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Subject: Re: md_raid: mdX_raid6 looping after sync_action "check" to "idle"
 transition
To:     Dragan Stancevic <dragan@stancevic.com>,
        Yu Kuai <yukuai1@huaweicloud.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>,
        "yukuai (C)" <yukuai3@huawei.com>
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From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <0d79d1f9-00e8-93be-3c7c-244030521cd7@huaweicloud.com>
Date:   Wed, 30 Aug 2023 09:36:53 +0800
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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.
> 
> 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.
>