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Date: Mon, 10 Feb 1997 07:50:29 -0500 (EST)
From: Thomas David Rivers <ponds!rivers@dg-rtp.dg.com>
Message-Id: <199702101250.HAA26033@lakes.water.net>
To: ponds!critter.dk.tfs.com!phk
Subject: Re: daily panics, ffs_valloc: dup alloc - Good news!
Cc: ponds!root.com!dg, ponds!freebsd.org!hackers, ponds!freebsd.org!joerg
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Poul-Henning Kamp

> 
> In message <199702091853.NAA24339@lakes.water.net>, Thomas David Rivers writes:
> >
> >I built a new "newfs", with NTRACKS bumped to 2 and NSECTORS dropped 
> >to 2048.
> >
> >It worked like a champ!  No more panic: ffs_valloc: dup alloc.
> >
> >I'd say the problem is that the underlying code can't handle one
> >track (head).
> >
> >We should probably go ahead and use this work-around in 2.1.7 and
> >2.2.  Perhaps, if we're so inclined, we can determine what a
> >better fix would be to keep the 1 track idea.  [It could possibly
> >be simply setting fs->fs_cgmask to 0 if the number of tracks is 1; but 
> >I'm not sure.]  That investigation could wait until after 2.2 and
> >2.1.7.
> 
> I've looked at the code, and I cannot see how it could be because
> of fs_cgmask being 0xffffffff.
> 
> There must be some other explanation.
> 
> Do you have the first couple of hundred lines from a dumpfs on the
> filesystem (when made with heads=1 ?)
> 

 I'll try getting it with a fixit floppy.

 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.


> --
> Poul-Henning Kamp           | phk@FreeBSD.ORG       FreeBSD Core-team.