> On the other hand, Nicholas's work includes timeout and reconnect. I'm
> not sure how complicated it is to include it in my series, but probably
> not much. With coroutines, preserving the list of outstanding I/O
> requests is done implicitly by the CoMutex, so you basically have to
> check errno for ECONNRESET and similar errors, reconnect, and retry
> issuing the current request only.
Definitely a simpler approach than my version. Although, does your
version preserve write ordering? I was quite careful to ensure that
write requests would always be sent in the order they were presented;
although I don't know if qemu proper depends on that behaviour or not.
> Timeout can be done with a QEMUTimer that shuts down the socket
> (shutdown(2) I mean). This triggers an EPIPE when writing, or a
> zero-sized read when reading. The timeout can be set every time the
> coroutine is (re)entered, and reset before exiting nbd_co_readv/writev.
for reconnect, I did consider using QEMUTimer, but when I tried it I ran
into linking problems with qemu-io. As far as I can tell, resolving that
is a significant code reorganisation - QEMUTimer pulls in lots of code
that isn't linked in at the moment (VM clocks, etc). I'm not sure it's
worth tackling that to avoid using timer_create(2).