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From: Herbert P÷tzl (herbert_at_13thfloor.at)
Date: Mon 11 Aug 2003 - 15:29:11 BST


On Mon, Aug 11, 2003 at 09:56:17AM +0200, Mark Lawrence wrote:
> On Sat, 9 Aug 2003, Herbert P÷tzl wrote:
>
> > > For this case, it might be useful that linking from any context to a file
> > > in a special context (say context 1) _is_ allowed, but invokes a
> > > copy-on-write function when the context attempts to write to the file.
> >
> > okay, so basically except from unification, which would/should
> > change the files back to context zero/one links to/from
> > another context should be considered not doable/accessible at
> > all. correct me if that's not what you meant.
>
> I don't quite understand your sentence here, so here is the long version
> of my meaning (:

I think I know why you didn't understand my sentence ;)

> 1. Cross-context linking is only possible from any context
> to files in context 1.

there is no such thing like 'cross-context' linking.
either the file changes the context or stays in its context,
and either is is allowed to make a link or not.

> 2. When using open(2) with O_TRUNC|O_CREAT|O_APPEND on a cross-context
> link, the link should be removed and the original file copied to the
> context file space. The file descriptor returned from the open(2) call
> should then point to this new file.

yes, this is copy on write, on file basis, which maybe
will be implemented, but not at this time, because there
are too many issues regarding this approach.

> How you do 2. is not a simple matter I guess. Some sort of userspace
> helper?

this could be a solution, keep on developing theories,
they will be very valuable later ...

> Cheers, Mark.
> --
> Mark Lawrence
> mark_at_holderbank.com


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