minor bug in dump, can cause system to hang.

[Bill Shannon]

> In article <1763 at brl-tgr.ARPA> davet at RAND-UNIX.ARPA (Dave Truesdell) writes:
> >	When doing dumps from a raw device, dump does not force all reads
> >	to be done in multiples of DEV_BSIZE byte chunks.  In most cases
> >	drivers seem to handle this correctly, but one obscure case has
> >	caused one of our systems (a VAX 11/785 running 4.2BSD) to hang.
>
> But why fix dump when the problem is almost certainly in the disk driver?

Because:
	1.  If you read the man pages for the disk devices you will see
	    that they strongly suggest that you do reads in multiples
	    of 512 (== DEV_BSIZE) when reading the raw device.

	2.  Not all disk controllers on all machines are capable of
	    reading partial sectors.

The bug is in dump, and should be fixed there.

					Bill Shannon