drm/i915/gvt: Use list_entry to access list members

Use list_entry() instead of container_of() to access list members.
Also drop unnecessary and misleading NULL checks on the result of
list_entry().

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20210523172304.3033229-1-linux@roeck-us.net
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>

Author: groeck

drivers/gpu/drm/i915/gvt/dmabuf.c

@@ -148,8 +148,7 @@ static void dmabuf_gem_object_free(struct kref *kref)
 
 	if (vgpu && vgpu->active && !list_empty(&vgpu->dmabuf_obj_list_head)) {
 		list_for_each(pos, &vgpu->dmabuf_obj_list_head) {
-			dmabuf_obj = container_of(pos,
-					struct intel_vgpu_dmabuf_obj, list);
+			dmabuf_obj = list_entry(pos, struct intel_vgpu_dmabuf_obj, list);
 			if (dmabuf_obj == obj) {
 				list_del(pos);
 				intel_gvt_hypervisor_put_vfio_device(vgpu);
@@ -357,10 +356,8 @@ pick_dmabuf_by_info(struct intel_vgpu *vgpu,
 	struct intel_vgpu_dmabuf_obj *ret = NULL;
 
 	list_for_each(pos, &vgpu->dmabuf_obj_list_head) {
-		dmabuf_obj = container_of(pos, struct intel_vgpu_dmabuf_obj,
-						list);
-		if ((dmabuf_obj == NULL) ||
-		    (dmabuf_obj->info == NULL))
+		dmabuf_obj = list_entry(pos, struct intel_vgpu_dmabuf_obj, list);
+		if (!dmabuf_obj->info)
 			continue;
 
 		fb_info = (struct intel_vgpu_fb_info *)dmabuf_obj->info;
@@ -387,11 +384,7 @@ pick_dmabuf_by_num(struct intel_vgpu *vgpu, u32 id)
 	struct intel_vgpu_dmabuf_obj *ret = NULL;
 
 	list_for_each(pos, &vgpu->dmabuf_obj_list_head) {
-		dmabuf_obj = container_of(pos, struct intel_vgpu_dmabuf_obj,
-						list);
-		if (!dmabuf_obj)
-			continue;
-
+		dmabuf_obj = list_entry(pos, struct intel_vgpu_dmabuf_obj, list);
 		if (dmabuf_obj->dmabuf_id == id) {
 			ret = dmabuf_obj;
 			break;
@@ -600,8 +593,7 @@ void intel_vgpu_dmabuf_cleanup(struct intel_vgpu *vgpu)
 
 	mutex_lock(&vgpu->dmabuf_lock);
 	list_for_each_safe(pos, n, &vgpu->dmabuf_obj_list_head) {
-		dmabuf_obj = container_of(pos, struct intel_vgpu_dmabuf_obj,
-						list);
+		dmabuf_obj = list_entry(pos, struct intel_vgpu_dmabuf_obj, list);
 		dmabuf_obj->vgpu = NULL;
 
 		idr_remove(&vgpu->object_idr, dmabuf_obj->dmabuf_id);