static int rbd_obj_read_sync(struct rbd_device *rbd_dev,
                                const char *object_name,
                                u64 offset, u64 length,
-                               char *buf, u64 *version)
+                               void *buf, u64 *version)
 
 {
        struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc;
                        return ERR_PTR(-ENOMEM);
 
                ret = rbd_obj_read_sync(rbd_dev, rbd_dev->header_name,
-                                      0, size,
-                                      (char *) ondisk, version);
+                                      0, size, ondisk, version);
                if (ret < 0)
                        goto out_err;
                if (WARN_ON((size_t) ret < size)) {