Re: [Resend PATCH 2/6] mm/memcg: remove useless check on page->mem_cgroup

[Alex Shi <alex.shi@linux.alibaba.com>]

在 2020/8/11 下午7:30, Michal Hocko 写道:
> subject line looks like a left over. It doesn't match the path. Did you
> mean
> memcg: bail out early from swap accounting when memcg is disabled?

It's much better, Thanks for correction!

> 
> Btw. if this patch was first in the series then you wouldn't need to
> mention the warnings that would trigger based on your previous patch.
> I am fine with both ways but mentioning the warning is usefule.

Right. but the patch is very simple,  w/o warning message doesn't cuase trouble.
So, removing the 'and keep WARN_ON monitor' make sense too.

Do I need a resend for the commit log change?

Thanks a lot!
Alex

> 
> On Tue 11-08-20 19:10:28, Alex Shi wrote:
>> If we disabled memcg by cgroup_disable=memory, the swap charges are
>> still called. Let's return from the funcs earlier and keep WARN_ON
>> monitor.
>>
>> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
>> Reviewed-by: Roman Gushchin <guro@fb.com>
>> Acked-by: Michal Hocko <mhocko@suse.com>
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: cgroups@vger.kernel.org
>> Cc: linux-mm@kvack.org
>> Cc: linux-kernel@vger.kernel.org
>> ---
>>  mm/memcontrol.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 299382fc55a9..419cf565f40b 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
>>  	VM_BUG_ON_PAGE(PageLRU(page), page);
>>  	VM_BUG_ON_PAGE(page_count(page), page);
>>  
>> +	if (mem_cgroup_disabled())
>> +		return;
>> +
>>  	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
>>  		return;
>>  
>> @@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
>>  	struct mem_cgroup *memcg;
>>  	unsigned short oldid;
>>  
>> +	if (mem_cgroup_disabled())
>> +		return 0;
>> +
>>  	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))
>>  		return 0;
>>  
>> -- 
>> 1.8.3.1
>