Re: [PATCH] mm/memcg: wrap mem_cgroup_from_css function

From: Wanpeng Li
Date: Wed Jul 18 2012 - 21:31:31 EST

On Wed, Jul 18, 2012 at 02:36:12PM -0700, Andrew Morton wrote:
>On Wed, 18 Jul 2012 11:05:30 +0800
>Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx> wrote:
>> wrap mem_cgroup_from_css function to clarify get mem cgroup
>> from cgroup_subsys_state.
>This certainly adds clarity.
>But it also adds a little more type-safety - these container_of() calls
>can be invoked against *any* struct which has a field called "css".
>With your patch, we add a check that the code is indeed using a
>cgroup_subsys_state*. A small thing, but it's all good.
>I changed the patch title to the more idiomatic "memcg: add
>mem_cgroup_from_css() helper" and rewrote the changelog to
>: Add a mem_cgroup_from_css() helper to replace open-coded invokations of
>: container_of(). To clarify the code and to add a little more type safety.
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -396,6 +396,12 @@ static void mem_cgroup_put(struct mem_cgroup *memcg);
>> #include <net/sock.h>
>> #include <net/ip.h>
>> +static inline
>> +struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *s)
>> +{
>> + return container_of(s, struct mem_cgroup, css);
>> +}
>And with great self-control, I avoided renaming this to
>memcg_from_css(). Sigh. I guess all that extra typing has cardio

Thank you for your time, Andrew. :-)

Thanks & Best Regards,
Wanpeng Li

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