virtual filesystem ideas

[Alexander Larsson]

On Fri, 2003-09-19 at 22:53, Ken Deeter wrote:
> Hmm.. looks like my last message may have been too big..
> ---
> 
> Here's something I threw together. I too am very interested an seeing
> the writeups of the gnome-vfs and kio as I only know very high level
> things about them.
> 
> Attached is some kind of architecture diagram and some text describing
> various ideas in it. I guess its an elaboration on what I was saying
> yesterday. I've also inserted the text part below. If anything maybe the
> design goals part tries to sum up what we've talked about in this thread
> so far.

I don't like this proposal. All the message passing looks slow, due to
context switches and unnecessary work. The way observers are used seems
to mean every single vfs operation will end up with a whole bunch of
out-of-process messages back and forth. 

The way this is set up doesn't look much like a vfs to me, more like a
download manager of some sort, which you tell to download files in the
background. It mentions status dialogs and all sorts of things that
should happen on a higher level. VFS operations are on a much lower
level (read(), readdir(), write(), seek(), rename() etc) and if they
return an error it is only the app that knows what to do. (i.e. We don't
want status dialogs while reading a configuration file on statup.)
The proposal even mentions that the most important thing a vfs is for
(reading data) isn't really specified in the proposal.

It seems like the proposal is all about plumbing, and there is no
specifics about how vfs operations are supposed to work, or any mention
about the issues related to vfs implementations: asynchronity,
cancellation, performance, API, threads vs processes, hanging NFS
mounts, how uris look, filename encoding, how vfs backend chaining works
(i.e. reading the contents of a zip file from a smb mount), seekability,
streams, etc.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Alexander Larsson                                            Red Hat, Inc 
                   alexl at redhat.com    alla at lysator.liu.se 
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