drm/gem: Add drm_gem_pin_unlocked()

Add unlocked variants of drm_gem_un/pin() functions and make them public.
These new helpers will take care of GEM dma-reservation locking for DRM
drivers.

We are going to add memory shrinking support to the VirtIO-GPU driver
that will need to pin framebuffers explicitly to prevent eviction of the
actively used buffers by the shrinker. VirtIO-GPU driver will use these
new generic helpers to pin shmem framebuffers.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>

drivers/gpu/drm/drm_gem.c

@@ -1179,6 +1179,35 @@ void drm_gem_unpin(struct drm_gem_object *obj)
 		obj->funcs->unpin(obj);
 }
 
+int drm_gem_pin_unlocked(struct drm_gem_object *obj)
+{
+	int ret;
+
+	if (!obj->funcs->pin)
+		return 0;
+
+	ret = dma_resv_lock_interruptible(obj->resv, NULL);
+	if (ret)
+		return ret;
+
+	ret = obj->funcs->pin(obj);
+	dma_resv_unlock(obj->resv);
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_gem_pin_unlocked);
+
+void drm_gem_unpin_unlocked(struct drm_gem_object *obj)
+{
+	if (!obj->funcs->unpin)
+		return;
+
+	dma_resv_lock(obj->resv, NULL);
+	obj->funcs->unpin(obj);
+	dma_resv_unlock(obj->resv);
+}
+EXPORT_SYMBOL(drm_gem_unpin_unlocked);
+
 int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map)
 {
 	int ret;

include/drm/drm_gem.h

@@ -413,4 +413,7 @@ int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
 int drm_gem_vmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map);
 void drm_gem_vunmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map);
 
+int drm_gem_pin_unlocked(struct drm_gem_object *obj);
+void drm_gem_unpin_unlocked(struct drm_gem_object *obj);
+
 #endif /* __DRM_GEM_H__ */