From: Shakeel Butt <shakeelb@xxxxxxxxxx> Subject: memcg: cleanup racy sum avoidance code We used to have per-cpu memcg and lruvec stats and the readers have to traverse and sum the stats from each cpu. This summing was racy and may expose transient negative values. So, an explicit check was added to avoid such scenarios. Now these stats are moved to rstat infrastructure and are no more per-cpu, so we can remove the fixup for transient negative values. Link: https://lkml.kernel.org/r/20210728012243.3369123-1-shakeelb@xxxxxxxxxx Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx> Acked-by: Roman Gushchin <guro@xxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/memcontrol.h | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) --- a/include/linux/memcontrol.h~memcg-cleanup-racy-sum-avoidance-code +++ a/include/linux/memcontrol.h @@ -977,30 +977,19 @@ static inline void mod_memcg_state(struc static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx) { - long x = READ_ONCE(memcg->vmstats.state[idx]); -#ifdef CONFIG_SMP - if (x < 0) - x = 0; -#endif - return x; + return READ_ONCE(memcg->vmstats.state[idx]); } static inline unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx) { struct mem_cgroup_per_node *pn; - long x; if (mem_cgroup_disabled()) return node_page_state(lruvec_pgdat(lruvec), idx); pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec); - x = READ_ONCE(pn->lruvec_stats.state[idx]); -#ifdef CONFIG_SMP - if (x < 0) - x = 0; -#endif - return x; + return READ_ONCE(pn->lruvec_stats.state[idx]); } static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, _
