[coyotos-dev] Impending changes to space bank

[Jonathan S. Shapiro]

On Wed, 2008-05-14 at 11:57 -0700, Charles Landau wrote:
> Jonathan S. Shapiro wrote:
> > I will be introducing a new operation. Given a bank B, this creates a
> > new sub-bank B' and transfers ownership of all storage associated with B
> > to B'. This is needed for initializer processes that wish to
> > self-destruct cleanly while leaving the object they initialized intact.
> 
> Is it possible to generalize this to two separate operations?
> - create a sub-bank
> - transfer ownership of all storage to a specified sub-bank

Three questions:

1. What happens to ownership transfer if, in the interim, a limit has
   been set on the sub-bank?

2. What happens to ownership of the Endpoint/RedSegNode that names the
   parent bank? In Coyotos, and I think EROS, this object is owned by
   the bank that it names, and so cannot be transferred in this way (in
   either implementation).

3. A generalized transfer operation could permit transfer *upwards*
   along the bank hierarchy, and might be called with a child bank whose
   permission set does not allow transfer of object ownership to parent
   on destruction (or there might be some intervening bank with this
   restriction in effect). What should happen in this case?

I suppose my feeling was that it was better to create the "boxcar"
version whose behavior seems clear to me than to try to sort out these
issues without the time to think them through.

Aside: note that "transfer" is not the same as "exchange ownership of
equal amounts of storage". Transfer operations can only occur upwards or
downwards along the bank hierarchy.


shap