// SPDX-License-Identifier: GPL-2.0-or-later /* * zswap.c - zswap driver file * * zswap is a backend for frontswap that takes pages that are in the process * of being swapped out and attempts to compress and store them in a * RAM-based memory pool. This can result in a significant I/O reduction on * the swap device and, in the case where decompressing from RAM is faster * than reading from the swap device, can also improve workload performance. * * Copyright (C) 2012 Seth Jennings */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "swap.h" /********************************* * statistics **********************************/ /* Total bytes used by the compressed storage */ u64 zswap_pool_total_size; /* The number of compressed pages currently stored in zswap */ atomic_t zswap_stored_pages = ATOMIC_INIT(0); /* The number of same-value filled pages currently stored in zswap */ static atomic_t zswap_same_filled_pages = ATOMIC_INIT(0); /* * The statistics below are not protected from concurrent access for * performance reasons so they may not be a 100% accurate. However, * they do provide useful information on roughly how many times a * certain event is occurring. */ /* Pool limit was hit (see zswap_max_pool_percent) */ static u64 zswap_pool_limit_hit; /* Pages written back when pool limit was reached */ static u64 zswap_written_back_pages; /* Store failed due to a reclaim failure after pool limit was reached */ static u64 zswap_reject_reclaim_fail; /* Compressed page was too big for the allocator to (optimally) store */ static u64 zswap_reject_compress_poor; /* Store failed because underlying allocator could not get memory */ static u64 zswap_reject_alloc_fail; /* Store failed because the entry metadata could not be allocated (rare) */ static u64 zswap_reject_kmemcache_fail; /* Duplicate store was encountered (rare) */ static u64 zswap_duplicate_entry; /* Shrinker work queue */ static struct workqueue_struct *shrink_wq; /* Pool limit was hit, we need to calm down */ static bool zswap_pool_reached_full; /********************************* * tunables **********************************/ #define ZSWAP_PARAM_UNSET "" /* Enable/disable zswap */ static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON); static int zswap_enabled_param_set(const char *, const struct kernel_param *); static const struct kernel_param_ops zswap_enabled_param_ops = { .set = zswap_enabled_param_set, .get = param_get_bool, }; module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644); /* Crypto compressor to use */ static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT; static int zswap_compressor_param_set(const char *, const struct kernel_param *); static const struct kernel_param_ops zswap_compressor_param_ops = { .set = zswap_compressor_param_set, .get = param_get_charp, .free = param_free_charp, }; module_param_cb(compressor, &zswap_compressor_param_ops, &zswap_compressor, 0644); /* Compressed storage zpool to use */ static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT; static int zswap_zpool_param_set(const char *, const struct kernel_param *); static const struct kernel_param_ops zswap_zpool_param_ops = { .set = zswap_zpool_param_set, .get = param_get_charp, .free = param_free_charp, }; module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_type, 0644); /* The maximum percentage of memory that the compressed pool can occupy */ static unsigned int zswap_max_pool_percent = 20; module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644); /* The threshold for accepting new pages after the max_pool_percent was hit */ static unsigned int zswap_accept_thr_percent = 90; /* of max pool size */ module_param_named(accept_threshold_percent, zswap_accept_thr_percent, uint, 0644); /* * Enable/disable handling same-value filled pages (enabled by default). * If disabled every page is considered non-same-value filled. */ static bool zswap_same_filled_pages_enabled = true; module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled, bool, 0644); /* Enable/disable handling non-same-value filled pages (enabled by default) */ static bool zswap_non_same_filled_pages_enabled = true; module_param_named(non_same_filled_pages_enabled, zswap_non_same_filled_pages_enabled, bool, 0644); /********************************* * data structures **********************************/ struct crypto_acomp_ctx { struct crypto_acomp *acomp; struct acomp_req *req; struct crypto_wait wait; u8 *dstmem; struct mutex *mutex; }; struct zswap_pool { struct zpool *zpool; struct crypto_acomp_ctx __percpu *acomp_ctx; struct kref kref; struct list_head list; struct work_struct release_work; struct work_struct shrink_work; struct hlist_node node; char tfm_name[CRYPTO_MAX_ALG_NAME]; }; /* * struct zswap_entry * * This structure contains the metadata for tracking a single compressed * page within zswap. * * rbnode - links the entry into red-black tree for the appropriate swap type * offset - the swap offset for the entry. Index into the red-black tree. * refcount - the number of outstanding reference to the entry. This is needed * to protect against premature freeing of the entry by code * concurrent calls to load, invalidate, and writeback. The lock * for the zswap_tree structure that contains the entry must * be held while changing the refcount. Since the lock must * be held, there is no reason to also make refcount atomic. * length - the length in bytes of the compressed page data. Needed during * decompression. For a same value filled page length is 0. * pool - the zswap_pool the entry's data is in * handle - zpool allocation handle that stores the compressed page data * value - value of the same-value filled pages which have same content */ struct zswap_entry { struct rb_node rbnode; pgoff_t offset; int refcount; unsigned int length; struct zswap_pool *pool; union { unsigned long handle; unsigned long value; }; struct obj_cgroup *objcg; }; struct zswap_header { swp_entry_t swpentry; }; /* * The tree lock in the zswap_tree struct protects a few things: * - the rbtree * - the refcount field of each entry in the tree */ struct zswap_tree { struct rb_root rbroot; spinlock_t lock; }; static struct zswap_tree *zswap_trees[MAX_SWAPFILES]; /* RCU-protected iteration */ static LIST_HEAD(zswap_pools); /* protects zswap_pools list modification */ static DEFINE_SPINLOCK(zswap_pools_lock); /* pool counter to provide unique names to zpool */ static atomic_t zswap_pools_count = ATOMIC_INIT(0); /* used by param callback function */ static bool zswap_init_started; /* fatal error during init */ static bool zswap_init_failed; /* init completed, but couldn't create the initial pool */ static bool zswap_has_pool; /********************************* * helpers and fwd declarations **********************************/ #define zswap_pool_debug(msg, p) \ pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \ zpool_get_type((p)->zpool)) static int zswap_writeback_entry(struct zpool *pool, unsigned long handle); static int zswap_pool_get(struct zswap_pool *pool); static void zswap_pool_put(struct zswap_pool *pool); static const struct zpool_ops zswap_zpool_ops = { .evict = zswap_writeback_entry }; static bool zswap_is_full(void) { return totalram_pages() * zswap_max_pool_percent / 100 < DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE); } static bool zswap_can_accept(void) { return totalram_pages() * zswap_accept_thr_percent / 100 * zswap_max_pool_percent / 100 > DIV_ROUND_UP(zswap_pool_total_size, PAGE_SIZE); } static void zswap_update_total_size(void) { struct zswap_pool *pool; u64 total = 0; rcu_read_lock(); list_for_each_entry_rcu(pool, &zswap_pools, list) total += zpool_get_total_size(pool->zpool); rcu_read_unlock(); zswap_pool_total_size = total; } /********************************* * zswap entry functions **********************************/ static struct kmem_cache *zswap_entry_cache; static int __init zswap_entry_cache_create(void) { zswap_entry_cache = KMEM_CACHE(zswap_entry, 0); return zswap_entry_cache == NULL; } static void __init zswap_entry_cache_destroy(void) { kmem_cache_destroy(zswap_entry_cache); } static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp) { struct zswap_entry *entry; entry = kmem_cache_alloc(zswap_entry_cache, gfp); if (!entry) return NULL; entry->refcount = 1; RB_CLEAR_NODE(&entry->rbnode); return entry; } static void zswap_entry_cache_free(struct zswap_entry *entry) { kmem_cache_free(zswap_entry_cache, entry); } /********************************* * rbtree functions **********************************/ static struct zswap_entry *zswap_rb_search(struct rb_root *root, pgoff_t offset) { struct rb_node *node = root->rb_node; struct zswap_entry *entry; while (node) { entry = rb_entry(node, struct zswap_entry, rbnode); if (entry->offset > offset) node = node->rb_left; else if (entry->offset < offset) node = node->rb_right; else return entry; } return NULL; } /* * In the case that a entry with the same offset is found, a pointer to * the existing entry is stored in dupentry and the function returns -EEXIST */ static int zswap_rb_insert(struct rb_root *root, struct zswap_entry *entry, struct zswap_entry **dupentry) { struct rb_node **link = &root->rb_node, *parent = NULL; struct zswap_entry *myentry; while (*link) { parent = *link; myentry = rb_entry(parent, struct zswap_entry, rbnode); if (myentry->offset > entry->offset) link = &(*link)->rb_left; else if (myentry->offset < entry->offset) link = &(*link)->rb_right; else { *dupentry = myentry; return -EEXIST; } } rb_link_node(&entry->rbnode, parent, link); rb_insert_color(&entry->rbnode, root); return 0; } static void zswap_rb_erase(struct rb_root *root, struct zswap_entry *entry) { if (!RB_EMPTY_NODE(&entry->rbnode)) { rb_erase(&entry->rbnode, root); RB_CLEAR_NODE(&entry->rbnode); } } /* * Carries out the common pattern of freeing and entry's zpool allocation, * freeing the entry itself, and decrementing the number of stored pages. */ static void zswap_free_entry(struct zswap_entry *entry) { if (entry->objcg) { obj_cgroup_uncharge_zswap(entry->objcg, entry->length); obj_cgroup_put(entry->objcg); } if (!entry->length) atomic_dec(&zswap_same_filled_pages); else { zpool_free(entry->pool->zpool, entry->handle); zswap_pool_put(entry->pool); } zswap_entry_cache_free(entry); atomic_dec(&zswap_stored_pages); zswap_update_total_size(); } /* caller must hold the tree lock */ static void zswap_entry_get(struct zswap_entry *entry) { entry->refcount++; } /* caller must hold the tree lock * remove from the tree and free it, if nobody reference the entry */ static void zswap_entry_put(struct zswap_tree *tree, struct zswap_entry *entry) { int refcount = --entry->refcount; BUG_ON(refcount < 0); if (refcount == 0) { zswap_rb_erase(&tree->rbroot, entry); zswap_free_entry(entry); } } /* caller must hold the tree lock */ static struct zswap_entry *zswap_entry_find_get(struct rb_root *root, pgoff_t offset) { struct zswap_entry *entry; entry = zswap_rb_search(root, offset); if (entry) zswap_entry_get(entry); return entry; } /********************************* * per-cpu code **********************************/ static DEFINE_PER_CPU(u8 *, zswap_dstmem); /* * If users dynamically change the zpool type and compressor at runtime, i.e. * zswap is running, zswap can have more than one zpool on one cpu, but they * are sharing dtsmem. So we need this mutex to be per-cpu. */ static DEFINE_PER_CPU(struct mutex *, zswap_mutex); static int zswap_dstmem_prepare(unsigned int cpu) { struct mutex *mutex; u8 *dst; dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu)); if (!dst) return -ENOMEM; mutex = kmalloc_node(sizeof(*mutex), GFP_KERNEL, cpu_to_node(cpu)); if (!mutex) { kfree(dst); return -ENOMEM; } mutex_init(mutex); per_cpu(zswap_dstmem, cpu) = dst; per_cpu(zswap_mutex, cpu) = mutex; return 0; } static int zswap_dstmem_dead(unsigned int cpu) { struct mutex *mutex; u8 *dst; mutex = per_cpu(zswap_mutex, cpu); kfree(mutex); per_cpu(zswap_mutex, cpu) = NULL; dst = per_cpu(zswap_dstmem, cpu); kfree(dst); per_cpu(zswap_dstmem, cpu) = NULL; return 0; } static int zswap_cpu_comp_prepare(unsigned int cpu, struct hlist_node *node) { struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node); struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu); struct crypto_acomp *acomp; struct acomp_req *req; acomp = crypto_alloc_acomp_node(pool->tfm_name, 0, 0, cpu_to_node(cpu)); if (IS_ERR(acomp)) { pr_err("could not alloc crypto acomp %s : %ld\n", pool->tfm_name, PTR_ERR(acomp)); return PTR_ERR(acomp); } acomp_ctx->acomp = acomp; req = acomp_request_alloc(acomp_ctx->acomp); if (!req) { pr_err("could not alloc crypto acomp_request %s\n", pool->tfm_name); crypto_free_acomp(acomp_ctx->acomp); return -ENOMEM; } acomp_ctx->req = req; crypto_init_wait(&acomp_ctx->wait); /* * if the backend of acomp is async zip, crypto_req_done() will wakeup * crypto_wait_req(); if the backend of acomp is scomp, the callback * won't be called, crypto_wait_req() will return without blocking. */ acomp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, crypto_req_done, &acomp_ctx->wait); acomp_ctx->mutex = per_cpu(zswap_mutex, cpu); acomp_ctx->dstmem = per_cpu(zswap_dstmem, cpu); return 0; } static int zswap_cpu_comp_dead(unsigned int cpu, struct hlist_node *node) { struct zswap_pool *pool = hlist_entry(node, struct zswap_pool, node); struct crypto_acomp_ctx *acomp_ctx = per_cpu_ptr(pool->acomp_ctx, cpu); if (!IS_ERR_OR_NULL(acomp_ctx)) { if (!IS_ERR_OR_NULL(acomp_ctx->req)) acomp_request_free(acomp_ctx->req); if (!IS_ERR_OR_NULL(acomp_ctx->acomp)) crypto_free_acomp(acomp_ctx->acomp); } return 0; } /********************************* * pool functions **********************************/ static struct zswap_pool *__zswap_pool_current(void) { struct zswap_pool *pool; pool = list_first_or_null_rcu(&zswap_pools, typeof(*pool), list); WARN_ONCE(!pool && zswap_has_pool, "%s: no page storage pool!\n", __func__); return pool; } static struct zswap_pool *zswap_pool_current(void) { assert_spin_locked(&zswap_pools_lock); return __zswap_pool_current(); } static struct zswap_pool *zswap_pool_current_get(void) { struct zswap_pool *pool; rcu_read_lock(); pool = __zswap_pool_current(); if (!zswap_pool_get(pool)) pool = NULL; rcu_read_unlock(); return pool; } static struct zswap_pool *zswap_pool_last_get(void) { struct zswap_pool *pool, *last = NULL; rcu_read_lock(); list_for_each_entry_rcu(pool, &zswap_pools, list) last = pool; WARN_ONCE(!last && zswap_has_pool, "%s: no page storage pool!