mm/zswap.c

   1 /*
   2  * zswap.c - zswap driver file
   3  *
   4  * zswap is a backend for frontswap that takes pages that are in the process
   5  * of being swapped out and attempts to compress and store them in a
   6  * RAM-based memory pool.  This can result in a significant I/O reduction on
   7  * the swap device and, in the case where decompressing from RAM is faster
   8  * than reading from the swap device, can also improve workload performance.
   9  *
  10  * Copyright (C) 2012  Seth Jennings <sjenning@linux.vnet.ibm.com>
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License
  14  * as published by the Free Software Foundation; either version 2
  15  * of the License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21 */
  22
  23 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  24
  25 #include <linux/module.h>
  26 #include <linux/cpu.h>
  27 #include <linux/highmem.h>
  28 #include <linux/slab.h>
  29 #include <linux/spinlock.h>
  30 #include <linux/types.h>
  31 #include <linux/atomic.h>
  32 #include <linux/frontswap.h>
  33 #include <linux/rbtree.h>
  34 #include <linux/swap.h>
  35 #include <linux/crypto.h>
  36 #include <linux/mempool.h>
  37 #include <linux/zpool.h>
  38
  39 #include <linux/mm_types.h>
  40 #include <linux/page-flags.h>
  41 #include <linux/swapops.h>
  42 #include <linux/writeback.h>
  43 #include <linux/pagemap.h>
  44
  45 /*********************************
  46 * statistics
  47 **********************************/
  48 /* Total bytes used by the compressed storage */
  49 static u64 zswap_pool_total_size;
  50 /* The number of compressed pages currently stored in zswap */
  51 static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
  52 /* The number of same-value filled pages currently stored in zswap */
  53 static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
  54
  55 /*
  56  * The statistics below are not protected from concurrent access for
  57  * performance reasons so they may not be a 100% accurate.  However,
  58  * they do provide useful information on roughly how many times a
  59  * certain event is occurring.
  60 */
  61
  62 /* Pool limit was hit (see zswap_max_pool_percent) */
  63 static u64 zswap_pool_limit_hit;
  64 /* Pages written back when pool limit was reached */
  65 static u64 zswap_written_back_pages;
  66 /* Store failed due to a reclaim failure after pool limit was reached */
  67 static u64 zswap_reject_reclaim_fail;
  68 /* Compressed page was too big for the allocator to (optimally) store */
  69 static u64 zswap_reject_compress_poor;
  70 /* Store failed because underlying allocator could not get memory */
  71 static u64 zswap_reject_alloc_fail;
  72 /* Store failed because the entry metadata could not be allocated (rare) */
  73 static u64 zswap_reject_kmemcache_fail;
  74 /* Duplicate store was encountered (rare) */
  75 static u64 zswap_duplicate_entry;
  76
  77 /*********************************
  78 * tunables
  79 **********************************/
  80
  81 #define ZSWAP_PARAM_UNSET ""
  82
  83 /* Enable/disable zswap (disabled by default) */
  84 static bool zswap_enabled;
  85 static int zswap_enabled_param_set(const char *,
  86                                    const struct kernel_param *);
  87 static struct kernel_param_ops zswap_enabled_param_ops = {
  88         .set =          zswap_enabled_param_set,
  89         .get =          param_get_bool,
  90 };
  91 module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
  92
  93 /* Crypto compressor to use */
  94 #define ZSWAP_COMPRESSOR_DEFAULT "lzo"
  95 static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
  96 static int zswap_compressor_param_set(const char *,
  97                                       const struct kernel_param *);
  98 static 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 #define ZSWAP_ZPOOL_DEFAULT "zbud"
 108 static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
 109 static int zswap_zpool_param_set(const char *, const struct kernel_param *);
 110 static struct kernel_param_ops zswap_zpool_param_ops = {
 111         .set =          zswap_zpool_param_set,
 112         .get =          param_get_charp,
 113         .free =         param_free_charp,
 114 };
 115 module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
 116
 117 /* The maximum percentage of memory that the compressed pool can occupy */
 118 static unsigned int zswap_max_pool_percent = 20;
 119 module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
 120
 121 /* Enable/disable handling same-value filled pages (enabled by default) */
 122 static bool zswap_same_filled_pages_enabled = true;
 123 module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
 124                    bool, 0644);
 125
 126 /*********************************
 127 * data structures
 128 **********************************/
 129
 130 struct zswap_pool {
 131         struct zpool *zpool;
 132         struct crypto_comp * __percpu *tfm;
 133         struct kref kref;
 134         struct list_head list;
 135         struct work_struct work;
 136         struct hlist_node node;
 137         char tfm_name[CRYPTO_MAX_ALG_NAME];
 138 };
 139
 140 /*
 141  * struct zswap_entry
 142  *
 143  * This structure contains the metadata for tracking a single compressed
 144  * page within zswap.
 145  *
 146  * rbnode - links the entry into red-black tree for the appropriate swap type
 147  * offset - the swap offset for the entry.  Index into the red-black tree.
 148  * refcount - the number of outstanding reference to the entry. This is needed
 149  *            to protect against premature freeing of the entry by code
 150  *            concurrent calls to load, invalidate, and writeback.  The lock
 151  *            for the zswap_tree structure that contains the entry must
 152  *            be held while changing the refcount.  Since the lock must
 153  *            be held, there is no reason to also make refcount atomic.
 154  * length - the length in bytes of the compressed page data.  Needed during
 155  *          decompression. For a same value filled page length is 0.
