Re: [PATCH v3 2/4] generic: test mmap io fom DAX to non-DAX

[Ross Zwisler <ross.zwisler@linux.intel.com>]

On Fri, Apr 14, 2017 at 08:33:44AM -0700, Dan Williams wrote:
> On Fri, Apr 14, 2017 at 8:22 AM, Ross Zwisler
> <ross.zwisler@linux.intel.com> wrote:
> > On Fri, Apr 14, 2017 at 07:49:48AM -0700, Dan Williams wrote:
> >> On Fri, Apr 14, 2017 at 3:01 AM, Xiong Zhou <xzhou@redhat.com> wrote:
> >> > I agree with Ross that we don't even need ndctl and jq, if we run tests
> >> > on memmap setup.
> >>
> >> I don't understand this comment. How is the test determining if it is
> >> on an memmap defined namespace without querying sysfs?
> >
> > If we we assume that a setup is *either* memmap based or NFIT based, we can
> > choose whether to use jq & ndctl by grepping for "memmap" with a trailing "!"
> > in /proc/cmdline.
> >
> > If you think we need to worry about the case where users have both a valid
> > NFIT and a memmap kernel command line param making them a PMEM region, this
> > shortcut won't work.
> 
> Since the user is picking the pmem device the test will gave the wrong
> answer if they pick the wrong one. Especially since the kernel is
> growing new nvdimm bus types, like the powerpc one, this test should
> check the namespace mode.

Fair enough.