Re: [Qemu-devel] [PATCH v2 03/10] block: Remove child references from bs->{options, explicit_options}

[Max Reitz <mreitz@redhat.com>]

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On 2018-09-03 16:34, Alberto Garcia wrote:
> Block drivers allow opening their children using a reference to an
> existing BlockDriverState. These references remain stored in the
> 'options' and 'explicit_options' QDicts, but we don't need to keep
> them once everything is open.
> 
> What is more important, these values can become wrong if the children
> change:
> 
>     $ qemu-img create -f qcow2 hd0.qcow2 10M
>     $ qemu-img create -f qcow2 hd1.qcow2 10M
>     $ qemu-img create -f qcow2 hd2.qcow2 10M
>     $ $QEMU -drive if=none,file=hd0.qcow2,node-name=hd0 \
>             -drive if=none,file=hd1.qcow2,node-name=hd1,backing=hd0 \
>             -drive file=hd2.qcow2,node-name=hd2,backing=hd1
> 
> After this hd2 has hd1 as its backing file. Now let's remove it using
> block_stream:
> 
>     (qemu) block_stream hd2 0 hd0.qcow2
> 
> Now hd0 is the backing file of hd2, but hd2's options QDicts still
> contain backing=hd1.
> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
>  block.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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