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mm: remove unused zpool layer

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With zswap using zsmalloc directly, there are no more in-tree users of
this code.  Remove it.

With zpool gone, zsmalloc is now always a simple dependency and no
longer something the user needs to configure. Hide CONFIG_ZSMALLOC
from the user and have zswap and zram pull it in as needed.

Link: https://lkml.kernel.org/r/20250829162212.208258-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: SeongJae Park <sj@kernel.org>
Acked-by: Yosry Ahmed <yosry.ahmed@linux.dev> 
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.se>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Johannes Weiner
2025-08-29 17:15:27 +01:00
committed by Andrew Morton
parent 5c3f8be0c6
commit 2ccd9fecd9
11 changed files with 24 additions and 561 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
Documentation/admin-guide/mm/zswap.rst
View File

@@ -53,26 +53,17 @@ Zswap receives pages for compression from the swap subsystem and is able to
evict pages from its own compressed pool on an LRU basis and write them back to
the backing swap device in the case that the compressed pool is full.
Zswap makes use of zpool for the managing the compressed memory pool. Each
allocation in zpool is not directly accessible by address. Rather, a handle is
Zswap makes use of zsmalloc for the managing the compressed memory pool. Each
allocation in zsmalloc is not directly accessible by address. Rather, a handle is
returned by the allocation routine and that handle must be mapped before being
accessed. The compressed memory pool grows on demand and shrinks as compressed
pages are freed. The pool is not preallocated. By default, a zpool
of type selected in ``CONFIG_ZSWAP_ZPOOL_DEFAULT`` Kconfig option is created,
but it can be overridden at boot time by setting the ``zpool`` attribute,
e.g. ``zswap.zpool=zsmalloc``. It can also be changed at runtime using the sysfs
``zpool`` attribute, e.g.::
echo zsmalloc > /sys/module/zswap/parameters/zpool
The zsmalloc type zpool has a complex compressed page storage method, and it
can achieve great storage densities.
pages are freed. The pool is not preallocated.
When a swap page is passed from swapout to zswap, zswap maintains a mapping
of the swap entry, a combination of the swap type and swap offset, to the zpool
handle that references that compressed swap page. This mapping is achieved
with a red-black tree per swap type. The swap offset is the search key for the
tree nodes.
of the swap entry, a combination of the swap type and swap offset, to the
zsmalloc handle that references that compressed swap page. This mapping is
achieved with a red-black tree per swap type. The swap offset is the search
key for the tree nodes.
During a page fault on a PTE that is a swap entry, the swapin code calls the
zswap load function to decompress the page into the page allocated by the page
@@ -96,11 +87,11 @@ attribute, e.g.::
echo lzo > /sys/module/zswap/parameters/compressor
When the zpool and/or compressor parameter is changed at runtime, any existing
compressed pages are not modified; they are left in their own zpool. When a
request is made for a page in an old zpool, it is uncompressed using its
original compressor. Once all pages are removed from an old zpool, the zpool
and its compressor are freed.
When the compressor parameter is changed at runtime, any existing compressed
pages are not modified; they are left in their own pool. When a request is
made for a page in an old pool, it is uncompressed using its original
compressor. Once all pages are removed from an old pool, the pool and its
compressor are freed.
Some of the pages in zswap are same-value filled pages (i.e. contents of the
page have same value or repetitive pattern). These pages include zero-filled

1
Documentation/core-api/mm-api.rst
View File

@@ -118,7 +118,6 @@ More Memory Management Functions
.. kernel-doc:: mm/memremap.c
.. kernel-doc:: mm/hugetlb.c
.. kernel-doc:: mm/swap.c
.. kernel-doc:: mm/zpool.c
.. kernel-doc:: mm/memcontrol.c
.. #kernel-doc:: mm/memory-tiers.c (build warnings)
.. kernel-doc:: mm/shmem.c

