Re: [Qemu-devel] [PATCH v6 for 2.1 08/10] block: add backing-file option to block-stream

[Stefan Hajnoczi]

On Tue, Jun 17, 2014 at 05:53:56PM -0400, Jeff Cody wrote:
> On some image chains, QEMU may not always be able to resolve the
> filenames properly, when updating the backing file of an image
> after a block job.
> 
> For instance, certain relative pathnames may fail, or drives may
> have been specified originally by file descriptor (e.g. /dev/fd/???),
> or a relative protocol pathname may have been used.
> 
> In these instances, QEMU may lack the information to be able to make
> the correct choice, but the user or management layer most likely does
> have that knowledge.
> 
> With this extension to the block-stream api, the user is able to change
> the backing file of the active layer as part of the block-stream
> operation.
> 
> This allows the change to be 'safe', in the sense that if the attempt
> to write the active image metadata fails, then the block-stream
> operation returns failure, without disrupting the guest.
> 
> If a backing file string is not specified in the command, the backing
> file string to use is determined in the same manner as it was
> previously.
> 
> Reviewed-by: Eric Blake <address@hidden>
> Signed-off-by: Jeff Cody <address@hidden>
> ---
>  block/stream.c       | 11 +++++------
>  blockdev.c           | 12 ++++++++++++
>  hmp.c                |  3 ++-
>  qapi/block-core.json | 18 +++++++++++++++++-
>  qmp-commands.hx      |  2 +-
>  5 files changed, 37 insertions(+), 9 deletions(-)

Reviewed-by: Stefan Hajnoczi <address@hidden>

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