Subject: Re: UDF integration / syscall
To: None <>
From: Reinoud Zandijk <>
List: tech-kern
Date: 06/08/2003 22:54:10
Dear folks,

On Sun, Jun 08, 2003 at 06:07:18PM +0200, Reinoud Zandijk wrote:
> Dear folks and fellow developers,
> As some of you might have read allready, i am working on implementing the
> UDF filingsystem both as a userland tool and hopefully one day also as a
> kernel filingsystem. The userland tool is getting near completion for
> read-only and getting some infrastructure for writing support too. The
> kernel part however still needs to be done from scratch. I hope to be able
> to recycle as much from the userland tool as possible but i'll have to see.

After some questions in private i'll try to explain some more details about
UDF. UDF is an Ecma-167 derived filingsystem endorsed by the optical
storage society OSTA and used as native format for DVD's.

An UDF filingsystem is like a book-library. You have a series of physical
volumes that together form a serie and are called `volumesets' in UDF. The
phyical volumes analog to the seperate books of the series are called
`primary volumes' in UDF. Such a primary volume can have logical volumes
(like chapters) that can be considered mounting mounts since they have a
directory tree associated with each of them. A logical volume space is
consisted of one of more disc partitions that dont have to be on the same
phyical disc; so a logical volume space can be grown by just adding another
partition to the logical volume.

My idea is thus to not only support the `one volumeset with one primary
volume with one logical volume with just one partion' like allmost all
current UDF filingsystem implementations limit themselves to but to go for
the most extensive set of features possible.

The userland client is allready capable of reading such extensive sets 
without any problems.... the kernel implementation doesnt have to be much 
different if i can can just `merge' the discs together by just adding them 
to the set of discs known. A `disc' doesnt need to be a whole disc but can 
easily be a partition within a disclabel or a cd-rom session or even a 
normal regular file!

Hope this additional info helps :)