DROP THIS Re: [PATCH 00/14] nbd: move reconnect-thread to separate file

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

07.04.2021 13:46, Vladimir Sementsov-Ogievskiy wrote:
> Hi all!
> 
> There are problems with nbd driver:
> 
>   - nbd reconnect is cancelled on drain, which is bad as Roman describes
>     in his "[PATCH 0/7] block/nbd: decouple reconnect from drain"
>   - nbd driver is too complicated around drained sections and aio context
>     switch. It's nearly impossible to follow all the logic, including
>     abuse of bs->in_flight, which is temporary decreased in some places
>     (like nbd_read_eof()). Additional reconnect thread and two different
>     state machines (we have BDRVNBDState::state and
>     BDRVNBDState::connect_thread->state) doesn't make things simpler :)
> 
> So, I have a plan:
> 
> 1. Move nbd negotiation to connect_thread
> 
> 2. Do receive NBD replies in request coroutines, not in connection_co
>    
>     At this point we can drop connection_co, and when we don't have
>     endless running coroutine, NBD driver becomes a usual block driver,
>     and we can drop abuse of bs->in_flight, and probably drop most of
>     complicated logic around drained section and aio context switch in
>     nbd driver.
> 
> 3. Still, as Roman describes, with [2] we loose a possibility to
>     reconnect immediately when connection breaks (with current code we
>     have endless read in reconnect_co, but actually for this to work
>     keep-alive should be setup correctly). So, we'll need to reinvent it,
>     checking connection periodically by timeout, with help of getsockopt
>     or just sending a kind of PING request (zero-length READ or something
>     like this).
> 
> And this series a kind of preparation. The main point of it is moving
> connect-thread to a separate file.
> 


Finally I don't like it. I'm in progress of creating new series to substitute this one, so don't waste your time on review.


-- 
Best regards,
Vladimir