2
Documentation/driver-api/crypto/iaa/iaa-crypto.rst
View File

@@ -476,7 +476,6 @@ Use the following commands to enable zswap::
# echo 0 > /sys/module/zswap/parameters/enabled
# echo 50 > /sys/module/zswap/parameters/max_pool_percent
# echo deflate-iaa > /sys/module/zswap/parameters/compressor
# echo zsmalloc > /sys/module/zswap/parameters/zpool
# echo 1 > /sys/module/zswap/parameters/enabled
# echo 100 > /proc/sys/vm/swappiness
# echo never > /sys/kernel/mm/transparent_hugepage/enabled
@@ -625,7 +624,6 @@ the 'fixed' compression mode::
echo 0 > /sys/module/zswap/parameters/enabled
echo 50 > /sys/module/zswap/parameters/max_pool_percent
echo deflate-iaa > /sys/module/zswap/parameters/compressor
echo zsmalloc > /sys/module/zswap/parameters/zpool
echo 1 > /sys/module/zswap/parameters/enabled
echo 100 > /proc/sys/vm/swappiness

2
MAINTAINERS
View File

@@ -27879,9 +27879,7 @@ R: Chengming Zhou <chengming.zhou@linux.dev>
L: linux-mm@kvack.org
S: Maintained
F: Documentation/admin-guide/mm/zswap.rst
F: include/linux/zpool.h
F: include/linux/zswap.h
F: mm/zpool.c
F: mm/zswap.c
F: tools/testing/selftests/cgroup/test_zswap.c

1
arch/loongarch/configs/loongson3_defconfig
View File

@@ -106,7 +106,6 @@ CONFIG_CMDLINE_PARTITION=y
CONFIG_IOSCHED_BFQ=y
CONFIG_BFQ_GROUP_IOSCHED=y
CONFIG_BINFMT_MISC=m
CONFIG_ZPOOL=y
CONFIG_ZSWAP=y
CONFIG_ZSWAP_COMPRESSOR_DEFAULT_ZSTD=y
CONFIG_ZSMALLOC=y

86
include/linux/zpool.h
View File

@@ -1,86 +0,0 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* zpool memory storage api
*
* Copyright (C) 2014 Dan Streetman
*
* This is a common frontend for the zswap compressed memory storage
* implementations.
*/
#ifndef _ZPOOL_H_
#define _ZPOOL_H_
struct zpool;
bool zpool_has_pool(char *type);
struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp);
const char *zpool_get_type(struct zpool *pool);
void zpool_destroy_pool(struct zpool *pool);
int zpool_malloc(struct zpool *pool, size_t size, gfp_t gfp,
unsigned long *handle, const int nid);
void zpool_free(struct zpool *pool, unsigned long handle);
void *zpool_obj_read_begin(struct zpool *zpool, unsigned long handle,
void *local_copy);
void zpool_obj_read_end(struct zpool *zpool, unsigned long handle,
void *handle_mem);
void zpool_obj_write(struct zpool *zpool, unsigned long handle,
void *handle_mem, size_t mem_len);
u64 zpool_get_total_pages(struct zpool *pool);
/**
* struct zpool_driver - driver implementation for zpool
* @type: name of the driver.
* @list: entry in the list of zpool drivers.
* @create: create a new pool.
* @destroy: destroy a pool.
* @malloc: allocate mem from a pool.
* @free: free mem from a pool.
* @sleep_mapped: whether zpool driver can sleep during map.
* @map: map a handle.
* @unmap: unmap a handle.
* @total_size: get total size of a pool.
*
* This is created by a zpool implementation and registered
* with zpool.
*/
struct zpool_driver {
char *type;
struct module *owner;
atomic_t refcount;
struct list_head list;
void *(*create)(const char *name, gfp_t gfp);
void (*destroy)(void *pool);
int (*malloc)(void *pool, size_t size, gfp_t gfp,
unsigned long *handle, const int nid);
void (*free)(void *pool, unsigned long handle);
void *(*obj_read_begin)(void *pool, unsigned long handle,
void *local_copy);
void (*obj_read_end)(void *pool, unsigned long handle,
void *handle_mem);
void (*obj_write)(void *pool, unsigned long handle,
void *handle_mem, size_t mem_len);
u64 (*total_pages)(void *pool);
};
void zpool_register_driver(struct zpool_driver *driver);
int zpool_unregister_driver(struct zpool_driver *driver);
bool zpool_can_sleep_mapped(struct zpool *pool);
#endif

