Re: [PATCH] mm/hugetlb: fix gigantic page initialization/allocation

Mike Kravetz
2016-02-02T23:17:29Z

On 02/02/2016 02:59 PM, David Rientjes wrote:
> On Tue, 2 Feb 2016, Mike Kravetz wrote:
>
>> Attempting to preallocate 1G gigantic huge pages at boot time with
>> "hugepagesz=1G hugepages=1" on the kernel command line will prevent
>> booting with the following:
>>
>> kernel BUG at mm/hugetlb.c:1218!
>>
>> When mapcount accounting was reworked, the setting of compound_mapcount_ptr
>> in prep_compound_gigantic_page was overlooked. As a result, the validation
>> of mapcount in free_huge_page fails.
>>
>> The "BUG_ON" checks in free_huge_page were also changed to "VM_BUG_ON_PAGE"
>> to assist with debugging.
>>
>> Fixes: af5642a8af ("mm: rework mapcount accounting to enable 4k mapping of THPs")
>> Suggested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
>> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
>
> I'm not sure whether this should have a "From: Naoya Horiguchi" line with
> an accompanying sign-off or not, since Naoya debugged and wrote the actual
> fix to prep_compound_gigantic_page().

I agree. Naoya did debug and provide fix via e-mail exchange. He did not
sign-off and I could not tell if he was going to pursue. My only intention
was to fix ASAP.

More than happy to give Naoya credit.
--
Mike Kravetz

>
> Acked-by: David Rientjes <rientjes@google.com>
>