drm/nv50-nvc0/vm: take client reference on shared channel vm

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_drv.h

@@ -48,6 +48,7 @@
 struct nouveau_fpriv {
 	spinlock_t lock;
 	struct list_head channels;
+	struct nouveau_vm *vm;
 };
 
 static inline struct nouveau_fpriv *

drivers/gpu/drm/nouveau/nouveau_state.c

@@ -767,6 +767,7 @@ static void nouveau_card_takedown(struct drm_device *dev)
 int
 nouveau_open(struct drm_device *dev, struct drm_file *file_priv)
 {
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
 	struct nouveau_fpriv *fpriv;
 
 	fpriv = kzalloc(sizeof(*fpriv), GFP_KERNEL);
@@ -776,6 +777,9 @@ nouveau_open(struct drm_device *dev, struct drm_file *file_priv)
 	spin_lock_init(&fpriv->lock);
 	INIT_LIST_HEAD(&fpriv->channels);
 
+	if (dev_priv->card_type >= NV_50)
+		nouveau_vm_ref(dev_priv->chan_vm, &fpriv->vm, NULL);
+
 	file_priv->driver_priv = fpriv;
 	return 0;
 }
@@ -791,6 +795,7 @@ void
 nouveau_postclose(struct drm_device *dev, struct drm_file *file_priv)
 {
 	struct nouveau_fpriv *fpriv = nouveau_fpriv(file_priv);
+	nouveau_vm_ref(NULL, &fpriv->vm, NULL);
 	kfree(fpriv);
 }