From: "J. Bruce Fields" Subject: Re: [NFS] -EXDEV between mounts that are same fs Date: Sun, 10 Feb 2008 10:57:33 -0500 Message-ID: <20080210155733.GC25571@fieldses.org> References: <20080209200503.6a11e88b@poseidon.drzeus.cx> <20080209191021.GE25533@fieldses.org> <20080209213511.59ff4e2c@poseidon.drzeus.cx> <20080209231435.GA20501@fieldses.org> <20080210131224.1d4ae39f@poseidon.drzeus.cx> <20080210152618.GB25571@fieldses.org> <20080210153340.GB14540@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: nfs@lists.sourceforge.net, Pierre Ossman To: Christoph Hellwig Return-path: Received: from neil.brown.name ([220.233.11.133]:34518 "EHLO neil.brown.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750745AbYBJP6H (ORCPT ); Sun, 10 Feb 2008 10:58:07 -0500 Received: from brown by neil.brown.name with local (Exim 4.63) (envelope-from ) id 1JOEZA-0007vq-B9 for linux-nfs@vger.kernel.org; Mon, 11 Feb 2008 02:58:04 +1100 In-Reply-To: <20080210153340.GB14540@infradead.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Sun, Feb 10, 2008 at 10:33:40AM -0500, Christoph Hellwig wrote: > On Sun, Feb 10, 2008 at 10:26:18AM -0500, J. Bruce Fields wrote: > > > The point of the setup is of course to avoid exposing more information > > > than is necessary, while still having the benefit of having a single > > > pool of disk space for all exported resources. > > > > I notice that btrfs claims support for "subvolumes"--multiple filesystem > > namespaces sharing the same storage. Seems like a useful feature for > > this situation. I don't know whether it'd be possible to add to other > > filesystems. > > That stuff is done using a code sniplet from me, which does nothing but > allowing to mount into a subdirectory of a filesystem. It will look > exactly the same as bind mounts. To get the equivalent of subtree checking, we also need a reference from each inode back to the subvolume it belongs to, so we can determine the subvolume from a filehandle. I assume that's a more intrusive change. --b. > I have hacked up implementations for > ext2 and xfs aswell and in the form btfs does it currently it would > be doable for any filesystem. But to actually make it useful you'd > need quotas for each subvolume which is something currently only > xfs could provide (if I could be arsed into finally implementing > my multiple subvolumes proposal fully). > ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs _______________________________________________ Please note that nfs@lists.sourceforge.net is being discontinued. Please subscribe to linux-nfs@vger.kernel.org instead. http://vger.kernel.org/vger-lists.html#linux-nfs