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

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Date:   Tue, 8 Aug 2017 15:15:50 +0530
From:   Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:     Laurent Dufour <ldufour@...ux.vnet.ibm.com>,
        paulmck@...ux.vnet.ibm.com, peterz@...radead.org,
        akpm@...ux-foundation.org, kirill@...temov.name,
        ak@...ux.intel.com, mhocko@...nel.org, dave@...olabs.net,
        jack@...e.cz, Matthew Wilcox <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        haren@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
        npiggin@...il.com, bsingharora@...il.com,
        Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [RFC v5 01/11] mm: Dont assume page-table invariance during
 faults

On 06/16/2017 11:22 PM, Laurent Dufour wrote:
> From: Peter Zijlstra <peterz@...radead.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 ?