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                 return -ENOMEM;
 376
 377         per_cpu(zswap_dstmem, cpu) = dst;
 378         return 0;
 379 }
 380
 381 static int zswap_dstmem_dead(unsigned int cpu)
 382 {
 383         u8 *dst;
 384
 385         dst = per_cpu(zswap_dstmem, cpu);
 386         kfree(dst);
 387         per_cpu(zswap_dstmem, cpu) = NULL;
 388
 389         return 0;
 390 }
 391
 392 static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 393 {
 394         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 395         struct crypto_comp *tfm;
 396
 397         if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
 398                 return 0;
 399
 400         tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
 401         if (IS_ERR_OR_NULL(tfm)) {
 402                 pr_err("could not alloc crypto comp %s : %ld\n",
 403                        pool->tfm_name, PTR_ERR(tfm));
 404                 return -ENOMEM;
 405         }
 406         *per_cpu_ptr(pool->tfm, cpu) = tfm;
 407         return 0;
 408 }
 409
 410 static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 411 {
 412         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 413         struct crypto_comp *tfm;
 414
 415         tfm = *per_cpu_ptr(pool->tfm, cpu);
 416         if (!IS_ERR_OR_NULL(tfm))
 417                 crypto_free_comp(tfm);
 418         *per_cpu_ptr(pool->tfm, cpu) = NULL;
 419         return 0;
 420 }
 421
 422 /*********************************
 423 * pool functions
 424 **********************************/
 425
 426 static struct zswap_pool *__zswap_pool_current(void)
 427 {
 428         struct zswap_pool *pool;
 429
 430         pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
 431         WARN_ONCE(!pool && zswap_has_pool,
 432                   "%s: no page storage pool!\n", __func__);
 433
 434         return pool;
 435 }
 436
 437 static struct zswap_pool *zswap_pool_current(void)
 438 {
 439         assert_spin_locked(&zswap_pools_lock);
 440
 441         return __zswap_pool_current();
 442 }
 443
 444 static struct zswap_pool *zswap_pool_current_get(void)
 445 {
 446         struct zswap_pool *pool;
 447
 448         rcu_read_lock();
 449
 450         pool = __zswap_pool_current();
 451         if (!zswap_pool_get(pool))
 452                 pool = NULL;
 453
 454         rcu_read_unlock();
 455
 456         return pool;
 457 }
 458
 459 static struct zswap_pool *zswap_pool_last_get(void)
 460 {
 461         struct zswap_pool *pool, *last = NULL;
 462
 463         rcu_read_lock();
 464
 465         list_for_each_entry_rcu(pool, &zswap_pools, list)
 466                 last = pool;
 467         WARN_ONCE(!last && zswap_has_pool,
 468                   "%s: no page storage pool!\n", __func__);
 469         if (!zswap_pool_get(last))
 470                 last = NULL;
 471
 472         rcu_read_unlock();
 473
 474         return last;
 475 }
 476
 477 /* type and compressor must be null-terminated */
 478 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
 479 {
 480         struct zswap_pool *pool;
 481
 482         assert_spin_locked(&zswap_pools_lock);
 483
 484         list_for_each_entry_rcu(pool, &zswap_pools, list) {
 485                 if (strcmp(pool->tfm_name, compressor))
 486                         continue;
 487                 if (strcmp(zpool_get_type(pool->zpool), type))
 488                         continue;
 489                 /* if we can't get it, it's about to be destroyed */
 490                 if (!zswap_pool_get(pool))
 491                         continue;
 492                 return pool;
 493         }
 494
 495         return NULL;
 496 }
 497
 498 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
 499 {
 500         struct zswap_pool *pool;
 501         char name[38]; /* 'zswap' + 32 char (max) num + \0 */
 502         gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
 503         int ret;
 504
 505         if (!zswap_has_pool) {
 506                 /* if either are unset, pool initialization failed, and we
 507                  * need both params to be set correctly before trying to
 508                  * create a pool.
