UBIFS recovery fails

[Ivan Djelic]

On Wed, Oct 19, 2011 at 04:15:15PM +0100, Artem Bityutskiy wrote:
> I suggest you to improve the UBIFS power cut emulation functions and
> make them emulate unstable bits, and then use integck which is already
> able to handle emulated power cuts. This will allow you to
> 
> 1. Test quickly
> 2. Continue the half-done work
> 3. Work with nicer code-base than ugly nandsim
> 4. Make it possible to emulate unstable bits in interesting places like
>    TNC, LPT, orphans area, etc. Otherwise most of the failures will be
>    emulated in data area.
> 
> 
> Similarly, something like that should be done in UBI level which will
> emulate power cuts _only_ when writing UBI-specific stuff (e.g., the
> headers).
 
My first hope was maybe to garantee stable data at UBI level, as this would also
secure raw UBI storage. But I have not looked into this seriously yet.

> I know you are driver guy and it is more natural for you to start from
> driver, but I suggest starting from UBIFS and fix 90% of the issues
> there, then go down. This way you will also isolate non-UBIFS specific
> issues.

OK; I also work on filesystem code; so I'm not really obsessed with drivers :-)
 
> Anyway, we should start with _documenting_:
> 1. What are unstable bits
> 2. Which work UBIFS/UBI/MTD needs to handle that.
> 3. What are MLC-specific issues
> 4. What would have to be done to handle them.
> 
> I have ideas about the paired pages in MLC.
> 
> But the thing also is that the whole stack is complex and big and
> has a lot of states (like any FS), so it is easy to miss something and
> you never know the complete list until you actually start stressing the
> stack.
> 
> But let's document what we know at the moment. Then people who are
> interested to have that fixed can start approaching that.

OK, sounds good to me.

BR,
--
Ivan