From owner-cvs-all@FreeBSD.ORG  Mon Feb 21 01:52:09 2005
Return-Path: <owner-cvs-all@FreeBSD.ORG>
Delivered-To: cvs-all@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id C62AE16A4CE
	for <cvs-all@freebsd.org>; Mon, 21 Feb 2005 01:52:09 +0000 (GMT)
Received: from mail-svr1.cs.utah.edu (mail-svr1.cs.utah.edu [155.98.64.200])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 99F9D43D55
	for <cvs-all@freebsd.org>; Mon, 21 Feb 2005 01:52:09 +0000 (GMT)
	(envelope-from swami@cs.utah.edu)
Received: from localhost (localhost [127.0.0.1])
	by mail-svr1.cs.utah.edu (Postfix) with ESMTP id 65948346F2
	for <cvs-all@freebsd.org>; Sun, 20 Feb 2005 18:52:09 -0700 (MST)
Received: from mail-svr1.cs.utah.edu ([127.0.0.1])
 by localhost (mail-svr1.cs.utah.edu [127.0.0.1]) (amavisd-new, port 10024)
 with ESMTP id 04653-03 for <cvs-all@freebsd.org>;
 Sun, 20 Feb 2005 18:52:09 -0700 (MST)
Received: from gradofc8.cs.utah.edu (gradofc8.cs.utah.edu [155.98.66.68])
	by mail-svr1.cs.utah.edu (Postfix) with ESMTP id 259DF346EC
	for <cvs-all@freebsd.org>; Sun, 20 Feb 2005 18:52:09 -0700 (MST)
Received: by gradofc8.cs.utah.edu (Postfix, from userid 4970)
	id D44CEAD9DA; Sun, 20 Feb 2005 18:52:08 -0700 (MST)
Received: from localhost (localhost [127.0.0.1])
	by gradofc8.cs.utah.edu (Postfix) with ESMTP id BF71FAD9D8
	for <cvs-all@freebsd.org>; Sun, 20 Feb 2005 18:52:08 -0700 (MST)
Date: Sun, 20 Feb 2005 18:52:08 -0700 (MST)
From: Swami Pichumani <swami@cs.utah.edu>
To: cvs-all@freebsd.org
Message-ID: <Pine.LNX.4.61.0502201846210.28727@gradofc8.cs.utah.edu>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
X-Virus-Scanned: amavisd-new at cs.utah.edu
Subject: question on mbuf(m_copyback) code 
X-BeenThere: cvs-all@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: CVS commit messages for the entire tree <cvs-all.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-all>,
	<mailto:cvs-all-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-all>
List-Post: <mailto:cvs-all@freebsd.org>
List-Help: <mailto:cvs-all-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-all>,
	<mailto:cvs-all-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 21 Feb 2005 01:52:09 -0000

Hi all,
I had a question on the m_copyback code (I use pretty old version but feel 
this might still be same).
Inside the while(len>0) loop, the first line kinda seems odd. It subtracts 
the off (which becomes after first iteration) from m_len(which is supposed 
to tell the amount of data in the particular mbuf) to find the free space 
i nthe mbuf. This obviously would not work without m_len getting initialized 
to MLEN (or MHLEN), which is not the right thing to do (since when an 
mbuf has 0 data when initialized and m_len would be zero).

thanks in advance for any comments on this,

-swami