[PATCHv3 0/7] new zram statistics reporting scheme

[PATCHv3 0/7] new zram statistics reporting scheme

[Sergey Senozhatsky]

Hello,

This patch introduces rework to zram stats. We have per-stat sysfs
nodes, and it makes things a bit hard to use in user space: it doesn't
give an immediate stats 'snapshot', it requires user space to use
more syscals -- open, read, close for every stat file, with
appropriate error checks on every step, etc.

First, zram now accounts block layer statistics. available in
/sys/block/zram<id>/stat and /proc/diskstats files. So some new
stats are available (see Documentation/block/stat.txt), besides,
zram's activities are now can be monitored by sysstat's iostat
or similar tools.

Example:
cat /sys/block/zram0/stat
248     0    1984    0   251029     0  2008232   5120   0   5116   5116



Second, group currently exported on per-stat basis nodes into two
categories (files):

-- zram<id>/io_stat
accumulates device's IO stats, that are not accounted by block layer,
and contains:
        failed_reads
        failed_writes
        invalid_io
        notify_free

Example:
cat /sys/block/zram0/io_stat
0        0        0   652572


-- zram<id>/mm_stat
accumulates zram mm stats and contains:
        orig_data_size
        compr_data_size
        mem_used_total
        mem_limit
        mem_used_max
        zero_pages
        num_migrated


Example:
cat /sys/block/zram0/mm_stat
434634752 270288572 279158784        0 579895296    15060        0


per-stat sysfs nodes are now considered to be deprecated and we plan
to remove them (and clean up some of the existing stat code) in two
years (as of now, there is no warning printed to syslog about deprecated
stats being used). user space is advised to use the above mentioned 3
files.


note:
util-linux mailing list is not Cc-ed into this series. once we settle
it down, I'll write to Karel. (we have several months ahead until 4.1
will be released).

v3:
-- show pid and comm in deprecated attr show() functions (Minchan)

v2:
-- fixed a couple of typos noted by Minchan
-- documented obsolete ABI (Minchan)
-- added pr_warn_once() to deprecated sysfs attr functions (Minchan)


Sergey Senozhatsky (7):
  zram: remove `num_migrated' device attr
  zram: move compact_store() to sysfs functions area
  zram: use generic start/end io accounting
  zram: describe device attrs in documentation
  zram: export new 'io_stat' sysfs attrs
  zram: export new 'mm_stat' sysfs attrs
  zram: deprecate zram attrs sysfs nodes

 Documentation/ABI/obsolete/sysfs-block-zram | 119 ++++++++++++++++++++++++++++
 Documentation/ABI/testing/sysfs-block-zram  |  18 ++++-
 Documentation/blockdev/zram.txt             |  91 +++++++++++++++++----
 drivers/block/zram/zram_drv.c               | 116 +++++++++++++++++++++------
 4 files changed, 303 insertions(+), 41 deletions(-)
 create mode 100644 Documentation/ABI/obsolete/sysfs-block-zram

-- 
2.3.2.223.g7a9409c

[PATCHv3 1/7] zram: remove `num_migrated' device attr

[Sergey Senozhatsky]

Remove sysfs `num_migrated' attribute. We are moving away from
per-stat device attrs towards 3 stat files that will accumulate
io and mm stats in a format similar to block layer statistics in
/sys/block/<dev>/stat. That will be easier to use in user space,
and reduce the number of syscalls needed to read zram device
statistics.

`num_migrated' will return back in zram<id>/mm_stat file.

Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 Documentation/ABI/testing/sysfs-block-zram | 7 -------
 drivers/block/zram/zram_drv.c              | 2 --
 2 files changed, 9 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index bede902..91ad707 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -149,10 +149,3 @@ Description:
 		The compact file is write-only and trigger compaction for
 		allocator zrm uses. The allocator moves some objects so that
 		it could free fragment space.
-
-What:		/sys/block/zram<id>/num_migrated
-Date:		August 2015
-Contact:	Minchan Kim <minchan@kernel.org>
-Description:
-		The compact file is read-only and shows how many object
-		migrated by compaction.
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 0194799..660999f 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -392,7 +392,6 @@ ZRAM_ATTR_RO(invalid_io);
 ZRAM_ATTR_RO(notify_free);
 ZRAM_ATTR_RO(zero_pages);
 ZRAM_ATTR_RO(compr_data_size);
-ZRAM_ATTR_RO(num_migrated);
 
 static inline bool zram_meta_get(struct zram *zram)
 {
@@ -1069,7 +1068,6 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_num_writes.attr,
 	&dev_attr_failed_reads.attr,
 	&dev_attr_failed_writes.attr,
-	&dev_attr_num_migrated.attr,
 	&dev_attr_compact.attr,
 	&dev_attr_invalid_io.attr,
 	&dev_attr_notify_free.attr,
-- 
2.3.2.223.g7a9409c

[PATCHv3 2/7] zram: move compact_store() to sysfs functions area

[Sergey Senozhatsky]

A cosmetic change. We have a new code layout and keep zram per-device
sysfs store and show functions in one place. Move compact_store() to
that handlers block to conform to current layout.

Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 drivers/block/zram/zram_drv.c | 42 +++++++++++++++++++++---------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 660999f..2d5848a 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -67,27 +67,6 @@ static inline struct zram *dev_to_zram(struct device *dev)
 	return (struct zram *)dev_to_disk(dev)->private_data;
 }
 
-static ssize_t compact_store(struct device *dev,
-		struct device_attribute *attr, const char *buf, size_t len)
-{
-	unsigned long nr_migrated;
-	struct zram *zram = dev_to_zram(dev);
-	struct zram_meta *meta;
-
-	down_read(&zram->init_lock);
-	if (!init_done(zram)) {
-		up_read(&zram->init_lock);
-		return -EINVAL;
-	}
-
-	meta = zram->meta;
-	nr_migrated = zs_compact(meta->mem_pool);
-	atomic64_add(nr_migrated, &zram->stats.num_migrated);
-	up_read(&zram->init_lock);
-
-	return len;
-}
-
 /* flag operations require table entry bit_spin_lock() being held */
 static int zram_test_flag(struct zram_meta *meta, u32 index,
 			enum zram_pageflags flag)
@@ -384,6 +363,27 @@ static ssize_t comp_algorithm_store(struct device *dev,
 	return len;
 }
 
+static ssize_t compact_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	unsigned long nr_migrated;
+	struct zram *zram = dev_to_zram(dev);
+	struct zram_meta *meta;
+
+	down_read(&zram->init_lock);
+	if (!init_done(zram)) {
+		up_read(&zram->init_lock);
+		return -EINVAL;
+	}
+
+	meta = zram->meta;
+	nr_migrated = zs_compact(meta->mem_pool);
+	atomic64_add(nr_migrated, &zram->stats.num_migrated);
+	up_read(&zram->init_lock);
+
+	return len;
+}
+
 ZRAM_ATTR_RO(num_reads);
 ZRAM_ATTR_RO(num_writes);
 ZRAM_ATTR_RO(failed_reads);
-- 
2.3.2.223.g7a9409c

[PATCHv3 3/7] zram: use generic start/end io accounting

[Sergey Senozhatsky]

Use bio generic_start_io_acct() and generic_end_io_acct() to account
device's block layer statistics. This will let users to monitor zram
activities using sysstat and similar packages/tools.

Apart from the usual per-stat sysfs attr, zram IO stats are now also
available in '/sys/block/zram<id>/stat' and '/proc/diskstats' files.

We will slowly get rid of per-stat sysfs files.

Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 drivers/block/zram/zram_drv.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 2d5848a..6adccdf 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -743,8 +743,12 @@ static void zram_bio_discard(struct zram *zram, u32 index,
 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 			int offset, int rw)
 {
+	unsigned long start_time = jiffies;
 	int ret;
 
+	generic_start_io_acct(rw, bvec->bv_len >> SECTOR_SHIFT,
+			&zram->disk->part0);
+
 	if (rw == READ) {
 		atomic64_inc(&zram->stats.num_reads);
 		ret = zram_bvec_read(zram, bvec, index, offset);
@@ -753,6 +757,8 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 		ret = zram_bvec_write(zram, bvec, index, offset);
 	}
 
+	generic_end_io_acct(rw, &zram->disk->part0, start_time);
+
 	if (unlikely(ret)) {
 		if (rw == READ)
 			atomic64_inc(&zram->stats.failed_reads);
-- 
2.3.2.223.g7a9409c

[PATCHv3 4/7] zram: describe device attrs in documentation

[Sergey Senozhatsky]

Briefly describe exported device stat attrs in zram documentation.
We will eventually get rid of per-stat sysfs nodes and, thus,
clean up Documentation/ABI/testing/sysfs-block-zram file, which is
the only source of information about device sysfs nodes.

Add `num_migrated' description, since there is no independent
`num_migrated' sysfs node (and no corresponding sysfs-block-zram
entry), it will be exported via zram<id>/mm_stat file.

At this point we can provide minimal description, because
sysfs-block-zram still contains detailed information.

Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 Documentation/blockdev/zram.txt | 49 +++++++++++++++++++++++++++++------------
 1 file changed, 35 insertions(+), 14 deletions(-)

diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 902c97c..5d5e8be 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -117,20 +117,41 @@ execute
 	echo X > /sys/class/zram-control/zram_remove
 
 8) Stats:
-	Per-device statistics are exported as various nodes under
-	/sys/block/zram<id>/
-		disksize
-		num_reads
-		num_writes
-		failed_reads
-		failed_writes
-		invalid_io
-		notify_free
-		zero_pages
-		orig_data_size
-		compr_data_size
-		mem_used_total
-		mem_used_max
+Per-device statistics are exported as various nodes under /sys/block/zram<id>/
+
+A brief description of exported device attritbutes. For more details please
+read Documentation/ABI/testing/sysfs-block-zram.
+
+Name            access            description
+----            ------            -----------
+disksize          RW    show and set the device's disk size
+initstate         RO    shows the initialization state of the device
+reset             WO    trigger device reset
+num_reads         RO    the number of reads
+failed_reads      RO    the number of failed reads
+num_write         RO    the number of writes
+failed_writes     RO    the number of failed writes
+invalid_io        RO    the number of non-page-size-aligned I/O requests
+max_comp_streams  RW    the number of possible concurrent compress operations
+comp_algorithm    RW    show and change the compression algorithm
+notify_free       RO    the number of notifications to free pages (either
+                        slot free notifications or REQ_DISCARD requests)
+zero_pages        RO    the number of zero filled pages written to this disk
+orig_data_size    RO    uncompressed size of data stored in this disk
+compr_data_size   RO    compressed size of data stored in this disk
+mem_used_total    RO    the amount of memory allocated for this disk
+mem_used_max      RW    the maximum amount memory zram have consumed to
+                        store compressed data
+mem_limit         RW    the maximum amount of memory ZRAM can use to store
+                        the compressed data
+num_migrated      RO    the number of objects migrated migrated by compaction
+compact           WO    trigger memory compaction
+
+
+File /sys/block/zram<id>/stat
+
+Represents block layer statistics. Read Documentation/block/stat.txt for
+details.
 
 9) Deactivate:
 	swapoff /dev/zram0
-- 
2.3.2.223.g7a9409c

[PATCHv3 5/7] zram: export new 'io_stat' sysfs attrs

[Sergey Senozhatsky]

Per-device `zram<id>/io_stat' file provides accumulated I/O statistics
of particular zram device in a format similar to block layer statistics.
The file consists of a single line and represents the following stats
(separated by whitespace):
	failed_reads
	failed_writes
	invalid_io
	notify_free

Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 Documentation/ABI/testing/sysfs-block-zram |  9 +++++++++
 Documentation/blockdev/zram.txt            | 12 ++++++++++++
 drivers/block/zram/zram_drv.c              | 20 ++++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 91ad707..a7f622f 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -149,3 +149,12 @@ Description:
 		The compact file is write-only and trigger compaction for
 		allocator zrm uses. The allocator moves some objects so that
 		it could free fragment space.
+
+What:		/sys/block/zram<id>/io_stat
+Date:		August 2015
+Contact:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+Description:
+		The io_stat file is read-only and accumulates device's I/O
+		statistics not accounted by block layer. For example,
+		failed_reads, failed_writes, etc. File format is similar to
+		block layer statistics file format.
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 5d5e8be..5ed4dd5 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -153,6 +153,18 @@ File /sys/block/zram<id>/stat
 Represents block layer statistics. Read Documentation/block/stat.txt for
 details.
 
+
+File /sys/block/zram<id>/io_stat
+
+The stat file represents device's I/O statistics not accounted by block
+layer and, thus, not available in zram<id>/stat file. It consists of a
+single line of text and contains the following stats separated by
+whitespace:
+	failed_reads
+	failed_writes
+	invalid_io
+	notify_free
+
 9) Deactivate:
 	swapoff /dev/zram0
 	umount /dev/zram1
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 6adccdf..99d9286 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -384,6 +384,25 @@ static ssize_t compact_store(struct device *dev,
 	return len;
 }
 
+static ssize_t io_stat_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct zram *zram = dev_to_zram(dev);
+	ssize_t ret;
+
+	down_read(&zram->init_lock);
+	ret = scnprintf(buf, PAGE_SIZE,
+			"%8llu %8llu %8llu %8llu\n",
+			(u64)atomic64_read(&zram->stats.failed_reads),
+			(u64)atomic64_read(&zram->stats.failed_writes),
+			(u64)atomic64_read(&zram->stats.invalid_io),
+			(u64)atomic64_read(&zram->stats.notify_free));
+	up_read(&zram->init_lock);
+
+	return ret;
+}
+
+static DEVICE_ATTR_RO(io_stat);
 ZRAM_ATTR_RO(num_reads);
 ZRAM_ATTR_RO(num_writes);
 ZRAM_ATTR_RO(failed_reads);
@@ -1085,6 +1104,7 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_mem_used_max.attr,
 	&dev_attr_max_comp_streams.attr,
 	&dev_attr_comp_algorithm.attr,
+	&dev_attr_io_stat.attr,
 	NULL,
 };
 
