Bad Blocks On JFFS2/NAND

[Simon Haynes]

I have experienced a problem in which a JFF2 filesystem on NAND became full. 
This is a root file system and constant writes to a logfile filled the 
filesystem. On investigation it was found that the NAND device now had 
hundreds of bad blocks. 

I started to investigate this and found that JFFS2 was announcing 

Newly-erased block contained word 0x1985e002 at offset 0x020f7e00

Messages which result in my mtd/jffs2 code marking the block bad. What I find 
strange is that a subsequent scan list the new block at a different 16k 
offset when the device erasesize is 16k, in this case 0x020f0000.
Is that because my device is 128Mb and JFFS2 is using this 'virtual erase 
size' of 32k ?

I have observed this now on several different NAND devices and it seems to be 
more prominent while performing small writes.

I am currently trying to work out if the erase is not completing, or this is 
the wrong block or something else. 

I was wondering if anyone has seen something similar

Cheers

Simon.