GSoC proposition: multiplatform UFS2 driver

[Richard Yao]

On 03/13/2014 06:29 PM, Richard Yao wrote:
> On 03/13/2014 06:12 PM, Julio Merino wrote:
>> On Fri, Mar 14, 2014 at 2:48 AM, Richard Yao <ryao at gentoo.org> wrote:
>>> On 03/12/2014 12:54 PM, CeDeROM wrote:
>>>> My proposition is to create universal UFS2 driver that would work on
>>>> Windows, Linux, and maybe other OS, so we can use native UFS2 as data
>>>> partition among various OS.
>>>>
>>>
>>> I like this idea. In particular, I would like to have UFS2 SU+J
>>> available for use in certain Linux VMs and was thinking about this
>>> possibility earlier in the week. However, I no longer qualify to be a
>>> GSoC student and I do not have time to do it myself.
>>> [...]
>>> Speaking as a kernel filesystem hacker (with most of my experience in
>>> Linux), I think this could be too ambitious depending on how you add
>>> detail. In particular, Linux has a moving target of a VFS (which causes
>>> much pain) and Windows' IFS is very different from the SunOS VFS that
>>> has become the basis for implementing multiple filesystems on different
>>> UNIX implementations and copy-cats.
>> [...]
>>
>> Something worth pointing out here: in NetBSD, and thanks to rump, you
>> can already get the *verbatim* in-kernel code of UFS2 built on a
>> variety of host platforms. You could very easily turn the existing
>> file system code into a FUSE file-system for Linux, for example, or
>> write the necessary shims to bundle the code into a kernel driver.
> 
> This would work, but I think it dramatically reduces the value of the
> result.
> 
>> In other words and in my opinion: rewriting file system code from
>> scratch is outside of the scope of GSoC, but writing the glue code for
>> the above to happen doesn't sound too crazy. (The only problem may be
>> if NetBSD's UFS2 driver is not compatible with FreeBSD's... but I
>> believe they should be for the "basic stuff".)
>>
>> Some links:
>>
>> https://github.com/rumpkernel/buildrump.sh
>> http://wiki.netbsd.org/rumpkernel/
>>
> 
> There is no need to write the code from scratch. He would just need to
> take the existing code and wrap it so that it builds as part of a kernel
> module for other kernels. The only things that need to be written is
> glue code for mapping *BSD interfaces to foreign ones. I do not think it
> is much more complex than writing a FUSE filesystem driver, especially
> given the existence of user-mode Linux. That would permit the filesystem
> driver for Linux to be developed in userland on FreeBSD, much like a
> FUSE driver. Once the wrapper is written, the things that need revision
> to support other kernels should be rather clearly defined.
> 
> http://user-mode-linux.sourceforge.net/
> 
> That being said, I do not like the idea of using NetBSD's UFS2 code. It
> lacks Soft-Updates, which I consider to make FreeBSD UFS2 second only to
> ZFS in desirability.
> 

Something worth pointing out here that I missed is that rump could be
used to develop a port of FreeBSD UFS2 to NetBSD. ;)

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