[RFC PATCH 2/2] nvme/core: advertise BLK_EXPECTED_REF_TAG_CAPABLE

[Christoph Hellwig]

On Wed, Jul 15, 2026 at 10:01:39AM -0600, Keith Busch wrote:
> > I mentioned this in the cover letter (and that's why I marked these
> > patches "RFC"). Unless you have a clever idea, it does seem like an
> > insurmountable obstacle here.
> 
> We had a similar problem when we enabled PI at the end of the metadata
> rather than just at the beginning. This left machines unbootable after
> upgrading the kernel, so we have a module parameter to turn off support
> for the feature. It's an unpleasant solution as there's no upgrade path
> to ever turn on the feature without a format first.

We could opt into not faking up type 1 PI with a REQ_ or BIP_ flag.
But we'd really need a user that actually wants it first.