// SPDX-License-Identifier: GPL-2.0-or-later
/*
* zswap.c - zswap driver file
*
* zswap is a cache 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>
*/
#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/rbtree.h>
#include <linux/swap.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include <linux/mempolicy.h>
#include <linux/mempool.h>
#include <linux/zpool.h>
#include <crypto/acompress.h>
#include <linux/zswap.h>
#include <linux/mm_types.h>
#include <linux/page-flags.h>
#include <linux/swapops.h>
#include <linux/writeback.h>
#include <linux/pagemap.h>
#include <linux/workqueue.h>
#include <linux/list_lru.h>
#include "swap.h"
#include "internal.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;
/* Store failed due to compression algorithm failure */
static u64 zswap_reject_compress_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;
/* 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 ""
static int zswap_setup(void);
/* 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);
/* Number of zpools in zswap_pool (empirically determined for scalability) */
#define ZSWAP_NR_ZPOOLS 32
/* Enable/disable memory pressure-based shrinker. */
static bool zswap_shrinker_enabled = IS_ENABLED(
CONFIG_ZSWAP_SHRINKER_DEFAULT_ON);
module_param_named(shrinker_enabled, zswap_shrinker_enabled, bool, 0644);
bool is_zswap_enabled(void)
{
return zswap_enabled;
}
/*********************************
* data structures
**********************************/
struct crypto_acomp_ctx {
struct crypto_acomp *acomp;
struct acomp_req *req;
struct crypto_wait wait;
u8 *buffer;
struct mutex mutex;
bool is_sleepable;
};
/*
* The lock ordering is zswap_tree.lock -> zswap_pool.lru_lock.
* The only case where lru_lock is not acquired while holding tree.lock is
* when a zswap_entry is taken off the lru for writeback, in that case it
* needs to be verified that it's still valid in the tree.
*/
struct zswap_pool {
struct zpool *zpools[ZSWAP_NR_ZPOOLS];
struct crypto_acomp_ctx __percpu *acomp_ctx;
struct percpu_ref ref;
struct list_head list;
struct work_struct release_work;
struct hlist_node node;
char tfm_name[CRYPTO_MAX_ALG_NAME];
};
/* Global LRU lists shared by all zswap pools. */
static struct list_lru zswap_list_lru;
/* counter of pages stored in all zswap pools. */
static atomic_t zswap_nr_stored = ATOMIC_INIT(0);
/* The lock protects zswap_next_shrink updates. */
static DEFINE_SPINLOCK(zswap_shrink_lock);
static struct mem_cgroup *zswap_next_shrink;
static struct work_struct zswap_shrink_work;
static struct shrinker *zswap_shrinker;
/*
* 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
* swpentry - associated swap entry, the offset indexes into the red-black tree
* length - the length in bytes of the compressed page data. Needed during
* decompression. For a same value filled page length is 0, and both
* pool and lru are invalid and must be ignored.
* 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
* objcg - the obj_cgroup that the compressed memory is charged to
* lru - handle to the pool's lru used to evict pages.
*/
struct zswap_entry {
struct rb_node rbnode;
swp_entry_t swpentry;
unsigned int length;
struct zswap_pool *pool;
union {
unsigned long handle;
unsigned long value;
};
struct obj_cgroup *objcg;
struct list_head lru;
};
struct zswap_tree {
struct rb_root rbroot;
spinlock_t lock;
};
static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
static unsigned int nr_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);
enum zswap_init_type {
ZSWAP_UNINIT,
ZSWAP_INIT_SUCCEED,
ZSWAP_INIT_FAILED
};
static enum zswap_init_type zswap_init_state;
/* used to ensure the integrity of initialization */
static DEFINE_MUTEX(zswap_init_lock);
/* init completed, but couldn't create the initial pool */
static bool zswap_has_pool;
/*********************************
* helpers and fwd declarations
**********************************/
static inline struct zswap_tree *swap_zswap_tree(swp_entry_t swp)
{
return &zswap_trees[swp_type(swp)][swp_offset(swp)
>> SWAP_ADDRESS_SPACE_SHIFT];
}
#define zswap_pool_debug(msg, p) \
pr_debug("%s pool %s/%s\n", msg, (p)->tfm_name, \
zpool_get_type((p)->zpools[0]))
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 u64 get_zswap_pool_size(struct zswap_pool *pool)
{
u64 pool_size = 0;
int i;
for (i = 0; i < ZSWAP_NR_ZPOOLS; i++)
pool_size += zpool_get_total_size(pool->zpools[i]);
return pool_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 += get_zswap_pool_size(pool);
rcu_read_unlock();
zswap_pool_total_size = total;
}
/*********************************
* pool functions
**********************************/
static void __zswap_pool_empty(struct percpu_ref *ref);
static struct zswap_pool *zswap_pool_create(char *type, char *compressor)
{
int i;
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;
for (i = 0; i < ZSWAP_NR_ZPOOLS; i++) {
/* unique name for each pool specifically required by zsmalloc */
snprintf(name, 38, "zswap%x",
atomic_inc_return(&zswap_pools_count));
pool->zpools[i] = zpool_create_pool(type, name, gfp);
if (!pool->zpools[i]) {
pr_err("%s zpool not available\n", type);
goto error;
}
}
