[PATCH kernel] powerpc/iommu: Do not call PageTransHuge() on tail pages

[Alexey Kardashevskiy]

On 28/03/17 21:45, Michael Ellerman wrote:
> Alexey Kardashevskiy <aik at ozlabs.ru> writes:
> 
>> The CMA pages migration code does not support compound pages at
>> the moment so it performs few tests before proceeding to actual page
>> migration.
>>
>> One of the tests - PageTransHuge() - has VM_BUG_ON_PAGE(PageTail()) as
>> it should be called on head pages. Since we also test for PageCompound(),
>> and it contains PageTail(), we can simply move PageCompound() in front
>> of PageTransHuge() and therefore avoid possible VM_BUG_ON_PAGE.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>> ---
>>
>> Some of actual POWER8 systems do crash on that BUG_ON.
> 
> So this is:
> 
> Fixes: 2e5bbb5461f1 ("KVM: PPC: Book3S HV: Migrate pinned pages out of CMA")
> 
> And therefore:
> 
> Cc: stable at vger.kernel.org # v4.9+
> 
> ?

May be, first I want to make sure this is enough fix, this is why I
(re)added Balbir in cc list.


-- 
Alexey