I may also take the commit into our 4.4 kernel as part of some zram improvements...

https://chromium-review.googlesource.com/c/506370/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/ad0acde1a62817ada65b47f48a9a607343ff3e70

commit ad0acde1a62817ada65b47f48a9a607343ff3e70
Author: Douglas Anderson <dianders@chromium.org>
Date: Fri May 19 20:57:13 2017

metrics: Switch zram metrics to "mm_stat" if it's available

The old way for reading zram metrics was deprecated.  Now we need to
read a file with a bunch of space-separated values.

The kernel describes this file as:

  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

For a while now on kernels like 4.4 we've seen a warning in dmesg at
every bootup about using the old deprecated attribute.  On newer
upstream kernels the deprecated attribute is totally gone.

NOTE that on older kernels (like 3.14) the "mm_stat" file doesn't
exist, so we need to keep support for the old location too.

BUG= chromium:721955 
TEST=cros_run_unit_tests --board ${BOARD} --packages "metrics"
TEST=Put printouts and see that metrics got read OK
TEST=Boot up and no more warning in the kernel logs

Change-Id: I46478dc59f6c875b3b93db0e7e7524002b0f1496
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/506370
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>

[modify] https://crrev.com/ad0acde1a62817ada65b47f48a9a607343ff3e70/metrics/metrics_daemon.cc
[modify] https://crrev.com/ad0acde1a62817ada65b47f48a9a607343ff3e70/metrics/metrics_daemon.h
[modify] https://crrev.com/ad0acde1a62817ada65b47f48a9a607343ff3e70/metrics/metrics_daemon_test.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/kernel/+/796540fbee1a3a50170c93b2a7a02b095b0aa3ca

commit 796540fbee1a3a50170c93b2a7a02b095b0aa3ca
Author: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Date: Fri May 19 20:57:28 2017

UPSTREAM: zram: remove obsolete sysfs attrs

We had a deprecated_attr_warn() warning for 2 years and now the time has
come and we finally can do the cleanup.

The plan was as follows:

: 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.

The patch also removes `obsolete/sysfs-block-zram', clean ups
`testing/sysfs-block-zram' and tweaks zram.txt files.

CQ-DEPEND=CL:506370
BUG= chromium:721934 ,  chromium:721955 
TEST=Build and boot

Change-Id: I1781db0293d9cc77c66f43ea84a0185c2b1bf5a4
Link: http://lkml.kernel.org/r/20170118035838.11090-1-sergey.senozhatsky@gmail.com
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
(cherry picked from commit c87d1655c29500b459fb135258a93f8309ada9c7)
Reviewed-on: https://chromium-review.googlesource.com/505202
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>

[modify] https://crrev.com/796540fbee1a3a50170c93b2a7a02b095b0aa3ca/Documentation/ABI/testing/sysfs-block-zram
[modify] https://crrev.com/796540fbee1a3a50170c93b2a7a02b095b0aa3ca/drivers/block/zram/zram_drv.c
[delete] https://crrev.com/e0b7c547929a08ce67bfbc7c684b661489f69c14/Documentation/ABI/obsolete/sysfs-block-zram
[modify] https://crrev.com/796540fbee1a3a50170c93b2a7a02b095b0aa3ca/Documentation/blockdev/zram.txt

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/kernel/+/3410a0f3409ad1df6841c80e0ebfc45c99b16b9c

commit 3410a0f3409ad1df6841c80e0ebfc45c99b16b9c
Author: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Date: Fri May 19 20:57:10 2017

UPSTREAM: zram: remove obsolete sysfs attrs

We had a deprecated_attr_warn() warning for 2 years and now the time has
come and we finally can do the cleanup.

The plan was as follows:

: 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.

The patch also removes `obsolete/sysfs-block-zram', clean ups
`testing/sysfs-block-zram' and tweaks zram.txt files.

CQ-DEPEND=CL:506370
BUG= chromium:721934 ,  chromium:721955 
TEST=Build and boot

Change-Id: I1781db0293d9cc77c66f43ea84a0185c2b1bf5a4
Link: http://lkml.kernel.org/r/20170118035838.11090-1-sergey.senozhatsky@gmail.com
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
(cherry picked from commit c87d1655c29500b459fb135258a93f8309ada9c7)
Reviewed-on: https://chromium-review.googlesource.com/508043
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>

[modify] https://crrev.com/3410a0f3409ad1df6841c80e0ebfc45c99b16b9c/Documentation/ABI/testing/sysfs-block-zram
[modify] https://crrev.com/3410a0f3409ad1df6841c80e0ebfc45c99b16b9c/drivers/block/zram/zram_drv.c
[delete] https://crrev.com/40219cf6230182338dc3daee1af441bd3a58f249/Documentation/ABI/obsolete/sysfs-block-zram
[modify] https://crrev.com/3410a0f3409ad1df6841c80e0ebfc45c99b16b9c/Documentation/blockdev/zram.txt

Landed in M60.  To verify, we should verify that we are still getting zram metrics from older systems (3.8, 3.10, 3.14) and newer systems (3.18, 4.4) on an M-60 build that contains this fix.