cgroup: misc changes

Misc trivial changes to prepare for future changes.  No functional
difference.

* Expose cgroup_get(), cgroup_tryget() and cgroup_parent().

* Implement task_dfl_cgroup() which dereferences css_set->dfl_cgrp.

* Rename cgroup_stats_show() to cgroup_stat_show() for consistency
  with the file name.

Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 79faa6467f76..085056e562b1 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -398,6 +398,16 @@ static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
 		percpu_ref_put_many(&css->refcnt, n);
 }
 
+static inline void cgroup_get(struct cgroup *cgrp)
+{
+	css_get(&cgrp->self);
+}
+
+static inline bool cgroup_tryget(struct cgroup *cgrp)
+{
+	return css_tryget(&cgrp->self);
+}
+
 static inline void cgroup_put(struct cgroup *cgrp)
 {
 	css_put(&cgrp->self);
@@ -510,6 +520,20 @@ static inline struct cgroup *task_cgroup(struct task_struct *task,
 	return task_css(task, subsys_id)->cgroup;
 }
 
+static inline struct cgroup *task_dfl_cgroup(struct task_struct *task)
+{
+	return task_css_set(task)->dfl_cgrp;
+}
+
+static inline struct cgroup *cgroup_parent(struct cgroup *cgrp)
+{
+	struct cgroup_subsys_state *parent_css = cgrp->self.parent;
+
+	if (parent_css)
+		return container_of(parent_css, struct cgroup, self);
+	return NULL;
+}
+
 /**
  * cgroup_is_descendant - test ancestry
  * @cgrp: the cgroup to be tested