 509                  */
 510                 if (!strcmp(type, ZSWAP_PARAM_UNSET))
 511                         return NULL;
 512                 if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
 513                         return NULL;
 514         }
 515
 516         pool = kzalloc(sizeof(*pool), GFP_KERNEL);
 517         if (!pool)
 518                 return NULL;
 519
 520         /* unique name for each pool specifically required by zsmalloc */
 521         snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
 522
 523         pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
 524         if (!pool->zpool) {
 525                 pr_err("%s zpool not available\n", type);
 526                 goto error;
 527         }
 528         pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
 529
 530         strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
 531         pool->tfm = alloc_percpu(struct crypto_comp *);
 532         if (!pool->tfm) {
 533                 pr_err("percpu alloc failed\n");
 534                 goto error;
 535         }
 536
 537         ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
 538                                        &pool->node);
 539         if (ret)
 540                 goto error;
 541         pr_debug("using %s compressor\n", pool->tfm_name);
 542
 543         /* being the current pool takes 1 ref; this func expects the
 544          * caller to always add the new pool as the current pool
 545          */
 546         kref_init(&pool->kref);
 547         INIT_LIST_HEAD(&pool->list);
 548
 549         zswap_pool_debug("created", pool);
 550
 551         return pool;
 552
 553 error:
 554         free_percpu(pool->tfm);
 555         if (pool->zpool)
 556                 zpool_destroy_pool(pool->zpool);
 557         kfree(pool);
 558         return NULL;
 559 }
 560
 561 static __init struct zswap_pool *__zswap_pool_create_fallback(void)
 562 {
 563         bool has_comp, has_zpool;
 564
 565         has_comp = crypto_has_comp(zswap_compressor, 0, 0);
 566         if (!has_comp && strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
 567                 pr_err("compressor %s not available, using default %s\n",
 568                        zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
 569                 param_free_charp(&zswap_compressor);
 570                 zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
 571                 has_comp = crypto_has_comp(zswap_compressor, 0, 0);
 572         }
 573         if (!has_comp) {
 574                 pr_err("default compressor %s not available\n",
 575                        zswap_compressor);
 576                 param_free_charp(&zswap_compressor);
 577                 zswap_compressor = ZSWAP_PARAM_UNSET;
 578         }
 579
 580         has_zpool = zpool_has_pool(zswap_zpool_type);
 581         if (!has_zpool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
 582                 pr_err("zpool %s not available, using default %s\n",
 583                        zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
 584                 param_free_charp(&zswap_zpool_type);
 585                 zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
 586                 has_zpool = zpool_has_pool(zswap_zpool_type);
 587         }
 588         if (!has_zpool) {
 589                 pr_err("default zpool %s not available\n",
 590                        zswap_zpool_type);
 591                 param_free_charp(&zswap_zpool_type);
 592                 zswap_zpool_type = ZSWAP_PARAM_UNSET;
 593         }
 594
 595         if (!has_comp || !has_zpool)
 596                 return NULL;
 597
 598         return zswap_pool_create(zswap_zpool_type, zswap_compressor);
 599 }
 600
 601 static void zswap_pool_destroy(struct zswap_pool *pool)
 602 {
 603         zswap_pool_debug("destroying", pool);
 604
 605         cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
 606         free_percpu(pool->tfm);
 607         zpool_destroy_pool(pool->zpool);
 608         kfree(pool);
 609 }
 610
 611 static int __must_check zswap_pool_get(struct zswap_pool *pool)
 612 {
 613         if (!pool)
 614                 return 0;
 615
 616         return kref_get_unless_zero(&pool->kref);
 617 }
 618
 619 static void __zswap_pool_release(struct work_struct *work)
 620 {
 621         struct zswap_pool *pool = container_of(work, typeof(*pool), work);
 622
 623         synchronize_rcu();
 624
 625         /* nobody should have been able to get a kref... */
 626         WARN_ON(kref_get_unless_zero(&pool->kref));
 627
 628         /* pool is now off zswap_pools list and has no references. */
 629         zswap_pool_destroy(pool);
 630 }
 631
 632 static void __zswap_pool_empty(struct kref *kref)
 633 {
 634         struct zswap_pool *pool;
 635
 636         pool = container_of(kref, typeof(*pool), kref);
 637
 638         spin_lock(&zswap_pools_lock);
 639
 640         WARN_ON(pool == zswap_pool_current());
 641
 642         list_del_rcu(&pool->list);
 643
 644         INIT_WORK(&pool->work, __zswap_pool_release);
 645         schedule_work(&pool->work);
 646
 647         spin_unlock(&zswap_pools_lock);
 648 }
 649
 650 static void zswap_pool_put(struct zswap_pool *pool)
 651 {
 652         kref_put(&pool->kref, __zswap_pool_empty);
 653 }
 654
 655 /*********************************
 656 * param callbacks
 657 **********************************/
 658
 659 /* val must be a null-terminated string */
 660 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
 661                              char *type, char *compressor)
 662 {
 663         struct zswap_pool *pool, *put_pool = NULL;
 664         char *s = strstrip((char *)val);
 665         int ret;
 666
 667         if (zswap_init_failed) {
 668                 pr_err("can't set param, initialization failed\n");
 669                 return -ENODEV;
 670         }
 671
 672         /* no change required */
 673         if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
 674                 return 0;
 675
 676         /* if this is load-time (pre-init) param setting,
 677          * don't create a pool; that's done during init.
