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memcg: force use_hierarchy if sane_behavior

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Turn on use_hierarchy by default if sane_behavior is specified and
don't create .use_hierarchy file.

It is debatable whether to remove .use_hierarchy file or make it ro as
the former could make transition easier in certain cases; however, the
behavior changes which will be gated by sane_behavior are intensive
including changing basic meaning of certain control knobs in a few
controllers and I don't really think keeping this piece would make
things easier in any noticeable way, so let's remove it.

v2: Explain that mem_cgroup_bind() doesn't have to worry about
    children as suggested by Michal Hocko.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
This commit is contained in:
Tejun Heo 2013-04-15 13:41:15 -07:00
parent 05fb22ec54
commit f00baae7ad
2 changed files with 20 additions and 0 deletions
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3
include/linux/cgroup.h
View File

@ -268,6 +268,9 @@ enum {
*
* - Remount is disallowed.
*
* - memcg: use_hierarchy is on by default and the cgroup file for
* the flag is not created.
*
* The followings are planned changes.
*
* - release_agent will be disallowed once replacement notification

17
mm/memcontrol.c
View File

@ -5814,6 +5814,7 @@ static struct cftype mem_cgroup_files[] = {
},
{
.name = "use_hierarchy",
.flags = CFTYPE_INSANE,
.write_u64 = mem_cgroup_hierarchy_write,
.read_u64 = mem_cgroup_hierarchy_read,
},
@ -6784,6 +6785,21 @@ static void mem_cgroup_move_task(struct cgroup *cont,
}
#endif
/*
* Cgroup retains root cgroups across [un]mount cycles making it necessary
* to verify sane_behavior flag on each mount attempt.
*/
static void mem_cgroup_bind(struct cgroup *root)
{
/*
* use_hierarchy is forced with sane_behavior. cgroup core
* guarantees that @root doesn't have any children, so turning it
* on for the root memcg is enough.
*/
if (cgroup_sane_behavior(root))
mem_cgroup_from_cont(root)->use_hierarchy = true;
}
struct cgroup_subsys mem_cgroup_subsys = {
.name = "memory",
.subsys_id = mem_cgroup_subsys_id,
@ -6794,6 +6810,7 @@ struct cgroup_subsys mem_cgroup_subsys = {
.can_attach = mem_cgroup_can_attach,
.cancel_attach = mem_cgroup_cancel_attach,
.attach = mem_cgroup_move_task,
.bind = mem_cgroup_bind,
.base_cftypes = mem_cgroup_files,
.early_init = 0,
.use_id = 1,