Some JFFS3 feedback

Some JFFS3 feedback

[Charles Manning]

Hi Artem

I briefly read the JFFS3 doc, and will read it more. It has some very 
interesting ideas in it.

About 9 years back, I did some flash file system patent research and IIRC one 
of the patents covered something very similar to the Wandering Tree approach 
to addressing the write-in-place problem, so there might be some IP issues 
with this. I shall have a scratch around to see if I can find it (though 
finding something in a 20+ year old paper mountain is a challenge).

I will be interested to see how you tackle the dreaded garbage collection. 
IMHO, GC is something that needs to be considered sooner rather than later 
because it is key to sustained write performance.

I know that it is hard to change a name, but JFFS3 is really not much like 
JFFS2 or JFFS in design, so keeping a similar name really gets confusing 
later on (I get enough problems with yaffs and yaffs2 and they share 90% of 
the code). I would suggest a name change to avoid confusion down the track.

Regards

-- Charles

Re: Some JFFS3 feedback

[Artem B. Bityutskiy]

Hello Charles,

Charles Manning wrote:
> I briefly read the JFFS3 doc, and will read it more. It has some very 
> interesting ideas in it.
thanks for your feedback.

> About 9 years back, I did some flash file system patent research and IIRC one 
> of the patents covered something very similar to the Wandering Tree approach 
> to addressing the write-in-place problem, so there might be some IP issues 
> with this. I shall have a scratch around to see if I can find it (though 
> finding something in a 20+ year old paper mountain is a challenge).
Hmm, it is interesting. We would be very appreciated if you provide some 
information.

> I will be interested to see how you tackle the dreaded garbage collection. 
> IMHO, GC is something that needs to be considered sooner rather than later 
> because it is key to sustained write performance.
Absolutely. Me and my workmate in OktetLabs are thinking on this. At the 
moment we're considering 2 approaches. It seems there are no fundamental 
problems, but it needs more thinking, analisys and evaluation. We're 
even going to  create a user-level prototype to see how well (and fast) 
will GC work. Only after I have a clear picture in my mind I'm able to 
put it clearly in the paper.

But we anyway are not going to start implementation befor we've designed GC.

> I know that it is hard to change a name, but JFFS3 is really not much like 
> JFFS2 or JFFS in design, so keeping a similar name really gets confusing 
> later on (I get enough problems with yaffs and yaffs2 and they share 90% of 
> the code). I would suggest a name change to avoid confusion down the track.
Hmm, frankly, I think we may consider JFFS3 as an JFFS2's descendant. 
Yes, the code is probably going to be completely different. But try to 
glance to JFFS3 like this: it is just JFFS2 + on-flash indexing. JFFS2 
keeps indexing in RAM, we are going to keep it on Flash. Glance at 
figure 5 here: 
http://www.linux-mtd.infradead.org/tech/JFFS3design/node8.html.

But if there are some other good names and people are really bothered by 
the JFFS3 name - we might rename it as well.

-- 
Best Regards,
Artem B. Bityutskiy,
St.-Petersburg, Russia.

Re: Some JFFS3 feedback

[Jörn Engel]

On Wed, 16 November 2005 17:02:12 +0300, Artem B. Bityutskiy wrote:
> Charles Manning wrote:
> 
> >About 9 years back, I did some flash file system patent research and IIRC 
> >one of the patents covered something very similar to the Wandering Tree 
> >approach to addressing the write-in-place problem, so there might be some 
> >IP issues with this. I shall have a scratch around to see if I can find it 
> >(though finding something in a 20+ year old paper mountain is a challenge).
>
> Hmm, it is interesting. We would be very appreciated if you provide some 
> information.

Definitely.  If there is a patent on this, we need to do the usual
dance to find some prior art and either invalidate the patent or make
it specific enough to be trivially avoided.

Jörn

-- 
Ninety percent of everything is crap.
-- Sturgeon's Law

Re: Some JFFS3 feedback

[Charles Manning]

On Thursday 17 November 2005 06:06, Jörn Engel wrote:
> On Wed, 16 November 2005 17:02:12 +0300, Artem B. Bityutskiy wrote:
> > Charles Manning wrote:
> > >About 9 years back, I did some flash file system patent research and
> > > IIRC one of the patents covered something very similar to the Wandering
> > > Tree approach to addressing the write-in-place problem, so there might
> > > be some IP issues with this. I shall have a scratch around to see if I
> > > can find it (though finding something in a 20+ year old paper mountain
> > > is a challenge).
> >
> > Hmm, it is interesting. We would be very appreciated if you provide some
> > information.
>
> Definitely.  If there is a patent on this, we need to do the usual
> dance to find some prior art and either invalidate the patent or make
> it specific enough to be trivially avoided.

I had a bit of a scratch through stuff and could not find any patent on 
wandering trees, but I am pretty sure I have seen this in a paper somewhere. 
So, inconclusive as to whether it is patented or not.

One bloke that I will ping is Sivan Toledo (http://www.cs.tau.ac.il/~stoledo/) 
who has done heaps of research into FFSs. 

-- Charles

Re: Some JFFS3 feedback

[Charles Manning]

On Thursday 17 November 2005 06:06, Jörn Engel wrote:
> On Wed, 16 November 2005 17:02:12 +0300, Artem B. Bityutskiy wrote:
> > Charles Manning wrote:
> > >About 9 years back, I did some flash file system patent research and
> > > IIRC one of the patents covered something very similar to the Wandering
> > > Tree approach to addressing the write-in-place problem, so there might
> > > be some IP issues with this. I shall have a scratch around to see if I
> > > can find it (though finding something in a 20+ year old paper mountain
> > > is a challenge).
> >
> > Hmm, it is interesting. We would be very appreciated if you provide some
> > information.
>
> Definitely.  If there is a patent on this, we need to do the usual
> dance to find some prior art and either invalidate the patent or make
> it specific enough to be trivially avoided.

I have discussed this with others and there would appear to be some closeness 
to WAFL. This has been discussed copiously in the context of ReiserFS and 
prior art has been established.

Short answer: it should not be a problem.

#discalimer I'm not a lawyer and all that.

-- CHarles

Re: Some JFFS3 feedback

[Jörn Engel]

On Tue, 22 November 2005 19:21:17 +1300, Charles Manning wrote:
> 
> I have discussed this with others and there would appear to be some closeness 
> to WAFL. This has been discussed copiously in the context of ReiserFS and 
> prior art has been established.
> 
> Short answer: it should not be a problem.

Good news.  Thanks, Charles.

> #discalimer I'm not a lawyer and all that.

Since even lawyers will always add disclaimers ("by our
interpretation", etc), this is good enough for me.

Jörn

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