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To:     Yi Li <yilikernel@gmail.com>
Cc:     Yi Li <yili@winhong.com>, kent.overstreet@gmail.com,
        linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org,
        Guo Chao <guochao@winhong.com>
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From:   Coly Li <colyli@suse.de>
Subject: Re: [PATCH] bcache: fix panic due to cache_set is null
Message-ID: <79fde596-254a-510c-547a-b1525985de9d@suse.de>
Date:   Thu, 3 Dec 2020 14:56:45 +0800
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On 12/3/20 2:25 PM, Yi Li wrote:
>> On 12/1/20 12:35 PM, Yi Li wrote:
>>> sorry, This patch will cause deadlock, i will check and redo it.
>>
>> Can you try latest upstream kernel firstly ? Before spending more time
>> on the fix.
>>
> 
> This issue just happened three times （xenserver7.5 dom0 kernel） on the
> same machine and cannot reproduce it now. and have not reproduce it
> using the lastest uptream kernel.
> 

Hmm, this is something very probably that I am not able to help. It
seems the kernel is a third-part maintained Linux v4.4 based kernel +
bcache backport, which is out of my view.

If similar problem happens on latest upstream kernel, or at least v5.8+
kernel, I can help to take a look.


>> If I remember correctly, when cancel_writeback_rate_update_dwork() is
>> not timed out, the cache set memory won't be freed before the
>> writeback_rate_update worker terminates. It is possible that I miss
>> something in the code, but I suggest to test with a kernel after v5.3,
>> and better a v5.8+ kernel.
>>
>> Coly Li
>>
> Thanks.
> 
> it is  confused that why writeback_rate_update worker run  again after
> cancel_delayed_work_sync( kernel log telled).
> 

[snipped]

Coly Li