[PATCH v3 2/6] cgroup: Introduce task_get_dfl_cgroup()

[Matt Roper <matthew.d.roper@intel.com>]

Wraps task_dfl_cgroup() to also take a reference to the cgroup.

Cc: Tejun Heo <tj@kernel.org>
Cc: cgroups@vger.kernel.org
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
---
 include/linux/cgroup.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index a3604b005417..b1ea2064f247 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -527,6 +527,29 @@ static inline struct cgroup *task_dfl_cgroup(struct task_struct *task)
 	return task_css_set(task)->dfl_cgrp;
 }
 
+/**
+ * task_get_dfl_cgroup() - find and get the cgroup for a task
+ * @task: the target task
+ *
+ * Find the cgroup in the v2 hierarchy that a task belongs to, increment its
+ * reference count, and return it.
+ *
+ * Returns:
+ * The appropriate cgroup from the default hierarchy.
+ */
+static inline struct cgroup *
+task_get_dfl_cgroup(struct task_struct *task)
+{
+	struct cgroup *cgrp;
+
+	mutex_lock(&cgroup_mutex);
+	cgrp = task_dfl_cgroup(task);
+	cgroup_get(cgrp);
+	mutex_unlock(&cgroup_mutex);
+
+	return cgrp;
+}
+
 static inline struct cgroup *cgroup_parent(struct cgroup *cgrp)
 {
 	struct cgroup_subsys_state *parent_css = cgrp->self.parent;
-- 
2.14.3

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