pr_debug("using %s zpool\n", zpool_get_type(pool->zpools[0]));
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;
/* being the current pool takes 1 ref; this func expects the
* caller to always add the new pool as the current pool
*/
ret = percpu_ref_init(&pool->ref, __zswap_pool_empty,
PERCPU_REF_ALLOW_REINIT, GFP_KERNEL);
if (ret)
goto ref_fail;
INIT_LIST_HEAD(&pool->list);
zswap_pool_debug("created", pool);
return pool;
ref_fail:
cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
error:
if (pool->acomp_ctx)
free_percpu(pool->acomp_ctx);
while (i--)
zpool_destroy_pool(pool->zpools[i]);
kfree(pool);
return NULL;
}
static 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)
{
int i;
zswap_pool_debug("destroying", pool);
cpuhp_state_remove_instance(CPUHP_MM_ZSWP_POOL_PREPARE, &pool->node);
free_percpu(pool->acomp_ctx);
for (i = 0; i < ZSWAP_NR_ZPOOLS; i++)
zpool_destroy_pool(pool->zpools[i]);
kfree(pool);
}
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 ref... */
WARN_ON(!percpu_ref_is_zero(&pool->ref));
percpu_ref_exit(&pool->ref);
/* pool is now off zswap_pools list and has no references. */
zswap_pool_destroy(pool);
}
static struct zswap_pool *zswap_pool_current(void);
static void __zswap_pool_empty(struct percpu_ref *ref)
{
struct zswap_pool *pool;
pool = container_of(ref, typeof(*pool), ref);
spin_lock_bh(&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_bh(&zswap_pools_lock);
}
static int __must_check zswap_pool_get(struct zswap_pool *pool)
{
if (!pool)
return 0;
return percpu_ref_tryget(&pool->ref);
}
static void zswap_pool_put(struct zswap_pool *pool)
{
percpu_ref_put(&pool->ref);
}
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;
}
/* 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;
/* all zpools share the same type */
if (strcmp(zpool_get_type(pool->zpools[0]), type))
continue;
/* if we can't get it, it's about to be destroyed */
if (!zswap_pool_get(pool))
continue;
return pool;
}
return NULL;
}
/*********************************
* param callbacks
**********************************/
static bool zswap_pool_changed(const char *s, const struct kernel_param *kp)
{
/* no change required */
if (!strcmp(s, *(char **)kp->arg) && zswap_has_pool)
return false;
return true;
}
/* 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 = 0;
bool new_pool = false;
mutex_lock(&zswap_init_lock);
switch (zswap_init_state) {
case ZSWAP_UNINIT:
/* if this is load-time (pre-init) param setting,
* don't create a pool; that's done during init.
*/
ret = param_set_charp(s, kp);
break;
case ZSWAP_INIT_SUCCEED:
new_pool = zswap_pool_changed(s, kp);
break;
case ZSWAP_INIT_FAILED:
pr_err("can't set param, initialization failed\n");
ret = -ENODEV;
}
mutex_unlock(&zswap_init_lock);
/* no need to create a new pool, return directly */
if (!new_pool)
return ret;
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_bh(&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_bh(&zswap_pools_lock);
if (!pool)
pool = zswap_pool_create(type, compressor);
else {
/*
* Restore the initial ref dropped by percpu_ref_kill()
* when the pool was decommissioned and switch it again
* to percpu mode.
*/
percpu_ref_resurrect(&pool->ref);
/* Drop the ref from zswap_pool_find_get(). */
zswap_pool_put(pool);
}
if (pool)
ret = param_set_charp(s, kp);
else
ret = -EINVAL;
spin_lock_bh(&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_bh(&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)
percpu_ref_kill(&put_pool->ref);
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)
{
int ret = -ENODEV;
/* if this is load-time (pre-init) param setting, only set param. */
if (system_state != SYSTEM_RUNNING)
return param_set_bool(val, kp);
mutex_lock(&zswap_init_lock);
switch (zswap_init_state) {
case ZSWAP_UNINIT:
if (zswap_setup())
break;
fallthrough;
case ZSWAP_INIT_SUCCEED:
if (!zswap_has_pool)
pr_err("can't enable, no pool configured\n");
else
ret = param_set_bool(val, kp);
break;
case ZSWAP_INIT_FAILED:
pr_err("can't enable, initialization failed\n");
}
mutex_unlock(&zswap_init_lock);
return ret;
}
/*********************************
* lru functions
**********************************/
/* should be called under RCU */
#ifdef CONFIG_MEMCG
static inline struct mem_cgroup *mem_cgroup_from_entry(struct zswap_entry *entry)
{
return entry->objcg ? obj_cgroup_memcg(entry->objcg) : NULL;
}
#else
static inline struct mem_cgroup *mem_cgroup_from_entry(struct zswap_entry *entry)
{
return NULL;
}
#endif
static inline int entry_to_nid(struct zswap_entry *entry)
{
return page_to_nid(virt_to_page(entry));
}
static void zswap_lru_add(struct list_lru *list_lru, struct zswap_entry *entry)
{
atomic_long_t *nr_zswap_protected;
unsigned long lru_size, old, new;
int nid = entry_to_nid(entry);
struct mem_cgroup *memcg;
struct lruvec *lruvec;
/*
* Note that it is safe to use rcu_read_lock() here, even in the face of
* concurrent memcg offlining. Thanks to the memcg->kmemcg_id indirection
* used in list_lru lookup, only two scenarios are possible:
*
* 1. list_lru_add() is called before memcg->kmemcg_id is updated. The
* new entry will be reparented to memcg's parent's list_lru.
