From: Lu Jialin lujialin4@huawei.com

hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5E8LA CVE: NA

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At present, only when the absolute value of stat_cpu->count exceeds MEMCG_CHARGE_BATCH will it be updated to stat, so there will always be a certain lag difference between stat and the correct value.

In addition, since the partially deleted memcg is still referenced, it will not be freed immediately after it is offline. Although the remaining memcg has released the page, it and the parent's stat will still be not 0 or too large due to the update lag, which leads to the abnormality of the total_<count> parameter in the memory.stat file.

This patch mainly solves the problem of synchronization between memcg's stat and the correct value during the destruction process from two aspects: 1) Perform a flush synchronization operation when memcg is offline 2) For memcg in the process of being destroyed, bypass the threshold judgment when updating vmstats

Signed-off-by: Lu Jialin lujialin4@huawei.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- mm/memcontrol.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2983baf910f4..345a9d159ad8 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -697,7 +697,8 @@ void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val) return;

x = val + __this_cpu_read(memcg->stat_cpu->count[idx]); - if (unlikely(abs(x) > MEMCG_CHARGE_BATCH)) { + if (unlikely(abs(x) > MEMCG_CHARGE_BATCH || + memcg->css.flags & CSS_DYING)) { struct mem_cgroup *mi; struct mem_cgroup_extension *memcg_ext;

@@ -3244,8 +3245,10 @@ static void memcg_flush_percpu_vmstats(struct mem_cgroup *memcg) stat[i] = 0;

for_each_online_cpu(cpu) - for (i = 0; i < MEMCG_NR_STAT; i++) + for (i = 0; i < MEMCG_NR_STAT; i++) { stat[i] += per_cpu(memcg->stat_cpu->count[i], cpu); + per_cpu(memcg->stat_cpu->count[i], cpu) = 0; + }

for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) for (i = 0; i < MEMCG_NR_STAT; i++) @@ -3259,9 +3262,11 @@ static void memcg_flush_percpu_vmstats(struct mem_cgroup *memcg) stat[i] = 0;

for_each_online_cpu(cpu) - for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) + for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) { stat[i] += per_cpu( pn->lruvec_stat_cpu->count[i], cpu); + per_cpu(pn->lruvec_stat_cpu->count[i], cpu) = 0; + }

for (pi = pn; pi; pi = parent_nodeinfo(pi, node)) for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) @@ -3279,9 +3284,11 @@ static void memcg_flush_percpu_vmevents(struct mem_cgroup *memcg) events[i] = 0;

for_each_online_cpu(cpu) - for (i = 0; i < NR_VM_EVENT_ITEMS; i++) + for (i = 0; i < NR_VM_EVENT_ITEMS; i++) { events[i] += per_cpu(memcg->stat_cpu->events[i], cpu); + per_cpu(memcg->stat_cpu->events[i], cpu) = 0; + }

for (mi = memcg; mi; mi = parent_mem_cgroup(mi)) for (i = 0; i < NR_VM_EVENT_ITEMS; i++) @@ -5106,6 +5113,9 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) memcg_offline_kmem(memcg); wb_memcg_offline(memcg);

+ memcg_flush_percpu_vmstats(memcg); + memcg_flush_percpu_vmevents(memcg); + mem_cgroup_id_put(memcg); }