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From: Paolo Bonzini <pbonzini@redhat.com>
To: Wouter Verhelst <w@uter.be>, Pavel Borzenkov <pborzenkov@virtuozzo.com>
Cc: nbd-general@lists.sourceforge.net,
	"Denis V. Lunev" <den@openvz.org>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	qemu-devel@nongnu.org, Kevin Wolf <kwolf@redhat.com>
Subject: Re: [Qemu-devel] [Nbd] [PATCH 1/2] NBD proto: add WRITE_ZEROES extension
Date: Thu, 24 Mar 2016 12:37:33 +0100	[thread overview]
Message-ID: <56F3D17D.7040100@redhat.com> (raw)
In-Reply-To: <20160324082641.GF1590@grep.be>



On 24/03/2016 09:26, Wouter Verhelst wrote:
>> > 
>> > No, there is no specific reason. Looks like NBD_CMD_FLAG_ZEROES fits the
>> > spec and implementations nicely. So I'll rewrite the extension and add
>> > the flag instead of the whole command.
> Actually, having given this some more thought...
> 
> There is at least one server-side implementation of nbd (mine) which
> silently ignores flags it doesn't know about. This isn't a problem for
> non-critical flags, but it could be a problem for a flag like this. Of
> course, a client shouldn't send a flag to a server which that server
> hasn't heard of, but mistakes do happen.
> 
> Do we want to keep that in mind? If so, we might want to keep it as a
> separate command after all.
> 
> OTOH, it could be said that silently ignoring unknown messages is a bug.
> I should probably just fix my implementation instead.

Even if it is a bug, it does suggest that the payload format should not
be changed by flags.  For example ignoring flags is a bug for an NBD
server, but not for a Wireshark protocol dissector.

Paolo

  parent reply	other threads:[~2016-03-24 11:37 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-23 14:16 [Qemu-devel] [PATCH 0/2] NBD protocol extensions: WRITE_ZEROES and GET_LBA_STATUS Denis V. Lunev
2016-03-23 14:16 ` [Qemu-devel] [PATCH 1/2] NBD proto: add WRITE_ZEROES extension Denis V. Lunev
2016-03-23 15:14   ` Eric Blake
2016-03-23 17:40     ` [Qemu-devel] [Nbd] " Wouter Verhelst
2016-03-24  7:16     ` [Qemu-devel] " Pavel Borzenkov
2016-03-24  7:36       ` [Qemu-devel] [Nbd] " Wouter Verhelst
2016-03-23 17:21   ` Wouter Verhelst
2016-03-24  7:57     ` Pavel Borzenkov
2016-03-24  8:26       ` Wouter Verhelst
2016-03-24 11:35         ` Pavel Borzenkov
2016-03-24 11:37         ` Paolo Bonzini [this message]
2016-03-24 12:31           ` Wouter Verhelst
2016-03-24 14:53         ` Eric Blake
2016-03-23 14:16 ` [Qemu-devel] [PATCH 2/2] NBD proto: add GET_LBA_STATUS extension Denis V. Lunev
2016-03-23 16:27   ` Eric Blake
2016-03-24 12:30     ` Pavel Borzenkov
2016-03-24 15:04       ` Eric Blake
2016-03-24 16:36         ` Pavel Borzenkov
2016-03-23 17:58   ` [Qemu-devel] [Nbd] " Wouter Verhelst
2016-03-23 18:14     ` Kevin Wolf
2016-03-24  8:25       ` Pavel Borzenkov
2016-03-24  8:41         ` Wouter Verhelst
2016-03-24 11:36           ` Pavel Borzenkov
2016-03-24 12:32             ` Wouter Verhelst
2016-03-24  8:43     ` Pavel Borzenkov
2016-03-24  9:33       ` Wouter Verhelst
2016-03-24 10:32         ` Alex Bligh
2016-03-24 11:58           ` Paolo Bonzini
2016-03-24 12:17             ` Alex Bligh
2016-03-24 12:32               ` Paolo Bonzini
2016-03-24 13:31                 ` Alex Bligh
2016-03-24 13:32                   ` Paolo Bonzini
2016-03-24 11:55     ` Paolo Bonzini
2016-03-24 12:43       ` Wouter Verhelst
2016-03-24 15:25       ` Eric Blake
2016-03-24 15:33         ` Paolo Bonzini
2016-03-24 15:53           ` Wouter Verhelst
2016-03-24 16:04             ` Eric Blake
2016-03-24 16:07               ` Kevin Wolf
2016-03-24 16:47                 ` Wouter Verhelst
2016-03-29  9:38                   ` Kevin Wolf
2016-03-29  9:53                     ` Wouter Verhelst
2016-03-29 10:25                     ` Paolo Bonzini
2016-03-24 22:08   ` [Qemu-devel] " Eric Blake
2016-03-25  8:49     ` [Qemu-devel] [Nbd] " Wouter Verhelst
2016-03-25  9:01       ` Alex Bligh
2016-03-28 15:58       ` Eric Blake
2016-04-04 10:32         ` Markus Pargmann
2016-04-04 10:18       ` Markus Pargmann
2016-04-04 16:54         ` Eric Blake
2016-04-04 22:17         ` Wouter Verhelst
2016-04-04 16:40   ` [Qemu-devel] " Eric Blake
2016-04-04 20:16   ` Denis V. Lunev
2016-04-04 20:36     ` [Qemu-devel] [Nbd] " Eric Blake

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