[PATCHv2 3/3] zram: use common zpool interface

From: Vitaly Wool
Date: Thu Dec 19 2019 - 09:28:00 EST

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This patch modifies ZRAM use a common "small allocator" API
(zpool). This is done to address increasing demand to deploy
ZRAM in systems where zsmalloc (which is currently the only
available ZRAM allocator backend) is not a perfect match or is
not applicable at all. An example of a system of the first type
is an embedded system using ZRAM block device as a swap where
quick application launch is critical for good user experience
since z3fold is substantially faster on read than zsmalloc [1].
A system of the second type is, for instance, the one with
hardware on-the-fly RAM compression/decompression where the
saved RAM space could be used for ZRAM but would require a
special allocator. These cases wre also discussed in detail
at LPC'2019 [2].

zpool-registered backend can be selected using ZRAM sysfs
interface on a per-device basis. 'zsmalloc' is taken by default.

This patch is transparent with regard to the existing ZRAM
functionality and does not change its default behavior.

[1] https://lkml.org/lkml/2019/10/21/743
[2] https://linuxplumbersconf.org/event/4/contributions/551/

Signed-off-by: Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>
---
drivers/block/zram/Kconfig | 3 +-
drivers/block/zram/zram_drv.c | 100 ++++++++++++++++++++++++----------
drivers/block/zram/zram_drv.h | 6 +-
3 files changed, 76 insertions(+), 33 deletions(-)

diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index fe7a4b7d30cf..7248d5aa3468 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -1,8 +1,9 @@
# SPDX-License-Identifier: GPL-2.0
config ZRAM
tristate "Compressed RAM block device support"
- depends on BLOCK && SYSFS && ZSMALLOC && CRYPTO
+ depends on BLOCK && SYSFS && CRYPTO
select CRYPTO_LZO
+ select ZPOOL
help
Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
Pages written to these disks are compressed and stored in memory
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 4285e75e52c3..189c326cbeee 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -43,6 +43,8 @@ static DEFINE_MUTEX(zram_index_mutex);
static int zram_major;
static const char *default_compressor = "lzo-rle";

+static const char *default_allocator = "zsmalloc";
+
/* Module params (documentation at end) */
static unsigned int num_devices = 1;
/*
@@ -245,6 +247,14 @@ static ssize_t disksize_show(struct device *dev,
return scnprintf(buf, PAGE_SIZE, "%llu\n", zram->disksize);
}

+static ssize_t allocator_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct zram *zram = dev_to_zram(dev);
+
+ return scnprintf(buf, PAGE_SIZE, "%s\n", zram->allocator);
+}
+
static ssize_t mem_limit_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t len)
{
@@ -277,7 +287,7 @@ static ssize_t mem_used_max_store(struct device *dev,
down_read(&zram->init_lock);
if (init_done(zram)) {
atomic_long_set(&zram->stats.max_used_pages,
- zs_get_total_pages(zram->mem_pool));
+ zpool_get_total_size(zram->mem_pool) >> PAGE_SHIFT);
}
up_read(&zram->init_lock);

@@ -1021,7 +1031,7 @@ static ssize_t compact_store(struct device *dev,
return -EINVAL;
}

- zs_compact(zram->mem_pool);
+ zpool_compact(zram->mem_pool);
up_read(&zram->init_lock);

return len;
@@ -1049,17 +1059,14 @@ static ssize_t mm_stat_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct zram *zram = dev_to_zram(dev);
- struct zs_pool_stats pool_stats;
u64 orig_size, mem_used = 0;
- long max_used;
+ long max_used, num_compacted = 0;
ssize_t ret;

