mm/zswap.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * zswap.c - zswap driver file
   4  *
   5  * zswap is a cache that takes pages that are in the process
   6  * of being swapped out and attempts to compress and store them in a
   7  * RAM-based memory pool.  This can result in a significant I/O reduction on
   8  * the swap device and, in the case where decompressing from RAM is faster
   9  * than reading from the swap device, can also improve workload performance.
  10  *
  11  * Copyright (C) 2012  Seth Jennings <sjenning@linux.vnet.ibm.com>
  12 */
  13
  14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16 #include <linux/module.h>
  17 #include <linux/cpu.h>
  18 #include <linux/highmem.h>
  19 #include <linux/slab.h>
  20 #include <linux/spinlock.h>
  21 #include <linux/types.h>
  22 #include <linux/atomic.h>
  23 #include <linux/rbtree.h>
  24 #include <linux/swap.h>
  25 #include <linux/crypto.h>
  26 #include <linux/scatterlist.h>
  27 #include <linux/mempool.h>
  28 #include <linux/zpool.h>
  29 #include <crypto/acompress.h>
  30 #include <linux/zswap.h>
  31 #include <linux/mm_types.h>
  32 #include <linux/page-flags.h>
  33 #include <linux/swapops.h>
  34 #include <linux/writeback.h>
  35 #include <linux/pagemap.h>
  36 #include <linux/workqueue.h>
  37
  38 #include "swap.h"
  39 #include "internal.h"
  40
  41 /*********************************
  42 * statistics
  43 **********************************/
  44 /* Total bytes used by the compressed storage */
  45 u64 zswap_pool_total_size;
  46 /* The number of compressed pages currently stored in zswap */
  47 atomic_t zswap_stored_pages = ATOMIC_INIT(0);
  48 /* The number of same-value filled pages currently stored in zswap */
  49 static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
  50
  51 /*
  52  * The statistics below are not protected from concurrent access for
  53  * performance reasons so they may not be a 100% accurate.  However,
  54  * they do provide useful information on roughly how many times a
  55  * certain event is occurring.
  56 */
  57
  58 /* Pool limit was hit (see zswap_max_pool_percent) */
  59 static u64 zswap_pool_limit_hit;
  60 /* Pages written back when pool limit was reached */
  61 static u64 zswap_written_back_pages;
  62 /* Store failed due to a reclaim failure after pool limit was reached */
  63 static u64 zswap_reject_reclaim_fail;
  64 /* Compressed page was too big for the allocator to (optimally) store */
  65 static u64 zswap_reject_compress_poor;
  66 /* Store failed because underlying allocator could not get memory */
  67 static u64 zswap_reject_alloc_fail;
  68 /* Store failed because the entry metadata could not be allocated (rare) */
  69 static u64 zswap_reject_kmemcache_fail;
  70 /* Duplicate store was encountered (rare) */
  71 static u64 zswap_duplicate_entry;
  72
  73 /* Shrinker work queue */
  74 static struct workqueue_struct *shrink_wq;
  75 /* Pool limit was hit, we need to calm down */
  76 static bool zswap_pool_reached_full;
  77
  78 /*********************************
  79 * tunables
  80 **********************************/
  81
  82 #define ZSWAP_PARAM_UNSET ""
  83
  84 static int zswap_setup(void);
  85
  86 /* Enable/disable zswap */
  87 static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);
  88 static int zswap_enabled_param_set(const char *,
  89                                    const struct kernel_param *);
  90 static const struct kernel_param_ops zswap_enabled_param_ops = {
  91         .set =          zswap_enabled_param_set,
  92         .get =          param_get_bool,
  93 };
  94 module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
  95
  96 /* Crypto compressor to use */
  97 static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
  98 static int zswap_compressor_param_set(const char *,
  99                                       const struct kernel_param *);
 100 static const struct kernel_param_ops zswap_compressor_param_ops = {
 101         .set =          zswap_compressor_param_set,
 102         .get =          param_get_charp,
 103         .free =         param_free_charp,
 104 };
 105 module_param_cb(compressor, &zswap_compressor_param_ops,
 106                 &zswap_compressor, 0644);
 107
 108 /* Compressed storage zpool to use */
 109 static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
 110 static int zswap_zpool_param_set(const char *, const struct kernel_param *);
 111 static const struct kernel_param_ops zswap_zpool_param_ops = {
 112         .set =          zswap_zpool_param_set,
 113         .get =          param_get_charp,
 114         .free =         param_free_charp,
 115 };
 116 module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
 117
 118 /* The maximum percentage of memory that the compressed pool can occupy */
 119 static unsigned int zswap_max_pool_percent = 20;
 120 module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
 121
 122 /* The threshold for accepting new pages after the max_pool_percent was hit */
 123 static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */
 124 module_param_named(accept_threshold_percent, zswap_accept_thr_percent,
 125                    uint, 0644);
 126
 127 /*
 128  * Enable/disable handling same-value filled pages (enabled by default).
 129  * If disabled every page is considered non-same-value filled.
 130  */
 131 static bool zswap_same_filled_pages_enabled = true;
 132 module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
 133                    bool, 0644);
 134
 135 /* Enable/disable handling non-same-value filled pages (enabled by default) */
 136 static bool zswap_non_same_filled_pages_enabled = true;
 137 module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled,
 138                    bool, 0644);
 139
 140 static bool zswap_exclusive_loads_enabled = IS_ENABLED(
 141                 CONFIG_ZSWAP_EXCLUSIVE_LOADS_DEFAULT_ON);
 142 module_param_named(exclusive_loads, zswap_exclusive_loads_enabled, bool, 0644);
 143
 144 /* Number of zpools in zswap_pool (empirically determined for scalability) */
 145 #define ZSWAP_NR_ZPOOLS 32
 146
 147 /*********************************
 148 * data structures
 149 **********************************/
 150
 151 struct crypto_acomp_ctx {
 152         struct crypto_acomp *acomp;
 153         struct acomp_req *req;
 154         struct crypto_wait wait;
 155         u8 *dstmem;
 156         struct mutex *mutex;
 157 };
 158
 159 /*
 160  * The lock ordering is zswap_tree.lock -> zswap_pool.lru_lock.
 161  * The only case where lru_lock is not acquired while holding tree.lock is
 162  * when a zswap_entry is taken off the lru for writeback, in that case it
 163  * needs to be verified that it's still valid in the tree.
 164  */
 165 struct zswap_pool {
 166         struct zpool *zpools[ZSWAP_NR_ZPOOLS];
 167         struct crypto_acomp_ctx __percpu *acomp_ctx;
 168         struct kref kref;
 169         struct list_head list;
 170         struct work_struct release_work;
 171         struct work_struct shrink_work;
 172         struct hlist_node node;
 173         char tfm_name[CRYPTO_MAX_ALG_NAME];
 174         struct list_head lru;
 175         spinlock_t lru_lock;
 176 };
 177
 178 /*
 179  * struct zswap_entry
 180  *
 181  * This structure contains the metadata for tracking a single compressed
 182  * page within zswap.
