Re: [PATCH v2 13/28] mm: migrate: prevent memory cgroup release in folio_migrate_mapping()

[Johannes Weiner]

On Wed, Dec 17, 2025 at 03:27:37PM +0800, Qi Zheng wrote:
> From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> 
> In the near future, a folio will no longer pin its corresponding
> memory cgroup. To ensure safety, it will only be appropriate to
> hold the rcu read lock or acquire a reference to the memory cgroup
> returned by folio_memcg(), thereby preventing it from being released.
> 
> In the current patch, the rcu read lock is employed to safeguard
> against the release of the memory cgroup in folio_migrate_mapping().
> 
> This serves as a preparatory measure for the reparenting of the
> LRU pages.
> 
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
> Reviewed-by: Harry Yoo <harry.yoo@xxxxxxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>