- memset(&pool_stats, 0x00, sizeof(struct zs_pool_stats));
-
down_read(&zram->init_lock);
if (init_done(zram)) {
- mem_used = zs_get_total_pages(zram->mem_pool);
- zs_pool_stats(zram->mem_pool, &pool_stats);
+ mem_used = zpool_get_total_size(zram->mem_pool);
+ num_compacted = zpool_get_num_compacted(zram->mem_pool);
}

orig_size = atomic64_read(&zram->stats.pages_stored);
@@ -1069,11 +1076,11 @@ static ssize_t mm_stat_show(struct device *dev,
"%8llu %8llu %8llu %8lu %8ld %8llu %8lu %8llu\n",
orig_size << PAGE_SHIFT,
(u64)atomic64_read(&zram->stats.compr_data_size),
- mem_used << PAGE_SHIFT,
+ mem_used,
zram->limit_pages << PAGE_SHIFT,
max_used << PAGE_SHIFT,
(u64)atomic64_read(&zram->stats.same_pages),
- pool_stats.pages_compacted,
+ num_compacted,
(u64)atomic64_read(&zram->stats.huge_pages));
up_read(&zram->init_lock);

@@ -1134,7 +1141,7 @@ static void zram_meta_free(struct zram *zram, u64 disksize)
for (index = 0; index < num_pages; index++)
zram_free_page(zram, index);

- zs_destroy_pool(zram->mem_pool);
+ zpool_destroy_pool(zram->mem_pool);
vfree(zram->table);
}

@@ -1147,14 +1154,18 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
if (!zram->table)
return false;

- zram->mem_pool = zs_create_pool(zram->disk->disk_name);
+ zram->mem_pool = zpool_create_pool(zram->allocator,
+ zram->disk->disk_name,
+ GFP_NOIO, NULL);
if (!zram->mem_pool) {
+ pr_err("%s: not enough memory or wrong allocator '%s'\n",
+ __func__, zram->allocator);
vfree(zram->table);
return false;
}

if (!huge_class_size)
- huge_class_size = zs_huge_class_size(zram->mem_pool);
+ huge_class_size = zpool_huge_class_size(zram->mem_pool);
return true;
}

@@ -1198,7 +1209,7 @@ static void zram_free_page(struct zram *zram, size_t index)
if (!handle)
return;

- zs_free(zram->mem_pool, handle);
+ zpool_free(zram->mem_pool, handle);

atomic64_sub(zram_get_obj_size(zram, index),
&zram->stats.compr_data_size);
@@ -1247,7 +1258,7 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,

size = zram_get_obj_size(zram, index);

- src = zs_map_object(zram->mem_pool, handle, ZS_MM_RO);
+ src = zpool_map_handle(zram->mem_pool, handle, ZPOOL_MM_RO);
if (size == PAGE_SIZE) {
dst = kmap_atomic(page);
memcpy(dst, src, PAGE_SIZE);
@@ -1261,7 +1272,7 @@ static int __zram_bvec_read(struct zram *zram, struct page *page, u32 index,
kunmap_atomic(dst);
zcomp_stream_put(zram->comp);
}
- zs_unmap_object(zram->mem_pool, handle);
+ zpool_unmap_handle(zram->mem_pool, handle);
zram_slot_unlock(zram, index);

/* Should NEVER happen. Return bio error if it does. */
@@ -1336,7 +1347,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
if (unlikely(ret)) {
zcomp_stream_put(zram->comp);
pr_err("Compression failed! err=%d\n", ret);
- zs_free(zram->mem_pool, handle);
+ zpool_free(zram->mem_pool, handle);
return ret;
}

@@ -1355,33 +1366,34 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
* if we have a 'non-null' handle here then we are coming
* from the slow path and handle has already been allocated.
*/
- if (!handle)
- handle = zs_malloc(zram->mem_pool, comp_len,
+ if (handle == 0)
+ ret = zpool_malloc(zram->mem_pool, comp_len,
__GFP_KSWAPD_RECLAIM |
__GFP_NOWARN |
__GFP_HIGHMEM |
- __GFP_MOVABLE);
- if (!handle) {
+ __GFP_MOVABLE,
+ &handle);
+ if (ret) {
zcomp_stream_put(zram->comp);
atomic64_inc(&zram->stats.writestall);
- handle = zs_malloc(zram->mem_pool, comp_len,
- GFP_NOIO | __GFP_HIGHMEM |
- __GFP_MOVABLE);
- if (handle)
+ ret = zpool_malloc(zram->mem_pool, comp_len,
+ GFP_NOIO | __GFP_HIGHMEM | __GFP_MOVABLE,
+ &handle);
+ if (ret == 0)
goto compress_again;
return -ENOMEM;
}

