From: Muchun Song 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 Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo --- mm/migrate.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/migrate.c b/mm/migrate.c index 5169f9717f606..8bcd588c083ca 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -671,6 +671,7 @@ static int __folio_migrate_mapping(struct address_space *mapping, struct lruvec *old_lruvec, *new_lruvec; struct mem_cgroup *memcg; + rcu_read_lock(); memcg = folio_memcg(folio); old_lruvec = mem_cgroup_lruvec(memcg, oldzone->zone_pgdat); new_lruvec = mem_cgroup_lruvec(memcg, newzone->zone_pgdat); @@ -698,6 +699,7 @@ static int __folio_migrate_mapping(struct address_space *mapping, mod_lruvec_state(new_lruvec, NR_FILE_DIRTY, nr); __mod_zone_page_state(newzone, NR_ZONE_WRITE_PENDING, nr); } + rcu_read_unlock(); } local_irq_enable(); -- 2.20.1