> Busy waiting is not acceptable here (it can be unbounded if, for example, an
> NFS server is on the other side of a network partition). You have to add a
> bottom half to qemu_laio_state that calls ioq_submit, and schedule it after
> calling io_getevents.
>
> If the bottom half is already scheduled and the queue is full, I guess
> there's no other choice than returning -EAGAIN from ioq_enqueue and
> ultimately to the guest.
That is a bit complicated, as you mentioned it is close to
2.1 release, could we just keep it simple to return failure to guest
after retrying several times? Actually, previous dataplane handles
it by exit(-1), which is unfriendly absolutely.