From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: Delays on "first" access to a NFS mount Date: Thu, 8 Mar 2007 16:42:15 +1100 Message-ID: <17903.41527.623137.618107@notabene.brown> References: <20070307194418.97fee0ec.simon.peter@gmx.de> <20070307205016.GI26553@fieldses.org> <20070307211729.GO26553@fieldses.org> <20070307215406.GR26553@fieldses.org> <17903.16030.26119.464793@notabene.brown> <20070307230601.GX26553@fieldses.org> <17903.19755.146916.321440@notabene.brown> <20070308051401.GC15814@fieldses.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Christoph Hellwig , nfs@lists.sourceforge.net, "Talpey, Thomas" , Simon Peter To: "J. Bruce Fields" Return-path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list2-new.sourceforge.net with esmtp (Exim 4.43) id 1HPBOj-0005d8-Fx for nfs@lists.sourceforge.net; Wed, 07 Mar 2007 21:42:41 -0800 Received: from cantor2.suse.de ([195.135.220.15] helo=mx2.suse.de) by mail.sourceforge.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.44) id 1HPBOj-00029n-OU for nfs@lists.sourceforge.net; Wed, 07 Mar 2007 21:42:43 -0800 In-Reply-To: message from J. Bruce Fields on Thursday March 8 List-Id: "Discussion of NFS under Linux development, interoperability, and testing." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: nfs-bounces@lists.sourceforge.net Errors-To: nfs-bounces@lists.sourceforge.net On Thursday March 8, bfields@fieldses.org wrote: > On Thu, Mar 08, 2007 at 10:39:23AM +1100, Neil Brown wrote: > > Imagine having hundreds of filesystems on some sort of library (a CD > > library?) where each can be identified by a UUID which gets stored in > > the fsid in the filehandle. > > Imagine a simple extension to mountd so that a call-out were made when > > an unknown filehandle arrived. This callout could mount the required > > filesystem and export it. Maybe the library only allows 3 filesystems > > to be mounted at a time, so it would unmount the lease-recently-used > > one. > > Maybe. Is this practical? Do we know of any cases of users doing this? Someone once mentioned doing something vaguely like this... I don't know the exact details. It was mentioned in the context of the fsid being too small to do a really good job. I wonder if you can export autofs to get them mounted in the first place..... > Do you block forever if you try to access 4 filesystems at once? I > dunno.... round-robin? Sending lots of EINPROGRESS for one filesystem while the others have a turn. > > > I have often wanted to write a 'Linux commentary' that explains all > > the hows and whys of things. I even started some bits once (to help > > me understand the VFS layer). But Linux changes so fast that any > > entry in such a commentary would be out-of-date before it was > > written.... > > And there's a lot to document. I mean, look: > > http://www.oreilly.com/catalog/understandlni/ > > Just over a thousand pages, just covering the kernel networking code > (and only some of it at that). Maybe they just lost the forest for the > trees, but still, yipes. Is there really a market for that sort of book? Maybe we should write "Understanding Linux NFS" in our spare time .... oh wait, we don't have any spare time. Maybe in a couple of decades when I retire:-) NeilBrown ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs