Re: [Qemu-devel] [PATCH 14/18] nbd: Implement NBD_OPT_GO on client

[Eric Blake <eblake@redhat.com>]

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On 04/09/2016 04:47 AM, Alex Bligh wrote:
> 
> On 8 Apr 2016, at 23:05, Eric Blake <eblake@redhat.com> wrote:
> 
>> NBD_OPT_EXPORT_NAME is lousy: it doesn't have any sane error
>> reporting.  Upstream NBD recently added NBD_OPT_GO as the
> 
> ... as an experimental option for now, but hopefully this
> should move it out the experimental section.
> 
> Thanks for doing this one.
> 
>> improved version of the option that does what we want: it
>> reports sane errors on failures (including when a server
>> requires TLS but does not have NBD_OPT_GO!), and on success
>> it concludes with the same data as NBD_OPT_EXPORT_NAME sends.
>>
>> Signed-off-by: Eric Blake <eblake@redhat.com>
> 
> Perhaps worth adding that although all servers that support
> FixedNewstyle are meant to support (i.e. error but not disconnect on)
> unsupported options, perhaps some don't (in which case they
> are buggy and should be fixed). But just in case someone asks
> 'why is qemu no longer connecting to shonkynbd', a message in
> the commit log might be useful.

qemu 2.5 is one of those 'shonkynbd' servers.  We just barely fixed it
in commit 156f6a10 in time for 2.6, but now you've made me worry whether
that will be a big enough problem to have to hack around in newer qemu
clients.  On the other hand, we won't merge the NBD_OPT_GO code until
qemu 2.7, a few more months down the road; and we can get the fix
backported to the 2.5.x stable series in the meantime.

> 
> Otherwise:
> 
> Reviewed-by: Alex Bligh <alex@alex.org.uk>
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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