Re: [PATCH v4 4/4] mm: thp: reparent the split queue during memcg offline

[Qi Zheng]

Hi Shakeel,

On 10/8/25 1:56 AM, Shakeel Butt wrote:
> On Sat, Oct 04, 2025 at 12:53:18AM +0800, Qi Zheng wrote:
> > From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
> >
> > Similar to list_lru, the split queue is relatively independent and does
> > not need to be reparented along with objcg and LRU folios (holding
> > objcg lock and lru lock). So let's apply the similar mechanism as list_lru
> > to reparent the split queue separately when memcg is offine.
> >
> > This is also a preparation for reparenting LRU folios.
> >
> > Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
> > ---
> >   include/linux/huge_mm.h |  4 +++
> >   mm/huge_memory.c        | 54 +++++++++++++++++++++++++++++++++++++++++
> >   mm/memcontrol.c         |  1 +
> >   3 files changed, 59 insertions(+)
> >
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index f327d62fc9852..0c211dcbb0ec1 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -417,6 +417,9 @@ static inline int split_huge_page(struct page *page)
> >   	return split_huge_page_to_list_to_order(page, NULL, ret);
> >   }
> >   void deferred_split_folio(struct folio *folio, bool partially_mapped);
> > +#ifdef CONFIG_MEMCG
> > +void reparent_deferred_split_queue(struct mem_cgroup *memcg);
> > +#endif
> >   
> >   void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
> >   		unsigned long address, bool freeze);
> > @@ -611,6 +614,7 @@ static inline int try_folio_split(struct folio *folio, struct page *page,
> >   }
> >   
> >   static inline void deferred_split_folio(struct folio *folio, bool partially_mapped) {}
> > +static inline void reparent_deferred_split_queue(struct mem_cgroup *memcg) {}
> >   #define split_huge_pmd(__vma, __pmd, __address)	\
> >   	do { } while (0)
> >   
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 59ddebc9f3232..b5eea2091cdf6 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -1099,6 +1099,11 @@ static struct deferred_split *memcg_split_queue(int nid, struct mem_cgroup *memc
> >   {
> >   	return memcg ? &memcg->deferred_split_queue : split_queue_node(nid);
> >   }
> > +
> > +static bool memcg_is_dying(struct mem_cgroup *memcg)
> > +{
> > +	return memcg ? css_is_dying(&memcg->css) : false;
> > +}
>
> Please move the above function to include/linux/memcontrol.h

OK, will do.

> With that, please add:
>
> Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>

Thanks!

>