The bdev->bd_disk, !bdev_get_queue and q->make_request_fn checks
are all things you don't need, any blkdev_issue_flush should not
either, although I'll need to look into the weird loop workaround
again, which doesn't make much sense to me.

  I tried to confirm q->make_request_fn and got lost, I am going to
  try again.

Thanks, Anand