linux/mm/zswap.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * zswap.c - zswap driver file
   4 *
   5 * zswap is a backend for frontswap that takes pages that are in the process
   6 * of being swapped out and attempts to compress and store them in a
   7 * RAM-based memory pool.  This can result in a significant I/O reduction on
   8 * the swap device and, in the case where decompressing from RAM is faster
   9 * than reading from the swap device, can also improve workload performance.
  10 *
  11 * Copyright (C) 2012  Seth Jennings <sjenning@linux.vnet.ibm.com>
  12*/
  13
  14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16#include <linux/module.h>
  17#include <linux/cpu.h>
  18#include <linux/highmem.h>
  19#include <linux/slab.h>
  20#include <linux/spinlock.h>
  21#include <linux/types.h>
  22#include <linux/atomic.h>
  23#include <linux/frontswap.h>
  24#include <linux/rbtree.h>
  25#include <linux/swap.h>
  26#include <linux/crypto.h>
  27#include <linux/mempool.h>
  28#include <linux/zpool.h>
  29
  30#include <linux/mm_types.h>
  31#include <linux/page-flags.h>
  32#include <linux/swapops.h>
  33#include <linux/writeback.h>
  34#include <linux/pagemap.h>
  35
  36/*********************************
  37* statistics
  38**********************************/
  39/* Total bytes used by the compressed storage */
  40static u64 zswap_pool_total_size;
  41/* The number of compressed pages currently stored in zswap */
  42static atomic_t zswap_stored_pages = ATOMIC_INIT(0);
  43/* The number of same-value filled pages currently stored in zswap */
  44static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0);
  45
  46/*
  47 * The statistics below are not protected from concurrent access for
  48 * performance reasons so they may not be a 100% accurate.  However,
  49 * they do provide useful information on roughly how many times a
  50 * certain event is occurring.
  51*/
  52
  53/* Pool limit was hit (see zswap_max_pool_percent) */
  54static u64 zswap_pool_limit_hit;
  55/* Pages written back when pool limit was reached */
  56static u64 zswap_written_back_pages;
  57/* Store failed due to a reclaim failure after pool limit was reached */
  58static u64 zswap_reject_reclaim_fail;
  59/* Compressed page was too big for the allocator to (optimally) store */
  60static u64 zswap_reject_compress_poor;
  61/* Store failed because underlying allocator could not get memory */
  62static u64 zswap_reject_alloc_fail;
  63/* Store failed because the entry metadata could not be allocated (rare) */
  64static u64 zswap_reject_kmemcache_fail;
  65/* Duplicate store was encountered (rare) */
  66static u64 zswap_duplicate_entry;
  67
  68/*********************************
  69* tunables
  70**********************************/
  71
  72#define ZSWAP_PARAM_UNSET ""
  73
  74/* Enable/disable zswap (disabled by default) */
  75static bool zswap_enabled;
  76static int zswap_enabled_param_set(const char *,
  77                                   const struct kernel_param *);
  78static struct kernel_param_ops zswap_enabled_param_ops = {
  79        .set =          zswap_enabled_param_set,
  80        .get =          param_get_bool,
  81};
  82module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
  83
  84/* Crypto compressor to use */
  85#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
  86static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
  87static int zswap_compressor_param_set(const char *,
  88                                      const struct kernel_param *);
  89static struct kernel_param_ops zswap_compressor_param_ops = {
  90        .set =          zswap_compressor_param_set,
  91        .get =          param_get_charp,
  92        .free =         param_free_charp,
  93};
  94module_param_cb(compressor, &zswap_compressor_param_ops,
  95                &zswap_compressor, 0644);
  96
  97/* Compressed storage zpool to use */
  98#define ZSWAP_ZPOOL_DEFAULT "zbud"
  99static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
 100static int zswap_zpool_param_set(const char *, const struct kernel_param *);
 101static struct kernel_param_ops zswap_zpool_param_ops = {
 102        .set =          zswap_zpool_param_set,
 103        .get =          param_get_charp,
 104        .free =         param_free_charp,
 105};
 106module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
 107
 108/* The maximum percentage of memory that the compressed pool can occupy */
 109static unsigned int zswap_max_pool_percent = 20;
 110module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
 111
 112/* Enable/disable handling same-value filled pages (enabled by default) */
 113static bool zswap_same_filled_pages_enabled = true;
 114module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
 115                   bool, 0644);
 116
 117/*********************************
 118* data structures
 119**********************************/
 120
 121struct zswap_pool {
 122        struct zpool *zpool;
 123        struct crypto_comp * __percpu *tfm;
 124        struct kref kref;
 125        struct list_head list;
 126        struct work_struct work;
 127        struct hlist_node node;
 128        char tfm_name[CRYPTO_MAX_ALG_NAME];
 129};
 130
 131/*
 132 * struct zswap_entry
 133 *
 134 * This structure contains the metadata for tracking a single compressed
 135 * page within zswap.
 136 *
 137 * rbnode - links the entry into red-black tree for the appropriate swap type
 138 * offset - the swap offset for the entry.  Index into the red-black tree.
 139 * refcount - the number of outstanding reference to the entry. This is needed
 140 *            to protect against premature freeing of the entry by code
 141 *            concurrent calls to load, invalidate, and writeback.  The lock
 142 *            for the zswap_tree structure that contains the entry must
 143 *            be held while changing the refcount.  Since the lock must
 144 *            be held, there is no reason to also make refcount atomic.
 145 * length - the length in bytes of the compressed page data.  Needed during
 146 *          decompression. For a same value filled page length is 0.
 147 * pool - the zswap_pool the entry's data is in
 148 * handle - zpool allocation handle that stores the compressed page data
 149 * value - value of the same-value filled pages which have same content
 150 */
 151struct zswap_entry {
 152        struct rb_node rbnode;
 153        pgoff_t offset;
 154        int refcount;
 155        unsigned int length;
 156        struct zswap_pool *pool;
 157        union {
 158                unsigned long handle;
 159                unsigned long value;
 160        };
 161};
 162
 163struct zswap_header {
 164        swp_entry_t swpentry;
 165};
 166
 167/*
 168 * The tree lock in the zswap_tree struct protects a few things:
 169 * - the rbtree
 170 * - the refcount field of each entry in the tree
 171 */
 172struct zswap_tree {
 173        struct rb_root rbroot;
 174        spinlock_t lock;
 175};
 176
 177static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
 178
 179/* RCU-protected iteration */
 180static LIST_HEAD(zswap_pools);
 181/* protects zswap_pools list modification */
 182static DEFINE_SPINLOCK(zswap_pools_lock);
 183/* pool counter to provide unique names to zpool */
 184static atomic_t zswap_pools_count = ATOMIC_INIT(0);
 185
 186/* used by param callback function */
 187static bool zswap_init_started;
 188
 189/* fatal error during init */
 190static bool zswap_init_failed;
 191
 192/* init completed, but couldn't create the initial pool */
 193static bool zswap_has_pool;
 194
 195/*********************************
 196* helpers and fwd declarations
 197**********************************/
 198
 199#define zswap_pool_debug(msg, p)                                \
 200        pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,         \
 201                 zpool_get_type((p)->zpool))
 202
 203static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
 204static int zswap_pool_get(struct zswap_pool *pool);
 205static void zswap_pool_put(struct zswap_pool *pool);
 206
 207static const struct zpool_ops zswap_zpool_ops = {
 208        .evict = zswap_writeback_entry
 209};
 210
 211static bool zswap_is_full(void)
 212{
 213        return totalram_pages() * zswap_max_pool_percent / 100 <
 214                        DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
 215}
 216
 217static void zswap_update_total_size(void)
 218{
 219        struct zswap_pool *pool;
 220        u64 total = 0;
 221
 222        rcu_read_lock();
 223
 224        list_for_each_entry_rcu(pool, &zswap_pools, list)
 225                total += zpool_get_total_size(pool->zpool);
 226
 227        rcu_read_unlock();
 228
 229        zswap_pool_total_size = total;
 230}
 231
 232/*********************************
 233* zswap entry functions
 234**********************************/
 235static struct kmem_cache *zswap_entry_cache;
 236
 237static int __init zswap_entry_cache_create(void)
 238{
 239        zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
 240        return zswap_entry_cache == NULL;
 241}
 242
 243static void __init zswap_entry_cache_destroy(void)
 244{
 245        kmem_cache_destroy(zswap_entry_cache);
 246}
 247
 248static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
 249{
 250        struct zswap_entry *entry;
 251        entry = kmem_cache_alloc(zswap_entry_cache, gfp);
 252        if (!entry)
 253                return NULL;
 254        entry->refcount = 1;
 255        RB_CLEAR_NODE(&entry->rbnode);
 256        return entry;
 257}
 258
 259static void zswap_entry_cache_free(struct zswap_entry *entry)
 260{
 261        kmem_cache_free(zswap_entry_cache, entry);
 262}
 263
 264/*********************************
 265* rbtree functions
 266**********************************/
 267static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
 268{
 269        struct rb_node *node = root->rb_node;
 270        struct zswap_entry *entry;
 271
 272        while (node) {
 273                entry = rb_entry(node, struct zswap_entry, rbnode);
 274                if (entry->offset > offset)
 275                        node = node->rb_left;
 276                else if (entry->offset < offset)
 277                        node = node->rb_right;
 278                else
 279                        return entry;
 280        }
 281        return NULL;
 282}
 283
 284/*
 285 * In the case that a entry with the same offset is found, a pointer to
 286 * the existing entry is stored in dupentry and the function returns -EEXIST
 287 */
 288static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
 289                        struct zswap_entry **dupentry)
 290{
 291        struct rb_node **link = &root->rb_node, *parent = NULL;
 292        struct zswap_entry *myentry;
 293
 294        while (*link) {
 295                parent = *link;
 296                myentry = rb_entry(parent, struct zswap_entry, rbnode);
 297                if (myentry->offset > entry->offset)
 298                        link = &(*link)->rb_left;
 299                else if (myentry->offset < entry->offset)
 300                        link = &(*link)->rb_right;
 301                else {
 302                        *dupentry = myentry;
 303                        return -EEXIST;
 304                }
 305        }
 306        rb_link_node(&entry->rbnode, parent, link);
 307        rb_insert_color(&entry->rbnode, root);
 308        return 0;
 309}
 310
 311static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
 312{
 313        if (!RB_EMPTY_NODE(&entry->rbnode)) {
 314                rb_erase(&entry->rbnode, root);
 315                RB_CLEAR_NODE(&entry->rbnode);
 316        }
 317}
 318
 319/*
 320 * Carries out the common pattern of freeing and entry's zpool allocation,
 321 * freeing the entry itself, and decrementing the number of stored pages.