 156  * pool - the zswap_pool the entry's data is in
 157  * handle - zpool allocation handle that stores the compressed page data
 158  * value - value of the same-value filled pages which have same content
 159  */
 160 struct zswap_entry {
 161         struct rb_node rbnode;
 162         pgoff_t offset;
 163         int refcount;
 164         unsigned int length;
 165         struct zswap_pool *pool;
 166         union {
 167                 unsigned long handle;
 168                 unsigned long value;
 169         };
 170 };
 171
 172 struct zswap_header {
 173         swp_entry_t swpentry;
 174 };
 175
 176 /*
 177  * The tree lock in the zswap_tree struct protects a few things:
 178  * - the rbtree
 179  * - the refcount field of each entry in the tree
 180  */
 181 struct zswap_tree {
 182         struct rb_root rbroot;
 183         spinlock_t lock;
 184 };
 185
 186 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
 187
 188 /* RCU-protected iteration */
 189 static LIST_HEAD(zswap_pools);
 190 /* protects zswap_pools list modification */
 191 static DEFINE_SPINLOCK(zswap_pools_lock);
 192 /* pool counter to provide unique names to zpool */
 193 static atomic_t zswap_pools_count = ATOMIC_INIT(0);
 194
 195 /* used by param callback function */
 196 static bool zswap_init_started;
 197
 198 /* fatal error during init */
 199 static bool zswap_init_failed;
 200
 201 /* init completed, but couldn't create the initial pool */
 202 static bool zswap_has_pool;
 203
 204 /*********************************
 205 * helpers and fwd declarations
 206 **********************************/
 207
 208 #define zswap_pool_debug(msg, p)                                \
 209         pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,         \
 210                  zpool_get_type((p)->zpool))
 211
 212 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
 213 static int zswap_pool_get(struct zswap_pool *pool);
 214 static void zswap_pool_put(struct zswap_pool *pool);
 215
 216 static const struct zpool_ops zswap_zpool_ops = {
 217         .evict = zswap_writeback_entry
 218 };
 219
 220 static bool zswap_is_full(void)
 221 {
 222         return totalram_pages * zswap_max_pool_percent / 100 <
 223                 DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
 224 }
 225
 226 static void zswap_update_total_size(void)
 227 {
 228         struct zswap_pool *pool;
 229         u64 total = 0;
 230
 231         rcu_read_lock();
 232
 233         list_for_each_entry_rcu(pool, &zswap_pools, list)
 234                 total += zpool_get_total_size(pool->zpool);
 235
 236         rcu_read_unlock();
 237
 238         zswap_pool_total_size = total;
 239 }
 240
 241 /*********************************
 242 * zswap entry functions
 243 **********************************/
 244 static struct kmem_cache *zswap_entry_cache;
 245
 246 static int __init zswap_entry_cache_create(void)
 247 {
 248         zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
 249         return zswap_entry_cache == NULL;
 250 }
 251
 252 static void __init zswap_entry_cache_destroy(void)
 253 {
 254         kmem_cache_destroy(zswap_entry_cache);
 255 }
 256
 257 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
 258 {
 259         struct zswap_entry *entry;
 260         entry = kmem_cache_alloc(zswap_entry_cache, gfp);
 261         if (!entry)
 262                 return NULL;
 263         entry->refcount = 1;
 264         RB_CLEAR_NODE(&entry->rbnode);
 265         return entry;
 266 }
 267
 268 static void zswap_entry_cache_free(struct zswap_entry *entry)
 269 {
 270         kmem_cache_free(zswap_entry_cache, entry);
 271 }
 272
 273 /*********************************
 274 * rbtree functions
 275 **********************************/
 276 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
 277 {
 278         struct rb_node *node = root->rb_node;
 279         struct zswap_entry *entry;
 280
 281         while (node) {
 282                 entry = rb_entry(node, struct zswap_entry, rbnode);
 283                 if (entry->offset > offset)
 284                         node = node->rb_left;
 285                 else if (entry->offset < offset)
 286                         node = node->rb_right;
 287                 else
 288                         return entry;
 289         }
 290         return NULL;
 291 }
 292
 293 /*
 294  * In the case that a entry with the same offset is found, a pointer to
 295  * the existing entry is stored in dupentry and the function returns -EEXIST
 296  */
 297 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
 298                         struct zswap_entry **dupentry)
 299 {
 300         struct rb_node **link = &root->rb_node, *parent = NULL;
 301         struct zswap_entry *myentry;
 302
 303         while (*link) {
 304                 parent = *link;
 305                 myentry = rb_entry(parent, struct zswap_entry, rbnode);
 306                 if (myentry->offset > entry->offset)
 307                         link = &(*link)->rb_left;
 308                 else if (myentry->offset < entry->offset)
 309                         link = &(*link)->rb_right;
 310                 else {
 311                         *dupentry = myentry;
 312                         return -EEXIST;
 313                 }
 314         }
 315         rb_link_node(&entry->rbnode, parent, link);
 316         rb_insert_color(&entry->rbnode, root);
 317         return 0;
 318 }
 319
 320 static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
 321 {
 322         if (!RB_EMPTY_NODE(&entry->rbnode)) {
 323                 rb_erase(&entry->rbnode, root);
 324                 RB_CLEAR_NODE(&entry->rbnode);
 325         }
 326 }
 327
 328 /*
 329  * Carries out the common pattern of freeing and entry's zpool allocation,
 330  * freeing the entry itself, and decrementing the number of stored pages.
