From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
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>,
	Xiao Guangrong <guangrong.xiao@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.com>, Gleb Natapov <gleb@kernel.org>,
	mtosatti@redhat.com, KVM list <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Yumei Huang <yuhuang@redhat.com>, Linux MM <linux-mm@kvack.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
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>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20160908225636.GB15167@linux.intel.com>
Sender: owner-linux-mm@kvack.org
List-ID: <linux-fsdevel.vger.kernel.org>

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.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>