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Date:      Fri, 09 Feb 2001 10:13:46 -0500
From:      Kevin Brunelle <kruptos@netzero.net>
To:        freebsd-hackers@FreeBSD.ORG
Subject:   Re: mount checking for read-only media
Message-ID:  <3A84092A.7552DA11@netzero.net>
References:  <3A837A0A.DAB3520A@columbus.rr.com> <200102090558.f195wEW01613@harmony.village.org>

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I am sorry if this hits the list twice. But, I think my school's
mailserver has been silently dropping mail for some time now. -KB

Well,

> This is a driver bug.  The da driver, which deals with disks, doesn't
> check to see if the media is writable or not before allowing r/w
> mounts.  You could short circuit the panic by fixing this.

I know this is going to sound corny, but if this gets fixed I am going
to miss it.

#ifdef SAGA

After I had been using FreeBSD for a while I realized I had never seen a
kernel panic. So I specifically went and tried to cause one. It took
several days of looking through the code and I still found nothing. I
needed to go to school, but I knew I had a class where I could look at
some code if I brought it with me. I grabbed a disk, mounted it, and
started copying files to it. There was no problem for a while, but then
it tried to start writing the data; instant kernel panic. The disk was
write protected and I had accidentally found what I was looking for. I
did figure out where it must be, but I never looked for it; I never
really wanted to find it. I figured if I found it, I would want to fix
it. I assumed the occurrence must be rare, and if it wasn't, a better
programmer than myself would offer a fix to it. Instead I used it to
show my friends what a kernel panic looked like, and explain to them
exactly the lengths it took to get my system to mess up. This was
amazing to them, as they were Windows users and to them a crash was a
daily occurrence. I also used it to show how even programs that had been
in use for a long time, could still have bugs in them.

As the months flew by, as they seem to do with FreeBSD. I showed people
less and less, and I guess I really forgot about it. [I think I first
found it in 3.4-RELEASE] I guess I assumed it was fixed, although I
never checked. Now, I know it is still there, and I will miss it when it
is gone. This is one of my favorite bugs. If it does get fixed, I might
just keep a copy of the old source around -- for the memories.

#endif

[HHOS] Yes, I know I have problems. ;-)

Kevin Brunelle
-- 
"Do not meddle in the affairs of sysadmins,
for they are subtle and quick to anger."
HHOS=Ha ha only serious.


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