Re: [PATCH 1/2] block: add BPF kfuncs to read blkcg io.stat

On Mon, Aug 10, 2026 at 10:00:55AM -1000, Tejun Heo wrote:
> Hello,
> 
> On Fri, Aug 07, 2026 at 12:37:31PM -0700, Ziyang Men wrote:
> > +__bpf_kfunc struct blkcg *bpf_get_root_blkcg(void)
> > +__bpf_kfunc struct blkcg *bpf_get_blkcg(struct cgroup_subsys_state *css)
> > +__bpf_kfunc void bpf_put_blkcg(struct blkcg *blkcg)
> > +__bpf_kfunc void bpf_blkcg_flush_stats(struct blkcg *blkcg)
> 
> I wonder whether making the above deal with css's would make more sense so
> that we don't end up with per-subsystem iterators. If casting to per-subsys
> type is necessary, we can provide RCU protected cast kfucns.
> 

Hi Tejun, (sorry for asking dumb questions) is the concern you have is that with
the current approach, we will have get_root/get/put kfuncs for each subsystem or
something else? Also how will the current approach leads to per-subsystem
iterators?