 322 */
 323static void zswap_free_entry(struct zswap_entry *entry)
 324{
 325        if (!entry->length)
 326                atomic_dec(&zswap_same_filled_pages);
 327        else {
 328                zpool_free(entry->pool->zpool, entry->handle);
 329                zswap_pool_put(entry->pool);
 330        }
 331        zswap_entry_cache_free(entry);
 332        atomic_dec(&zswap_stored_pages);
 333        zswap_update_total_size();
 334}
 335
 336/* caller must hold the tree lock */
 337static void zswap_entry_get(struct zswap_entry *entry)
 338{
 339        entry->refcount++;
 340}
 341
 342/* caller must hold the tree lock
 343* remove from the tree and free it, if nobody reference the entry
 344*/
 345static void zswap_entry_put(struct zswap_tree *tree,
 346                        struct zswap_entry *entry)
 347{
 348        int refcount = --entry->refcount;
 349
 350        BUG_ON(refcount < 0);
 351        if (refcount == 0) {
 352                zswap_rb_erase(&tree->rbroot, entry);
 353                zswap_free_entry(entry);
 354        }
 355}
 356
 357/* caller must hold the tree lock */
 358static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
 359                                pgoff_t offset)
 360{
 361        struct zswap_entry *entry;
 362
 363        entry = zswap_rb_search(root, offset);
 364        if (entry)
 365                zswap_entry_get(entry);
 366
 367        return entry;
 368}
 369
 370/*********************************
 371* per-cpu code
 372**********************************/
 373static DEFINE_PER_CPU(u8 *, zswap_dstmem);
 374
 375static int zswap_dstmem_prepare(unsigned int cpu)
 376{
 377        u8 *dst;
 378
 379        dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
 380        if (!dst)
 381                return -ENOMEM;
 382
 383        per_cpu(zswap_dstmem, cpu) = dst;
 384        return 0;
 385}
 386
 387static int zswap_dstmem_dead(unsigned int cpu)
 388{
 389        u8 *dst;
 390
 391        dst = per_cpu(zswap_dstmem, cpu);
 392        kfree(dst);
 393        per_cpu(zswap_dstmem, cpu) = NULL;
 394
 395        return 0;
 396}
 397
 398static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 399{
 400        struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 401        struct crypto_comp *tfm;
 402
 403        if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu)))
 404                return 0;
 405
 406        tfm = crypto_alloc_comp(pool->tfm_name, 0, 0);
 407        if (IS_ERR_OR_NULL(tfm)) {
 408                pr_err("could not alloc crypto comp %s : %ld\n",
 409                       pool->tfm_name, PTR_ERR(tfm));
 410                return -ENOMEM;
 411        }
 412        *per_cpu_ptr(pool->tfm, cpu) = tfm;
 413        return 0;
 414}
 415
 416static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 417{
 418        struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 419        struct crypto_comp *tfm;
 420
 421        tfm = *per_cpu_ptr(pool->tfm, cpu);
 422        if (!IS_ERR_OR_NULL(tfm))
 423                crypto_free_comp(tfm);
 424        *per_cpu_ptr(pool->tfm, cpu) = NULL;
 425        return 0;
 426}
 427
 428/*********************************
 429* pool functions
 430**********************************/
 431
 432static struct zswap_pool *__zswap_pool_current(void)
 433{
 434        struct zswap_pool *pool;
 435
 436        pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
 437        WARN_ONCE(!pool && zswap_has_pool,
 438                  "%s: no page storage pool!\n", __func__);
 439
 440        return pool;
 441}
 442
 443static struct zswap_pool *zswap_pool_current(void)
 444{
 445        assert_spin_locked(&zswap_pools_lock);
 446
 447        return __zswap_pool_current();
 448}
 449
 450static struct zswap_pool *zswap_pool_current_get(void)
 451{
 452        struct zswap_pool *pool;
 453
 454        rcu_read_lock();
 455
 456        pool = __zswap_pool_current();
 457        if (!zswap_pool_get(pool))
 458                pool = NULL;
 459
 460        rcu_read_unlock();
 461
 462        return pool;
 463}
 464
 465static struct zswap_pool *zswap_pool_last_get(void)
 466{
 467        struct zswap_pool *pool, *last = NULL;
 468
 469        rcu_read_lock();
 470
 471        list_for_each_entry_rcu(pool, &zswap_pools, list)
 472                last = pool;
 473        WARN_ONCE(!last && zswap_has_pool,
 474                  "%s: no page storage pool!\n", __func__);
 475        if (!zswap_pool_get(last))
 476                last = NULL;
 477
 478        rcu_read_unlock();
 479
 480        return last;
 481}
 482
 483/* type and compressor must be null-terminated */
 484static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
 485{
 486        struct zswap_pool *pool;
 487
 488        assert_spin_locked(&zswap_pools_lock);
 489
 490        list_for_each_entry_rcu(pool, &zswap_pools, list) {
 491                if (strcmp(pool->tfm_name, compressor))
 492                        continue;
 493                if (strcmp(zpool_get_type(pool->zpool), type))
 494                        continue;
 495                /* if we can't get it, it's about to be destroyed */
 496                if (!zswap_pool_get(pool))
 497                        continue;
 498                return pool;
 499        }
 500
 501        return NULL;
 502}
 503
 504static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
 505{
 506        struct zswap_pool *pool;
 507        char name[38]; /* 'zswap' + 32 char (max) num + \0 */
 508        gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
 509        int ret;
 510
 511        if (!zswap_has_pool) {
 512                /* if either are unset, pool initialization failed, and we
 513                 * need both params to be set correctly before trying to
 514                 * create a pool.
