From: Paolo Bonzini <pbonzini@redhat.com>
To: Eric Blake <eblake@redhat.com>, Wouter Verhelst <w@uter.be>,
"Denis V. Lunev" <den@openvz.org>
Cc: nbd-general@lists.sourceforge.net, Kevin Wolf <kwolf@redhat.com>,
qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [Qemu-devel] [Nbd] [PATCH 2/2] NBD proto: add GET_LBA_STATUS extension
Date: Thu, 24 Mar 2016 16:33:42 +0100 [thread overview]
Message-ID: <56F408D6.2020002@redhat.com> (raw)
In-Reply-To: <56F406E7.4010207@redhat.com>
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On 24/03/2016 16:25, Eric Blake wrote:
>> However, let's make these bits, so that
>>
>> NBD_STATE_ALLOCATED (0x1), LBA extent is present on the block device
>> NBD_STATE_ZERO (0x2), LBA extent will read as zeroes
>
> Should we flip the sense and call this NBD_STATE_UNALLOCATED (0 means
> allocated, 1 means not present), so that an overall status of 0 is a
> safe default?
Double negations are evil (and don't work the same in all languages), so
I think it's a worse option.
>> An implementation that doesn't track the "dirtiness" state of blocks
>> MUST either fail this command with EINVAL, or mark all blocks as
>> dirty in the descriptor that it returns.
>
> Is it feasible to return zero/allocated/dirty status all at the same
> time, or do we want to strictly require two different modes of
> operation?
I think we should differentiate them, because it makes sense to support
only one.
In particular, while it is more or less obvious that (in my proposal
above) a trivial implementation must return NBD_STATE_ALLOCATED, it is
quite weird to require a trivial implementation to return
NBD_STATE_ALLOCATED|NBD_STATE_DIRTY.
Paolo
> That is, if we are returning zero and allocated as two bits,
> can we also return a third bit for dirty/clean? Should we flip the
> sense of the bit, where 0 means dirty and 1 means clean, again so that a
> server can always return a status of 0 as the safe default?
>
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next prev parent reply other threads:[~2016-03-24 15:33 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
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 [this message]
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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