Description of problem:
syzbot reported hung task [1].  The following program is a simplified
version of the reproducer:

int main(void)
{
	int sv[2], fd;

	if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) < 0)
		return 1;
	if ((fd = open("/dev/nbd0", 0)) < 0)
		return 1;
	if (ioctl(fd, NBD_SET_SIZE_BLOCKS, 0x81) < 0)
		return 1;
	if (ioctl(fd, NBD_SET_SOCK, sv[0]) < 0)
		return 1;
	if (ioctl(fd, NBD_DO_IT) < 0)
		return 1;
	return 0;
}

When signal interrupt nbd_start_device_ioctl() waiting the condition
atomic_read(&config->recv_threads) == 0, the task can hung because it
waits the completion of the inflight IOs.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
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Actual results:


Expected results:


Additional info: