Do not leave stdin, stdout, stderr open after fork. stdout is the
tap-driver.pl pipe. If we keep the pipe open then tap-driver.pl will not
detect that qos-test has terminated and it will hang.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tests/qtest/vhost-user-blk-test.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tests/qtest/vhost-user-blk-test.c b/tests/qtest/vhost-user-blk-test.c
index f05f14c192..15daf8ccbc 100644
--- a/tests/qtest/vhost-user-blk-test.c
+++ b/tests/qtest/vhost-user-blk-test.c
@@ -749,6 +749,17 @@ static char *start_vhost_user_blk(GString *cmd_line, int vus_instances,
                    storage_daemon_command->str);
     pid_t pid = fork();
     if (pid == 0) {
+        /*
+         * Close standard file descriptors so tap-driver.pl pipe detects when
+         * our parent terminates.
+         */
+        close(0);
+        close(1);
+        close(2);
+        open("/dev/null", O_RDONLY);
+        open("/dev/null", O_WRONLY);
+        open("/dev/null", O_WRONLY);
+
         execlp("/bin/sh", "sh", "-c", storage_daemon_command->str, NULL);
         exit(1);
     }
-- 
2.26.2