\n", __func__); if (!zswap_pool_get(last)) last = NULL; rcu_read_unlock(); return last; } /* type and compressor must be null-terminated */ static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor) { struct zswap_pool *pool; assert_spin_locked(&zswap_pools_lock); list_for_each_entry_rcu(pool, &zswap_pools, list) { if (strcmp(pool->tfm_name, compressor)) continue; if (strcmp(zpool_get_type(pool->zpool), type)) continue; /* if we can't get it, it's about to be destroyed */ if (!zswap_pool_get(pool)) continue; return pool; } return NULL; } static void shrink_worker(struct work_struct *w) { struct zswap_pool *pool = container_of(w, typeof(*pool), shrink_work); if (zpool_shrink(pool->zpool, 1, NULL)) zswap_reject_reclaim_fail++; zswap_pool_put(pool); } static struct zswap_pool *zswap_pool_create(char *type, char *compressor) { struct zswap_pool *pool; char name[38]; /* 'zswap' + 32 char (max) num + \0 */ gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM; int ret; if (!zswap_has_pool) { /* if either are unset, pool initialization failed, and we * need both params to be set correctly before trying to * create a pool. */ if (!strcmp(type, ZSWAP_PARAM_UNSET)) return NULL; if (!strcmp(compressor, ZSWAP_PARAM_UNSET)) return NULL; } pool = kzalloc(sizeof(*pool), GFP_KERNEL); if (!pool) return NULL; /* unique name for each pool specifically required by zsmalloc */ snprintf(name, 38, "zswap%x", atomic_inc_return(&zswap_pools_count)); pool->zpool = zpool_create_pool(type, name, gfp, &zswap_zpool_ops); if (!pool->zpool) { pr_err("%s zpool not available\n", type); goto error; } pr_debug("using %s zpool\n", zpool_get_type(pool->zpool)); strscpy(pool->tfm_name, compressor, sizeof(pool->tfm_name)); pool->acomp_ctx = alloc_percpu(*pool->acomp_ctx); if (!pool->acomp_ctx) { pr_err("percpu alloc failed\n"); goto error; } ret = cpuhp_state_add_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node); if (ret) goto error; pr_debug("using %s compressor\n", pool->tfm_name); /* being the current pool takes 1 ref; this func expects the * caller to always add the new pool as the current pool */ kref_init(&pool->kref); INIT_LIST_HEAD(&pool->list); INIT_WORK(&pool->shrink_work, shrink_worker); zswap_pool_debug("created", pool); return pool; error: if (pool->acomp_ctx) free_percpu(pool->acomp_ctx); if (pool->zpool) zpool_destroy_pool(pool->zpool); kfree(pool); return NULL; } static __init struct zswap_pool *__zswap_pool_create_fallback(void) { bool has_comp, has_zpool; has_comp = crypto_has_acomp(zswap_compressor, 0, 0); if (!has_comp && strcmp(zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) { pr_err("compressor %s not available, using default %s\n", zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT); param_free_charp(&zswap_compressor); zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT; has_comp = crypto_has_acomp(zswap_compressor, 0, 0); } if (!has_comp) { pr_err("default compressor %s not available\n", zswap_compressor); param_free_charp(&zswap_compressor); zswap_compressor = ZSWAP_PARAM_UNSET; } has_zpool = zpool_has_pool(zswap_zpool_type); if (!has_zpool && strcmp(zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT)) { pr_err("zpool %s not available, using default %s\n", zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT); param_free_charp(&zswap_zpool_type); zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT; has_zpool = zpool_has_pool(zswap_zpool_type); } if (!has_zpool) { pr_err("default zpool %s not available\n", zswap_zpool_type); param_free_charp(&zswap_zpool_type); zswap_zpool_type = ZSWAP_PARAM_UNSET; } if (!has_comp || !has_zpool) return NULL; return zswap_pool_create(zswap_zpool_type, zswap_compressor); } static void zswap_pool_destroy(struct zswap_pool *pool) { zswap_pool_debug("destroying", pool); cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node); free_percpu(pool->acomp_ctx); zpool_destroy_pool(pool->zpool); kfree(pool); } static int __must_check zswap_pool_get(struct zswap_pool *pool) { if (!pool) return 0; return kref_get_unless_zero(&pool->kref); } static void __zswap_pool_release(struct work_struct *work) { struct zswap_pool *pool = container_of(work, typeof(*pool), release_work); synchronize_rcu(); /* nobody should have been able to get a kref... */ WARN_ON(kref_get_unless_zero(&pool->kref)); /* pool is now off zswap_pools list and has no references. */ zswap_pool_destroy(pool); } static void __zswap_pool_empty(struct kref *kref) { struct zswap_pool *pool; pool = container_of(kref, typeof(*pool), kref); spin_lock(&zswap_pools_lock); WARN_ON(pool == zswap_pool_current()); list_del_rcu(&pool->list); INIT_WORK(&pool->release_work, __zswap_pool_release); schedule_work(&pool->release_work); spin_unlock(&zswap_pools_lock); } static void zswap_pool_put(struct zswap_pool *pool) { kref_put(&pool->kref, __zswap_pool_empty); } /********************************* * param