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v5.4
   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");
v6.2
   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/scatterlist.h>
  28#include <linux/mempool.h>
  29#include <linux/zpool.h>
  30#include <crypto/acompress.h>
  31
  32#include <linux/mm_types.h>
  33#include <linux/page-flags.h>
  34#include <linux/swapops.h>
  35#include <linux/writeback.h>
  36#include <linux/pagemap.h>
  37#include <linux/workqueue.h>
  38
  39#include "swap.h"
  40
  41/*********************************
  42* statistics
  43**********************************/
  44/* Total bytes used by the compressed storage */
  45u64 zswap_pool_total_size;
  46/* The number of compressed pages currently stored in zswap */
  47atomic_t zswap_stored_pages = ATOMIC_INIT(0);
  48/* The number of same-value filled pages currently stored in zswap */
  49static 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) */
  59static u64 zswap_pool_limit_hit;
  60/* Pages written back when pool limit was reached */
  61static u64 zswap_written_back_pages;
  62/* Store failed due to a reclaim failure after pool limit was reached */
  63static u64 zswap_reject_reclaim_fail;
  64/* Compressed page was too big for the allocator to (optimally) store */
  65static u64 zswap_reject_compress_poor;
  66/* Store failed because underlying allocator could not get memory */
  67static u64 zswap_reject_alloc_fail;
  68/* Store failed because the entry metadata could not be allocated (rare) */
  69static u64 zswap_reject_kmemcache_fail;
  70/* Duplicate store was encountered (rare) */
  71static u64 zswap_duplicate_entry;
  72
  73/* Shrinker work queue */
  74static struct workqueue_struct *shrink_wq;
  75/* Pool limit was hit, we need to calm down */
  76static bool zswap_pool_reached_full;
  77
  78/*********************************
  79* tunables
  80**********************************/
  81
  82#define ZSWAP_PARAM_UNSET ""
  83
  84/* Enable/disable zswap */
  85static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);
  86static int zswap_enabled_param_set(const char *,
  87				   const struct kernel_param *);
  88static const struct kernel_param_ops zswap_enabled_param_ops = {
  89	.set =		zswap_enabled_param_set,
  90	.get =		param_get_bool,
  91};
  92module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);
  93
  94/* Crypto compressor to use */
  95static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
 
  96static int zswap_compressor_param_set(const char *,
  97				      const struct kernel_param *);
  98static const struct kernel_param_ops zswap_compressor_param_ops = {
  99	.set =		zswap_compressor_param_set,
 100	.get =		param_get_charp,
 101	.free =		param_free_charp,
 102};
 103module_param_cb(compressor, &zswap_compressor_param_ops,
 104		&zswap_compressor, 0644);
 105
 106/* Compressed storage zpool to use */
 107static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
 