* 2. list_lru_add() is called after memcg->kmemcg_id is updated. The
* new entry will be added directly to memcg's parent's list_lru.
*
* Similar reasoning holds for list_lru_del().
*/
rcu_read_lock();
memcg = mem_cgroup_from_entry(entry);
/* will always succeed */
list_lru_add(list_lru, &entry->lru, nid, memcg);
/* Update the protection area */
lru_size = list_lru_count_one(list_lru, nid, memcg);
lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(nid));
nr_zswap_protected = &lruvec->zswap_lruvec_state.nr_zswap_protected;
old = atomic_long_inc_return(nr_zswap_protected);
/*
* Decay to avoid overflow and adapt to changing workloads.
* This is based on LRU reclaim cost decaying heuristics.
*/
do {
new = old > lru_size / 4 ? old / 2 : old;
} while (!atomic_long_try_cmpxchg(nr_zswap_protected, &old, new));
rcu_read_unlock();
}
static void zswap_lru_del(struct list_lru *list_lru, struct zswap_entry *entry)
{
int nid = entry_to_nid(entry);
struct mem_cgroup *memcg;
rcu_read_lock();
memcg = mem_cgroup_from_entry(entry);
/* will always succeed */
list_lru_del(list_lru, &entry->lru, nid, memcg);
rcu_read_unlock();
}
void zswap_lruvec_state_init(struct lruvec *lruvec)
{
atomic_long_set(&lruvec->zswap_lruvec_state.nr_zswap_protected, 0);
}
void zswap_folio_swapin(struct folio *folio)
{
struct lruvec *lruvec;
if (folio) {
lruvec = folio_lruvec(folio);
atomic_long_inc(&lruvec->zswap_lruvec_state.nr_zswap_protected);
}
}
void zswap_memcg_offline_cleanup(struct mem_cgroup *memcg)
{
/* lock out zswap shrinker walking memcg tree */
spin_lock(&zswap_shrink_lock);
if (zswap_next_shrink == memcg)
zswap_next_shrink = mem_cgroup_iter(NULL, zswap_next_shrink, NULL);
spin_unlock(&zswap_shrink_lock);
}
/*********************************
* 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;
pgoff_t entry_offset;
while (node) {
entry = rb_entry(node, struct zswap_entry, rbnode);
entry_offset = swp_offset(entry->swpentry);
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;
pgoff_t myentry_offset, entry_offset = swp_offset(entry->swpentry);
while (*link) {
parent = *link;
myentry = rb_entry(parent, struct zswap_entry, rbnode);
myentry_offset = swp_offset(myentry->swpentry);
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)
{
rb_erase(&entry->rbnode, root);
RB_CLEAR_NODE(&entry->rbnode);
}
/*********************************
* zswap entry functions
**********************************/
static struct kmem_cache *zswap_entry_cache;
static struct zswap_entry *zswap_entry_cache_alloc(gfp_t gfp, int nid)
{
struct zswap_entry *entry;
entry = kmem_cache_alloc_node(zswap_entry_cache, gfp, nid);
if (!entry)
return NULL;
RB_CLEAR_NODE(&entry->rbnode);
return entry;
}
static void zswap_entry_cache_free(struct zswap_entry *entry)
{
kmem_cache_free(zswap_entry_cache, entry);
}
static struct zpool *zswap_find_zpool(struct zswap_entry *entry)
{
int i = 0;
if (ZSWAP_NR_ZPOOLS > 1)
i = hash_ptr(entry, ilog2(ZSWAP_NR_ZPOOLS));
return entry->pool->zpools[i];
}
/*
* 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_entry_free(struct zswap_entry *entry)
{
if (!entry->length)
atomic_dec(&zswap_same_filled_pages);
else {
zswap_lru_del(&zswap_list_lru, entry);
zpool_free(zswap_find_zpool(entry), entry->handle);
atomic_dec(&zswap_nr_stored);
zswap_pool_put(entry->pool);
}
if (entry->objcg) {
obj_cgroup_uncharge_zswap(entry->objcg, entry->length);
obj_cgroup_put(entry->objcg);
}
zswap_entry_cache_free(entry);
atomic_dec(&zswap_stored_pages);
zswap_update_total_size();
}
/*
* The caller hold the tree lock and search the entry from the tree,
* so it must be on the tree, remove it from the tree and free it.
