From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758597AbXHBQFx (ORCPT ); Thu, 2 Aug 2007 12:05:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754355AbXHBQFo (ORCPT ); Thu, 2 Aug 2007 12:05:44 -0400 Received: from mail.fieldses.org ([66.93.2.214]:36786 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751069AbXHBQFo (ORCPT ); Thu, 2 Aug 2007 12:05:44 -0400 Date: Thu, 2 Aug 2007 12:05:36 -0400 To: Jeff Layton Cc: nfs@lists.sourceforge.net, linux-kernel@vger.kernel.org, Stefan Walter Subject: Re: [NFS] rpc.mountd crashes when extensively using netgroups Message-ID: <20070802160536.GF21282@fieldses.org> References: <46ADDFB2.9070709@inf.ethz.ch> <20070731144824.GA15231@fieldses.org> <20070802113255.d686894c.jlayton@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070802113255.d686894c.jlayton@redhat.com> User-Agent: Mutt/1.5.16 (2007-06-11) From: "J. Bruce Fields" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 02, 2007 at 11:32:55AM -0400, Jeff Layton wrote: > On Tue, 31 Jul 2007 10:48:24 -0400 > "J. Bruce Fields" wrote: > > That's an interesting problem. Thanks for the report! > > > > I don't believe that long comma-delimited string actually has any > > meaning to the kernel--as far as the kernel is concerned, it's just an > > opaque object that will be passed back to mountd later (along with a > > path name) to get export options. > > > > So I suppose that string could be replaced by a hash, or maybe even just > > by the ip address of the particular host--the disadvantage to the latter > > being that it would require the kernel to keep a separate export for > > each client address. > > I started having a look at this today. The original patches that I > proposed to clean up the rmtab a few months ago also eliminated this > comma-delimited string. Neil had valid objections to it at the time, > but if we switched to using the IP address as a cache key like Bruce > describes then doing that becomes more reasonable. > > The only downside I see is the one Bruce points out -- the size of > the kernel export cache would increase. I don't have a feel for whether > this is a show stopper, however. Yeah, there might be some risk of solving that problem at the expense of people with tons of clients all matching *.example.com. The actual export objects are actually pretty small--68 bytes, last I checked? You'd also need two upcalls to mountd per client (for ip address and export, as opposed to just ip address). I don't know what other costs there might be. What about the idea of hashing the comma-delimited list and passing that? You'd want hash large enough to be collision-free--might as well use some cryptographic hash, I guess, though it may be mild overkill. Is there any reason why that wouldn't work? Could you remind me what problems you were trying to fix with your rmtab cleanup? --b.