Unstable bits CEWG project

[Artem Bityutskiy]

On Mon, 2012-10-15 at 18:28 -0300, Ezequiel Garcia wrote:
> Hello all,
> 
> I'm considering to propose myself as a candidate for the CEWG funded
> "Unstable bits" project [1].
> 
> I'd like to know if anyone has considered the posibility of adding
> power-cut emulation to nandsim driver;
> or if this is just a stupid idea.

I'd suggest to add this in UBI instead.

1. nandsim is quite unreadable already and difficult to deal with
2. UBI is cleaner and all the I/O goes through functions in the io.c
   file.
3. By having it in UBI it is possible to force p-c emulation in
   interesting places, like when we are updating the volume table,
   or recovering from a failed write, or torturing a PEB, or writing
   EC/VID headers, or doing something fastmap-related.

   If you do this in nandsim, you will get 99% of power cuts when
   writing data, so you will mostly test this, and very rarely cover
   other places, unless you run for days.

   We passes through this when developing UBIFS, and this is why we
   put the power-cut emulation to UBIFS. I guess nowadays you can move
   it down to UBI.

Also, FYI, we have the integck test which supports emulated power-cut
testing for UBIFS.

-- 
Best Regards,
Artem Bityutskiy
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