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Commit f00baae7 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarSerge E. Hallyn <serge.hallyn@ubuntu.com>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
parent 05fb22ec

include/linux/cgroup.h

+3 −0
Original line number Diff line number Diff line
@@ -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

mm/memcontrol.c

+17 −0
Original line number Diff line number Diff line
@@ -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,