cgroup: remove cgroup->control_kn

Now that cgroup_subtree_control_write() has access to the associated
kernfs_open_file and thus the kernfs_node, there's no need to cache it
in cgroup->control_kn on creation.  Remove cgroup->control_kn and use
@of->kn directly.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

2 files changed, 3 insertions, 6 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 08eb71ee600b..aa7353deaaf3 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -177,7 +177,6 @@ struct cgroup {
 
         struct cgroup *parent;          /* my parent */
         struct kernfs_node *kn;         /* cgroup kernfs entry */
-        struct kernfs_node *control_kn; /* kn for "cgroup.subtree_control" */
         struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */
 
         /*
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 9a48c117ebf1..94d259bcd2b9 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2580,7 +2580,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
          * active_ref protection.
          */
         cgroup_get(cgrp);
-        kernfs_break_active_protection(cgrp->control_kn);
+        kernfs_break_active_protection(of->kn);
 
         mutex_lock(&cgroup_tree_mutex);
 
@@ -2697,7 +2697,7 @@ out_unlock:
 out_unlock_tree:
         mutex_unlock(&cgroup_tree_mutex);
 out_unbreak:
-        kernfs_unbreak_active_protection(cgrp->control_kn);
+        kernfs_unbreak_active_protection(of->kn);
         cgroup_put(cgrp);
         return ret ?: nbytes;
 
@@ -2887,9 +2887,7 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
                 return ret;
         }
 
-        if (cft->seq_show == cgroup_subtree_control_show)
-                cgrp->control_kn = kn;
-        else if (cft->seq_show == cgroup_populated_show)
+        if (cft->seq_show == cgroup_populated_show)
                 cgrp->populated_kn = kn;
         return 0;
 }