Re: [PATCH v4] mm: mglru: fix stale batch updates after memcg reparenting

[Johannes Weiner <hannes@cmpxchg.org>]

On Fri, Jul 10, 2026 at 02:19:15PM +0800, Qi Zheng wrote:
> On 7/10/26 9:51 AM, Johannes Weiner wrote:
> > On Thu, Jul 02, 2026 at 09:38:41AM +0800, Qi Zheng wrote:
> >> On 7/1/26 11:59 PM, Johannes Weiner wrote:
> >>> lruvec_live_lock_irq()?
> >>
> >> But lruvec_lock_irq() grabs the rcu lock too. :(
> > 
> > Yes, but it's self-explanatory if you put it with those definitions:
> > 
> > static inline void lruvec_lock_irq(struct lruvec *lruvec)
> > {
> >          rcu_read_lock();
> >          spin_lock_irq(&lruvec->lru_lock);
> > }
> > 
> > static struct lruvec *lruvec_live_lock_irq(struct lruvec *lruvec)
> > {
> > 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
> > 
> > 	rcu_read_lock();
> > 	while (unlikely(memcg && css_is_dying(&memcg->css))) {
> > 		memcg = parent_mem_cgroup(memcg);
> > 		lruvec = mem_cgroup_lruvec(memcg, lruvec_pgdat(lruvec));
> > 	}
> > 	spin_lock_irq(&lruvec->lru_lock);
> > }
> 
> All right, should the implementation for !CONFIG_MEMCG be placed here
> too?

Yes. You can just #ifdef, #else the function body itself.

static struct lruvec *lruvec_live_lock_irq()
{
#ifdef CONFIG_MEMCG
	...
#else
	lruvec_lock_irq(lruvec);
	return lruvec;
#endif
}

> Will send the v5.

Thanks.