Re: reiser4 plugins

From: David Masover
Date: Wed Jun 22 2005 - 17:03:33 EST

Hash: SHA1

Horst von Brand wrote:
> Artem B. Bityuckiy <dedekind@xxxxxxxxx> wrote:
>>Markus TÃârnqvist wrote:
>>> and move the stuff to the VFS as needed or
>>>deemed necessary. And enable the pseudo interface, or at least
>>>set it in menuconfig and enable by default, it needs testing too.
> Then test it out of the standard tree...

Standard tree is actually a good place to test things. That's why there
are so many things there that say "EXPERIMENTAL", and so many of those
don't work. Some even refuse to compile.

>>atomic operations,
> What is atomic that isn't in the standard filesystems? How do you guarantee

We've been discussing this for quite awhile. In standard filesystems,
the only things that are atomic are metadata. If I rename a file and
crash, I'm guarenteed to either have renamed the file or not, and not be
caught halfway.

This does not apply to files. In fact, the only way to perform an
atomic write on a file, using the filesystem's atomicity, is to write a
new file, nuke the old one, and rename the new one on top of the old one.

What we want is to have programs that can write small changes to one
file or to many files, lump all those changes into a transaction, and
have the transaction either succeed or fail.

> it doesn't stop the system dead in its tracks waiting for some very long
> transaction to finish?

We've also discussed this. For one thing, if we can have transactions
in databases which don't stop the database dead in its tracks, why can't
we do it with filesystems?

But anyway, if you really want to know, ask someone else or read the
archives. I wasn't really paying attention except to remember that this
issue was resolved.

>> different kinds of stat data,
> Usefulness? Sounds like kernel bloat leading to userspace bloat and
> applications/users wondering what the heck goes on when they don't grok the
> particular stat format.

So you allow multiple stat formats. Bloat is not as big an issue here
as the bloat of existing systems which run on top of the FS and don't
cooperate. Gnome and KDE each have their own VFS, for instance.

>> fibretions, etc,
> ???

Low-level tweaking. I think the word is from some sort of calculus.

>>etc. Some thing is not yet ready - doesn't matter. Some of this is of
>>general interest, some is Reiser4-dedicated.
> I don't see anything that would interest me at least, so you can safely
> scratch the "general interest" part.

You're the sole general public?

>>New interfaces are needed to allow users to utilize that all.
> That is a quite strong argument /against/ it all in my book. It means bloat
> in /every/ filesystem, and they have shown to be able to do without for
> some 30 years now. I'd need /very/ strong reasons for adding something.

Spotlight on the Mac. Users love it. We can do it. But not without
changing something in the filesystem.

Actually, I think we came up with several ways to do this, all of which
required Reiser4 interfaces.

It's "bloat" until you need it.

>> My point
>>is that the things that are of general interest must not be
> Reiser4-only stuff is of very limited use, if it isn't just internal
> stuff. And that doesn't need any changes.

Only it does. Reiser4 can't get into the kernel because it duplicates
the VFS in order to extend it. It couldn't get in before because it
extended the VFS directly.

Maybe you just don't want this system to EVER get in, no matter what
they do to it?

>> For example, I should have a possibility to implement
>>files-like-dir in _another_ FS using the same interfaces that Reiser4
>>uses. That's all I wanted to say.
> It has been argued over and over that that particular feature /can't/ be
> implemented sanely anyway, so it has to stay out. Besides not making any

It's been dropped for the moment, but it's been argued just as many
times that it can be done sanely.

> sense. "You've got files and directories" is a bit asymetrical and so not
> quite nice; "all you have is directories" is symmetrical, estetic, and
> completely useless; "some files are directories, some aren't; files in
> file-directories are different than regular files in directory-directories"
> is just a mindless jumble.

Or you can just say "There are no files. There are no directories.
There are only objects, which contain a chunk of linear data and other

If you actually go read the whitepaper, you will discover that this is
actually a cleaner, more esthetic, and more useful model than the
current one. It's just a little harder to do.
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