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From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: qemu-block@nongnu.org
Cc: qemu-devel@nongnu.org, mreitz@redhat.com, kwolf@redhat.com,
	eblake@redhat.com, rvkagan@yandex-team.ru, den@openvz.org
Subject: DROP THIS Re: [PATCH 00/14] nbd: move reconnect-thread to separate file
Date: Thu, 8 Apr 2021 13:03:55 +0300	[thread overview]
Message-ID: <13074b0f-3b83-8db5-2ef4-a5e0060d15cc@virtuozzo.com> (raw)
In-Reply-To: <20210407104637.36033-1-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


      parent reply	other threads:[~2021-04-08 10:05 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-07 10:46 Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 01/14] block/nbd: BDRVNBDState: drop unused connect_err Vladimir Sementsov-Ogievskiy
2021-04-07 11:13   ` Roman Kagan
2021-04-07 10:46 ` [PATCH 02/14] block/nbd: nbd_co_establish_connection(): drop unused errp Vladimir Sementsov-Ogievskiy
2021-04-07 11:28   ` Roman Kagan
2021-04-07 10:46 ` [PATCH 03/14] block/nbd: drop unused NBDConnectThread::err field Vladimir Sementsov-Ogievskiy
2021-04-07 11:42   ` Roman Kagan
2021-04-07 11:55     ` Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 04/14] block/nbd: split connect_thread_cb() out of connect_thread_func() Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 05/14] block/nbd: rename NBDConnectThread to NBDConnectCB Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 06/14] block/nbd: further segregation of connect-thread Vladimir Sementsov-Ogievskiy
2021-04-08 10:44   ` Roman Kagan
2021-04-07 10:46 ` [PATCH 07/14] block/nbd: drop nbd_free_connect_thread() Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 08/14] block/nbd: move nbd connect-thread to nbd/client-connect.c Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 09/14] block/nbd: NBDConnectCB: drop bh_* fields Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 10/14] block/nbd: move wait_connect field under mutex protection Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 11/14] block/nbd: refactor connect_bh() Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 12/14] block/nbd: refactor nbd_co_establish_connection Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 13/14] block/nbd: nbd_co_establish_connection_cancel(): rename wake to do_wake Vladimir Sementsov-Ogievskiy
2021-04-07 10:46 ` [PATCH 14/14] block/nbd: drop thr->state Vladimir Sementsov-Ogievskiy
2021-04-08 10:03 ` Vladimir Sementsov-Ogievskiy [this message]

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