 183  *
 184  * rbnode - links the entry into red-black tree for the appropriate swap type
 185  * swpentry - associated swap entry, the offset indexes into the red-black tree
 186  * refcount - the number of outstanding reference to the entry. This is needed
 187  *            to protect against premature freeing of the entry by code
 188  *            concurrent calls to load, invalidate, and writeback.  The lock
 189  *            for the zswap_tree structure that contains the entry must
 190  *            be held while changing the refcount.  Since the lock must
 191  *            be held, there is no reason to also make refcount atomic.
 192  * length - the length in bytes of the compressed page data.  Needed during
 193  *          decompression. For a same value filled page length is 0, and both
 194  *          pool and lru are invalid and must be ignored.
 195  * pool - the zswap_pool the entry's data is in
 196  * handle - zpool allocation handle that stores the compressed page data
 197  * value - value of the same-value filled pages which have same content
 198  * objcg - the obj_cgroup that the compressed memory is charged to
 199  * lru - handle to the pool's lru used to evict pages.
 200  */
 201 struct zswap_entry {
 202         struct rb_node rbnode;
 203         swp_entry_t swpentry;
 204         int refcount;
 205         unsigned int length;
 206         struct zswap_pool *pool;
 207         union {
 208                 unsigned long handle;
 209                 unsigned long value;
 210         };
 211         struct obj_cgroup *objcg;
 212         struct list_head lru;
 213 };
 214
 215 /*
 216  * The tree lock in the zswap_tree struct protects a few things:
 217  * - the rbtree
 218  * - the refcount field of each entry in the tree
 219  */
 220 struct zswap_tree {
 221         struct rb_root rbroot;
 222         spinlock_t lock;
 223 };
 224
 225 static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
 226
 227 /* RCU-protected iteration */
 228 static LIST_HEAD(zswap_pools);
 229 /* protects zswap_pools list modification */
 230 static DEFINE_SPINLOCK(zswap_pools_lock);
 231 /* pool counter to provide unique names to zpool */
 232 static atomic_t zswap_pools_count = ATOMIC_INIT(0);
 233
 234 enum zswap_init_type {
 235         ZSWAP_UNINIT,
 236         ZSWAP_INIT_SUCCEED,
 237         ZSWAP_INIT_FAILED
 238 };
 239
 240 static enum zswap_init_type zswap_init_state;
 241
 242 /* used to ensure the integrity of initialization */
 243 static DEFINE_MUTEX(zswap_init_lock);
 244
 245 /* init completed, but couldn't create the initial pool */
 246 static bool zswap_has_pool;
 247
 248 /*********************************
 249 * helpers and fwd declarations
 250 **********************************/
 251
 252 #define zswap_pool_debug(msg, p)                                \
 253         pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,         \
 254                  zpool_get_type((p)->zpools[0]))
 255
 256 static int zswap_writeback_entry(struct zswap_entry *entry,
 257                                  struct zswap_tree *tree);
 258 static int zswap_pool_get(struct zswap_pool *pool);
 259 static void zswap_pool_put(struct zswap_pool *pool);
 260
 261 static bool zswap_is_full(void)
 262 {
 263         return totalram_pages() * zswap_max_pool_percent / 100 <
 264                         DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
 265 }
 266
 267 static bool zswap_can_accept(void)
 268 {
 269         return totalram_pages() * zswap_accept_thr_percent / 100 *
 270                                 zswap_max_pool_percent / 100 >
 271                         DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
 272 }
 273
 274 static void zswap_update_total_size(void)
 275 {
 276         struct zswap_pool *pool;
 277         u64 total = 0;
 278         int i;
 279
 280         rcu_read_lock();
 281
 282         list_for_each_entry_rcu(pool, &zswap_pools, list)
 283                 for (i = 0; i < ZSWAP_NR_ZPOOLS; i++)
 284                         total += zpool_get_total_size(pool->zpools[i]);
 285
 286         rcu_read_unlock();
 287
 288         zswap_pool_total_size = total;
 289 }
 290
 291 /*********************************
 292 * zswap entry functions
 293 **********************************/
 294 static struct kmem_cache *zswap_entry_cache;
 295
 296 static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
 297 {
 298         struct zswap_entry *entry;
 299         entry = kmem_cache_alloc(zswap_entry_cache, gfp);
 300         if (!entry)
 301                 return NULL;
 302         entry->refcount = 1;
 303         RB_CLEAR_NODE(&entry->rbnode);
 304         return entry;
 305 }
 306
 307 static void zswap_entry_cache_free(struct zswap_entry *entry)
 308 {
 309         kmem_cache_free(zswap_entry_cache, entry);
 310 }
 311
 312 /*********************************
 313 * rbtree functions
 314 **********************************/
 315 static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
 316 {
 317         struct rb_node *node = root->rb_node;
 318         struct zswap_entry *entry;
 319         pgoff_t entry_offset;
 320
 321         while (node) {
 322                 entry = rb_entry(node, struct zswap_entry, rbnode);
 323                 entry_offset = swp_offset(entry->swpentry);
 324                 if (entry_offset > offset)
 325                         node = node->rb_left;
 326                 else if (entry_offset < offset)
 327                         node = node->rb_right;
 328                 else
 329                         return entry;
 330         }
 331         return NULL;
 332 }
 333
 334 /*
 335  * In the case that a entry with the same offset is found, a pointer to
 336  * the existing entry is stored in dupentry and the function returns -EEXIST
 337  */
 338 static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
 339                         struct zswap_entry **dupentry)
 340 {
 341         struct rb_node **link = &root->rb_node, *parent = NULL;
 342         struct zswap_entry *myentry;
 343         pgoff_t myentry_offset, entry_offset = swp_offset(entry->swpentry);
 344
 345         while (*link) {
 346                 parent = *link;
 347                 myentry = rb_entry(parent, struct zswap_entry, rbnode);
 348                 myentry_offset = swp_offset(myentry->swpentry);
 349                 if (myentry_offset > entry_offset)
 350                         link = &(*link)->rb_left;
 351                 else if (myentry_offset < entry_offset)
 352                         link = &(*link)->rb_right;
 353                 else {
 354                         *dupentry = myentry;
 355                         return -EEXIST;
 356                 }
 357         }
 358         rb_link_node(&entry->rbnode, parent, link);
 359         rb_insert_color(&entry->rbnode, root);
 360         return 0;
 361 }
 362
 363 static bool zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
 364 {
 365         if (!RB_EMPTY_NODE(&entry->rbnode)) {
 366                 rb_erase(&entry->rbnode, root);
 367                 RB_CLEAR_NODE(&entry->rbnode);
 368                 return true;
 369         }
 370         return false;
 371 }
 372
 373 static struct zpool *zswap_find_zpool(struct zswap_entry *entry)
 374 {
 375         int i = 0;
 376
 377         if (ZSWAP_NR_ZPOOLS > 1)
 378                 i = hash_ptr(entry, ilog2(ZSWAP_NR_ZPOOLS));
 379
 380         return entry->pool->zpools[i];
 381 }
 382
 383 /*
 384  * Carries out the common pattern of freeing and entry's zpool allocation,
 385  * freeing the entry itself, and decrementing the number of stored pages.
