drm/gem: handlecount isn't really a kref so don't make it one.

There were lots of places being inconsistent since handle count
looked like a kref but it really wasn't.

Fix this my just making handle count an atomic on the object,
and have it increase the normal object kref.

Now i915/radeon/nouveau drivers can drop the normal reference on
userspace object creation, and have the handle hold it.

This patch fixes a memory leak or corruption on unload, because
the driver had no way of knowing if a handle had been actually
added for this object, and the fbcon object needed to know this
to clean itself up properly.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_gem.c

@@ -148,7 +148,7 @@ int drm_gem_object_init(struct drm_device *dev,
 		return -ENOMEM;
 
 	kref_init(&obj->refcount);
-	kref_init(&obj->handlecount);
+	atomic_set(&obj->handle_count, 0);
 	obj->size = size;
 
 	atomic_inc(&dev->object_count);
@@ -496,12 +496,8 @@ static void drm_gem_object_ref_bug(struct kref *list_kref)
  * called before drm_gem_object_free or we'll be touching
  * freed memory
  */
-void
-drm_gem_object_handle_free(struct kref *kref)
+void drm_gem_object_handle_free(struct drm_gem_object *obj)
 {
-	struct drm_gem_object *obj = container_of(kref,
-						  struct drm_gem_object,
-						  handlecount);
 	struct drm_device *dev = obj->dev;
 
 	/* Remove any name for this object */

drivers/gpu/drm/drm_info.c

@@ -255,7 +255,7 @@ int drm_gem_one_name_info(int id, void *ptr, void *data)
 
 	seq_printf(m, "%6d %8zd %7d %8d\n",
 		   obj->name, obj->size,
-		   atomic_read(&obj->handlecount.refcount),
+		   atomic_read(&obj->handle_count),
 		   atomic_read(&obj->refcount.refcount));
 	return 0;
 }

drivers/gpu/drm/i915/i915_gem.c

@@ -136,14 +136,12 @@ i915_gem_create_ioctl(struct drm_device *dev, void *data,
 		return -ENOMEM;
 
 	ret = drm_gem_handle_create(file_priv, obj, &handle);
-	if (ret) {
+	/* drop reference from allocate - handle holds it now */
 	drm_gem_object_unreference_unlocked(obj);
+	if (ret) {
 		return ret;
 	}
 
-	/* Sink the floating reference from kref_init(handlecount) */
-	drm_gem_object_handle_unreference_unlocked(obj);
-
 	args->handle = handle;
 	return 0;
 }

drivers/gpu/drm/i915/intel_fb.c

@@ -237,8 +237,10 @@ int intel_fbdev_destroy(struct drm_device *dev,
 	drm_fb_helper_fini(&ifbdev->helper);
 
 	drm_framebuffer_cleanup(&ifb->base);
-	if (ifb->obj)
+	if (ifb->obj) {
+		drm_gem_object_handle_unreference(ifb->obj);
 		drm_gem_object_unreference(ifb->obj);
+	}
 
 	return 0;
 }

drivers/gpu/drm/nouveau/nouveau_fbcon.c

@@ -352,6 +352,7 @@ nouveau_fbcon_destroy(struct drm_device *dev, struct nouveau_fbdev *nfbdev)
 
 	if (nouveau_fb->nvbo) {
 		nouveau_bo_unmap(nouveau_fb->nvbo);
+		drm_gem_object_handle_unreference_unlocked(nouveau_fb->nvbo->gem);
 		drm_gem_object_unreference_unlocked(nouveau_fb->nvbo->gem);
 		nouveau_fb->nvbo = NULL;
 	}

drivers/gpu/drm/nouveau/nouveau_gem.c

@@ -167,11 +167,9 @@ nouveau_gem_ioctl_new(struct drm_device *dev, void *data,
 		goto out;
 
 	ret = drm_gem_handle_create(file_priv, nvbo->gem, &req->info.handle);
-out:
-	drm_gem_object_handle_unreference_unlocked(nvbo->gem);
-
-	if (ret)
+	/* drop reference from allocate - handle holds it now */
 	drm_gem_object_unreference_unlocked(nvbo->gem);
+out:
 	return ret;
 }
 

drivers/gpu/drm/nouveau/nouveau_notifier.c

@@ -79,6 +79,7 @@ nouveau_notifier_takedown_channel(struct nouveau_channel *chan)
 	mutex_lock(&dev->struct_mutex);
 	nouveau_bo_unpin(chan->notifier_bo);
 	mutex_unlock(&dev->struct_mutex);
+	drm_gem_object_handle_unreference_unlocked(chan->notifier_bo->gem);
 	drm_gem_object_unreference_unlocked(chan->notifier_bo->gem);
 	drm_mm_takedown(&chan->notifier_heap);
 }

drivers/gpu/drm/radeon/radeon_display.c

@@ -843,8 +843,9 @@ static void radeon_user_framebuffer_destroy(struct drm_framebuffer *fb)
 {
 	struct radeon_framebuffer *radeon_fb = to_radeon_framebuffer(fb);
 
