minor bug in dump, can cause system to hang.

[Bill Shannon]

> > > But why fix dump when the problem is almost certainly in the disk driver?
> >
> > . . .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. . .
> > The bug is in dump, and should be fixed there.
> 
> If the claim is that dump "ought to" read in multiples of DEV_BSIZE,
> then the driver is buggy in its failure to reject read requests of other sizes.

The manual doesn't go so far as to say that this will not work, or may not
work, only that it is suggested that you not do it.  The driver is free to
provide this capability as an extension (in which case the previously
mentioned bugs should be fixed so that it works properly) but no portable
program should depend on that extension.

					Bill Shannon