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SubjectRe: [PATCHv5 4/8] zswap: add to mm/
On 02/14/2013 02:38 AM, Seth Jennings wrote:
> zswap is a thin compression backend for frontswap. It receives
> pages from frontswap and attempts to store them in a compressed
> memory pool, resulting in an effective partial memory reclaim and
> dramatically reduced swap device I/O.
>
> Additionally, in most cases, pages can be retrieved from this
> compressed store much more quickly than reading from tradition
> swap devices resulting in faster performance for many workloads.
>
> This patch adds the zswap driver to mm/
>
> Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
> ---
> mm/Kconfig | 15 ++
> mm/Makefile | 1 +
> mm/zswap.c | 658 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 674 insertions(+)
> create mode 100644 mm/zswap.c
>
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 25b8f38..f9f35b7 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -470,3 +470,18 @@ config PGTABLE_MAPPING
>
> You can check speed with zsmalloc benchmark[1].
> [1] https://github.com/spartacus06/zsmalloc
> +
> +config ZSWAP
> + bool "In-kernel swap page compression"
> + depends on FRONTSWAP && CRYPTO
> + select CRYPTO_LZO
> + select ZSMALLOC
> + default n
> + help
> + Zswap is a backend for the frontswap mechanism in the VMM.
> + It receives pages from frontswap and attempts to store them
> + in a compressed memory pool, resulting in an effective
> + partial memory reclaim. In addition, pages and be retrieved
> + from this compressed store much faster than most tradition
> + swap devices resulting in reduced I/O and faster performance
> + for many workloads.
> diff --git a/mm/Makefile b/mm/Makefile
> index 0f6ef0a..1e0198f 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -32,6 +32,7 @@ obj-$(CONFIG_HAVE_MEMBLOCK) += memblock.o
> obj-$(CONFIG_BOUNCE) += bounce.o
> obj-$(CONFIG_SWAP) += page_io.o swap_state.o swapfile.o
> obj-$(CONFIG_FRONTSWAP) += frontswap.o
> +obj-$(CONFIG_ZSWAP) += zswap.o
> obj-$(CONFIG_HAS_DMA) += dmapool.o
> obj-$(CONFIG_HUGETLBFS) += hugetlb.o
> obj-$(CONFIG_NUMA) += mempolicy.o
> diff --git a/mm/zswap.c b/mm/zswap.c
> new file mode 100644
> index 0000000..e77ab2f
> --- /dev/null
> +++ b/mm/zswap.c
> @@ -0,0 +1,658 @@
> +/*
> + * 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 them and store
> + * them in a RAM-based memory pool. This results in a significant I/O
> + * reduction on the real swap device and, in the case of a slow 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/zsmalloc.h>
> +
> +/*********************************
> +* statistics
> +**********************************/
> +/* Number of memory pages used by the compressed pool */
> +static atomic_t zswap_pool_pages = ATOMIC_INIT(0);
> +/* 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,
> + * the do provide useful information on roughly how many times a

s/the/they

> + * certain event is occurring.
> +*/
> +static u64 zswap_pool_limit_hit;
> +static u64 zswap_reject_compress_poor;
> +static u64 zswap_reject_zsmalloc_fail;
> +static u64 zswap_reject_kmemcache_fail;
> +static u64 zswap_duplicate_entry;
> +
> +/*********************************
> +* tunables
> +**********************************/
> +/* Enable/disable zswap (disabled by default, fixed at boot for now) */
> +static bool zswap_enabled;
> +module_param_named(enabled, zswap_enabled, bool, 0);

please document in Documentation/kernel-parameters.txt.

