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Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping

From Dan Williams <dan.j.williams@intel.com>
Newsgroups linux.kernel
Subject Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping
Date 2015-12-02 22:00 +0100
Message-ID <qBmFl-3Od-35@gated-at.bofh.it> (permalink)
References (8 earlier) <qBkWS-2Tg-29@gated-at.bofh.it> <qBkWS-2Tg-27@gated-at.bofh.it> <qBl6y-2Xu-1@gated-at.bofh.it> <qBlJg-3cy-5@gated-at.bofh.it> <qBmvE-3Jz-25@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Wed, Dec 2, 2015 at 1:37 PM, Toshi Kani <toshi.kani@hpe.com> wrote:
> On Wed, 2015-12-02 at 11:57 -0800, Dan Williams wrote:
[..]
>> The whole point of __get_user_page_fast() is to avoid the overhead of
>> taking the mm semaphore to access the vma.  _PAGE_SPECIAL simply tells
>> __get_user_pages_fast that it needs to fallback to the
>> __get_user_pages slow path.
>
> I see.  Then, I think gup_huge_pmd() can simply return 0 when !pfn_valid(),
> instead of VM_BUG_ON.

Is pfn_valid() a reliable check?  It seems to be based on a max_pfn
per node... what happens when pmem is located below that point.  I
haven't been able to convince myself that we won't get false
positives, but maybe I'm missing something.
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Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-11-30 23:10 +0100
  Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani <toshi.kani@hpe.com> - 2015-12-02 02:30 +0100
    Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-12-02 04:50 +0100
      Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani <toshi.kani@hpe.com> - 2015-12-02 17:50 +0100
        Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-12-02 18:40 +0100
          Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-12-02 19:10 +0100
            Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani <toshi.kani@hpe.com> - 2015-12-02 19:40 +0100
              Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani <toshi.kani@hpe.com> - 2015-12-02 20:10 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani <toshi.kani@hpe.com> - 2015-12-02 20:20 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-12-02 21:00 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani <toshi.kani@hpe.com> - 2015-12-02 21:50 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-12-02 22:00 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani <toshi.kani@hpe.com> - 2015-12-02 22:10 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-12-04 00:50 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani <toshi.kani@hpe.com> - 2015-12-04 17:10 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dave Hansen <dave.hansen@intel.com> - 2015-12-02 23:10 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dave Hansen <dave.hansen@intel.com> - 2015-12-02 23:10 +0100
                Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-12-02 23:10 +0100
              Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-12-02 20:10 +0100
        Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani <toshi.kani@hpe.com> - 2015-12-03 00:30 +0100
          Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Dan Williams <dan.j.williams@intel.com> - 2015-12-03 00:40 +0100

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