Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:41657 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751465Ab2ANBiy (ORCPT ); Fri, 13 Jan 2012 20:38:54 -0500 Date: Fri, 13 Jan 2012 20:38:34 -0500 From: "J. Bruce Fields" To: Trond Myklebust , NeilBrown , Tigran Mkrtchyan , Christoph Hellwig , Matthew Treinish , linux-nfs@vger.kernel.org Subject: Re: [PATCH/RFC 0/7] Volatile Filehandle Client-side Support Message-ID: <20120114013834.GA20464@fieldses.org> References: <1321052673-22171-1-git-send-email-treinish@linux.vnet.ibm.com> <1321056809.8733.2.camel@lade.trondhjem.org> <20111112144953.GA3740@infradead.org> <20111113145400.6c7a9be3@notabene.brown> <20111113163632.GA28574@fieldses.org> <20111114080745.57083bfe@notabene.brown> <1321338825.8267.2.camel@lade.trondhjem.org> <20120113170914.GA31414@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20120113170914.GA31414@us.ibm.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Jan 13, 2012 at 11:09:14AM -0600, Malahal Naineni wrote: > Trond Myklebust [Trond.Myklebust@netapp.com] wrote: > > On Mon, 2011-11-14 at 08:07 +1100, NeilBrown wrote: > > > > > If a server has objects that are never renamed, it can easily use volatile > > > file handles. > > > If a server has objects which can be renamed and wants to use volatile file > > > handles, then if such an object is open and is about to be renamed, it must > > > first log to stable storage some mapping to allow it to access the file from > > > the old volatile file handle. And of course it cannot allow renames during > > > the grace period, but I think we already have that. > > > Also, if the VFH is such that it will be lost on a reboot, the server must > > > log it to stable storage before allowing an open. > > > > BTW: If the namespace is stable, then the server can easily implement > > permanent filehandles. Use a hash of the pathname as the filehandle, and > > set up a hidden directory ('/.filehandles') containing symlinks that map > > said hash back to the correct pathname. No need for volatile > > filehandles. > > Neil and Trond, one of our use cases is for a read only file system. The > name space is stable and Volatile File Handle support should not have > any issues under those conditions, correct? Dumb question: remind me which filesystem your exporting that can't already generate stable filehandles? --b. > > Trond, trying to understand how we can make file handles permanent at > the servers with your ideas. We do use linux NFS server. Looks like the > server needs a new config parameter to hide '/.filehandles' and use it > for storing permanent file handles. Also, the solution needs a tool > that generates/populates './filehandles' directory. I don't know how > best we should handle hash collisions at this point (shouldn't be an > issue once we agree to a method though). Anything else I am missing? > > Any thoughts from linux NFS server community? Is this approach > acceptable? > > Regards, Malahal. >