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 <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>
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@ -268,6 +268,9 @@ enum {
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*
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*
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* - Remount is disallowed.
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* - Remount is disallowed.
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*
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*
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* - memcg: use_hierarchy is on by default and the cgroup file for
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* the flag is not created.
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*
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* The followings are planned changes.
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* The followings are planned changes.
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*
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*
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* - release_agent will be disallowed once replacement notification
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* - release_agent will be disallowed once replacement notification
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@ -5814,6 +5814,7 @@ static struct cftype mem_cgroup_files[] = {
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},
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},
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{
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{
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.name = "use_hierarchy",
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.name = "use_hierarchy",
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.flags = CFTYPE_INSANE,
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.write_u64 = mem_cgroup_hierarchy_write,
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.write_u64 = mem_cgroup_hierarchy_write,
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.read_u64 = mem_cgroup_hierarchy_read,
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.read_u64 = mem_cgroup_hierarchy_read,
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},
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},
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@ -6784,6 +6785,21 @@ static void mem_cgroup_move_task(struct cgroup *cont,
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}
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}
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#endif
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#endif
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/*
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* Cgroup retains root cgroups across [un]mount cycles making it necessary
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* to verify sane_behavior flag on each mount attempt.
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*/
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static void mem_cgroup_bind(struct cgroup *root)
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{
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/*
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* use_hierarchy is forced with sane_behavior. cgroup core
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* guarantees that @root doesn't have any children, so turning it
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* on for the root memcg is enough.
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*/
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if (cgroup_sane_behavior(root))
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mem_cgroup_from_cont(root)->use_hierarchy = true;
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}
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struct cgroup_subsys mem_cgroup_subsys = {
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struct cgroup_subsys mem_cgroup_subsys = {
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.name = "memory",
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.name = "memory",
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.subsys_id = mem_cgroup_subsys_id,
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.subsys_id = mem_cgroup_subsys_id,
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@ -6794,6 +6810,7 @@ struct cgroup_subsys mem_cgroup_subsys = {
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.can_attach = mem_cgroup_can_attach,
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.can_attach = mem_cgroup_can_attach,
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.cancel_attach = mem_cgroup_cancel_attach,
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.cancel_attach = mem_cgroup_cancel_attach,
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.attach = mem_cgroup_move_task,
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.attach = mem_cgroup_move_task,
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.bind = mem_cgroup_bind,
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.base_cftypes = mem_cgroup_files,
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.base_cftypes = mem_cgroup_files,
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.early_init = 0,
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.early_init = 0,
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.use_id = 1,
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.use_id = 1,
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