Hi Tejun,
On Wed, Aug 19, 2026 at 10:43:51AM -1000, Tejun Heo wrote:
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.
Yes the css_rstat_flush() is exposed but currently it is marked as SLEEPABLE, so
it doesn't accept a RCU_PROTECTED css we proposed. This is not a problem for cpu
ones since &cgrp->self is a trusted pointer.
Best,
Ziyang
Thanks.
--
tejun
