cgroup: add cgroup_subsys->post_create()
Currently, there's no way for a controller to find out whether a new
cgroup finished all ->create() allocatinos successfully and is
considered "live" by cgroup.
This becomes a problem later when we add generic descendants walking
to cgroup which can be used by controllers as controllers don't have a
synchronization point where it can synchronize against new cgroups
appearing in such walks.
This patch adds ->post_create(). It's called after all ->create()
succeeded and the cgroup is linked into the generic cgroup hierarchy.
This plays the counterpart of ->pre_destroy().
When used in combination with the to-be-added generic descendant
iterators, ->post_create() can be used to implement reliable state
inheritance. It will be explained with the descendant iterators.
v2: Added a paragraph about its future use w/ descendant iterators per
Michal.
v3: Forgot to add ->post_create() invocation to cgroup_load_subsys().
Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Glauber Costa <glommer@parallels.com>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index fe876a7..b442122 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -438,6 +438,7 @@
struct cgroup_subsys {
struct cgroup_subsys_state *(*create)(struct cgroup *cgrp);
+ void (*post_create)(struct cgroup *cgrp);
void (*pre_destroy)(struct cgroup *cgrp);
void (*destroy)(struct cgroup *cgrp);
int (*can_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);