 108static int zswap_zpool_param_set(const char *, const struct kernel_param *);
 109static const struct kernel_param_ops zswap_zpool_param_ops = {
 110	.set =		zswap_zpool_param_set,
 111	.get =		param_get_charp,
 112	.free =		param_free_charp,
 113};
 114module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644);
 115
 116/* The maximum percentage of memory that the compressed pool can occupy */
 117static unsigned int zswap_max_pool_percent = 20;
 118module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
 119
 120/* The threshold for accepting new pages after the max_pool_percent was hit */
 121static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */
 122module_param_named(accept_threshold_percent, zswap_accept_thr_percent,
 123		   uint, 0644);
 124
 125/*
 126 * Enable/disable handling same-value filled pages (enabled by default).
 127 * If disabled every page is considered non-same-value filled.
 128 */
 129static bool zswap_same_filled_pages_enabled = true;
 130module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled,
 131		   bool, 0644);
 132
 133/* Enable/disable handling non-same-value filled pages (enabled by default) */
 134static bool zswap_non_same_filled_pages_enabled = true;
 135module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled,
 136		   bool, 0644);
 137
 138/*********************************
 139* data structures
 140**********************************/
 141
 142struct crypto_acomp_ctx {
 143	struct crypto_acomp *acomp;
 144	struct acomp_req *req;
 145	struct crypto_wait wait;
 146	u8 *dstmem;
 147	struct mutex *mutex;
 148};
 149
 150struct zswap_pool {
 151	struct zpool *zpool;
 152	struct crypto_acomp_ctx __percpu *acomp_ctx;
 153	struct kref kref;
 154	struct list_head list;
 155	struct work_struct release_work;
 156	struct work_struct shrink_work;
 157	struct hlist_node node;
 158	char tfm_name[CRYPTO_MAX_ALG_NAME];
 159};
 160
 161/*
 162 * struct zswap_entry
 163 *
 164 * This structure contains the metadata for tracking a single compressed
 165 * page within zswap.
 166 *
 167 * rbnode - links the entry into red-black tree for the appropriate swap type
 168 * offset - the swap offset for the entry.  Index into the red-black tree.
 169 * refcount - the number of outstanding reference to the entry. This is needed
 170 *            to protect against premature freeing of the entry by code
 171 *            concurrent calls to load, invalidate, and writeback.  The lock
 172 *            for the zswap_tree structure that contains the entry must
 173 *            be held while changing the refcount.  Since the lock must
 174 *            be held, there is no reason to also make refcount atomic.
 175 * length - the length in bytes of the compressed page data.  Needed during
 176 *          decompression. For a same value filled page length is 0.
 177 * pool - the zswap_pool the entry's data is in
 178 * handle - zpool allocation handle that stores the compressed page data
 179 * value - value of the same-value filled pages which have same content
 180 */
 181struct zswap_entry {
 182	struct rb_node rbnode;
 183	pgoff_t offset;
 184	int refcount;
 185	unsigned int length;
 186	struct zswap_pool *pool;
 187	union {
 188		unsigned long handle;
 189		unsigned long value;
 190	};
 191	struct obj_cgroup *objcg;
 192};
 193
 194struct zswap_header {
 195	swp_entry_t swpentry;
 196};
 197
 198/*
 199 * The tree lock in the zswap_tree struct protects a few things:
 200 * - the rbtree
 201 * - the refcount field of each entry in the tree
 202 */
 203struct zswap_tree {
 204	struct rb_root rbroot;
 205	spinlock_t lock;
 206};
 207
 208static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
 209
 210/* RCU-protected iteration */
 211static LIST_HEAD(zswap_pools);
 212/* protects zswap_pools list modification */
 213static DEFINE_SPINLOCK(zswap_pools_lock);
 214/* pool counter to provide unique names to zpool */
 215static atomic_t zswap_pools_count = ATOMIC_INIT(0);
 216
 217/* used by param callback function */
 218static bool zswap_init_started;
 219
 220/* fatal error during init */
 221static bool zswap_init_failed;
 222
 223/* init completed, but couldn't create the initial pool */
 224static bool zswap_has_pool;
 225
 226/*********************************
 227* helpers and fwd declarations
 228**********************************/
 229
 230#define zswap_pool_debug(msg, p)				\
 231	pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name,		\
 232		 zpool_get_type((p)->zpool))
 233
 234static int zswap_writeback_entry(struct zpool *pool, unsigned long handle);
 235static int zswap_pool_get(struct zswap_pool *pool);
 236static void zswap_pool_put(struct zswap_pool *pool);
 237
 238static const struct zpool_ops zswap_zpool_ops = {
 239	.evict = zswap_writeback_entry
 240};
 241
 242static bool zswap_is_full(void)
 243{
 244	return totalram_pages() * zswap_max_pool_percent / 100 <
 245			DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
 246}
 247
 248static bool zswap_can_accept(void)
 249{
 250	return totalram_pages() * zswap_accept_thr_percent / 100 *
 251				zswap_max_pool_percent / 100 >
 252			DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE);
 253}
 254
 255static void zswap_update_total_size(void)
 256{
 257	struct zswap_pool *pool;
 258	u64 total = 0;
 259
 260	rcu_read_lock();
 261
 262	list_for_each_entry_rcu(pool, &zswap_pools, list)
 263		total += zpool_get_total_size(pool->zpool);
 264
 265	rcu_read_unlock();
 266
 267	zswap_pool_total_size = total;
 268}
 269
 270/*********************************
 271* zswap entry functions
 272**********************************/
 273static struct kmem_cache *zswap_entry_cache;
 274
 275static int __init zswap_entry_cache_create(void)
 276{
 277	zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
 278	return zswap_entry_cache == NULL;
 279}
 280
 281static void __init zswap_entry_cache_destroy(void)
 282{
 283	kmem_cache_destroy(zswap_entry_cache);
 284}
 285
 286static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp)
 287{
 288	struct zswap_entry *entry;
 289	entry = kmem_cache_alloc(zswap_entry_cache, gfp);
 290	if (!entry)
 291		return NULL;
 292	entry->refcount = 1;
 293	RB_CLEAR_NODE(&entry->rbnode);
 294	return entry;
