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Diffstat (limited to '')
| -rw-r--r-- | mm/zswap.c | 1365 |
1 files changed, 1365 insertions, 0 deletions
diff --git a/mm/zswap.c b/mm/zswap.c new file mode 100644 index 000000000..cd91fd9d9 --- /dev/null +++ b/mm/zswap.c @@ -0,0 +1,1365 @@ +/* + * 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 <sjenning@linux.vnet.ibm.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. +*/ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/cpu.h> +#include <linux/highmem.h> +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/types.h> +#include <linux/atomic.h> +#include <linux/frontswap.h> +#include <linux/rbtree.h> +#include <linux/swap.h> +#include <linux/crypto.h> +#include <linux/mempool.h> +#include <linux/zpool.h> + +#include <linux/mm_types.h> +#include <linux/page-flags.h> +#include <linux/swapops.h> +#include <linux/writeback.h> +#include <linux/pagemap.h> + +/********************************* +* statistics +**********************************/ +/* Total bytes used by the compressed storage */ +static u64 zswap_pool_total_size; +/* The number of compressed pages currently stored in zswap */ +static 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; + +/********************************* +* tunables +**********************************/ + +#define ZSWAP_PARAM_UNSET "" + +/* Enable/disable zswap (disabled by default) */ +static bool zswap_enabled; +static int zswap_enabled_param_set(const char *, + const struct kernel_param *); +static 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 */ +#define ZSWAP_COMPRESSOR_DEFAULT "lzo" +static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT; +static int zswap_compressor_param_set(const char *, + const struct kernel_param *); +static 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 */ +#define ZSWAP_ZPOOL_DEFAULT "zbud" +static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT; +static int zswap_zpool_param_set(const char *, const struct kernel_param *); +static 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); + +/* Enable/disable handling same-value filled pages (enabled by default) */ +static bool zswap_same_filled_pages_enabled = true; +module_param_named(same_filled_pages_enabled, zswap_same_filled_pages_enabled, + bool, 0644); + +/********************************* +* data structures +**********************************/ + +struct zswap_pool { + struct zpool *zpool; + struct crypto_comp * __percpu *tfm; + struct kref kref; + struct list_head list; + struct work_struct 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 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 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->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); + +static int zswap_dstmem_prepare(unsigned int cpu) +{ + u8 *dst; + + dst = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu)); + if (!dst) + return -ENOMEM; + + per_cpu(zswap_dstmem, cpu) = dst; + return 0; +} + +static int zswap_dstmem_dead(unsigned int cpu) +{ + u8 *dst; + + 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_comp *tfm; + + if (WARN_ON(*per_cpu_ptr(pool->tfm, cpu))) + return 0; + + tfm = crypto_alloc_comp(pool->tfm_name, 0, 0); + if (IS_ERR_OR_NULL(tfm)) { + pr_err("could not alloc crypto comp %s : %ld\n", + pool->tfm_name, PTR_ERR(tfm)); + return -ENOMEM; + } + *per_cpu_ptr(pool->tfm, cpu) = tfm; + 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_comp *tfm; + + tfm = *per_cpu_ptr(pool->tfm, cpu); + if (!IS_ERR_OR_NULL(tfm)) + crypto_free_comp(tfm); + *per_cpu_ptr(pool->tfm, cpu) = NULL; + 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 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)); + + strlcpy(pool->tfm_name, compressor, sizeof(pool->tfm_name)); + pool->tfm = alloc_percpu(struct crypto_comp *); + if (!pool->tfm) { + 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); + + zswap_pool_debug("created", pool); + + return pool; + +error: + free_percpu(pool->tfm); + 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_comp(zswap_compressor, 0, 0); + if (!has_comp && strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) { + pr_err("compressor %s not available, using default %s\n", + zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT); + param_free_charp(&zswap_compressor); + zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT; + has_comp = crypto_has_comp(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, ZSWAP_ZPOOL_DEFAULT)) { + pr_err("zpool %s not available, using default %s\n", + zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT); + param_free_charp(&zswap_zpool_type); + zswap_zpool_type = 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->tfm); + 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), 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->work, __zswap_pool_release); + schedule_work(&pool->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_comp(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_comp() + * 