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

From	Laurent Dufour <ldufour@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: [RFC v5 01/11] mm: Dont assume page-table invariance during faults
Date	2017-08-08 14:20 +0200
Message-ID	<ucbEm-8gS-11@gated-at.bofh.it> (permalink)
References	<tT3Hj-3lN-3@gated-at.bofh.it> <tT3Hl-3lN-39@gated-at.bofh.it> <uc9jd-69T-15@gated-at.bofh.it>
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On 08/08/2017 11:45, Anshuman Khandual wrote:
> On 06/16/2017 11:22 PM, Laurent Dufour wrote:
>> From: Peter Zijlstra <peterz@infradead.org>
>>
>> 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.

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Re: [RFC v5 01/11] mm: Dont assume page-table invariance during  faults Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-08-08 11:50 +0200
  Re: [RFC v5 01/11] mm: Dont assume page-table invariance during  faults Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-08-08 14:20 +0200

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