 515                 */
 516                if (!strcmp(type, ZSWAP_PARAM_UNSET))
 517                        return NULL;
 518                if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
 519                        return NULL;
 520        }
 521
 522        pool = kzalloc(sizeof(*pool), GFP_KERNEL);
 523        if (!pool)
 524                return NULL;
 525
 526        /* unique name for each pool specifically required by zsmalloc */
 527        snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
 528
 529        pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
 530        if (!pool->zpool) {
 531                pr_err("%s zpool not available\n", type);
 532                goto error;
 533        }
 534        pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
 535
 536        strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
 537        pool->tfm = alloc_percpu(struct crypto_comp *);
 538        if (!pool->tfm) {
 539                pr_err("percpu alloc failed\n");
 540                goto error;
 541        }
 542
 543        ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
 544                                       &pool->node);
 545        if (ret)
 546                goto error;
 547        pr_debug("using %s compressor\n", pool->tfm_name);
 548
 549        /* being the current pool takes 1 ref; this func expects the
 550         * caller to always add the new pool as the current pool
 551         */
 552        kref_init(&pool->kref);
 553        INIT_LIST_HEAD(&pool->list);
 554
 555        zswap_pool_debug("created", pool);
 556
 557        return pool;
 558
 559error:
 560        free_percpu(pool->tfm);
 561        if (pool->zpool)
 562                zpool_destroy_pool(pool->zpool);
 563        kfree(pool);
 564        return NULL;
 565}
 566
 567static __init struct zswap_pool *__zswap_pool_create_fallback(void)
 568{
 569        bool has_comp, has_zpool;
 570
 571        has_comp = crypto_has_comp(zswap_compressor, 0, 0);
 572        if (!has_comp && strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
 573                pr_err("compressor %s not available, using default %s\n",
 574                       zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);
 575                param_free_charp(&zswap_compressor);
 576                zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
 577                has_comp = crypto_has_comp(zswap_compressor, 0, 0);
 578        }
 579        if (!has_comp) {
 580                pr_err("default compressor %s not available\n",
 581                       zswap_compressor);
 582                param_free_charp(&zswap_compressor);
 583                zswap_compressor = ZSWAP_PARAM_UNSET;
 584        }
 585
 586        has_zpool = zpool_has_pool(zswap_zpool_type);
 587        if (!has_zpool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
 588                pr_err("zpool %s not available, using default %s\n",
 589                       zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);
 590                param_free_charp(&zswap_zpool_type);
 591                zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
 592                has_zpool = zpool_has_pool(zswap_zpool_type);
 593        }
 594        if (!has_zpool) {
 595                pr_err("default zpool %s not available\n",
 596                       zswap_zpool_type);
 597                param_free_charp(&zswap_zpool_type);
 598                zswap_zpool_type = ZSWAP_PARAM_UNSET;
 599        }
 600
 601        if (!has_comp || !has_zpool)
 602                return NULL;
 603
 604        return zswap_pool_create(zswap_zpool_type, zswap_compressor);
 605}
 606
 607static void zswap_pool_destroy(struct zswap_pool *pool)
 608{
 609        zswap_pool_debug("destroying", pool);
 610
 611        cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
 612        free_percpu(pool->tfm);
 613        zpool_destroy_pool(pool->zpool);
 614        kfree(pool);
 615}
 616
 617static int __must_check zswap_pool_get(struct zswap_pool *pool)
 618{
 619        if (!pool)
 620                return 0;
 621
 622        return kref_get_unless_zero(&pool->kref);
 623}
 624
 625static void __zswap_pool_release(struct work_struct *work)
 626{
 627        struct zswap_pool *pool = container_of(work, typeof(*pool), work);
 628
 629        synchronize_rcu();
 630
 631        /* nobody should have been able to get a kref... */
 632        WARN_ON(kref_get_unless_zero(&pool->kref));
 633
 634        /* pool is now off zswap_pools list and has no references. */
 635        zswap_pool_destroy(pool);
 636}
 637
 638static void __zswap_pool_empty(struct kref *kref)
 639{
 640        struct zswap_pool *pool;
 641
 642        pool = container_of(kref, typeof(*pool), kref);
 643
 644        spin_lock(&zswap_pools_lock);
 645
 646        WARN_ON(pool == zswap_pool_current());
 647
 648        list_del_rcu(&pool->list);
 649
 650        INIT_WORK(&pool->work, __zswap_pool_release);
 651        schedule_work(&pool->work);
 652
 653        spin_unlock(&zswap_pools_lock);
 654}
 655
 656static void zswap_pool_put(struct zswap_pool *pool)
 657{
 658        kref_put(&pool->kref, __zswap_pool_empty);
 659}
 660
 661/*********************************
 662* param callbacks
 663**********************************/
 664
 665/* val must be a null-terminated string */
 666static int __zswap_param_set(const char *val, const struct kernel_param *kp,
 667                             char *type, char *compressor)
 668{
 669        struct zswap_pool *pool, *put_pool = NULL;
 670        char *s = strstrip((char *)val);
 671        int ret;
 672
 673        if (zswap_init_failed) {
 674                pr_err("can't set param, initialization failed\n");
 675                return -ENODEV;
 676        }
 677
 678        /* no change required */
 679        if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
 680                return 0;
 681
 682        /* if this is load-time (pre-init) param setting,
 683         * don't create a pool; that's done during init.
