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	2015-12-03 00:40 +0100
Message-ID	<qBpaa-5uf-11@gated-at.bofh.it> (permalink)
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On Wed, Dec 2, 2015 at 4:21 PM, Toshi Kani <toshi.kani@hpe.com> wrote:
> On Wed, 2015-12-02 at 10:43 -0700, Toshi Kani wrote:
>> On Tue, 2015-12-01 at 19:45 -0800, Dan Williams wrote:
>> > On Tue, Dec 1, 2015 at 6:19 PM, Toshi Kani <toshi.kani@hpe.com> wrote:
>> > > On Mon, 2015-11-30 at 14:08 -0800, Dan Williams wrote:
>  :
>> > > >
>> > > > Hey Toshi,
>> > > >
>> > > > I ended up fixing this differently with follow_pmd_devmap() introduced
>> > > > in this series:
>> > > >
>> > > > https://lists.01.org/pipermail/linux-nvdimm/2015-November/003033.html
>> > > >
>> > > > Does the latest libnvdimm-pending branch [1] pass your test case?
>> > >
>> > > Hi Dan,
>> > >
>> > > I ran several test cases, and they all hit the case "pfn not in memmap" in
>> > > __dax_pmd_fault() during mmap(MAP_POPULATE).  Looking at the dax.pfn,
>> > > PFN_DEV is set but PFN_MAP is not.  I have not looked into why, but I
>> > > thought I let you know first.  I've also seen the test thread got hung up
>> > > at the end sometime.
>> >
>> > That PFN_MAP flag will not be set by default for NFIT-defined
>> > persistent memory.  See pmem_should_map_pages() for pmem namespaces
>> > that will have it set by default, currently only e820 type-12 memory
>> > ranges.
>> >
>> > NFIT-defined persistent memory can have a memmap array dynamically
>> > allocated by setting up a pfn device (similar to setting up a btt).
>> > We don't map it by default because the NFIT may describe hundreds of
>> > gigabytes of persistent and the overhead of the memmap may be too
>> > large to locate the memmap in ram.
>>
>> Oh, I see.  I will setup the memmap array and run the tests again.
>
> I setup a pfn device, and ran a few test cases again.  Yes, it solved the
> PFN_MAP issue.  However, I am no longer able to allocate FS blocks aligned by
> 2MB, so PMD faults fall back to PTE.  They are off by 2 pages, which I suspect
> due to the pfn metadata.If I pass a 2MB-aligned+2pages virtual address to
> mmap(MAP_POPULATE), the mmap() call gets hung up.

Ok, I need to switch over from my memmap=ss!nn config.  We just need
to pad the info block reservation to 2M.  As for the MAP_POPULATE
hang, I'll take a look.

Right now I'm in the process of rebasing the whole set on top of -mm
which has a pending THP re-works from Kirill.
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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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