Re: silent semantic changes with reiser4

Alex Zarochentsev
2004-08-30T18:10:54Z

On Thu, Aug 26, 2004 at 05:53:51PM +0100, Jamie Lokier wrote:
> Rik van Riel wrote:
> > And if an unaware application reads the compound file
> > and then writes it out again, does the filesystem
> > interpret the contents and create the other streams ?
>
> Yes, exactly that. The streams are created on demand of course, and
> by userspace helpers when that's appropriate which I suspect it almost
> always is.
>
> > Unless I overlook something (please tell me what), the
> > scheme just proposed requires filesystems to look at
> > the content of files that is being written out, in
> > order to make the streams work.
>
> Yes. Hence the idea of coherent views between two files: writing to
> one affects the content of the other, although the calcalation is only
> done on demand (or when the fs wants to migrate the representation --
> for example, creating the flat container prior to deleting the
> regeneratable pieces in order to save space).
>
> I haven't seen anything from Namesys that says they'll do that. I
> have the impression the streams are just generated in memory on the
> fly, not stored on disk with a cacheing policy, but that's just an
> impression. (We've all seen the Namesys white papers, they're not
> _that_ revealing). :)

would it be a tautology if I say that the streams implementation depends on
(reiser4 now, may be vfs later) plugins? All proposals including user-level
helpers, shadow caching/indexing may be implemented, why not?

> I'm just pointing out how to do it _right_. I think it will turn out
> like this eventually, either next year or some time over the next
> decade after some iterations. Inevitable. Mark my words, etc. :)
>
> -- Jamie

--
Alex.