_ctx;
1104         struct obj_cgroup *objcg = NULL;
1105         struct zswap_pool *pool;
1106         int ret;
1107         unsigned int hlen, dlen = PAGE_SIZE;
1108         unsigned long handle, value;
1109         char *buf;
1110         u8 *src, *dst;
1111         struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
1112         gfp_t gfp;
1113
1114         /* THP isn't supported */
1115         if (PageTransHuge(page)) {
1116                 ret = -EINVAL;
1117                 goto reject;
1118         }
1119
1120         if (!zswap_enabled || !tree) {
1121                 ret = -ENODEV;
1122                 goto reject;
1123         }
1124
1125         objcg = get_obj_cgroup_from_page(page);
1126         if (objcg && !obj_cgroup_may_zswap(objcg))
1127                 goto shrink;
1128
1129         /* reclaim space if needed */
1130         if (zswap_is_full()) {
1131                 zswap_pool_limit_hit++;
1132                 zswap_pool_reached_full = true;
1133                 goto shrink;
1134         }
1135
1136         if (zswap_pool_reached_full) {
1137                if (!zswap_can_accept()) {
1138                         ret = -ENOMEM;
1139                         goto reject;
1140                 } else
1141                         zswap_pool_reached_full = false;
1142         }
1143
1144         /* allocate entry */
1145         entry = zswap_entry_cache_alloc(GFP_KERNEL);
1146         if (!entry) {
1147                 zswap_reject_kmemcache_fail++;
1148                 ret = -ENOMEM;
1149                 goto reject;
1150         }
1151
1152         if (zswap_same_filled_pages_enabled) {
1153                 src = kmap_atomic(page);
1154                 if (zswap_is_page_same_filled(src, &value)) {
1155                         kunmap_atomic(src);
1156                         entry->offset = offset;
1157                         entry->length = 0;
1158                         entry->value = value;
1159                         atomic_inc(&zswap_same_filled_pages);
1160                         goto insert_entry;
1161                 }
1162                 kunmap_atomic(src);
1163         }
1164
1165         if (!zswap_non_same_filled_pages_enabled) {
1166                 ret = -EINVAL;
1167                 goto freepage;
1168         }
1169
1170         /* if entry is successfully added, it keeps the reference */
1171         entry->pool = zswap_pool_current_get();
1172         if (!entry->pool) {
1173                 ret = -EINVAL;
1174                 goto freepage;
1175         }
1176
1177         /* compress */
1178         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1179
1180         mutex_lock(acomp_ctx->mutex);
1181
1182         dst = acomp_ctx->dstmem;
1183         sg_init_table(&input, 1);
1184         sg_set_page(&input, page, PAGE_SIZE, 0);
1185
1186         /* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
1187         sg_init_one(&output, dst, PAGE_SIZE * 2);
1188         acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
1189         /*
1190          * it maybe looks a little bit silly that we send an asynchronous request,
1191          * then wait for its completion synchronously. This makes the process look
1192          * synchronous in fact.
1193          * Theoretically, acomp supports users send multiple acomp requests in one
1194          * acomp instance, then get those requests done simultaneously. but in this
1195          * case, frontswap actually does store and load page by page, there is no
1196          * existing method to send the second page before the first page is done
1197          * in one thread doing frontswap.
1198          * but in different threads running on different cpu, we have different
1199          * acomp instance, so multiple threads can do (de)compression in parallel.
1200          */
1201         ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
1202         dlen = acomp_ctx->req->dlen;
1203
1204         if (ret) {
1205                 ret = -EINVAL;
1206                 goto put_dstmem;
1207         }
1208
1209         /* store */
1210         hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1211         gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1212         if (zpool_malloc_support_movable(entry->pool->zpool))
1213                 gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1214         ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
1215         if (ret == -ENOSPC) {
1216                 zswap_reject_compress_poor++;
1217                 goto put_dstmem;
1218         }
1219         if (ret) {
1220                 zswap_reject_alloc_fail++;
1221                 goto put_dstmem;
1222         }
1223         buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_WO);
1224         memcpy(buf, &zhdr, hlen);
1225         memcpy(buf + hlen, dst, dlen);
1226         zpool_unmap_handle(entry->pool->zpool, handle);
1227         mutex_unlock(acomp_ctx->mutex);
1228
1229         /* populate entry */
1230         entry->offset = offset;
1231         entry->handle = handle;
1232         entry->length = dlen;
1233
1234 insert_entry:
1235         entry->objcg = objcg;
1236         if (objcg) {
1237                 obj_cgroup_charge_zswap(objcg, entry->length);
1238                 /* Account before objcg ref is moved to tree */
1239                 count_objcg_event(objcg, ZSWPOUT);
1240         }
1241
1242         /* map */