 331  */
 332 static void zswap_free_entry(struct zswap_entry *entry)
 333 {
 334         if (!entry->length)
 335                 atomic_dec(&zswap_same_filled_pages);
 336         else {
 337                 zpool_free(entry->pool->zpool, entry->handle);
 338                 zswap_pool_put(entry->pool);
 339         }
 340         zswap_entry_cache_free(entry);
 341         atomic_dec(&zswap_stored_pages);
 342         zswap_update_total_size();
 343 }
 344
 345 /* caller must hold the tree lock */
 346 static void zswap_entry_get(struct zswap_entry *entry)
 347 {
 348         entry->refcount++;
 349 }
 350
 351 /* caller must hold the tree lock
 352 * remove from the tree and free it, if nobody reference the entry
 353 */
 354 static void zswap_entry_put(struct zswap_tree *tree,
 355                         struct zswap_entry *entry)
 356 {
 357         int refcount = --entry->refcount;
 358
 359         BUG_ON(refcount < 0);
 360         if (refcount == 0) {
 361                 zswap_rb_erase(&tree->rbroot, entry);
 362                 zswap_free_entry(entry);
 363         }
 364 }
 365
 366 /* caller must hold the tree lock */
 367 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
 368                                 pgoff_t offset)
 369 {
 370         struct zswap_entry *entry;
 371
 372         entry = zswap_rb_search(root, offset);
 373         if (entry)
 374                 zswap_entry_get(entry);
 375
 376         return entry;
 377 }
 378
 379 /*********************************
 380 * per-cpu code
 381 **********************************/
 382 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
 383
 384 static int zswap_dstmem_prepare(unsigned int cpu)
 385 {
 386         u8 *dst;
 387
 388         dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
 389         if (!dst)
 390                 return -ENOMEM;
 391
 392         per_cpu(zswap_dstmem, cpu) = dst;
 393         return 0;
 394 }
 395
 396 static int zswap_dstmem_dead(unsigned int cpu)
 397 {
 398         u8 *dst;
 399
 400         dst = per_cpu(zswap_dstmem, cpu);
 401         kfree(dst);
 402         per_cpu(zswap_dstmem, cpu) = NULL;
 403
 404         return 0;
 405 }
 406
 407 static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 408 {
 409         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 410         struct crypto_comp *tfm;
 411
 412         if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
 413                 return 0;
 414
 415         tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
 416         if (IS_ERR_OR_NULL(tfm)) {
 417                 pr_err("could not alloc crypto comp %s : %ld\n",
 418                        pool->tfm_name, PTR_ERR(tfm));
 419                 return -ENOMEM;
 420         }
 421         *per_cpu_ptr(pool->tfm, cpu) = tfm;
 422         return 0;
 423 }
 424
 425 static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 426 {
 427         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 428         struct crypto_comp *tfm;
 429
 430         tfm = *per_cpu_ptr(pool->tfm, cpu);
 431         if (!IS_ERR_OR_NULL(tfm))
 432                 crypto_free_comp(tfm);
 433         *per_cpu_ptr(pool->tfm, cpu) = NULL;
 434         return 0;
 435 }
 436
 437 /*********************************
 438 * pool functions
 439 **********************************/
 440
 441 static struct zswap_pool *__zswap_pool_current(void)
 442 {
 443         struct zswap_pool *pool;
 444
 445         pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
 446         WARN_ONCE(!pool && zswap_has_pool,
 447                   "%s: no page storage pool!\n", __func__);
 448
 449         return pool;
 450 }
 451
 452 static struct zswap_pool *zswap_pool_current(void)
 453 {
 454         assert_spin_locked(&zswap_pools_lock);
 455
 456         return __zswap_pool_current();
 457 }
 458
 459 static struct zswap_pool *zswap_pool_current_get(void)
 460 {
 461         struct zswap_pool *pool;
 462
 463         rcu_read_lock();
 464
 465         pool = __zswap_pool_current();
 466         if (!zswap_pool_get(pool))
 467                 pool = NULL;
 468
 469         rcu_read_unlock();
 470
 471         return pool;
 472 }
 473
 474 static struct zswap_pool *zswap_pool_last_get(void)
 475 {
 476         struct zswap_pool *pool, *last = NULL;
 477
 478         rcu_read_lock();
 479
 480         list_for_each_entry_rcu(pool, &zswap_pools, list)
 481                 last = pool;
 482         WARN_ONCE(!last && zswap_has_pool,
 483                   "%s: no page storage pool!\n", __func__);
 484         if (!zswap_pool_get(last))
 485                 last = NULL;
 486
 487         rcu_read_unlock();
 488
 489         return last;
 490 }
 491
 492 /* type and compressor must be null-terminated */
 493 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
 494 {
 495         struct zswap_pool *pool;
 496
 497         assert_spin_locked(&zswap_pools_lock);
 498
 499         list_for_each_entry_rcu(pool, &zswap_pools, list) {
 500                 if (strcmp(pool->tfm_name, compressor))
 501                         continue;
 502                 if (strcmp(zpool_get_type(pool->zpool), type))
 503                         continue;
 504                 /* if we can't get it, it's about to be destroyed */
 505                 if (!zswap_pool_get(pool))
 506                         continue;
 507                 return pool;
 508         }
 509
 510         return NULL;
 511 }
 512
 513 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
 514 {
 515         struct zswap_pool *pool;
 516         char name[38]; /* 'zswap' + 32 char (max) num + \0 */
 517         gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
 518         int ret;
 519
 520         if (!zswap_has_pool) {
 521                 /* if either are unset, pool initialization failed, and we
 522                  * need both params to be set correctly before trying to
 523                  * create a pool.
