Re: [Qemu-devel] [PATCH 1/3] block: Support streaming to an intermediate layer

[Alberto Garcia]

On Thu, Mar 05, 2015 at 03:04:25PM +0100, Kevin Wolf wrote:

> The bs parameter is now only used for the following things:
> 
> 1. As the default for top

Right.

> 2. For error handling: Any errors are reported for bs, even though
>    they are actually for top. Is this correct behaviour? It looks
>    questionable to me.

Hmm... I guess you mean when calling block_job_error_action(), I
probably overlooked that.

> 3. As the BDS that owns the job
> 
> My question is whether we can't simply call stream_start() with an
> intermediate node as bs instead of introducing a new parameter. I'm
> not completely sure about the consequences of 3., i.e. moving
> ownership of a block job to some BDS somewhere down the chain, but
> otherwise it should be possible and seems cleaner.

We can, that was actually the first thing I tried and it does work,
but then I noticed that other parts of the code would need changes,
e.g. qmp_query_block_jobs() must be modified to iterate over all nodes
of each device.

Since I was also not sure about the consequences of such a change I
opted for the conservative approach.

Berto