51
mm/Kconfig
View File

@@ -9,9 +9,6 @@ menu "Memory Management options"
config ARCH_NO_SWAP
bool
config ZPOOL
bool
menuconfig SWAP
bool "Support for paging of anonymous memory (swap)"
depends on MMU && BLOCK && !ARCH_NO_SWAP
@@ -26,7 +23,7 @@ config ZSWAP
bool "Compressed cache for swap pages"
depends on SWAP
select CRYPTO
select ZPOOL
select ZSMALLOC
help
A lightweight compressed cache for swap pages. It takes
pages that are in the process of being swapped out and attempts to
@@ -125,45 +122,18 @@ config ZSWAP_COMPRESSOR_DEFAULT
default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
default ""
choice
prompt "Default allocator"
depends on ZSWAP
default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
help
Selects the default allocator for the compressed cache for
swap pages.
The default is 'zbud' for compatibility, however please do
read the description of each of the allocators below before
making a right choice.
The selection made here can be overridden by using the kernel
command line 'zswap.zpool=' option.
config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
bool "zsmalloc"
select ZSMALLOC
help
Use the zsmalloc allocator as the default allocator.
endchoice
config ZSWAP_ZPOOL_DEFAULT
string
depends on ZSWAP
default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
default ""
config ZSMALLOC
tristate
prompt "N:1 compression allocator (zsmalloc)" if (ZSWAP || ZRAM)
depends on MMU
help
zsmalloc is a slab-based memory allocator designed to store
pages of various compression levels efficiently. It achieves
the highest storage density with the least amount of fragmentation.
if ZSMALLOC
menu "Zsmalloc allocator options"
depends on ZSMALLOC
comment "Zsmalloc is a common backend allocator for zswap & zram"
config ZSMALLOC_STAT
bool "Export zsmalloc statistics"
depends on ZSMALLOC
select DEBUG_FS
help
This option enables code in the zsmalloc to collect various
@@ -175,7 +145,6 @@ config ZSMALLOC_CHAIN_SIZE
int "Maximum number of physical pages per-zspage"
default 8
range 4 16
depends on ZSMALLOC
help
This option sets the upper limit on the number of physical pages
that a zmalloc page (zspage) can consist of. The optimal zspage
@@ -190,6 +159,10 @@ config ZSMALLOC_CHAIN_SIZE
For more information, see zsmalloc documentation.
endmenu
endif
menu "Slab allocator options"
config SLUB

1
mm/Makefile
View File

@@ -115,7 +115,6 @@ obj-$(CONFIG_DEBUG_RODATA_TEST) += rodata_test.o
obj-$(CONFIG_DEBUG_VM_PGTABLE) += debug_vm_pgtable.o
obj-$(CONFIG_PAGE_OWNER) += page_owner.o
obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
obj-$(CONFIG_ZPOOL) += zpool.o
obj-$(CONFIG_ZSMALLOC) += zsmalloc.o
obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
obj-$(CONFIG_CMA) += cma.o