*/
static void zswap_invalidate_entry(struct zswap_tree *tree,
struct zswap_entry *entry)
{
zswap_rb_erase(&tree->rbroot, entry);
zswap_entry_free(entry);
}
/*********************************
* compressed storage functions
**********************************/
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;
int ret;
mutex_init(&acomp_ctx->mutex);
acomp_ctx->buffer = kmalloc_node(PAGE_SIZE * 2, GFP_KERNEL, cpu_to_node(cpu));
if (!acomp_ctx->buffer)
return -ENOMEM;
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));
ret = PTR_ERR(acomp);
goto acomp_fail;
}
acomp_ctx->acomp = acomp;
acomp_ctx->is_sleepable = acomp_is_async(acomp);
req = acomp_request_alloc(acomp_ctx->acomp);
if (!req) {
pr_err("could not alloc crypto acomp_request %s\n",
pool->tfm_name);
ret = -ENOMEM;
goto req_fail;
}
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);
return 0;
req_fail:
crypto_free_acomp(acomp_ctx->acomp);
acomp_fail:
kfree(acomp_ctx->buffer);
return ret;
}
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);
kfree(acomp_ctx->buffer);
}
return 0;
}
static bool zswap_compress(struct folio *folio, struct zswap_entry *entry)
{
struct crypto_acomp_ctx *acomp_ctx;
struct scatterlist input, output;
int comp_ret = 0, alloc_ret = 0;
unsigned int dlen = PAGE_SIZE;
unsigned long handle;
struct zpool *zpool;
char *buf;
gfp_t gfp;
u8 *dst;
acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
mutex_lock(&acomp_ctx->mutex);
dst = acomp_ctx->buffer;
sg_init_table(&input, 1);
sg_set_page(&input, &folio->page, PAGE_SIZE, 0);
/*
* We need PAGE_SIZE * 2 here since there maybe over-compression case,
* and hardware-accelerators may won't check the dst buffer size, so
* giving the dst buffer with enough length to avoid buffer overflow.
*/
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, zswap 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 zwap.
* but in different threads running on different cpu, we have different
* acomp instance, so multiple threads can do (de)compression in parallel.
*/
comp_ret = crypto_wait_req(crypto_acomp_compress(acomp_ctx->req), &acomp_ctx->wait);
dlen = acomp_ctx->req->dlen;
if (comp_ret)
goto unlock;
zpool = zswap_find_zpool(entry);
gfp = __GFP_NORETRY | __GFP_NOWARN | __GFP_KSWAPD_RECLAIM;
if (zpool_malloc_support_movable(zpool))
gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
alloc_ret = zpool_malloc(zpool, dlen, gfp, &handle);
if (alloc_ret)
goto unlock;
buf = zpool_map_handle(zpool, handle, ZPOOL_MM_WO);
memcpy(buf, dst, dlen);
zpool_unmap_handle(zpool, handle);
entry->handle = handle;
entry->length = dlen;
unlock:
if (comp_ret == -ENOSPC || alloc_ret == -ENOSPC)
zswap_reject_compress_poor++;
else if (comp_ret)
zswap_reject_compress_fail++;
else if (alloc_ret)
zswap_reject_alloc_fail++;
mutex_unlock(&acomp_ctx->mutex);
return comp_ret == 0 && alloc_ret == 0;
}
static void zswap_decompress(struct zswap_entry *entry, struct page *page)
{
struct zpool *zpool = zswap_find_zpool(entry);
struct scatterlist input, output;
struct crypto_acomp_ctx *acomp_ctx;
u8 *src;
acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
mutex_lock(&acomp_ctx->mutex);
src = zpool_map_handle(zpool, entry->handle, ZPOOL_MM_RO);
/*
* If zpool_map_handle is atomic, we cannot reliably utilize its mapped buffer
* to do crypto_acomp_decompress() which might sleep. In such cases, we must
* resort to copying the buffer to a temporary one.
* Meanwhile, zpool_map_handle() might return a non-linearly mapped buffer,
* such as a kmap address of high memory or even ever a vmap address.
* However, sg_init_one is only equipped to handle linearly mapped low memory.
* In such cases, we also must copy the buffer to a temporary and lowmem one.
*/
if ((acomp_ctx->is_sleepable && !zpool_can_sleep_mapped(zpool)) ||
!virt_addr_valid(src)) {
memcpy(acomp_ctx->buffer, src, entry->length);
src = acomp_ctx->buffer;
zpool_unmap_handle(zpool, entry->handle);
}
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, PAGE_SIZE);
BUG_ON(crypto_wait_req(crypto_acomp_decompress(acomp_ctx->req), &acomp_ctx->wait));
BUG_ON(acomp_ctx->req->dlen != PAGE_SIZE);
mutex_unlock(&acomp_ctx->mutex);
if (src != acomp_ctx->buffer)
zpool_unmap_handle(zpool, entry->handle);
}
/*********************************
* writeback code
**********************************/
/*
* Attempts to free an entry by adding a folio to the swap cache,
* decompressing the entry data into the folio, and issuing a
* bio write to write the folio back to the swap device.
*
* This can be thought of as a "resumed writeback" of the folio
* to the swap device. We are basically resuming the same swap
* writeback path that was intercepted with the zswap_store()
* in the first place. After the folio has been decompressed into
* the swap cache, the compressed version stored by zswap can be
* freed.
