Re: [PATCH bpf-next] bpf: Support default .validate() and .update() behavior for struct_ops links

Stanislav Fomichev
2023-08-10T22:46:24Z

On 08/10, David Vernet wrote:
> Currently, if a struct_ops map is loaded with BPF_F_LINK, it must also
> define the .validate() and .update() callbacks in its corresponding
> struct bpf_struct_ops in the kernel. Enabling struct_ops link is useful
> in its own right to ensure that the map is unloaded if an application
> crashes. For example, with sched_ext, we want to automatically unload
> the host-wide scheduler if the application crashes. We would likely
> never support updating elements of a sched_ext struct_ops map, so we'd
> have to implement these callbacks showing that they _can't_ support
> element updates just to benefit from the basic lifetime management of
> struct_ops links.
>
> Let's enable struct_ops maps to work with BPF_F_LINK even if they
> haven't defined these callbacks, by assuming that a struct_ops map
> element cannot be updated by default.

Any reason this is not part of sched_ext series? As you mention,
we don't seem to have such users in the three?