Some thoughts about JFFS3 design doc

Some thoughts about JFFS3 design doc

[zhao, forrest]

Hi, Artem

I read through your JFFS3 design doc and had some thoughts

1 in Section 4.1->4, there's a typo:
direntries contain {xattr name =>xattr ID}......

2 in section 3.6, I think it's better if you could
give a description or an example of how to replay
the journal to build the journal tree in RAM and
recover the inconsistent meta data on flash.

3 In section 4, I think it's better if you could
give a description or an example of what happens
for an update operation. Such as what happens when
a write operation update offset from 100 to 200 for
a file of length 400 bytes. I guess maybe you are
working on this now :)

4 I think your design doc is well-organized and give
reader a very clear picture and illustration of the
JFFS3 design.

Thanks,
Forrest

Re: Some thoughts about JFFS3 design doc

[Artem B. Bityutskiy]

zhao, forrest wrote:
> Hi, Artem
> 
> I read through your JFFS3 design doc and had some thoughts
I'm flattered you're reading my writings :-)

> 1 in Section 4.1->4, there's a typo:
> direntries contain {xattr name =>xattr ID}......
Oh, thanks.

> 2 in section 3.6, I think it's better if you could
> give a description or an example of how to replay
> the journal to build the journal tree in RAM and
> recover the inconsistent meta data on flash.
Yes, there is supposed a distinct big chapter related to this topic. I 
just have not had time to write it so far.

> 3 In section 4, I think it's better if you could
> give a description or an example of what happens
> for an update operation. Such as what happens when
> a write operation update offset from 100 to 200 for
> a file of length 400 bytes. I guess maybe you are
> working on this now :)
Nothing interesting - the new node just goes to the journal and the old 
one is considered obsolete.

I'm planning to add a distinct chapter with description of 
JFFS3-in0action where this will be described. Thanks for the note.

> 4 I think your design doc is well-organized and give
> reader a very clear picture and illustration of the
> JFFS3 design.
Thanks, the only really major missing thing is Garbage Collection. Will 
describe it as soon as I completely design it.

Feel free to send any comments, and even patches - the design sources 
are in MTD CVS (Documentation/mtd/).

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