From owner-freebsd-hackers@FreeBSD.ORG  Thu May  8 12:12:57 2003
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 6DF7237B401
	for <freebsd-hackers@freebsd.org>;
	Thu,  8 May 2003 12:12:57 -0700 (PDT)
Received: from critter.freebsd.dk (critter.freebsd.dk [212.242.86.163])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 1FC2743F93
	for <freebsd-hackers@freebsd.org>;
	Thu,  8 May 2003 12:12:56 -0700 (PDT)
	(envelope-from phk@phk.freebsd.dk)
Received: from critter.freebsd.dk (localhost [127.0.0.1])
	by critter.freebsd.dk (8.12.9/8.12.9) with ESMTP id h48JCrxa001790;
	Thu, 8 May 2003 21:12:53 +0200 (CEST)
	(envelope-from phk@phk.freebsd.dk)
To: alih@internetDog.org
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
In-Reply-To: Your message of "Thu, 08 May 2003 15:03:41 EDT."
             <20030508150341.B28906@internetDog.org> 
Date: Thu, 08 May 2003 21:12:52 +0200
Message-ID: <1789.1052421172@critter.freebsd.dk>
cc: freebsd-hackers@freebsd.org
Subject: Re: cache_purge > cache_zap segmentation fault 
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 08 May 2003 19:12:57 -0000

In message <20030508150341.B28906@internetDog.org>, Ali Bahar writes:

>Given the vnode for /usr/src, 
>
>  - is its v_cache_dst a linked list of namecache entries for /usr, 
>  - &  its v_cache_src a linked list of namecache entries for /usr/src/sys ?

If you look at the definition in sys/sys/vnode.h, it actually is pretty
clear from that:

struct vnode {
	[...]
        LIST_HEAD(, namecache) v_cache_src;     /* c Cache entries from us */
        TAILQ_HEAD(, namecache) v_cache_dst;    /* c Cache entries to us */
	[...]
};

So imagine this name cache entry:

	{
	directory vnode:	vnode of "/usr/src"	[vnode#1]
	name			"sys"
	destination vnode:	vnode of "/usr/src/sys"	[vnode#2]
	}

This name cache entry will be a member of the "v_cache_src" LIST from
vnode#1, and of the v_cache_dst TAILQ for vnode#2

Other entries on vnode#1's ..._src LIST will be for /usr/src/bin,
/usr/src/etc and so on.

The thing you have to remember is that one vnode can have multiple names
due to hard links.  If it could have only one, the TAILQ would not
be necessary.

In this case there will be no other elements on vnode#2's TAILQ
since we do not allow hardlinks to directories.

>Would you know if the 5.0 modifications could fix this problem?

I'm not sure I know what the problem is, I just stumbled on your
email midthread I think...

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.