From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamie Lokier Subject: Re: [RFC] Support for stackable file systems on top of nfs Date: Mon, 14 Nov 2005 21:32:54 +0000 Message-ID: <20051114213254.GA29776@mail.shareable.org> References: <200511142048.jAEKmu4u017755@agora.fsl.cs.sunysb.edu> <200511142113.jAELDHfx017507@sumu.lexma.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Erez Zadok , David Howells , Nikolai Joukov , Trond Myklebust , nfsv4@linux-nfs.org, Charles Wright , linux-fsdevel@vger.kernel.org Return-path: Received: from mail.shareable.org ([81.29.64.88]:58276 "EHLO mail.shareable.org") by vger.kernel.org with ESMTP id S932163AbVKNVeC (ORCPT ); Mon, 14 Nov 2005 16:34:02 -0500 To: "John T. Kohl" Content-Disposition: inline In-Reply-To: <200511142113.jAELDHfx017507@sumu.lexma.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org John T. Kohl wrote: > >>>>> "Erez" == Erez Zadok writes: > > Erez> Will this work? Will it give us the functionality we need? > Or would we Erez> need a single page to possibly point back to a > _chain_ of inodes (which Erez> would start looking like Skinner's > "pvnode" '93 idea)? > > Also have a look at Heidemann's PhD thesis, > http://www.isi.edu:80/people/johnh/PAPERS/Heidemann95e.html This looks like it might also have relevance to "copy-on-write" copied files - multiple inodes, on the same filesystem, sharing pages in memory as well as on disk. Good for virtual machines sharing files, etc. A key feature of COW files is the need to mmap() them, and for modifications to one to not affect the mapped view of the other. Pages attached to multiple inodes would be a way of implementing that. I don't have time to write more, so I'm just putting out the observation. -- Jamie