Re: [PATCH] mtd: ubi: Max out default wear-leveling threshold

["Stefan Riedmüller" <s.riedmueller@phytec.de>]

Hi Sascha,

On 11.07.19 09:01, Sascha Hauer wrote:
> On Wed, Jul 10, 2019 at 01:27:30PM +0200, Stefan Riedmueller wrote:
>> Due to the recursive ubi_thread implementation in the barebox, a large
>> amount of wear-leveling can lead to a stack overflow.
>>
>> This was observed during extensive ubi stress tests with the linux
>> kernel and periodic power cycles. We found that if the wear-leveling
>> threshold is exceeded and a large amount of erase blocks need
>> wear-leveling the stack can overflow.
>>
>> The hardware used to observe this was a phyCORE-i.MX 6 with 1GB NAND flash.
>>
>> As the kernel is perfectly capable of handling wear-leveling we can
>> increase the wear-leveling threshold in the barebox to leave it to the
>> kernel. To minimize the chance of wear-leveling in the barebox max out
>> the threshold.
> 
> I can follow the reasoning and it seems indeed better and more safe to
> leave the wearleveling to the Kernel. Given that, can't we just disable
> wear leveling completely in barebox?

I think it would be best to disable it or at least improve it. But since 
wear-leveling is not an isolated task but involved in more functionalities I 
couldn't find an easy way to disable it in a quick way. That is why I went 
with the threshold enlargement to have at least a quick fix.

But I agree that at some point in the future the root cause should be 
handled and not just the symptom.

Stefan

> 
> Sascha
> 

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