Re: ubifs version 1 compatibility

[Artem Bityutskiy <dedekind@infradead.org>]

On Fri, 2009-03-27 at 00:15 +1100, Hamish Moffatt wrote:
> On Thu, Mar 26, 2009 at 02:12:05PM +0200, Artem Bityutskiy wrote:
> > On Thu, 2009-03-26 at 23:04 +1100, Hamish Moffatt wrote:
> > > On Thu, Mar 26, 2009 at 11:50:23AM +0200, Artem Bityutskiy wrote:
> > > > On Thu, 2009-03-26 at 18:44 +1100, Hamish Moffatt wrote:
> > > > makes it very difficult to turn old image into new one. This will
> > > > basically mean we need:
> > > > 
> > > > 1. extract files from the old image
> > > > 2. feed them to mkfs.ubifs.
> > > > 
> > > > > Maybe before upgrade we could run mkfs.ubifs using the contents of the
> > > > > existing volume to create the new format, unmount it and ubiupdatevol it..
> > > > 
> > > > The easiest way to do this is to boot the old kernel,
> > > > e.g. in vmware, extract the files using the nandsim technique:
> > > > http://www.linux-mtd.infradead.org/faq/ubifs.html#L_ubifs_nandsim
> > > > 
> > > > then feed them to mkfs.ubifs.
> > > 
> > > Well I have these files on embedded devices out in the real world. The
> > > volume is storing user data, so I need to do this change in-place.
> > 
> > Let me make sure I understand the need.
> > 
> > So you have devises with v1 format in the wild. You want to upgrade
> > those devices. While upgrading, you will re-write some UBI volumes, but
> > after upgrade the user-data volume should contains exactly the same data
> > as before the upgrade, right?
> 
> Yes, that's what I need.

I see. Well, because most of the UBIFS functionality is in the
kernel, it might probably be possible to teach the kernel UBIFS
implementation to automatically re-format the file-system if it
finds v.1 layout. However, this is not a very simple task, and
I am not sure I have time to implement this, sorry :-(


-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)