 386  */
 387 static void zswap_free_entry(struct zswap_entry *entry)
 388 {
 389         if (entry->objcg) {
 390                 obj_cgroup_uncharge_zswap(entry->objcg, entry->length);
 391                 obj_cgroup_put(entry->objcg);
 392         }
 393         if (!entry->length)
 394                 atomic_dec(&zswap_same_filled_pages);
 395         else {
 396                 spin_lock(&entry->pool->lru_lock);
 397                 list_del(&entry->lru);
 398                 spin_unlock(&entry->pool->lru_lock);
 399                 zpool_free(zswap_find_zpool(entry), entry->handle);
 400                 zswap_pool_put(entry->pool);
 401         }
 402         zswap_entry_cache_free(entry);
 403         atomic_dec(&zswap_stored_pages);
 404         zswap_update_total_size();
 405 }
 406
 407 /* caller must hold the tree lock */
 408 static void zswap_entry_get(struct zswap_entry *entry)
 409 {
 410         entry->refcount++;
 411 }
 412
 413 /* caller must hold the tree lock
 414 * remove from the tree and free it, if nobody reference the entry
 415 */
 416 static void zswap_entry_put(struct zswap_tree *tree,
 417                         struct zswap_entry *entry)
 418 {
 419         int refcount = --entry->refcount;
 420
 421         WARN_ON_ONCE(refcount < 0);
 422         if (refcount == 0) {
 423                 WARN_ON_ONCE(!RB_EMPTY_NODE(&entry->rbnode));
 424                 zswap_free_entry(entry);
 425         }
 426 }
 427
 428 /* caller must hold the tree lock */
 429 static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
 430                                 pgoff_t offset)
 431 {
 432         struct zswap_entry *entry;
 433
 434         entry = zswap_rb_search(root, offset);
 435         if (entry)
 436                 zswap_entry_get(entry);
 437
 438         return entry;
 439 }
 440
 441 /*********************************
 442 * per-cpu code
 443 **********************************/
 444 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
 445 /*
 446  * If users dynamically change the zpool type and compressor at runtime, i.e.
 447  * zswap is running, zswap can have more than one zpool on one cpu, but they
 448  * are sharing dtsmem. So we need this mutex to be per-cpu.
 449  */
 450 static DEFINE_PER_CPU(struct mutex *, zswap_mutex);
 451
 452 static int zswap_dstmem_prepare(unsigned int cpu)
 453 {
 454         struct mutex *mutex;
 455         u8 *dst;
 456
 457         dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
 458         if (!dst)
 459                 return -ENOMEM;
 460
 461         mutex = kmalloc_node(sizeof(*mutex), GFP_KERNEL, cpu_to_node(cpu));
 462         if (!mutex) {
 463                 kfree(dst);
 464                 return -ENOMEM;
 465         }
 466
 467         mutex_init(mutex);
 468         per_cpu(zswap_dstmem, cpu) = dst;
 469         per_cpu(zswap_mutex, cpu) = mutex;
 470         return 0;
 471 }
 472
 473 static int zswap_dstmem_dead(unsigned int cpu)
 474 {
 475         struct mutex *mutex;
 476         u8 *dst;
 477
 478         mutex = per_cpu(zswap_mutex, cpu);
 479         kfree(mutex);
 480         per_cpu(zswap_mutex, cpu) = NULL;
 481
 482         dst = per_cpu(zswap_dstmem, cpu);
 483         kfree(dst);
 484         per_cpu(zswap_dstmem, cpu) = NULL;
 485
 486         return 0;
 487 }
 488
 489 static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 490 {
 491         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 492         struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
 493         struct crypto_acomp *acomp;
 494         struct acomp_req *req;
 495
 496         acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
 497         if (IS_ERR(acomp)) {
 498                 pr_err("could not alloc crypto acomp %s : %ld\n",
 499                                 pool->tfm_name, PTR_ERR(acomp));
 500                 return PTR_ERR(acomp);
 501         }
 502         acomp_ctx->acomp = acomp;
 503
 504         req = acomp_request_alloc(acomp_ctx->acomp);
 505         if (!req) {
 506                 pr_err("could not alloc crypto acomp_request %s\n",
 507                        pool->tfm_name);
 508                 crypto_free_acomp(acomp_ctx->acomp);
 509                 return -ENOMEM;
 510         }
 511         acomp_ctx->req = req;
 512
 513         crypto_init_wait(&acomp_ctx->wait);
 514         /*
 515          * if the backend of acomp is async zip, crypto_req_done() will wakeup
 516          * crypto_wait_req(); if the backend of acomp is scomp, the callback
 517          * won't be called, crypto_wait_req() will return without blocking.
 518          */
 519         acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
 520                                    crypto_req_done, &acomp_ctx->wait);
 521
 522         acomp_ctx->mutex = per_cpu(zswap_mutex, cpu);
 523         acomp_ctx->dstmem = per_cpu(zswap_dstmem, cpu);
 524
 525         return 0;
 526 }
 527
 528 static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 529 {
 530         struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 531         struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
 532
 533         if (!IS_ERR_OR_NULL(acomp_ctx)) {
 534                 if (!IS_ERR_OR_NULL(acomp_ctx->req))
 535                         acomp_request_free(acomp_ctx->req);
 536                 if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
 537                         crypto_free_acomp(acomp_ctx->acomp);
 538         }
 539
 540         return 0;
 541 }
 542
 543 /*********************************
 544 * pool functions
 545 **********************************/
 546
 547 static struct zswap_pool *__zswap_pool_current(void)
 548 {
 549         struct zswap_pool *pool;
 550
 551         pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
 552         WARN_ONCE(!pool && zswap_has_pool,
 553                   "%s: no page storage pool!\n", __func__);
 554
 555         return pool;
 556 }
 557
 558 static struct zswap_pool *zswap_pool_current(void)
 559 {
 560         assert_spin_locked(&zswap_pools_lock);
 561
 562         return __zswap_pool_current();
 563 }
 564
 565 static struct zswap_pool *zswap_pool_current_get(void)
 566 {
 567         struct zswap_pool *pool;
 568
 569         rcu_read_lock();
 570
 571         pool = __zswap_pool_current();
 572         if (!zswap_pool_get(pool))
 573                 pool = NULL;
 574
 575         rcu_read_unlock();
 576
 577         return pool;
 578 }
 579
 580 static struct zswap_pool *zswap_pool_last_get(void)
 581 {
 582         struct zswap_pool *pool, *last = NULL;
 583
 584         rcu_read_lock();
 585
 586         list_for_each_entry_rcu(pool, &zswap_pools, list)
 587                 last = pool;
 588         WARN_ONCE(!last && zswap_has_pool,
 589                   "%s: no page storage pool!\n", __func__);
 590         if (!zswap_pool_get(last))
 591                 last = NULL;
 592
 593         rcu_read_unlock();
 594
 595         return last;
 596 }
 597
 598 /* type and compressor must be null-terminated */
 599 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
 600 {
 601         struct zswap_pool *pool;
 602
 603         assert_spin_locked(&zswap_pools_lock);
 604
 605         list_for_each_entry_rcu(pool, &zswap_pools, list) {
 606                 if (strcmp(pool->tfm_name, compressor))
 607                         continue;
 608                 /* all zpools share the same type */
 609                 if (strcmp(zpool_get_type(pool->zpools[0]), type))
 610                         continue;
 611                 /* if we can't get it, it's about to be destroyed */
 612                 if (!zswap_pool_get(pool))
 613                         continue;
 614                 return pool;
 615         }
 616
 617         return NULL;
 618 }
 619
 620 /*
 621  * If the entry is still valid in the tree, drop the initial ref and remove it
 622  * from the tree. This function must be called with an additional ref held,
 623  * otherwise it may race with another invalidation freeing the entry.
