A question about UBIFS

Zhao Forrest forrest.zhao at gmail.com
Wed Jun 11 00:16:12 EDT 2008

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?
I know I omit many details in UBIFS/UBI for this updating operation.
I'd like to know the cost of rewrite in UBIFS/UBI.


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