> +
> +/* 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);

ditto

> +
> +/* 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);
> +
> +/*
> + * Maximum compression ratio, as as percentage, for an acceptable
> + * compressed page. Any pages that do not compress by at least
> + * this ratio will be rejected.
> +*/
> +static unsigned int zswap_max_compression_ratio = 80;
> +module_param_named(max_compression_ratio,
> + zswap_max_compression_ratio, 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 {
> + struct rb_node rbnode;
> + unsigned type;
> + pgoff_t offset;
> + unsigned long handle;
> + unsigned int length;
> +};
> +
> +struct zswap_tree {
> + struct rb_root rbroot;
> + spinlock_t lock;
> + struct zs_pool *pool;
> +};
> +
> +static struct zswap_tree *zswap_trees[MAX_SWAPFILES];
> +
> +/*********************************
> +* zswap entry functions
> +**********************************/
> +#define ZSWAP_KMEM_CACHE_NAME "zswap_entry_cache"
> +static struct kmem_cache *zswap_entry_cache;
> +
> +static inline int zswap_entry_cache_create(void)
> +{
> + zswap_entry_cache =
> + kmem_cache_create(ZSWAP_KMEM_CACHE_NAME,
> + sizeof(struct zswap_entry), 0, 0, NULL);
> + return (zswap_entry_cache == NULL);
> +}
> +
> +static inline void zswap_entry_cache_destory(void)
> +{
> + kmem_cache_destroy(zswap_entry_cache);
> +}
> +
> +static inline 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;
> + return entry;
> +}
> +
> +static inline 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, it 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 = (u8 *)__get_free_pages(GFP_KERNEL, 1);
> + 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);
> + if (dst) {
> + free_pages((unsigned long)dst, 1);
> + 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;
> +}
> +
> +/*********************************
> +* zsmalloc callbacks
> +**********************************/
> +static mempool_t *zswap_page_pool;
> +
> +static inline unsigned int zswap_max_pool_pages(void)
> +{
> + return zswap_max_pool_percent * totalram_pages / 100;
> +}
> +
> +static inline int zswap_page_pool_create(void)
> +{
> + /* TODO: dynamically size mempool */
> + zswap_page_pool = mempool_create_page_pool(256, 0);
> + if (!zswap_page_pool)
> + return -ENOMEM;
> + return 0;
> +}
> +
> +static inline void zswap_page_pool_destroy(void)
> +{
> + mempool_destroy(zswap_page_pool);
> +}
> +
> +static struct page *zswap_alloc_page(gfp_t flags)
> +{
> + struct page *page;
> +
> + if (atomic_read(&zswap_pool_pages) >= zswap_max_pool_pages()) {
> + zswap_pool_limit_hit++;
> + return NULL;
> + }
> + page = mempool_alloc(zswap_page_pool, flags);
> + if (page)
> + atomic_inc(&zswap_pool_pages);
> + return page;
> +}
> +
> +static void zswap_free_page(struct page *page)
> +{
> + if (!page)
> + return;
> + mempool_free(page, zswap_page_pool);
> + atomic_dec(&zswap_pool_pages);
> +}
> +
> +static struct zs_ops zswap_zs_ops = {
> + .alloc = zswap_alloc_page,
> + .free = zswap_free_page
> +};
> +
> +/*********************************
> +* 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;
> + unsigned long handle;
> + char *buf;
> + u8 *src, *dst;
> +
> + if (!tree) {
> + ret = -ENODEV;
> + 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 putcpu;
> + }
> + if ((dlen * 100 / PAGE_SIZE) > zswap_max_compression_ratio) {
> + zswap_reject_compress_poor++;
> + ret = -E2BIG;
> + goto putcpu;
> + }
> +
> + /* store */
> + handle = zs_malloc(tree->pool, dlen,
> + __GFP_NORETRY | __GFP_HIGHMEM | __GFP_NOMEMALLOC |
> + __GFP_NOWARN);
