On Fri, Aug 25, 2017 at 12:54:15AM -0700, Christoph Hellwig wrote:

quoted

1)  Has there been any other difficulty that XFS has had due to the
fact that they have this DAX flag added?  e.g., are there any
operational, or practical code maintainability issues at stake here?
Or is this mostly an design philosophy debate?

It hasn't yet.  It will create really annoying problems once we
use raw DAX access for metadata, which I had prototype a while ago
and plan to finnally get in in the next months.

quoted

2) Are there any users using the DAX flag with XFS such that, if XFS
were to remove the DAX flag support, those users would complain
bitterly?

I don't know of anyone that actually uses the flag.  If someone did
that would probably run into problems like changing that changing it
on a file that's currently mmaped would crash an burn badly.

Crash and burn meaning the *kernel* will crash and burn?  Or will data
be damaged?

Given that, maybe XFS should withdraw support for the DAX and hope no
one is actually using it?

					- Ted