Re: [PATCH v2] mm: mglru: fix stale batch updates after memcg reparenting

[Qi Zheng]

On 6/25/26 12:16 PM, Harry Yoo wrote:
>

[...]

> > So lock_batch_lruvec() can be implemented like this:
> >
> > #ifdef CONFIG_MEMCG
> > static struct lruvec *lock_batch_lruvec(struct lruvec *lruvec)
> > {
> >      struct pglist_data *pgdat = lruvec_pgdat(lruvec);
> >      struct mem_cgroup *memcg = lruvec_memcg(lruvec);
> >
> >      rcu_read_lock();
> >
> >      /*
> >       * The memcg can be NULL when the memory controller is disabled.
> >       * Otherwise, the caller keeps the memcg owning @lruvec alive.
> >       */
> >      if (!memcg || !css_is_dying(&memcg->css))
> >          goto lock;
> >
> >      do {
> >          memcg = parent_mem_cgroup(memcg);
> >      } while (memcg && css_is_dying(&memcg->css));
> >      lruvec = mem_cgroup_lruvec(memcg, pgdat);
> >
> > lock:
> >      spin_lock_irq(&lruvec->lru_lock);
> >
> >      return lruvec;
> > }
> > #else
> > static struct lruvec *lock_batch_lruvec(struct lruvec *lruvec)
> > {
> >      lruvec_lock_irq(lruvec);
> >
> >      return lruvec;
> > }
> > #endif
> >
> > Does this make sense?
>
> Yes, looks good to me!

OK, this sync method makes more sense as it doesn't require adding a
new lrugen->reparente. I'll go with this method and update v3.

Hi Barry and Baolin, what do you think? Since the sync method has been
changed, I will temporarily drop your previous Reviewed-by tags in v3. ;)

Thanks,
Qi

>