/*
* 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/zbud.h>
#include <linux/mm_types.h>
#include <linux/page-flags.h>
#include <linux/swapops.h>
#include <linux/writeback.h>
#include <linux/pagemap.h>
/*********************************
* statistics
**********************************/
/* Number of memory pages used by the compressed pool */
static u64 zswap_pool_pages;
/* 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, fixed at boot for now) */
static bool zswap_enabled __read_mostly;
module_param_named(enabled, zswap_enabled, bool, 0);
/* Compressor to be used by zswap (fixed at boot for now) */
#define ZSWAP_COMPRESSOR_DEFAULT "lzo"
static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
module_param_named(compressor, zswap_compressor, charp, 0);
/* 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);
/*********************************
* compression functions
**********************************/
/* per-cpu compression transforms */
static struct crypto_comp * __percpu *zswap_comp_pcpu_tfms;
enum comp_op {
ZSWAP_COMPOP_COMPRESS,
ZSWAP_COMPOP_DECOMPRESS
};
static int zswap_comp_op(enum comp_op op, const u8 *src, unsigned int slen,
u8 *dst, unsigned int *dlen)
{
struct crypto_comp *tfm;
int ret;
tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, get_cpu());
switch (op) {
case ZSWAP_COMPOP_COMPRESS:
ret = crypto_comp_compress(tfm, src, slen, dst, dlen);
break;
case ZSWAP_COMPOP_DECOMPRESS:
ret = crypto_comp_decompress(tfm, src, slen, dst, dlen);
break;
default:
ret = -EINVAL;
}
put_cpu();
return ret;
}
static int __init zswap_comp_init(void)
{
if (!crypto_has_comp(zswap_compressor, 0, 0)) {
pr_info("%s compressor not available\n", zswap_compressor);
/* fall back to default compressor */
zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
if (!crypto_has_comp(zswap_compressor, 0, 0))
/* can't even load the default compressor */
return -ENODEV;
}
pr_info("using %s compressor\n", zswap_compressor);
/* alloc percpu transforms */
zswap_comp_pcpu_tfms = alloc_percpu(struct crypto_comp *);
if (!zswap_comp_pcpu_tfms)
return -ENOMEM;
return 0;
}
static void zswap_comp_exit(void)
{
/* free percpu transforms */
if (zswap_comp_pcpu_tfms)
free_percpu(zswap_comp_pcpu_tfms);
}
/*********************************
* data structures
**********************************/
/*
* 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
* refcount - the number of outstanding reference to the entry. This is needed
* to protect against premature freeing of the entry by code
* concurent 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.
* offset - the swap offset for the entry. Index into the red-black tree.
* handle - zsmalloc allocation handle that stores the compressed page data
* length - the length in bytes of the compressed page data. Needed during
* decompression
*/
struct zswap_entry {
struct rb_node rbnode;
pgoff_t offset;
int refcount;
unsigned int length;
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;
struct zbud_pool *pool;
};
static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
/*********************************
* zswap entry functions
**********************************/
static struct kmem_cache *zswap_entry_cache;
static int zswap_entry_cache_create(void)
{
zswap_entry_cache = KMEM_CACHE(zswap_entry, 0);
return (zswap_entry_cache == NULL);
}
static void zswap_entry_cache_destory(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;
return entry;
}
static void zswap_entry_cache_free(struct zswap_entry *entry)
{
kmem_cache_free(zswap_entry_cache, entry);
}
/* caller must hold the tree lock */
static void zswap_entry_get(struct zswap_entry *entry)
{
entry->refcount++;
}
/* caller must hold the tree lock */
static int zswap_entry_put(struct zswap_entry *entry)
{
entry->refcount--;
return entry->refcount;