*/
static int zswap_writeback_entry(struct zswap_entry *entry,
swp_entry_t swpentry)
{
struct zswap_tree *tree;
struct folio *folio;
struct mempolicy *mpol;
bool folio_was_allocated;
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
};
/* try to allocate swap cache folio */
mpol = get_task_policy(current);
folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
NO_INTERLEAVE_INDEX, &folio_was_allocated, true);
if (!folio)
return -ENOMEM;
/*
* Found an existing folio, we raced with swapin or concurrent
* shrinker. We generally writeback cold folios from zswap, and
* swapin means the folio just became hot, so skip this folio.
* For unlikely concurrent shrinker case, it will be unlinked
* and freed when invalidated by the concurrent shrinker anyway.
*/
if (!folio_was_allocated) {
folio_put(folio);
return -EEXIST;
}
/*
* folio is locked, and the swapcache is now secured against
* concurrent swapping to and from the slot, and concurrent
* swapoff so we can safely dereference the zswap tree here.
* Verify that the swap entry hasn't been invalidated and recycled
* behind our backs, to avoid overwriting a new swap folio with
* old compressed data. Only when this is successful can the entry
* be dereferenced.
*/
tree = swap_zswap_tree(swpentry);
spin_lock(&tree->lock);
if (zswap_rb_search(&tree->rbroot, swp_offset(swpentry)) != entry) {
spin_unlock(&tree->lock);
delete_from_swap_cache(folio);
folio_unlock(folio);
folio_put(folio);
return -ENOMEM;
}
/* Safe to deref entry after the entry is verified above. */
zswap_rb_erase(&tree->rbroot, entry);
spin_unlock(&tree->lock);
zswap_decompress(entry, &folio->page);
count_vm_event(ZSWPWB);
if (entry->objcg)
count_objcg_event(entry->objcg, ZSWPWB);
zswap_entry_free(entry);
/* folio is up to date */
folio_mark_uptodate(folio);
/* move it to the tail of the inactive list after end_writeback */
folio_set_reclaim(folio);
/* start writeback */
__swap_writepage(folio, &wbc);
folio_put(folio);
return 0;
}
/*********************************
* shrinker functions
**********************************/
static enum lru_status shrink_memcg_cb(struct list_head *item, struct list_lru_one *l,
spinlock_t *lock, void *arg)
{
struct zswap_entry *entry = container_of(item, struct zswap_entry, lru);
bool *encountered_page_in_swapcache = (bool *)arg;
swp_entry_t swpentry;
enum lru_status ret = LRU_REMOVED_RETRY;
int writeback_result;
/*
* As soon as we drop the LRU lock, the entry can be freed by
* a concurrent invalidation. This means the following:
*
* 1. We extract the swp_entry_t to the stack, allowing
* zswap_writeback_entry() to pin the swap entry and
* then validate the zwap entry against that swap entry's
* tree using pointer value comparison. Only when that
* is successful can the entry be dereferenced.
*
* 2. Usually, objects are taken off the LRU for reclaim. In
* this case this isn't possible, because if reclaim fails
* for whatever reason, we have no means of knowing if the
* entry is alive to put it back on the LRU.
*
* So rotate it before dropping the lock. If the entry is
* written back or invalidated, the free path will unlink
* it. For failures, rotation is the right thing as well.
*
* Temporary failures, where the same entry should be tried
* again immediately, almost never happen for this shrinker.
* We don't do any trylocking; -ENOMEM comes closest,
* but that's extremely rare and doesn't happen spuriously
* either. Don't bother distinguishing this case.
*/
list_move_tail(item, &l->list);
/*
* Once the lru lock is dropped, the entry might get freed. The
* swpentry is copied to the stack, and entry isn't deref'd again
* until the entry is verified to still be alive in the tree.
*/
swpentry = entry->swpentry;
/*
* It's safe to drop the lock here because we return either
* LRU_REMOVED_RETRY or LRU_RETRY.
*/
spin_unlock(lock);
writeback_result = zswap_writeback_entry(entry, swpentry);
if (writeback_result) {
zswap_reject_reclaim_fail++;
ret = LRU_RETRY;
/*
* Encountering a page already in swap cache is a sign that we are shrinking
* into the warmer region. We should terminate shrinking (if we're in the dynamic
* shrinker context).
*/
if (writeback_result == -EEXIST && encountered_page_in_swapcache) {
ret = LRU_STOP;
*encountered_page_in_swapcache = true;
}
} else {
zswap_written_back_pages++;
}
spin_lock(lock);
return ret;
}
static unsigned long zswap_shrinker_scan(struct shrinker *shrinker,
struct shrink_control *sc)
{
struct lruvec *lruvec = mem_cgroup_lruvec(sc->memcg, NODE_DATA(sc->nid));
unsigned long shrink_ret, nr_protected, lru_size;
bool encountered_page_in_swapcache = false;
if (!zswap_shrinker_enabled ||
!mem_cgroup_zswap_writeback_enabled(sc->memcg)) {
sc->nr_scanned = 0;
return SHRINK_STOP;
}
nr_protected =
atomic_long_read(&lruvec->zswap_lruvec_state.nr_zswap_protected);
lru_size = list_lru_shrink_count(&zswap_list_lru, sc);
/*
* Abort if we are shrinking into the protected region.