-	if (radeon_fb->obj)
+	if (radeon_fb->obj) {
 		drm_gem_object_unreference_unlocked(radeon_fb->obj);
+	}
 	drm_framebuffer_cleanup(fb);
 	kfree(radeon_fb);
 }

drivers/gpu/drm/radeon/radeon_fb.c

@@ -94,8 +94,10 @@ static void radeonfb_destroy_pinned_object(struct drm_gem_object *gobj)
 	ret = radeon_bo_reserve(rbo, false);
 	if (likely(ret == 0)) {
 		radeon_bo_kunmap(rbo);
+		radeon_bo_unpin(rbo);
 		radeon_bo_unreserve(rbo);
 	}
+	drm_gem_object_handle_unreference(gobj);
 	drm_gem_object_unreference_unlocked(gobj);
 }
 
@@ -325,8 +327,6 @@ static int radeon_fbdev_destroy(struct drm_device *dev, struct radeon_fbdev *rfb
 {
 	struct fb_info *info;
 	struct radeon_framebuffer *rfb = &rfbdev->rfb;
-	struct radeon_bo *rbo;
-	int r;
 
 	if (rfbdev->helper.fbdev) {
 		info = rfbdev->helper.fbdev;
@@ -338,14 +338,8 @@ static int radeon_fbdev_destroy(struct drm_device *dev, struct radeon_fbdev *rfb
 	}
 
 	if (rfb->obj) {
-		rbo = rfb->obj->driver_private;
-		r = radeon_bo_reserve(rbo, false);
-		if (likely(r == 0)) {
-			radeon_bo_kunmap(rbo);
-			radeon_bo_unpin(rbo);
-			radeon_bo_unreserve(rbo);
-		}
-		drm_gem_object_unreference_unlocked(rfb->obj);
+		radeonfb_destroy_pinned_object(rfb->obj);
+		rfb->obj = NULL;
 	}
 	drm_fb_helper_fini(&rfbdev->helper);
 	drm_framebuffer_cleanup(&rfb->base);

drivers/gpu/drm/radeon/radeon_gem.c

@@ -201,11 +201,11 @@ int radeon_gem_create_ioctl(struct drm_device *dev, void *data,
 		return r;
 	}
 	r = drm_gem_handle_create(filp, gobj, &handle);
-	if (r) {
+	/* drop reference from allocate - handle holds it now */
 	drm_gem_object_unreference_unlocked(gobj);
+	if (r) {
 		return r;
 	}
-	drm_gem_object_handle_unreference_unlocked(gobj);
 	args->handle = handle;
 	return 0;
 }

include/drm/drmP.h

@@ -612,7 +612,7 @@ struct drm_gem_object {
 	struct kref refcount;
 
 	/** Handle count of this object. Each handle also holds a reference */
-	struct kref handlecount;
+	atomic_t handle_count; /* number of handles on this object */
 
 	/** Related drm device */
 	struct drm_device *dev;
@@ -1461,7 +1461,7 @@ struct drm_gem_object *drm_gem_object_alloc(struct drm_device *dev,
 					    size_t size);
 int drm_gem_object_init(struct drm_device *dev,
 			struct drm_gem_object *obj, size_t size);
-void drm_gem_object_handle_free(struct kref *kref);
+void drm_gem_object_handle_free(struct drm_gem_object *obj);
 void drm_gem_vm_open(struct vm_area_struct *vma);
 void drm_gem_vm_close(struct vm_area_struct *vma);
 int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma);
@@ -1496,7 +1496,7 @@ static inline void
 drm_gem_object_handle_reference(struct drm_gem_object *obj)
 {
 	drm_gem_object_reference(obj);
-	kref_get(&obj->handlecount);
+	atomic_inc(&obj->handle_count);
 }
 
 static inline void
@@ -1505,12 +1505,15 @@ drm_gem_object_handle_unreference(struct drm_gem_object *obj)
 	if (obj == NULL)
 		return;
 
+	if (atomic_read(&obj->handle_count) == 0)
+		return;
 	/*
 	 * Must bump handle count first as this may be the last
 	 * ref, in which case the object would disappear before we
 	 * checked for a name
 	 */
-	kref_put(&obj->handlecount, drm_gem_object_handle_free);
+	if (atomic_dec_and_test(&obj->handle_count))
+		drm_gem_object_handle_free(obj);
 	drm_gem_object_unreference(obj);
 }
 
@@ -1520,12 +1523,17 @@ drm_gem_object_handle_unreference_unlocked(struct drm_gem_object *obj)
 	if (obj == NULL)
 		return;
 
+	if (atomic_read(&obj->handle_count) == 0)
+		return;
+
 	/*
 	* Must bump handle count first as this may be the last
 	* ref, in which case the object would disappear before we
 	* checked for a name
 	*/
-	kref_put(&obj->handlecount, drm_gem_object_handle_free);
+
+	if (atomic_dec_and_test(&obj->handle_count))
+		drm_gem_object_handle_free(obj);
 	drm_gem_object_unreference_unlocked(obj);
 }