 624  */
 625 static void zswap_invalidate_entry(struct zswap_tree *tree,
 626                                    struct zswap_entry *entry)
 627 {
 628         if (zswap_rb_erase(&tree->rbroot, entry))
 629                 zswap_entry_put(tree, entry);
 630 }
 631
 632 static int zswap_reclaim_entry(struct zswap_pool *pool)
 633 {
 634         struct zswap_entry *entry;
 635         struct zswap_tree *tree;
 636         pgoff_t swpoffset;
 637         int ret;
 638
 639         /* Get an entry off the LRU */
 640         spin_lock(&pool->lru_lock);
 641         if (list_empty(&pool->lru)) {
 642                 spin_unlock(&pool->lru_lock);
 643                 return -EINVAL;
 644         }
 645         entry = list_last_entry(&pool->lru, struct zswap_entry, lru);
 646         list_del_init(&entry->lru);
 647         /*
 648          * Once the lru lock is dropped, the entry might get freed. The
 649          * swpoffset is copied to the stack, and entry isn't deref'd again
 650          * until the entry is verified to still be alive in the tree.
 651          */
 652         swpoffset = swp_offset(entry->swpentry);
 653         tree = zswap_trees[swp_type(entry->swpentry)];
 654         spin_unlock(&pool->lru_lock);
 655
 656         /* Check for invalidate() race */
 657         spin_lock(&tree->lock);
 658         if (entry != zswap_rb_search(&tree->rbroot, swpoffset)) {
 659                 ret = -EAGAIN;
 660                 goto unlock;
 661         }
 662         /* Hold a reference to prevent a free during writeback */
 663         zswap_entry_get(entry);
 664         spin_unlock(&tree->lock);
 665
 666         ret = zswap_writeback_entry(entry, tree);
 667
 668         spin_lock(&tree->lock);
 669         if (ret) {
 670                 /* Writeback failed, put entry back on LRU */
 671                 spin_lock(&pool->lru_lock);
 672                 list_move(&entry->lru, &pool->lru);
 673                 spin_unlock(&pool->lru_lock);
 674                 goto put_unlock;
 675         }
 676
 677         /*
 678          * Writeback started successfully, the page now belongs to the
 679          * swapcache. Drop the entry from zswap - unless invalidate already
 680          * took it out while we had the tree->lock released for IO.
 681          */
 682         zswap_invalidate_entry(tree, entry);
 683
 684 put_unlock:
 685         /* Drop local reference */
 686         zswap_entry_put(tree, entry);
 687 unlock:
 688         spin_unlock(&tree->lock);
 689         return ret ? -EAGAIN : 0;
 690 }
 691
 692 static void shrink_worker(struct work_struct *w)
 693 {
 694         struct zswap_pool *pool = container_of(w, typeof(*pool),
 695                                                 shrink_work);
 696         int ret, failures = 0;
 697
 698         do {
 699                 ret = zswap_reclaim_entry(pool);
 700                 if (ret) {
 701                         zswap_reject_reclaim_fail++;
 702                         if (ret != -EAGAIN)
 703                                 break;
 704                         if (++failures == MAX_RECLAIM_RETRIES)
 705                                 break;
 706                 }
 707                 cond_resched();
 708         } while (!zswap_can_accept());
 709         zswap_pool_put(pool);
 710 }
 711
 712 static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
 713 {
 714         int i;
 715         struct zswap_pool *pool;
 716         char name[38]; /* 'zswap' + 32 char (max) num + \0 */
 717         gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
 718         int ret;
 719
 720         if (!zswap_has_pool) {
 721                 /* if either are unset, pool initialization failed, and we
 722                  * need both params to be set correctly before trying to
 723                  * create a pool.
 724                  */
 725                 if (!strcmp(type, ZSWAP_PARAM_UNSET))
 726                         return NULL;
 727                 if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
 728                         return NULL;
 729         }
 730
 731         pool = kzalloc(sizeof(*pool), GFP_KERNEL);
 732         if (!pool)
 733                 return NULL;
 734
 735         for (i = 0; i < ZSWAP_NR_ZPOOLS; i++) {
 736                 /* unique name for each pool specifically required by zsmalloc */
 737                 snprintf(name, 38, "zswap%x",
 738                          atomic_inc_return(&zswap_pools_count));
 739
 740                 pool->zpools[i] = zpool_create_pool(type, name, gfp);
 741                 if (!pool->zpools[i]) {
 742                         pr_err("%s zpool not available\n", type);
 743                         goto error;
 744                 }
 745         }
 746         pr_debug("using %s zpool\n", zpool_get_type(pool->zpools[0]));
 747
 748         strscpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
 749
 750         pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx);
 751         if (!pool->acomp_ctx) {
 752                 pr_err("percpu alloc failed\n");
 753                 goto error;
 754         }
 755
 756         ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
 757                                        &pool->node);
 758         if (ret)
 759                 goto error;
 760         pr_debug("using %s compressor\n", pool->tfm_name);
 761
 762         /* being the current pool takes 1 ref; this func expects the
 763          * caller to always add the new pool as the current pool
 764          */
 765         kref_init(&pool->kref);
 766         INIT_LIST_HEAD(&pool->list);
 767         INIT_LIST_HEAD(&pool->lru);
 768         spin_lock_init(&pool->lru_lock);
 769         INIT_WORK(&pool->shrink_work, shrink_worker);
 770
 771         zswap_pool_debug("created", pool);
 772
 773         return pool;
 774
 775 error:
 776         if (pool->acomp_ctx)
 777                 free_percpu(pool->acomp_ctx);
 778         while (i--)
 779                 zpool_destroy_pool(pool->zpools[i]);
 780         kfree(pool);
 781         return NULL;
 782 }
 783
 784 static struct zswap_pool *__zswap_pool_create_fallback(void)
 785 {
 786         bool has_comp, has_zpool;
 787
 788         has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
 789         if (!has_comp && strcmp(zswap_compressor,
 790                                 CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
 791                 pr_err("compressor %s not available, using default %s\n",
 792                        zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
 793                 param_free_charp(&zswap_compressor);
 794                 zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
 795                 has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
 796         }
 797         if (!has_comp) {
 798                 pr_err("default compressor %s not available\n",
 799                        zswap_compressor);
 800                 param_free_charp(&zswap_compressor);
 801                 zswap_compressor = ZSWAP_PARAM_UNSET;
 802         }
 803
 804         has_zpool = zpool_has_pool(zswap_zpool_type);
 805         if (!has_zpool && strcmp(zswap_zpool_type,
 806                                  CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
 807                 pr_err("zpool %s not available, using default %s\n",
 808                        zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
 809                 param_free_charp(&zswap_zpool_type);
 810                 zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
 811                 has_zpool = zpool_has_pool(zswap_zpool_type);
 812         }
 813         if (!has_zpool) {
 814                 pr_err("default zpool %s not available\n",
 815                        zswap_zpool_type);
 816                 param_free_charp(&zswap_zpool_type);
 817                 zswap_zpool_type = ZSWAP_PARAM_UNSET;
 818         }
 819
 820         if (!has_comp || !has_zpool)
