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From: "Denis V. Lunev" <den@openvz.org>
Message-ID: <570F355E.1080603@openvz.org>
Date: Thu, 14 Apr 2016 09:14:54 +0300
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Subject: Re: [Qemu-devel] [PATCH for-2.7 00/15] block: Lock images when
 opening
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To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org, Kevin Wolf <kwolf@redhat.com>, Max Reitz <mreitz@redhat.com>, Jeff Cody <jcody@redhat.com>, Markus Armbruster <armbru@redhat.com>, Eric Blake <eblake@redhat.com>, John Snow <jsnow@redhat.com>, qemu-block@nongnu.org, berrange@redhat.com, pbonzini@redhat.com

On 04/14/2016 08:46 AM, Fam Zheng wrote:
> On Thu, 04/14 08:04, Denis V. Lunev wrote:
>> unfortunately no. If the lock will be on the image file,
>> we will have get it on the target node on QEMU start
>> and re-acquire it in bdrv_invalidate_cache.
>>
>>  From my POW you should not get the lock if
>> BDRV_O_INACTIVE is set.
> That is what I meant. :)
>
> At source: Images are unlocked in bdrv_inactivate().
>
> At destinition: Images are not locked if opened with BDRV_O_INACTIVE, and
> are locked in bdrv_invalidate_cache() (at the INMIGRATE -> RUNNING switch).
>
> Fam
it looks I have missed something. The above will work, but
I do not see clause where you set BDRV_O_NOLOCK when BDRV_O_INACTIVE
is set.

Do you mean that we will not reach bdrv_open_common with this flag
set?

Den