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Re: [Qemu-devel] [RFC] Intermediate block mirroring
From: |
Alberto Garcia |
Subject: |
Re: [Qemu-devel] [RFC] Intermediate block mirroring |
Date: |
Wed, 25 Apr 2018 14:58:54 +0200 |
User-agent: |
Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) |
On Fri 20 Apr 2018 03:13:49 PM CEST, Max Reitz wrote:
>>>>>> One other way is to have a more generic replace-node command
>>>>>> which would call bdrv_replace_node(), but I don't know if we want
>>>>>> to expose that and I don't have any other use case for it at the
>>>>>> moment.
>>>>>
>>>>> I think we do want to expose that. As far as I'm informed, for
>>>>> graph manipulation we want a command that can replace nodes
>>>>> (including replacing nothing by a new node or replacing an
>>>>> existing node by nothing, if the parent supports that).
>>>>
>>>> Was there any discussion about this in the mailing list? (proposed
>>>> name for this function, features, etc.)
>>>
>>> Well, there is x-blockdev-change. But we probably want to expose
>>> bdrv_reopen() in the long run.
>>
>> Exposing bdrv_reopen() itself shouldn't be too much work (it takes
>> just two node names, or am I missing something?).
I just realized that I meant "Exposing bdrv_replace_node()" here.
> So from my perspective... If you think it's easy, why don't you try
> it and then we'll see? *cough*
I'm doing it :-)
>> There's still the question of how to update the backing file string
>> (on the overlay). stream and commit do it automatically, but if we do
>> bdrv_reopen() or the aforementioned modification to blockdev-mirror
bdrv_replace_node() again
>> we'd need to do it explicitly with change-backing-file, or extend the
>> API to allow for that.
>
> Well, the December notes do say that we probably want an option to
> specify the target's filename which is what will be written into the
> overlays of @to_replace as their backing file string, so I think
> extending the API should be fine.
Yes, but how do you find out what the overlays are (without an
additional parameter, that is)? I thought we didn't want to support
walking the backing chain in reverse direction.
Berto
- [Qemu-devel] [RFC] Intermediate block mirroring, Alberto Garcia, 2018/04/12
- Re: [Qemu-devel] [RFC] Intermediate block mirroring, Max Reitz, 2018/04/13
- Re: [Qemu-devel] [RFC] Intermediate block mirroring, Alberto Garcia, 2018/04/16
- Re: [Qemu-devel] [RFC] Intermediate block mirroring, Max Reitz, 2018/04/16
- Re: [Qemu-devel] [RFC] Intermediate block mirroring, Alberto Garcia, 2018/04/18
- Re: [Qemu-devel] [RFC] Intermediate block mirroring, Max Reitz, 2018/04/20
- Re: [Qemu-devel] [RFC] Intermediate block mirroring,
Alberto Garcia <=
- Re: [Qemu-devel] [RFC] Intermediate block mirroring, Max Reitz, 2018/04/25
- Re: [Qemu-devel] [RFC] Intermediate block mirroring, Alberto Garcia, 2018/04/25
- Re: [Qemu-devel] [RFC] Intermediate block mirroring, Max Reitz, 2018/04/25