IORING_FSYNC_DATASYNC
if (unlikely(sync->flags & ~IORING_FSYNC_DATASYNC))
sync->flags & IORING_FSYNC_DATASYNC);
io_uring_prep_fsync(sqe[0], ublk_get_registered_fd(q, 1) /*fds[1]*/, IORING_FSYNC_DATASYNC);
io_uring_prep_fsync(sqe[i], i + 1, IORING_FSYNC_DATASYNC);