Re: DAX mapping detection (was: Re: [PATCH] Fix region lost in /proc/self/smaps)

From: Christoph Hellwig
Date: Mon Sep 12 2016 - 01:27:14 EST

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