 684         */
 685        if (!zswap_init_started)
 686                return param_set_charp(s, kp);
 687
 688        if (!type) {
 689                if (!zpool_has_pool(s)) {
 690                        pr_err("zpool %s not available\n", s);
 691                        return -ENOENT;
 692                }
 693                type = s;
 694        } else if (!compressor) {
 695                if (!crypto_has_comp(s, 0, 0)) {
 696                        pr_err("compressor %s not available\n", s);
 697                        return -ENOENT;
 698                }
 699                compressor = s;
 700        } else {
 701                WARN_ON(1);
 702                return -EINVAL;
 703        }
 704
 705        spin_lock(&zswap_pools_lock);
 706
 707        pool = zswap_pool_find_get(type, compressor);
 708        if (pool) {
 709                zswap_pool_debug("using existing", pool);
 710                WARN_ON(pool == zswap_pool_current());
 711                list_del_rcu(&pool->list);
 712        }
 713
 714        spin_unlock(&zswap_pools_lock);
 715
 716        if (!pool)
 717                pool = zswap_pool_create(type, compressor);
 718
 719        if (pool)
 720                ret = param_set_charp(s, kp);
 721        else
 722                ret = -EINVAL;
 723
 724        spin_lock(&zswap_pools_lock);
 725
 726        if (!ret) {
 727                put_pool = zswap_pool_current();
 728                list_add_rcu(&pool->list, &zswap_pools);
 729                zswap_has_pool = true;
 730        } else if (pool) {
 731                /* add the possibly pre-existing pool to the end of the pools
 732                 * list; if it's new (and empty) then it'll be removed and
 733                 * destroyed by the put after we drop the lock
 734                 */
 735                list_add_tail_rcu(&pool->list, &zswap_pools);
 736                put_pool = pool;
 737        }
 738
 739        spin_unlock(&zswap_pools_lock);
 740
 741        if (!zswap_has_pool && !pool) {
 742                /* if initial pool creation failed, and this pool creation also
 743                 * failed, maybe both compressor and zpool params were bad.
 744                 * Allow changing this param, so pool creation will succeed
 745                 * when the other param is changed. We already verified this
 746                 * param is ok in the zpool_has_pool() or crypto_has_comp()
 747                 * checks above.
 748                 */
 749                ret = param_set_charp(s, kp);
 750        }
 751
 752        /* drop the ref from either the old current pool,
 753         * or the new pool we failed to add
 754         */
 755        if (put_pool)
 756                zswap_pool_put(put_pool);
 757
 758        return ret;
 759}
 760
 761static int zswap_compressor_param_set(const char *val,
 762                                      const struct kernel_param *kp)
 763{
 764        return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
 765}
 766
 767static int zswap_zpool_param_set(const char *val,
 768                                 const struct kernel_param *kp)
 769{
 770        return __zswap_param_set(val, kp, NULL, zswap_compressor);
 771}
 772
 773static int zswap_enabled_param_set(const char *val,
 774                                   const struct kernel_param *kp)
 775{
 776        if (zswap_init_failed) {
 777                pr_err("can't enable, initialization failed\n");
 778                return -ENODEV;
 779        }
 780        if (!zswap_has_pool && zswap_init_started) {
 781                pr_err("can't enable, no pool configured\n");
 782                return -ENODEV;
 783        }
 784
 785        return param_set_bool(val, kp);
 786}
 787
 788/*********************************
 789* writeback code
 790**********************************/
 791/* return enum for zswap_get_swap_cache_page */
 792enum zswap_get_swap_ret {
 793        ZSWAP_SWAPCACHE_NEW,
 794        ZSWAP_SWAPCACHE_EXIST,
 795        ZSWAP_SWAPCACHE_FAIL,
 796};
 797
 798/*
 799 * zswap_get_swap_cache_page
 800 *
 801 * This is an adaption of read_swap_cache_async()
 802 *
 803 * This function tries to find a page with the given swap entry
 804 * in the swapper_space address space (the swap cache).  If the page
 805 * is found, it is returned in retpage.  Otherwise, a page is allocated,
 806 * added to the swap cache, and returned in retpage.
 807 *
 808 * If success, the swap cache page is returned in retpage
 809 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
 810 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
 811 *     the new page is added to swapcache and locked
 812 * Returns ZSWAP_SWAPCACHE_FAIL on error
 813 */
 814static int zswap_get_swap_cache_page(swp_entry_t entry,
 815                                struct page **retpage)
 816{
 817        bool page_was_allocated;
 818
 819        *retpage = __read_swap_cache_async(entry, GFP_KERNEL,
 820                        NULL, 0, &page_was_allocated);
 821        if (page_was_allocated)
 822                return ZSWAP_SWAPCACHE_NEW;
 823        if (!*retpage)
 824                return ZSWAP_SWAPCACHE_FAIL;
 825        return ZSWAP_SWAPCACHE_EXIST;
 826}
 827
 828/*
 829 * Attempts to free an entry by adding a page to the swap cache,
 830 * decompressing the entry data into the page, and issuing a
 831 * bio write to write the page back to the swap device.
 832 *
 833 * This can be thought of as a "resumed writeback" of the page
 834 * to the swap device.  We are basically resuming the same swap
 835 * writeback path that was intercepted with the frontswap_store()
 836 * in the first place.  After the page has been decompressed into
 837 * the swap cache, the compressed version stored by zswap can be
 838 * freed.
