Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure

[Laurent Dufour]

On 29/08/2017 14:04, Peter Zijlstra wrote:
> On Tue, Aug 29, 2017 at 09:59:30AM +0200, Laurent Dufour wrote:
>> On 27/08/2017 02:18, Kirill A. Shutemov wrote:
>>>> +
>>>> +	if (unlikely(!vma->anon_vma))
>>>> +		goto unlock;
>>>
>>> It deserves a comment.
>>
>> You're right I'll add it in the next version.
>> For the record, the root cause is that __anon_vma_prepare() requires the
>> mmap_sem to be held because vm_next and vm_prev must be safe.
> 
> But should that test not be:
> 
> 	if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma))
> 		goto unlock;
> 
> Because !anon vmas will never have ->anon_vma set and you don't want to
> exclude those.

Yes in the case we later allow non anonymous vmas to be handled.
Currently only anonymous vmas are supported so the check is good enough,
isn't it ?