Re: [PATCH v9 01/12] nvme-core: introduce nvme_ctrl_get_by_path()

+struct nvme_ctrl *nvme_ctrl_get_by_path(const char *path)
+{
+	struct nvme_ctrl *ctrl;
+	struct file *f;
+
+	f = filp_open(path, O_RDWR, 0);
+	if (IS_ERR(f))
+		return ERR_CAST(f);
+
+	if (f->f_op != &nvme_dev_fops) {
+		ctrl = ERR_PTR(-EINVAL);
+		goto out_close;
+	}
+
+	ctrl = f->private_data;
+	nvme_get_ctrl(ctrl);
+
+out_close:
+	filp_close(f, NULL);
+
+	return ctrl;

No need for the empty line here.  Also can you make sure this new
code (and all the new exports) are only enabled if
CONFIG_NVME_TARGET_PASSTHRU is set.  Preferably by having a little
block at the end of this file with this function and the extra
exports with a big fat comment that they are only for nvmet-passthrough.