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

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Date:   Fri, 24 Apr 2020 09:13:02 +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 2020/4/24 0:07, Alexei Starovoitov wrote:
> On Wed, Apr 22, 2020 at 11:25 PM maowenan <maowenan@...wei.com> wrote:
>>
>> 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()?
> 
> which one?
I mean pr_warn is no need, this patch just change the return code ERR_PTR(-EOPNOTSUPP);
+               pr_warn("map type %d not supported or kernel config not opened\n", type);
> 
> .
>