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zram: deprecate zram attrs sysfs nodes

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Add Documentation/ABI/obsolete/sysfs-block-zram file and list obsolete and
deprecated attributes there.  The patch also adds additional information
to zram documentation and describes the basic strategy:

- the existing RW nodes will be downgraded to WO nodes (in 4.11)
- deprecated RO sysfs nodes will eventually be removed (in 4.11)

Users will be additionally notified about deprecated attr usage by
pr_warn_once() (added to every deprecated attr _show()), as suggested by
Minchan Kim.

User space is advised to use zram<id>/stat, zram<id>/io_stat and
zram<id>/mm_stat files.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sergey Senozhatsky 2015-04-15 16:16:09 -07:00 committed by Linus Torvalds
parent 4f2109f608
commit 8f7d282c71
3 changed files with 150 additions and 0 deletions
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119
Documentation/ABI/obsolete/sysfs-block-zram Normal file
View file

@ -0,0 +1,119 @@
What: /sys/block/zram<id>/num_reads
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The num_reads file is read-only and specifies the number of
reads (failed or successful) done on this device.
Now accessible via zram<id>/stat node.
What: /sys/block/zram<id>/num_writes
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The num_writes file is read-only and specifies the number of
writes (failed or successful) done on this device.
Now accessible via zram<id>/stat node.
What: /sys/block/zram<id>/invalid_io
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The invalid_io file is read-only and specifies the number of
non-page-size-aligned I/O requests issued to this device.
Now accessible via zram<id>/io_stat node.
What: /sys/block/zram<id>/failed_reads
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The failed_reads file is read-only and specifies the number of
failed reads happened on this device.
Now accessible via zram<id>/io_stat node.
What: /sys/block/zram<id>/failed_writes
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The failed_writes file is read-only and specifies the number of
failed writes happened on this device.
Now accessible via zram<id>/io_stat node.
What: /sys/block/zram<id>/notify_free
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The notify_free file is read-only. Depending on device usage
scenario it may account a) the number of pages freed because
of swap slot free notifications or b) the number of pages freed
because of REQ_DISCARD requests sent by bio. The former ones
are sent to a swap block device when a swap slot is freed, which
implies that this disk is being used as a swap disk. The latter
ones are sent by filesystem mounted with discard option,
whenever some data blocks are getting discarded.
Now accessible via zram<id>/io_stat node.
What: /sys/block/zram<id>/zero_pages
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The zero_pages file is read-only and specifies number of zero
filled pages written to this disk. No memory is allocated for
such pages.
Now accessible via zram<id>/mm_stat node.
What: /sys/block/zram<id>/orig_data_size
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The orig_data_size file is read-only and specifies uncompressed
size of data stored in this disk. This excludes zero-filled
pages (zero_pages) since no memory is allocated for them.
Unit: bytes
Now accessible via zram<id>/mm_stat node.
What: /sys/block/zram<id>/compr_data_size
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The compr_data_size file is read-only and specifies compressed
size of data stored in this disk. So, compression ratio can be
calculated using orig_data_size and this statistic.
Unit: bytes
Now accessible via zram<id>/mm_stat node.
What: /sys/block/zram<id>/mem_used_total
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The mem_used_total file is read-only and specifies the amount
of memory, including allocator fragmentation and metadata
overhead, allocated for this disk. So, allocator space
efficiency can be calculated using compr_data_size and this
statistic.
Unit: bytes
Now accessible via zram<id>/mm_stat node.
What: /sys/block/zram<id>/mem_used_max
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The mem_used_max file is read/write and specifies the amount
of maximum memory zram have consumed to store compressed data.
For resetting the value, you should write "0". Otherwise,
you could see -EINVAL.
Unit: bytes
Downgraded to write-only node: so it's possible to set new
value only; its current value is stored in zram<id>/mm_stat
node.
What: /sys/block/zram<id>/mem_limit
Date: August 2015
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The mem_limit file is read/write and specifies the maximum
amount of memory ZRAM can use to store the compressed data.
The limit could be changed in run time and "0" means disable
the limit. No limit is the initial state. Unit: bytes
Downgraded to write-only node: so it's possible to set new
value only; its current value is stored in zram<id>/mm_stat
node.

16
Documentation/blockdev/zram.txt
View file

@ -128,6 +128,22 @@ mem_limit RW the maximum amount of memory ZRAM can use to store
num_migrated RO the number of objects migrated migrated by compaction
WARNING
=======
per-stat sysfs attributes are considered to be deprecated.
The basic strategy is:
-- the existing RW nodes will be downgraded to WO nodes (in linux 4.11)
-- deprecated RO sysfs nodes will eventually be removed (in linux 4.11)
The list of deprecated attributes can be found here:
Documentation/ABI/obsolete/sysfs-block-zram
Basically, every attribute that has its own read accessible sysfs node
(e.g. num_reads) *AND* is accessible via one of the stat files (zram<id>/stat
or zram<id>/io_stat or zram<id>/mm_stat) is considered to be deprecated.
User space is advised to use the following files to read the device statistics.
File /sys/block/zram<id>/stat
Represents block layer statistics. Read Documentation/block/stat.txt for

15
drivers/block/zram/zram_drv.c
View file

@ -43,11 +43,22 @@ static const char *default_compressor = "lzo";
/* Module params (documentation at end) */
static unsigned int num_devices = 1;
static inline void deprecated_attr_warn(const char *name)
{
pr_warn_once("%d (%s) Attribute %s (and others) will be removed. %s\n",
task_pid_nr(current),
current->comm,
name,
"See zram documentation.");
}
#define ZRAM_ATTR_RO(name) \
static ssize_t name##_show(struct device *d, \
struct device_attribute *attr, char *b) \
{ \
struct zram *zram = dev_to_zram(d); \
\
deprecated_attr_warn(__stringify(name)); \
return scnprintf(b, PAGE_SIZE, "%llu\n", \
(u64)atomic64_read(&zram->stats.name)); \
} \
@ -89,6 +100,7 @@ static ssize_t orig_data_size_show(struct device *dev,
{
struct zram *zram = dev_to_zram(dev);
deprecated_attr_warn("orig_data_size");
return scnprintf(buf, PAGE_SIZE, "%llu\n",
(u64)(atomic64_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
}
@ -99,6 +111,7 @@ static ssize_t mem_used_total_show(struct device *dev,
u64 val = 0;
struct zram *zram = dev_to_zram(dev);
deprecated_attr_warn("mem_used_total");
down_read(&zram->init_lock);
if (init_done(zram)) {
struct zram_meta *meta = zram->meta;
@ -128,6 +141,7 @@ static ssize_t mem_limit_show(struct device *dev,
u64 val;
struct zram *zram = dev_to_zram(dev);
deprecated_attr_warn("mem_limit");
down_read(&zram->init_lock);
val = zram->limit_pages;
up_read(&zram->init_lock);
@ -159,6 +173,7 @@ static ssize_t mem_used_max_show(struct device *dev,
u64 val = 0;
struct zram *zram = dev_to_zram(dev);
deprecated_attr_warn("mem_used_max");
down_read(&zram->init_lock);
if (init_done(zram))
val = atomic_long_read(&zram->stats.max_used_pages);