 524                  */
 525                 if (!strcmp(type, ZSWAP_PARAM_UNSET))
 526                         return NULL;
 527                 if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
 528                         return NULL;
 529         }
 530
 531         pool = kzalloc(sizeof(*pool), GFP_KERNEL);
 532         if (!pool)
 533                 return NULL;
 534
 535         /* unique name for each pool specifically required by zsmalloc */
 536         snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
 537
 538         pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
 539         if (!pool->zpool) {
 540                 pr_err("%s zpool not available\n", type);
 541                 goto error;
 542         }
 543         pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
 544
 545         strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
 546         pool->tfm = alloc_percpu(struct crypto_comp *);
 547         if (!pool->tfm) {
 548                 pr_err("percpu alloc failed\n");
 549                 goto error;
 550         }
 551
 552         ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
 553                                        &pool->node);
 554         if (ret)
 555                 goto error;
 556         pr_debug("using %s compressor\n", pool->tfm_name);
 557
 558         /* being the current pool takes 1 ref; this func expects the
 559          * caller to always add the new pool as the current pool
 560          */
 561         kref_init(&pool->kref);
 562         INIT_LIST_HEAD(&pool->list);
 563
 564         zswap_pool_debug("created", pool);
 565
 566         return pool;
 567
 568 error:
 569         free_percpu(pool->tfm);
 570         if (pool->zpool)
 571                 zpool_destroy_pool(pool->zpool);
 572         kfree(pool);
 573         return NULL;
 574 }
 575
 576 static __init struct zswap_pool *__zswap_pool_create_fallback(void)
 577 {
 578         bool has_comp, has_zpool;
 579
 580         has_comp = crypto_has_comp(zswap_compressor, 0, 0);
 581         if (!has_comp && strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
 582                 pr_err("compressor %s not available, using default %s\n",
 583                        zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
 584                 param_free_charp(&zswap_compressor);
 585                 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
 586                 has_comp = crypto_has_comp(zswap_compressor, 0, 0);
 587         }
 588         if (!has_comp) {
 589                 pr_err("default compressor %s not available\n",
 590                        zswap_compressor);
 591                 param_free_charp(&zswap_compressor);
 592                 zswap_compressor = ZSWAP_PARAM_UNSET;
 593         }
 594
 595         has_zpool = zpool_has_pool(zswap_zpool_type);
 596         if (!has_zpool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
 597                 pr_err("zpool %s not available, using default %s\n",
 598                        zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
 599                 param_free_charp(&zswap_zpool_type);
 600                 zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
 601                 has_zpool = zpool_has_pool(zswap_zpool_type);
 602         }
 603         if (!has_zpool) {
 604                 pr_err("default zpool %s not available\n",
 605                        zswap_zpool_type);
 606                 param_free_charp(&zswap_zpool_type);
 607                 zswap_zpool_type = ZSWAP_PARAM_UNSET;
 608         }
 609
 610         if (!has_comp || !has_zpool)
 611                 return NULL;
 612
 613         return zswap_pool_create(zswap_zpool_type, zswap_compressor);
 614 }
 615
 616 static void zswap_pool_destroy(struct zswap_pool *pool)
 617 {
 618         zswap_pool_debug("destroying", pool);
 619
 620         cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
 621         free_percpu(pool->tfm);
 622         zpool_destroy_pool(pool->zpool);
 623         kfree(pool);
 624 }
 625
 626 static int __must_check zswap_pool_get(struct zswap_pool *pool)
 627 {
 628         if (!pool)
 629                 return 0;
 630
 631         return kref_get_unless_zero(&pool->kref);
 632 }
 633
 634 static void __zswap_pool_release(struct work_struct *work)
 635 {
 636         struct zswap_pool *pool = container_of(work, typeof(*pool), work);
 637
 638         synchronize_rcu();
 639
 640         /* nobody should have been able to get a kref... */
 641         WARN_ON(kref_get_unless_zero(&pool->kref));
 642
 643         /* pool is now off zswap_pools list and has no references. */
 644         zswap_pool_destroy(pool);
 645 }
 646
 647 static void __zswap_pool_empty(struct kref *kref)
 648 {
 649         struct zswap_pool *pool;
 650
 651         pool = container_of(kref, typeof(*pool), kref);
 652
 653         spin_lock(&zswap_pools_lock);
 654
 655         WARN_ON(pool == zswap_pool_current());
 656
 657         list_del_rcu(&pool->list);
 658
 659         INIT_WORK(&pool->work, __zswap_pool_release);
 660         schedule_work(&pool->work);
 661
 662         spin_unlock(&zswap_pools_lock);
 663 }
 664
 665 static void zswap_pool_put(struct zswap_pool *pool)
 666 {
 667         kref_put(&pool->kref, __zswap_pool_empty);
 668 }
 669
 670 /*********************************
 671 * param callbacks
 672 **********************************/
 673
 674 /* val must be a null-terminated string */
 675 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
 676                              char *type, char *compressor)
 677 {
 678         struct zswap_pool *pool, *put_pool = NULL;
 679         char *s = strstrip((char *)val);
 680         int ret;
 681
 682         if (zswap_init_failed) {
 683                 pr_err("can't set param, initialization failed\n");
 684                 return -ENODEV;
 685         }
 686
 687         /* no change required */
 688         if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
 689                 return 0;
 690
 691         /* if this is load-time (pre-init) param setting,
 692          * don't create a pool; that's done during init.
