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Subject: Re: [BUG] kernel BUG at mm/slub.c - possible BFQ issue?
To:     torvic9@mailbox.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "paolo.valente@linaro.org" <paolo.valente@linaro.org>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
References: <1624640454.149631.1632987871186@office.mailbox.org>
 <1889051823.161943.1633100469857@office.mailbox.org>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <2abec603-cad9-d87e-356c-9fe49dbbb3a3@kernel.dk>
Date:   Fri, 1 Oct 2021 09:02:28 -0600
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On 10/1/21 9:01 AM, torvic9@mailbox.org wrote:
>> torvic9@mailbox.org hat am 30.09.2021 09:44 geschrieben:
>>
>>  
>> Hello,
>>
>> I encounter a hard freeze on both 5.14 and 5.15 when using BFQ.
>> Unfortunately, I do not have a full error log, because the computer
>> totally freezes and slightly corrupts the display, so it's
>> impossible to read the entire message.
>>
>> However, what I could get is the following:
>>
>>   kernel BUG at mm/slub.c:379
>>   invalid opcode: 0000 [#1]
>>   RIP: 0010:__slab_free
>>   [...]
>>   Call Trace:
>>   bfq_set_next_ioprio_data
>>   [...]
>>   bfq_put_queue
>>   bfq_insert_requests
>>   [...]
>>
>> This issue appears more or less randomly and it sometimes takes a
>> little while to reproduce it (running fio helps).
>> The call trace always contains references to BFQ, but they are not
>> always the exact same. Once, I could see on the corrupted display
>> the message "general protection fault".
>> I could reproduce this issue on two computers.
>>
>> Not quite sure but I *think* the issue first appeared somewhere around
>> 5.14.5 or 5.14.6, during which time BFQ only got the following commit:
>>
>>   (88013a0c5d99) block, bfq: honor already-setup queue merges
> 
> I have now reverted the above commit and launched some heavy I/O like
> e.g. git kernel, fio, xz compression, and so far, no freezes anymore!
> Too early to say that this commit really is the cause though.
> Would be great if someone could have a look at it.

It's known buggy, and a revert has been queued up since earlier this
week. It'll go to Linus for 5.15-rc4, and will hit 5.14 stable shortly
thereafter.

-- 
Jens Axboe