 295}
 296
 297static void zswap_entry_cache_free(struct zswap_entry *entry)
 298{
 299	kmem_cache_free(zswap_entry_cache, entry);
 300}
 301
 302/*********************************
 303* rbtree functions
 304**********************************/
 305static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset)
 306{
 307	struct rb_node *node = root->rb_node;
 308	struct zswap_entry *entry;
 309
 310	while (node) {
 311		entry = rb_entry(node, struct zswap_entry, rbnode);
 312		if (entry->offset > offset)
 313			node = node->rb_left;
 314		else if (entry->offset < offset)
 315			node = node->rb_right;
 316		else
 317			return entry;
 318	}
 319	return NULL;
 320}
 321
 322/*
 323 * In the case that a entry with the same offset is found, a pointer to
 324 * the existing entry is stored in dupentry and the function returns -EEXIST
 325 */
 326static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry,
 327			struct zswap_entry **dupentry)
 328{
 329	struct rb_node **link = &root->rb_node, *parent = NULL;
 330	struct zswap_entry *myentry;
 331
 332	while (*link) {
 333		parent = *link;
 334		myentry = rb_entry(parent, struct zswap_entry, rbnode);
 335		if (myentry->offset > entry->offset)
 336			link = &(*link)->rb_left;
 337		else if (myentry->offset < entry->offset)
 338			link = &(*link)->rb_right;
 339		else {
 340			*dupentry = myentry;
 341			return -EEXIST;
 342		}
 343	}
 344	rb_link_node(&entry->rbnode, parent, link);
 345	rb_insert_color(&entry->rbnode, root);
 346	return 0;
 347}
 348
 349static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry)
 350{
 351	if (!RB_EMPTY_NODE(&entry->rbnode)) {
 352		rb_erase(&entry->rbnode, root);
 353		RB_CLEAR_NODE(&entry->rbnode);
 354	}
 355}
 356
 357/*
 358 * Carries out the common pattern of freeing and entry's zpool allocation,
 359 * freeing the entry itself, and decrementing the number of stored pages.
 360 */
 361static void zswap_free_entry(struct zswap_entry *entry)
 362{
 363	if (entry->objcg) {
 364		obj_cgroup_uncharge_zswap(entry->objcg, entry->length);
 365		obj_cgroup_put(entry->objcg);
 366	}
 367	if (!entry->length)
 368		atomic_dec(&zswap_same_filled_pages);
 369	else {
 370		zpool_free(entry->pool->zpool, entry->handle);
 371		zswap_pool_put(entry->pool);
 372	}
 373	zswap_entry_cache_free(entry);
 374	atomic_dec(&zswap_stored_pages);
 375	zswap_update_total_size();
 376}
 377
 378/* caller must hold the tree lock */
 379static void zswap_entry_get(struct zswap_entry *entry)
 380{
 381	entry->refcount++;
 382}
 383
 384/* caller must hold the tree lock
 385* remove from the tree and free it, if nobody reference the entry
 386*/
 387static void zswap_entry_put(struct zswap_tree *tree,
 388			struct zswap_entry *entry)
 389{
 390	int refcount = --entry->refcount;
 391
 392	BUG_ON(refcount < 0);
 393	if (refcount == 0) {
 394		zswap_rb_erase(&tree->rbroot, entry);
 395		zswap_free_entry(entry);
 396	}
 397}
 398
 399/* caller must hold the tree lock */
 400static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
 401				pgoff_t offset)
 402{
 403	struct zswap_entry *entry;
 404
 405	entry = zswap_rb_search(root, offset);
 406	if (entry)
 407		zswap_entry_get(entry);
 408
 409	return entry;
 410}
 411
 412/*********************************
 413* per-cpu code
 414**********************************/
 415static DEFINE_PER_CPU(u8 *, zswap_dstmem);
 416/*
 417 * If users dynamically change the zpool type and compressor at runtime, i.e.
 418 * zswap is running, zswap can have more than one zpool on one cpu, but they
 419 * are sharing dtsmem. So we need this mutex to be per-cpu.
 420 */
 421static DEFINE_PER_CPU(struct mutex *, zswap_mutex);
 422
 423static int zswap_dstmem_prepare(unsigned int cpu)
 424{
 425	struct mutex *mutex;
 426	u8 *dst;
 427
 428	dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
 429	if (!dst)
 430		return -ENOMEM;
 431
 432	mutex = kmalloc_node(sizeof(*mutex), GFP_KERNEL, cpu_to_node(cpu));
 433	if (!mutex) {
 434		kfree(dst);
 435		return -ENOMEM;
 436	}
 437
 438	mutex_init(mutex);
 439	per_cpu(zswap_dstmem, cpu) = dst;
 440	per_cpu(zswap_mutex, cpu) = mutex;
 441	return 0;
 442}
 443
 444static int zswap_dstmem_dead(unsigned int cpu)
 445{
 446	struct mutex *mutex;
 447	u8 *dst;
 448
 449	mutex = per_cpu(zswap_mutex, cpu);
 450	kfree(mutex);
 451	per_cpu(zswap_mutex, cpu) = NULL;
 452
 453	dst = per_cpu(zswap_dstmem, cpu);
 454	kfree(dst);
 455	per_cpu(zswap_dstmem, cpu) = NULL;
 456
 457	return 0;
 458}
 459
 460static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node)
 461{
 462	struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 463	struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
 464	struct crypto_acomp *acomp;
 465	struct acomp_req *req;
 466
 467	acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu));
 468	if (IS_ERR(acomp)) {
 469		pr_err("could not alloc crypto acomp %s : %ld\n",
 470				pool->tfm_name, PTR_ERR(acomp));
 471		return PTR_ERR(acomp);
 472	}
 473	acomp_ctx->acomp = acomp;
 474
 475	req = acomp_request_alloc(acomp_ctx->acomp);
 476	if (!req) {
 477		pr_err("could not alloc crypto acomp_request %s\n",
 478		       pool->tfm_name);
 479		crypto_free_acomp(acomp_ctx->acomp);
 480		return -ENOMEM;
 481	}
 482	acomp_ctx->req = req;
 483
 484	crypto_init_wait(&acomp_ctx->wait);
 485	/*
 486	 * if the backend of acomp is async zip, crypto_req_done() will wakeup
 487	 * crypto_wait_req(); if the backend of acomp is scomp, the callback
 488	 * won't be called, crypto_wait_req() will return without blocking.
 489	 */
 490	acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
 491				   crypto_req_done, &acomp_ctx->wait);
 492
 493	acomp_ctx->mutex = per_cpu(zswap_mutex, cpu);
 494	acomp_ctx->dstmem = per_cpu(zswap_dstmem, cpu);
 495
 496	return 0;
 497}
 498
 499static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node)
 500{
 501	struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node);
 502	struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu);
 503
 504	if (!IS_ERR_OR_NULL(acomp_ctx)) {
 505		if (!IS_ERR_OR_NULL(acomp_ctx->req))
 506			acomp_request_free(acomp_ctx->req);
 507		if (!IS_ERR_OR_NULL(acomp_ctx->acomp))
 508			crypto_free_acomp(acomp_ctx->acomp);
 509	}
 510
 
