I think it's wrong to print out messages like that because DIAGNOSTIC is defined. DIAGNOSTIC is supposed to just add KASSERT (was panic, long ago) about conditions that must be true unless the kernel is buggy. Separately, given that there's no rule that all disks must have labels, it seems wrong of the kernel to print this. Certainly readdisklable() or something can return an error, and a caller can do something, but IMHO external input shouldn't trigger printfs like this. So I would be inclined to drop the printf, but as you say you might want to figure out why there is more than one attempt to read the label.
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