 821                 return NULL;
 822
 823         return zswap_pool_create(zswap_zpool_type, zswap_compressor);
 824 }
 825
 826 static void zswap_pool_destroy(struct zswap_pool *pool)
 827 {
 828         int i;
 829
 830         zswap_pool_debug("destroying", pool);
 831
 832         cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
 833         free_percpu(pool->acomp_ctx);
 834         for (i = 0; i < ZSWAP_NR_ZPOOLS; i++)
 835                 zpool_destroy_pool(pool->zpools[i]);
 836         kfree(pool);
 837 }
 838
 839 static int __must_check zswap_pool_get(struct zswap_pool *pool)
 840 {
 841         if (!pool)
 842                 return 0;
 843
 844         return kref_get_unless_zero(&pool->kref);
 845 }
 846
 847 static void __zswap_pool_release(struct work_struct *work)
 848 {
 849         struct zswap_pool *pool = container_of(work, typeof(*pool),
 850                                                 release_work);
 851
 852         synchronize_rcu();
 853
 854         /* nobody should have been able to get a kref... */
 855         WARN_ON(kref_get_unless_zero(&pool->kref));
 856
 857         /* pool is now off zswap_pools list and has no references. */
 858         zswap_pool_destroy(pool);
 859 }
 860
 861 static void __zswap_pool_empty(struct kref *kref)
 862 {
 863         struct zswap_pool *pool;
 864
 865         pool = container_of(kref, typeof(*pool), kref);
 866
 867         spin_lock(&zswap_pools_lock);
 868
 869         WARN_ON(pool == zswap_pool_current());
 870
 871         list_del_rcu(&pool->list);
 872
 873         INIT_WORK(&pool->release_work, __zswap_pool_release);
 874         schedule_work(&pool->release_work);
 875
 876         spin_unlock(&zswap_pools_lock);
 877 }
 878
 879 static void zswap_pool_put(struct zswap_pool *pool)
 880 {
 881         kref_put(&pool->kref, __zswap_pool_empty);
 882 }
 883
 884 /*********************************
 885 * param callbacks
 886 **********************************/
 887
 888 static bool zswap_pool_changed(const char *s, const struct kernel_param *kp)
 889 {
 890         /* no change required */
 891         if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
 892                 return false;
 893         return true;
 894 }
 895
 896 /* val must be a null-terminated string */
 897 static int __zswap_param_set(const char *val, const struct kernel_param *kp,
 898                              char *type, char *compressor)
 899 {
 900         struct zswap_pool *pool, *put_pool = NULL;
 901         char *s = strstrip((char *)val);
 902         int ret = 0;
 903         bool new_pool = false;
 904
 905         mutex_lock(&zswap_init_lock);
 906         switch (zswap_init_state) {
 907         case ZSWAP_UNINIT:
 908                 /* if this is load-time (pre-init) param setting,
 909                  * don't create a pool; that's done during init.
 910                  */
 911                 ret = param_set_charp(s, kp);
 912                 break;
 913         case ZSWAP_INIT_SUCCEED:
 914                 new_pool = zswap_pool_changed(s, kp);
 915                 break;
 916         case ZSWAP_INIT_FAILED:
 917                 pr_err("can't set param, initialization failed\n");
 918                 ret = -ENODEV;
 919         }
 920         mutex_unlock(&zswap_init_lock);
 921
 922         /* no need to create a new pool, return directly */
 923         if (!new_pool)
 924                 return ret;
 925
 926         if (!type) {
 927                 if (!zpool_has_pool(s)) {
 928                         pr_err("zpool %s not available\n", s);
 929                         return -ENOENT;
 930                 }
 931                 type = s;
 932         } else if (!compressor) {
 933                 if (!crypto_has_acomp(s, 0, 0)) {
 934                         pr_err("compressor %s not available\n", s);
 935                         return -ENOENT;
 936                 }
 937                 compressor = s;
 938         } else {
 939                 WARN_ON(1);
 940                 return -EINVAL;
 941         }
 942
 943         spin_lock(&zswap_pools_lock);
 944
 945         pool = zswap_pool_find_get(type, compressor);
 946         if (pool) {
 947                 zswap_pool_debug("using existing", pool);
 948                 WARN_ON(pool == zswap_pool_current());
 949                 list_del_rcu(&pool->list);
 950         }
 951
 952         spin_unlock(&zswap_pools_lock);
 953
 954         if (!pool)
 955                 pool = zswap_pool_create(type, compressor);
 956
 957         if (pool)
 958                 ret = param_set_charp(s, kp);
 959         else
 960                 ret = -EINVAL;
 961
 962         spin_lock(&zswap_pools_lock);
 963
 964         if (!ret) {
 965                 put_pool = zswap_pool_current();
 966                 list_add_rcu(&pool->list, &zswap_pools);
 967                 zswap_has_pool = true;
 968         } else if (pool) {
 969                 /* add the possibly pre-existing pool to the end of the pools
 970                  * list; if it's new (and empty) then it'll be removed and
 971                  * destroyed by the put after we drop the lock
 972                  */
 973                 list_add_tail_rcu(&pool->list, &zswap_pools);
 974                 put_pool = pool;
 975         }
 976
 977         spin_unlock(&zswap_pools_lock);
 978
 979         if (!zswap_has_pool && !pool) {
 980                 /* if initial pool creation failed, and this pool creation also
 981                  * failed, maybe both compressor and zpool params were bad.
 982                  * Allow changing this param, so pool creation will succeed
 983                  * when the other param is changed. We already verified this
 984                  * param is ok in the zpool_has_pool() or crypto_has_acomp()
 985                  * checks above.
 986                  */
 987                 ret = param_set_charp(s, kp);
 988         }
 989
 990         /* drop the ref from either the old current pool,
 991          * or the new pool we failed to add
 992          */
 993         if (put_pool)
 994                 zswap_pool_put(put_pool);
 995
 996         return ret;
 997 }
 998
 999 static int zswap_compressor_param_set(const char *val,
1000                                       const struct kernel_param *kp)
1001 {
1002         return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
1003 }
1004
1005 static int zswap_zpool_param_set(const char *val,
1006                                  const struct kernel_param *kp)
1007 {
1008         return __zswap_param_set(val, kp, NULL, zswap_compressor);
1009 }
1010
1011 static int zswap_enabled_param_set(const char *val,
1012                                    const struct kernel_param *kp)
1013 {
1014         int ret = -ENODEV;
1015
1016         /* if this is load-time (pre-init) param setting, only set param. */
1017         if (system_state != SYSTEM_RUNNING)
1018                 return param_set_bool(val, kp);
1019
1020         mutex_lock(&zswap_init_lock);
1021         switch (zswap_init_state) {
1022         case ZSWAP_UNINIT:
1023                 if (zswap_setup())
1024                         break;
1025                 fallthrough;
1026         case ZSWAP_INIT_SUCCEED:
1027                 if (!zswap_has_pool)
1028                         pr_err("can't enable, no pool configured\n");
1029                 else
1030                         ret = param_set_bool(val, kp);
1031                 break;
1032         case ZSWAP_INIT_FAILED:
1033                 pr_err("can't enable, initialization failed\n");
1034         }
1035         mutex_unlock(&zswap_init_lock);
1036
1037         return ret;
1038 }
1039
1040 /*********************************
1041 * writeback code
1042 **********************************/
1043 /*
1044  * Attempts to free an entry by adding a page to the swap cache,
1045  * decompressing the entry data into the page, and issuing a
1046  * bio write to write the page back to the swap device.
