Re: [RFC] [PATCH 3/4] Reclaim from groups over their soft limit under memory pressure

[Balbir Singh <balbir@linux.vnet.ibm.com>]

YAMAMOTO Takashi wrote:
>> +/*
>> + * Free all control groups, which are over their soft limit
>> + */
>> +unsigned long mem_cgroup_pushback_groups_over_soft_limit(struct zone **zones,
>> +								gfp_t gfp_mask)
>> +{
>> +	struct mem_cgroup *mem;
>> +	unsigned long nr_pages;
>> +	long long nr_bytes_over_sl;
>> +	unsigned long ret = 0;
>> +	unsigned long flags;
>> +	struct list_head reclaimed_groups;
>>  
>> +	INIT_LIST_HEAD(&reclaimed_groups);
>> +	read_lock_irqsave(&mem_cgroup_sl_list_lock, flags);
>> +	while (!list_empty(&mem_cgroup_sl_exceeded_list)) {
>> +		mem = list_first_entry(&mem_cgroup_sl_exceeded_list,
>> +				struct mem_cgroup, sl_exceeded_list);
>> +		list_move(&mem->sl_exceeded_list, &reclaimed_groups);
>> +		read_unlock_irqrestore(&mem_cgroup_sl_list_lock, flags);
>> +
>> +		nr_bytes_over_sl = res_counter_sl_excess(&mem->res);
>> +		if (nr_bytes_over_sl <= 0)
>> +			goto next;
>> +		nr_pages = (nr_bytes_over_sl >> PAGE_SHIFT);
>> +		ret += try_to_free_mem_cgroup_pages(mem, gfp_mask, nr_pages,
>> +							zones);
>> +next:
>> +		read_lock_irqsave(&mem_cgroup_sl_list_lock, flags);
>> +	}
> 
> what prevents the cgroup 'mem' from disappearing while we are dropping
> mem_cgroup_sl_list_lock?
> 

I thought I had a css_get/put around it, but I don't. Thanks for catching the
problem.

> YAMAMOTO Takashi


-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>