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Subject: Re: md_raid: mdX_raid6 looping after sync_action "check" to "idle"
 transition
To:     Yu Kuai <yukuai1@huaweicloud.com>,
        Dragan Stancevic <dragan@stancevic.com>, song@kernel.org
Cc:     buczek@molgen.mpg.de, guoqing.jiang@linux.dev,
        it+raid@molgen.mpg.de, linux-kernel@vger.kernel.org,
        linux-raid@vger.kernel.org, msmith626@gmail.com,
        "yangerkun@huawei.com" <yangerkun@huawei.com>
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From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <ff996ffb-cba5-cc9b-2740-49ba4a1869b5@huaweicloud.com>
Date:   Tue, 5 Sep 2023 11:50:10 +0800
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Hi,

在 2023/08/30 9:36, Yu Kuai 写道:
> Hi,
> 
> 在 2023/08/29 4:32, Dragan Stancevic 写道:
> 
>> Just a followup on 6.1 testing. I tried reproducing this problem for 5 
>> days with 6.1.42 kernel without your patches and I was not able to 
>> reproduce it.

oops, I forgot that you need to backport this patch first to reporduce
this problem:

https://lore.kernel.org/all/20230529132037.2124527-2-yukuai1@huaweicloud.com/

The patch fix the deadlock as well, but it introduce some regressions.

Thanks,
Kuai

>>
>> It seems that 6.1 has some other code that prevents this from happening.
>>
> 
> I see that there are lots of patches for raid456 between 5.10 and 6.1,
> however, I remember that I used to reporduce the deadlock after 6.1, and
> it's true it's not easy to reporduce, see below:
> 
> https://lore.kernel.org/linux-raid/e9067438-d713-f5f3-0d3d-9e6b0e9efa0e@huaweicloud.com/ 
> 
> 
> My guess is that 6.1 is harder to reporduce than 5.10 due to some
> changes inside raid456.
> 
> By the way, raid10 had a similiar deadlock, and can be fixed the same
> way, so it make sense to backport these patches.
> 
> https://lore.kernel.org/r/20230529132037.2124527-5-yukuai1@huaweicloud.com
> 
> Thanks,
> Kuai
> 
> 
>> On 5.10 I can reproduce it within minutes to an hour.
>>
> 
> .
>