Re: [Dazuko-devel] dazukoFS - redirFS

[John Ogness]

Frantisek Hrbata wrote:
> You are absolutely right. The solution, as I introduced it, is for Linux
> kernels only, because it works directly with Linux VFS internals. It is
> intended to solve some Dazuko's problems on Linux kernels (for
> example ON-CLOSE events for Linux 2.6).
> I am not planning to port this to Solaris or FreeBSD. For these OS
> it will have to be completely rewritten.
>
> Actually at this moment I am waiting for some feedback and then we will
> see if this is a right way.
>
> I think, that processing overhead is not a problem, but the duplication of
> VFS objects could be. Please note, that for on-access scanning only some
> events like open, exec and close are needed. So, why to duplicate all VFS
> objects in the inode and dentry cache.

Hi Franta,

If we were go ahead with VFS object duplication, and you were to make it for 
Linux 2.6 only, how small could it be? I have looked around at lots of 
examples (including the code generated from FiST) and it seems like there is 
an enormous amount to keep track of. It also seems like there are a lot of 
behavior and structural changes from each kernel version.

But if you were to take the current 2.6 Linux kernel and specialize a 
solution (based on VFS object duplication), how small and clean could you 
make it?

I know that you have done a lot of investigation on this, so I consider you 
to be the best qualified to answer.

(I was quite impressed with how small and clean your redirfs was. I don't 
have any problems with the implementation. My problems stem from the general 
concept of "hacking" the VFS objects of other filesystems.)

A little bit of background information for everyone else: In February, 
Franta and I had a long discussion about how DazukoFS should be implemented. 
At that time I had really hoped that we could avoid VFS object duplication. 
But after seeing an actual implementation doing this (although the 
implementation itself was good), I have changed my mind. I think it is 
important that DazukoFS behaves like a real filesystem.

John Ogness

--
Dazuko Maintainer