[RFC 18/23] cgroup/drm: Track DRM clients per cgroup

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

To enable propagation of settings from the cgroup DRM controller to DRM
and vice-versa, we need to start tracking to which cgroups DRM clients
belong.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
---
 drivers/gpu/drm/drm_file.c |  8 +++++
 include/drm/drm_file.h     |  6 ++++
 include/linux/cgroup_drm.h | 20 ++++++++++++
 kernel/cgroup/drm.c        | 62 +++++++++++++++++++++++++++++++++++++-
 4 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index cf2463090d3a..7500b2b14fd5 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -32,6 +32,7 @@
  */
 
 #include <linux/anon_inodes.h>
+#include <linux/cgroup_drm.h>
 #include <linux/dma-fence.h>
 #include <linux/file.h>
 #include <linux/module.h>
@@ -275,6 +276,8 @@ static void drm_close_helper(struct file *filp)
 	list_del(&file_priv->lhead);
 	mutex_unlock(&dev->filelist_mutex);
 
+	drmcgroup_client_close(file_priv);
+
 	drm_file_free(file_priv);
 }
 
@@ -339,6 +342,8 @@ int drm_open_helper(struct file *filp, struct drm_minor *minor)
 	list_add(&priv->lhead, &dev->filelist);
 	mutex_unlock(&dev->filelist_mutex);
 
+	drmcgroup_client_open(priv);
+
 	return 0;
 }
 
@@ -465,6 +470,9 @@ void drm_file_update_pid(struct drm_file *filp)
 	old = rcu_replace_pointer(filp->pid, pid, 1);
 	mutex_unlock(&dev->filelist_mutex);
 
+	if (pid != old)
+		drmcgroup_client_migrate(filp);
+
 	synchronize_rcu();
 	put_pid(old);
 }
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index 94d365b22505..76b194c0fc52 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -30,6 +30,7 @@
 #ifndef _DRM_FILE_H_
 #define _DRM_FILE_H_
 
+#include <linux/cgroup.h>
 #include <linux/types.h>
 #include <linux/completion.h>
 #include <linux/idr.h>
@@ -295,6 +296,11 @@ struct drm_file {
 	/** @minor: &struct drm_minor for this file. */
 	struct drm_minor *minor;
 
+#if IS_ENABLED(CONFIG_CGROUP_DRM)
+	struct cgroup_subsys_state *__css;
+	struct list_head clink;
+#endif
+
 	/**
 	 * @object_idr:
 	 *
diff --git a/include/linux/cgroup_drm.h b/include/linux/cgroup_drm.h
index 3e51fe517791..d6a9a2fbdbf5 100644
--- a/include/linux/cgroup_drm.h
+++ b/include/linux/cgroup_drm.h
@@ -4,4 +4,24 @@
 #ifndef _CGROUP_DRM_H
 #define _CGROUP_DRM_H
 
+#include <drm/drm_file.h>
+
+#if IS_ENABLED(CONFIG_CGROUP_DRM)
+void drmcgroup_client_open(struct drm_file *file_priv);
+void drmcgroup_client_close(struct drm_file *file_priv);
+void drmcgroup_client_migrate(struct drm_file *file_priv);
+#else
+static inline void drmcgroup_client_open(struct drm_file *file_priv)
+{
+}
+
+static inline void drmcgroup_client_close(struct drm_file *file_priv)
+{
+}
+
+static void drmcgroup_client_migrate(struct drm_file *file_priv)
+{
+}
+#endif
+
 #endif	/* _CGROUP_DRM_H */
diff --git a/kernel/cgroup/drm.c b/kernel/cgroup/drm.c
index 55947a009e04..e9dc1e7cc4a4 100644
--- a/kernel/cgroup/drm.c
+++ b/kernel/cgroup/drm.c
@@ -3,17 +3,25 @@
 
 #include <linux/cgroup.h>
 #include <linux/cgroup_drm.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
 #include <linux/slab.h>
 
 struct drm_cgroup_state {
 	struct cgroup_subsys_state css;
+
+	struct list_head clients;
 };
 
 struct drm_root_cgroup_state {
 	struct drm_cgroup_state drmcs;
 };
 
-static struct drm_root_cgroup_state root_drmcs;
+static struct drm_root_cgroup_state root_drmcs = {
+	.drmcs.clients = LIST_HEAD_INIT(root_drmcs.drmcs.clients),
+};
+
+static DEFINE_MUTEX(drmcg_mutex);
 
 static inline struct drm_cgroup_state *
 css_to_drmcs(struct cgroup_subsys_state *css)
@@ -40,11 +48,63 @@ drmcs_alloc(struct cgroup_subsys_state *parent_css)
 		drmcs = kzalloc(sizeof(*drmcs), GFP_KERNEL);
 		if (!drmcs)
 			return ERR_PTR(-ENOMEM);
+
+		INIT_LIST_HEAD(&drmcs->clients);
 	}
 
 	return &drmcs->css;
 }
 
+void drmcgroup_client_open(struct drm_file *file_priv)
+{
+	struct drm_cgroup_state *drmcs;
+
+	drmcs = css_to_drmcs(task_get_css(current, drm_cgrp_id));
+
+	mutex_lock(&drmcg_mutex);
+	file_priv->__css = &drmcs->css; /* Keeps the reference. */
+	list_add_tail(&file_priv->clink, &drmcs->clients);
+	mutex_unlock(&drmcg_mutex);
+}
+EXPORT_SYMBOL_GPL(drmcgroup_client_open);
+
+void drmcgroup_client_close(struct drm_file *file_priv)
+{
+	struct drm_cgroup_state *drmcs;
+
+	drmcs = css_to_drmcs(file_priv->__css);
+
+	mutex_lock(&drmcg_mutex);
+	list_del(&file_priv->clink);
+	file_priv->__css = NULL;
+	mutex_unlock(&drmcg_mutex);
+
+	css_put(&drmcs->css);
+}
+EXPORT_SYMBOL_GPL(drmcgroup_client_close);
+
+void drmcgroup_client_migrate(struct drm_file *file_priv)
+{
+	struct drm_cgroup_state *src, *dst;
+	struct cgroup_subsys_state *old;
+
+	mutex_lock(&drmcg_mutex);
+
+	old = file_priv->__css;
+	src = css_to_drmcs(old);
+	dst = css_to_drmcs(task_get_css(current, drm_cgrp_id));
+
+	if (src != dst) {
+		file_priv->__css = &dst->css; /* Keeps the reference. */
+		list_move_tail(&file_priv->clink, &dst->clients);
+	}
+
+	mutex_unlock(&drmcg_mutex);
+
+	css_put(old);
+}
+EXPORT_SYMBOL_GPL(drmcgroup_client_migrate);
+
 struct cftype files[] = {
 	{ } /* Zero entry terminates. */
 };
-- 
2.48.0