 
 
 
 511	return 0;
 512}
 513
 514/*********************************
 515* pool functions
 516**********************************/
 517
 518static struct zswap_pool *__zswap_pool_current(void)
 519{
 520	struct zswap_pool *pool;
 521
 522	pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list);
 523	WARN_ONCE(!pool && zswap_has_pool,
 524		  "%s: no page storage pool!\n", __func__);
 525
 526	return pool;
 527}
 528
 529static struct zswap_pool *zswap_pool_current(void)
 530{
 531	assert_spin_locked(&zswap_pools_lock);
 532
 533	return __zswap_pool_current();
 534}
 535
 536static struct zswap_pool *zswap_pool_current_get(void)
 537{
 538	struct zswap_pool *pool;
 539
 540	rcu_read_lock();
 541
 542	pool = __zswap_pool_current();
 543	if (!zswap_pool_get(pool))
 544		pool = NULL;
 545
 546	rcu_read_unlock();
 547
 548	return pool;
 549}
 550
 551static struct zswap_pool *zswap_pool_last_get(void)
 552{
 553	struct zswap_pool *pool, *last = NULL;
 554
 555	rcu_read_lock();
 556
 557	list_for_each_entry_rcu(pool, &zswap_pools, list)
 558		last = pool;
 559	WARN_ONCE(!last && zswap_has_pool,
 560		  "%s: no page storage pool!\n", __func__);
 561	if (!zswap_pool_get(last))
 562		last = NULL;
 563
 564	rcu_read_unlock();
 565
 566	return last;
 567}
 568
 569/* type and compressor must be null-terminated */
 570static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
 571{
 572	struct zswap_pool *pool;
 573
 574	assert_spin_locked(&zswap_pools_lock);
 575
 576	list_for_each_entry_rcu(pool, &zswap_pools, list) {
 577		if (strcmp(pool->tfm_name, compressor))
 578			continue;
 579		if (strcmp(zpool_get_type(pool->zpool), type))
 580			continue;
 581		/* if we can't get it, it's about to be destroyed */
 582		if (!zswap_pool_get(pool))
 583			continue;
 584		return pool;
 585	}
 586
 587	return NULL;
 588}
 589
 590static void shrink_worker(struct work_struct *w)
 591{
 592	struct zswap_pool *pool = container_of(w, typeof(*pool),
 593						shrink_work);
 594
 595	if (zpool_shrink(pool->zpool, 1, NULL))
 596		zswap_reject_reclaim_fail++;
 597	zswap_pool_put(pool);
 598}
 599
 600static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
 601{
 602	struct zswap_pool *pool;
 603	char name[38]; /* 'zswap' + 32 char (max) num + \0 */
 604	gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
 605	int ret;
 606
 607	if (!zswap_has_pool) {
 608		/* if either are unset, pool initialization failed, and we
 609		 * need both params to be set correctly before trying to
 610		 * create a pool.
 611		 */
 612		if (!strcmp(type, ZSWAP_PARAM_UNSET))
 613			return NULL;
 614		if (!strcmp(compressor, ZSWAP_PARAM_UNSET))
 615			return NULL;
 616	}
 617
 618	pool = kzalloc(sizeof(*pool), GFP_KERNEL);
 619	if (!pool)
 620		return NULL;
 621
 622	/* unique name for each pool specifically required by zsmalloc */
 623	snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count));
 624
 625	pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops);
 626	if (!pool->zpool) {
 627		pr_err("%s zpool not available\n", type);
 628		goto error;
 629	}
 630	pr_debug("using %s zpool\n", zpool_get_type(pool->zpool));
 631
 632	strscpy(pool->tfm_name, compressor, sizeof(pool->tfm_name));
 633
 634	pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx);
 635	if (!pool->acomp_ctx) {
 636		pr_err("percpu alloc failed\n");
 637		goto error;
 638	}
 639
 640	ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE,
 641				       &pool->node);
 642	if (ret)
 643		goto error;
 644	pr_debug("using %s compressor\n", pool->tfm_name);
 645
 646	/* being the current pool takes 1 ref; this func expects the
 647	 * caller to always add the new pool as the current pool
 648	 */
 649	kref_init(&pool->kref);
 650	INIT_LIST_HEAD(&pool->list);
 651	INIT_WORK(&pool->shrink_work, shrink_worker);
 652
 653	zswap_pool_debug("created", pool);
 654
 655	return pool;
 656
 657error:
 658	if (pool->acomp_ctx)
 659		free_percpu(pool->acomp_ctx);
 660	if (pool->zpool)
 661		zpool_destroy_pool(pool->zpool);
 662	kfree(pool);
 663	return NULL;
 664}
 665
 666static __init struct zswap_pool *__zswap_pool_create_fallback(void)
 667{
 668	bool has_comp, has_zpool;
 669
 670	has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
 671	if (!has_comp && strcmp(zswap_compressor,
 672				CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {
 673		pr_err("compressor %s not available, using default %s\n",
 674		       zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);
 675		param_free_charp(&zswap_compressor);
 676		zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;
 677		has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
 678	}
 679	if (!has_comp) {
 680		pr_err("default compressor %s not available\n",
 681		       zswap_compressor);
 682		param_free_charp(&zswap_compressor);
 683		zswap_compressor = ZSWAP_PARAM_UNSET;
 684	}
 685
 686	has_zpool = zpool_has_pool(zswap_zpool_type);
 687	if (!has_zpool && strcmp(zswap_zpool_type,
 688				 CONFIG_ZSWAP_ZPOOL_DEFAULT)) {
 689		pr_err("zpool %s not available, using default %s\n",
 690		       zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);
 691		param_free_charp(&zswap_zpool_type);
 692		zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;
 693		has_zpool = zpool_has_pool(zswap_zpool_type);
 694	}
 695	if (!has_zpool) {
 696		pr_err("default zpool %s not available\n",
 697		       zswap_zpool_type);
 698		param_free_charp(&zswap_zpool_type);
 699		zswap_zpool_type = ZSWAP_PARAM_UNSET;
 700	}
 701
 702	if (!has_comp || !has_zpool)
 703		return NULL;
 704
 705	return zswap_pool_create(zswap_zpool_type, zswap_compressor);
 706}
 707
 708static void zswap_pool_destroy(struct zswap_pool *pool)
 709{
 710	zswap_pool_debug("destroying", pool);
 711
 712	cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
 713	free_percpu(pool->acomp_ctx);
 714	zpool_destroy_pool(pool->zpool);
 715	kfree(pool);
 716}
 717
 718static int __must_check zswap_pool_get(struct zswap_pool *pool)
 719{
 720	if (!pool)
 721		return 0;
 722
 723	return kref_get_unless_zero(&pool->kref);
 724}
 725
 726static void __zswap_pool_release(struct work_struct *work)
 727{
 728	struct zswap_pool *pool = container_of(work, typeof(*pool),
 729						release_work);
 730
 731	synchronize_rcu();
 732
 733	/* nobody should have been able to get a kref... */
 734	WARN_ON(kref_get_unless_zero(&pool->kref));
 735
 736	/* pool is now off zswap_pools list and has no references. */
 737	zswap_pool_destroy(pool);
 738}
 739
 740static void __zswap_pool_empty(struct kref *kref)
 741{
 742	struct zswap_pool *pool;
 743
 744	pool = container_of(kref, typeof(*pool), kref);
 745
 746	spin_lock(&zswap_pools_lock);
 747
 748	WARN_ON(pool == zswap_pool_current());
 749
 750	list_del_rcu(&pool->list);
 751
 752	INIT_WORK(&pool->release_work, __zswap_pool_release);
 753	schedule_work(&pool->release_work);
 754
 755	spin_unlock(&zswap_pools_lock);
 756}
 757
 758static void zswap_pool_put(struct zswap_pool *pool)
 759{
 760	kref_put(&pool->kref, __zswap_pool_empty);
 761}
 762
 763/*********************************
 764* param callbacks
 765**********************************/
 766
 767/* val must be a null-terminated string */
 768static int __zswap_param_set(const char *val, const struct kernel_param *kp,
 769			     char *type, char *compressor)
 770{
 771	struct zswap_pool *pool, *put_pool = NULL;
 772	char *s = strstrip((char *)val);
 773	int ret;
 774
 775	if (zswap_init_failed) {
 776		pr_err("can't set param, initialization failed\n");
 777		return -ENODEV;
 778	}
 779
 780	/* no change required */
 781	if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
 782		return 0;
 783
 784	/* if this is load-time (pre-init) param setting,
 785	 * don't create a pool; that's done during init.
 786	 */
 787	if (!zswap_init_started)
 788		return param_set_charp(s, kp);
 789
 790	if (!type) {
 791		if (!zpool_has_pool(s)) {
 792			pr_err("zpool %s not available\n", s);
 793			return -ENOENT;
 794		}
 795		type = s;
 796	} else if (!compressor) {
 797		if (!crypto_has_acomp(s, 0, 0)) {
 798			pr_err("compressor %s not available\n", s);