 678          */
 679         if (!zswap_init_started)
 680                 return param_set_charp(s, kp);
 681
 682         if (!type) {
 683                 if (!zpool_has_pool(s)) {
 684                         pr_err("zpool %s not available\n", s);
 685                         return -ENOENT;
 686                 }
 687                 type = s;
 688         } else if (!compressor) {
 689                 if (!crypto_has_comp(s, 0, 0)) {
 690                         pr_err("compressor %s not available\n", s);
 691                         return -ENOENT;
 692                 }
 693                 compressor = s;
 694         } else {
 695                 WARN_ON(1);
 696                 return -EINVAL;
 697         }
 698
 699         spin_lock(&zswap_pools_lock);
 700
 701         pool = zswap_pool_find_get(type, compressor);
 702         if (pool) {
 703                 zswap_pool_debug("using existing", pool);
 704                 WARN_ON(pool == zswap_pool_current());
 705                 list_del_rcu(&pool->list);
 706         }
 707
 708         spin_unlock(&zswap_pools_lock);
 709
 710         if (!pool)
 711                 pool = zswap_pool_create(type, compressor);
 712
 713         if (pool)
 714                 ret = param_set_charp(s, kp);
 715         else
 716                 ret = -EINVAL;
 717
 718         spin_lock(&zswap_pools_lock);
 719
 720         if (!ret) {
 721                 put_pool = zswap_pool_current();
 722                 list_add_rcu(&pool->list, &zswap_pools);
 723                 zswap_has_pool = true;
 724         } else if (pool) {
 725                 /* add the possibly pre-existing pool to the end of the pools
 726                  * list; if it's new (and empty) then it'll be removed and
 727                  * destroyed by the put after we drop the lock
 728                  */
 729                 list_add_tail_rcu(&pool->list, &zswap_pools);
 730                 put_pool = pool;
 731         }
 732
 733         spin_unlock(&zswap_pools_lock);
 734
 735         if (!zswap_has_pool && !pool) {
 736                 /* if initial pool creation failed, and this pool creation also
 737                  * failed, maybe both compressor and zpool params were bad.
 738                  * Allow changing this param, so pool creation will succeed
 739                  * when the other param is changed. We already verified this
 740                  * param is ok in the zpool_has_pool() or crypto_has_comp()
 741                  * checks above.
 742                  */
 743                 ret = param_set_charp(s, kp);
 744         }
 745
 746         /* drop the ref from either the old current pool,
 747          * or the new pool we failed to add
 748          */
 749         if (put_pool)
 750                 zswap_pool_put(put_pool);
 751
 752         return ret;
 753 }
 754
 755 static int zswap_compressor_param_set(const char *val,
 756                                       const struct kernel_param *kp)
 757 {
 758         return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
 759 }
 760
 761 static int zswap_zpool_param_set(const char *val,
 762                                  const struct kernel_param *kp)
 763 {
 764         return __zswap_param_set(val, kp, NULL, zswap_compressor);
 765 }
 766
 767 static int zswap_enabled_param_set(const char *val,
 768                                    const struct kernel_param *kp)
 769 {
 770         if (zswap_init_failed) {
 771                 pr_err("can't enable, initialization failed\n");
 772                 return -ENODEV;
 773         }
 774         if (!zswap_has_pool && zswap_init_started) {
 775                 pr_err("can't enable, no pool configured\n");
 776                 return -ENODEV;
 777         }
 778
 779         return param_set_bool(val, kp);
 780 }
 781
 782 /*********************************
 783 * writeback code
 784 **********************************/
 785 /* return enum for zswap_get_swap_cache_page */
 786 enum zswap_get_swap_ret {
 787         ZSWAP_SWAPCACHE_NEW,
 788         ZSWAP_SWAPCACHE_EXIST,
 789         ZSWAP_SWAPCACHE_FAIL,
 790 };
 791
 792 /*
 793  * zswap_get_swap_cache_page
 794  *
 795  * This is an adaption of read_swap_cache_async()
 796  *
 797  * This function tries to find a page with the given swap entry
 798  * in the swapper_space address space (the swap cache).  If the page
 799  * is found, it is returned in retpage.  Otherwise, a page is allocated,
 800  * added to the swap cache, and returned in retpage.
