On Mon, Sep 20, 2021 at 04:50:03PM -0700, Dan Williams wrote:

quoted

        ddev->parent = parent;
-       ddev->groups = groups;
+       if (!WARN_ON_ONCE(ddev->groups))
+               ddev->groups = groups;

That feels too compact to me, and dev_WARN_ONCE() might save someone a
git blame to look up the reason for the warning:

    dev_WARN_ONCE(parent, ddev->groups, "unexpected pre-populated
attribute group\n");
    if (!ddev->groups)
        ddev->groups = groups;

...but not a deal breaker. Either way you can add:

I'd rather keep it simple and optmize for the normal case..