linux-kernel - Re: [PATCH] [RFC] bpf: tracing: new helper bpf_get_current_cgroup

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Message-ID: <CAH3MdRVwmKd84ePvNX+NuAj3TfA_28BObEmzBqGXv=P5_A=8fQ@mail.gmail.com>
Date:   Tue, 22 May 2018 21:31:04 -0700
From:   Y Song <ys114321@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Alban Crequy <alban.crequy@...il.com>,
        netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org,
        containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
        Alban Crequy <alban@...volk.io>, tj@...nel.org
Subject: Re: [PATCH] [RFC] bpf: tracing: new helper bpf_get_current_cgroup_ino

On Tue, May 22, 2018 at 8:35 PM, Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
> On Tue, May 22, 2018 at 08:33:24PM -0700, Y Song wrote:
>> +       struct cgroup *cgrp = task_dfl_cgroup(current);
>> +       if (!cgrp)
>> +               return -EINVAL;
>
> why this check is needed?

No reason :-) Originally I am concerned whether it is possible cgrp
could be NULL.
By looking at the code, it SEEMS to me that it could not be NULL, but I am not
100% sure (as I am not a cgroup expert). Since you are asking,
probably means it cannot be NULL, so will remove it in formal upstream patch.