[PATCHSET cgroup/for-3.16] cgroup: implement css->id

[Tejun Heo <tj@kernel.org>]

Hello,

Until now, cgroup->id has been used to identify all the associated
csses and css_from_id() takes cgroup ID and returns the matching css
by looking up the cgroup and then dereferencing the css associated
with it; however, now that the lifetimes of cgroup and css are
separate, this is incorrect and breaks on the unified hierarchy when a
controller is disabled and enabled back again before the previous
instance is released.

This series adds css->id which is a subsystem-unique ID and converts
css_from_id() to look up by the new css->id instead.  memcg is the
only user of css_from_id() and also converted to use css->id instead.

 0001-cgroup-make-flags-and-subsys_masks-unsigned-int.patch
 0002-cgroup-memcg-allocate-cgroup-ID-from-1.patch
 0003-cgroup-protect-cgroup_root-cgroup_idr-with-a-spinloc.patch
 0004-cgroup-use-RCU-free-in-create_css-failure-path.patch
 0005-cgroup-update-init_css-into-init_and_link_css.patch
 0006-cgroup-memcg-implement-css-id-and-convert-css_from_i.patch

0001-0003 are related prep/cleanups.

0004-0006 add css->id and convert css_from_id() and its user to it.

This patchset is on top of

  cgroup/for-3.16 f8f22e53a262 ("cgroup: implement dynamic subtree controller enable/disable on the default hierarchy")
+ [1] [PATCHSET cgroup/for-3.16] cgroup: implement cgroup.populated
+ [2] Misc comment / warning cleanups

and available in the following git branch.

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-css_id

diffstat follows.

 include/linux/cgroup.h |   21 ++++--
 kernel/cgroup.c        |  164 ++++++++++++++++++++++++++++++++-----------------
 mm/memcontrol.c        |   10 --
 3 files changed, 126 insertions(+), 69 deletions(-)

Thanks.

--
tejun

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