UBIFS recovery fails

[Jean-Sébastien Gagnon]

>> The situation you described should be already handled correctly by UBIFS, if the nand driver is correctly reporting pages with bitflips with the -EUNCLEAN.  In this case, UBI will move the PEB to a new one as soon as possible to avoid this problem.

> This would be true, if you could assume that a page reading failure always
> occurs after a previous read on the same page reports an ecc correction.
> But this is not the case: we had several unstable pages going from 0 bitflips
> (perfect read) to 2 bitflips (failed read). No way to detect any failure, no
> way to scrub data before it's too late.
> And the answer from the manufacturer was: you should not use any partially
> programmed/erased pages anyway, those should be cleaned up after recovering
> from a power failure.

This should not append if you use recommended ECC bits count defined by the NAND part. 
Can you verify that, because 1 bit ECC for each 512 byte is only recommended by older 
SLC flash which are pretty stable.  Newer NAND need more ECC bits, which can be 
addressed by using BCH parities.

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J-S