From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fieldses.org ([173.255.197.46]:53938 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751802AbdGAMRx (ORCPT ); Sat, 1 Jul 2017 08:17:53 -0400 Date: Sat, 1 Jul 2017 08:17:52 -0400 From: "J. Bruce Fields" To: "Mkrtchyan, Tigran" Cc: Trond Myklebust , Christoph Hellwig , Jeff Layton , linux-nfs , schumaker anna Subject: Re: open by handle support for NFS V2 Message-ID: <20170701121752.GG14868@fieldses.org> References: <20170629133453.19641-1-hch@lst.de> <20170629154650.GC1651@fieldses.org> <1498842056.6728.1.camel@primarydata.com> <20170630173818.GC14868@fieldses.org> <995885135.19496849.1498901676399.JavaMail.zimbra@desy.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <995885135.19496849.1498901676399.JavaMail.zimbra@desy.de> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Sat, Jul 01, 2017 at 11:34:36AM +0200, Mkrtchyan, Tigran wrote: > > > ----- Original Message ----- > > From: "J. Bruce Fields" > > To: "Trond Myklebust" > > Cc: "Christoph Hellwig" , "Jeff Layton" , "linux-nfs" , > > "schumaker anna" > > Sent: Friday, June 30, 2017 7:38:18 PM > > Subject: Re: open by handle support for NFS V2 > > > On Fri, Jun 30, 2017 at 05:00:59PM +0000, Trond Myklebust wrote: > >> The main use case for open by filehandle was (and still should be) the > >> promise of being able to do the sort of tricks you normally associate > >> with object storage on a standard filesystem. > >> > >> Imagine that you are trying to build an application for indexing and > >> searching the data on your storage. You basically want to trawl through > >> the filesystem on a regular basis and build up a database of key words > >> and other metadata to tell you what is in the files. For that kind of > >> application, the namespace is a real PITA to deal with, because files > >> get renamed, moved and deleted all the time; so if you can store > >> something that is independent of the namespace and that will give you > >> access to the file contents, then why wouldn't you do so? Normally, > >> applications like that use the inode number, but you can't open a file > >> by inode number, and you have the same problems with inode number reuse > >> that a NFS server has. > >> > >> That's the sort of thing I'd think we want to allow through open by > >> filehandle, and I see no reason why NFS should be excluded from that > >> type of application. > > > > Thanks, that makes sense. > > > > We've had open_by_handle support for most filesystems since 2011, is > > there evidence of anyone doing this? > > > I am pretty sure that nfs-ganesha is using this in one the backend > implementations. Yes, but I was curious about the kind of application Trond describes. --b.