linux/mm/zswap.c
Dan Streetman d7b028f56a zswap: disable changing params if init fails
Add zswap_init_failed bool that prevents changing any of the module
params, if init_zswap() fails, and set zswap_enabled to false.  Change
'enabled' param to a callback, and check zswap_init_failed before
allowing any change to 'enabled', 'zpool', or 'compressor' params.

Any driver that is built-in to the kernel will not be unloaded if its
init function returns error, and its module params remain accessible for
users to change via sysfs.  Since zswap uses param callbacks, which
assume that zswap has been initialized, changing the zswap params after
a failed initialization will result in WARNING due to the param
callbacks expecting a pool to already exist.  This prevents that by
immediately exiting any of the param callbacks if initialization failed.

This was reported here:
  https://marc.info/?l=linux-mm&m=147004228125528&w=4

And fixes this WARNING:
  [  429.723476] WARNING: CPU: 0 PID: 5140 at mm/zswap.c:503 __zswap_pool_current+0x56/0x60

The warning is just noise, and not serious.  However, when init fails,
zswap frees all its percpu dstmem pages and its kmem cache.  The kmem
cache might be serious, if kmem_cache_alloc(NULL, gfp) has problems; but
the percpu dstmem pages are definitely a problem, as they're used as
temporary buffer for compressed pages before copying into place in the
zpool.

If the user does get zswap enabled after an init failure, then zswap
will likely Oops on the first page it tries to compress (or worse, start
corrupting memory).

Fixes: 90b0fc26d5 ("zswap: change zpool/compressor at runtime")
Link: http://lkml.kernel.org/r/20170124200259.16191-2-ddstreet@ieee.org
Signed-off-by: Dan Streetman <dan.streetman@canonical.com>
Reported-by: Marcin Miroslaw <marcin@mejor.pl>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-02-03 14:13:19 -08:00

1240 lines
31 KiB
C

/*
* 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 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
**********************************/
/* 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);
/*********************************
* 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
* pool - the zswap_pool the entry's data is in
* handle - zpool allocation handle that stores the compressed page data
*/
struct zswap_entry {
struct rb_node rbnode;
pgoff_t offset;
int refcount;
unsigned int length;
struct zswap_pool *pool;
unsigned long handle;
};
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;
/*********************************
* 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)
{
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) {
pr_err("can't allocate compressor buffer\n");
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_ON(!pool);
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 (!pool || !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;
if (!WARN_ON(!last) && !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;
pool = kzalloc(sizeof(*pool), GFP_KERNEL);
if (!pool) {
pr_err("pool alloc failed\n");
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)
{
if (!crypto_has_comp(zswap_compressor, 0, 0)) {
if (!strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {
pr_err("default compressor %s not available\n",
zswap_compressor);
return NULL;
}
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;
}
if (!zpool_has_pool(zswap_zpool_type)) {
if (!strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {
pr_err("default zpool %s not available\n",
zswap_zpool_type);
return NULL;
}
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;
}
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)
{
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))
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);
list_del_rcu(&pool->list);
} else {
spin_unlock(&zswap_pools_lock);
pool = zswap_pool_create(type, compressor);
spin_lock(&zswap_pools_lock);
}
if (pool)
ret = param_set_charp(s, kp);
else
ret = -EINVAL;
if (!ret) {
put_pool = zswap_pool_current();
list_add_rcu(&pool->list, &zswap_pools);
} 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);
/* 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;
}
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;
}
/*********************************
* 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 dlen = PAGE_SIZE, len;
unsigned long handle;
char *buf;
u8 *src, *dst;
struct zswap_header *zhdr;
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;
}
}
/* allocate entry */
entry = zswap_entry_cache_alloc(GFP_KERNEL);
if (!entry) {
zswap_reject_kmemcache_fail++;
ret = -ENOMEM;
goto reject;
}
/* 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 */
len = dlen + sizeof(struct zswap_header);
ret = zpool_malloc(entry->pool->zpool, len,
__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;
}
zhdr = zpool_map_handle(entry->pool->zpool, handle, ZPOOL_MM_RW);
zhdr->swpentry = swp_entry(type, offset);
buf = (u8 *)(zhdr + 1);
memcpy(buf, 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;
/* 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);
/* 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);
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(struct zswap_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", S_IRUGO,
zswap_debugfs_root, &zswap_pool_limit_hit);
debugfs_create_u64("reject_reclaim_fail", S_IRUGO,
zswap_debugfs_root, &zswap_reject_reclaim_fail);
debugfs_create_u64("reject_alloc_fail", S_IRUGO,
zswap_debugfs_root, &zswap_reject_alloc_fail);
debugfs_create_u64("reject_kmemcache_fail", S_IRUGO,
zswap_debugfs_root, &zswap_reject_kmemcache_fail);
debugfs_create_u64("reject_compress_poor", S_IRUGO,
zswap_debugfs_root, &zswap_reject_compress_poor);
debugfs_create_u64("written_back_pages", S_IRUGO,
zswap_debugfs_root, &zswap_written_back_pages);
debugfs_create_u64("duplicate_entry", S_IRUGO,
zswap_debugfs_root, &zswap_duplicate_entry);
debugfs_create_u64("pool_total_size", S_IRUGO,
zswap_debugfs_root, &zswap_pool_total_size);
debugfs_create_atomic_t("stored_pages", S_IRUGO,
zswap_debugfs_root, &zswap_stored_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_err("pool creation failed\n");
goto pool_fail;
}
pr_info("loaded using pool %s/%s\n", pool->tfm_name,
zpool_get_type(pool->zpool));
list_add(&pool->list, &zswap_pools);
frontswap_register_ops(&zswap_frontswap_ops);
if (zswap_debugfs_init())
pr_warn("debugfs initialization failed\n");
return 0;
pool_fail:
cpuhp_remove_state_nocalls(CPUHP_MM_ZSWP_POOL_PREPARE);
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");