Re: "Why Reuser 4 still is not in" doc

From: Al Boldi
Date: Mon Jul 17 2006 - 07:22:29 EST

Jan Engelhardt wrote:
> >> > (aside from the VFS integration debate)
> >>
> >> Anybody know what's in Reiser4 that VFS doesn't like (link please)?
> >
> > Reiser4 plug-ins have (had?) the ability to alter the semantics of
> > things, like making files into directories inside
> Yes, it changes the semantics. Suddenly you can "cd linux-2.6.17.tar.bz2".
> But what will stat() return? S_IFDIR? S_IFREG? S_IFANY? A .tar parser in
> kernelspace is almost never the right thing. And then a cpio parser,
> because that's what initramfs'es are made of. Not to forget .zip, because
> that's omnipresent. Oh of course we'd also need bzip2 and gzip decoder.
> BASE64 and UU anyone?

Using this as an argument against plug-ins is a bit strange. I suppose
somebody could go overboard and use plug-ins to implement a subKernel.
Would this then imply that plug-ins are wrong?

> > which you could see meta-files like
> > file/uid and file/size which contained meta-data and such accessible as
> > normal files to all the unix tools (which is a very good idea IMO). You
> > could get things like chmod by just 'echo root
> >
> >> file/owner' or something, very nice.
> I wish you a lot of fun with users in LDAP or other exotic storage
> methods. By making Everything possible through echo, you are violating the
> unix philosophy that one tool should do one thing (though echo does just
> that).

The unix philosophy would hold with plug-ins, as this would aid flexibility.
Using plug-ins is a form of modularization, much like the 'one tool should
do one thing' approach.

> And in this case, echo would be chown, chmod, tar, bzip2 all at
> once. This sounds familiar, I think I have seen this with explorer.exe
> (and its uncountable DLLs), which lets you change everything within the
> same window.

Nothing wrong with that, unless you have an allergy against explorer.

> What I think is promising are the compression/encryption plugins. ext2
> and 3 had an attribute (`lsattr`) for compression but it does not seem
> like ever implemented.

Now that's a great example for using a plug-in in the wright place.

> > This was frowned upon by kernel developers who felt that it belonged in
> > the kernel VFS (if at all), rather than in reiser4 directly.

This is really the crux of the issue. Introducing plug-ins into the FS is
really the wrong place, when we already have an abstracted VFS that allows
this to be fanned out to its children.



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