Re: Lots of fastmap writes

From: Zhihao Cheng <chengzhihao1@huawei.com>
To: Rickard X Andersson <rickaran@axis.com>, <richard@nod.at>,
	<linux-mtd@lists.infradead.org>
Cc: <rickard314.andersson@gmail.com>
Subject: Re: Lots of fastmap writes
Date: Fri, 14 Jun 2024 20:28:27 +0800	[thread overview]
Message-ID: <a8bf10e3-009f-3d4b-fa4b-43bbc6e1bebc@huawei.com> (raw)
In-Reply-To: <aad1b520-ee9e-476f-911b-45be9eb09195@axis.com>

在 2024/6/14 19:42, Rickard X Andersson 写道:
> On 6/4/24 03:52, Zhihao Cheng wrote:

[...]
>>
>> BTW, after applying the patches, the kernel should run on a new flash, 
>> the improved wear-leveling algorithm cannot rescue the worn out image.
>>
> 
> Thanks for the patches!
> 
> I have backported the patches to Linux kernel 6.1. Do you think the 
> patches are safe to apply to Linux kernel 6.1?

Yes, it's okay. I have backported the patches to our product(kernel 
v5.10) and it works fine.
> 
> Another thing, would it not be possible to rescue that particular worn 
> out device by simply turning fastmap off on that device?
> 

Can I regard the rescuing as making erase counters become normal 
again(max - min <= UBI_WL_THRESHOLD)? If so, I'm afraid that not all 
PEBs can be rescued, according to get_peb_for_wl().
For example: PB, PC cannot be rescued, unless PA is taken for writing 
and then wl is just right scheduled.

ubi->free tree:
      29600(PB)
1(PA)        29600(PC)

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