> + if (!handle) {
> + zswap_reject_zsmalloc_fail++;
> + ret = -ENOMEM;
> + goto putcpu;
> + }
> +
> + buf = zs_map_object(tree->pool, handle, ZS_MM_WO);
> + memcpy(buf, dst, dlen);
> + zs_unmap_object(tree->pool, handle);
> + put_cpu_var(zswap_dstmem);
> +
> + /* allocate entry */
> + entry = zswap_entry_cache_alloc(GFP_KERNEL);
> + if (!entry) {
> + zs_free(tree->pool, handle);
> + zswap_reject_kmemcache_fail++;
> + ret = -ENOMEM;
> + goto reject;
> + }
> +
> + /* populate entry */
> + entry->type = type;
> + 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);
> +
> + /* free */
> + zs_free(tree->pool, dupentry->handle);
> + zswap_entry_cache_free(dupentry);
> + atomic_dec(&zswap_stored_pages);
> + }
> + } while (ret == -EEXIST);
> + spin_unlock(&tree->lock);
> +
> + /* update stats */
> + atomic_inc(&zswap_stored_pages);
> +
> + return 0;
> +
> +putcpu:
> + put_cpu_var(zswap_dstmem);
> +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;
> +
> + /* find */
> + spin_lock(&tree->lock);
> + entry = zswap_rb_search(&tree->rbroot, offset);
> + spin_unlock(&tree->lock);
> +
> + /* decompress */
> + dlen = PAGE_SIZE;
> + src = zs_map_object(tree->pool, entry->handle, ZS_MM_RO);
> + dst = kmap_atomic(page);
> + zswap_comp_op(ZSWAP_COMPOP_DECOMPRESS, src, entry->length,
> + dst, &dlen);
> + kunmap_atomic(dst);
> + zs_unmap_object(tree->pool, entry->handle);
> +
> + return 0;
> +}
> +
> +/* invalidates a single page */
> +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);
> +
> + /* remove from rbtree */
> + rb_erase(&entry->rbnode, &tree->rbroot);
> + spin_unlock(&tree->lock);
> +
> + /* free */
> + zs_free(tree->pool, entry->handle);
> + zswap_entry_cache_free(entry);
> + atomic_dec(&zswap_stored_pages);
> +}
> +
> +/* invalidates all pages for the given swap type */
> +static void zswap_frontswap_invalidate_area(unsigned type)
> +{
> + struct zswap_tree *tree = zswap_trees[type];
> + struct rb_node *node, *next;
> + struct zswap_entry *entry;
> +
> + if (!tree)
> + return;
> +
> + /* walk the tree and free everything */
> + spin_lock(&tree->lock);
> + node = rb_first(&tree->rbroot);
> + while (node) {
> + entry = rb_entry(node, struct zswap_entry, rbnode);
> + zs_free(tree->pool, entry->handle);
> + next = rb_next(node);
> + zswap_entry_cache_free(entry);
> + node = next;
> + }
> + tree->rbroot = RB_ROOT;

Why don't need rb_erase for every nodes?

> + spin_unlock(&tree->lock);
> +}
> +
> +/* NOTE: this is called in atomic context from swapon and must not sleep */
> +static void zswap_frontswap_init(unsigned type)
> +{
> + struct zswap_tree *tree;
> +
> + tree = kzalloc(sizeof(struct zswap_tree), GFP_NOWAIT);
> + if (!tree)
> + goto err;
> + tree->pool = zs_create_pool(GFP_NOWAIT, &zswap_zs_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_zsmalloc_fail", S_IRUGO,
> + zswap_debugfs_root, &zswap_reject_zsmalloc_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("duplicate_entry", S_IRUGO,
> + zswap_debugfs_root, &zswap_duplicate_entry);
> + debugfs_create_atomic_t("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 inline int __init zswap_debugfs_init(void)
> +{
> + return 0;
> +}
> +
> +static inline 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_page_pool_create()) {
> + pr_err("page pool initialization failed\n");
> + goto pagepoolfail;
> + }
> + 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_page_pool_destroy();
> +pagepoolfail:
> + 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");



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