RFC: detect and manage power cut on MLC NAND

[Artem Bityutskiy]

On Mon, 2015-03-23 at 13:18 +1100, Iwo Mergler wrote:
> On Fri, 20 Mar 2015 19:26:11 +1100
> Boris Brezillon <boris.brezillon at free-electrons.com> wrote:
> 
> > You want to do that in order to avoid using 2 Jumbo pages to only
> > store a few bytes ?
> 
> Yes. I'm already a little unhappy about using two whole pages
> for UBI, and don't want to be guilty of doubling that.
> 
> > Artem suggested another solution to deal with that: duplicate the EC
> > header in the VID header so that EC information can be recovered when
> > writing to the page paired with the EC header.
> 
> Sounds good to me. It won't avoid the loss of the VID header,
> but it will safeguard the EC. It's free, too.
> 
> > You'd still have to prevent any write on the page paired with the EC
> > header, but you're still saving one page with this approach and avoid
> > any corruption of UBI metadata caused by paired pages.
> 
> Ah, you probably meant VID header here, right?

If we sacrifice another page, we could store a copy of the VID header
there, in case the first copy gets corrupted. IOW, we'd have:

	ECH, VIDH#1, VIDH#2, User Data.