netdev - Re: [PATCH bpf-next v2 1/2] bpf: Change error code when ops is NULL

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Date:   Thu, 23 Apr 2020 14:25:22 +0800
From:   maowenan <maowenan@...wei.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, <kernel-janitors@...r.kernel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>
Subject: Re: [PATCH bpf-next v2 1/2] bpf: Change error code when ops is NULL

On 2020/4/23 13:43, Alexei Starovoitov wrote:
> On Wed, Apr 22, 2020 at 8:31 PM Mao Wenan <maowenan@...wei.com> wrote:
>>
>> There is one error printed when use BPF_MAP_TYPE_SOCKMAP to create map:
>> libbpf: failed to create map (name: 'sock_map'): Invalid argument(-22)
>>
>> This is because CONFIG_BPF_STREAM_PARSER is not set, and
>> bpf_map_types[type] return invalid ops. It is not clear to show the
>> cause of config missing with return code -EINVAL, so add pr_warn() and
>> change error code to describe the reason.
>>
>> Signed-off-by: Mao Wenan <maowenan@...wei.com>
>> ---
>>  kernel/bpf/syscall.c | 7 ++++---
>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
>> index d85f37239540..7686778457c7 100644
>> --- a/kernel/bpf/syscall.c
>> +++ b/kernel/bpf/syscall.c
>> @@ -112,9 +112,10 @@ static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
>>                 return ERR_PTR(-EINVAL);
>>         type = array_index_nospec(type, ARRAY_SIZE(bpf_map_types));
>>         ops = bpf_map_types[type];
>> -       if (!ops)
>> -               return ERR_PTR(-EINVAL);
>> -
>> +       if (!ops) {
>> +               pr_warn("map type %d not supported or kernel config not opened\n", type);
>> +               return ERR_PTR(-EOPNOTSUPP);
>> +       }
> 
> I don't think users will like it when kernel spams dmesg.
> If you need this level of verbosity please teach consumer of libbpf to
> print them.
> It's not a job of libbpf either.
thanks for reviw, so is it better to delete redundant pr_warn()?

> 
> .
>