Add compressor device attr that allows to list and select
compression algorithms.
Define and make available for selection LZ4 compressor ops.
usage example:
List available compression algorithms (currently selected
one is LZO):
cat /sys/block/zram0/compressor
<lzo> lz4
Change compression algorithm to LZ4:
echo lz4 > /sys/block/zram0/compressor
cat /sys/block/zram0/compressor
lzo <lz4>
Update documentation with "Select compression algorithm" section
Signed-off-by: Sergey Senozhatsky <sergey.senozhat...@gmail.com>
---
Documentation/blockdev/zram.txt | 23 ++++++++++++++++-----
drivers/block/zram/Kconfig | 2 ++
drivers/block/zram/zram_drv.c | 46 +++++++++++++++++++++++++++++++++++++----
3 files changed, 62 insertions(+), 9 deletions(-)
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 393541be..af90d29 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -21,7 +21,20 @@ Following shows a typical sequence of steps for using zram.
This creates 4 devices: /dev/zram{0,1,2,3}
(num_devices parameter is optional. Default: 1)
-2) Set Disksize
+2) Select compression algorithm
+'compressor' sysfs node allows to see available, currently used
+and change compression algorithms.
+In order to list available compression algorithms (currently selected
+one is LZO):
+ cat /sys/block/zram0/compressor
+ <lzo> lz4
+
+Change compression algorithm to LZ4:
+ echo lz4 > /sys/block/zram0/compressor
+ cat /sys/block/zram0/compressor
+ lzo <lz4>
+
+3) Set Disksize
Set disk size by writing the value to sysfs node 'disksize'.
The value can be either in bytes or you can use mem suffixes.
Examples:
@@ -38,14 +51,14 @@ There is little point creating a zram of greater than twice
the size of memory
since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the
size of the disk when not in use so a huge zram is wasteful.
-3) Activate:
+4) Activate:
mkswap /dev/zram0
swapon /dev/zram0
mkfs.ext4 /dev/zram1
mount /dev/zram1 /tmp
-4) Stats:
+5) Stats:
Per-device statistics are exported as various nodes under
/sys/block/zram<id>/
disksize
@@ -59,11 +72,11 @@ size of the disk when not in use so a huge zram is wasteful.
compr_data_size
mem_used_total
-5) Deactivate:
+6) Deactivate:
swapoff /dev/zram0
umount /dev/zram1
-6) Reset:
+7) Reset:
Write any positive value to 'reset' sysfs node
echo 1 > /sys/block/zram0/reset
echo 1 > /sys/block/zram1/reset
diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index 3450be8..09dacd6 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -3,6 +3,8 @@ config ZRAM
depends on BLOCK && SYSFS && ZSMALLOC
select LZO_COMPRESS
select LZO_DECOMPRESS
+ select LZ4_COMPRESS
+ select LZ4_DECOMPRESS
default n
help
Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 4f2c748..f1434f8 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -31,6 +31,7 @@
#include <linux/string.h>
#include <linux/vmalloc.h>
#include <linux/lzo.h>
+#include <linux/lz4.h>
#include "zram_drv.h"
@@ -47,6 +48,12 @@ static struct zram_compress_ops lzo_compressor = {
.decompress = lzo1x_decompress_safe,
};
+static struct zram_compress_ops lz4_compressor = {
+ .workmem_sz = LZ4_MEM_COMPRESS,
+ .compress = lz4_compress,
+ .decompress = lz4_decompress_unknownoutputsize,
+};
+
#define ZRAM_ATTR_RO(name) \
static ssize_t zram_attr_##name##_show(struct device *d, \
struct device_attribute *attr, char *b) \
@@ -113,6 +120,34 @@ static ssize_t mem_used_total_show(struct device *dev,
return sprintf(buf, "%llu\n", val);
}
+static ssize_t compressor_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct zram *zram = dev_to_zram(dev);
+ if (zram->ops == &lzo_compressor)
+ return sprintf(buf, "<lzo> lz4\n");
+ return sprintf(buf, "lzo <lz4>\n");
+}
+
+static ssize_t compressor_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t len)
+{
+ struct zram *zram = dev_to_zram(dev);
+
+ down_write(&zram->init_lock);
+ if (init_done(zram)) {
+ up_write(&zram->init_lock);
+ pr_info("Cannot change compressor for initialized device\n");
+ return -EBUSY;
+ }
+ if (strncmp(buf, "lzo", 3) == 0)
+ zram->ops = &lzo_compressor;
+ else
+ zram->ops = &lz4_compressor;
+ up_write(&zram->init_lock);
+ return len;
+}
+
/* flag operations needs meta->tb_lock */
static int zram_test_flag(struct zram_meta *meta, u32 index,
enum zram_pageflags flag)
@@ -285,7 +320,7 @@ static void zram_free_page(struct zram *zram, size_t index)
static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
{
- int ret = LZO_E_OK;
+ int ret = 0;
size_t clen = PAGE_SIZE;
unsigned char *cmem;
struct zram_meta *meta = zram->meta;
@@ -311,7 +346,7 @@ static int zram_decompress_page(struct zram *zram, char
*mem, u32 index)
read_unlock(&meta->tb_lock);
/* Should NEVER happen. Return bio error if it does. */
- if (unlikely(ret != LZO_E_OK)) {
+ if (unlikely(ret)) {
pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
atomic64_inc(&zram->stats.failed_reads);
return ret;
@@ -354,7 +389,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec
*bvec,
ret = zram_decompress_page(zram, uncmem, index);
/* Should NEVER happen. Return bio error if it does. */
- if (unlikely(ret != LZO_E_OK))
+ if (unlikely(ret))
goto out_cleanup;
if (is_partial_io(bvec))
@@ -433,7 +468,7 @@ static int zram_bvec_write(struct zram *zram, struct
bio_vec *bvec, u32 index,
uncmem = NULL;
}
- if (unlikely(ret != LZO_E_OK)) {
+ if (unlikely(ret)) {
pr_err("Compression failed! err=%d\n", ret);
goto out;
}
@@ -705,6 +740,8 @@ static DEVICE_ATTR(initstate, S_IRUGO, initstate_show,
NULL);
static DEVICE_ATTR(reset, S_IWUSR, NULL, reset_store);
static DEVICE_ATTR(orig_data_size, S_IRUGO, orig_data_size_show, NULL);
static DEVICE_ATTR(mem_used_total, S_IRUGO, mem_used_total_show, NULL);
+static DEVICE_ATTR(compressor, S_IRUGO | S_IWUSR,
+ compressor_show, compressor_store);
ZRAM_ATTR_RO(num_reads);
ZRAM_ATTR_RO(num_writes);
@@ -719,6 +756,7 @@ static struct attribute *zram_disk_attrs[] = {
&dev_attr_disksize.attr,
&dev_attr_initstate.attr,
&dev_attr_reset.attr,
+ &dev_attr_compressor.attr,
&dev_attr_num_reads.attr,
&dev_attr_num_writes.attr,
&dev_attr_failed_reads.attr,
--
1.8.5.3.493.gb139ac2
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