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 crypto_comp *tfm; + u8 *src, *dst; + unsigned int dlen; + int ret; + struct writeback_control wbc = { + .sync_mode = WB_SYNC_NONE, + }; + + /* extract swpentry from data */ + zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO); + swpentry = zhdr->swpentry; /* here */ + zpool_unmap_handle(pool, handle); + 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); + return 0; + } + spin_unlock(&tree->lock); + BUG_ON(offset != entry->offset); + + /* 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 */ + /* decompress */ + dlen = PAGE_SIZE; + src = (u8 *)zpool_map_handle(entry->pool->zpool, entry->handle, + ZPOOL_MM_RO) + sizeof(struct zswap_header); + dst = kmap_atomic(page); + tfm = *get_cpu_ptr(entry->pool->tfm); + ret = crypto_comp_decompress(tfm, src, entry->length, + dst, &dlen); + put_cpu_ptr(entry->pool->tfm); + kunmap_atomic(dst); + zpool_unmap_handle(entry->pool->zpool, entry->handle); + 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, end_swap_bio_write); + 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 happening concurrently + * it is safe and okay to not free the entry + * if we free the entry in the following put + * it it either okay to return !0 + */ +fail: + spin_lock(&tree->lock); + zswap_entry_put(tree, entry); + spin_unlock(&tree->lock); + +end: + return ret; +} + +static int zswap_shrink(void) +{ + struct zswap_pool *pool; + int ret; + + pool = zswap_pool_last_get(); + if (!pool) + return -ENOENT; + + ret = zpool_shrink(pool->zpool, 1, NULL); + + zswap_pool_put(pool); + + 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 crypto_comp *tfm; + 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) }; + + /* THP isn't supported */ + if (PageTransHuge(page)) { + ret = -EINVAL; + goto reject; + } + + if (!zswap_enabled || !tree) { + ret = -ENODEV; + goto reject; + } + + /* reclaim space if needed */ + if (zswap_is_full()) { + zswap_pool_limit_hit++; + if (zswap_shrink()) { + zswap_reject_reclaim_fail++; + ret = -ENOMEM; + goto reject; + } + + /* A second zswap_is_full() check after + * zswap_shrink() to make sure it's now + * under the max_pool_percent + */ + if (zswap_is_full()) { + ret = -ENOMEM; + goto reject; + } + } + + /* 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 entry is successfully added, it keeps the reference */ + entry->pool = zswap_pool_current_get(); + if (!entry->pool) { + ret = -EINVAL; + goto freepage; + } + + /* compress */ + dst = get_cpu_var(zswap_dstmem); + tfm = *get_cpu_ptr(entry->pool->tfm); + src = kmap_atomic(page); + ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen); + kunmap_atomic(src); + put_cpu_ptr(entry->pool->tfm); + if (ret) { + ret = -EINVAL; + goto put_dstmem; + } + + /* store */ + hlen = zpool_evictable(entry->pool->zpool) ? sizeof(zhdr) : 0; + ret = zpool_malloc(entry->pool->zpool, hlen + dlen, + __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM, + &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_RW); + memcpy(buf, &zhdr, hlen); + memcpy(buf + hlen, dst, dlen); + zpool_unmap_handle(entry->pool->zpool, handle); + put_cpu_var(zswap_dstmem); + + /* populate entry */ + entry->offset = offset; + entry->handle = handle; + entry->length = dlen; + +insert_entry: + /* 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(); + + return 0; + +put_dstmem: + put_cpu_var(zswap_dstmem); + zswap_pool_put(entry->pool); +freepage: + zswap_entry_cache_free(entry); +reject: + return ret; +} + +/* + * 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 crypto_comp *tfm; + u8 *src, *dst; + 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); + 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); + dst = kmap_atomic(page); + tfm = *get_cpu_ptr(entry->pool->tfm); + ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen); + put_cpu_ptr(entry->pool->tfm); + kunmap_atomic(dst); + zpool_unmap_handle(entry->pool->zpool, entry->handle); + BUG_ON(ret); + +freeentry: + spin_lock(&tree->lock); + zswap_entry_put(tree, entry); + spin_unlock(&tree->lock); + + return 0; +} + +/* 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 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 <linux/debugfs.h> + +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); + if (!zswap_debugfs_root) + return -ENOMEM; + + 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; +} + +static void __exit zswap_debugfs_exit(void) +{ + debugfs_remove_recursive(zswap_debugfs_root); +} +#else +static int __init zswap_debugfs_init(void) +{ + return 0; +} + +static void __exit zswap_debugfs_exit(void) { } +#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; + } + + frontswap_register_ops(&zswap_frontswap_ops); + if (zswap_debugfs_init()) + pr_warn("debugfs initialization failed\n"); + return 0; + +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 <sjennings@variantweb.net>"); +MODULE_DESCRIPTION("Compressed cache for swap pages"); |