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Date:   Fri, 1 Oct 2021 17:01:09 +0200 (CEST)
From:   torvic9@mailbox.org
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "paolo.valente@linaro.org" <paolo.valente@linaro.org>,
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Subject: Re: [BUG] kernel BUG at mm/slub.c - possible BFQ issue?
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> 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.

> 
> 5.13 doesn't seem to be affected AFAICS.
> 
> Does anyone have an idea what is going on?
> I will now revert the above commit and see if that helps...
> 
> Thanks,
> Tor