1243         spin_lock(&tree->lock);
1244         do {
1245                 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1246                 if (ret == -EEXIST) {
1247                         zswap_duplicate_entry++;
1248                         /* remove from rbtree */
1249                         zswap_rb_erase(&tree->rbroot, dupentry);
1250                         zswap_entry_put(tree, dupentry);
1251                 }
1252         } while (ret == -EEXIST);
1253         spin_unlock(&tree->lock);
1254
1255         /* update stats */
1256         atomic_inc(&zswap_stored_pages);
1257         zswap_update_total_size();
1258         count_vm_event(ZSWPOUT);
1259
1260         return 0;
1261
1262 put_dstmem:
1263         mutex_unlock(acomp_ctx->mutex);
1264         zswap_pool_put(entry->pool);
1265 freepage:
1266         zswap_entry_cache_free(entry);
1267 reject:
1268         if (objcg)
1269                 obj_cgroup_put(objcg);
1270         return ret;
1271
1272 shrink:
1273         pool = zswap_pool_last_get();
1274         if (pool)
1275                 queue_work(shrink_wq, &pool->shrink_work);
1276         ret = -ENOMEM;
1277         goto reject;
1278 }
1279
1280 /*
1281  * returns 0 if the page was successfully decompressed
1282  * return -1 on entry not found or error
1283 */
1284 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1285                                 struct page *page)
1286 {
1287         struct zswap_tree *tree = zswap_trees[type];
1288         struct zswap_entry *entry;
1289         struct scatterlist input, output;
1290         struct crypto_acomp_ctx *acomp_ctx;
1291         u8 *src, *dst, *tmp;
1292         unsigned int dlen;
1293         int ret;
1294
1295         /* find */
1296         spin_lock(&tree->lock);
1297         entry = zswap_entry_find_get(&tree->rbroot, offset);
1298         if (!entry) {
1299                 /* entry was written back */
1300                 spin_unlock(&tree->lock);
1301                 return -1;
1302         }
1303         spin_unlock(&tree->lock);
1304
1305         if (!entry->length) {
1306                 dst = kmap_atomic(page);
1307                 zswap_fill_page(dst, entry->value);
1308                 kunmap_atomic(dst);
1309                 ret = 0;
1310                 goto stats;
1311         }
1312
1313         if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1314                 tmp = kmalloc(entry->length, GFP_ATOMIC);
1315                 if (!tmp) {
1316                         ret = -ENOMEM;
1317                         goto freeentry;
1318                 }
1319         }
1320
1321         /* decompress */
1322         dlen = PAGE_SIZE;
1323         src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1324         if (zpool_evictable(entry->pool->zpool))
1325                 src += sizeof(struct zswap_header);
1326
1327         if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1328                 memcpy(tmp, src, entry->length);
1329                 src = tmp;
1330                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1331         }
1332
1333         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1334         mutex_lock(acomp_ctx->mutex);
1335         sg_init_one(&input, src, entry->length);
1336         sg_init_table(&output, 1);
1337         sg_set_page(&output, page, PAGE_SIZE, 0);
1338         acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1339         ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1340         mutex_unlock(acomp_ctx->mutex);
1341
1342         if (zpool_can_sleep_mapped(entry->pool->zpool))
1343                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
1344         else
1345                 kfree(tmp);
1346
1347         BUG_ON(ret);
1348 stats:
1349         count_vm_event(ZSWPIN);
1350         if (entry->objcg)
1351                 count_objcg_event(entry->objcg, ZSWPIN);
1352 freeentry:
1353         spin_lock(&tree->lock);
1354         zswap_entry_put(tree, entry);
1355         spin_unlock(&tree->lock);
1356
1357         return ret;
1358 }
1359
1360 /* frees an entry in zswap */
1361 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1362 {
1363         struct zswap_tree *tree = zswap_trees[type];
1364         struct zswap_entry *entry;
1365
1366         /* find */
1367         spin_lock(&tree->lock);
1368         entry = zswap_rb_search(&tree->rbroot, offset);
1369         if (!entry) {
1370                 /* entry was written back */
1371                 spin_unlock(&tree->lock);
1372                 return;
1373         }
1374
1375         /* remove from rbtree */
1376         zswap_rb_erase(&tree->rbroot, entry);
1377
1378         /* drop the initial reference from entry creation */
1379         zswap_entry_put(tree, entry);
1380
1381         spin_unlock(&tree->lock);
1382 }
1383
1384 /* frees all zswap entries for the given swap type */
1385 static void zswap_frontswap_invalidate_area(unsigned type)
1386 {
1387         struct zswap_tree *tree = zswap_trees[type];
1388         struct zswap_entry *entry, *n;
1389
1390         if (!tree)
1391                 return;
1392
1393         /* walk the tree and free everything */
1394         spin_lock(&tree->lock);
1395         rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1396                 zswap_free_entry(entry);
1397         tree->rbroot = RB_ROOT;
1398         spin_unlock(&tree->lock);
1399         kfree(tree);