-- 
2.3.2.223.g7a9409c

[PATCHv3 6/7] zram: export new 'mm_stat' sysfs attrs

[Sergey Senozhatsky]

Per-device `zram<id>/mm_stat' file provides mm statistics of a
particular zram device in a format similar to block layer statistics.
The file consists of a single line and represents the following stats
(separated by whitespace):
	orig_data_size
	compr_data_size
	mem_used_total
	mem_limit
	mem_used_max
	zero_pages
	num_migrated

Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 Documentation/ABI/testing/sysfs-block-zram |  8 ++++++++
 Documentation/blockdev/zram.txt            | 14 ++++++++++++++
 drivers/block/zram/zram_drv.c              | 31 ++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index a7f622f..2e69e83 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -158,3 +158,11 @@ Description:
 		statistics not accounted by block layer. For example,
 		failed_reads, failed_writes, etc. File format is similar to
 		block layer statistics file format.
+
+What:		/sys/block/zram<id>/mm_stat
+Date:		August 2015
+Contact:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+Description:
+		The mm_stat file is read-only and represents device's mm
+		statistics (orig_data_size, compr_data_size, etc.) in a format
+		similar to block layer statistics file format.
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 5ed4dd5..b133138 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -165,6 +165,20 @@ whitespace:
 	invalid_io
 	notify_free
 
+
+File /sys/block/zram<id>/mm_stat
+
+The stat file represents device's mm statistics. It consists of a single
+line of text and contains the following stats separated by whitespace:
+	orig_data_size
+	compr_data_size
+	mem_used_total
+	mem_limit
+	mem_used_max
+	zero_pages
+	num_migrated
+
+
 9) Deactivate:
 	swapoff /dev/zram0
 	umount /dev/zram1
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 99d9286..f2dc90d 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -402,7 +402,37 @@ static ssize_t io_stat_show(struct device *dev,
 	return ret;
 }
 
+static ssize_t mm_stat_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct zram *zram = dev_to_zram(dev);
+	u64 orig_size, mem_used = 0;
+	long max_used;
+	ssize_t ret;
+
+	down_read(&zram->init_lock);
+	if (init_done(zram))
+		mem_used = zs_get_total_pages(zram->meta->mem_pool);
+
+	orig_size = atomic64_read(&zram->stats.pages_stored);
+	max_used = atomic_long_read(&zram->stats.max_used_pages);
+
+	ret = scnprintf(buf, PAGE_SIZE,
+			"%8llu %8llu %8llu %8lu %8ld %8llu %8llu\n",
+			orig_size << PAGE_SHIFT,
+			(u64)atomic64_read(&zram->stats.compr_data_size),
+			mem_used << PAGE_SHIFT,
+			zram->limit_pages << PAGE_SHIFT,
+			max_used << PAGE_SHIFT,
+			(u64)atomic64_read(&zram->stats.zero_pages),
+			(u64)atomic64_read(&zram->stats.num_migrated));
+	up_read(&zram->init_lock);
+
+	return ret;
+}
+
 static DEVICE_ATTR_RO(io_stat);
+static DEVICE_ATTR_RO(mm_stat);
 ZRAM_ATTR_RO(num_reads);
 ZRAM_ATTR_RO(num_writes);
 ZRAM_ATTR_RO(failed_reads);
@@ -1105,6 +1135,7 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_max_comp_streams.attr,
 	&dev_attr_comp_algorithm.attr,
 	&dev_attr_io_stat.attr,
+	&dev_attr_mm_stat.attr,
 	NULL,
 };
 
-- 
2.3.2.223.g7a9409c

[PATCHv3 7/7] zram: deprecate zram attrs sysfs nodes

[Sergey Senozhatsky]

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.

Reported-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 Documentation/ABI/obsolete/sysfs-block-zram | 119 ++++++++++++++++++++++++++++
 Documentation/blockdev/zram.txt             |  16 ++++
 drivers/block/zram/zram_drv.c               |  15 ++++
 3 files changed, 150 insertions(+)
 create mode 100644 Documentation/ABI/obsolete/sysfs-block-zram

diff --git a/Documentation/ABI/obsolete/sysfs-block-zram b/Documentation/ABI/obsolete/sysfs-block-zram
new file mode 100644
index 0000000..720ea92
--- /dev/null
+++ b/Documentation/ABI/obsolete/sysfs-block-zram
@@ -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.
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index b133138..44b1a77 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -148,6 +148,22 @@ num_migrated      RO    the number of objects migrated migrated by compaction
 compact           WO    trigger memory 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
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index f2dc90d..759ee093 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -47,11 +47,22 @@ 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));			\
 }									\
@@ -206,6 +217,7 @@ 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);
 }
@@ -216,6 +228,7 @@ 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;
@@ -245,6 +258,7 @@ 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);
@@ -276,6 +290,7 @@ 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);
-- 
2.3.2.223.g7a9409c