callbacks **********************************/ /* val must be a null-terminated string */ static int __zswap_param_set(const char *val, const struct kernel_param *kp, char *type, char *compressor) { struct zswap_pool *pool, *put_pool = NULL; char *s = strstrip((char *)val); int ret; if (zswap_init_failed) { pr_err("can't set param, initialization failed\n"); return -ENODEV; } /* no change required */ if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool) return 0; /* if this is load-time (pre-init) param setting, * don't create a pool; that's done during init. */ if (!zswap_init_started) return param_set_charp(s, kp); if (!type) { if (!zpool_has_pool(s)) { pr_err("zpool %s not available\n", s); return -ENOENT; } type = s; } else if (!compressor) { if (!crypto_has_acomp(s, 0, 0)) { pr_err("compressor %s not available\n", s); return -ENOENT; } compressor = s; } else { WARN_ON(1); return -EINVAL; } spin_lock(&zswap_pools_lock); pool = zswap_pool_find_get(type, compressor); if (pool) { zswap_pool_debug("using existing", pool); WARN_ON(pool == zswap_pool_current()); list_del_rcu(&pool->list); } spin_unlock(&zswap_pools_lock); if (!pool) pool = zswap_pool_create(type, compressor); if (pool) ret = param_set_charp(s, kp); else ret = -EINVAL; spin_lock(&zswap_pools_lock); if (!ret) { put_pool = zswap_pool_current(); list_add_rcu(&pool->list, &zswap_pools); zswap_has_pool = true; } else if (pool) { /* add the possibly pre-existing pool to the end of the pools * list; if it's new (and empty) then it'll be removed and * destroyed by the put after we drop the lock */ list_add_tail_rcu(&pool->list, &zswap_pools); put_pool = pool; } spin_unlock(&zswap_pools_lock); if (!zswap_has_pool && !pool) { /* if initial pool creation failed, and this pool creation also * failed, maybe both compressor and zpool params were bad. * Allow changing this param, so pool creation will succeed * when the other param is changed. We already verified this * param is ok in the zpool_has_pool() or crypto_has_acomp() * checks above. */ ret = param_set_charp(s, kp); } /* drop the ref from either the old current pool, * or the new pool we failed to add */ if (put_pool) zswap_pool_put(put_pool); return ret; } static int zswap_compressor_param_set(const char *val, const struct kernel_param *kp) { return __zswap_param_set(val, kp, zswap_zpool_type, NULL); } static int zswap_zpool_param_set(const char *val, const struct kernel_param *kp) { return __zswap_param_set(val, kp, NULL, zswap_compressor); } static int zswap_enabled_param_set(const char *val, const struct kernel_param *kp) { if (zswap_init_failed) { pr_err("can't enable, initialization failed\n"); return -ENODEV; } if (!zswap_has_pool && zswap_init_started) { pr_err("can't enable, no pool configured\n"); return -ENODEV; } return param_set_bool(val, kp); } /********************************* * writeback code **********************************/ /* return enum for zswap_get_swap_cache_page */ enum zswap_get_swap_ret { ZSWAP_SWAPCACHE_NEW, ZSWAP_SWAPCACHE_EXIST, ZSWAP_SWAPCACHE_FAIL, }; /* * zswap_get_swap_cache_page * * This is an adaption of read_swap_cache_async() * * This function tries to find a page with the given swap entry * in the swapper_space address space (the swap cache). If the page * is found, it is returned in retpage. Otherwise, a page is allocated, * added to the swap cache, and returned in retpage. * * If success, the swap cache page is returned in retpage * Returns ZSWAP_SWAPCACHE_EXIST if page was already in the swap cache * Returns ZSWAP_SWAPCACHE_NEW if the new page needs to be populated, * the new page is added to swapcache and locked * Returns ZSWAP_SWAPCACHE_FAIL on error */ static int zswap_get_swap_cache_page(swp_entry_t entry, struct page **retpage) { bool page_was_allocated; *retpage = __read_swap_cache_async(entry, GFP_KERNEL, NULL, 0, &page_was_allocated); if (page_was_allocated) return ZSWAP_SWAPCACHE_NEW; if (!*retpage) return ZSWAP_SWAPCACHE_FAIL; return ZSWAP_SWAPCACHE_EXIST; } /* * Attempts to free an entry by adding a page to the swap cache, * decompressing the entry data into the page, and issuing a * bio write to write the page back to the swap device. * * This can be thought of as a "resumed writeback" of the page * to the swap device. We are basically resuming the same swap * writeback path that was intercepted with the frontswap_store() * in the first place. After the page has been decompressed into * the swap cache, the compressed version stored by zswap can be * freed. */ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle) { struct zswap_header *zhdr; swp_entry_t swpentry; struct zswap_tree *tree; pgoff_t offset; struct zswap_entry *entry; struct page *page; struct scatterlist input, output; struct crypto_acomp_ctx *acomp_ctx; u8 *src, *tmp = NULL; unsigned int dlen; int ret; struct