1400         zswap_trees[type] = NULL;
1401 }
1402
1403 static void zswap_frontswap_init(unsigned type)
1404 {
1405         struct zswap_tree *tree;
1406
1407         tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1408         if (!tree) {
1409                 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1410                 return;
1411         }
1412
1413         tree->rbroot = RB_ROOT;
1414         spin_lock_init(&tree->lock);
1415         zswap_trees[type] = tree;
1416 }
1417
1418 static const struct frontswap_ops zswap_frontswap_ops = {
1419         .store = zswap_frontswap_store,
1420         .load = zswap_frontswap_load,
1421         .invalidate_page = zswap_frontswap_invalidate_page,
1422         .invalidate_area = zswap_frontswap_invalidate_area,
1423         .init = zswap_frontswap_init
1424 };
1425
1426 /*********************************
1427 * debugfs functions
1428 **********************************/
1429 #ifdef CONFIG_DEBUG_FS
1430 #include <linux/debugfs.h>
1431
1432 static struct dentry *zswap_debugfs_root;
1433
1434 static int __init zswap_debugfs_init(void)
1435 {
1436         if (!debugfs_initialized())
1437                 return -ENODEV;
1438
1439         zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1440
1441         debugfs_create_u64("pool_limit_hit", 0444,
1442                            zswap_debugfs_root, &zswap_pool_limit_hit);
1443         debugfs_create_u64("reject_reclaim_fail", 0444,
1444                            zswap_debugfs_root, &zswap_reject_reclaim_fail);
1445         debugfs_create_u64("reject_alloc_fail", 0444,
1446                            zswap_debugfs_root, &zswap_reject_alloc_fail);
1447         debugfs_create_u64("reject_kmemcache_fail", 0444,
1448                            zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1449         debugfs_create_u64("reject_compress_poor", 0444,
1450                            zswap_debugfs_root, &zswap_reject_compress_poor);
1451         debugfs_create_u64("written_back_pages", 0444,
1452                            zswap_debugfs_root, &zswap_written_back_pages);
1453         debugfs_create_u64("duplicate_entry", 0444,
1454                            zswap_debugfs_root, &zswap_duplicate_entry);
1455         debugfs_create_u64("pool_total_size", 0444,
1456                            zswap_debugfs_root, &zswap_pool_total_size);
1457         debugfs_create_atomic_t("stored_pages", 0444,
1458                                 zswap_debugfs_root, &zswap_stored_pages);
1459         debugfs_create_atomic_t("same_filled_pages", 0444,
1460                                 zswap_debugfs_root, &zswap_same_filled_pages);
1461
1462         return 0;
1463 }
1464 #else
1465 static int __init zswap_debugfs_init(void)
1466 {
1467         return 0;
1468 }
1469 #endif
1470
1471 /*********************************
1472 * module init and exit
1473 **********************************/
1474 static int __init init_zswap(void)
1475 {
1476         struct zswap_pool *pool;
1477         int ret;
1478
1479         zswap_init_started = true;
1480
1481         if (zswap_entry_cache_create()) {
1482                 pr_err("entry cache creation failed\n");
1483                 goto cache_fail;
1484         }
1485
1486         ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1487                                 zswap_dstmem_prepare, zswap_dstmem_dead);
1488         if (ret) {
1489                 pr_err("dstmem alloc failed\n");
1490                 goto dstmem_fail;
1491         }
1492
1493         ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1494                                       "mm/zswap_pool:prepare",
1495                                       zswap_cpu_comp_prepare,
1496                                       zswap_cpu_comp_dead);
1497         if (ret)
1498                 goto hp_fail;
1499
1500         pool = __zswap_pool_create_fallback();
1501         if (pool) {
1502                 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1503                         zpool_get_type(pool->zpool));
1504                 list_add(&pool->list, &zswap_pools);
1505                 zswap_has_pool = true;
1506         } else {
1507                 pr_err("pool creation failed\n");
1508                 zswap_enabled = false;
1509         }
1510
1511         shrink_wq = create_workqueue("zswap-shrink");
1512         if (!shrink_wq)
1513                 goto fallback_fail;
1514
1515         ret = frontswap_register_ops(&zswap_frontswap_ops);
1516         if (ret)
1517                 goto destroy_wq;
1518         if (zswap_debugfs_init())
1519                 pr_warn("debugfs initialization failed\n");
1520         return 0;
1521
1522 destroy_wq:
1523         destroy_workqueue(shrink_wq);
1524 fallback_fail:
1525         if (pool)
1526                 zswap_pool_destroy(pool);
1527 hp_fail:
1528         cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1529 dstmem_fail:
1530         zswap_entry_cache_destroy();
1531 cache_fail:
1532         /* if built-in, we aren't unloaded on failure; don't allow use */
1533         zswap_init_failed = true;
1534         zswap_enabled = false;
1535         return -ENOMEM;
1536 }
1537 /* must be late so crypto has time to come up */
1538 late_initcall(init_zswap);
1539
1540 MODULE_LICENSE("GPL");
1541 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1542 MODULE_DESCRIPTION("Compressed cache for swap pages");