1047  *
1048  * This can be thought of as a "resumed writeback" of the page
1049  * to the swap device.  We are basically resuming the same swap
1050  * writeback path that was intercepted with the zswap_store()
1051  * in the first place.  After the page has been decompressed into
1052  * the swap cache, the compressed version stored by zswap can be
1053  * freed.
1054  */
1055 static int zswap_writeback_entry(struct zswap_entry *entry,
1056                                  struct zswap_tree *tree)
1057 {
1058         swp_entry_t swpentry = entry->swpentry;
1059         struct page *page;
1060         struct scatterlist input, output;
1061         struct crypto_acomp_ctx *acomp_ctx;
1062         struct zpool *pool = zswap_find_zpool(entry);
1063         bool page_was_allocated;
1064         u8 *src, *tmp = NULL;
1065         unsigned int dlen;
1066         int ret;
1067         struct writeback_control wbc = {
1068                 .sync_mode = WB_SYNC_NONE,
1069         };
1070
1071         if (!zpool_can_sleep_mapped(pool)) {
1072                 tmp = kmalloc(PAGE_SIZE, GFP_KERNEL);
1073                 if (!tmp)
1074                         return -ENOMEM;
1075         }
1076
1077         /* try to allocate swap cache page */
1078         page = __read_swap_cache_async(swpentry, GFP_KERNEL, NULL, 0,
1079                                        &page_was_allocated);
1080         if (!page) {
1081                 ret = -ENOMEM;
1082                 goto fail;
1083         }
1084
1085         /* Found an existing page, we raced with load/swapin */
1086         if (!page_was_allocated) {
1087                 put_page(page);
1088                 ret = -EEXIST;
1089                 goto fail;
1090         }
1091
1092         /*
1093          * Page is locked, and the swapcache is now secured against
1094          * concurrent swapping to and from the slot. Verify that the
1095          * swap entry hasn't been invalidated and recycled behind our
1096          * backs (our zswap_entry reference doesn't prevent that), to
1097          * avoid overwriting a new swap page with old compressed data.
1098          */
1099         spin_lock(&tree->lock);
1100         if (zswap_rb_search(&tree->rbroot, swp_offset(entry->swpentry)) != entry) {
1101                 spin_unlock(&tree->lock);
1102                 delete_from_swap_cache(page_folio(page));
1103                 ret = -ENOMEM;
1104                 goto fail;
1105         }
1106         spin_unlock(&tree->lock);
1107
1108         /* decompress */
1109         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1110         dlen = PAGE_SIZE;
1111
1112         src = zpool_map_handle(pool, entry->handle, ZPOOL_MM_RO);
1113         if (!zpool_can_sleep_mapped(pool)) {
1114                 memcpy(tmp, src, entry->length);
1115                 src = tmp;
1116                 zpool_unmap_handle(pool, entry->handle);
1117         }
1118
1119         mutex_lock(acomp_ctx->mutex);
1120         sg_init_one(&input, src, entry->length);
1121         sg_init_table(&output, 1);
1122         sg_set_page(&output, page, PAGE_SIZE, 0);
1123         acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1124         ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1125         dlen = acomp_ctx->req->dlen;
1126         mutex_unlock(acomp_ctx->mutex);
1127
1128         if (!zpool_can_sleep_mapped(pool))
1129                 kfree(tmp);
1130         else
1131                 zpool_unmap_handle(pool, entry->handle);
1132
1133         BUG_ON(ret);
1134         BUG_ON(dlen != PAGE_SIZE);
1135
1136         /* page is up to date */
1137         SetPageUptodate(page);
1138
1139         /* move it to the tail of the inactive list after end_writeback */
1140         SetPageReclaim(page);
1141
1142         /* start writeback */
1143         __swap_writepage(page, &wbc);
1144         put_page(page);
1145         zswap_written_back_pages++;
1146
1147         return ret;
1148
1149 fail:
1150         if (!zpool_can_sleep_mapped(pool))
1151                 kfree(tmp);
1152
1153         /*
1154          * If we get here because the page is already in swapcache, a
1155          * load may be happening concurrently. It is safe and okay to
1156          * not free the entry. It is also okay to return !0.
1157          */
1158         return ret;
1159 }
1160
1161 static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
1162 {
1163         unsigned long *page;
1164         unsigned long val;
1165         unsigned int pos, last_pos = PAGE_SIZE / sizeof(*page) - 1;
1166
1167         page = (unsigned long *)ptr;
1168         val = page[0];
1169
1170         if (val != page[last_pos])
1171                 return 0;
1172
1173         for (pos = 1; pos < last_pos; pos++) {
1174                 if (val != page[pos])
1175                         return 0;
1176         }
1177
1178         *value = val;
1179
1180         return 1;
1181 }
1182
1183 static void zswap_fill_page(void *ptr, unsigned long value)
1184 {
1185         unsigned long *page;
1186
1187         page = (unsigned long *)ptr;
1188         memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
1189 }
1190
1191 bool zswap_store(struct folio *folio)
1192 {
1193         swp_entry_t swp = folio->swap;
1194         int type = swp_type(swp);
1195         pgoff_t offset = swp_offset(swp);
1196         struct page *page = &folio->page;
1197         struct zswap_tree *tree = zswap_trees[type];
1198         struct zswap_entry *entry, *dupentry;
1199         struct scatterlist input, output;
1200         struct crypto_acomp_ctx *acomp_ctx;
1201         struct obj_cgroup *objcg = NULL;
1202         struct zswap_pool *pool;
1203         struct zpool *zpool;
1204         unsigned int dlen = PAGE_SIZE;
1205         unsigned long handle, value;
1206         char *buf;
1207         u8 *src, *dst;
1208         gfp_t gfp;
1209         int ret;
1210
1211         VM_WARN_ON_ONCE(!folio_test_locked(folio));
1212         VM_WARN_ON_ONCE(!folio_test_swapcache(folio));
1213
1214         /* Large folios aren't supported */
1215         if (folio_test_large(folio))
1216                 return false;
1217
1218         if (!zswap_enabled || !tree)
1219                 return false;
1220
1221         /*
1222          * If this is a duplicate, it must be removed before attempting to store
1223          * it, otherwise, if the store fails the old page won't be removed from
1224          * the tree, and it might be written back overriding the new data.
1225          */
1226         spin_lock(&tree->lock);
1227         dupentry = zswap_rb_search(&tree->rbroot, offset);
1228         if (dupentry) {
1229                 zswap_duplicate_entry++;
1230                 zswap_invalidate_entry(tree, dupentry);
1231         }
1232         spin_unlock(&tree->lock);
1233
1234         /*
1235          * XXX: zswap reclaim does not work with cgroups yet. Without a
1236          * cgroup-aware entry LRU, we will push out entries system-wide based on
1237          * local cgroup limits.