*
* This short-circuiting is necessary because if we have too many multiple
* concurrent reclaimers getting the freeable zswap object counts at the
* same time (before any of them made reasonable progress), the total
* number of reclaimed objects might be more than the number of unprotected
* objects (i.e the reclaimers will reclaim into the protected area of the
* zswap LRU).
*/
if (nr_protected >= lru_size - sc->nr_to_scan) {
sc->nr_scanned = 0;
return SHRINK_STOP;
}
shrink_ret = list_lru_shrink_walk(&zswap_list_lru, sc, &shrink_memcg_cb,
&encountered_page_in_swapcache);
if (encountered_page_in_swapcache)
return SHRINK_STOP;
return shrink_ret ? shrink_ret : SHRINK_STOP;
}
static unsigned long zswap_shrinker_count(struct shrinker *shrinker,
struct shrink_control *sc)
{
struct mem_cgroup *memcg = sc->memcg;
struct lruvec *lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(sc->nid));
unsigned long nr_backing, nr_stored, nr_freeable, nr_protected;
if (!zswap_shrinker_enabled || !mem_cgroup_zswap_writeback_enabled(memcg))
return 0;
/*
* The shrinker resumes swap writeback, which will enter block
* and may enter fs. XXX: Harmonize with vmscan.c __GFP_FS
* rules (may_enter_fs()), which apply on a per-folio basis.
*/
if (!gfp_has_io_fs(sc->gfp_mask))
return 0;
/*
* For memcg, use the cgroup-wide ZSWAP stats since we don't
* have them per-node and thus per-lruvec. Careful if memcg is
* runtime-disabled: we can get sc->memcg == NULL, which is ok
* for the lruvec, but not for memcg_page_state().
*
* Without memcg, use the zswap pool-wide metrics.
*/
if (!mem_cgroup_disabled()) {
mem_cgroup_flush_stats(memcg);
nr_backing = memcg_page_state(memcg, MEMCG_ZSWAP_B) >> PAGE_SHIFT;
nr_stored = memcg_page_state(memcg, MEMCG_ZSWAPPED);
} else {
nr_backing = zswap_pool_total_size >> PAGE_SHIFT;
nr_stored = atomic_read(&zswap_nr_stored);
}
if (!nr_stored)
return 0;
nr_protected =
atomic_long_read(&lruvec->zswap_lruvec_state.nr_zswap_protected);
nr_freeable = list_lru_shrink_count(&zswap_list_lru, sc);
/*
* Subtract the lru size by an estimate of the number of pages
* that should be protected.
*/
nr_freeable = nr_freeable > nr_protected ? nr_freeable - nr_protected : 0;
/*
* Scale the number of freeable pages by the memory saving factor.
* This ensures that the better zswap compresses memory, the fewer
* pages we will evict to swap (as it will otherwise incur IO for
* relatively small memory saving).
*/
return mult_frac(nr_freeable, nr_backing, nr_stored);
}
static struct shrinker *zswap_alloc_shrinker(void)
{
struct shrinker *shrinker;
shrinker =
shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE, "mm-zswap");
if (!shrinker)
return NULL;
shrinker->scan_objects = zswap_shrinker_scan;
shrinker->count_objects = zswap_shrinker_count;
shrinker->batch = 0;
shrinker->seeks = DEFAULT_SEEKS;
return shrinker;
}
static int shrink_memcg(struct mem_cgroup *memcg)
{
int nid, shrunk = 0;
if (!mem_cgroup_zswap_writeback_enabled(memcg))
return -EINVAL;
/*
* Skip zombies because their LRUs are reparented and we would be
* reclaiming from the parent instead of the dead memcg.
*/
if (memcg && !mem_cgroup_online(memcg))
return -ENOENT;
for_each_node_state(nid, N_NORMAL_MEMORY) {
unsigned long nr_to_walk = 1;
shrunk += list_lru_walk_one(&zswap_list_lru, nid, memcg,
&shrink_memcg_cb, NULL, &nr_to_walk);
}
return shrunk ? 0 : -EAGAIN;
}
static void shrink_worker(struct work_struct *w)
{
struct mem_cgroup *memcg;
int ret, failures = 0;
/* global reclaim will select cgroup in a round-robin fashion. */
do {
spin_lock(&zswap_shrink_lock);
zswap_next_shrink = mem_cgroup_iter(NULL, zswap_next_shrink, NULL);
memcg = zswap_next_shrink;
/*
* We need to retry if we have gone through a full round trip, or if we
* got an offline memcg (or else we risk undoing the effect of the
* zswap memcg offlining cleanup callback). This is not catastrophic
* per se, but it will keep the now offlined memcg hostage for a while.
*
* Note that if we got an online memcg, we will keep the extra
* reference in case the original reference obtained by mem_cgroup_iter
* is dropped by the zswap memcg offlining callback, ensuring that the
* memcg is not killed when we are reclaiming.
