Re: [Nbd] [PATCH v4 04/11] nbd: Improve server handling of bogus commands

[Alex Bligh <alex@...872...>]

> On 14 Jun 2016, at 16:11, Paolo Bonzini <pbonzini@...696...> wrote:
> 
>> To illustrate the problem, look consider what qemu itself would do as
>> a server if it can't buffer the entire read issued to it.
> 
> Return ENOMEM?

Well OK, qemu then 'works' on the basis it breaks another
part of the spec, which is coping with long reads.

> However, it looks like the
> de facto status prior to structured replies is that the error is in the
> spec, and this patch introduces a regression.

Well, I guess the patch makes it work the same as the
reference server implementation and the spec, which I'd
consider a fix. My view is that the error is in the
kernel client. I think Erik CC'd in nbd-general
re the comment that the spec was broken; I don't think
it is, and don't propose to change it. Wouter might or
might not feel differently.

It's been reasonably well known (I wrote about it
at least 3 years ago), that the current implementation
(reference + kernel) does not cope well with errors
on reads, so I'm guessing one is just trading one
set of brokenness for another. So I'm pretty relaxed
about what goes in qemu.

-- 
Alex Bligh