Re: [PATCH 1/4 v3] cgroup: use separate rstat api for bpf programs

["Michal Koutný" <mkoutny@suse.com>]

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On Wed, Mar 19, 2025 at 03:21:47PM -0700, JP Kobryn <inwardvessel@gmail.com> wrote:
> The rstat updated/flush API functions are exported as kfuncs so bpf
> programs can make the same calls that in-kernel code can. Split these API
> functions into separate in-kernel and bpf versions. Function signatures
> remain unchanged. The kfuncs are named with the prefix "bpf_". This
> non-functional change allows for future commits which will modify the
> signature of the in-kernel API without impacting bpf call sites. The
> implementations of the kfuncs serve as adapters to the in-kernel API.

This made me look up
https://docs.kernel.org/bpf/kfuncs.html#bpf-kfunc-lifecycle-expectations

The series reworks existing kfuncs anyway, is it necessary to have the
bpf_ versions? The semantics is changed too from base+all subsystems
flush to only base flush (bpf_rstat_flush()).

I'd perhaps do the changes freely w/out taking kfuncs into account and
then add possible reconstructive patches towards the end of the series.
(I'm not unsure whether the modified btf_type_tag_percpu.c selftest
survives the latest unionization of base stats.)


Michal

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