cgroup: replace cftype->mode with CFTYPE_WORLD_WRITABLE
authorTejun Heo <tj@kernel.org>
Fri, 18 Sep 2015 21:54:23 +0000 (17:54 -0400)
committerTejun Heo <tj@kernel.org>
Fri, 18 Sep 2015 21:54:23 +0000 (17:54 -0400)
commit7dbdb199d3bf88f043ea17e97113eb28d5b100bc
tree648451cd5f719dafe1c01a18cf2a7903d6166f93
parent4a07c222d3afb00e1113834fee38d23a8e5d71dc
cgroup: replace cftype->mode with CFTYPE_WORLD_WRITABLE

cftype->mode allows controllers to give arbitrary permissions to
interface knobs.  Except for "cgroup.event_control", the existing uses
are spurious.

* Some explicitly specify S_IRUGO | S_IWUSR even though that's the
  default.

* "cpuset.memory_pressure" specifies S_IRUGO while also setting a
  write callback which returns -EACCES.  All it needs to do is simply
  not setting a write callback.

"cgroup.event_control" uses cftype->mode to make the file
world-writable.  It's a misdesigned interface and we don't want
controllers to be tweaking interface file permissions in general.
This patch removes cftype->mode and all its spurious uses and
implements CFTYPE_WORLD_WRITABLE for "cgroup.event_control" which is
marked as compatibility-only.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
include/linux/cgroup-defs.h
kernel/cgroup.c
kernel/cpuset.c
mm/memcontrol.c