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