linux-kernel - Re: [patch 08/11] mm: memcg: remove needless !mm fixup to init

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Message-ID: <20120710061021.GA6096@kernel>
Date:	Tue, 10 Jul 2012 14:10:21 +0800
From:	Wanpeng Li <liwp.linux@...il.com>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hughd@...gle.com>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Wanpeng Li <liwp.linux@...il.com>
Subject: Re: [patch 08/11] mm: memcg: remove needless !mm fixup to init_mm
 when charging

On Mon, Jul 09, 2012 at 05:20:58PM +0200, Michal Hocko wrote:
>On Thu 05-07-12 02:45:00, Johannes Weiner wrote:
>> It does not matter to __mem_cgroup_try_charge() if the passed mm is
>> NULL or init_mm, it will charge the root memcg in either case.

You can also change the comment in __mem_cgroup_try_charge :

"if so charge the init_mm" => "if so charge the root memcg"

>> 
>> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
>
>Acked-by: Michal Hocko <mhocko@...e.cz>
>
>> ---
>>  mm/memcontrol.c |    5 -----
>>  1 files changed, 0 insertions(+), 5 deletions(-)
>> 
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 418b47d..6fe4101 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -2766,8 +2766,6 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
>>  		ret = 0;
>>  	return ret;
>>  charge_cur_mm:
>> -	if (unlikely(!mm))
>> -		mm = &init_mm;
>>  	ret = __mem_cgroup_try_charge(mm, mask, 1, memcgp, true);
>>  	if (ret == -EINTR)
>>  		ret = 0;
>> @@ -2832,9 +2830,6 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
>>  	if (PageCompound(page))
>>  		return 0;
>>  
>> -	if (unlikely(!mm))
>> -		mm = &init_mm;
>> -
>>  	if (!PageSwapCache(page))
>>  		ret = mem_cgroup_charge_common(page, mm, gfp_mask, type);
>>  	else { /* page is swapcache/shmem */
>> -- 
>> 1.7.7.6
>> 
>
>-- 
>Michal Hocko
>SUSE Labs
>SUSE LINUX s.r.o.
>Lihovarska 1060/12
>190 00 Praha 9    
>Czech Republic
>--
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