linux-kernel - Re: [PATCH] mm: memcontrol: fix percpu vmstats and vmevents flush

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Date:   Fri, 30 Aug 2019 07:49:31 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Roman Gushchin <guro@...com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] mm: memcontrol: fix percpu vmstats and vmevents flush

On Thu 29-08-19 13:31:10, Shakeel Butt wrote:
> Instead of using raw_cpu_read() use per_cpu() to read the actual data of
> the corresponding cpu otherwise we will be reading the data of the
> current cpu for the number of online CPUs.
> 
> Fixes: bb65f89b7d3d ("mm: memcontrol: flush percpu vmevents before releasing memcg")
> Fixes: c350a99ea2b1 ("mm: memcontrol: flush percpu vmstats before releasing memcg")
> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
> Cc: Roman Gushchin <guro@...com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Vladimir Davydov <vdavydov.dev@...il.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: <stable@...r.kernel.org>

Ups, missed that when reviewing. Sorry about that.

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
> 
> Note: The buggy patches were marked for stable therefore adding Cc to
> stable.
> 
>  mm/memcontrol.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 26e2999af608..f4e60ee8b845 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3271,7 +3271,7 @@ static void memcg_flush_percpu_vmstats(struct mem_cgroup *memcg)
>  
>  	for_each_online_cpu(cpu)
>  		for (i = 0; i < MEMCG_NR_STAT; i++)
> -			stat[i] += raw_cpu_read(memcg->vmstats_percpu->stat[i]);
> +			stat[i] += per_cpu(memcg->vmstats_percpu->stat[i], cpu);
>  
>  	for (mi = memcg; mi; mi = parent_mem_cgroup(mi))
>  		for (i = 0; i < MEMCG_NR_STAT; i++)
> @@ -3286,8 +3286,8 @@ static void memcg_flush_percpu_vmstats(struct mem_cgroup *memcg)
>  
>  		for_each_online_cpu(cpu)
>  			for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
> -				stat[i] += raw_cpu_read(
> -					pn->lruvec_stat_cpu->count[i]);
> +				stat[i] += per_cpu(
> +					pn->lruvec_stat_cpu->count[i], cpu);
>  
>  		for (pi = pn; pi; pi = parent_nodeinfo(pi, node))
>  			for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
> @@ -3306,8 +3306,8 @@ static void memcg_flush_percpu_vmevents(struct mem_cgroup *memcg)
>  
>  	for_each_online_cpu(cpu)
>  		for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
> -			events[i] += raw_cpu_read(
> -				memcg->vmstats_percpu->events[i]);
> +			events[i] += per_cpu(memcg->vmstats_percpu->events[i],
> +					     cpu);
>  
>  	for (mi = memcg; mi; mi = parent_mem_cgroup(mi))
>  		for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
> -- 
> 2.23.0.187.g17f5b7556c-goog
> 

-- 
Michal Hocko
SUSE Labs