From owner-freebsd-fs  Sun Jan 12 13: 0:30 2003
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Date: Mon, 13 Jan 2003 08:00:48 +1100 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: David Schultz <dschultz@uclink.Berkeley.EDU>
Cc: Tomas Pluskal <plusik@pohoda.cz>,
	Terry Lambert <tlambert2@mindspring.com>, <freebsd-fs@FreeBSD.ORG>
Subject: Re: seeking help to rewrite the msdos filesystem
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On Sun, 12 Jan 2003, David Schultz wrote:

> Thus spake Tomas Pluskal <plusik@pohoda.cz>:
> > I have made a simple patch to enable clustering in msdosfs.
> > It is against 4-STABLE.
> [...]
> >  	if (ap->a_runp) {
> > -		/*
> > -		 * Sequential clusters should be counted here.
> > -		 */
> > -		*ap->a_runp = 0;
> > +		int nblk;
> > +
> > +		nblk = (dep->de_FileSize >> bshift) - (lblkno + 1);
>
> I'm not sure I understand what you're trying to do here.  Does
> this work with files that are fragmented?  You appear to be
> assuming that they are not.  Maybe you copied the code from the
> cd9660 filesystem, which does not permit external fragmentation.

ISTR suggesting looking at cd9660 for examples of how to do clustering.
Unfortunately, it is too simple here.  The corresponding code in ufs
and ext2fs is quite complicated.

Bruce


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