# Re: \[LSF/MM TOPIC\] Future direction of DAX

- From: Jeff Moyer \<hidden\>
- Date: 2017-01-17 16:07:14 
- List: linux-block
- Page: https://ratatoskr.run/linux-block/2017/01/116760
- Thread: https://ratatoskr.run/linux-fsdevel/2017/01/116760/t.md

```text
Christoph Hellwig [ref] writes:

> On Tue, Jan 17, 2017 at 09:54:27AM -0500, Jeff Moyer wrote:
>> I spoke with Dave before the holidays, and he indicated that
>> PMEM_IMMUTABLE would be an acceptable solution to allowing applications
>> to flush data completely from userspace.  I know this subject has been
>> beaten to death, but would you mind just summarizing your opinion on
>> this one more time?  I'm guessing this will be something more easily
>> hashed out at LSF, though.
>
> Come up with a prototype that doesn't suck and allows all fs features to
> actually work.

OK, I'll take this to mean that PMEM_IMMUTABLE is a non-starter.
Perhaps synchronous page faults (or whatever you want to call it) would
work, but...

> And show an application that actually cares and shows benefits on
> publicly available real hardware.

This is the crux of the issue.

> Until then go away and stop wasting everyones time.

Fair enough.  It seems fairly likely that this sort of functionality
would provide a big benefit.  But I agree we should have a real-world
use case as proof.

Thanks,
Jeff
```