Subject: Re: [PATCH v7 1/2] Always free struct memcg through schedule_work()

From: Glauber Costa <[email-masked]>
Date: Fri, 25 May 2012 13:51:22 +0400

On 05/25/2012 01:50 PM, Michal Hocko wrote:
> On Fri 25-05-12 13:32:07, Glauber Costa wrote:
>> Right now we free struct memcg with kfree right after a
>> rcu grace period, but defer it if we need to use vfree() to get
>> rid of that memory area. We do that by need, because we need vfree
>> to be called in a process context.
>>
>> This patch unifies this behavior, by ensuring that even kfree will
>> happen in a separate thread. The goal is to have a stable place to
>> call the upcoming jump label destruction function outside the realm
>> of the complicated and quite far-reaching cgroup lock (that can't be
>> held when calling neither the cpu_hotplug.lock nor the jump_label_mutex)
>>
>> Signed-off-by: Glauber Costa<[email-masked]>
>> Acked-by: Kamezawa Hiroyuki<[email-masked]>
>
> Acked-by: Michal Hocko<[email-masked]>
>
> Just one comment below
>
>> CC: Tejun Heo<[email-masked]>
>> CC: Li Zefan<[email-masked]>
>> CC: Johannes Weiner<[email-masked]>
>> CC: Michal Hocko<[email-masked]>
>> CC: Andrew Morton<akpm-de/[email-masked]>
>> ---
>>   mm/memcontrol.c |   24 +++++++++++++-----------
>>   1 files changed, 13 insertions(+), 11 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 932a734..0b4b4c8 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
> [...]
>> @@ -4826,23 +4826,28 @@ out_free:
>>   }
>>
>>   /*
>> - * Helpers for freeing a vzalloc()ed mem_cgroup by RCU,
>> + * Helpers for freeing a kmalloc()ed/vzalloc()ed mem_cgroup by RCU,
>>    * but in process context.  The work_freeing structure is overlaid
>>    * on the rcu_freeing structure, which itself is overlaid on memsw.
>>    */
>> -static void vfree_work(struct work_struct *work)
>> +static void free_work(struct work_struct *work)
>>   {
>>   	struct mem_cgroup *memcg;
>> +	int size = sizeof(struct mem_cgroup);
>>
>>   	memcg = container_of(work, struct mem_cgroup, work_freeing);
>> -	vfree(memcg);
>> +	if (size<  PAGE_SIZE)
>
> What about
> 	if (is_vmalloc_addr(memcg))
>> +		kfree(memcg);
>> +	else
>> +		vfree(memcg);
>>   }
>
Could be, but I believe this one is already in Andrew's tree from last 
submission (might be wrong)