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Date: Sun, 11 Sep 2016 22:27:03 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Ross Zwisler <ross.zwisler@linux.intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
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Subject: Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in
 /proc/self/smaps)
Message-ID: <20160912052703.GA1897@infradead.org>
References: <CAPcyv4iDra+mRqEejfGqapKEAFZmUtUcg0dsJ8nt7mOhcT-Qpw@mail.gmail.com>
 <20160908225636.GB15167@linux.intel.com>
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On Thu, Sep 08, 2016 at 04:56:36PM -0600, Ross Zwisler wrote:
> I think this goes back to our previous discussion about support for the PMEM
> programming model.  Really I think what NVML needs isn't a way to tell if it
> is getting a DAX mapping, but whether it is getting a DAX mapping on a
> filesystem that fully supports the PMEM programming model.  This of course is
> defined to be a filesystem where it can do all of its flushes from userspace
> safely and never call fsync/msync, and that allocations that happen in page
> faults will be synchronized to media before the page fault completes.

That's a an easy way to flag:  you will never get that from a Linux
filesystem, period.

NVML folks really need to stop taking crack and dreaming this could
happen.