From: Tejun Heo <tj@kernel.org>
Date: Wed, 19 Mar 2014 14:23:55 +0000 (-0400)
Subject: cgroup: make cgrp_dfl_root mountable
X-Git-Tag: v3.15-rc1~109^2~6
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a2dd424750807f83632a2a70293961086fd8f870;p=pandora-kernel.git

cgroup: make cgrp_dfl_root mountable

cgrp_dfl_root will be used as the default unified hierarchy.  This
patch makes cgrp_dfl_root mountable by making the following changes.

* cgroup_init_early() now initializes cgrp_dfl_root w/
  CGRP_ROOT_SANE_BEHAVIOR.  The default hierarchy is always sane.

* parse_cgroupfs_options() and cgroup_mount() are updated such that
  cgrp_dfl_root is mounted if sane_behavior is specified w/o any
  subsystems.

* rebind_subsystems() now populates the root directory of
  cgrp_dfl_root.  Note that the function still guarantees success of
  rebinding subsystems to cgrp_dfl_root.  If populating fails while
  rebinding to cgrp_dfl_root, it whines but ignores the error.

* For backward compatibility, the default hierarchy shows up in
  /proc/$PID/cgroup only after it's explicitly mounted so that
  userland which doesn't make use of it doesn't see any change.

* "current_css_set_cg_links" file of debug cgroup now treats the
  default hierarchy the same as other hierarchies.  This is visible to
  userland.  Given that it's for debug controller, this should be
  fine.

* While at it, implement cgroup_on_dfl() which tests whether a give
  cgroup is on the default hierarchy or not.

The above changes make cgrp_dfl_root mostly equivalent to other
controllers but the actual unified hierarchy behaviors are not
implemented yet.  Let's plug child cgroup creation in cgrp_dfl_root
from create_cgroup() for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
---

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