 801  *
 802  * If success, the swap cache page is returned in retpage
 803  * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
 804  * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
 805  *     the new page is added to swapcache and locked
 806  * Returns ZSWAP_SWAPCACHE_FAIL on error
 807  */
 808 static int zswap_get_swap_cache_page(swp_entry_t entry,
 809                                 struct page **retpage)
 810 {
 811         bool page_was_allocated;
 812
 813         *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
 814                         NULL, 0, &page_was_allocated);
 815         if (page_was_allocated)
 816                 return ZSWAP_SWAPCACHE_NEW;
 817         if (!*retpage)
 818                 return ZSWAP_SWAPCACHE_FAIL;
 819         return ZSWAP_SWAPCACHE_EXIST;
 820 }
 821
 822 /*
 823  * Attempts to free an entry by adding a page to the swap cache,
 824  * decompressing the entry data into the page, and issuing a
 825  * bio write to write the page back to the swap device.
 826  *
 827  * This can be thought of as a "resumed writeback" of the page
 828  * to the swap device.  We are basically resuming the same swap
 829  * writeback path that was intercepted with the frontswap_store()
 830  * in the first place.  After the page has been decompressed into
 831  * the swap cache, the compressed version stored by zswap can be
 832  * freed.
 833  */
 834 static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 835 {
 836         struct zswap_header *zhdr;
 837         swp_entry_t swpentry;
 838         struct zswap_tree *tree;
 839         pgoff_t offset;
 840         struct zswap_entry *entry;
 841         struct page *page;
 842         struct crypto_comp *tfm;
 843         u8 *src, *dst;
 844         unsigned int dlen;
 845         int ret;
 846         struct writeback_control wbc = {
 847                 .sync_mode = WB_SYNC_NONE,
 848         };
 849
 850         /* extract swpentry from data */
 851         zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
 852         swpentry = zhdr->swpentry; /* here */
 853         zpool_unmap_handle(pool, handle);
 854         tree = zswap_trees[swp_type(swpentry)];
 855         offset = swp_offset(swpentry);
 856
 857         /* find and ref zswap entry */
 858         spin_lock(&tree->lock);
 859         entry = zswap_entry_find_get(&tree->rbroot, offset);
 860         if (!entry) {
 861                 /* entry was invalidated */
 862                 spin_unlock(&tree->lock);
 863                 return 0;
 864         }
 865         spin_unlock(&tree->lock);
 866         BUG_ON(offset != entry->offset);
 867
 868         /* try to allocate swap cache page */
 869         switch (zswap_get_swap_cache_page(swpentry, &page)) {
 870         case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
 871                 ret = -ENOMEM;
 872                 goto fail;
 873
 874         case ZSWAP_SWAPCACHE_EXIST:
 875                 /* page is already in the swap cache, ignore for now */
 876                 put_page(page);
 877                 ret = -EEXIST;
 878                 goto fail;
 879
 880         case ZSWAP_SWAPCACHE_NEW: /* page is locked */
 881                 /* decompress */
 882                 dlen = PAGE_SIZE;
 883                 src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
 884                                 ZPOOL_MM_RO) + sizeof(struct zswap_header);
 885                 dst = kmap_atomic(page);
 886                 tfm = *get_cpu_ptr(entry->pool->tfm);
 887                 ret = crypto_comp_decompress(tfm, src, entry->length,
 888                                              dst, &dlen);
 889                 put_cpu_ptr(entry->pool->tfm);
 890                 kunmap_atomic(dst);
 891                 zpool_unmap_handle(entry->pool->zpool, entry->handle);
 892                 BUG_ON(ret);
 893                 BUG_ON(dlen != PAGE_SIZE);
 894
 895                 /* page is up to date */
 896                 SetPageUptodate(page);
 897         }
 898
 899         /* move it to the tail of the inactive list after end_writeback */
 900         SetPageReclaim(page);
 901
 902         /* start writeback */
 903         __swap_writepage(page, &wbc, end_swap_bio_write);
 904         put_page(page);
 905         zswap_written_back_pages++;
 906
 907         spin_lock(&tree->lock);
 908         /* drop local reference */
 909         zswap_entry_put(tree, entry);
 910
