With the introduction of UFS2 we started looking for superblocks in four different locations on a prospective filesystem.
With the introduction of UFS2 we started looking for superblocks in
four different locations on a prospective filesystem.

If we found none, we forgot to invalidate the four buffers, thus the
following sequence would fails:

	(md0 = blank disk)
	mount /dev/md0 /mnt
	(fails, no superblocks)
	newfs /dev/md0
	(writes using physio which does not go through buffercache).
	mount /dev/md0 /mnt
	(still fails, the four cached buffers still contain no superblocks)

Found by:	ru

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