 693          */
 694         if (!zswap_init_started)
 695                 return param_set_charp(s, kp);
 696
 697         if (!type) {
 698                 if (!zpool_has_pool(s)) {
 699                         pr_err("zpool %s not available\n", s);
 700                         return -ENOENT;
 701                 }
 702                 type = s;
 703         } else if (!compressor) {
 704                 if (!crypto_has_comp(s, 0, 0)) {
 705                         pr_err("compressor %s not available\n", s);
 706                         return -ENOENT;
 707                 }
 708                 compressor = s;
 709         } else {
 710                 WARN_ON(1);
 711                 return -EINVAL;
 712         }
 713
 714         spin_lock(&zswap_pools_lock);
 715
 716         pool = zswap_pool_find_get(type, compressor);
 717         if (pool) {
 718                 zswap_pool_debug("using existing", pool);
 719                 WARN_ON(pool == zswap_pool_current());
 720                 list_del_rcu(&pool->list);
 721         }
 722
 723         spin_unlock(&zswap_pools_lock);
 724
 725         if (!pool)
 726                 pool = zswap_pool_create(type, compressor);
 727
 728         if (pool)
 729                 ret = param_set_charp(s, kp);
 730         else
 731                 ret = -EINVAL;
 732
 733         spin_lock(&zswap_pools_lock);
 734
 735         if (!ret) {
 736                 put_pool = zswap_pool_current();
 737                 list_add_rcu(&pool->list, &zswap_pools);
 738                 zswap_has_pool = true;
 739         } else if (pool) {
 740                 /* add the possibly pre-existing pool to the end of the pools
 741                  * list; if it's new (and empty) then it'll be removed and
 742                  * destroyed by the put after we drop the lock
 743                  */
 744                 list_add_tail_rcu(&pool->list, &zswap_pools);
 745                 put_pool = pool;
 746         }
 747
 748         spin_unlock(&zswap_pools_lock);
 749
 750         if (!zswap_has_pool && !pool) {
 751                 /* if initial pool creation failed, and this pool creation also
 752                  * failed, maybe both compressor and zpool params were bad.
 753                  * Allow changing this param, so pool creation will succeed
 754                  * when the other param is changed. We already verified this
 755                  * param is ok in the zpool_has_pool() or crypto_has_comp()
 756                  * checks above.
 757                  */
 758                 ret = param_set_charp(s, kp);
 759         }
 760
 761         /* drop the ref from either the old current pool,
 762          * or the new pool we failed to add
 763          */
 764         if (put_pool)
 765                 zswap_pool_put(put_pool);
 766
 767         return ret;
 768 }
 769
 770 static int zswap_compressor_param_set(const char *val,
 771                                       const struct kernel_param *kp)
 772 {
 773         return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
 774 }
 775
 776 static int zswap_zpool_param_set(const char *val,
 777                                  const struct kernel_param *kp)
 778 {
 779         return __zswap_param_set(val, kp, NULL, zswap_compressor);
 780 }
 781
 782 static int zswap_enabled_param_set(const char *val,
 783                                    const struct kernel_param *kp)
 784 {
 785         if (zswap_init_failed) {
 786                 pr_err("can't enable, initialization failed\n");
 787                 return -ENODEV;
 788         }
 789         if (!zswap_has_pool && zswap_init_started) {
 790                 pr_err("can't enable, no pool configured\n");
 791                 return -ENODEV;
 792         }
 793
 794         return param_set_bool(val, kp);
 795 }
 796
 797 /*********************************
 798 * writeback code
 799 **********************************/
 800 /* return enum for zswap_get_swap_cache_page */
 801 enum zswap_get_swap_ret {
 802         ZSWAP_SWAPCACHE_NEW,
 803         ZSWAP_SWAPCACHE_EXIST,
 804         ZSWAP_SWAPCACHE_FAIL,
 805 };
 806
 807 /*
 808  * zswap_get_swap_cache_page
 809  *
 810  * This is an adaption of read_swap_cache_async()
 811  *
 812  * This function tries to find a page with the given swap entry
 813  * in the swapper_space address space (the swap cache).  If the page
 814  * is found, it is returned in retpage.  Otherwise, a page is allocated,
 815  * added to the swap cache, and returned in retpage.
 816  *
 817  * If success, the swap cache page is returned in retpage
 818  * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
 819  * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
 820  *     the new page is added to swapcache and locked
 821  * Returns ZSWAP_SWAPCACHE_FAIL on error
 822  */
 823 static int zswap_get_swap_cache_page(swp_entry_t entry,
 824                                 struct page **retpage)
 825 {
 826         bool page_was_allocated;
 827
 828         *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
 829                         NULL, 0, &page_was_allocated);
 830         if (page_was_allocated)
 831                 return ZSWAP_SWAPCACHE_NEW;
 832         if (!*retpage)
 833                 return ZSWAP_SWAPCACHE_FAIL;
 834         return ZSWAP_SWAPCACHE_EXIST;
 835 }
 836
 837 /*
 838  * Attempts to free an entry by adding a page to the swap cache,
 839  * decompressing the entry data into the page, and issuing a
 840  * bio write to write the page back to the swap device.
 841  *
 842  * This can be thought of as a "resumed writeback" of the page
 843  * to the swap device.  We are basically resuming the same swap
 844  * writeback path that was intercepted with the frontswap_store()
 845  * in the first place.  After the page has been decompressed into
 846  * the swap cache, the compressed version stored by zswap can be
 847  * freed.
