cgroup, memcg: implement css->id and convert css_from_id() to use it
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>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1d0b297..c3f82f6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -527,7 +527,7 @@
static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
{
- return memcg->css.cgroup->id;
+ return memcg->css.id;
}
static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
@@ -6401,7 +6401,7 @@
struct mem_cgroup *memcg = mem_cgroup_from_css(css);
struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(css));
- if (css->cgroup->id > MEM_CGROUP_ID_MAX)
+ if (css->id > MEM_CGROUP_ID_MAX)
return -ENOSPC;
if (!parent)