}
/*********************************
* 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;
}
/*********************************
* per-cpu code
**********************************/
static DEFINE_PER_CPU(u8 *, zswap_dstmem);
static int __zswap_cpu_notifier(unsigned long action, unsigned long cpu)
{
struct crypto_comp *tfm;
u8 *dst;
switch (action) {
case CPU_UP_PREPARE:
tfm = crypto_alloc_comp(zswap_compressor, 0, 0);
if (IS_ERR(tfm)) {
pr_err("can't allocate compressor transform\n");
return NOTIFY_BAD;
}
*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = tfm;
dst = kmalloc(PAGE_SIZE * 2, GFP_KERNEL);
if (!dst) {
pr_err("can't allocate compressor buffer\n");
crypto_free_comp(tfm);
*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
return NOTIFY_BAD;
}
per_cpu(zswap_dstmem, cpu) = dst;
break;
case CPU_DEAD:
case CPU_UP_CANCELED:
tfm = *per_cpu_ptr(zswap_comp_pcpu_tfms, cpu);
if (tfm) {
crypto_free_comp(tfm);
*per_cpu_ptr(zswap_comp_pcpu_tfms, cpu) = NULL;
}
dst = per_cpu(zswap_dstmem, cpu);
kfree(dst);
per_cpu(zswap_dstmem, cpu) = NULL;
break;
default:
break;
}
return NOTIFY_OK;
}
static int zswap_cpu_notifier(struct notifier_block *nb,
unsigned long action, void *pcpu)
{
unsigned long cpu = (unsigned long)pcpu;
return __zswap_cpu_notifier(action, cpu);
}
static struct notifier_block zswap_cpu_notifier_block = {
.notifier_call = zswap_cpu_notifier
};
static int zswap_cpu_init(void)
{
unsigned long cpu;
get_online_cpus();
for_each_online_cpu(cpu)
if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
goto cleanup;
register_cpu_notifier(&zswap_cpu_notifier_block);
put_online_cpus();
return 0;
cleanup:
for_each_online_cpu(cpu)
__zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
put_online_cpus();
return -ENOMEM;
}
/*********************************
* helpers
**********************************/
static bool zswap_is_full(void)
{
return (totalram_pages * zswap_max_pool_percent / 100 <
zswap_pool_pages);
}
/*
* Carries out the common pattern of freeing and entry's zsmalloc allocation,
* freeing the entry itself, and decrementing the number of stored pages.
*/
static void zswap_free_entry(struct zswap_tree *tree, struct zswap_entry *entry)
{
zbud_free(tree->pool, entry->handle);
zswap_entry_cache_free(entry);
atomic_dec(&zswap_stored_pages);
zswap_pool_pages = zbud_get_pool_size(tree->pool);
}
/*********************************
* 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)
{
struct page *found_page, *new_page = NULL;
struct address_space *swapper_space = swap_address_space(entry);
int err;
*retpage = NULL;
do {
/*
* First check the swap cache. Since this is normally
* called after lookup_swap_cache() failed, re-calling
* that would confuse statistics.
*/
found_page = find_get_page(swapper_space, entry.val);
if (found_page)
break;
/*
* Get a new page to read into from swap.
*/
if (!new_page) {
new_page = alloc_page(GFP_KERNEL);
if (!new_page)
break; /* Out of memory */
}
/*
* call radix_tree_preload() while we can wait.
*/
err = radix_tree_preload(GFP_KERNEL);
if (err)
break;
/*
* Swap entry may have been freed since our caller observed it.
*/
err = swapcache_prepare(entry);
if (err == -EEXIST) { /* seems racy */
radix_tree_preload_end();
continue;
}
if (err) { /* swp entry is obsolete ? */
radix_tree_preload_end();
break;
}
/* May fail (-ENOMEM) if radix-tree node allocation failed. */
__set_page_locked(new_page);
SetPageSwapBacked(new_page);
err = __add_to_swap_cache(new_page, entry);
if (likely(!err)) {
radix_tree_preload_end();
lru_cache_add_anon(new_page);
*retpage = new_page;
return ZSWAP_SWAPCACHE_NEW;
}
radix_tree_preload_end();
ClearPageSwapBacked(new_page);
__clear_page_locked(new_page);
/*
* add_to_swap_cache() doesn't return -EEXIST, so we can safely
* clear SWAP_HAS_CACHE flag.
