On Wednesday 14 February 2007 18:49, Blair Barnett wrote:
> We're experiencing what appear to be file system corruption
> due to power fail. I just got done looking at a nanddump of a
> yaffs2 file system that looks like the block header (first
> page in the block) was overwritten with garbage data (can't
> tell whether it's "good" data from some where else yet).

If power is lost during an erase, the memory cells are left in an 
undefined state with a "half bucket" of electrons which can be 
read as a one or a zero depending on the temperature, supply 
voltage, age and the wind ;-) The garbage data would very 
propably produce a data ECC error (mtd ecc), but this is not 
guaranteed.

If an error is detected by a failed read (mtd ecc), I would 
expect Yaffs to recover.  If not, and Yaffs' test of it's own 
spare/tags "mini ECC" looks good, then the data would be assumed 
valid and presented as part of a Yaffs file.
[Have I got this right Charles?]

If you compute the ECC data for the "corrupted" block header
page, is it correct?
Is the mini-ecc that runs over the Yaffs tags correct?

> I'm running 2.4.27 linux with the latest yaffs2 tarball. I'm
> unable to quickly move to 2.6.

Linux 2.5 vs. 2.6 should not matter; there are many others
in the same boat (real world).

-imcd