From: Markus Armbruster <armbru@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>
Cc: Peter Krempa <pkrempa@redhat.com>,
qemu-devel@nongnu.org, Michael Roth <mdroth@linux.vnet.ibm.com>
Subject: Re: [PATCH v2 2/2] qapi: Allow introspecting fix for savevm's cooperation with blockdev
Date: Fri, 11 Oct 2019 13:10:54 +0200 [thread overview]
Message-ID: <8736fzfsg1.fsf@dusky.pond.sub.org> (raw)
In-Reply-To: <20191011090036.GA5158@localhost.localdomain> (Kevin Wolf's message of "Fri, 11 Oct 2019 11:00:36 +0200")
Kevin Wolf <kwolf@redhat.com> writes:
> Am 11.10.2019 um 08:08 hat Markus Armbruster geschrieben:
>> Kevin Wolf <kwolf@redhat.com> writes:
>>
>> > Am 02.10.2019 um 13:57 hat Markus Armbruster geschrieben:
[...]
>> >> So the problem is certain (common & sane) -blockdev use makes savevm
>> >> create additional, unwanted snapshots.
>> >
>> > Actually, the most common protocol driver is file-posix, which doesn't
>> > support snapshots, so usually the result was that savevm just fails
>> > because it can't snapshot something that it (incorrectly) thinks it
>> > should snapshot.
>>
>> v3's commit message:
>>
>> qapi: Allow introspecting fix for savevm's cooperation with blockdev
>>
>> 'savevm' was buggy as it considered all monitor-owned block device nodes
>> for snapshot. With introduction of -blockdev the common usage made all
>> nodes including protocol and backing file nodes monitor-owned and thus
>> considered for snapshot.
>>
>> This is a problem since the 'file' protocol nodes can't have internal
>> snapshots and it does not make sense to take snapshot of nodes
>> representing backing files.
>>
>> This was fixed by commit 05f4aced658a02b02 clients need to be able to
>> detect whether this fix is present.
>
> Something is missing in this sentence. I think you lost the "but" from
> the original message.
I fixed this in v4 by inserting a period. I wasn't aware we had lost a
"but".
>> Since savevm does not have an QMP alternative, add the feature for the
>> 'human-monitor-command' backdoor which is used to call this command in
>> modern use.
>>
>> Signed-off-by: Peter Krempa <pkrempa@redhat.com>
>>
>> Kevin, is this explanation sufficiently correct & complete?
>
> Looks good to me otherwise.
Thanks!
next prev parent reply other threads:[~2019-10-11 11:12 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-20 14:26 [PATCH v2 0/2] qapi: Add detection for the 'savevm' fix for blockdev Peter Krempa
2019-09-20 14:26 ` [PATCH v2 1/2] qapi: Add feature flags to commands in qapi introspection Peter Krempa
2019-10-01 6:40 ` Markus Armbruster
2019-10-01 14:17 ` Peter Krempa
2019-10-01 20:01 ` Markus Armbruster
2019-10-02 6:15 ` Markus Armbruster
2019-09-20 14:26 ` [PATCH v2 2/2] qapi: Allow introspecting fix for savevm's cooperation with blockdev Peter Krempa
2019-10-01 19:34 ` Markus Armbruster
2019-10-01 21:07 ` Eric Blake
2019-10-02 11:57 ` Markus Armbruster
2019-10-10 15:07 ` Kevin Wolf
2019-10-11 6:08 ` Markus Armbruster
2019-10-11 9:00 ` Kevin Wolf
2019-10-11 11:10 ` Markus Armbruster [this message]
2019-09-30 13:04 ` [PATCH v2 0/2] qapi: Add detection for the 'savevm' fix for blockdev Peter Krempa
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