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 mem_cgroup_swap_full(). This serves as a preparatory measure for the reparenting of the LRU pages. Signed-off-by: Muchun Song Signed-off-by: Qi Zheng --- mm/memcontrol.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index aa8945c4ee383..4b3c7d4f346b5 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5275,17 +5275,21 @@ bool mem_cgroup_swap_full(struct folio *folio) if (do_memsw_account()) return false; - memcg = folio_memcg(folio); - if (!memcg) + if (!folio_memcg_charged(folio)) return false; + rcu_read_lock(); + memcg = folio_memcg(folio); for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) { unsigned long usage = page_counter_read(&memcg->swap); if (usage * 2 >= READ_ONCE(memcg->swap.high) || - usage * 2 >= READ_ONCE(memcg->swap.max)) + usage * 2 >= READ_ONCE(memcg->swap.max)) { + rcu_read_unlock(); return true; + } } + rcu_read_unlock(); return false; } -- 2.20.1