 799			return -ENOENT;
 800		}
 801		compressor = s;
 802	} else {
 803		WARN_ON(1);
 804		return -EINVAL;
 805	}
 806
 807	spin_lock(&zswap_pools_lock);
 808
 809	pool = zswap_pool_find_get(type, compressor);
 810	if (pool) {
 811		zswap_pool_debug("using existing", pool);
 812		WARN_ON(pool == zswap_pool_current());
 813		list_del_rcu(&pool->list);
 814	}
 815
 816	spin_unlock(&zswap_pools_lock);
 817
 818	if (!pool)
 819		pool = zswap_pool_create(type, compressor);
 820
 821	if (pool)
 822		ret = param_set_charp(s, kp);
 823	else
 824		ret = -EINVAL;
 825
 826	spin_lock(&zswap_pools_lock);
 827
 828	if (!ret) {
 829		put_pool = zswap_pool_current();
 830		list_add_rcu(&pool->list, &zswap_pools);
 831		zswap_has_pool = true;
 832	} else if (pool) {
 833		/* add the possibly pre-existing pool to the end of the pools
 834		 * list; if it's new (and empty) then it'll be removed and
 835		 * destroyed by the put after we drop the lock
 836		 */
 837		list_add_tail_rcu(&pool->list, &zswap_pools);
 838		put_pool = pool;
 839	}
 840
 841	spin_unlock(&zswap_pools_lock);
 842
 843	if (!zswap_has_pool && !pool) {
 844		/* if initial pool creation failed, and this pool creation also
 845		 * failed, maybe both compressor and zpool params were bad.
 846		 * Allow changing this param, so pool creation will succeed
 847		 * when the other param is changed. We already verified this
 848		 * param is ok in the zpool_has_pool() or crypto_has_acomp()
 849		 * checks above.
 850		 */
 851		ret = param_set_charp(s, kp);
 852	}
 853
 854	/* drop the ref from either the old current pool,
 855	 * or the new pool we failed to add
 856	 */
 857	if (put_pool)
 858		zswap_pool_put(put_pool);
 859
 860	return ret;
 861}
 862
 863static int zswap_compressor_param_set(const char *val,
 864				      const struct kernel_param *kp)
 865{
 866	return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
 867}
 868
 869static int zswap_zpool_param_set(const char *val,
 870				 const struct kernel_param *kp)
 871{
 872	return __zswap_param_set(val, kp, NULL, zswap_compressor);
 873}
 874
 875static int zswap_enabled_param_set(const char *val,
 876				   const struct kernel_param *kp)
 877{
 878	if (zswap_init_failed) {
 879		pr_err("can't enable, initialization failed\n");
 880		return -ENODEV;
 881	}
 882	if (!zswap_has_pool && zswap_init_started) {
 883		pr_err("can't enable, no pool configured\n");
 884		return -ENODEV;
 885	}
 886
 887	return param_set_bool(val, kp);
 888}
 889
 890/*********************************
 891* writeback code
 892**********************************/
 893/* return enum for zswap_get_swap_cache_page */
 894enum zswap_get_swap_ret {
 895	ZSWAP_SWAPCACHE_NEW,
 896	ZSWAP_SWAPCACHE_EXIST,
 897	ZSWAP_SWAPCACHE_FAIL,
 898};
 899
 900/*
 901 * zswap_get_swap_cache_page
 902 *
 903 * This is an adaption of read_swap_cache_async()
 904 *
 905 * This function tries to find a page with the given swap entry
 906 * in the swapper_space address space (the swap cache).  If the page
 907 * is found, it is returned in retpage.  Otherwise, a page is allocated,
 908 * added to the swap cache, and returned in retpage.
 909 *
 910 * If success, the swap cache page is returned in retpage
 911 * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache
 912 * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated,
 913 *     the new page is added to swapcache and locked
 914 * Returns ZSWAP_SWAPCACHE_FAIL on error
 915 */
 916static int zswap_get_swap_cache_page(swp_entry_t entry,
 917				struct page **retpage)
 918{
 919	bool page_was_allocated;
 920
 921	*retpage = __read_swap_cache_async(entry, GFP_KERNEL,
 922			NULL, 0, &page_was_allocated);
 923	if (page_was_allocated)
 924		return ZSWAP_SWAPCACHE_NEW;
 925	if (!*retpage)
 926		return ZSWAP_SWAPCACHE_FAIL;
 927	return ZSWAP_SWAPCACHE_EXIST;
 928}
 929
 930/*
 931 * Attempts to free an entry by adding a page to the swap cache,
 932 * decompressing the entry data into the page, and issuing a
 933 * bio write to write the page back to the swap device.
 934 *
 935 * This can be thought of as a "resumed writeback" of the page
 936 * to the swap device.  We are basically resuming the same swap
 937 * writeback path that was intercepted with the frontswap_store()
 938 * in the first place.  After the page has been decompressed into
 939 * the swap cache, the compressed version stored by zswap can be
 940 * freed.
 941 */
 942static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 943{
 944	struct zswap_header *zhdr;
 945	swp_entry_t swpentry;
 946	struct zswap_tree *tree;
 947	pgoff_t offset;
 948	struct zswap_entry *entry;
 949	struct page *page;
 950	struct scatterlist input, output;
 951	struct crypto_acomp_ctx *acomp_ctx;
 952
 953	u8 *src, *tmp = NULL;
 954	unsigned int dlen;
 955	int ret;
 956	struct writeback_control wbc = {
 957		.sync_mode = WB_SYNC_NONE,
 958	};
 959
 960	if (!zpool_can_sleep_mapped(pool)) {
 961		tmp = kmalloc(PAGE_SIZE, GFP_KERNEL);
 962		if (!tmp)
 963			return -ENOMEM;
 964	}
 965
 966	/* extract swpentry from data */
 967	zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
 968	swpentry = zhdr->swpentry; /* here */
 969	tree = zswap_trees[swp_type(swpentry)];
 970	offset = swp_offset(swpentry);
 971	zpool_unmap_handle(pool, handle);
 972
 973	/* find and ref zswap entry */
 974	spin_lock(&tree->lock);
 975	entry = zswap_entry_find_get(&tree->rbroot, offset);
 976	if (!entry) {
 977		/* entry was invalidated */
 978		spin_unlock(&tree->lock);
 979		kfree(tmp);
 980		return 0;
 981	}
 982	spin_unlock(&tree->lock);
 983	BUG_ON(offset != entry->offset);
 984
 985	/* try to allocate swap cache page */
 986	switch (zswap_get_swap_cache_page(swpentry, &page)) {
 987	case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
 988		ret = -ENOMEM;
 989		goto fail;
 990
 991	case ZSWAP_SWAPCACHE_EXIST:
 992		/* page is already in the swap cache, ignore for now */
 993		put_page(page);
 994		ret = -EEXIST;
 995		goto fail;
 996
 997	case ZSWAP_SWAPCACHE_NEW: /* page is locked */
 998		/* decompress */
 999		acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1000		dlen = PAGE_SIZE;
1001
1002		zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO);
1003		src = (u8 *)zhdr + sizeof(struct zswap_header);
1004		if (!zpool_can_sleep_mapped(pool)) {
1005			memcpy(tmp, src, entry->length);
1006			src = tmp;
1007			zpool_unmap_handle(pool, handle);
1008		}
1009
1010		mutex_lock(acomp_ctx->mutex);
1011		sg_init_one(&input, src, entry->length);
1012		sg_init_table(&output, 1);
1013		sg_set_page(&output, page, PAGE_SIZE, 0);
1014		acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1015		ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1016		dlen = acomp_ctx->req->dlen;
1017		mutex_unlock(acomp_ctx->mutex);
1018
1019		if (!zpool_can_sleep_mapped(pool))
1020			kfree(tmp);
1021		else
1022			zpool_unmap_handle(pool, handle);
1023
1024		BUG_ON(ret);
1025		BUG_ON(dlen != PAGE_SIZE);
1026
1027		/* page is up to date */
1028		SetPageUptodate(page);
1029	}
1030
1031	/* move it to the tail of the inactive list after end_writeback */
1032	SetPageReclaim(page);
1033
1034	/* start writeback */
1035	__swap_writepage(page, &wbc);
1036	put_page(page);
1037	zswap_written_back_pages++;
1038
1039	spin_lock(&tree->lock);
1040	/* drop local reference */
1041	zswap_entry_put(tree, entry);
1042
1043	/*
1044	* There are two possible situations for entry here:
1045	* (1) refcount is 1(normal case),  entry is valid and on the tree
1046	* (2) refcount is 0, entry is freed and not on the tree
1047	*     because invalidate happened during writeback
1048	*  search the tree and free the entry if find entry
1049	*/
1050	if (entry == zswap_rb_search(&tree->rbroot, offset))
1051		zswap_entry_put(tree, entry);
1052	spin_unlock(&tree->lock);
1053
1054	return ret;
1055
1056fail:
1057	if (!zpool_can_sleep_mapped(pool))
1058		kfree(tmp);
1059
1060	/*
1061	* if we get here due to ZSWAP_SWAPCACHE_EXIST
1062	* a load may be happening concurrently.
1063	* it is safe and okay to not free the entry.
1064	* if we free the entry in the following put
1065	* it is also okay to return !0
1066	*/
 
