On 9/15/21 1:35 PM, Dan Williams wrote:

On Wed, Sep 15, 2021 at 10:23 AM Eric Sandeen [off-list ref] wrote:

quoted

For six years now, when mounting xfs, ext4, or ext2 with dax, the drivers
have logged "DAX enabled. Warning: EXPERIMENTAL, use at your own risk."

IIRC, dchinner added this to the original XFS patchset, and Dan Williams
followed suit for ext4 and ext2.

After brief conversations with some ext4 and xfs developers and maintainers,
it seems that it may be time to consider removing this warning.

For XFS, we had been holding out for reflink+dax capability, but proposals
which had seemed promising now appear to be indefinitely stalled, and
I think we might want to consider that dax-without-reflink is no longer
EXPERIMENTAL, while dax-with-reflink is simply an unimplemented future
feature.

I do regret my gap in engagement since the last review as I got
distracted by CXL, but I've recently gotten my act together and picked
up the review again to help get Ruan's patches over the goal line [1].
I am currently awaiting Ruan's response to latest review feedback
(looks like a new posting this morning). During that review Christoph
identified some cleanups that would help Ruan's series, and those are
now merged upstream [2]. The last remaining stumbling block (further
block-device entanglements with dax-devices) I noted here [2]. The
proposal is to consider eliding device-mapper dax-reflink support for
now and proceed with just xfs-on-/dev/pmem until Mike, Jens, and
Christoph can chime in on the future of dax on block devices.

As far as I can see we have line of sight to land xfs-dax-reflink
support for v5.16, does anyone see that differently at this point?

Thanks for that update, Dan. I'm wondering, even if we have renewed
hopes and dreams for dax+reflink, would it make sense to go ahead and
declare dax without reflink non-experimental, and tag dax+reflink as
a new "EXPERIMENTAL feature if and when it lands?

-Eric