On Wed, Mar 04, 2020 at 06:22:21PM +0100, Greg Kroah-Hartman wrote:
> On Wed, Mar 04, 2020 at 12:05:43PM -0500, Tejun Heo wrote:
> > Hello,
> >
> > It might be better to put this patch at the end rather than in the
> > middle so that when this patch is applied things are actually fixed.
> >
> > > +struct bdi_rcu_device {
> > > + struct device dev;
> > > + struct rcu_head rcu_head;
> > > +};
> >
> > (cc'ing Greg)
> >
> > Greg, block layer switches association between backing_device_info and
> > its struct device and needs to protect it with RCU. Yufen did so by
> > introducing a wrapping struct around struct device like above. Do you
> > think it'd make sense to just embed rcu_head into struct device and
> > let put_device() to RCU release by default?
>
> Ugh, I was dreading the fact that this day might sometime come...
>
> In theory, the reference counting for struct device shouldn't need to
> use rcu at all, right? what is driving the need to use rcu for
> backing_device_info? Are these being destroyed/used so often that rcu
> really is the best solution and the existing reference counting doesn't
> work properly?
>
> Some context is needed here.
Ah, would help if I just read the whole patch series, that helps...
Something is odd if kobj->name is the problem here, let me look at the
patches in full.
thanks,
greg k-h
