Re: Flashing UBIFS image to gluebi mtd

[Ezequiel Garcia <ezequiel.garcia@free-electrons.com>]

On Thu, Oct 31, 2013 at 10:00:30PM +0400, Konstantin Tokarev wrote:
> 
> 
> 31.10.2013, 19:08, "Ezequiel Garcia" <ezequiel.garcia@free-electrons.com>:
> > Hi Konstantin,
> >
> > On Thu, Oct 31, 2013 at 05:48:34PM +0400, Konstantin Tokarev wrote:
> >
> >>  I'm migrating rootfs of device from SquashFS on top of gluebi to UBIFS.
> >
> > Sounds like you could use ubiblock for that setup, which is suitable
> > for squashfs, and completely independent of ubifs (thus less cpu and
> > memory hungry and easier to setup).
> 
> Could you elaborate this a bit more? Do you mean that block device emultaion
> layer on top of UBI + FS on top of that can work faster than UBIFS on top of
> UBI?
> 

Given you provided no details, I'm not sure why you're migrating from squashfs
(which is a read-only, block oriented fs) to ubifs (which supports r/w on MTD).
But anyway, let me do this homework for you :-)

So, you had squashfs on top of gluebi, right? I guess you had this:

  mtd (plus your NAND driver) -> ubi -> gluebi/mtd -> mtdblock -> squashfs

On the other side, using ubiblock to emulate the block device you'd
end up with this:

  mtd (plus your NAND driver) -> ubi -> ubiblock -> squashfs

Which is less memory (cpu?) hungry than the first alternative.
The latest git branch also contained a non-cached option which
has shown some good behavior, given squashfs does its own caching.

But of course, this is _NOT_ a replacement for UBIFS, and using ubiblock
for R/W is strictly discouraged.

And here's the (already ancient) discussion:

http://lists.infradead.org/pipermail/linux-mtd/2012-November/045011.html

And the v2:
http://lists.infradead.org/pipermail/linux-mtd/2012-December/045274.html

I'll post the latest work as soon as I find some time, but you're free
to pursue your own research.

Hope it helps and best of lucks!
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com