 848  */
 849 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 850 {
 851         struct zswap_header *zhdr;
 852         swp_entry_t swpentry;
 853         struct zswap_tree *tree;
 854         pgoff_t offset;
 855         struct zswap_entry *entry;
 856         struct page *page;
 857         struct crypto_comp *tfm;
 858         u8 *src, *dst;
 859         unsigned int dlen;
 860         int ret;
 861         struct writeback_control wbc = {
 862                 .sync_mode = WB_SYNC_NONE,
 863         };
 864
 865         /* extract swpentry from data */
 866         zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
 867         swpentry = zhdr->swpentry; /* here */
 868         zpool_unmap_handle(pool, handle);
 869         tree = zswap_trees[swp_type(swpentry)];
 870         offset = swp_offset(swpentry);
 871
 872         /* find and ref zswap entry */
 873         spin_lock(&tree->lock);
 874         entry = zswap_entry_find_get(&tree->rbroot, offset);
 875         if (!entry) {
 876                 /* entry was invalidated */
 877                 spin_unlock(&tree->lock);
 878                 return 0;
 879         }
 880         spin_unlock(&tree->lock);
 881         BUG_ON(offset != entry->offset);
 882
 883         /* try to allocate swap cache page */
 884         switch (zswap_get_swap_cache_page(swpentry, &page)) {
 885         case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
 886                 ret = -ENOMEM;
 887                 goto fail;
 888
 889         case ZSWAP_SWAPCACHE_EXIST:
 890                 /* page is already in the swap cache, ignore for now */
 891                 put_page(page);
 892                 ret = -EEXIST;
 893                 goto fail;
 894
 895         case ZSWAP_SWAPCACHE_NEW: /* page is locked */
 896                 /* decompress */
 897                 dlen = PAGE_SIZE;
 898                 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
 899                                 ZPOOL_MM_RO) + sizeof(struct zswap_header);
 900                 dst = kmap_atomic(page);
 901                 tfm = *get_cpu_ptr(entry->pool->tfm);
 902                 ret = crypto_comp_decompress(tfm, src, entry->length,
 903                                              dst, &dlen);
 904                 put_cpu_ptr(entry->pool->tfm);
 905                 kunmap_atomic(dst);
 906                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
 907                 BUG_ON(ret);
 908                 BUG_ON(dlen != PAGE_SIZE);
 909
 910                 /* page is up to date */
 911                 SetPageUptodate(page);
 912         }
 913
 914         /* move it to the tail of the inactive list after end_writeback */
 915         SetPageReclaim(page);
 916
 917         /* start writeback */
 918         __swap_writepage(page, &wbc, end_swap_bio_write);
 919         put_page(page);
 920         zswap_written_back_pages++;
 921
 922         spin_lock(&tree->lock);
 923         /* drop local reference */
 924         zswap_entry_put(tree, entry);
 925
 926         /*
 927         * There are two possible situations for entry here:
 928         * (1) refcount is 1(normal case),  entry is valid and on the tree
 929         * (2) refcount is 0, entry is freed and not on the tree
 930         *     because invalidate happened during writeback
 931         *  search the tree and free the entry if find entry
 932         */
 933         if (entry == zswap_rb_search(&tree->rbroot, offset))
 934                 zswap_entry_put(tree, entry);
 935         spin_unlock(&tree->lock);
 936
 937         goto end;
 938
 939         /*
 940         * if we get here due to ZSWAP_SWAPCACHE_EXIST
 941         * a load may happening concurrently
 942         * it is safe and okay to not free the entry
 943         * if we free the entry in the following put
 944         * it it either okay to return !0
 945         */
 946 fail:
 947         spin_lock(&tree->lock);
 948         zswap_entry_put(tree, entry);
 949         spin_unlock(&tree->lock);
 950
 951 end:
 952         return ret;
 953 }
 954
 955 static int zswap_shrink(void)
 956 {
 957         struct zswap_pool *pool;
 958         int ret;
 959
 960         pool = zswap_pool_last_get();
 961         if (!pool)
 962                 return -ENOENT;
 963
 964         ret = zpool_shrink(pool->zpool, 1, NULL);
 965
 966         zswap_pool_put(pool);
 967
 968         return ret;
 969 }
 970
 971 static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
 972 {
 973         unsigned int pos;
 974         unsigned long *page;
 975
 976         page = (unsigned long *)ptr;
 977         for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
 978                 if (page[pos] != page[0])
 979                         return 0;
 980         }
 981         *value = page[0];
 982         return 1;
 983 }
 984
 985 static void zswap_fill_page(void *ptr, unsigned long value)
 986 {
 987         unsigned long *page;
 988
 989         page = (unsigned long *)ptr;
 990         memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
 991 }
 992
 993 /*********************************
 994 * frontswap hooks
 995 **********************************/
 996 /* attempts to compress and store an single page */
 997 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 998                                 struct page *page)
 999 {
1000         struct zswap_tree *tree = zswap_trees[type];
1001         struct zswap_entry *entry, *dupentry;
1002         struct crypto_comp *tfm;
1003         int ret;
1004         unsigned int hlen, dlen = PAGE_SIZE;
1005         unsigned long handle, value;
1006         char *buf;
1007         u8 *src, *dst;
1008         struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
1009
1010         /* THP isn't supported */
1011         if (PageTransHuge(page)) {
1012                 ret = -EINVAL;
1013                 goto reject;
1014         }
1015
1016         if (!zswap_enabled || !tree) {
1017                 ret = -ENODEV;
1018                 goto reject;
1019         }
1020
