From owner-freebsd-hackers Wed Nov 13 3:14: 5 2002 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 C515637B401 for ; Wed, 13 Nov 2002 03:14:04 -0800 (PST) Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id 71B4943E4A for ; Wed, 13 Nov 2002 03:14:04 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (localhost [127.0.0.1]) by apollo.backplane.com (8.12.5/8.12.5) with ESMTP id gADBE3FC069567; Wed, 13 Nov 2002 03:14:04 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.12.5/8.12.5/Submit) id gADBE3lM069566; Wed, 13 Nov 2002 03:14:03 -0800 (PST) (envelope-from dillon) Date: Wed, 13 Nov 2002 03:14:03 -0800 (PST) From: Matthew Dillon Message-Id: <200211131114.gADBE3lM069566@apollo.backplane.com> To: Terry Lambert Cc: "Daniel O'Connor" , Hans Zaunere , freebsd-hackers@FreeBSD.ORG Subject: Re: Shared files within a jail References: <20021113034726.75787.qmail@web12801.mail.yahoo.com> <1037159767.66058.34.camel@chowder.localdomain> <200211130530.gAD5UxNt067928@apollo.backplane.com> <3DD1FAB9.82607C41@mindspring.com> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG :> Try using null mounts. The warning is in there because making the :> null mount code work is a real hack and the authors aren't entirely :> sure that everything's gotten covered. That said, use of a null mount :> is certainly a lot safer if the stuff behind the mount is mostly :> static. : :The problem is in the VM object alias code. Specifically, the :getpages/putpages have to be implemented in terms of read/write, :so that there are not two vm_object_t's that refer to the same :data, since there is no "upcall" to notify of changes in a lower :layer, and therefore guarantee coherency. I'm fairly sure the VM issues were fixed when VOP_GETVOBJECT was added. A file accessed via a null mount will have the same VM object as the file in the original filesystem. I'm not 100% sure about that, I wasn't the one who did it, but I seem to recall it being discussed. -Matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message