[PATCH v4 3/8] cgroup: Introduce cgroup_priv_get_current

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

Getting cgroup private data for the current process' cgroup is such a
common pattern that we should add a convenience wrapper for it.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
---
 include/linux/cgroup.h |  1 +
 kernel/cgroup/cgroup.c | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 74b435f913c1..64d3dc45efd0 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -867,6 +867,7 @@ int cgroup_priv_getkey(void (*free)(struct kref *));
 void cgroup_priv_destroykey(int key);
 int cgroup_priv_install(struct cgroup *cgrp, int key, struct kref *ref);
 struct kref *cgroup_priv_get(struct cgroup *cgrp, int key);
+struct kref *cgroup_priv_get_current(int key);
 void cgroup_priv_release(struct cgroup *cgrp, int key);
 
 #endif /* _LINUX_CGROUP_H */
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index a5e2017c9a94..56ed910beb8a 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6079,6 +6079,29 @@ cgroup_priv_get(struct cgroup *cgrp, int key)
 }
 EXPORT_SYMBOL_GPL(cgroup_priv_get);
 
+/**
+ * cgroup_priv_get_current - looks up cgroup private data for current task
+ * @key: key uniquely identifying owner of private data to lookup
+ *
+ * Convenience function that performs cgroup_priv_get() on the cgroup that owns
+ * %current.
+ *
+ * Returns:
+ * A pointer to the private data's kref field, or NULL if no private data has
+ * been registered.
+ */
+struct kref *
+cgroup_priv_get_current(int key)
+{
+	struct cgroup *cgrp = task_get_dfl_cgroup(current);
+	struct kref *ref = cgroup_priv_get(cgrp, key);
+
+	cgroup_put(cgrp);
+
+	return ref;
+}
+EXPORT_SYMBOL_GPL(cgroup_priv_get_current);
+
 /**
  * cgroup_priv_free - free cgroup private data
  * @cgrp: cgroup to release private data for
-- 
2.14.3

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