Re: [RFC] UBIFS recovery

[Richard Weinberger <richard@nod.at>]

Am 09.02.2015 um 11:38 schrieb hujianyang:
> Hi Artem and Richard,
> 
> On 2015/2/9 15:57, Richard Weinberger wrote:
>> Am 09.02.2015 um 08:51 schrieb Artem Bityutskiy:
>>> On Mon, 2015-02-09 at 10:34 +0800, hujianyang wrote:
>>>> Good suggestions. I will try to realize periodically commit first. But I
>>>> don't know if this feature is really needed. Switch to R/O and revert to
>>>> last comitted state? But we just consider about log before, never think
>>>> about index.
>>>
>>> I think the right way to approach this problem is to come up with a high
>>> level summary of the problems we are trying to solve, and the solutions,
>>> along with some analysis of the solutions. This does not have to be very
>>> detailed, but it should put everyone involved into the same page.
>>
>> Agreed. I fear we're talking about different things. :)
>>
> 
> I'm afraid I didn't express the use case of the corruption recovery feature.
> UBIFS is used mostly in embedded environment. After products selling out,
> it's hard to debug it. So the production team may consider any failure that
> could happen and put the recovery method into their operation scripts/utilities.
> 
> Flash corruption is a problem they need to care about. Using high quality
> cell is not enough, ECC error could not be avoid. So a recovery method which
> is provided by filesystem itself is required. This feature is not used by
> us, the developer of kernel, but the production team. They know little about
> linux kernel. So the easier interface we provide, the much effective recovery
> method of the products they could make. So, Artem, I'm agree with your another
> email mail about R-gadget and H-gadget.
> 
> I think mount R/O is a good beginning. We don't need consider much about how
> to recover but can provide a usable(in some cases) file-system. And a R/O
> mount means we could do some cleanup to revert to this R/O state. This R/O
> mount should be provided by driver itself without any userspace tools.

So, at the end of the day you want an UBIFS that can deal with randomly failed PEBs?

Thanks,
//richard