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cgroup, memcg: implement css->id and convert css_from_id() to use it

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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 patch 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.

For traditional hierarchies, this shouldn't make any functional
difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jianyu Zhan <nasa4836@gmail.com>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo
2014-05-04 15:09:14 -04:00
parent ddfcadab35
commit 15a4c835e4
3 changed files with 49 additions and 23 deletions
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9
include/linux/cgroup.h
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@@ -62,6 +62,12 @@ struct cgroup_subsys_state {
/* the parent css */
struct cgroup_subsys_state *parent;
/*
* Subsys-unique ID. 0 is unused and root is always 1. The
* matching css can be looked up using css_from_id().
*/
int id;
unsigned int flags;
/* percpu_ref killing and RCU release */
@@ -655,6 +661,9 @@ struct cgroup_subsys {
/* link to parent, protected by cgroup_lock() */
struct cgroup_root *root;
/* idr for css->id */
struct idr css_idr;
/*
* List of cftypes. Each entry is the first entry of an array
* terminated by zero length name.