zram: export new 'mm_stat' sysfs attrs

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

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-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>

2 files changed, 20 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index a7f622f9bcf6..2e69e83bf510 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 9610be3e9d36..7920f4026d36 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -144,6 +144,18 @@ 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
+
 8) Deactivate:
         swapoff /dev/zram0
         umount /dev/zram1