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

[Ivan Djelic]

On Fri, Apr 13, 2012 at 04:20:45PM +0100, Artem Bityutskiy wrote:
> > > 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

Hello Matteo,

I have been using a very similar setup (2.6.32 + OMAP3630), and I added BCH support
(8-bit correction) to the mtd omap2 driver, using the BCH library (not TI implementation).
My patch corrects bitflips on empty space (erased pages), so that UBIFS does not choke on corrupted empty space.

I posted a patch a while ago, albeit for a more recent kernel version:
http://lists.infradead.org/pipermail/linux-mtd/2011-October/038207.html
bit I did not get much feedback from TI maintainers.

If you have some trouble backporting this patch to your kernel, let me know, I may
have an old 2.6.32 version of the patch somewhere on my hdd :).

BR,
--
Ivan

> > 
> > Hi Aartem,
> > I have some updates (also a BCH fix) as reported here:
> > http://e2e.ti.com/support/embedded/linux/f/354/t/171839.aspx
> > 
> > Anyway the read-only mounting persists.
> > I have errors also at run time (without power cuts) simply performing very 
> > frequent and stressful reading/writing operations (using dd and md5sum with 8 
> > parallel processes).
> 
> Does BCH in your tree protects the free space? CCing Ivan, just in case.
> Preserving more than usual of the context for him.
> 
> > 
> > At this point I am wondering:
> > 1- Is possibile that the "unstable bits" issue happens also during run-time 
> > simply reading and writing?
> 
> Not as far as I know.
> 
> > 2- How can I do to tolerate bit-flips in the empty space?