Re: silent semantic changes with reiser4

Bernd Petrovitsch
2004-08-26T11:11:43Z

[ shortened Cc: of reiser- and other folks since it is no longer
reiser-specific - sorry, if it was too much ]
[ fixed missing attribution ]

On Thu, 2004-08-26 at 12:51 +0200, Spam wrote:
> On Thu, 2004-08-26 at 03:24 -0700, Andrew Morton wrote:
> > Spam <spam@tnonline.net> wrote:
[...]
> >> Applications that support the new features will benefit, all others
> >> will continue to work without destroying data.
>
> > Sorry, but that all sounds a bit fluffy. Please provide some examples.

It is too fluffy.

> We already had the examples with cp and mv. Both should continue to
> work and the files will still be copied. The same with Konqueror and

... after they are patched to support streams. As stated each stream has
an own fd, so - from the user-space perspective - one has to open *all*
streams of this file, read them and write them into the destination.

> Nautilus. Files and their meta-files/streams/attributes will be
> retained as long as applications are using the OS API.

The OS-API is *one* file descriptor where you can read, write, mmap, ...
on. Therefore stream selection must happen with open() since open()
returns a fd (which uniquely identify a stream). Voila.
And actually this makes transition actually possible: Old apps simply
ignore streams (yes, there will be a default stream, which is used id
nothing else is specified) and throw them away (think of e.g. patch
which opens a new file, writes into it, unlink's the old one and mv's
the new one on the old place) until they are modified to support them.

Bernd
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