 911         /*
 912         * There are two possible situations for entry here:
 913         * (1) refcount is 1(normal case),  entry is valid and on the tree
 914         * (2) refcount is 0, entry is freed and not on the tree
 915         *     because invalidate happened during writeback
 916         *  search the tree and free the entry if find entry
 917         */
 918         if (entry == zswap_rb_search(&tree->rbroot, offset))
 919                 zswap_entry_put(tree, entry);
 920         spin_unlock(&tree->lock);
 921
 922         goto end;
 923
 924         /*
 925         * if we get here due to ZSWAP_SWAPCACHE_EXIST
 926         * a load may happening concurrently
 927         * it is safe and okay to not free the entry
 928         * if we free the entry in the following put
 929         * it it either okay to return !0
 930         */
 931 fail:
 932         spin_lock(&tree->lock);
 933         zswap_entry_put(tree, entry);
 934         spin_unlock(&tree->lock);
 935
 936 end:
 937         return ret;
 938 }
 939
 940 static int zswap_shrink(void)
 941 {
 942         struct zswap_pool *pool;
 943         int ret;
 944
 945         pool = zswap_pool_last_get();
 946         if (!pool)
 947                 return -ENOENT;
 948
 949         ret = zpool_shrink(pool->zpool, 1, NULL);
 950
 951         zswap_pool_put(pool);
 952
 953         return ret;
 954 }
 955
 956 /*********************************
 957 * frontswap hooks
 958 **********************************/
 959 /* attempts to compress and store an single page */
 960 static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 961                                 struct page *page)
 962 {
 963         struct zswap_tree *tree = zswap_trees[type];
 964         struct zswap_entry *entry, *dupentry;
 965         struct crypto_comp *tfm;
 966         int ret;
 967         unsigned int dlen = PAGE_SIZE, len;
 968         unsigned long handle;
 969         char *buf;
 970         u8 *src, *dst;
 971         struct zswap_header *zhdr;
 972
 973         if (!zswap_enabled || !tree) {
 974                 ret = -ENODEV;
 975                 goto reject;
 976         }
 977
 978         /* reclaim space if needed */
 979         if (zswap_is_full()) {
 980                 zswap_pool_limit_hit++;
 981                 if (zswap_shrink()) {
 982                         zswap_reject_reclaim_fail++;
 983                         ret = -ENOMEM;
 984                         goto reject;
 985                 }
 986         }
 987
 988         /* allocate entry */
 989         entry = zswap_entry_cache_alloc(GFP_KERNEL);
 990         if (!entry) {
 991                 zswap_reject_kmemcache_fail++;
 992                 ret = -ENOMEM;
 993                 goto reject;
 994         }
 995
 996         /* if entry is successfully added, it keeps the reference */
 997         entry->pool = zswap_pool_current_get();
 998         if (!entry->pool) {
 999                 ret = -EINVAL;
1000                 goto freepage;
1001         }
1002
1003         /* compress */
1004         dst = get_cpu_var(zswap_dstmem);
1005         tfm = *get_cpu_ptr(entry->pool->tfm);
1006         src = kmap_atomic(page);
1007         ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
1008         kunmap_atomic(src);
1009         put_cpu_ptr(entry->pool->tfm);
1010         if (ret) {
1011                 ret = -EINVAL;
1012                 goto put_dstmem;
1013         }
1014
1015         /* store */
1016         len = dlen + sizeof(struct zswap_header);
1017         ret = zpool_malloc(entry->pool->zpool, len,
1018                            __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM,
1019                            &handle);
1020         if (ret == -ENOSPC) {
1021                 zswap_reject_compress_poor++;
1022                 goto put_dstmem;
1023         }
1024         if (ret) {
1025                 zswap_reject_alloc_fail++;
1026                 goto put_dstmem;
1027         }
1028         zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1029         zhdr->swpentry = swp_entry(type, offset);
1030         buf = (u8 *)(zhdr + 1);
1031         memcpy(buf, dst, dlen);
1032         zpool_unmap_handle(entry->pool->zpool, handle);
1033         put_cpu_var(zswap_dstmem);
1034
1035         /* populate entry */
1036         entry->offset = offset;
1037         entry->handle = handle;
1038         entry->length = dlen;
1039
1040         /* map */
