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

From Anshuman Khandual <khandual@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure
Date 2017-08-30 05:50 +0200
Message-ID <uk2aR-38o-3@gated-at.bofh.it> (permalink)
References <ufB9f-2BN-5@gated-at.bofh.it> <ufBiW-2Hx-21@gated-at.bofh.it> <uiTsZ-8fp-1@gated-at.bofh.it> <ujJBg-8hK-9@gated-at.bofh.it> <ujNvc-2sE-23@gated-at.bofh.it>
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On 08/29/2017 05:34 PM, 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;

This makes more sense. We are backing off from speculative path
because struct anon_vma has not been created for this anonymous
vma and we cannot do that without holding mmap_sem. This should
have nothing to do with vma->vm_ops availability.

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Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-08-27 02:20 +0200
  Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Peter Zijlstra <peterz@infradead.org> - 2017-08-28 11:40 +0200
    Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-08-28 23:30 +0200
      Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Andi Kleen <ak@linux.intel.com> - 2017-08-29 00:40 +0200
        Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Peter Zijlstra <peterz@infradead.org> - 2017-08-29 10:20 +0200
      Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Peter Zijlstra <peterz@infradead.org> - 2017-08-29 10:40 +0200
        Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Peter Zijlstra <peterz@infradead.org> - 2017-08-29 13:30 +0200
          Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-08-30 00:00 +0200
            Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Peter Zijlstra <peterz@infradead.org> - 2017-08-30 08:20 +0200
  Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-08-29 10:00 +0200
    Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Peter Zijlstra <peterz@infradead.org> - 2017-08-29 14:10 +0200
      Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-08-29 15:20 +0200
        Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Peter Zijlstra <peterz@infradead.org> - 2017-08-29 15:50 +0200
          Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-08-30 07:10 +0200
            Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Peter Zijlstra <peterz@infradead.org> - 2017-08-30 08:00 +0200
              Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-08-30 11:40 +0200
                Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-08-31 09:00 +0200
                Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Peter Zijlstra <peterz@infradead.org> - 2017-08-31 09:40 +0200
            Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-08-30 12:00 +0200
      Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-08-30 05:50 +0200
  Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Anshuman Khandual <khandual@linux.vnet.ibm.com> - 2017-08-30 07:30 +0200
  Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure Laurent Dufour <ldufour@linux.vnet.ibm.com> - 2017-08-30 11:00 +0200

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