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