Re: [RFC PATCH] common/rc: Fix _check_s_dax() for kernel 5.10

On Wed, Dec 02, 2020 at 11:10:50AM -0600, Eric Sandeen wrote:

xfstests gets used on distro kernels too, so relying on kernel version isn't
really something we can use to make determinations like this, unfortunately.

Probably the best we can do is hope that the change makes it to stable and
distro kernels quickly, and the old flag fades into obscurity.

Maybe worth a comment in the test mentioning the SNAFU, though, for anyone
investigating it when it fails on older kernels?

I think we should explicitly check for the "old" or mixed up flag and
error out.  Given that the other meaning of the bit value should only
be set on mount points it should be easy to test.  That means we will
reliably fail on old and distro kernels, but I think that is the right
thing to do in this case.