Re: [PATCH v2 20/28] mm: zswap: prevent lruvec release in zswap_folio_swapin()

[Johannes Weiner]

On Wed, Dec 17, 2025 at 03:27:44PM +0800, Qi Zheng wrote:
> From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> 
> In the near future, a folio will no longer pin its corresponding
> memory cgroup. So an lruvec returned by folio_lruvec() could be
> released without the rcu read lock or a reference to its memory
> cgroup.
> 
> In the current patch, the rcu read lock is employed to safeguard
> against the release of the lruvec in zswap_folio_swapin().
> 
> This serves as a preparatory measure for the reparenting of the
> LRU pages.
> 
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Acked-by: Nhat Pham <nphamcs@xxxxxxxxx>
> Reviewed-by: Chengming Zhou <chengming.zhou@xxxxxxxxx>
> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
> Reviewed-by: Harry Yoo <harry.yoo@xxxxxxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>

Btw, it would make the series shorter if you combined the changes to
workingset.c, zswap.c etc. It should still be easy to review as long
as you just stick to making folio_memcg(), folio_lruvec() calls safe.