1238          */
1239         objcg = get_obj_cgroup_from_folio(folio);
1240         if (objcg && !obj_cgroup_may_zswap(objcg))
1241                 goto reject;
1242
1243         /* reclaim space if needed */
1244         if (zswap_is_full()) {
1245                 zswap_pool_limit_hit++;
1246                 zswap_pool_reached_full = true;
1247                 goto shrink;
1248         }
1249
1250         if (zswap_pool_reached_full) {
1251                if (!zswap_can_accept())
1252                         goto shrink;
1253                 else
1254                         zswap_pool_reached_full = false;
1255         }
1256
1257         /* allocate entry */
1258         entry = zswap_entry_cache_alloc(GFP_KERNEL);
1259         if (!entry) {
1260                 zswap_reject_kmemcache_fail++;
1261                 goto reject;
1262         }
1263
1264         if (zswap_same_filled_pages_enabled) {
1265                 src = kmap_atomic(page);
1266                 if (zswap_is_page_same_filled(src, &value)) {
1267                         kunmap_atomic(src);
1268                         entry->swpentry = swp_entry(type, offset);
1269                         entry->length = 0;
1270                         entry->value = value;
1271                         atomic_inc(&zswap_same_filled_pages);
1272                         goto insert_entry;
1273                 }
1274                 kunmap_atomic(src);
1275         }
1276
1277         if (!zswap_non_same_filled_pages_enabled)
1278                 goto freepage;
1279
1280         /* if entry is successfully added, it keeps the reference */
1281         entry->pool = zswap_pool_current_get();
1282         if (!entry->pool)
1283                 goto freepage;
1284
1285         /* compress */
1286         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1287
1288         mutex_lock(acomp_ctx->mutex);
1289
1290         dst = acomp_ctx->dstmem;
1291         sg_init_table(&input, 1);
1292         sg_set_page(&input, page, PAGE_SIZE, 0);
1293
1294         /* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
1295         sg_init_one(&output, dst, PAGE_SIZE * 2);
1296         acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
1297         /*
1298          * it maybe looks a little bit silly that we send an asynchronous request,
1299          * then wait for its completion synchronously. This makes the process look
1300          * synchronous in fact.
1301          * Theoretically, acomp supports users send multiple acomp requests in one
1302          * acomp instance, then get those requests done simultaneously. but in this
1303          * case, zswap actually does store and load page by page, there is no
1304          * existing method to send the second page before the first page is done
1305          * in one thread doing zwap.
1306          * but in different threads running on different cpu, we have different
1307          * acomp instance, so multiple threads can do (de)compression in parallel.
1308          */
1309         ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
1310         dlen = acomp_ctx->req->dlen;
1311
1312         if (ret)
1313                 goto put_dstmem;
1314
1315         /* store */
1316         zpool = zswap_find_zpool(entry);
1317         gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1318         if (zpool_malloc_support_movable(zpool))
1319                 gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1320         ret = zpool_malloc(zpool, dlen, gfp, &handle);
1321         if (ret == -ENOSPC) {
1322                 zswap_reject_compress_poor++;
1323                 goto put_dstmem;
1324         }
1325         if (ret) {
1326                 zswap_reject_alloc_fail++;
1327                 goto put_dstmem;
1328         }
1329         buf = zpool_map_handle(zpool, handle, ZPOOL_MM_WO);
1330         memcpy(buf, dst, dlen);
1331         zpool_unmap_handle(zpool, handle);
1332         mutex_unlock(acomp_ctx->mutex);
1333
1334         /* populate entry */
1335         entry->swpentry = swp_entry(type, offset);
1336         entry->handle = handle;
1337         entry->length = dlen;
1338
1339 insert_entry:
1340         entry->objcg = objcg;
1341         if (objcg) {
1342                 obj_cgroup_charge_zswap(objcg, entry->length);
1343                 /* Account before objcg ref is moved to tree */
1344                 count_objcg_event(objcg, ZSWPOUT);
1345         }
1346
1347         /* map */
1348         spin_lock(&tree->lock);
1349         /*
1350          * A duplicate entry should have been removed at the beginning of this
1351          * function. Since the swap entry should be pinned, if a duplicate is
1352          * found again here it means that something went wrong in the swap
1353          * cache.
1354          */
1355         while (zswap_rb_insert(&tree->rbroot, entry, &dupentry) == -EEXIST) {
1356                 WARN_ON(1);
1357                 zswap_duplicate_entry++;
1358                 zswap_invalidate_entry(tree, dupentry);
1359         }
1360         if (entry->length) {
1361                 spin_lock(&entry->pool->lru_lock);
1362                 list_add(&entry->lru, &entry->pool->lru);
1363                 spin_unlock(&entry->pool->lru_lock);
1364         }
1365         spin_unlock(&tree->lock);
1366
1367         /* update stats */
1368         atomic_inc(&zswap_stored_pages);
1369         zswap_update_total_size();
1370         count_vm_event(ZSWPOUT);
1371
1372         return true;
1373
1374 put_dstmem:
1375         mutex_unlock(acomp_ctx->mutex);
1376         zswap_pool_put(entry->pool);
1377 freepage:
1378         zswap_entry_cache_free(entry);
1379 reject:
1380         if (objcg)
1381                 obj_cgroup_put(objcg);
1382         return false;
1383
1384 shrink:
1385         pool = zswap_pool_last_get();
1386         if (pool && !queue_work(shrink_wq, &pool->shrink_work))
1387                 zswap_pool_put(pool);
1388         goto reject;
1389 }
1390
1391 bool zswap_load(struct folio *folio)
1392 {
1393         swp_entry_t swp = folio->swap;
1394         int type = swp_type(swp);
1395         pgoff_t offset = swp_offset(swp);
1396         struct page *page = &folio->page;
1397         struct zswap_tree *tree = zswap_trees[type];
1398         struct zswap_entry *entry;
1399         struct scatterlist input, output;
1400         struct crypto_acomp_ctx *acomp_ctx;
1401         u8 *src, *dst, *tmp;
1402         struct zpool *zpool;
1403         unsigned int dlen;
1404         bool ret;
1405
1406         VM_WARN_ON_ONCE(!folio_test_locked(folio));
1407
1408         /* find */
1409         spin_lock(&tree->lock);
1410         entry = zswap_entry_find_get(&tree->rbroot, offset);
1411         if (!entry) {
1412                 spin_unlock(&tree->lock);
1413                 return false;
1414         }
1415         spin_unlock(&tree->lock);
1416
1417         if (!entry->length) {
1418                 dst = kmap_atomic(page);
1419                 zswap_fill_page(dst, entry->value);
1420                 kunmap_atomic(dst);
1421                 ret = true;
1422                 goto stats;
1423         }
1424
1425         zpool = zswap_find_zpool(entry);
1426         if (!zpool_can_sleep_mapped(zpool)) {
1427                 tmp = kmalloc(entry->length, GFP_KERNEL);
1428                 if (!tmp) {
1429                         ret = false;
1430                         goto freeentry;
1431                 }
1432         }
1433
1434         /* decompress */
1435         dlen = PAGE_SIZE;
1436         src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
1437
1438         if (!zpool_can_sleep_mapped(zpool)) {
