[RFC 10/13] cgroup/drm: Client exit hook

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

We need the ability for DRM core to inform the cgroup controller when a
client has closed a DRM file descriptor. This will allow us not needing
to keep state relating to GPU time usage by tasks sets in the cgroup
controller itself.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
 drivers/gpu/drm/drm_cgroup.c |  8 ++++++++
 include/linux/cgroup_drm.h   |  4 ++++
 kernel/cgroup/drm.c          | 13 +++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/drm_cgroup.c b/drivers/gpu/drm/drm_cgroup.c
index d3050c744e3e..31a1bf3c8a43 100644
--- a/drivers/gpu/drm/drm_cgroup.c
+++ b/drivers/gpu/drm/drm_cgroup.c
@@ -5,6 +5,7 @@
 
 #include <drm/drm_drv.h>
 #include <drm/drm_clients.h>
+#include <linux/cgroup_drm.h>
 
 static DEFINE_XARRAY(drm_pid_clients);
 
@@ -31,6 +32,7 @@ void drm_clients_close(struct drm_file *file_priv)
 {
 	struct drm_device *dev = file_priv->minor->dev;
 	struct drm_pid_clients *clients;
+	struct task_struct *task;
 	struct pid *pid;
 
 	lockdep_assert_held(&dev->filelist_mutex);
@@ -43,6 +45,12 @@ void drm_clients_close(struct drm_file *file_priv)
 	if (WARN_ON_ONCE(!clients))
 		return;
 
+	task = get_pid_task(pid, PIDTYPE_PID);
+	if (task) {
+		drmcgroup_client_exited(task);
+		put_task_struct(task);
+	}
+
 	__del_clients(clients, file_priv, (unsigned long)pid);
 }
 
diff --git a/include/linux/cgroup_drm.h b/include/linux/cgroup_drm.h
index bf8abc6b8ebf..2f755b896136 100644
--- a/include/linux/cgroup_drm.h
+++ b/include/linux/cgroup_drm.h
@@ -6,4 +6,8 @@
 #ifndef _CGROUP_DRM_H
 #define _CGROUP_DRM_H
 
+struct task_struct;
+
+void drmcgroup_client_exited(struct task_struct *task);
+
 #endif	/* _CGROUP_DRM_H */
diff --git a/kernel/cgroup/drm.c b/kernel/cgroup/drm.c
index b88c93661df3..e165d8f542cc 100644
--- a/kernel/cgroup/drm.c
+++ b/kernel/cgroup/drm.c
@@ -18,11 +18,24 @@ css_to_drmcs(struct cgroup_subsys_state *css)
 	return container_of(css, struct drm_cgroup_state, css);
 }
 
+static inline struct drm_cgroup_state *get_task_drmcs(struct task_struct *task)
+{
+	return css_to_drmcs(task_get_css(task, drm_cgrp_id));
+}
+
 static void drmcs_free(struct cgroup_subsys_state *css)
 {
 	kfree(css_to_drmcs(css));
 }
 
+void drmcgroup_client_exited(struct task_struct *task)
+{
+	struct drm_cgroup_state *drmcs = get_task_drmcs(task);
+
+	css_put(&drmcs->css);
+}
+EXPORT_SYMBOL_GPL(drmcgroup_client_exited);
+
 static struct drm_cgroup_state root_drmcs = {
 };
 
-- 
2.34.1