*/
swapcache_free(entry, NULL);
} while (err != -ENOMEM);
if (new_page)
page_cache_release(new_page);
if (!found_page)
return ZSWAP_SWAPCACHE_FAIL;
*retpage = found_page;
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 zbud_pool *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;
u8 *src, *dst;
unsigned int dlen;
int ret, refcount;
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
};
/* extract swpentry from data */
zhdr = zbud_map(pool, handle);
swpentry = zhdr->swpentry; /* here */
zbud_unmap(pool, handle);
tree = zswap_trees[swp_type(swpentry)];
offset = swp_offset(swpentry);
BUG_ON(pool != tree->pool);
/* find and ref zswap entry */
spin_lock(&tree->lock);
entry = zswap_rb_search(&tree->rbroot, offset);
if (!entry) {
/* entry was invalidated */
spin_unlock(&tree->lock);
return 0;
}
zswap_entry_get(entry);
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 */
page_cache_release(page);
ret = -EEXIST;
goto fail;
case ZSWAP_SWAPCACHE_NEW: /* page is locked */
/* decompress */
dlen = PAGE_SIZE;
src = (u8 *)zbud_map(tree->pool, entry->handle) +
sizeof(struct zswap_header);
dst = kmap_atomic(page);
ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src,
entry->length, dst, &dlen);
kunmap_atomic(dst);
zbud_unmap(tree->pool, 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);
page_cache_release(page);
zswap_written_back_pages++;
spin_lock(&tree->lock);
/* drop local reference */
zswap_entry_put(entry);
/* drop the initial reference from entry creation */
refcount = zswap_entry_put(entry);
/*
* There are three possible values for refcount here:
* (1) refcount is 1, load is in progress, unlink from rbtree,
* load will free
* (2) refcount is 0, (normal case) entry is valid,
* remove from rbtree and free entry
* (3) refcount is -1, invalidate happened during writeback,
* free entry
*/
if (refcount >= 0) {
/* no invalidate yet, remove from rbtree */
rb_erase(&entry->rbnode, &tree->rbroot);
}
spin_unlock(&tree->lock);
if (refcount <= 0) {
/* free the entry */
zswap_free_entry(tree, entry);
return 0;
}
return -EAGAIN;
fail:
spin_lock(&tree->lock);
refcount = zswap_entry_put(entry);
if (refcount <= 0) {
/* invalidate happened, consider writeback as success */
zswap_free_entry(tree, entry);
ret = 0;
}
spin_unlock(&tree->lock);
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;
int ret;
unsigned int dlen = PAGE_SIZE, len;
unsigned long handle;
char *buf;
u8 *src, *dst;
struct zswap_header *zhdr;
if (!tree) {
ret = -ENODEV;
goto reject;
}
/* reclaim space if needed */
if (zswap_is_full()) {
zswap_pool_limit_hit++;
if (zbud_reclaim_page(tree->pool, 8)) {
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;
}
/* compress */
dst = get_cpu_var(zswap_dstmem);
src = kmap_atomic(page);
ret = zswap_comp_op(ZSWAP_COMPOP_COMPRESS, src, PAGE_SIZE, dst, &dlen);
kunmap_atomic(src);
if (ret) {
ret = -EINVAL;
goto freepage;
}
/* store */
len = dlen + sizeof(struct zswap_header);
ret = zbud_alloc(tree->pool, len, __GFP_NORETRY | __GFP_NOWARN,
&handle);
if (ret == -ENOSPC) {
zswap_reject_compress_poor++;
goto freepage;
}
if (ret) {
zswap_reject_alloc_fail++;
goto freepage;
}
zhdr = zbud_map(tree->pool, handle);
zhdr->swpentry = swp_entry(type, offset);
buf = (u8 *)(zhdr + 1);
memcpy(buf, dst, dlen);
zbud_unmap(tree->pool, 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 */
rb_erase(&dupentry->rbnode, &tree->rbroot);
