From: Hui Zhu get_non_dying_memcg_start() redirects the stat updates of a dying memcg to its closest non-dying ancestor, but only on cgroup v1; on cgroup v2 the stats keep being accounted to the dying memcg itself. The previous patch restored lruvec_page_state_local() in count_shadow_nodes(), which reads those state_locals on cgroup v2 too, so apply the redirection to all hierarchies. Offlining is rare, so the added cost on the stat update fast path is limited to an rcu_read_lock() and a css_is_dying() check; the upward walk happens only while a memcg is dying. Signed-off-by: Hui Zhu --- mm/memcontrol.c | 30 +++++------------------------- 1 file changed, 5 insertions(+), 25 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8319ad8c5c23..b3d1ac3fe0aa 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -805,20 +805,14 @@ static long memcg_state_val_in_pages(int idx, long val) return val < 0 ? -res : res; } -#ifdef CONFIG_MEMCG_V1 /* - * Used in mod_memcg_state() and mod_memcg_lruvec_state() to avoid race with - * reparenting of non-hierarchical state_locals. + * Used in mod_memcg_state() and mod_memcg_lruvec_state() to avoid race + * with reparenting of non-hierarchical state_locals. Offlining a + * memcg is rare, so do the redirection for all cgroup hierarchies. */ -static inline struct mem_cgroup *get_non_dying_memcg_start(struct mem_cgroup *memcg, - bool *rcu_locked) +static inline struct mem_cgroup * +get_non_dying_memcg_start(struct mem_cgroup *memcg, bool *rcu_locked) { - /* Rebinding can cause this value to be changed at runtime */ - if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) { - *rcu_locked = false; - return memcg; - } - rcu_read_lock(); *rcu_locked = true; @@ -830,22 +824,8 @@ static inline struct mem_cgroup *get_non_dying_memcg_start(struct mem_cgroup *me static inline void get_non_dying_memcg_end(bool rcu_locked) { - if (!rcu_locked) - return; - rcu_read_unlock(); } -#else -static inline struct mem_cgroup *get_non_dying_memcg_start(struct mem_cgroup *memcg, - bool *rcu_locked) -{ - return memcg; -} - -static inline void get_non_dying_memcg_end(bool rcu_locked) -{ -} -#endif static void __mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx, long val) -- 2.53.0