Reiser4 & Files/Directories question

Reiser4 & Files/Directories question

[Ross Jekel]

Newbie question as I'm evaluating Reiser4 as a storage solution for a 
project I'm working on.

It appears Reiser4 has the ability to have a file name be both the name 
for the file data and a directory. Can I take advantage of this at the 
application level?

For instance, can I use python to access the file data directly, and 
access the directory information as well to open any attribute files I 
might want to put in there? Or is that functionality only available 
through non-posix calls from file system plugins and such.

I was interested in the design of the livingxml.net solution from the 
testimonials page, but that site is no longer available. Is there a 
project or design document somewhere that summarizes the best way of 
using reiser4 as a database of content with additional metadata for each 
document?

Forgive me if this is answered somewhere. I've searched some mailing 
list archives site and couldn't find the exact answer.

Thanks,
Ross

Re: Reiser4 & Files/Directories question

[David Masover]

Ross Jekel wrote:
> Newbie question as I'm evaluating Reiser4 as a storage solution for a 
> project I'm working on.
> 
> It appears Reiser4 has the ability to have a file name be both the name 
> for the file data and a directory. Can I take advantage of this at the 
> application level?

I think there's a mount option to turn this behavior back on, but it's 
not on at the moment due to HUGE flamefests on the kernel lists.  We 
don't know if it's coming back anytime soon, or if it'll resemble what 
you're thinking when it does.

For now, I think there might still be a '-o metas' option, or something 
similar.

> For instance, can I use python to access the file data directly, and 
> access the directory information as well to open any attribute files I 
> might want to put in there? Or is that functionality only available 
> through non-posix calls from file system plugins and such.

It will eventually be available through a non-posix call, and maybe 
(hopefully, you paying attention, Namesys?) in some limited way from the 
xattr calls.

> I was interested in the design of the livingxml.net solution from the 
> testimonials page, but that site is no longer available. Is there a 
> project or design document somewhere that summarizes the best way of 
> using reiser4 as a database of content with additional metadata for each 
> document?

AFAIK, livingxml was based on reiserfs3, and it had nothing to do with 
non-standard extensions to the FS, but rather with the fact that v3 (and 
v4) is fast with small text files, making it a good choice for web, 
email, XML, or anything else small and text-y.  Even more so after we 
get the compression plugin.

> Forgive me if this is answered somewhere. I've searched some mailing 
> list archives site and couldn't find the exact answer.

Maybe not, but if you search the archive for "Silent Semantic Changes in 
Reiser4"  (or something very similar), you'll find a very long thread on 
why Reiser4 doesn't (currently) support files as directories.

Re: Reiser4 & Files/Directories question

[Jake Maciejewski]

On Thu, 2005-09-08 at 13:53 -0500, David Masover wrote:
> Ross Jekel wrote:
> > Newbie question as I'm evaluating Reiser4 as a storage solution for a 
> > project I'm working on.
> > 
> > It appears Reiser4 has the ability to have a file name be both the name 
> > for the file data and a directory. Can I take advantage of this at the 
> > application level?
> 
> I think there's a mount option to turn this behavior back on, but it's 
> not on at the moment due to HUGE flamefests on the kernel lists.  We 
> don't know if it's coming back anytime soon, or if it'll resemble what 
> you're thinking when it does.
> 
> For now, I think there might still be a '-o metas' option, or something 
> similar.

I don't know about mount options, but I've enabled metas by changing
"#define ENABLE_REISER4_PSEUDO (0)" to "#define ENABLE_REISER4_PSEUDO
(1)" in fs/reiser4/reiser4.h

> > For instance, can I use python to access the file data directly, and 
> > access the directory information as well to open any attribute files I 
> > might want to put in there? Or is that functionality only available 
> > through non-posix calls from file system plugins and such.
> 
> It will eventually be available through a non-posix call, and maybe 
> (hopefully, you paying attention, Namesys?) in some limited way from the 
> xattr calls.
> 
> > I was interested in the design of the livingxml.net solution from the 
> > testimonials page, but that site is no longer available. Is there a 
> > project or design document somewhere that summarizes the best way of 
> > using reiser4 as a database of content with additional metadata for each 
> > document?
> 
> AFAIK, livingxml was based on reiserfs3, and it had nothing to do with 
> non-standard extensions to the FS, but rather with the fact that v3 (and 
> v4) is fast with small text files, making it a good choice for web, 
> email, XML, or anything else small and text-y.  Even more so after we 
> get the compression plugin.
> 
> > Forgive me if this is answered somewhere. I've searched some mailing 
> > list archives site and couldn't find the exact answer.
> 
> Maybe not, but if you search the archive for "Silent Semantic Changes in 
> Reiser4"  (or something very similar), you'll find a very long thread on 
> why Reiser4 doesn't (currently) support files as directories.
> 
-- 
Jake Maciejewski <maciejej@msoe.edu>