 839 */
 840static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 841{
 842        struct zswap_header *zhdr;
 843        swp_entry_t swpentry;
 844        struct zswap_tree *tree;
 845        pgoff_t offset;
 846        struct zswap_entry *entry;
 847        struct page *page;
 848        struct crypto_comp *tfm;
 849        u8 *src, *dst;
 850        unsigned int dlen;
 851        int ret;
 852        struct writeback_control wbc = {
 853                .sync_mode = WB_SYNC_NONE,
 854        };
 855
 856        /* extract swpentry from data */
 857        zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
 858        swpentry = zhdr->swpentry; /* here */
 859        tree = zswap_trees[swp_type(swpentry)];
 860        offset = swp_offset(swpentry);
 861
 862        /* find and ref zswap entry */
 863        spin_lock(&tree->lock);
 864        entry = zswap_entry_find_get(&tree->rbroot, offset);
 865        if (!entry) {
 866                /* entry was invalidated */
 867                spin_unlock(&tree->lock);
 868                zpool_unmap_handle(pool, handle);
 869                return 0;
 870        }
 871        spin_unlock(&tree->lock);
 872        BUG_ON(offset != entry->offset);
 873
 874        /* try to allocate swap cache page */
 875        switch (zswap_get_swap_cache_page(swpentry, &page)) {
 876        case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
 877                ret = -ENOMEM;
 878                goto fail;
 879
 880        case ZSWAP_SWAPCACHE_EXIST:
 881                /* page is already in the swap cache, ignore for now */
 882                put_page(page);
 883                ret = -EEXIST;
 884                goto fail;
 885
 886        case ZSWAP_SWAPCACHE_NEW: /* page is locked */
 887                /* decompress */
 888                dlen = PAGE_SIZE;
 889                src = (u8 *)zhdr + sizeof(struct zswap_header);
 890                dst = kmap_atomic(page);
 891                tfm = *get_cpu_ptr(entry->pool->tfm);
 892                ret = crypto_comp_decompress(tfm, src, entry->length,
 893                                             dst, &dlen);
 894                put_cpu_ptr(entry->pool->tfm);
 895                kunmap_atomic(dst);
 896                BUG_ON(ret);
 897                BUG_ON(dlen != PAGE_SIZE);
 898
 899                /* page is up to date */
 900                SetPageUptodate(page);
 901        }
 902
 903        /* move it to the tail of the inactive list after end_writeback */
 904        SetPageReclaim(page);
 905
 906        /* start writeback */
 907        __swap_writepage(page, &wbc, end_swap_bio_write);
 908        put_page(page);
 909        zswap_written_back_pages++;
 910
 911        spin_lock(&tree->lock);
 912        /* drop local reference */
 913        zswap_entry_put(tree, entry);
 914
 915        /*
 916        * There are two possible situations for entry here:
 917        * (1) refcount is 1(normal case),  entry is valid and on the tree
 918        * (2) refcount is 0, entry is freed and not on the tree
 919        *     because invalidate happened during writeback
 920        *  search the tree and free the entry if find entry
 921        */
 922        if (entry == zswap_rb_search(&tree->rbroot, offset))
 923                zswap_entry_put(tree, entry);
 924        spin_unlock(&tree->lock);
 925
 926        goto end;
 927
 928        /*
 929        * if we get here due to ZSWAP_SWAPCACHE_EXIST
 930        * a load may happening concurrently
 931        * it is safe and okay to not free the entry
 932        * if we free the entry in the following put
 933        * it it either okay to return !0
 934        */
 935fail:
 936        spin_lock(&tree->lock);
 937        zswap_entry_put(tree, entry);
 938        spin_unlock(&tree->lock);
 939
 940end:
 941        zpool_unmap_handle(pool, handle);
 942        return ret;
 943}
 944
 945static int zswap_shrink(void)
 946{
 947        struct zswap_pool *pool;
 948        int ret;
 949
 950        pool = zswap_pool_last_get();
 951        if (!pool)
 952                return -ENOENT;
 953
 954        ret = zpool_shrink(pool->zpool, 1, NULL);
 955
 956        zswap_pool_put(pool);
 957
 958        return ret;
 959}
 960
 961static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
 962{
 963        unsigned int pos;
 964        unsigned long *page;
 965
 966        page = (unsigned long *)ptr;
 967        for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
 968                if (page[pos] != page[0])
 969                        return 0;
 970        }
 971        *value = page[0];
 972        return 1;
 973}
 974
 975static void zswap_fill_page(void *ptr, unsigned long value)
 976{
 977        unsigned long *page;
 978
 979        page = (unsigned long *)ptr;
 980        memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
 981}
 982
 983/*********************************
 984* frontswap hooks
 985**********************************/
 986/* attempts to compress and store an single page */
 987static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 988                                struct page *page)
 989{
 990        struct zswap_tree *tree = zswap_trees[type];
 991        struct zswap_entry *entry, *dupentry;
 992        struct crypto_comp *tfm;
 993        int ret;
 994        unsigned int hlen, dlen = PAGE_SIZE;
 995        unsigned long handle, value;
 996        char *buf;
 997        u8 *src, *dst;
 998        struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
 999        gfp_t gfp;
1000
1001        /* THP isn't supported */
1002        if (PageTransHuge(page)) {
1003                ret = -EINVAL;
1004                goto reject;
1005        }
1006
1007        if (!zswap_enabled || !tree) {
1008                ret = -ENODEV;
1009                goto reject;
1010        }
1011
1012        /* reclaim space if needed */
1013        if (zswap_is_full()) {
1014                zswap_pool_limit_hit++;
1015                if (zswap_shrink()) {
1016                        zswap_reject_reclaim_fail++;
