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Subject: Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements
From: Alex Bligh <alex@alex.org.uk>
In-Reply-To: <20160915124103.GA20657@infradead.org>
Date: Thu, 15 Sep 2016 13:44:29 +0100
Cc: Alex Bligh <alex@alex.org.uk>, Wouter Verhelst <w@uter.be>,
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To: Christoph Hellwig <hch@infradead.org>
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> On 15 Sep 2016, at 13:41, Christoph Hellwig <hch@infradead.org> wrote:
> 
> On Thu, Sep 15, 2016 at 01:39:11PM +0100, Alex Bligh wrote:
>> That's probably right in the case of file-based back ends that
>> are running on a Linux OS. But gonbdserver for instance supports
>> (e.g.) Ceph based backends, where each connection might be talking
>> to a completely separate ceph node, and there may be no cache
>> consistency between connections.
> 
> Yes, if you don't have a cache coherent backend you are generally
> screwed with a multiqueue protocol.

I wonder if the ability to support multiqueue should be visible
in the negotiation stage. That would allow the client to refuse
to select multiqueue where it isn't safe.

Wouter?

-- 
Alex Bligh