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From: Alex Bligh <alex@alex.org.uk>
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Date: Fri, 25 Mar 2016 09:01:25 +0000
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Subject: Re: [Qemu-devel] [Nbd] [PATCH 2/2] NBD proto: add GET_LBA_STATUS
	extension
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To: Wouter Verhelst <w@uter.be>
Cc: "nbd-general@lists.sourceforge.net" <nbd-general@lists.sourceforge.net>, Kevin Wolf <kwolf@redhat.com>, Alex Bligh <alex@alex.org.uk>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "Stefan stefanha@redhat. com" <stefanha@redhat.com>, "Denis V. Lunev" <den@openvz.org>, Paolo Bonzini <pbonzini@redhat.com>


On 25 Mar 2016, at 08:49, Wouter Verhelst <w@uter.be> wrote:

> Yes. This has been discussed on the nbd-general list in the past. There
> is also the (significant) problem of the server having maybe already
> sent out the header before discovering there is an error, at which point
> it can *only* drop the connection.

Indeed.

I think where we got to last time this was discussed was that the
server could have the option of returning 'chunks' of reply, each
chunk either being a {length, data} tuple, or an error. The total
data transmitted would add up to the full length if there is no
error.

>> I could write up a negotiation of global flags for structured reply
>> lengths as an extension proposal, if you think it is worth it.
> 
> I think it is worth it...

+1 - for NBD_CMD_READ too

-- 
Alex Bligh