Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261539AbUAEPO7 (ORCPT ); Mon, 5 Jan 2004 10:14:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261605AbUAEPO7 (ORCPT ); Mon, 5 Jan 2004 10:14:59 -0500 Received: from findaloan.ca ([66.11.177.6]:7106 "EHLO mark.mielke.cc") by vger.kernel.org with ESMTP id S261539AbUAEPOx (ORCPT ); Mon, 5 Jan 2004 10:14:53 -0500 Date: Mon, 5 Jan 2004 10:13:03 -0500 From: Mark Mielke To: Rob Landley Cc: David Lang , Linus Torvalds , Andries Brouwer , Rob Love , Pascal Schmidt , linux-kernel@vger.kernel.org, Greg KH Subject: Re: udev and devfs - The final word Message-ID: <20040105151303.GA30849@mark.mielke.cc> Mail-Followup-To: Rob Landley , David Lang , Linus Torvalds , Andries Brouwer , Rob Love , Pascal Schmidt , linux-kernel@vger.kernel.org, Greg KH References: <20040103040013.A3100@pclin040.win.tue.nl> <200401042148.24742.rob@landley.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200401042148.24742.rob@landley.net> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2570 Lines: 54 On Sun, Jan 04, 2004 at 09:48:24PM -0600, Rob Landley wrote: > On Sunday 04 January 2004 21:06, David Lang wrote: > > Linus, what Andries is saying is that if you export a directory (say > > /home) the process of exporting it somehow uses the /dev device number so > > if the server reboots and gets a different device number for the partition > > that /home is on the clients won't see it as the same export, breaking the > > NFS requirement that a server can be rebooted. > NFS always struck me as a peverse design. "The fileserver must be > stateless with regard to clients, even though maintainging state is > what a filesystem DOES, and the point of the thing is to export a > filesystem." Okay... (If it was exporting read-only filesystems > with no locking of any kind, maybe they'd have a point, but come on > guys...) Statelessness translated to capacity back in the day when maintaining state for hundreds or thousands of machines was expensive... I don't buy NFS as an excuse, though. I refuse to believe that a shared /dev is necessary or desirable for *any* environment. /dev/pts is one example of where everybody seems to have already agreed on this. With udev, or with devfs, a shared /dev becomes unnecessary. /dev will no longer need to be 7000+ entries. It could be a few hundred or less for common configurations, and 0% persistence/remote storage for tmpfs-udev or devfs. There are a few cases that we might be forced to maintain regular numbers: mkfifo() creates a named pipe, and bind() creates a named socket. These might be accessed between reboots over NFS, or local mounts by many existing programs. I think these must be guaranteed to keep the same major:minor numbers across reboots (preferably, even across kernel releases). These are exceptional cases, though, and should be considered as such. Cheers, mark -- mark@mielke.cc/markm@ncf.ca/markm@nortelnetworks.com __________________________ . . _ ._ . . .__ . . ._. .__ . . . .__ | Neighbourhood Coder |\/| |_| |_| |/ |_ |\/| | |_ | |/ |_ | | | | | | \ | \ |__ . | | .|. |__ |__ | \ |__ | Ottawa, Ontario, Canada One ring to rule them all, one ring to find them, one ring to bring them all and in the darkness bind them... http://mark.mielke.cc/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/