AW: UBIFS corruption and UBI + unstable bit questions

[Morand, Guy]

> Can you please be more specific.
> What exactly do you mean by "only the partition"?
> Also what do you mean by "corrupted"?

Sorry, nomenclature problem ... I mean by a volume the layer on top of the MTD 
device (UBI):
ubiformat /dev/mtd1
ubiattach /dev/ubi_ctrl -m 1

By partition, I mean actually a volume on top of UBI (UBIFS):
ubimkvol /dev/ubi0 -N partition1 -s 64MiB
ubimkvol /dev/ubi0 -N partition2 -m

Then if there is a "unstable bit" on partition1, is also the partition2 
corrupted? This means there is nothing I can do to restore it.

> UBI/FS is not a magic bullet. People who *really* care about power cut safety
> attack the problem also with their hardware.
Yieah right, I understand... I've seen some hardware with super caps that gives 
some time to Linux to shutdown correctly, I really love it!

> Are you able to trigger this problem?
No, I'm just thinking about a nice partitioning strategy on my platform to 
avoid as much corruptions as possible with the hardware I have in hands!

Kind regards,

Guy

-----Ursprüngliche Nachricht-----
Von: Richard Weinberger [mailto:richard.weinberger at gmail.com] 
Gesendet: Donnerstag, 26. März 2015 17:45
An: Morand, Guy
Cc: linux-mtd at lists.infradead.org
Betreff: Re: UBIFS corruption and UBI + unstable bit questions

On Thu, Mar 26, 2015 at 5:00 PM, Morand, Guy <Guy.Morand at comet.ch> wrote:
> Hello UBI developers,
>
> I was wondering what happens to the UBI volume if an UBIFS partition gets
> corrupted:
> * Is only the partition corrupted?
> * Is the whole volume corrupted?

Can you please be more specific.
What exactly do you mean by "only the partition"?
Also what do you mean by "corrupted"?

If a filesystem is corrupted there is nothing you can do...
(By definition of corrupted)

> Moreover, about this "Unstable bit issue" ...
> * Does it still make sense to use UBI/UBIFS as it doesn't seem to be fully
>   power cut failsafe?

It all depends on how you define "fully power cut failsafe".
UBI/FS is not a magic bullet. People who *really* care about power cut safety
attack the problem also with their hardware.
e.g., by not using the cheapest NAND chip they can find. ;-)

> * Have you planned to fix this issue?

TBH nobody cared enough so far to either fix the issue on its own or
fund one of us UBI developers.

Are you able to trigger this problem?

-- 
Thanks,
//richard