Re: [Qemu-block] [PATCH 1/2] iotests: 030 TestParallelOps non-shared base node

[Alberto Garcia]

On Wed 20 Mar 2019 10:35:27 AM CET, Vladimir Sementsov-Ogievskiy wrote:
>> Maybe at least this kind of freezing isn't the right tool for block
>> jobs, after all.
>
> I think, the correct way, which will support these correct cases
> (which however don't look like real use cases) is removing base from
> stream view. Stream should operate instead using bottom-node.

What is bottom-node?

> And this all looks really more complicated than what we already have
> with frozen backing chain.
>
> Do we really need such cases with parallel streams, sharing same node
> as base for one and top for another? Will someone be upset if we drop
> usage for such scenarios?

That would mean that 'base' is blocked and therefore cannot be used by a
different block job.

I don't think it's terrible to restrict that scenario, although it's
technically a regression so someone could complain about it. As I said
ealier I would prefer not to do it if there's a simple solution (we
would need to think about it), but I wouldn't want to make the code more
complicated just for this use case.

Berto