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Message-ID: <428689f2-ad91-e1b4-64c5-c1c4802e2cbe@tessares.net>
Date:   Sun, 10 Jul 2022 22:19:03 +0200
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Subject: Re: [PATCH bpf-next] bpf: fix 'dubious one-bit signed bitfield'
 warnings
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To:     Yonghong Song <yhs@fb.com>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Eduard Zingerman <eddyz87@gmail.com>
Cc:     mptcp@lists.linux.dev, bpf@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220710083523.1620722-1-matthieu.baerts@tessares.net>
 <fd51d0bb-8908-ede1-6d7a-37ed82badebf@fb.com>
From:   Matthieu Baerts <matthieu.baerts@tessares.net>
In-Reply-To: <fd51d0bb-8908-ede1-6d7a-37ed82badebf@fb.com>
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Hi Yonghong,

Thank you for the review!

On 10/07/2022 18:59, Yonghong Song wrote:> On 7/10/22 1:35 AM, Matthieu
Baerts wrote:
>> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
>> index 81b19669efba..2ac424641cc3 100644
>> --- a/include/linux/bpf_verifier.h
>> +++ b/include/linux/bpf_verifier.h
>> @@ -345,10 +345,10 @@ struct bpf_verifier_state_list {
>>   };
>>     struct bpf_loop_inline_state {
>> -    int initialized:1; /* set to true upon first entry */
>> -    int fit_for_inline:1; /* true if callback function is the same
>> -                   * at each call and flags are always zero
>> -                   */
>> +    bool initialized; /* set to true upon first entry */
>> +    bool fit_for_inline; /* true if callback function is the same
>> +                  * at each call and flags are always zero
>> +                  */
> 
> I think changing 'int' to 'unsigned' is a better alternative for
> potentially adding more bitfields in the future. This is also a pattern
> for many other kernel data structures.

There was room, I was not sure if it would be OK but I saw 'bool' were
often used in structures from this bpf_verifier.h file.

I can of course switch to an unsigned one. I would have picked 'u8' when
looking at the structures around but any preferences from you?
'unsigned', 'unsigned int', 'u8', 'u32'?

Cheers,
Matt
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