v4.19.13 snapshot.
diff --git a/mm/zswap.c b/mm/zswap.c
new file mode 100644
index 0000000..cd91fd9
--- /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");