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Subject[PATCHv9 6/7] zram: make compression algorithm selection possible
Date
Add and document `comp_algorithm' device attribute. This attribute
allows to show supported compression and currently selected
compression algorithms:
cat /sys/block/zram0/comp_algorithm
[lzo] lz4

and change selected compression algorithm:
echo lzo > /sys/block/zram0/comp_algorithm

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
Documentation/ABI/testing/sysfs-block-zram | 8 +++++++
Documentation/blockdev/zram.txt | 24 +++++++++++++++----
drivers/block/zram/zcomp.c | 32 +++++++++++++++++++++++---
drivers/block/zram/zcomp.h | 2 ++
drivers/block/zram/zram_drv.c | 37 +++++++++++++++++++++++++++---
drivers/block/zram/zram_drv.h | 1 +
6 files changed, 93 insertions(+), 11 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 0da9ed6..70ec992 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -65,6 +65,14 @@ Description:
number of backend's zcomp_strm compression streams (number of
concurrent compress operations).

+What: /sys/block/zram<id>/comp_algorithm
+Date: February 2014
+Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+Description:
+ The comp_algorithm file is read-write and lets to show
+ available and selected compression algorithms, change
+ compression algorithm selection.
+
What: /sys/block/zram<id>/notify_free
Date: August 2010
Contact: Nitin Gupta <ngupta@vflare.org>
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index aadfe60..2604ffe 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -42,7 +42,21 @@ will not take any effect, because single stream compression backend implemented
as a special case and does not support dynamic max_comp_streams. Only multi
stream backend supports dynamic max_comp_streams adjustment.

-3) Set Disksize
+3) Select compression algorithm
+ Using comp_algorithm device attribute one can see available and
+ currently selected (shown in square brackets) compression algortithms,
+ change selected compression algorithm (once the device is initialised
+ there is no way to change compression algorithm).
+
+ Examples:
+ #show supported compression algorithms
+ cat /sys/block/zram0/comp_algorithm
+ lzo [lz4]
+
+ #select lzo compression algorithm
+ echo lzo > /sys/block/zram0/comp_algorithm
+
+4) 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:
@@ -59,14 +73,14 @@ 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.

-4) Activate:
+5) Activate:
mkswap /dev/zram0
swapon /dev/zram0

mkfs.ext4 /dev/zram1
mount /dev/zram1 /tmp

-5) Stats:
+6) Stats:
Per-device statistics are exported as various nodes under
/sys/block/zram<id>/
disksize
@@ -81,11 +95,11 @@ size of the disk when not in use so a huge zram is wasteful.
compr_data_size
mem_used_total

-6) Deactivate:
+7) Deactivate:
swapoff /dev/zram0
umount /dev/zram1

-7) Reset:
+8) 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/zcomp.c b/drivers/block/zram/zcomp.c
index ac276f7..aad533a 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -39,11 +39,20 @@ struct zcomp_strm_multi {
wait_queue_head_t strm_wait;
};

+static struct zcomp_backend *backends[] = {
+ &zcomp_lzo,
+ NULL
+};
+
static struct zcomp_backend *find_backend(const char *compress)
{
- if (strncmp(compress, "lzo", 3) == 0)
- return &zcomp_lzo;
- return NULL;
+ int i = 0;
+ while (backends[i]) {
+ if (sysfs_streq(compress, backends[i]->name))
+ break;
+ i++;
+ }
+ return backends[i];
}

static void zcomp_strm_free(struct zcomp *comp, struct zcomp_strm *zstrm)
@@ -251,6 +260,23 @@ static int zcomp_strm_single_create(struct zcomp *comp)
return 0;
}

+/* show available compressors */
+ssize_t zcomp_available_show(const char *comp, char *buf)
+{
+ ssize_t sz = 0;
+ int i = 0;
+
+ while (backends[i]) {
+ if (sysfs_streq(comp, backends[i]->name))
+ sz += sprintf(buf + sz, "[%s] ", backends[i]->name);
+ else
+ sz += sprintf(buf + sz, "%s ", backends[i]->name);
+ i++;
+ }
+ sz += sprintf(buf + sz, "\n");
+ return sz;
+}
+
int zcomp_set_max_streams(struct zcomp *comp, int num_strm)
{
return comp->set_max_streams(comp, num_strm);
diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
index bd11d59..8b8997f 100644
--- a/drivers/block/zram/zcomp.h
+++ b/drivers/block/zram/zcomp.h
@@ -50,6 +50,8 @@ struct zcomp {
void (*destroy)(struct zcomp *comp);
};

+ssize_t zcomp_available_show(const char *comp, char *buf);
+
struct zcomp *zcomp_create(const char *comp, int max_strm);
void zcomp_destroy(struct zcomp *comp);

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 2de17f6..dfe52ed 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -141,6 +141,34 @@ static ssize_t max_comp_streams_store(struct device *dev,
return len;
}

+static ssize_t comp_algorithm_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ size_t sz;
+ struct zram *zram = dev_to_zram(dev);
+
+ down_read(&zram->init_lock);
+ sz = zcomp_available_show(zram->compressor, buf);
+ up_read(&zram->init_lock);
+
+ return sz;
+}
+
+static ssize_t comp_algorithm_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("Can't change algorithm for initialized device\n");
+ return -EBUSY;
+ }
+ strlcpy(zram->compressor, buf, sizeof(zram->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)
@@ -565,11 +593,11 @@ static ssize_t disksize_store(struct device *dev,
return -EBUSY;
}

- zram->comp = zcomp_create(default_compressor, zram->max_comp_streams);
+ zram->comp = zcomp_create(zram->compressor, zram->max_comp_streams);
if (!zram->comp) {
up_write(&zram->init_lock);
pr_info("Cannot initialise %s compressing backend\n",
- default_compressor);
+ zram->compressor);
return -EINVAL;
}

@@ -730,6 +758,8 @@ 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(max_comp_streams, S_IRUGO | S_IWUSR,
max_comp_streams_show, max_comp_streams_store);
+static DEVICE_ATTR(comp_algorithm, S_IRUGO | S_IWUSR,
+ comp_algorithm_show, comp_algorithm_store);

ZRAM_ATTR_RO(num_reads);
ZRAM_ATTR_RO(num_writes);
@@ -755,6 +785,7 @@ static struct attribute *zram_disk_attrs[] = {
&dev_attr_compr_data_size.attr,
&dev_attr_mem_used_total.attr,
&dev_attr_max_comp_streams.attr,
+ &dev_attr_comp_algorithm.attr,
NULL,
};

@@ -815,7 +846,7 @@ static int create_device(struct zram *zram, int device_id)
pr_warn("Error creating sysfs group");
goto out_free_disk;
}
-
+ strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
zram->meta = NULL;
zram->max_comp_streams = 1;
return 0;
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index ccf36d1..7f21c14 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -101,5 +101,6 @@ struct zram {
u64 disksize; /* bytes */
int max_comp_streams;
struct zram_stats stats;
+ char compressor[10];
};
#endif
--
1.9.0.359.g5e34a15


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