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Date: Tue, 8 Nov 2016 12:05:50 +0100
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] BdrvDirtyBitmap and bdrv_snapshot_goto
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To: Max Reitz <mreitz@redhat.com>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>, qemu-devel <qemu-devel@nongnu.org>, qemu block <qemu-block@nongnu.org>, Fam Zheng <famz@redhat.com>, "Denis V. Lunev" <den@openvz.org>, John Snow <jsnow@redhat.com>


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Am 07.11.2016 um 17:10 hat Max Reitz geschrieben:
> On 07.11.2016 16:24, Vladimir Sementsov-Ogievskiy wrote:
> > Hi all!
> >=20
> > As I can see, in bdrv_snapshot_goto, existing dirty bitmaps are not
> > handled.. Is it ok? Should not they be filled with ones or something
> > like this?
>=20
> Filling them with ones makes sense to me. I guess nobody noticed because
> nobody was crazy enough to use block jobs alongside loadvm...

What's the use case in which ones make sense?

It rather seems to me that an active dirty bitmap and snapshot switching
should exclude each other because the bitmap becomes meaningless by the
switch. And chances are that after switching a snapshot you don't want
to "incrementally" backup everything, but that you should access a
different backup.

Kevin

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