Re: UBI/UBIFS issue: corrupt empty space => switched to read-only mode

[Artem Bityutskiy <dedekind1@gmail.com>]

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On Fri, 2012-03-16 at 17:14 +0100, Matteo Mattei wrote:
> Hi guys,
> 
> I am working hard on UBIFS to make it works on 2.6.32 and OMAP3530.
> 
> I already posted some requests to TI forum but I have no answers up to now:
> http://e2e.ti.com/support/embedded/linux/f/354/t/171839.aspx#627875

Well, this error was reported several times. AFAIR, there are 2 possible
causes for this.

1. Your driver does not protect the empty space. Normally the driver
corrects bit-flips using ECC, but some systems do not do this for empty
space, i.e., for the flash regions which have been erased but have never
been written. UBIFS expects to see all 0xFFs there, and if it doesn't,
it reports about corrupt empty space.

You can fix this by fixing the driver, at least this is what people seem
to do. If this is impossible to fix, you can teach UBIFS to tolerate
bit-flips in the empty space.

2. More difficult issue which no one still dares to start fixing is the
unstable bits issue. I do not have time to work on this, so I offer
everyone assistance, but no on so far started working on this, AFAIK.
Here is the description of the issue:

http://www.linux-mtd.infradead.org/doc/ubifs.html#L_unstable_bits

HTH.

-- 
Best Regards,
Artem Bityutskiy

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