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SubjectRe: [PATCH] [RFC] bpf: tracing: new helper bpf_get_current_cgroup_ino
On Sun, May 13, 2018 at 07:33:18PM +0200, Alban Crequy wrote:
>
> +BPF_CALL_2(bpf_get_current_cgroup_ino, u32, hierarchy, u64, flags)
> +{
> + // TODO: pick the correct hierarchy instead of the mem controller
> + struct cgroup *cgrp = task_cgroup(current, memory_cgrp_id);
> +
> + if (unlikely(!cgrp))
> + return -EINVAL;
> + if (unlikely(hierarchy))
> + return -EINVAL;
> + if (unlikely(flags))
> + return -EINVAL;
> +
> + return cgrp->kn->id.ino;

ino only is not enough to identify cgroup. It needs generation number too.
I don't quite see how hierarchy and flags can be used in the future.
Also why limit it to memcg?

How about something like this instead:

BPF_CALL_2(bpf_get_current_cgroup_id)
{
struct cgroup *cgrp = task_dfl_cgroup(current);

return cgrp->kn->id.id;
}
The user space can use fhandle api to get the same 64-bit id.

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