*/
if (!memcg) {
spin_unlock(&zswap_shrink_lock);
if (++failures == MAX_RECLAIM_RETRIES)
break;
goto resched;
}
if (!mem_cgroup_tryget_online(memcg)) {
/* drop the reference from mem_cgroup_iter() */
mem_cgroup_iter_break(NULL, memcg);
zswap_next_shrink = NULL;
spin_unlock(&zswap_shrink_lock);
if (++failures == MAX_RECLAIM_RETRIES)
break;
goto resched;
}
spin_unlock(&zswap_shrink_lock);
ret = shrink_memcg(memcg);
/* drop the extra reference */
mem_cgroup_put(memcg);
if (ret == -EINVAL)
break;
if (ret && ++failures == MAX_RECLAIM_RETRIES)
break;
resched:
cond_resched();
} while (!zswap_can_accept());
}
static int zswap_is_page_same_filled(void *ptr, unsigned long *value)
{
unsigned long *page;
unsigned long val;
unsigned int pos, last_pos = PAGE_SIZE / sizeof(*page) - 1;
page = (unsigned long *)ptr;
val = page[0];
if (val != page[last_pos])
return 0;
for (pos = 1; pos < last_pos; pos++) {
if (val != page[pos])
return 0;
}
*value = val;
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));
}
bool zswap_store(struct folio *folio)
{
swp_entry_t swp = folio->swap;
pgoff_t offset = swp_offset(swp);
struct zswap_tree *tree = swap_zswap_tree(swp);
struct zswap_entry *entry, *dupentry;
struct obj_cgroup *objcg = NULL;
struct mem_cgroup *memcg = NULL;
VM_WARN_ON_ONCE(!folio_test_locked(folio));
VM_WARN_ON_ONCE(!folio_test_swapcache(folio));
/* Large folios aren't supported */
if (folio_test_large(folio))
return false;
if (!zswap_enabled)
goto check_old;
objcg = get_obj_cgroup_from_folio(folio);
if (objcg && !obj_cgroup_may_zswap(objcg)) {
memcg = get_mem_cgroup_from_objcg(objcg);
if (shrink_memcg(memcg)) {
mem_cgroup_put(memcg);
goto reject;
}
mem_cgroup_put(memcg);
}
/* 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())
goto shrink;
else
zswap_pool_reached_full = false;
}
/* allocate entry */
entry = zswap_entry_cache_alloc(GFP_KERNEL, folio_nid(folio));
if (!entry) {
zswap_reject_kmemcache_fail++;
goto reject;
}
if (zswap_same_filled_pages_enabled) {
unsigned long value;
u8 *src;
src = kmap_local_folio(folio, 0);
if (zswap_is_page_same_filled(src, &value)) {
kunmap_local(src);
entry->length = 0;
entry->value = value;
atomic_inc(&zswap_same_filled_pages);
goto insert_entry;
}
kunmap_local(src);
}
if (!zswap_non_same_filled_pages_enabled)
goto freepage;
/* if entry is successfully added, it keeps the reference */
entry->pool = zswap_pool_current_get();
if (!entry->pool)
goto freepage;
if (objcg) {
memcg = get_mem_cgroup_from_objcg(objcg);
if (memcg_list_lru_alloc(memcg, &zswap_list_lru, GFP_KERNEL)) {
mem_cgroup_put(memcg);
goto put_pool;
}
mem_cgroup_put(memcg);
}
if (!zswap_compress(folio, entry))
goto put_pool;
insert_entry:
entry->swpentry = swp;
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);
/*
* The folio may have been dirtied again, invalidate the
* possibly stale entry before inserting the new entry.
*/
if (zswap_rb_insert(&tree->rbroot, entry, &dupentry) == -EEXIST) {
zswap_invalidate_entry(tree, dupentry);
WARN_ON(zswap_rb_insert(&tree->rbroot, entry, &dupentry));
}
if (entry->length) {
INIT_LIST_HEAD(&entry->lru);
zswap_lru_add(&zswap_list_lru, entry);
atomic_inc(&zswap_nr_stored);
}
spin_unlock(&tree->lock);
/* update stats */
atomic_inc(&zswap_stored_pages);
zswap_update_total_size();
count_vm_event(ZSWPOUT);
return true;
put_pool:
zswap_pool_put(entry->pool);
freepage:
zswap_entry_cache_free(entry);
reject:
if (objcg)
obj_cgroup_put(objcg);
check_old:
/*
* If the zswap store fails or zswap is disabled, we must invalidate the
* possibly stale entry which was previously stored at this offset.
* Otherwise, writeback could overwrite the new data in the swapfile.
