Comment 16 for bug 316607

Probably udev vol_id interface does not change that often for us to try to work around it in advance. Unnecessary calls from startup scripts is a plague that slows whole system boot process. Checking shell error codes would be the fastest and cleanest of all, but unfortunately vol_id shares error code 4 for both unknown filesystem and various probing errors.

And in the case of http://git.kernel.org/?p=linux/hotplug/udev.git;a=blob;f=extras/volume_id/vol_id.c;h=3e44c3b069794b81a1e61338c98eef0fa7671bf3;hb=HEAD#l308 it does look like a typo to me, as the whole switch statement introduces error code 3 for raid checks.