Re: [PATCH 02/10] struct ref_transaction: add a place for backends to store data

> > This is just one pointer. Once we start layering ref backends (and
> > already we're moving towards a "files" layer which sits atop loose and
> > packed backends, right?), how do we avoid backends stomping on each
> > other (or worse, dereferencing somebody else's data as their own
> > struct)?
> 
> My conception is that layered backends would be separated as much as
> possible, and if the "top" layer needs to modify the "bottom" layer, it
> would do so via a separate reference transaction on the bottom layer.
> That transaction would be owned by the bottom layer, which would be able
> to use the corresponding `backend_data` pointers however it likes.
>
> You can see an example of this construct in patch 08.