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Subject: Re: [PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page()
To:     Dan Williams <dan.j.williams@intel.com>
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From:   "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Date:   Fri, 14 Jun 2019 22:25:18 +0530
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On 6/14/19 10:06 PM, Dan Williams wrote:
> On Fri, Jun 14, 2019 at 9:26 AM Aneesh Kumar K.V
> <aneesh.kumar@linux.ibm.com> wrote:

>> Why not let the arch
>> arch decide the SUBSECTION_SHIFT and default to one subsection per
>> section if arch is not enabled to work with subsection.
> 
> Because that keeps the implementation from ever reaching a point where
> a namespace might be able to be moved from one arch to another. If we
> can squash these arch differences then we can have a common tool to
> initialize namespaces outside of the kernel. The one wrinkle is
> device-dax that wants to enforce the mapping size,

The fsdax have a much bigger issue right? The file system block size is 
the same as PAGE_SIZE and we can't make it portable across archs that 
support different PAGE_SIZE?

-aneesh