Comment # 24 on bug 948771 from Michael Chang

(In reply to Fabian Vogt from comment #4)
> > This way it will override any other unit and no extraneous warning will be generated.
> 
> That's the correct approach to avoid the warning, but we WANT the warning to
> appear.
> It notifies us that mount options for / (for example, discard on XFS which
> can not be changed at runtime by "mount -o remount,discard") may have been
> ignored.

That sounds like XFS bug to fix, and actually the warning message is not
precise to what have happened ..

> Once root= is gone from the cmdline it's not an issue anymore. I agree that
> this patch should've been delayed a bit, but it's not that big of an issue,
> I hope :-)

It may not be an issue here, but may be other issue there. Consider power user
may try to custom their initrd from another source and oops ..  

Thanks.