From: Wouter Verhelst <w@uter.be>
To: Pavel Borzenkov <pborzenkov@virtuozzo.com>
Cc: nbd-general@lists.sourceforge.net, Kevin Wolf <kwolf@redhat.com>,
qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
"Denis V. Lunev" <den@openvz.org>
Subject: Re: [Qemu-devel] [Nbd] [PATCH 1/2] NBD proto: add WRITE_ZEROES extension
Date: Thu, 24 Mar 2016 09:26:41 +0100 [thread overview]
Message-ID: <20160324082641.GF1590@grep.be> (raw)
In-Reply-To: <20160324075706.GA24831@phobos.sw.ru>
On Thu, Mar 24, 2016 at 10:57:06AM +0300, Pavel Borzenkov wrote:
> On Wed, Mar 23, 2016 at 06:21:16PM +0100, Wouter Verhelst wrote:
> > So, the semantics of your proposed WRITE_ZEROES are exactly the same as
> > the WRITE command, except that no payload is sent?
> >
> > In that case, I think it's slightly more sensible if we don't add a new
> > command, but instead just have an NBD_CMD_FLAG_ZEROES added to the WRITE
> > command instead. After all, they're going to be (mostly) the same
> > anyway.
> >
> > Did you propose a separate command for a specific reason that I'm
> > missing (or forgetting), or is that just an oversight?
>
> 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.
--
< ron> I mean, the main *practical* problem with C++, is there's like a dozen
people in the world who think they really understand all of its rules,
and pretty much all of them are just lying to themselves too.
-- #debian-devel, OFTC, 2016-02-12
next prev parent reply other threads:[~2016-03-24 8:27 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 [this message]
2016-03-24 11:35 ` Pavel Borzenkov
2016-03-24 11:37 ` Paolo Bonzini
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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