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Re: [Qemu-devel] [PATCH 2/3] block: Add QMP support for streaming to an
From: |
Alberto Garcia |
Subject: |
Re: [Qemu-devel] [PATCH 2/3] block: Add QMP support for streaming to an intermediate layer |
Date: |
Thu, 5 Mar 2015 16:12:03 +0100 |
User-agent: |
Mutt/1.5.20 (2009-06-14) |
On Thu, Mar 05, 2015 at 03:09:58PM +0100, Kevin Wolf wrote:
> > { 'command': 'block-stream',
> > - 'data': { 'device': 'str', '*base': 'str', '*backing-file': 'str',
> > - '*speed': 'int', '*on-error': 'BlockdevOnError' } }
> > + 'data': { 'device': 'str', '*base': 'str', '*top': 'str',
> > + '*backing-file': 'str', '*speed': 'int',
> > + '*on-error': 'BlockdevOnError' } }
> A better interface would probably be to allow node names for
> 'device' and leave everything else as it is.
That's possible, but if the API is the same how does libvirt know if
streaming to an intermediate node is possible or not?
> There is no point in specifying some root node as 'device' that
> isn't actually involved in the operation; worse, it isn't even
> possible in the general case because 'top' could have multiple
> users/parents.
The latter is actually a good point, if 'top' is used by 2+ parents
then it makes sense that the ownership of the block job in in 'top',
not in the root node.
I think I will need to investigate the consequences of that.
Berto