1067	spin_lock(&tree->lock);
1068	zswap_entry_put(tree, entry);
1069	spin_unlock(&tree->lock);
1070
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1071	return ret;
1072}
1073
1074static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
1075{
1076	unsigned int pos;
1077	unsigned long *page;
1078
1079	page = (unsigned long *)ptr;
1080	for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) {
1081		if (page[pos] != page[0])
1082			return 0;
1083	}
1084	*value = page[0];
1085	return 1;
1086}
1087
1088static void zswap_fill_page(void *ptr, unsigned long value)
1089{
1090	unsigned long *page;
1091
1092	page = (unsigned long *)ptr;
1093	memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
1094}
1095
1096/*********************************
1097* frontswap hooks
1098**********************************/
1099/* attempts to compress and store an single page */
1100static int zswap_frontswap_store(unsigned type, pgoff_t offset,
1101				struct page *page)
1102{
1103	struct zswap_tree *tree = zswap_trees[type];
1104	struct zswap_entry *entry, *dupentry;
1105	struct scatterlist input, output;
1106	struct crypto_acomp_ctx *acomp_ctx;
1107	struct obj_cgroup *objcg = NULL;
1108	struct zswap_pool *pool;
1109	int ret;
1110	unsigned int hlen, dlen = PAGE_SIZE;
1111	unsigned long handle, value;
1112	char *buf;
1113	u8 *src, *dst;
1114	struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
1115	gfp_t gfp;
1116
1117	/* THP isn't supported */
1118	if (PageTransHuge(page)) {
1119		ret = -EINVAL;
1120		goto reject;
1121	}
1122
1123	if (!zswap_enabled || !tree) {
1124		ret = -ENODEV;
1125		goto reject;
1126	}
1127
1128	objcg = get_obj_cgroup_from_page(page);
1129	if (objcg && !obj_cgroup_may_zswap(objcg))
1130		goto shrink;
1131
1132	/* reclaim space if needed */
1133	if (zswap_is_full()) {
1134		zswap_pool_limit_hit++;
1135		zswap_pool_reached_full = true;
1136		goto shrink;
1137	}
 
