From owner-freebsd-fs@FreeBSD.ORG  Mon Sep 19 02:25:53 2005
Return-Path: <owner-freebsd-fs@FreeBSD.ORG>
X-Original-To: freebsd-fs@freebsd.org
Delivered-To: freebsd-fs@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id D211516A420
	for <freebsd-fs@freebsd.org>; Mon, 19 Sep 2005 02:25:53 +0000 (GMT)
	(envelope-from ezk@fsl.cs.sunysb.edu)
Received: from filer.fsl.cs.sunysb.edu (filer.fsl.cs.sunysb.edu
	[130.245.126.2])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 5A76443D4C
	for <freebsd-fs@freebsd.org>; Mon, 19 Sep 2005 02:25:53 +0000 (GMT)
	(envelope-from ezk@fsl.cs.sunysb.edu)
Received: from agora.fsl.cs.sunysb.edu (agora.fsl.cs.sunysb.edu
	[130.245.126.12])
	by filer.fsl.cs.sunysb.edu (8.12.8/8.12.8) with ESMTP id j8J2Pj9P014911;
	Sun, 18 Sep 2005 22:25:45 -0400
Received: from agora.fsl.cs.sunysb.edu (localhost.localdomain [127.0.0.1])
	by agora.fsl.cs.sunysb.edu (8.13.1/8.13.1) with ESMTP id j8J2Pi7m016628;
	Sun, 18 Sep 2005 22:25:44 -0400
Received: (from ezk@localhost)
	by agora.fsl.cs.sunysb.edu (8.13.1/8.12.8/Submit) id j8J2PclG016625;
	Sun, 18 Sep 2005 22:25:38 -0400
Date: Sun, 18 Sep 2005 22:25:38 -0400
Message-Id: <200509190225.j8J2PclG016625@agora.fsl.cs.sunysb.edu>
From: Erez Zadok <ezk@cs.sunysb.edu>
To: Scott Long <scottl@samsco.org>, Kris Kennaway <kris@obsecurity.org>,
	Erez Zadok <ezk@cs.sunysb.edu>, freebsd-fs@freebsd.org, christos@zoulas.com
In-reply-to: Your message of "Sun, 18 Sep 2005 18:12:36 MDT."
	<432E0274.4010704@samsco.org> 
X-MailKey: Erez_Zadok
Cc: 
Subject: Re: turning off the NFS attribute cache 
X-BeenThere: freebsd-fs@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Filesystems <freebsd-fs.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
	<mailto:freebsd-fs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-fs>
List-Post: <mailto:freebsd-fs@freebsd.org>
List-Help: <mailto:freebsd-fs-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-fs>,
	<mailto:freebsd-fs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 19 Sep 2005 02:25:54 -0000

Good news!

After browsing the 6.0 kernel sources, I found out that freebsd DOES indeed
have a way of turning off the attribute cache.  It's not enough to just set
nfs_args->acregmin and friends, but you also need to

	nfs_args->flags |= NFSMNT_ACREGMIN

Otherwise, the kernel ignores what you set in the ->acregmin field.  So, to
completely turn off the attrcache on freebsd, you have to set four fields in
struct nfs_args to 0, and turn four flags on in ->flags.

It's cumbersome, but it works.  You may still want to consider offering a
"noac" flag for convenience, which'd set all eight values as needed (as some
OSs do).  At the very least, please document specifically in the mount_nfs
man page how one turns off the attribute cache completely.

Anyway, I was able to verify this in 5.4 and 6.0 (SNAP001).  And it looks
like the NFSMNT_ACREGMIN type of flags have existed as far back as 4.x, so I
suspect that as long as the implementation was correct, even old versions of
BSD should work well now with Amd.

I'll release a quick new version of am-utils (6.1.2.1) with this fix,
specifically because I have a few freebsd users who complained about this
bug.

I would like to ask whomever is responsible for maintaining am-utils for
FreeBSD to consider importing 6.1.2.1 into your ports tree.  Currently
you're stuck at an ancient 6.0.10.  6.1.x fixes numerous bugs other than
this latest one, plus it offers a host of new performance and security
features.

Thanks,
Erez.