*/
spin_lock(&tree->lock);
entry = zswap_rb_search(&tree->rbroot, offset);
if (entry)
zswap_invalidate_entry(tree, entry);
spin_unlock(&tree->lock);
return false;
shrink:
queue_work(shrink_wq, &zswap_shrink_work);
goto reject;
}
bool zswap_load(struct folio *folio)
{
swp_entry_t swp = folio->swap;
pgoff_t offset = swp_offset(swp);
struct page *page = &folio->page;
bool swapcache = folio_test_swapcache(folio);
struct zswap_tree *tree = swap_zswap_tree(swp);
struct zswap_entry *entry;
u8 *dst;
VM_WARN_ON_ONCE(!folio_test_locked(folio));
spin_lock(&tree->lock);
entry = zswap_rb_search(&tree->rbroot, offset);
if (!entry) {
spin_unlock(&tree->lock);
return false;
}
/*
* When reading into the swapcache, invalidate our entry. The
* swapcache can be the authoritative owner of the page and
* its mappings, and the pressure that results from having two
* in-memory copies outweighs any benefits of caching the
* compression work.
*
* (Most swapins go through the swapcache. The notable
* exception is the singleton fault on SWP_SYNCHRONOUS_IO
* files, which reads into a private page and may free it if
* the fault fails. We remain the primary owner of the entry.)
*/
if (swapcache)
zswap_rb_erase(&tree->rbroot, entry);
spin_unlock(&tree->lock);
if (entry->length)
zswap_decompress(entry, page);
else {
dst = kmap_local_page(page);
zswap_fill_page(dst, entry->value);
kunmap_local(dst);
}
count_vm_event(ZSWPIN);
if (entry->objcg)
count_objcg_event(entry->objcg, ZSWPIN);
if (swapcache) {
zswap_entry_free(entry);
folio_mark_dirty(folio);
}
return true;
}
void zswap_invalidate(swp_entry_t swp)
{
pgoff_t offset = swp_offset(swp);
struct zswap_tree *tree = swap_zswap_tree(swp);
struct zswap_entry *entry;
spin_lock(&tree->lock);
entry = zswap_rb_search(&tree->rbroot, offset);
if (entry)
zswap_invalidate_entry(tree, entry);
spin_unlock(&tree->lock);
}
int zswap_swapon(int type, unsigned long nr_pages)
{
struct zswap_tree *trees, *tree;
unsigned int nr, i;
nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
trees = kvcalloc(nr, sizeof(*tree), GFP_KERNEL);
if (!trees) {
pr_err("alloc failed, zswap disabled for swap type %d\n", type);
return -ENOMEM;
}
for (i = 0; i < nr; i++) {
tree = trees + i;
tree->rbroot = RB_ROOT;
spin_lock_init(&tree->lock);
}
nr_zswap_trees[type] = nr;
zswap_trees[type] = trees;
return 0;
}
void zswap_swapoff(int type)
{
struct zswap_tree *trees = zswap_trees[type];
unsigned int i;
if (!trees)
return;
/* try_to_unuse() invalidated all the entries already */
for (i = 0; i < nr_zswap_trees[type]; i++)
WARN_ON_ONCE(!RB_EMPTY_ROOT(&trees[i].rbroot));
kvfree(trees);
nr_zswap_trees[type] = 0;
zswap_trees[type] = NULL;
}
/*********************************
* debugfs functions
**********************************/
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
static struct dentry *zswap_debugfs_root;
static int 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_fail", 0444,
zswap_debugfs_root, &zswap_reject_compress_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("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 zswap_debugfs_init(void)
{
return 0;
}
#endif
/*********************************
* module init and exit
**********************************/
static int zswap_setup(void)
{
struct zswap_pool *pool;
int ret;
zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
if (!zswap_entry_cache) {
pr_err("entry cache creation failed\n");
goto cache_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;
shrink_wq = alloc_workqueue("zswap-shrink",
WQ_UNBOUND|WQ_MEM_RECLAIM, 1);
if (!shrink_wq)
goto shrink_wq_fail;
zswap_shrinker = zswap_alloc_shrinker();
if (!zswap_shrinker)
goto shrinker_fail;
if (list_lru_init_memcg(&zswap_list_lru, zswap_shrinker))
goto lru_fail;
shrinker_register(zswap_shrinker);
INIT_WORK(&zswap_shrink_work, shrink_worker);
pool = __zswap_pool_create_fallback();
if (pool) {
pr_info("loaded using pool %s/%s\n", pool->tfm_name,
zpool_get_type(pool->zpools[0]));
list_add(&pool->list, &zswap_pools);
zswap_has_pool = true;
} else {
pr_err("pool creation failed\n");
zswap_enabled = false;
}
if (zswap_debugfs_init())
pr_warn("debugfs initialization failed\n");
zswap_init_state = ZSWAP_INIT_SUCCEED;
return 0;
lru_fail:
shrinker_free(zswap_shrinker);
shrinker_fail:
destroy_workqueue(shrink_wq);
shrink_wq_fail:
cpuhp_remove_multi_state(CPUHP_MM_ZSWP_POOL_PREPARE);
hp_fail:
kmem_cache_destroy(zswap_entry_cache);
cache_fail:
/* if built-in, we aren't unloaded on failure; don't allow use */
zswap_init_state = ZSWAP_INIT_FAILED;
zswap_enabled = false;
return -ENOMEM;
}
static int __init zswap_init(void)
{
if (!zswap_enabled)
return 0;
return zswap_setup();
}
/* must be late so crypto has time to come up */
late_initcall(zswap_init);
MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
MODULE_DESCRIPTION("Compressed cache for swap pages");