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Re: [RFC PATCH] dax: add badblocks check to Device DAX

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On Wed, May 3, 2017 at 8:31 AM, Toshi Kani <toshi.kani@hpe.com> wrote:
> This is a RFC patch for seeking suggestions.  It adds support of
> badblocks check in Device DAX by using region-level badblocks list.
> This patch is only briefly tested.
>
> device_dax is a well-isolated self-contained module as it calls
> alloc_dax() with dev_dax, which is private to device_dax.  For
> checking badblocks, it needs to call dax_pmem to check with
> region-level badblocks.
>
> This patch attempts to keep device_dax self-contained.  It adds
> check_error() to dax_operations, and dax_check_error() as a stub
> with *dev_dax and *dev pointers to convey it to dax_pmem.  I am
> wondering if this is the right direction, or we should change the
> modularity to let dax_pmem call alloc_dax() with its dax_pmem (or
> I completely missed something).

The problem is that device-dax guarantees a given fault granularity.
To make that guarantee we can't fallback from 1G or 2M mappings due to
an error. We also can't reasonably go the other way and fail mappings
that contain a badblock because that would change the blast radius of
a media error to the fault size.

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[RFC PATCH] dax: add badblocks check to Device DAX Toshi Kani <toshi.kani@hpe.com> - 2017-05-03 17:40 +0200
  Re: [RFC PATCH] dax: add badblocks check to Device DAX Dan Williams <dan.j.williams@intel.com> - 2017-05-03 18:00 +0200
    Re: [RFC PATCH] dax: add badblocks check to Device DAX "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2017-05-03 18:10 +0200
      Re: [RFC PATCH] dax: add badblocks check to Device DAX Dan Williams <dan.j.williams@intel.com> - 2017-05-03 18:40 +0200
        Re: [RFC PATCH] dax: add badblocks check to Device DAX "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2017-05-03 20:50 +0200
          Re: [RFC PATCH] dax: add badblocks check to Device DAX Dan Williams <dan.j.williams@intel.com> - 2017-05-03 23:50 +0200
            Re: [RFC PATCH] dax: add badblocks check to Device DAX Dave Jiang <dave.jiang@intel.com> - 2017-05-04 00:00 +0200
            Re: [RFC PATCH] dax: add badblocks check to Device DAX "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2017-05-04 00:50 +0200
              Re: [RFC PATCH] dax: add badblocks check to Device DAX Dan Williams <dan.j.williams@intel.com> - 2017-05-04 01:00 +0200
                Re: [RFC PATCH] dax: add badblocks check to Device DAX Dan Williams <dan.j.williams@intel.com> - 2017-05-04 01:10 +0200
                Re: [RFC PATCH] dax: add badblocks check to Device DAX "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2017-05-04 01:30 +0200
                Re: [RFC PATCH] dax: add badblocks check to Device DAX "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2017-05-04 01:40 +0200
                Re: [RFC PATCH] dax: add badblocks check to Device DAX Dan Williams <dan.j.williams@intel.com> - 2017-05-04 04:10 +0200
                Re: [RFC PATCH] dax: add badblocks check to Device DAX "Kani, Toshimitsu" <toshi.kani@hpe.com> - 2017-05-04 16:20 +0200

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