 
1138
1139	if (zswap_pool_reached_full) {
1140	       if (!zswap_can_accept()) {
 
 
 
1141			ret = -ENOMEM;
1142			goto reject;
1143		} else
1144			zswap_pool_reached_full = false;
1145	}
1146
1147	/* allocate entry */
1148	entry = zswap_entry_cache_alloc(GFP_KERNEL);
1149	if (!entry) {
1150		zswap_reject_kmemcache_fail++;
1151		ret = -ENOMEM;
1152		goto reject;
1153	}
1154
1155	if (zswap_same_filled_pages_enabled) {
1156		src = kmap_atomic(page);
1157		if (zswap_is_page_same_filled(src, &value)) {
1158			kunmap_atomic(src);
1159			entry->offset = offset;
1160			entry->length = 0;
1161			entry->value = value;
1162			atomic_inc(&zswap_same_filled_pages);
1163			goto insert_entry;
1164		}
1165		kunmap_atomic(src);
1166	}
1167
1168	if (!zswap_non_same_filled_pages_enabled) {
1169		ret = -EINVAL;
1170		goto freepage;
1171	}
1172
1173	/* if entry is successfully added, it keeps the reference */
1174	entry->pool = zswap_pool_current_get();
1175	if (!entry->pool) {
1176		ret = -EINVAL;
1177		goto freepage;
1178	}
1179
1180	/* compress */
1181	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1182
1183	mutex_lock(acomp_ctx->mutex);
1184
1185	dst = acomp_ctx->dstmem;
1186	sg_init_table(&input, 1);
1187	sg_set_page(&input, page, PAGE_SIZE, 0);
1188
1189	/* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */
1190	sg_init_one(&output, dst, PAGE_SIZE * 2);
1191	acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen);
1192	/*
1193	 * it maybe looks a little bit silly that we send an asynchronous request,
1194	 * then wait for its completion synchronously. This makes the process look
1195	 * synchronous in fact.
1196	 * Theoretically, acomp supports users send multiple acomp requests in one
1197	 * acomp instance, then get those requests done simultaneously. but in this
1198	 * case, frontswap actually does store and load page by page, there is no
1199	 * existing method to send the second page before the first page is done
1200	 * in one thread doing frontswap.
1201	 * but in different threads running on different cpu, we have different
1202	 * acomp instance, so multiple threads can do (de)compression in parallel.
1203	 */
1204	ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
1205	dlen = acomp_ctx->req->dlen;
1206
1207	if (ret) {
1208		ret = -EINVAL;
1209		goto put_dstmem;
1210	}
1211
1212	/* store */
1213	hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0;
1214	gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
1215	if (zpool_malloc_support_movable(entry->pool->zpool))
1216		gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
1217	ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle);
1218	if (ret == -ENOSPC) {
1219		zswap_reject_compress_poor++;
1220		goto put_dstmem;
1221	}
1222	if (ret) {
1223		zswap_reject_alloc_fail++;
1224		goto put_dstmem;
1225	}
1226	buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_WO);
1227	memcpy(buf, &zhdr, hlen);
1228	memcpy(buf + hlen, dst, dlen);
1229	zpool_unmap_handle(entry->pool->zpool, handle);
1230	mutex_unlock(acomp_ctx->mutex);
1231
1232	/* populate entry */
1233	entry->offset = offset;
1234	entry->handle = handle;
1235	entry->length = dlen;
1236
1237insert_entry:
1238	entry->objcg = objcg;
1239	if (objcg) {
1240		obj_cgroup_charge_zswap(objcg, entry->length);
1241		/* Account before objcg ref is moved to tree */
1242		count_objcg_event(objcg, ZSWPOUT);
1243	}
1244
1245	/* map */
1246	spin_lock(&tree->lock);
1247	do {
1248		ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry);
1249		if (ret == -EEXIST) {
1250			zswap_duplicate_entry++;
1251			/* remove from rbtree */
1252			zswap_rb_erase(&tree->rbroot, dupentry);
1253			zswap_entry_put(tree, dupentry);
1254		}
1255	} while (ret == -EEXIST);
1256	spin_unlock(&tree->lock);
1257
1258	/* update stats */
1259	atomic_inc(&zswap_stored_pages);
1260	zswap_update_total_size();
1261	count_vm_event(ZSWPOUT);
1262
1263	return 0;
1264
1265put_dstmem:
1266	mutex_unlock(acomp_ctx->mutex);
1267	zswap_pool_put(entry->pool);
1268freepage:
1269	zswap_entry_cache_free(entry);
1270reject:
1271	if (objcg)
1272		obj_cgroup_put(objcg);
1273	return ret;
1274
1275shrink:
1276	pool = zswap_pool_last_get();
1277	if (pool)
1278		queue_work(shrink_wq, &pool->shrink_work);
1279	ret = -ENOMEM;
1280	goto reject;
1281}
1282
1283/*
1284 * returns 0 if the page was successfully decompressed
1285 * return -1 on entry not found or error
1286*/
1287static int zswap_frontswap_load(unsigned type, pgoff_t offset,
1288				struct page *page)
1289{
1290	struct zswap_tree *tree = zswap_trees[type];
1291	struct zswap_entry *entry;
1292	struct scatterlist input, output;
1293	struct crypto_acomp_ctx *acomp_ctx;
1294	u8 *src, *dst, *tmp;
1295	unsigned int dlen;
1296	int ret;
1297
1298	/* find */
1299	spin_lock(&tree->lock);
1300	entry = zswap_entry_find_get(&tree->rbroot, offset);
1301	if (!entry) {
1302		/* entry was written back */
1303		spin_unlock(&tree->lock);
1304		return -1;
1305	}
1306	spin_unlock(&tree->lock);
1307
1308	if (!entry->length) {
1309		dst = kmap_atomic(page);
1310		zswap_fill_page(dst, entry->value);
1311		kunmap_atomic(dst);
1312		ret = 0;
1313		goto stats;
1314	}
1315
1316	if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1317		tmp = kmalloc(entry->length, GFP_KERNEL);
1318		if (!tmp) {
1319			ret = -ENOMEM;
1320			goto freeentry;
1321		}
1322	}
1323
1324	/* decompress */
1325	dlen = PAGE_SIZE;
1326	src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO);
1327	if (zpool_evictable(entry->pool->zpool))
1328		src += sizeof(struct zswap_header);
 
 
 
 
 
 
 
