From owner-freebsd-hackers  Mon Feb 10 05:26:16 1997
Return-Path: <owner-hackers>
Received: (from root@localhost)
          by freefall.freebsd.org (8.8.5/8.8.5) id FAA02251
          for hackers-outgoing; Mon, 10 Feb 1997 05:26:16 -0800 (PST)
Received: from bofh.cybercity.dk (bofh.cybercity.dk [195.8.128.254])
          by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id FAA02246;
          Mon, 10 Feb 1997 05:26:08 -0800 (PST)
Received: from critter.dk.tfs.com ([140.145.230.252]) by bofh.cybercity.dk (8.8.3/8.7.3) with ESMTP id OAA02888; Mon, 10 Feb 1997 14:28:18 +0100 (MET)
Received: from critter.dk.tfs.com (localhost [127.0.0.1]) by critter.dk.tfs.com (8.8.2/8.8.2) with ESMTP id OAA12737; Mon, 10 Feb 1997 14:28:06 +0100 (MET)
To: Thomas David Rivers <ponds!rivers@dg-rtp.dg.com>
cc: dg@freebsd.org, hackers@freebsd.org, joerg@freebsd.org
Subject: Re: daily panics, ffs_valloc: dup alloc - Good news! 
In-reply-to: Your message of "Mon, 10 Feb 1997 07:50:29 EST."
             <199702101250.HAA26033@lakes.water.net> 
Date: Mon, 10 Feb 1997 14:28:06 +0100
Message-ID: <12735.855581286@critter.dk.tfs.com>
From: Poul-Henning Kamp <phk@critter.dk.tfs.com>
Sender: owner-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

> I'll try getting it with a fixit floppy.

please, it's rather crucial for debugging this.

> But, if you'll read my previous writeup; you'll see that a fs_cgmask
>of 0xffffffff causes a problem in the cgstart macro:
>
>#define cgstart(fs, c)                                                  \
>        (cgbase(fs, c) + (fs)->fs_cgoffset * ((c) & ~((fs)->fs_cgmask)))
>
>effectively eliminating the fs_cgoffset value.  This is what we're
>guessing is the problem.

The cgoffset is only there to make sure that all of the superblock
copies are not on the same head.  Since we only have one head that
field (correctly) doesn't apply.

I must admit that I don't really know what to look for, but if I get
the data on the filesystem, at least I can start to dig through
the code looking for trouble.

I'm actually thinking about making a version of ufs that has all this
head/track/sector knowledge pulled out, it really obfuscates the code
a lot.


--
Poul-Henning Kamp           | phk@FreeBSD.ORG       FreeBSD Core-team.
http://www.freebsd.org/~phk | phk@login.dknet.dk    Private mailbox.
whois: [PHK]                | phk@tfs.com           TRW Financial Systems, Inc.
Power and ignorance is a disgusting cocktail.