[PATCH v2 08/25] arch: introduce memremap()

[Christoph Hellwig]

On Sun, Jul 26, 2015 at 10:49:39AM -0700, Dan Williams wrote:
> On Sun, Jul 26, 2015 at 10:25 AM, Christoph Hellwig <hch at lst.de> wrote:
> > On Fri, Jul 24, 2015 at 10:38:42PM -0400, Dan Williams wrote:
> >> The behavior change to return NULL on an unsupported request is reserved
> >> for a later patch.
> >
> > Why?
> 
> This is for drivers like pmem that care about the mapping type.  For
> example, if pmem can't get a cache-enabled mapping it is potentially
> putting the write durability of the persistent media at risk.

I understand that part, but the question is why the old behavior
is retained for now and only changed later.