Re: [PATCH v2 2/3] mm/sparse: fix possible memory leak

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

On Thu, Jun 28, 2012 at 02:34:29PM -0700, David Rientjes wrote:
>On Thu, 28 Jun 2012, Gavin Shan wrote:
>
>> >> +{
>> >> +	unsigned long size = SECTIONS_PER_ROOT *
>> >> +			     sizeof(struct mem_section);
>> >> +
>> >> +	if (!section)
>> >> +		return;
>> >> +
>> >> +	if (slab_is_available())
>> >> +		kfree(section);
>> >> +	else
>> >> +		free_bootmem_node(NODE_DATA(nid),
>> >> +			virt_to_phys(section), size);
>> >
>> >Did you check what happens here if !node_state(nid, N_HIGH_MEMORY)?
>> >
>> 
>> I'm sorry that I'm not catching your point. Please explain for more
>> if necessary.
>> 
>
>I'm asking specifically about the free_bootmem_node(NODE_DATA(nid), ...).
>

Thanks for pointing it out, David.

>If this section was allocated in sparse_index_alloc() before 
>slab_is_available() with alloc_bootmem_node() and nid is not in 
>N_HIGH_MEMORY, will alloc_bootmem_node() fallback to any node or return 
>NULL?
>

Yes, you're right that bootmem allocator will try other nodes if the
specified node can't accomodate the memory allocation. So it's not
safe to free memory by free_bootmem_node().

>If it falls back to any node, is it safe to try to free that section by 
>passing NODE_DATA(nid) here when it wasn't allocated on that nid?
>

I think free_bootmem() should be used here :-)

Thanks,
Gavin

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