From f00baae7ad6c5f1503528efa852f0be8e9513f0e Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 15 Apr 2013 13:41:15 -0700 Subject: [PATCH] memcg: force use_hierarchy if sane_behavior 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 Acked-by: Serge E. Hallyn Acked-by: Li Zefan Acked-by: Michal Hocko Acked-by: KAMEZAWA Hiroyuki --- include/linux/cgroup.h | 3 +++ mm/memcontrol.c | 17 +++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 64047ae7fde1..cda7eb2239e1 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -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 diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9715c0c491b0..df87bdd4d692 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -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,