Re: kernel BUG in munlock_vma_pages_range

[Sasha Levin <sasha.levin@oracle.com>]

On 12/09/2013 12:12 PM, Vlastimil Babka wrote:
> On 12/09/2013 06:05 PM, Sasha Levin wrote:
>> On 12/09/2013 04:34 AM, Vlastimil Babka wrote:
>>> Hello, I will look at it, thanks.
>>> Do you have specific reproduction instructions?
>>
>> Not really, the fuzzer hit it once and I've been unable to trigger it again. Looking at
>> the piece of code involved it might have had something to do with hugetlbfs, so I'll crank
>> up testing on that part.
>
> Thanks. Do you have trinity log and the .config file? I'm currently unable to even boot linux-next
> with my config/setup due to a GPF.
> Looking at code I wouldn't expect that it could encounter a tail page, without first encountering a
> head page and skipping the whole huge page. At least in THP case, as TLB pages should be split when
> a vma is split. As for hugetlbfs, it should be skipped for mlock/munlock operations completely. One
> of these assumptions is probably failing here...

If it helps, I've added a dump_page() in case we hit a tail page there and got:

[  980.172299] page:ffffea003e5e8040 count:0 mapcount:1 mapping:          (null) index:0
x0
[  980.173412] page flags: 0x2fffff80008000(tail)

I can also add anything else in there to get other debug output if you think of something else useful.


Thanks,
Sasha

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