1041         spin_lock(&tree->lock);
1042         do {
1043                 ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1044                 if (ret == -EEXIST) {
1045                         zswap_duplicate_entry++;
1046                         /* remove from rbtree */
1047                         zswap_rb_erase(&tree->rbroot, dupentry);
1048                         zswap_entry_put(tree, dupentry);
1049                 }
1050         } while (ret == -EEXIST);
1051         spin_unlock(&tree->lock);
1052
1053         /* update stats */
1054         atomic_inc(&zswap_stored_pages);
1055         zswap_update_total_size();
1056
1057         return 0;
1058
1059 put_dstmem:
1060         put_cpu_var(zswap_dstmem);
1061         zswap_pool_put(entry->pool);
1062 freepage:
1063         zswap_entry_cache_free(entry);
1064 reject:
1065         return ret;
1066 }
1067
1068 /*
1069  * returns 0 if the page was successfully decompressed
1070  * return -1 on entry not found or error
1071 */
1072 static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1073                                 struct page *page)
1074 {
1075         struct zswap_tree *tree = zswap_trees[type];
1076         struct zswap_entry *entry;
1077         struct crypto_comp *tfm;
1078         u8 *src, *dst;
1079         unsigned int dlen;
1080         int ret;
1081
1082         /* find */
1083         spin_lock(&tree->lock);
1084         entry = zswap_entry_find_get(&tree->rbroot, offset);
1085         if (!entry) {
1086                 /* entry was written back */
1087                 spin_unlock(&tree->lock);
1088                 return -1;
1089         }
1090         spin_unlock(&tree->lock);
1091
1092         /* decompress */
1093         dlen = PAGE_SIZE;
1094         src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle,
1095                         ZPOOL_MM_RO) + sizeof(struct zswap_header);
1096         dst = kmap_atomic(page);
1097         tfm = *get_cpu_ptr(entry->pool->tfm);
1098         ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1099         put_cpu_ptr(entry->pool->tfm);
1100         kunmap_atomic(dst);
1101         zpool_unmap_handle(entry->pool->zpool, entry->handle);
1102         BUG_ON(ret);
1103
1104         spin_lock(&tree->lock);
1105         zswap_entry_put(tree, entry);
1106         spin_unlock(&tree->lock);
1107
1108         return 0;
1109 }
1110
1111 /* frees an entry in zswap */
1112 static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1113 {
1114         struct zswap_tree *tree = zswap_trees[type];
1115         struct zswap_entry *entry;
1116
1117         /* find */
1118         spin_lock(&tree->lock);
1119         entry = zswap_rb_search(&tree->rbroot, offset);
1120         if (!entry) {
1121                 /* entry was written back */
1122                 spin_unlock(&tree->lock);
1123                 return;
1124         }
1125
1126         /* remove from rbtree */
1127         zswap_rb_erase(&tree->rbroot, entry);
1128
1129         /* drop the initial reference from entry creation */
1130         zswap_entry_put(tree, entry);
1131
1132         spin_unlock(&tree->lock);
1133 }
1134
1135 /* frees all zswap entries for the given swap type */
1136 static void zswap_frontswap_invalidate_area(unsigned type)
1137 {
1138         struct zswap_tree *tree = zswap_trees[type];
1139         struct zswap_entry *entry, *n;
1140
1141         if (!tree)
1142                 return;
1143
1144         /* walk the tree and free everything */
1145         spin_lock(&tree->lock);
1146         rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1147                 zswap_free_entry(entry);
1148         tree->rbroot = RB_ROOT;
1149         spin_unlock(&tree->lock);
1150         kfree(tree);
1151         zswap_trees[type] = NULL;
1152 }
1153
1154 static void zswap_frontswap_init(unsigned type)
1155 {
1156         struct zswap_tree *tree;
1157
1158         tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1159         if (!tree) {
1160                 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1161                 return;
1162         }
1163
1164         tree->rbroot = RB_ROOT;
1165         spin_lock_init(&tree->lock);
1166         zswap_trees[type] = tree;
1167 }
1168
1169 static struct frontswap_ops zswap_frontswap_ops = {
1170         .store = zswap_frontswap_store,
1171         .load = zswap_frontswap_load,
1172         .invalidate_page = zswap_frontswap_invalidate_page,
