9cd93b3aec
when bdevsw[] became sparse. We still depend on magic to avoid having to check that (v_rdev) device numbers in vnodes are not NODEV. Removed a redundant `major(dev) < nblkdev' test instead of updating it. Don't follow a garbage bdevsw pointer for attempts to swap on empty regular files. This case currently can't happen. Swapping on regular files is ifdefed out in swapon() and isn't attempted for empty files in nfs_mountroot().