Grow UBI device?

[Wolfgang Denk]

Dear "Gupta, Pekon",

In message <20980858CB6D3A4BAE95CA194937D5E73EA20350 at DBDE04.ent.ti.com> you wrote:
>
> > > It would be nice if I could start with a UBI device that is smaller
> > > than the NAND, so I can keep an existing MTD partition with a JFFS2
> > > file system. After copying the data from JFFS2 to a UBIFS volume, I
> > > would like to free and reuse the space of this JFFS2 partition.
> > >
> That seems to be a nice move, but where would you copy the existing
> JFFS2 data ?

Well, I wrote: "copy[...] the data from JFFS2 to a UBIFS volume".

> (a) In memory, then there is threat of losing the data due to
>   power-failure, and you should have enough RAM.
> (b) copy to target UBIFS volume/partition. So assumption is that target
>   UBI volume has enough space and is writable.
> I'm assuming (b) is more workable .. 

...which is what I'm after.

> > Come to think of it, I'm not sure that would work anyway, as the
> > resulting, new, enlarged partition would partly contain UBI data and
> > partly old jffs2 data. I'm not sure what UBI does when it encounters
> > incorrect data, if it just erases the relevant blocks and formats them for
> > its own use, or if it barfs completely and just bails out complaining that
> > the partition does not contain UBI data. If the relevant blocks were
> > erased, then I think UBI would simply concede that the a previous erase
> > attempt had been prematurely aborted, and re-erase the blocks and write
> > its headers, so perhaps that is something to try. At any rate it involves
> > at least some mild trickery (erase the blocks that previously contained
> > jffs2 data).
> > 
> Yes, during mounting of UBIFS volumes, UBI checks for erase-header
> on first-page of every block. 

Mounting UBIFS volumes should not be a problem - the existing ones are
not located in the newly added area of the NAND.  The question however
is what the UBI layer itself does, if I for example try to create a
new volume which then would allocate blocks from the newly added
space.

> So, effectively you don't even need to erase the partition to convert
> it into UBI volume, you just try attaching it as UBI volume and UBI
> should erase it for you. (though flagging some warnings on the way).

Are you sure about that?

Well, I guess I'll have to try it out in the end...


Thanks!

Best regards,

Wolfgang Denk

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