Re: [PATCH] mm/buddy: get the allownodes for dump at once

[Gavin Shan <shangw@linux.vnet.ibm.com>]

>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index 7892f84..211004e 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -2765,11 +2765,19 @@ out:
>>   */
>>  void show_free_areas(unsigned int filter)
>>  {
>> -	int cpu;
>> +	int nid, cpu;
>> +	nodemask_t allownodes;
>>  	struct zone *zone;
>>  
>
>I saw this added to the -mm tree today, but it has to be nacked with 
>apologies for not seeing the patch on the mailing list earlier.
>

Thanks, David.

>show_free_areas() is called by the oom killer, so we know two things: it 
>can be called potentially very deep in the callchain and current is out of 
>memory.  Both are killers for this patch since you're allocating 
>nodemask_t on the stack here which could cause an overflow and because you 
>can't easily fix that case with NODEMASK_ALLOC() since it allocates slab 
>with GFP_KERNEL when we we're oom, which would simply suppress vital 
>meminfo from being shown.
>

I'm not sure it's the possible to resolve the concerns with "static" here
since "allownodes" will be cleared for each call to show_free_areas().

	static nodemask_t allownodes;

Thanks,
Gavin 

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