writeback_control wbc = { .sync_mode = WB_SYNC_NONE, }; if (!zpool_can_sleep_mapped(pool)) { tmp = kmalloc(PAGE_SIZE, GFP_ATOMIC); if (!tmp) return -ENOMEM; } /* extract swpentry from data */ zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO); swpentry = zhdr->swpentry; /* here */ tree = zswap_trees[swp_type(swpentry)]; offset = swp_offset(swpentry); /* find and ref zswap entry */ spin_lock(&tree->lock); entry = zswap_entry_find_get(&tree->rbroot, offset); if (!entry) { /* entry was invalidated */ spin_unlock(&tree->lock); zpool_unmap_handle(pool, handle); kfree(tmp); return 0; } spin_unlock(&tree->lock); BUG_ON(offset != entry->offset); src = (u8 *)zhdr + sizeof(struct zswap_header); if (!zpool_can_sleep_mapped(pool)) { memcpy(tmp, src, entry->length); src = tmp; zpool_unmap_handle(pool, handle); } /* try to allocate swap cache page */ switch (zswap_get_swap_cache_page(swpentry, &page)) { case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */ ret = -ENOMEM; goto fail; case ZSWAP_SWAPCACHE_EXIST: /* page is already in the swap cache, ignore for now */ put_page(page); ret = -EEXIST; goto fail; case ZSWAP_SWAPCACHE_NEW: /* page is locked */ /* * Having a local reference to the zswap entry doesn't exclude * swapping from invalidating and recycling the swap slot. Once * the swapcache is secured against concurrent swapping to and * from the slot, recheck that the entry is still current before * writing. */ spin_lock(&tree->lock); if (zswap_rb_search(&tree->rbroot, entry->offset) != entry) { spin_unlock(&tree->lock); delete_from_swap_cache(page_folio(page)); ret = -ENOMEM; goto fail; } spin_unlock(&tree->lock); /* decompress */ acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx); dlen = PAGE_SIZE; mutex_lock(acomp_ctx->mutex); sg_init_one(&input, src, entry->length); sg_init_table(&output, 1); sg_set_page(&output, page, PAGE_SIZE, 0); acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen); ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait); dlen = acomp_ctx->req->dlen; mutex_unlock(acomp_ctx->mutex); BUG_ON(ret); BUG_ON(dlen != PAGE_SIZE); /* page is up to date */ SetPageUptodate(page); } /* move it to the tail of the inactive list after end_writeback */ SetPageReclaim(page); /* start writeback */ __swap_writepage(page, &wbc); put_page(page); zswap_written_back_pages++; spin_lock(&tree->lock); /* drop local reference */ zswap_entry_put(tree, entry); /* * There are two possible situations for entry here: * (1) refcount is 1(normal case), entry is valid and on the tree * (2) refcount is 0, entry is freed and not on the tree * because invalidate happened during writeback * search the tree and free the entry if find entry */ if (entry == zswap_rb_search(&tree->rbroot, offset)) zswap_entry_put(tree, entry); spin_unlock(&tree->lock); goto end; /* * if we get here due to ZSWAP_SWAPCACHE_EXIST * a load may be happening concurrently. * it is safe and okay to not free the entry. * if we free the entry in the following put * it is also okay to return !0 */ fail: spin_lock(&tree->lock); zswap_entry_put(tree, entry); spin_unlock(&tree->lock); end: if (zpool_can_sleep_mapped(pool)) zpool_unmap_handle(pool, handle); else kfree(tmp); return ret; } static int zswap_is_page_same_filled(void *ptr, unsigned long *value) { unsigned int pos; unsigned long *page; page = (unsigned long *)ptr; for (pos = 1; pos < PAGE_SIZE / sizeof(*page); pos++) { if (page[pos] != page[0]) return 0; } *value = page[0]; return 1; } static void zswap_fill_page(void *ptr, unsigned long value) { unsigned long *page; page = (unsigned long *)ptr; memset_l(page, value, PAGE_SIZE / sizeof(unsigned long)); } /********************************* * frontswap hooks **********************************/ /* attempts to compress and store an single page */ static int zswap_frontswap_store(unsigned type, pgoff_t offset, struct page *page) { struct zswap_tree *tree = zswap_trees[type]; struct zswap_entry *entry, *dupentry; struct scatterlist input, output; struct crypto_acomp_ctx *acomp_ctx; struct obj_cgroup *objcg = NULL; struct zswap_pool *pool; int ret; unsigned int hlen, dlen = PAGE_SIZE; unsigned long handle, value; char *buf; u8 *src, *dst; struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) }; gfp_t gfp; /* THP isn't supported */ if (PageTransHuge(page)) { ret = -EINVAL; goto reject; } if (!zswap_enabled || !tree) { ret = -ENODEV; goto reject; } objcg = get_obj_cgroup_from_page(page); if (objcg && !obj_cgroup_may_zswap(objcg)) goto shrink; /* reclaim space if needed */ if (zswap_is_full()) { zswap_pool_limit_hit++; zswap_pool_reached_full = true; goto shrink; } if (zswap_pool_reached_full) { if (!zswap_can_accept()) { ret = -ENOMEM; goto reject; } else zswap_pool_reached_full = false; } /* allocate entry */ entry = zswap_entry_cache_alloc(GFP_KERNEL); if (!entry) { zswap_reject_kmemcache_fail++; ret = -ENOMEM; goto reject; } if (zswap_same_filled_pages_enabled) { src = kmap_atomic(page); if (zswap_is_page_same_filled(src, &value)) { kunmap_atomic(src); entry->offset = offset; entry->length = 0; entry->value = value; atomic_inc(&zswap_same_filled_pages); goto insert_entry; } kunmap_atomic(src); } if (!zswap_non_same_filled_pages_enabled) { ret = -EINVAL; goto freepage; } /* if entry is successfully added, it keeps the reference */ entry->pool = zswap_pool_current_get(); if (!entry->pool) { ret = -EINVAL; goto freepage; } /* compress */ acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx); mutex_lock(acomp_ctx->mutex); dst = acomp_ctx->dstmem; sg_init_table(&input, 1); sg_set_page(&input, page, PAGE_SIZE, 0); /* zswap_dstmem is of size (PAGE_SIZE * 2). Reflect same in sg_list */ sg_init_one(&output, dst, PAGE_SIZE * 2); acomp_request_set_params(acomp_ctx->req, &input, &output, PAGE_SIZE, dlen); /* * it maybe looks a little bit silly that we send an asynchronous request, * then wait for its completion synchronously. This makes the process look * synchronous in fact. * Theoretically, acomp supports users send multiple acomp requests in one * acomp instance, then get those requests done simultaneously. but in this * case, frontswap actually does store and load page by page, there is no * existing method to send the second page before the first page is done * in one thread doing frontswap. * but in different threads running on different cpu, we have different * acomp instance, so multiple threads can do (de)compression in parallel. */ ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait); dlen = acomp_ctx->req->dlen; if (ret) { ret = -EINVAL; goto put_dstmem; } /* store */ hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0; gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM; if (zpool_malloc_support_movable(entry->pool->zpool)) gfp |= __GFP_HIGHMEM | __GFP_MOVABLE; ret = zpool_malloc(entry->pool->zpool, hlen + dlen, gfp, &handle); if (ret == -ENOSPC) { zswap_reject_compress_poor++; goto put_dstmem; } if (ret) { zswap_reject_alloc_fail++; goto put_dstmem; } buf = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_WO); memcpy(buf, &zhdr, hlen); memcpy(buf + hlen, dst, dlen); zpool_unmap_handle(entry->pool->zpool, handle); mutex_unlock(acomp_ctx->mutex); /* populate entry */ entry->offset = offset; entry->handle = handle; entry->length = dlen; insert_entry: entry->objcg = objcg; if (objcg) { obj_cgroup_charge_zswap(objcg, entry->length); /* Account before objcg ref is moved to tree */ count_objcg_event(objcg, ZSWPOUT); } /* map */ spin_lock(&tree->lock); do { ret = zswap_rb_insert(&tree->rbroot, entry, &dupentry); if (ret == -EEXIST) { zswap_duplicate_entry++; /* remove from rbtree */ zswap_rb_erase(&tree->rbroot, dupentry); zswap_entry_put(tree, dupentry); } } while (ret == -EEXIST); spin_unlock(&tree->lock); /* update stats */ atomic_inc(&zswap_stored_pages); zswap_update_total_size(); count_vm_event(ZSWPOUT); return 0; put_dstmem: mutex_unlock(acomp_ctx->mutex); zswap_pool_put(entry->pool); freepage: zswap_entry_cache_free(entry); reject: if (objcg) obj_cgroup_put(objcg); return ret; shrink: pool = zswap_pool_last_get(); if (pool) queue_work(shrink_wq, &pool->shrink_work); ret = -ENOMEM; goto reject; } /* * returns 0 if the page was successfully decompressed * return -1 on entry not found or error */ static int zswap_frontswap_load(unsigned type, pgoff_t offset, struct page *page) { struct zswap_tree *tree = zswap_trees[type]; struct zswap_entry *entry; struct scatterlist input, output; struct crypto_acomp_ctx *acomp_ctx; u8 *src, *dst, *tmp; unsigned int dlen; int ret; /* find */ spin_lock(&tree->lock); entry = zswap_entry_find_get(&tree->rbroot, offset); if (!entry) { /* entry was written back */ spin_unlock(&tree->lock); return -1; } spin_unlock(&tree->lock); if (!entry->length) { dst = kmap_atomic(page); zswap_fill_page(dst, entry->value); kunmap_atomic(dst); ret = 0; goto stats; } if (!zpool_can_sleep_mapped(entry->pool->zpool)) { tmp = kmalloc(entry->length, GFP_ATOMIC); if (!tmp) { ret = -ENOMEM; goto freeentry; } } /* decompress */ dlen = PAGE_SIZE; src = zpool_map_handle(entry->pool->zpool, entry->handle, ZPOOL_MM_RO); if (zpool_evictable(entry->pool->zpool)) src += sizeof(struct zswap_header); if (!zpool_can_sleep_mapped(entry->pool->zpool)) { memcpy(tmp, src, entry->length); src = tmp; zpool_unmap_handle(entry->pool->zpool, entry->handle); } acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx); mutex_lock(acomp_ctx->mutex); sg_init_one(&input, src, entry->length); sg_init_table(&output, 1); sg_set_page(&output, page, PAGE_SIZE, 0); acomp_request_set_params(acomp_ctx->req, &input, &output, entry->length, dlen); ret = crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait); mutex_unlock(acomp_ctx->mutex); if (zpool_can_sleep_mapped(entry->pool->zpool)) zpool_unmap_handle(entry->pool->zpool, entry->handle); else kfree(tmp); BUG_ON(ret); stats: count_vm_event(ZSWPIN); if (entry->objcg) count_objcg_event(entry->objcg, ZSWPIN); freeentry: spin_lock(&tree->lock); zswap_entry_put(tree, entry); spin_unlock(&tree->lock); return ret; } /* frees an entry in zswap */ static void zswap_frontswap_invalidate_page(unsigned type, pgoff_t offset) { struct zswap_tree *tree = zswap_trees[type]; struct zswap_entry *entry; /* find */ spin_lock(&tree->lock); entry = zswap_rb_search(&tree->rbroot, offset); if (!entry) { /* entry was written back */ spin_unlock(&tree->lock); return; } /* remove from rbtree */ zswap_rb_erase(&tree->rbroot, entry); /* drop the initial reference from entry creation */ zswap_entry_put(tree, entry); spin_unlock(&tree->lock); } /* frees all zswap entries for the given swap type */ static void zswap_frontswap_invalidate_area(unsigned type) { struct zswap_tree *tree = zswap_trees[type]; struct zswap_entry *entry, *n; if (!tree) return; /* walk the tree and free everything */ spin_lock(&tree->lock); rbtree_postorder_for_each_entry_safe(entry, n, &tree->rbroot, rbnode) zswap_free_entry(entry); tree->rbroot = RB_ROOT; spin_unlock(&tree->lock); kfree(tree); zswap_trees[type] = NULL; } static void zswap_frontswap_init(unsigned type) { struct zswap_tree *tree; tree = kzalloc(sizeof(*tree), GFP_KERNEL); if (!tree) { pr_err("alloc failed, zswap disabled for swap type %d\n", type); return; } tree->rbroot = RB_ROOT; spin_lock_init(&tree->lock); zswap_trees[type] = tree; } static const struct frontswap_ops zswap_frontswap_ops = { .store = zswap_frontswap_store, .load = zswap_frontswap_load, .invalidate_page = zswap_frontswap_invalidate_page, .invalidate_area = zswap_frontswap_invalidate_area, .init = zswap_frontswap_init }; /********************************* * debugfs functions **********************************/ #ifdef CONFIG_DEBUG_FS #include static struct dentry *zswap_debugfs_root; static int __init zswap_debugfs_init(void) { if (!debugfs_initialized()) return -ENODEV; zswap_debugfs_root = debugfs_create_dir("zswap", NULL); debugfs_create_u64("pool_limit_hit", 0444, zswap_debugfs_root, &zswap_pool_limit_hit); debugfs_create_u64("reject_reclaim_fail", 0444, zswap_debugfs_root, &zswap_reject_reclaim_fail); debugfs_create_u64("reject_alloc_fail", 0444, zswap_debugfs_root, &zswap_reject_alloc_fail); debugfs_create_u64("reject_kmemcache_fail", 0444, zswap_debugfs_root, &zswap_reject_kmemcache_fail); debugfs_create_u64("reject_compress_poor", 0444, zswap_debugfs_root, &zswap_reject_compress_poor); debugfs_create_u64("written_back_pages", 0444, zswap_debugfs_root, &zswap_written_back_pages); debugfs_create_u64("duplicate_entry", 0444, zswap_debugfs_root, &zswap_duplicate_entry); debugfs_create_u64("pool_total_size", 0444, zswap_debugfs_root, &zswap_pool_total_size); debugfs_create_atomic_t("stored_pages", 0444, zswap_debugfs_root, &zswap_stored_pages); debugfs_create_atomic_t("same_filled_pages", 0444, zswap_debugfs_root, &zswap_same_filled_pages); return 0; } #else static int __init zswap_debugfs_init(void) { return 0; } #endif /********************************* * module init and exit **********************************/ static int __init init_zswap(void) { struct zswap_pool *pool; int ret; zswap_init_started = true; if (zswap_entry_cache_create()) { pr_err("entry cache creation failed\n"); goto cache_fail; } ret = cpuhp_setup_state(CPUHP_MM_ZSWP_MEM_PREPARE, "mm/zswap:prepare", zswap_dstmem_prepare, zswap_dstmem_dead); if (ret) { pr_err("dstmem alloc failed\n"); goto dstmem_fail; } ret = cpuhp_setup_state_multi(CPUHP_MM_ZSWP_POOL_PREPARE, "mm/zswap_pool:prepare", zswap_cpu_comp_prepare, zswap_cpu_comp_dead); if (ret) goto hp_fail; pool = __zswap_pool_create_fallback(); if (pool) { pr_info("loaded using pool %s/%s\n", pool->tfm_name, zpool_get_type(pool->zpool)); list_add(&pool->list, &zswap_pools); zswap_has_pool = true; } else { pr_err("pool creation failed\n"); zswap_enabled = false; } shrink_wq = create_workqueue("zswap-shrink"); if (!shrink_wq) goto fallback_fail; ret = frontswap_register_ops(&zswap_frontswap_ops); if (ret) goto destroy_wq; if (zswap_debugfs_init()) pr_warn("debugfs initialization failed\n"); return 0; destroy_wq: destroy_workqueue(shrink_wq); fallback_fail: if (pool) zswap_pool_destroy(pool); hp_fail: cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE); dstmem_fail: zswap_entry_cache_destroy(); cache_fail: /* if built-in, we aren't unloaded on failure; don't allow use */ zswap_init_failed = true; zswap_enabled = false; return -ENOMEM; } /* must be late so crypto has time to come up */ late_initcall(init_zswap); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Seth Jennings "); MODULE_DESCRIPTION("Compressed cache for swap pages");