1329
1330	if (!zpool_can_sleep_mapped(entry->pool->zpool)) {
1331		memcpy(tmp, src, entry->length);
1332		src = tmp;
1333		zpool_unmap_handle(entry->pool->zpool, entry->handle);
1334	}
1335
1336	acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
1337	mutex_lock(acomp_ctx->mutex);
1338	sg_init_one(&input, src, entry->length);
1339	sg_init_table(&output, 1);
1340	sg_set_page(&output, page, PAGE_SIZE, 0);
1341	acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen);
1342	ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait);
1343	mutex_unlock(acomp_ctx->mutex);
1344
1345	if (zpool_can_sleep_mapped(entry->pool->zpool))
1346		zpool_unmap_handle(entry->pool->zpool, entry->handle);
1347	else
1348		kfree(tmp);
1349
1350	BUG_ON(ret);
1351stats:
1352	count_vm_event(ZSWPIN);
1353	if (entry->objcg)
1354		count_objcg_event(entry->objcg, ZSWPIN);
1355freeentry:
1356	spin_lock(&tree->lock);
1357	zswap_entry_put(tree, entry);
1358	spin_unlock(&tree->lock);
1359
1360	return ret;
1361}
1362
1363/* frees an entry in zswap */
1364static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset)
1365{
1366	struct zswap_tree *tree = zswap_trees[type];
1367	struct zswap_entry *entry;
1368
1369	/* find */
1370	spin_lock(&tree->lock);
1371	entry = zswap_rb_search(&tree->rbroot, offset);
1372	if (!entry) {
1373		/* entry was written back */
1374		spin_unlock(&tree->lock);
1375		return;
1376	}
1377
1378	/* remove from rbtree */
1379	zswap_rb_erase(&tree->rbroot, entry);
1380
1381	/* drop the initial reference from entry creation */
1382	zswap_entry_put(tree, entry);
1383
1384	spin_unlock(&tree->lock);
1385}
1386
1387/* frees all zswap entries for the given swap type */
1388static void zswap_frontswap_invalidate_area(unsigned type)
1389{
1390	struct zswap_tree *tree = zswap_trees[type];
1391	struct zswap_entry *entry, *n;
1392
1393	if (!tree)
1394		return;
1395
1396	/* walk the tree and free everything */
1397	spin_lock(&tree->lock);
1398	rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode)
1399		zswap_free_entry(entry);
1400	tree->rbroot = RB_ROOT;
1401	spin_unlock(&tree->lock);
1402	kfree(tree);
1403	zswap_trees[type] = NULL;
1404}
1405
1406static void zswap_frontswap_init(unsigned type)
1407{
1408	struct zswap_tree *tree;
1409
1410	tree = kzalloc(sizeof(*tree), GFP_KERNEL);
1411	if (!tree) {
1412		pr_err("alloc failed, zswap disabled for swap type %d\n", type);
1413		return;
1414	}
1415
1416	tree->rbroot = RB_ROOT;
1417	spin_lock_init(&tree->lock);
1418	zswap_trees[type] = tree;
1419}
1420
1421static const struct frontswap_ops zswap_frontswap_ops = {
1422	.store = zswap_frontswap_store,
1423	.load = zswap_frontswap_load,
1424	.invalidate_page = zswap_frontswap_invalidate_page,
1425	.invalidate_area = zswap_frontswap_invalidate_area,
1426	.init = zswap_frontswap_init
1427};
1428
1429/*********************************
1430* debugfs functions
1431**********************************/
1432#ifdef CONFIG_DEBUG_FS
1433#include <linux/debugfs.h>
1434
1435static struct dentry *zswap_debugfs_root;
1436
1437static int __init zswap_debugfs_init(void)
1438{
1439	if (!debugfs_initialized())
1440		return -ENODEV;
1441
1442	zswap_debugfs_root = debugfs_create_dir("zswap", NULL);
1443
1444	debugfs_create_u64("pool_limit_hit", 0444,
1445			   zswap_debugfs_root, &zswap_pool_limit_hit);
1446	debugfs_create_u64("reject_reclaim_fail", 0444,
1447			   zswap_debugfs_root, &zswap_reject_reclaim_fail);
1448	debugfs_create_u64("reject_alloc_fail", 0444,
1449			   zswap_debugfs_root, &zswap_reject_alloc_fail);
1450	debugfs_create_u64("reject_kmemcache_fail", 0444,
1451			   zswap_debugfs_root, &zswap_reject_kmemcache_fail);
1452	debugfs_create_u64("reject_compress_poor", 0444,
1453			   zswap_debugfs_root, &zswap_reject_compress_poor);
1454	debugfs_create_u64("written_back_pages", 0444,
1455			   zswap_debugfs_root, &zswap_written_back_pages);
1456	debugfs_create_u64("duplicate_entry", 0444,
1457			   zswap_debugfs_root, &zswap_duplicate_entry);
1458	debugfs_create_u64("pool_total_size", 0444,
1459			   zswap_debugfs_root, &zswap_pool_total_size);
1460	debugfs_create_atomic_t("stored_pages", 0444,
1461				zswap_debugfs_root, &zswap_stored_pages);
1462	debugfs_create_atomic_t("same_filled_pages", 0444,
1463				zswap_debugfs_root, &zswap_same_filled_pages);
1464
1465	return 0;
1466}
 
 
 
 
 
1467#else
1468static int __init zswap_debugfs_init(void)
1469{
1470	return 0;
1471}
 
 
1472#endif
1473
1474/*********************************
1475* module init and exit
1476**********************************/
1477static int __init init_zswap(void)
1478{
1479	struct zswap_pool *pool;
1480	int ret;
1481
1482	zswap_init_started = true;
1483
1484	if (zswap_entry_cache_create()) {
1485		pr_err("entry cache creation failed\n");
1486		goto cache_fail;
1487	}
1488
1489	ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare",
1490				zswap_dstmem_prepare, zswap_dstmem_dead);
1491	if (ret) {
1492		pr_err("dstmem alloc failed\n");
1493		goto dstmem_fail;
1494	}
1495
1496	ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE,
1497				      "mm/zswap_pool:prepare",
1498				      zswap_cpu_comp_prepare,
1499				      zswap_cpu_comp_dead);
1500	if (ret)
1501		goto hp_fail;
1502
1503	pool = __zswap_pool_create_fallback();
1504	if (pool) {
1505		pr_info("loaded using pool %s/%s\n", pool->tfm_name,
1506			zpool_get_type(pool->zpool));
1507		list_add(&pool->list, &zswap_pools);
1508		zswap_has_pool = true;
1509	} else {
1510		pr_err("pool creation failed\n");
1511		zswap_enabled = false;
1512	}
1513
1514	shrink_wq = create_workqueue("zswap-shrink");
1515	if (!shrink_wq)
1516		goto fallback_fail;
1517
1518	ret = frontswap_register_ops(&zswap_frontswap_ops);
1519	if (ret)
1520		goto destroy_wq;
1521	if (zswap_debugfs_init())
1522		pr_warn("debugfs initialization failed\n");
1523	return 0;
1524
1525destroy_wq:
1526	destroy_workqueue(shrink_wq);
1527fallback_fail:
1528	if (pool)
1529		zswap_pool_destroy(pool);
1530hp_fail:
1531	cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
1532dstmem_fail:
1533	zswap_entry_cache_destroy();
1534cache_fail:
1535	/* if built-in, we aren't unloaded on failure; don't allow use */
1536	zswap_init_failed = true;
1537	zswap_enabled = false;
1538	return -ENOMEM;
1539}
1540/* must be late so crypto has time to come up */
1541late_initcall(init_zswap);
1542
1543MODULE_LICENSE("GPL");
1544MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
1545MODULE_DESCRIPTION("Compressed cache for swap pages");