linux-kernel - Re: [PATCH v4 1/2] perf/core: Bail out early if the request AUX area is out of bound

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Date:   Wed, 6 Sep 2023 15:07:41 +0800
From:   Shuai Xue <xueshuai@...ux.alibaba.com>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     James Clark <james.clark@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        alexander.shishkin@...ux.intel.com, mingo@...hat.com,
        baolin.wang@...ux.alibaba.com, acme@...nel.org,
        mark.rutland@....com, jolsa@...nel.org, namhyung@...nel.org,
        irogers@...gle.com, adrian.hunter@...el.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        nathan@...nel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v4 1/2] perf/core: Bail out early if the request AUX area
 is out of bound



On 2023/9/6 15:02, Leo Yan wrote:
> Hi Shuai,
> 
> On Wed, Sep 06, 2023 at 11:27:38AM +0800, Shuai Xue wrote:
> 
> [...]
> 
>>>>> +	/* Can't allocate more than MAX_ORDER */
>>>>
>>>> The comment is confused.  I'd like to refine it as:
>>>>
>>>>   /*
>>>>    * kcalloc_node() is unable to allocate buffer if the size is larger
>>>>    * than: PAGE_SIZE << MAX_ORDER; directly bail out in this case.
>>>>    */
>>>
>>> Hi, Leo,
>>>
>>> Thank you for your quick feedback. The comment is simplified from Peter's reply in v2
>>> version. Your refined comment is more detailed and it makes sense to me, I would like
>>> to adopt it if @Peter has no other opinions.
>>>
>>>> To be honest, I am not sure if perf core maintainers like this kind
>>>> thing or not.  Please seek their opinion before you move forward.
>>>>
>>>
>>> and hi, all perf core maintainers,
>>>
>>> I have not received explicit objection from perf core maintainers @Peter or @James so
>>> I moved forward to address their comments. It's fine to me to wait for more opinions from
>>> perf core maintainers.
>>>
>>> Best Regards,
>>> Shuai
>>>
>>
>> Hi, Leo, and all folks,
>>
>> Any more comments? Should I move forward to send a new patch?
> 
> I am afraid I cannot give a reliable suggestion.
> 
> Anyway, I personally think the returned error value in this patch is
> better than the kernel oops since the kernel oops is a bit scary for
> tool's users ;)   Another reason is the perf core layer should report
> error earlier rather than relying on the page buddy allocation layer
> to detect the memory allocation failure, which is easier for both
> developers and users to understand the failure.
> 
> IMHO, a good practice is to respin a new patch set and send out for
> review.  Good luck!
> 

Hi, Leo,

Thanks for valuable comments.

I will send a new patch set.

Thank you.

Best Regards,
Shuai