[PATCH RFC 7/9] drm: Add helper to obtain cgroup of drm_file's owning process

[Matt Roper <matthew.d.roper-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Signed-off-by: Matt Roper <matthew.d.roper-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
 include/drm/drm_file.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index 0e0c868451a5..08855a99069c 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -32,6 +32,7 @@
 
 #include <linux/types.h>
 #include <linux/completion.h>
+#include <linux/cgroup.h>
 
 #include <uapi/drm/drm.h>
 
@@ -378,4 +379,31 @@ void drm_event_cancel_free(struct drm_device *dev,
 void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e);
 void drm_send_event(struct drm_device *dev, struct drm_pending_event *e);
 
+#ifdef CONFIG_CGROUPS
+/**
+ * drm_file_get_cgroup - obtain cgroup for drm_file's owning process
+ * @file_priv: DRM file
+ * @root: cgroup hierarchy to search for process in
+ *
+ * Obtains the cgroup from a specific hierarchy that the drm_file's owning
+ * process belongs to.  The cgroup may be used to set driver-specific
+ * policy (priority, vram usage, etc.).
+ */
+static inline struct cgroup *
+drm_file_get_cgroup(struct drm_file *file_priv, struct cgroup_root *root)
+{
+	struct task_struct *task = pid_task(file_priv->pid, PIDTYPE_PID);
+	struct cgroup *cgrp;
+
+	mutex_lock(&cgroup_mutex);
+	cgrp = task_cgroup_from_root(task, root);
+	mutex_unlock(&cgroup_mutex);
+
+	return cgrp;
+}
+#else
+static inline struct cgroup *
+drm_file_get_cgroup(struct drm_file *file_priv) { return NULL; }
+#endif
+
 #endif /* _DRM_FILE_H_ */
-- 
2.14.3