328
mm/zpool.c
View File

@@ -1,328 +0,0 @@
// SPDX-License-Identifier: GPL-2.0-only
/*
* zpool memory storage api
*
* Copyright (C) 2014 Dan Streetman
*
* This is a common frontend for memory storage pool implementations.
* Typically, this is used to store compressed memory.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/list.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/zpool.h>
struct zpool {
struct zpool_driver *driver;
void *pool;
};
static LIST_HEAD(drivers_head);
static DEFINE_SPINLOCK(drivers_lock);
/**
* zpool_register_driver() - register a zpool implementation.
* @driver: driver to register
*/
void zpool_register_driver(struct zpool_driver *driver)
{
spin_lock(&drivers_lock);
atomic_set(&driver->refcount, 0);
list_add(&driver->list, &drivers_head);
spin_unlock(&drivers_lock);
}
EXPORT_SYMBOL(zpool_register_driver);
/**
* zpool_unregister_driver() - unregister a zpool implementation.
* @driver: driver to unregister.
*
* Module usage counting is used to prevent using a driver
* while/after unloading, so if this is called from module
* exit function, this should never fail; if called from
* other than the module exit function, and this returns
* failure, the driver is in use and must remain available.
*/
int zpool_unregister_driver(struct zpool_driver *driver)
{
int ret = 0, refcount;
spin_lock(&drivers_lock);
refcount = atomic_read(&driver->refcount);
WARN_ON(refcount < 0);
if (refcount > 0)
ret = -EBUSY;
else
list_del(&driver->list);
spin_unlock(&drivers_lock);
return ret;
}
EXPORT_SYMBOL(zpool_unregister_driver);
/* this assumes @type is null-terminated. */
static struct zpool_driver *zpool_get_driver(const char *type)
{
struct zpool_driver *driver;
spin_lock(&drivers_lock);
list_for_each_entry(driver, &drivers_head, list) {
if (!strcmp(driver->type, type)) {
bool got = try_module_get(driver->owner);
if (got)
atomic_inc(&driver->refcount);
spin_unlock(&drivers_lock);
return got ? driver : NULL;
}
}
spin_unlock(&drivers_lock);
return NULL;
}
static void zpool_put_driver(struct zpool_driver *driver)
{
atomic_dec(&driver->refcount);
module_put(driver->owner);
}
/**
* zpool_has_pool() - Check if the pool driver is available
* @type: The type of the zpool to check (e.g. zsmalloc)
*
* This checks if the @type pool driver is available. This will try to load
* the requested module, if needed, but there is no guarantee the module will
* still be loaded and available immediately after calling. If this returns
* true, the caller should assume the pool is available, but must be prepared
* to handle the @zpool_create_pool() returning failure. However if this
* returns false, the caller should assume the requested pool type is not
* available; either the requested pool type module does not exist, or could
* not be loaded, and calling @zpool_create_pool() with the pool type will
* fail.
*
* The @type string must be null-terminated.
*
* Returns: true if @type pool is available, false if not
*/
bool zpool_has_pool(char *type)
{
struct zpool_driver *driver = zpool_get_driver(type);
if (!driver) {
request_module("zpool-%s", type);
driver = zpool_get_driver(type);
}
if (!driver)
return false;
zpool_put_driver(driver);
return true;
}
EXPORT_SYMBOL(zpool_has_pool);
/**
* zpool_create_pool() - Create a new zpool
* @type: The type of the zpool to create (e.g. zsmalloc)
* @name: The name of the zpool (e.g. zram0, zswap)
* @gfp: The GFP flags to use when allocating the pool.
*
* This creates a new zpool of the specified type. The gfp flags will be
* used when allocating memory, if the implementation supports it. If the
* ops param is NULL, then the created zpool will not be evictable.
*
* Implementations must guarantee this to be thread-safe.
*
* The @type and @name strings must be null-terminated.
*
* Returns: New zpool on success, NULL on failure.
*/
struct zpool *zpool_create_pool(const char *type, const char *name, gfp_t gfp)
{
struct zpool_driver *driver;
struct zpool *zpool;
pr_debug("creating pool type %s\n", type);
driver = zpool_get_driver(type);
if (!driver) {
request_module("zpool-%s", type);
driver = zpool_get_driver(type);
}
if (!driver) {
pr_err("no driver for type %s\n", type);
return NULL;
}
zpool = kmalloc(sizeof(*zpool), gfp);
if (!zpool) {
pr_err("couldn't create zpool - out of memory\n");
zpool_put_driver(driver);
return NULL;
}
zpool->driver = driver;
zpool->pool = driver->create(name, gfp);
if (!zpool->pool) {
pr_err("couldn't create %s pool\n", type);