if (!zswap_entry_put(dupentry)) {
/* free */
zswap_free_entry(tree, dupentry);
}
}
} while (ret == -EEXIST);
spin_unlock(&tree->lock);
/* update stats */
atomic_inc(&zswap_stored_pages);
zswap_pool_pages = zbud_get_pool_size(tree->pool);
return 0;
freepage:
put_cpu_var(zswap_dstmem);
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;
u8 *src, *dst;
unsigned int dlen;
int refcount, ret;
/* find */
spin_lock(&tree->lock);
entry = zswap_rb_search(&tree->rbroot, offset);
if (!entry) {
/* entry was written back */
spin_unlock(&tree->lock);
return -1;
}
zswap_entry_get(entry);
spin_unlock(&tree->lock);
/* decompress */
dlen = PAGE_SIZE;
src = (u8 *)zbud_map(tree->pool, entry->handle) +
sizeof(struct zswap_header);
dst = kmap_atomic(page);
ret = zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
dst, &dlen);
kunmap_atomic(dst);
zbud_unmap(tree->pool, entry->handle);
BUG_ON(ret);
spin_lock(&tree->lock);
refcount = zswap_entry_put(entry);
if (likely(refcount)) {
spin_unlock(&tree->lock);
return 0;
}
spin_unlock(&tree->lock);
/*
* We don't have to unlink from the rbtree because
* zswap_writeback_entry() or zswap_frontswap_invalidate page()
* has already done this for us if we are the last reference.
*/
/* free */
zswap_free_entry(tree, entry);
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;
int refcount;
/* 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 */
rb_erase(&entry->rbnode, &tree->rbroot);
/* drop the initial reference from entry creation */
refcount = zswap_entry_put(entry);
spin_unlock(&tree->lock);
if (refcount) {
/* writeback in progress, writeback will free */
return;
}
/* free */
zswap_free_entry(tree, entry);
}
/* 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) {
zbud_free(tree->pool, entry->handle);
zswap_entry_cache_free(entry);
atomic_dec(&zswap_stored_pages);
}
tree->rbroot = RB_ROOT;
spin_unlock(&tree->lock);
zbud_destroy_pool(tree->pool);
kfree(tree);
zswap_trees[type] = NULL;
}
static struct zbud_ops zswap_zbud_ops = {
.evict = zswap_writeback_entry
};
static void zswap_frontswap_init(unsigned type)
{
struct zswap_tree *tree;
tree = kzalloc(sizeof(struct zswap_tree), GFP_KERNEL);
if (!tree)
goto err;
tree->pool = zbud_create_pool(GFP_KERNEL, &zswap_zbud_ops);
if (!tree->pool)
goto freetree;
tree->rbroot = RB_ROOT;
spin_lock_init(&tree->lock);
zswap_trees[type] = tree;
return;
freetree:
kfree(tree);
err:
pr_err("alloc failed, zswap disabled for swap type %d\n", type);
}
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_pages", S_IRUGO,
zswap_debugfs_root, &zswap_pool_pages);
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)
{
if (!zswap_enabled)
return 0;
pr_info("loading zswap\n");
if (zswap_entry_cache_create()) {
pr_err("entry cache creation failed\n");
goto error;
}
if (zswap_comp_init()) {
pr_err("compressor initialization failed\n");
goto compfail;
}
if (zswap_cpu_init()) {
pr_err("per-cpu initialization failed\n");
goto pcpufail;
}
frontswap_register_ops(&zswap_frontswap_ops);
if (zswap_debugfs_init())
pr_warn("debugfs initialization failed\n");
return 0;
pcpufail:
zswap_comp_exit();
compfail:
zswap_entry_cache_destory();
error:
return -ENOMEM;
}
/* must be late so crypto has time to come up */
late_initcall(init_zswap);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Seth Jennings <sjenning@linux.vnet.ibm.com>");
MODULE_DESCRIPTION("Compressed cache for swap pages");
