Re: [Qemu-devel] [PATCH v2 3/6] qapi: add nbd-server-remove

[Eric Blake]

On 01/12/2018 03:47 AM, Vladimir Sementsov-Ogievskiy wrote:
> 09.01.2018 22:52, Eric Blake wrote:
>> On 12/07/2017 09:50 AM, Vladimir Sementsov-Ogievskiy wrote:
>>> Add command for export removing. It is needed for cases when we
>>> don't want to keep export after the operation on it was completed.
>>> The other example is temporary node, created with blockdev-add.
>>> If we want to delete it we should firstly remove corresponding
>>> NBD export.
>>>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
>>> ---

>> Do we want a third mode in the middle, where the server starts replying
>> to all existing clients with ESHUTDOWN errors for all new requests
>> rather than abruptly disconnecting (no new I/O, but no forced disconnect
>> and pending in-flight transactions can still complete gracefully)?
> 
> looks interesting. what about the following naming?
> 
> @mode: possible values:
>               hide - just hide server from new clients, maintain
> existing connections,
>                           remove after all clients disconnected
>               soft - like hide, but answer with ESHUTDOWN for all
> further requests from
>                           existing connections
>               hard - hard disconnect all clients and remove server
>               (default: soft)

Or even a fourth mode that causes an immediate error return without
state change if there are any connected clients, but otherwise removes
the server.

> 
> new corresponding states of nbd export:
> hidden, shutting_down
> 
> and we allow transitions:
> 
> normal_execution -> hidden
> normal_execution -> shutting_down
> normal_execution -> exit
> hidden -> shutting_down
> hidden -> exit
> shutting_down -> exit

Seems reasonable.  Are you planning on tackling a respin of this series
incorporating that idea?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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