1173         .invalidate_area = zswap_frontswap_invalidate_area,
1174         .init = zswap_frontswap_init
1175 };
1176
1177 /*********************************
1178 * debugfs functions
1179 **********************************/
1180 #ifdef CONFIG_DEBUG_FS
1181 #include <linux/debugfs.h>
1182
1183 static struct dentry *zswap_debugfs_root;
1184
1185 static int __init zswap_debugfs_init(void)
1186 {
1187         if (!debugfs_initialized())
1188                 return -ENODEV;
1189
1190         zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1191         if (!zswap_debugfs_root)
1192                 return -ENOMEM;
1193
1194         debugfs_create_u64("pool_limit_hit", S_IRUGO,
1195                         zswap_debugfs_root, &zswap_pool_limit_hit);
1196         debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
1197                         zswap_debugfs_root, &zswap_reject_reclaim_fail);
1198         debugfs_create_u64("reject_alloc_fail", S_IRUGO,
1199                         zswap_debugfs_root, &zswap_reject_alloc_fail);
1200         debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
1201                         zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1202         debugfs_create_u64("reject_compress_poor", S_IRUGO,
1203                         zswap_debugfs_root, &zswap_reject_compress_poor);
1204         debugfs_create_u64("written_back_pages", S_IRUGO,
1205                         zswap_debugfs_root, &zswap_written_back_pages);
1206         debugfs_create_u64("duplicate_entry", S_IRUGO,
1207                         zswap_debugfs_root, &zswap_duplicate_entry);
1208         debugfs_create_u64("pool_total_size", S_IRUGO,
1209                         zswap_debugfs_root, &zswap_pool_total_size);
1210         debugfs_create_atomic_t("stored_pages", S_IRUGO,
1211                         zswap_debugfs_root, &zswap_stored_pages);
1212
1213         return 0;
1214 }
1215
1216 static void __exit zswap_debugfs_exit(void)
1217 {
1218         debugfs_remove_recursive(zswap_debugfs_root);
1219 }
1220 #else
1221 static int __init zswap_debugfs_init(void)
1222 {
1223         return 0;
1224 }
1225
1226 static void __exit zswap_debugfs_exit(void) { }
1227 #endif
1228
1229 /*********************************
1230 * module init and exit
1231 **********************************/
1232 static int __init init_zswap(void)
1233 {
1234         struct zswap_pool *pool;
1235         int ret;
1236
1237         zswap_init_started = true;
1238
1239         if (zswap_entry_cache_create()) {
1240                 pr_err("entry cache creation failed\n");
1241                 goto cache_fail;
1242         }
1243
1244         ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1245                                 zswap_dstmem_prepare, zswap_dstmem_dead);
1246         if (ret) {
1247                 pr_err("dstmem alloc failed\n");
1248                 goto dstmem_fail;
1249         }
1250
1251         ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1252                                       "mm/zswap_pool:prepare",
1253                                       zswap_cpu_comp_prepare,
1254                                       zswap_cpu_comp_dead);
1255         if (ret)
1256                 goto hp_fail;
1257
1258         pool = __zswap_pool_create_fallback();
1259         if (pool) {
1260                 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1261                         zpool_get_type(pool->zpool));
1262                 list_add(&pool->list, &zswap_pools);
1263                 zswap_has_pool = true;
1264         } else {
1265                 pr_err("pool creation failed\n");
1266                 zswap_enabled = false;
1267         }
1268
1269         frontswap_register_ops(&zswap_frontswap_ops);
1270         if (zswap_debugfs_init())
1271                 pr_warn("debugfs initialization failed\n");
1272         return 0;
1273
1274 hp_fail:
1275         cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1276 dstmem_fail:
1277         zswap_entry_cache_destroy();
1278 cache_fail:
1279         /* if built-in, we aren't unloaded on failure; don't allow use */
1280         zswap_init_failed = true;
1281         zswap_enabled = false;
1282         return -ENOMEM;
1283 }
1284 /* must be late so crypto has time to come up */
1285 late_initcall(init_zswap);
1286
1287 MODULE_LICENSE("GPL");
1288 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1289 MODULE_DESCRIPTION("Compressed cache for swap pages");