Re: [RFC v5 01/11] mm: Dont assume page-table invariance during faults

[Laurent Dufour]

On 08/08/2017 11:45, Anshuman Khandual wrote:
> On 06/16/2017 11:22 PM, Laurent Dufour wrote:
>> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>>
>> One of the side effects of speculating on faults (without holding
>> mmap_sem) is that we can race with free_pgtables() and therefore we
>> cannot assume the page-tables will stick around.
>>
>> Remove the relyance on the pte pointer.
> 
> Looking into other parts of the series, it seemed like now we have
> sequence lock both at MM and VMA level but then after that we still
> need to take page table lock before handling page faults (in turn
> manipulating PTE which includes swap in paths as well). Is not that
> true ?

Page table locking is still required as several VMAs can reference the same
page table.