From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vojtech Myslivec <vojtech@xmyslivec.cz>
Subject: Re: Linux RAID with btrfs stuck and consume 100 % CPU
Date: Wed, 12 Aug 2020 15:58:41 +0200
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To: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>, linux-btrfs@vger.kernel.org, linux-raid@vger.kernel.org
Cc: Michal Moravec <michal.moravec@logicworks.cz>, Song Liu <songliubraving@fb.com>
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Hello,

On 29. 07. 20 23:06, Guoqing Jiang wrote:
> On 7/22/20 10:47 PM, Vojtech Myslivec wrote:
>> 1. What should be the cause of this problem?
> 
> Just a quick glance based on the stacks which you attached, I guess it
> could be
> a deadlock issue of raid5 cache super write.
> 
> Maybe the commit 8e018c21da3f ("raid5-cache: fix a deadlock in superblock
> write") didn't fix the problem completely.  Cc Song.
> 
> And I am curious why md thread is not waked if mddev_trylock fails, you can
> give it a try but I can't promise it helps ...

Just to make sure we use RAID 6 across 6 HDD (I am not sure how RAID 5
implementation relates to RAID 6).