Path: utzoo!attcan!uunet!cucstud!tfd!kent
From: kent@tfd.UUCP (Kent Hauser)
Newsgroups: comp.bugs.4bsd
Subject: Re: 4.3 Tahoe dump bug
Summary: FIX: read a whole frag
Keywords: dump bug
Message-ID: <1135@tfd.UUCP>
Date: 19 Dec 88 15:26:57 GMT
References: <23685@pprg.unm.edu>
Organization: Twenty-First Designs, Wash, DC
Lines: 55

In article <23685@pprg.unm.edu>, cyrus@pprg.unm.edu (Tait Cyrus) writes:
> 
> In the process of trying to get the 4.3 Tahoe dump running on a Sun 3
> running SunOS 3.X, I, along with others, have run into the following
> bug (feature) (shown below).
> 
> >Writing dump file 0 (/research)
> >  DUMP: Date of this level 1 dump: Sat Dec 17 12:59:10 1988
> >  DUMP: Date of last level 0 dump: Wed Dec 14 19:08:42 1988
> >  DUMP: Dumping /dev/rxy1g (/research) to /dev/rmt1h on host houdini
> >  DUMP: mapping (Pass I) [regular files]
> >  DUMP: mapping (Pass II) [directories]
> >  DUMP: (This should not happen)bread from /dev/rxy1g [block 58766]: count=24, got=512
> >  DUMP: (This should not happen)bread from /dev/rxy1g [block 60802]: count=536, got=1024
> >				.
> >				.
> >				.
> ---

The problem is that some raw device drivers can not read a partial block.
See for instance the SunOS sd(4) man page.  I suspect that this problem
is inherent with SCSI devices.

The 'fix' is to make dump always read the complete frag when
reading the directories.  Attached is my fix:

*** dumptraverse.c~	Fri Nov 18 12:22:18 1988
--- dumptraverse.c	Sat Dec 10 12:21:49 1988
***************
*** 265,271 ****
  		return;
  	if (filesize > size)
  		filesize = size;
! 	bread(fsbtodb(sblock, d), dblk, filesize);
  	for (loc = 0; loc < filesize; ) {
  		dp = (struct direct *)(dblk + loc);
  		if (dp->d_reclen == 0) {
--- 265,272 ----
  		return;
  	if (filesize > size)
  		filesize = size;
! /* change the third bread arg from filesize to size to read whole frag */
! 	bread(fsbtodb(sblock, d), dblk, size);
  	for (loc = 0; loc < filesize; ) {
  		dp = (struct direct *)(dblk + loc);
  		if (dp->d_reclen == 0) {

==============================

> W. Tait Cyrus   (505) 277-0806		e-mail: cyrus@pprg.unm.edu


-- 
Kent Hauser			UUCP: sun!sundc!tfd!kent
Twenty-First Designs		INET: kent%tfd.uucp@sundc.sun.com