zpool_put_driver(driver);
kfree(zpool);
return NULL;
}
pr_debug("created pool type %s\n", type);
return zpool;
}
/**
* zpool_destroy_pool() - Destroy a zpool
* @zpool: The zpool to destroy.
*
* Implementations must guarantee this to be thread-safe,
* however only when destroying different pools. The same
* pool should only be destroyed once, and should not be used
* after it is destroyed.
*
* This destroys an existing zpool. The zpool should not be in use.
*/
void zpool_destroy_pool(struct zpool *zpool)
{
pr_debug("destroying pool type %s\n", zpool->driver->type);
zpool->driver->destroy(zpool->pool);
zpool_put_driver(zpool->driver);
kfree(zpool);
}
/**
* zpool_get_type() - Get the type of the zpool
* @zpool: The zpool to check
*
* This returns the type of the pool.
*
* Implementations must guarantee this to be thread-safe.
*
* Returns: The type of zpool.
*/
const char *zpool_get_type(struct zpool *zpool)
{
return zpool->driver->type;
}
/**
* zpool_malloc() - Allocate memory
* @zpool: The zpool to allocate from.
* @size: The amount of memory to allocate.
* @gfp: The GFP flags to use when allocating memory.
* @handle: Pointer to the handle to set
* @nid: The preferred node id.
*
* This allocates the requested amount of memory from the pool.
* The gfp flags will be used when allocating memory, if the
* implementation supports it. The provided @handle will be
* set to the allocated object handle. The allocation will
* prefer the NUMA node specified by @nid.
*
* Implementations must guarantee this to be thread-safe.
*
* Returns: 0 on success, negative value on error.
*/
int zpool_malloc(struct zpool *zpool, size_t size, gfp_t gfp,
unsigned long *handle, const int nid)
{
return zpool->driver->malloc(zpool->pool, size, gfp, handle, nid);
}
/**
* zpool_free() - Free previously allocated memory
* @zpool: The zpool that allocated the memory.
* @handle: The handle to the memory to free.
*
* This frees previously allocated memory. This does not guarantee
* that the pool will actually free memory, only that the memory
* in the pool will become available for use by the pool.
*
* Implementations must guarantee this to be thread-safe,
* however only when freeing different handles. The same
* handle should only be freed once, and should not be used
* after freeing.
*/
void zpool_free(struct zpool *zpool, unsigned long handle)
{
zpool->driver->free(zpool->pool, handle);
}
/**
* zpool_obj_read_begin() - Start reading from a previously allocated handle.
* @zpool: The zpool that the handle was allocated from
* @handle: The handle to read from
* @local_copy: A local buffer to use if needed.
*
* This starts a read operation of a previously allocated handle. The passed
* @local_copy buffer may be used if needed by copying the memory into.
* zpool_obj_read_end() MUST be called after the read is completed to undo any
* actions taken (e.g. release locks).
*
* Returns: A pointer to the handle memory to be read, if @local_copy is used,
* the returned pointer is @local_copy.
*/
void *zpool_obj_read_begin(struct zpool *zpool, unsigned long handle,
void *local_copy)
{
return zpool->driver->obj_read_begin(zpool->pool, handle, local_copy);
}
/**
* zpool_obj_read_end() - Finish reading from a previously allocated handle.
* @zpool: The zpool that the handle was allocated from
* @handle: The handle to read from
* @handle_mem: The pointer returned by zpool_obj_read_begin()
*
* Finishes a read operation previously started by zpool_obj_read_begin().
*/
void zpool_obj_read_end(struct zpool *zpool, unsigned long handle,
void *handle_mem)
{
zpool->driver->obj_read_end(zpool->pool, handle, handle_mem);
}
/**
* zpool_obj_write() - Write to a previously allocated handle.
* @zpool: The zpool that the handle was allocated from
* @handle: The handle to read from
* @handle_mem: The memory to copy from into the handle.
* @mem_len: The length of memory to be written.
*
*/
void zpool_obj_write(struct zpool *zpool, unsigned long handle,
void *handle_mem, size_t mem_len)
{
zpool->driver->obj_write(zpool->pool, handle, handle_mem, mem_len);
}
/**
* zpool_get_total_pages() - The total size of the pool
* @zpool: The zpool to check
*
* This returns the total size in pages of the pool.
*
* Returns: Total size of the zpool in pages.
*/
u64 zpool_get_total_pages(struct zpool *zpool)
{
return zpool->driver->total_pages(zpool->pool);
}
MODULE_AUTHOR("Dan Streetman <ddstreet@ieee.org>");
MODULE_DESCRIPTION("Common API for compressed memory storage");