1017                        ret = -ENOMEM;
1018                        goto reject;
1019                }
1020
1021                /* A second zswap_is_full() check after
1022                 * zswap_shrink() to make sure it's now
1023                 * under the max_pool_percent
1024                 */
1025                if (zswap_is_full()) {
1026                        ret = -ENOMEM;
1027                        goto reject;
1028                }
1029        }
1030
1031        /* allocate entry */
1032        entry = zswap_entry_cache_alloc(GFP_KERNEL);
1033        if (!entry) {
1034                zswap_reject_kmemcache_fail++;
1035                ret = -ENOMEM;
1036                goto reject;
1037        }
1038
1039        if (zswap_same_filled_pages_enabled) {
1040                src = kmap_atomic(page);
1041                if (zswap_is_page_same_filled(src, &value)) {
1042                        kunmap_atomic(src);
1043                        entry->offset = offset;
1044                        entry->length = 0;
1045                        entry->value = value;
1046                        atomic_inc(&zswap_same_filled_pages);
1047                        goto insert_entry;
1048                }
1049                kunmap_atomic(src);
1050        }
1051
1052        /* if entry is successfully added, it keeps the reference */
1053        entry->pool = zswap_pool_current_get();
1054        if (!entry->pool) {
1055                ret = -EINVAL;
1056                goto freepage;
1057        }
1058
1059        /* compress */
1060        dst = get_cpu_var(zswap_dstmem);
1061        tfm = *get_cpu_ptr(entry->pool->tfm);
1062        src = kmap_atomic(page);
1063        ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
1064        kunmap_atomic(src);
1065        put_cpu_ptr(entry->pool->tfm);
1066        if (ret) {
1067                ret = -EINVAL;
1068                goto put_dstmem;
1069        }
1070
1071        /* store */
1072        hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1073        gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1074        if (zpool_malloc_support_movable(entry->pool->zpool))
1075                gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1076        ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
1077        if (ret == -ENOSPC) {
1078                zswap_reject_compress_poor++;
1079                goto put_dstmem;
1080        }
1081        if (ret) {
1082                zswap_reject_alloc_fail++;
1083                goto put_dstmem;
1084        }
1085        buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
1086        memcpy(buf, &zhdr, hlen);
1087        memcpy(buf + hlen, dst, dlen);
1088        zpool_unmap_handle(entry->pool->zpool, handle);
1089        put_cpu_var(zswap_dstmem);
1090
1091        /* populate entry */
1092        entry->offset = offset;
1093        entry->handle = handle;
1094        entry->length = dlen;
1095
1096insert_entry:
1097        /* map */
1098        spin_lock(&tree->lock);
1099        do {
1100                ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1101                if (ret == -EEXIST) {
1102                        zswap_duplicate_entry++;
1103                        /* remove from rbtree */
1104                        zswap_rb_erase(&tree->rbroot, dupentry);
1105                        zswap_entry_put(tree, dupentry);
1106                }
1107        } while (ret == -EEXIST);
1108        spin_unlock(&tree->lock);
1109
1110        /* update stats */
1111        atomic_inc(&zswap_stored_pages);
1112        zswap_update_total_size();
1113
1114        return 0;
1115
1116put_dstmem:
1117        put_cpu_var(zswap_dstmem);
1118        zswap_pool_put(entry->pool);
1119freepage:
1120        zswap_entry_cache_free(entry);
1121reject:
1122        return ret;
1123}
1124
1125/*
1126 * returns 0 if the page was successfully decompressed
1127 * return -1 on entry not found or error
1128*/
1129static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1130                                struct page *page)
1131{
1132        struct zswap_tree *tree = zswap_trees[type];
1133        struct zswap_entry *entry;
1134        struct crypto_comp *tfm;
1135        u8 *src, *dst;
1136        unsigned int dlen;
1137        int ret;
1138
1139        /* find */
1140        spin_lock(&tree->lock);
1141        entry = zswap_entry_find_get(&tree->rbroot, offset);
1142        if (!entry) {
1143                /* entry was written back */
1144                spin_unlock(&tree->lock);
1145                return -1;
1146        }
1147        spin_unlock(&tree->lock);
1148
1149        if (!entry->length) {
1150                dst = kmap_atomic(page);
1151                zswap_fill_page(dst, entry->value);
1152                kunmap_atomic(dst);
1153                goto freeentry;
1154        }
1155
1156        /* decompress */
1157        dlen = PAGE_SIZE;
1158        src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1159        if (zpool_evictable(entry->pool->zpool))
1160                src += sizeof(struct zswap_header);
1161        dst = kmap_atomic(page);
1162        tfm = *get_cpu_ptr(entry->pool->tfm);
1163        ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
1164        put_cpu_ptr(entry->pool->tfm);
1165        kunmap_atomic(dst);
1166        zpool_unmap_handle(entry->pool->zpool, entry->handle);
1167        BUG_ON(ret);
1168
1169freeentry:
1170        spin_lock(&tree->lock);
1171        zswap_entry_put(tree, entry);
1172        spin_unlock(&tree->lock);
1173
1174        return 0;
1175}
1176
1177/* frees an entry in zswap */
1178static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1179{
1180        struct zswap_tree *tree = zswap_trees[type];
1181        struct zswap_entry *entry;
1182
1183        /* find */
1184        spin_lock(&tree->lock);
1185        entry = zswap_rb_search(&tree->rbroot, offset);
1186        if (!entry) {
1187                /* entry was written back */
1188                spin_unlock(&tree->lock);