- alloced_pages = zs_get_total_pages(zram->mem_pool);
+ alloced_pages = zpool_get_total_size(zram->mem_pool) >> PAGE_SHIFT;
update_used_max(zram, alloced_pages);

if (zram->limit_pages && alloced_pages > zram->limit_pages) {
zcomp_stream_put(zram->comp);
- zs_free(zram->mem_pool, handle);
+ zpool_free(zram->mem_pool, handle);
return -ENOMEM;
}

- dst = zs_map_object(zram->mem_pool, handle, ZS_MM_WO);
+ dst = zpool_map_handle(zram->mem_pool, handle, ZPOOL_MM_WO);

src = zstrm->buffer;
if (comp_len == PAGE_SIZE)
@@ -1391,7 +1403,7 @@ static int __zram_bvec_write(struct zram *zram, struct bio_vec *bvec,
kunmap_atomic(src);

zcomp_stream_put(zram->comp);
- zs_unmap_object(zram->mem_pool, handle);
+ zpool_unmap_handle(zram->mem_pool, handle);
atomic64_add(comp_len, &zram->stats.compr_data_size);
out:
/*
@@ -1752,6 +1764,32 @@ static ssize_t disksize_store(struct device *dev,
return err;
}

+static ssize_t allocator_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t len)
+{
+ struct zram *zram = dev_to_zram(dev);
+ int ret;
+
+ down_write(&zram->init_lock);
+ if (init_done(zram)) {
+ pr_info("Cannot change disksize for initialized device\n");
+ ret = -EBUSY;
+ goto out;
+ }
+
+ if (len > sizeof(zram->allocator)) {
+ pr_info("Allocator backend name too long\n");
+ ret = -EINVAL;
+ goto out;
+ }
+ strlcpy(zram->allocator, buf, len);
+ ret = len;
+
+out:
+ up_write(&zram->init_lock);
+ return ret;
+}
+
static ssize_t reset_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t len)
{
@@ -1834,6 +1872,7 @@ static DEVICE_ATTR_WO(writeback);
static DEVICE_ATTR_RW(writeback_limit);
static DEVICE_ATTR_RW(writeback_limit_enable);
#endif
+static DEVICE_ATTR_RW(allocator);

static struct attribute *zram_disk_attrs[] = {
&dev_attr_disksize.attr,
@@ -1857,6 +1896,7 @@ static struct attribute *zram_disk_attrs[] = {
&dev_attr_bd_stat.attr,
#endif
&dev_attr_debug_stat.attr,
+ &dev_attr_allocator.attr,
NULL,
};

@@ -1954,7 +1994,7 @@ static int zram_add(void)
device_add_disk(NULL, zram->disk, zram_disk_attr_groups);

strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
-
+ strlcpy(zram->allocator, default_allocator, sizeof(zram->allocator));
zram_debugfs_register(zram);
pr_info("Added device: %s\n", zram->disk->disk_name);
return device_id;
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index f2fd46daa760..8a649a553a7a 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -16,7 +16,7 @@
#define _ZRAM_DRV_H_

#include <linux/rwsem.h>
-#include <linux/zsmalloc.h>
+#include <linux/zpool.h>
#include <linux/crypto.h>

#include "zcomp.h"
@@ -28,6 +28,7 @@
#define ZRAM_SECTOR_PER_LOGICAL_BLOCK \
(1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))

+#define ZRAM_MAX_ALLOCATOR_NAME 64

/*
* The lower ZRAM_FLAG_SHIFT bits of table.flags is for
@@ -91,7 +92,7 @@ struct zram_stats {

struct zram {
struct zram_table_entry *table;
- struct zs_pool *mem_pool;
+ struct zpool *mem_pool;
struct zcomp *comp;
struct gendisk *disk;
/* Prevent concurrent execution of device init */
@@ -108,6 +109,7 @@ struct zram {
*/
u64 disksize; /* bytes */
char compressor[CRYPTO_MAX_ALG_NAME];
+ char allocator[ZRAM_MAX_ALLOCATOR_NAME];
/*
* zram is claimed so open request will be failed
*/
--
2.20.1

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