79
mm/zsmalloc.c
View File

@@ -36,7 +36,6 @@
#include <linux/types.h>
#include <linux/debugfs.h>
#include <linux/zsmalloc.h>
#include <linux/zpool.h>
#include <linux/fs.h>
#include <linux/workqueue.h>
#include "zpdesc.h"
@@ -433,78 +432,6 @@ static void record_obj(unsigned long handle, unsigned long obj)
*(unsigned long *)handle = obj;
}
/* zpool driver */
#ifdef CONFIG_ZPOOL
static void *zs_zpool_create(const char *name, gfp_t gfp)
{
/*
* Ignore global gfp flags: zs_malloc() may be invoked from
* different contexts and its caller must provide a valid
* gfp mask.
*/
return zs_create_pool(name);
}
static void zs_zpool_destroy(void *pool)
{
zs_destroy_pool(pool);
}
static int zs_zpool_malloc(void *pool, size_t size, gfp_t gfp,
unsigned long *handle, const int nid)
{
*handle = zs_malloc(pool, size, gfp, nid);
if (IS_ERR_VALUE(*handle))
return PTR_ERR((void *)*handle);
return 0;
}
static void zs_zpool_free(void *pool, unsigned long handle)
{
zs_free(pool, handle);
}
static void *zs_zpool_obj_read_begin(void *pool, unsigned long handle,
void *local_copy)
{
return zs_obj_read_begin(pool, handle, local_copy);
}
static void zs_zpool_obj_read_end(void *pool, unsigned long handle,
void *handle_mem)
{
zs_obj_read_end(pool, handle, handle_mem);
}
static void zs_zpool_obj_write(void *pool, unsigned long handle,
void *handle_mem, size_t mem_len)
{
zs_obj_write(pool, handle, handle_mem, mem_len);
}
static u64 zs_zpool_total_pages(void *pool)
{
return zs_get_total_pages(pool);
}
static struct zpool_driver zs_zpool_driver = {
.type = "zsmalloc",
.owner = THIS_MODULE,
.create = zs_zpool_create,
.destroy = zs_zpool_destroy,
.malloc = zs_zpool_malloc,
.free = zs_zpool_free,
.obj_read_begin = zs_zpool_obj_read_begin,
.obj_read_end = zs_zpool_obj_read_end,
.obj_write = zs_zpool_obj_write,
.total_pages = zs_zpool_total_pages,
};
MODULE_ALIAS("zpool-zsmalloc");
#endif /* CONFIG_ZPOOL */
static inline bool __maybe_unused is_first_zpdesc(struct zpdesc *zpdesc)
{
return PagePrivate(zpdesc_page(zpdesc));
@@ -2248,9 +2175,6 @@ static int __init zs_init(void)
{
int rc __maybe_unused;
#ifdef CONFIG_ZPOOL
zpool_register_driver(&zs_zpool_driver);
#endif
#ifdef CONFIG_COMPACTION
rc = set_movable_ops(&zsmalloc_mops, PGTY_zsmalloc);
if (rc)
@@ -2262,9 +2186,6 @@ static int __init zs_init(void)
static void __exit zs_exit(void)
{
#ifdef CONFIG_ZPOOL
zpool_unregister_driver(&zs_zpool_driver);
#endif
#ifdef CONFIG_COMPACTION
set_movable_ops(NULL, PGTY_zsmalloc);
#endif

1
tools/testing/selftests/zram/README
View File

@@ -14,7 +14,6 @@ Statistics for individual zram devices are exported through sysfs nodes at
Kconfig required:
CONFIG_ZRAM=y
CONFIG_CRYPTO_LZ4=y
CONFIG_ZPOOL=y
CONFIG_ZSMALLOC=y
ZRAM Testcases