On Thu, Jun 28, 2012 at 02:57:42PM +0200, Michal Hocko wrote:
>On Thu 28-06-12 00:36:07, Gavin Shan wrote:
>> With CONFIG_SPARSEMEM_EXTREME, the root memory section descriptors
>> are allocated by slab or bootmem allocator. Also, the descriptors
>> might have been allocated and initialized during the hotplug path.
>> However, the memory chunk allocated in current implementation wouldn't
>> be put into the available pool if that has been allocated. The situation
>> will lead to memory leak.
>>
>> Signed-off-by: Gavin Shan <shangw@xxxxxxxxxxxxxxxxxx>
>> Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
>
>And again!
>To quote my answers to this patch in previous run:
>"
>I am not saying the bug is not real. It is just that the changelog
>doesn's say how the bug is hit, who is affected and when it has been
>introduced. These is essential for stable.
>"
>
>Does this sound like Reviewed-by? Hell no!
>
Ok. I won't do this again wrongly.
>This changelog btw. doesn't say this either!
>
Here's the changelog that Dave suggested. I just copy & paste it.
--
sparse_index_init() is designed to be safe if two copies of it race. It
uses "index_init_lock" to ensure that, even in the case of a race, only
one CPU will manage to do:
mem_section[root] = section;
However, in the case where two copies of sparse_index_init() _do_ race,
the one that loses the race will leak the "section" that
sparse_index_alloc() allocated for it. This patch fixes that leak.
--
Thanks,
Gavin
>> ---
>> mm/sparse.c | 19 +++++++++++++++++++
>> 1 file changed, 19 insertions(+)
>>
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index 781fa04..a803599 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -75,6 +75,22 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid)
>> return section;
>> }
>>
>> +static void noinline __init_refok sparse_index_free(struct mem_section *section,
>> + int nid)
>> +{
>> + 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);
>> +}
>> +
>> static int __meminit sparse_index_init(unsigned long section_nr, int nid)
>> {
>> static DEFINE_SPINLOCK(index_init_lock);
>> @@ -102,6 +118,9 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
>> mem_section[root] = section;
>> out:
>> spin_unlock(&index_init_lock);
>> + if (ret)
>> + sparse_index_free(section, nid);
>> +
>> return ret;
>> }
>> #else /* !SPARSEMEM_EXTREME */
>> --
>> 1.7.9.5
>>
>
>--
>Michal Hocko
>SUSE Labs
>SUSE LINUX s.r.o.
>Lihovarska 1060/12
>190 00 Praha 9
>Czech Republic
>
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