1021         /* reclaim space if needed */
1022         if (zswap_is_full()) {
1023                 zswap_pool_limit_hit++;
1024                 if (zswap_shrink()) {
1025                         zswap_reject_reclaim_fail++;
1026                         ret = -ENOMEM;
1027                         goto reject;
1028                 }
1029         }
1030
1031         /* allocate entry */
1032         entry = zswap_entry_cache_alloc(GFP_KERNEL);
1033         if (!entry) {
1034                 zswap_reject_kmemcache_fail++;
1035                 ret = -ENOMEM;
1036                 goto reject;
1037         }
1038
1039         if (zswap_same_filled_pages_enabled) {
1040                 src = kmap_atomic(page);
1041                 if (zswap_is_page_same_filled(src, &value)) {
1042                         kunmap_atomic(src);
1043                         entry->offset = offset;
1044                         entry->length = 0;
1045                         entry->value = value;
1046                         atomic_inc(&zswap_same_filled_pages);
1047                         goto insert_entry;
1048                 }
1049                 kunmap_atomic(src);
1050         }
1051
1052         /* if entry is successfully added, it keeps the reference */
1053         entry->pool = zswap_pool_current_get();
1054         if (!entry->pool) {
1055                 ret = -EINVAL;
1056                 goto freepage;
1057         }
1058
1059         /* compress */
1060         dst = get_cpu_var(zswap_dstmem);
1061         tfm = *get_cpu_ptr(entry->pool->tfm);
1062         src = kmap_atomic(page);
1063         ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
1064         kunmap_atomic(src);
1065         put_cpu_ptr(entry->pool->tfm);
1066         if (ret) {
1067                 ret = -EINVAL;
1068                 goto put_dstmem;
1069         }
1070
1071         /* store */
1072         hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1073         ret = zpool_malloc(entry->pool->zpool, hlen + dlen,
1074                            __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
1075                            &handle);
1076         if (ret == -ENOSPC) {
1077                 zswap_reject_compress_poor++;
1078                 goto put_dstmem;
1079         }
1080         if (ret) {
1081                 zswap_reject_alloc_fail++;
1082                 goto put_dstmem;
1083         }
1084         buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1085         memcpy(buf, &zhdr, hlen);
1086         memcpy(buf + hlen, dst, dlen);
1087         zpool_unmap_handle(entry->pool->zpool, handle);
1088         put_cpu_var(zswap_dstmem);
1089
1090         /* populate entry */
1091         entry->offset = offset;
1092         entry->handle = handle;
1093         entry->length = dlen;
1094
1095 insert_entry:
1096         /* map */
1097         spin_lock(&tree->lock);
1098         do {
1099                 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1100                 if (ret == -EEXIST) {
1101                         zswap_duplicate_entry++;
1102                         /* remove from rbtree */
1103                         zswap_rb_erase(&tree->rbroot, dupentry);
1104                         zswap_entry_put(tree, dupentry);
1105                 }
1106         } while (ret == -EEXIST);
1107         spin_unlock(&tree->lock);
1108
1109         /* update stats */
1110         atomic_inc(&zswap_stored_pages);
1111         zswap_update_total_size();
1112
1113         return 0;
1114
1115 put_dstmem:
1116         put_cpu_var(zswap_dstmem);
1117         zswap_pool_put(entry->pool);
1118 freepage:
1119         zswap_entry_cache_free(entry);
1120 reject:
1121         return ret;
1122 }
1123
1124 /*
1125  * returns 0 if the page was successfully decompressed
1126  * return -1 on entry not found or error
1127 */
1128 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1129                                 struct page *page)
1130 {
1131         struct zswap_tree *tree = zswap_trees[type];
1132         struct zswap_entry *entry;
1133         struct crypto_comp *tfm;
1134         u8 *src, *dst;
1135         unsigned int dlen;
1136         int ret;
1137
1138         /* find */
1139         spin_lock(&tree->lock);
1140         entry = zswap_entry_find_get(&tree->rbroot, offset);
1141         if (!entry) {
1142                 /* entry was written back */
1143                 spin_unlock(&tree->lock);
1144                 return -1;
1145         }
1146         spin_unlock(&tree->lock);
1147
1148         if (!entry->length) {
1149                 dst = kmap_atomic(page);
1150                 zswap_fill_page(dst, entry->value);
1151                 kunmap_atomic(dst);
1152                 goto freeentry;
1153         }
1154
1155         /* decompress */
1156         dlen = PAGE_SIZE;
1157         src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1158         if (zpool_evictable(entry->pool->zpool))
1159                 src += sizeof(struct zswap_header);
1160         dst = kmap_atomic(page);
1161         tfm = *get_cpu_ptr(entry->pool->tfm);
1162         ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1163         put_cpu_ptr(entry->pool->tfm);
1164         kunmap_atomic(dst);
1165         zpool_unmap_handle(entry->pool->zpool, entry->handle);
1166         BUG_ON(ret);
1167
1168 freeentry:
1169         spin_lock(&tree->lock);
1170         zswap_entry_put(tree, entry);
1171         spin_unlock(&tree->lock);
1172
1173         return 0;
1174 }
1175
1176 /* frees an entry in zswap */
1177 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1178 {
1179         struct zswap_tree *tree = zswap_trees[type];
1180         struct zswap_entry *entry;
1181
1182         /* find */
1183         spin_lock(&tree->lock);
1184         entry = zswap_rb_search(&tree->rbroot, offset);
1185         if (!entry) {
1186                 /* entry was written back */
1187                 spin_unlock(&tree->lock);
1188                 return;
1189         }
1190
1191         /* remove from rbtree */
1192         zswap_rb_erase(&tree->rbroot, entry);
1193