1439                 memcpy(tmp, src, entry->length);
1440                 src = tmp;
1441                 zpool_unmap_handle(zpool, entry->handle);
1442         }
1443
1444         acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1445         mutex_lock(acomp_ctx->mutex);
1446         sg_init_one(&input, src, entry->length);
1447         sg_init_table(&output, 1);
1448         sg_set_page(&output, page, PAGE_SIZE, 0);
1449         acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1450         if (crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait))
1451                 WARN_ON(1);
1452         mutex_unlock(acomp_ctx->mutex);
1453
1454         if (zpool_can_sleep_mapped(zpool))
1455                 zpool_unmap_handle(zpool, entry->handle);
1456         else
1457                 kfree(tmp);
1458
1459         ret = true;
1460 stats:
1461         count_vm_event(ZSWPIN);
1462         if (entry->objcg)
1463                 count_objcg_event(entry->objcg, ZSWPIN);
1464 freeentry:
1465         spin_lock(&tree->lock);
1466         if (ret && zswap_exclusive_loads_enabled) {
1467                 zswap_invalidate_entry(tree, entry);
1468                 folio_mark_dirty(folio);
1469         } else if (entry->length) {
1470                 spin_lock(&entry->pool->lru_lock);
1471                 list_move(&entry->lru, &entry->pool->lru);
1472                 spin_unlock(&entry->pool->lru_lock);
1473         }
1474         zswap_entry_put(tree, entry);
1475         spin_unlock(&tree->lock);
1476
1477         return ret;
1478 }
1479
1480 void zswap_invalidate(int type, pgoff_t offset)
1481 {
1482         struct zswap_tree *tree = zswap_trees[type];
1483         struct zswap_entry *entry;
1484
1485         /* find */
1486         spin_lock(&tree->lock);
1487         entry = zswap_rb_search(&tree->rbroot, offset);
1488         if (!entry) {
1489                 /* entry was written back */
1490                 spin_unlock(&tree->lock);
1491                 return;
1492         }
1493         zswap_invalidate_entry(tree, entry);
1494         spin_unlock(&tree->lock);
1495 }
1496
1497 void zswap_swapon(int type)
1498 {
1499         struct zswap_tree *tree;
1500
1501         tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1502         if (!tree) {
1503                 pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1504                 return;
1505         }
1506
1507         tree->rbroot = RB_ROOT;
1508         spin_lock_init(&tree->lock);
1509         zswap_trees[type] = tree;
1510 }
1511
1512 void zswap_swapoff(int type)
1513 {
1514         struct zswap_tree *tree = zswap_trees[type];
1515         struct zswap_entry *entry, *n;
1516
1517         if (!tree)
1518                 return;
1519
1520         /* walk the tree and free everything */
1521         spin_lock(&tree->lock);
1522         rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1523                 zswap_free_entry(entry);
1524         tree->rbroot = RB_ROOT;
1525         spin_unlock(&tree->lock);
1526         kfree(tree);
1527         zswap_trees[type] = NULL;
1528 }
1529
1530 /*********************************
1531 * debugfs functions
1532 **********************************/
1533 #ifdef CONFIG_DEBUG_FS
1534 #include <linux/debugfs.h>
1535
1536 static struct dentry *zswap_debugfs_root;
1537
1538 static int zswap_debugfs_init(void)
1539 {
1540         if (!debugfs_initialized())
1541                 return -ENODEV;
1542
1543         zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1544
1545         debugfs_create_u64("pool_limit_hit", 0444,
1546                            zswap_debugfs_root, &zswap_pool_limit_hit);
1547         debugfs_create_u64("reject_reclaim_fail", 0444,
1548                            zswap_debugfs_root, &zswap_reject_reclaim_fail);
1549         debugfs_create_u64("reject_alloc_fail", 0444,
1550                            zswap_debugfs_root, &zswap_reject_alloc_fail);
1551         debugfs_create_u64("reject_kmemcache_fail", 0444,
1552                            zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1553         debugfs_create_u64("reject_compress_poor", 0444,
1554                            zswap_debugfs_root, &zswap_reject_compress_poor);
1555         debugfs_create_u64("written_back_pages", 0444,
1556                            zswap_debugfs_root, &zswap_written_back_pages);
1557         debugfs_create_u64("duplicate_entry", 0444,
1558                            zswap_debugfs_root, &zswap_duplicate_entry);
1559         debugfs_create_u64("pool_total_size", 0444,
1560                            zswap_debugfs_root, &zswap_pool_total_size);
1561         debugfs_create_atomic_t("stored_pages", 0444,
1562                                 zswap_debugfs_root, &zswap_stored_pages);
1563         debugfs_create_atomic_t("same_filled_pages", 0444,
1564                                 zswap_debugfs_root, &zswap_same_filled_pages);
1565
1566         return 0;
1567 }
1568 #else
1569 static int zswap_debugfs_init(void)
1570 {
1571         return 0;
1572 }
1573 #endif
1574
1575 /*********************************
1576 * module init and exit
1577 **********************************/
1578 static int zswap_setup(void)
1579 {
1580         struct zswap_pool *pool;
1581         int ret;
1582
1583         zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
1584         if (!zswap_entry_cache) {
1585                 pr_err("entry cache creation failed\n");
1586                 goto cache_fail;
1587         }
1588
1589         ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1590                                 zswap_dstmem_prepare, zswap_dstmem_dead);
1591         if (ret) {
1592                 pr_err("dstmem alloc failed\n");
1593                 goto dstmem_fail;
1594         }
1595
1596         ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1597                                       "mm/zswap_pool:prepare",
1598                                       zswap_cpu_comp_prepare,
1599                                       zswap_cpu_comp_dead);
1600         if (ret)
1601                 goto hp_fail;
1602
1603         pool = __zswap_pool_create_fallback();
1604         if (pool) {
1605                 pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1606                         zpool_get_type(pool->zpools[0]));
1607                 list_add(&pool->list, &zswap_pools);
1608                 zswap_has_pool = true;
1609         } else {
1610                 pr_err("pool creation failed\n");
1611                 zswap_enabled = false;
1612         }
1613
1614         shrink_wq = create_workqueue("zswap-shrink");
1615         if (!shrink_wq)
1616                 goto fallback_fail;
1617
1618         if (zswap_debugfs_init())
1619                 pr_warn("debugfs initialization failed\n");
1620         zswap_init_state = ZSWAP_INIT_SUCCEED;
1621         return 0;
1622
1623 fallback_fail:
1624         if (pool)
1625                 zswap_pool_destroy(pool);
1626 hp_fail:
1627         cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1628 dstmem_fail:
1629         kmem_cache_destroy(zswap_entry_cache);
1630 cache_fail:
1631         /* if built-in, we aren't unloaded on failure; don't allow use */
1632         zswap_init_state = ZSWAP_INIT_FAILED;
1633         zswap_enabled = false;
1634         return -ENOMEM;
1635 }
1636
1637 static int __init zswap_init(void)
1638 {
1639         if (!zswap_enabled)
1640                 return 0;
1641         return zswap_setup();
1642 }
1643 /* must be late so crypto has time to come up */
1644 late_initcall(zswap_init);
1645
1646 MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1647 MODULE_DESCRIPTION("Compressed cache for swap pages");