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

Dan Williams
2017-04-14T15:33:46Z

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.