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Subject: Re: [BUG] btrfs potential failure on 32 core LTP test (fallocate05)
To:     Josef Bacik <josef@toxicpanda.com>, Chris Mason <clm@fb.com>,
        David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org,
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        Qu Wenruo <wqu@suse.com>, Filipe Manana <fdmanana@suse.com>
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From:   Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Message-ID: <30d510db-df48-e499-6e46-bd84c85d4b41@canonical.com>
Date:   Wed, 30 Jun 2021 10:34:56 +0200
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On 29/06/2021 20:32, Josef Bacik wrote:
> On 6/29/21 2:28 PM, Krzysztof Kozlowski wrote:
>> On 29/06/2021 20:06, Krzysztof Kozlowski wrote:
>>> Minor update - it's not only Azure's. AWS m5.8xlarge and m5.16xlarge (32
>>> and 64 cores) fail similarly. I'll try later also QEMU machines with
>>> different amount of CPUs.
>>>
>>
>> Test on QEMU machine with 31 CPUs passes. With 32 CPUs - failure as
>> reported.
>>
>> dmesg is empty - no error around this.
>>
>> Maybe something with per-cpu variables?
> 
> Ah yeah, so since you are further into this than I am, want to give my recent 
> batch of fixes a try?
> 
> https://github.com/josefbacik/linux/tree/delalloc-shrink
> 
> This might actually resolve the problems.  If not I'm getting one of our 64cpu 
> boxes setup to test this, I also couldn't reproduce it on my smaller local 
> machines.  Thanks,

I just gave ita try on v5.13 + merge of your branch and it fixes the
issue, at least on QEMU with 32 and 64 CPUs.

Would be good to find the exact commit fixing it to be sure it gets
backported to stables.


Best regards,
Krzysztof