Re: [PATCH v5 4/5] block/nbd: drop connection_co

[Vladimir Sementsov-Ogievskiy]

[add Roman}

14.07.2021 19:59, Vladimir Sementsov-Ogievskiy wrote:
> OK, that's a big rewrite of the logic.
>
> Pre-patch we have an always running coroutine - connection_co. It does
> reply receiving and reconnecting. And it leads to a lot of difficult
> and unobvious code around drained sections and context switch. We also
> abuse bs->in_flight counter which is increased for connection_co and
> temporary decreased in points where we want to allow drained section to
> begin. One of these place is in another file: in nbd_read_eof() in
> nbd/client.c.
>
> We also cancel reconnect and requests waiting for reconnect on drained
> begin which is not correct.

And this patch fixes that.

> Let's finally drop this always running coroutine and go another way:

Hmm here is missed something like:

  go another way: do both reconnect and receiving in request coroutines.
  The detailed list of changes below (in the sequence of diff hunks).

> 1. receiving coroutines are woken directly from nbd_channel_error, when
>     we change s->state
>
> 2. nbd_co_establish_connection_cancel(): we don't have drain_begin now,
>     and in nbd_teardown_connection() all requests should already be
>     finished (and reconnect is done from request). So
>     nbd_co_establish_connection_cancel() is called from
>     nbd_cancel_in_flight() (to cancel the request that is doing


--
Best regards,
Vladimir