1189                return;
1190        }
1191
1192        /* remove from rbtree */
1193        zswap_rb_erase(&tree->rbroot, entry);
1194
1195        /* drop the initial reference from entry creation */
1196        zswap_entry_put(tree, entry);
1197
1198        spin_unlock(&tree->lock);
1199}
1200
1201/* frees all zswap entries for the given swap type */
1202static void zswap_frontswap_invalidate_area(unsigned type)
1203{
1204        struct zswap_tree *tree = zswap_trees[type];
1205        struct zswap_entry *entry, *n;
1206
1207        if (!tree)
1208                return;
1209
1210        /* walk the tree and free everything */
1211        spin_lock(&tree->lock);
1212        rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1213                zswap_free_entry(entry);
1214        tree->rbroot = RB_ROOT;
1215        spin_unlock(&tree->lock);
1216        kfree(tree);
1217        zswap_trees[type] = NULL;
1218}
1219
1220static void zswap_frontswap_init(unsigned type)
1221{
1222        struct zswap_tree *tree;
1223
1224        tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1225        if (!tree) {
1226                pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1227                return;
1228        }
1229
1230        tree->rbroot = RB_ROOT;
1231        spin_lock_init(&tree->lock);
1232        zswap_trees[type] = tree;
1233}
1234
1235static struct frontswap_ops zswap_frontswap_ops = {
1236        .store = zswap_frontswap_store,
1237        .load = zswap_frontswap_load,
1238        .invalidate_page = zswap_frontswap_invalidate_page,
1239        .invalidate_area = zswap_frontswap_invalidate_area,
1240        .init = zswap_frontswap_init
1241};
1242
1243/*********************************
1244* debugfs functions
1245**********************************/
1246#ifdef CONFIG_DEBUG_FS
1247#include <linux/debugfs.h>
1248
1249static struct dentry *zswap_debugfs_root;
1250
1251static int __init zswap_debugfs_init(void)
1252{
1253        if (!debugfs_initialized())
1254                return -ENODEV;
1255
1256        zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1257
1258        debugfs_create_u64("pool_limit_hit", 0444,
1259                           zswap_debugfs_root, &zswap_pool_limit_hit);
1260        debugfs_create_u64("reject_reclaim_fail", 0444,
1261                           zswap_debugfs_root, &zswap_reject_reclaim_fail);
1262        debugfs_create_u64("reject_alloc_fail", 0444,
1263                           zswap_debugfs_root, &zswap_reject_alloc_fail);
1264        debugfs_create_u64("reject_kmemcache_fail", 0444,
1265                           zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1266        debugfs_create_u64("reject_compress_poor", 0444,
1267                           zswap_debugfs_root, &zswap_reject_compress_poor);
1268        debugfs_create_u64("written_back_pages", 0444,
1269                           zswap_debugfs_root, &zswap_written_back_pages);
1270        debugfs_create_u64("duplicate_entry", 0444,
1271                           zswap_debugfs_root, &zswap_duplicate_entry);
1272        debugfs_create_u64("pool_total_size", 0444,
1273                           zswap_debugfs_root, &zswap_pool_total_size);
1274        debugfs_create_atomic_t("stored_pages", 0444,
1275                                zswap_debugfs_root, &zswap_stored_pages);
1276        debugfs_create_atomic_t("same_filled_pages", 0444,
1277                                zswap_debugfs_root, &zswap_same_filled_pages);
1278
1279        return 0;
1280}
1281
1282static void __exit zswap_debugfs_exit(void)
1283{
1284        debugfs_remove_recursive(zswap_debugfs_root);
1285}
1286#else
1287static int __init zswap_debugfs_init(void)
1288{
1289        return 0;
1290}
1291
1292static void __exit zswap_debugfs_exit(void) { }
1293#endif
1294
1295/*********************************
1296* module init and exit
1297**********************************/
1298static int __init init_zswap(void)
1299{
1300        struct zswap_pool *pool;
1301        int ret;
1302
1303        zswap_init_started = true;
1304
1305        if (zswap_entry_cache_create()) {
1306                pr_err("entry cache creation failed\n");
1307                goto cache_fail;
1308        }
1309
1310        ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1311                                zswap_dstmem_prepare, zswap_dstmem_dead);
1312        if (ret) {
1313                pr_err("dstmem alloc failed\n");
1314                goto dstmem_fail;
1315        }
1316
1317        ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1318                                      "mm/zswap_pool:prepare",
1319                                      zswap_cpu_comp_prepare,
1320                                      zswap_cpu_comp_dead);
1321        if (ret)
1322                goto hp_fail;
1323
1324        pool = __zswap_pool_create_fallback();
1325        if (pool) {
1326                pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1327                        zpool_get_type(pool->zpool));
1328                list_add(&pool->list, &zswap_pools);
1329                zswap_has_pool = true;
1330        } else {
1331                pr_err("pool creation failed\n");
1332                zswap_enabled = false;
1333        }
1334
1335        frontswap_register_ops(&zswap_frontswap_ops);
1336        if (zswap_debugfs_init())
1337                pr_warn("debugfs initialization failed\n");
1338        return 0;
1339
1340hp_fail:
1341        cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1342dstmem_fail:
1343        zswap_entry_cache_destroy();
1344cache_fail:
1345        /* if built-in, we aren't unloaded on failure; don't allow use */
1346        zswap_init_failed = true;
1347        zswap_enabled = false;
1348        return -ENOMEM;
1349}
1350/* must be late so crypto has time to come up */
1351late_initcall(init_zswap);
1352
1353MODULE_LICENSE("GPL");
1354MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1355MODULE_DESCRIPTION("Compressed cache for swap pages");
1356