zram: deprecate zram attrs sysfs nodes

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>

diff --git a/Documentation/ABI/obsolete/sysfs-block-zram b/Documentation/ABI/obsolete/sysfs-block-zram
new file mode 100644 (file)
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 7920f40..48a183e 100644 (file)
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -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

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index c94a1a9..4491787 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -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);