1194         /* drop the initial reference from entry creation */
1195         zswap_entry_put(tree, entry);
1196
1197         spin_unlock(&tree->lock);
1198 }
1199
1200 /* frees all zswap entries for the given swap type */
1201 static void zswap_frontswap_invalidate_area(unsigned type)
1202 {
1203         struct zswap_tree *tree = zswap_trees[type];
1204         struct zswap_entry *entry, *n;
1205
1206         if (!tree)
1207                 return;
1208
1209         /* walk the tree and free everything */
1210         spin_lock(&tree->lock);
1211         rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1212                 zswap_free_entry(entry);
1213         tree->rbroot = RB_ROOT;
1214         spin_unlock(&tree->lock);
1215         kfree(tree);
1216         zswap_trees[type] = NULL;
1217 }
1218
1219 static void zswap_frontswap_init(unsigned type)
1220 {
1221         struct zswap_tree *tree;
1222
1223         tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1224         if (!tree) {
1225                 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1226                 return;
1227         }
1228
1229         tree->rbroot = RB_ROOT;
1230         spin_lock_init(&tree->lock);
1231         zswap_trees[type] = tree;
1232 }
1233
1234 static struct frontswap_ops zswap_frontswap_ops = {
1235         .store = zswap_frontswap_store,
1236         .load = zswap_frontswap_load,
1237         .invalidate_page = zswap_frontswap_invalidate_page,
1238         .invalidate_area = zswap_frontswap_invalidate_area,
1239         .init = zswap_frontswap_init
1240 };
1241
1242 /*********************************
1243 * debugfs functions
1244 **********************************/
1245 #ifdef CONFIG_DEBUG_FS
1246 #include <linux/debugfs.h>
1247
1248 static struct dentry *zswap_debugfs_root;
1249
1250 static int __init zswap_debugfs_init(void)
1251 {
1252         if (!debugfs_initialized())
1253                 return -ENODEV;
1254
1255         zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1256         if (!zswap_debugfs_root)
1257                 return -ENOMEM;
1258
1259         debugfs_create_u64("pool_limit_hit", S_IRUGO,
1260                         zswap_debugfs_root, &zswap_pool_limit_hit);
1261         debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
1262                         zswap_debugfs_root, &zswap_reject_reclaim_fail);
1263         debugfs_create_u64("reject_alloc_fail", S_IRUGO,
1264                         zswap_debugfs_root, &zswap_reject_alloc_fail);
1265         debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
1266                         zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1267         debugfs_create_u64("reject_compress_poor", S_IRUGO,
1268                         zswap_debugfs_root, &zswap_reject_compress_poor);
1269         debugfs_create_u64("written_back_pages", S_IRUGO,
1270                         zswap_debugfs_root, &zswap_written_back_pages);
1271         debugfs_create_u64("duplicate_entry", S_IRUGO,
1272                         zswap_debugfs_root, &zswap_duplicate_entry);
1273         debugfs_create_u64("pool_total_size", S_IRUGO,
1274                         zswap_debugfs_root, &zswap_pool_total_size);
1275         debugfs_create_atomic_t("stored_pages", S_IRUGO,
1276                         zswap_debugfs_root, &zswap_stored_pages);
1277         debugfs_create_atomic_t("same_filled_pages", 0444,
1278                         zswap_debugfs_root, &zswap_same_filled_pages);
1279
1280         return 0;
1281 }
1282
1283 static void __exit zswap_debugfs_exit(void)
1284 {
1285         debugfs_remove_recursive(zswap_debugfs_root);
1286 }
1287 #else
1288 static int __init zswap_debugfs_init(void)
1289 {
1290         return 0;
1291 }
1292
1293 static void __exit zswap_debugfs_exit(void) { }
1294 #endif
1295
1296 /*********************************
1297 * module init and exit
1298 **********************************/
1299 static int __init init_zswap(void)
1300 {
1301         struct zswap_pool *pool;
1302         int ret;
1303
1304         zswap_init_started = true;
1305
1306         if (zswap_entry_cache_create()) {
1307                 pr_err("entry cache creation failed\n");
1308                 goto cache_fail;
1309         }
1310
1311         ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1312                                 zswap_dstmem_prepare, zswap_dstmem_dead);
1313         if (ret) {
1314                 pr_err("dstmem alloc failed\n");
1315                 goto dstmem_fail;
1316         }
1317
1318         ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1319                                       "mm/zswap_pool:prepare",
1320                                       zswap_cpu_comp_prepare,
1321                                       zswap_cpu_comp_dead);
1322         if (ret)
1323                 goto hp_fail;
1324
1325         pool = __zswap_pool_create_fallback();
1326         if (pool) {
1327                 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1328                         zpool_get_type(pool->zpool));
1329                 list_add(&pool->list, &zswap_pools);
1330                 zswap_has_pool = true;
1331         } else {
1332                 pr_err("pool creation failed\n");
1333                 zswap_enabled = false;
1334         }
1335
1336         frontswap_register_ops(&zswap_frontswap_ops);
1337         if (zswap_debugfs_init())
1338                 pr_warn("debugfs initialization failed\n");
1339         return 0;
1340
1341 hp_fail:
1342         cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1343 dstmem_fail:
1344         zswap_entry_cache_destroy();
1345 cache_fail:
1346         /* if built-in, we aren't unloaded on failure; don't allow use */
1347         zswap_init_failed = true;
1348         zswap_enabled = false;
1349         return -ENOMEM;
1350 }
1351 /* must be late so crypto has time to come up */
1352 late_initcall(init_zswap);
1353
1354 MODULE_LICENSE("GPL");
1355 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1356 MODULE_DESCRIPTION("Compressed cache for swap pages");