Re: [PATCH v2 1/2] block: add BPF kfuncs to read blkcg io.stat

[Tejun Heo]

Hello,

On Tue, Aug 18, 2026 at 04:01:58PM -0700, Ziyang Men wrote:
> On Tue, Aug 18, 2026 at 12:42:54PM -1000, Tejun Heo wrote:
> > On Tue, Aug 18, 2026 at 03:31:29PM -0700, Ziyang Men wrote:
> > > Ok I will add the casts bpf_get_blkcg() and bpf_put_blkcg(), and remove the
> > > check of css->ss in above functoins.
> > 
> > RCU_PROTECTED is probably better than get/put().
> 
> Yes we can make the blkcg* RCU_PROTECTED but then the bpf_blkcg_flush_stats()
> needs to take the @cgroup* since it is SLEEPABLE. Does this work for you?

Do we really need that function? css_rstat_flush() is already exposed and
css can already be obtained, right? blkcg_fill_root_iostat() is just
accessing system-wide bdev stats, which you probably don't need to begin
with or if necessary just access through bdevs.

Thanks.

-- 
tejun