Re: A question about UBIFS

[Artem Bityutskiy <Artem.Bityutskiy@nokia.com>]

Zhao Forrest wrote:
>> Zhao Forrest wrote:
>>> Hi Artem,
>>> I have a basic question about NAND flash page update in UBIFS/UBI,
>>> take the following as an example:
>>> 1 a NAND flash with page size of 4KB, erase block size of 256KB, so
>>> there're 64 pages within an erase block
>>> 2 page 0 - page 10 has invalid data content, page 11 - page 63 has
>>> valid data content from FS's point of view
>>> 3 UBIFS attempts to update(or rewrite) page 11
>>> My question is how page 11 is updated by UBIFS/UBI?
>>> I only read the design docs of UBI and guess that for this particular
>>> case a new physical eraseblock is got by UBI, then new content of page
>>> 11 is written to page 11 of new physical eraseblock, page 12 - page 63
>>> in original physical eraseblock are copied to new physical eraseblock,
>>> lastly the mapping between logical eraseblock and physical eraseblock
>>> is updated. Am I right?
>> Right. All updates are out-of-place.
>>
> So when only page 11 is rewritten, are pages 12-63 rewritten at the same time?
> Or page 11 is updated by wandering tree mechanism, and pages 12-63 are
> untouched?

The latter (12-63 are untouched).

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)