selftests/ublk: fix error handling for starting device

Fix error handling in ublk_start_daemon() when start_dev fails:

1. Call ublk_ctrl_stop_dev() to cancel inflight uring_cmd before
   cleanup. Without this, the device deletion may hang waiting for
   I/O completion that will never happen.

2. Add fail_start label so that pthread_join() is called on the
   error path. This ensures proper thread cleanup when startup fails.

Fixes: 6aecda0 ("selftests: ublk: add kernel selftests for ublk")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Ming Lei

tools/testing/selftests/ublk/kublk.c

@@ -1054,15 +1054,17 @@ static int ublk_start_daemon(const struct dev_ctx *ctx, struct ublk_dev *dev)
 	}
 	if (ret < 0) {
 		ublk_err("%s: ublk_ctrl_start_dev failed: %d\n", __func__, ret);
-		goto fail;
+		/* stop device so that inflight uring_cmd can be cancelled */
+		ublk_ctrl_stop_dev(dev);
+		goto fail_start;
 	}
 
 	ublk_ctrl_get_info(dev);
 	if (ctx->fg)
 		ublk_ctrl_dump(dev);
 	else
 		ublk_send_dev_event(ctx, dev, dev->dev_info.dev_id);
-
+fail_start:
 	/* wait until we are terminated */
 	for (i = 0; i < dev->nthreads; i++)
 		pthread_join(tinfo[i].thread, &thread_ret);