From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 2/3] mm/memcg: set pos to prev unconditionally
Date: Wed, 30 Mar 2022 14:22:05 +0000
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References: <20220225003437.12620-1-richard.weiyang@gmail.com>
 <20220225003437.12620-3-richard.weiyang@gmail.com>
 <YkNUZYrSHPjJ1XOb@cmpxchg.org>
 <20220330004750.fx4jr4bnehz4ynpf@master>
 <YkRIUbEGHVIbVRNO@cmpxchg.org>
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To: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
Cc: Wei Yang <richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org

On Wed, Mar 30, 2022 at 08:08:49AM -0400, Johannes Weiner wrote:
>On Wed, Mar 30, 2022 at 12:47:50AM +0000, Wei Yang wrote:
>> Something like this?
>> 
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index eed9916cdce5..5d433b79ba47 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -1005,9 +1005,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
>>  	if (!root)
>>  		root = root_mem_cgroup;
>>  
>> -	if (prev && !reclaim)
>> -		pos = prev;
>> -
>>  	rcu_read_lock();
>>  
>>  	if (reclaim) {
>> @@ -1033,6 +1030,8 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
>>  			 */
>>  			(void)cmpxchg(&iter->position, pos, NULL);
>>  		}
>> +	} else if (prev) {
>> +		pos = prev;
>>  	}
>>  
>>  	if (pos)
>
>Yep!

Sure, I would prepare a v2.

BTW, do you have some comment on patch 3?

-- 
Wei Yang
Help you, Help me