From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Bharata B Rao" Subject: Re: [RFC 0/7] [RFC] cramfs: fake write support Date: Mon, 2 Jun 2008 11:37:07 +0530 Message-ID: <344eb09a0806012307v8a8c0e4pd4ccfd27825cc0c4@mail.gmail.com> References: <9785.1212374902@jrobl> <200806020437.m524bWiW027508@agora.fsl.cs.sunysb.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Arnd Bergmann" , "Jamie Lokier" , "Phillip Lougher" , "Jan Engelhardt" , "David Newall" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@lst.de To: "Erez Zadok" Return-path: Received: from rv-out-0506.google.com ([209.85.198.224]:31171 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751614AbYFBGHJ (ORCPT ); Mon, 2 Jun 2008 02:07:09 -0400 Received: by rv-out-0506.google.com with SMTP id l9so897423rvb.1 for ; Sun, 01 Jun 2008 23:07:09 -0700 (PDT) In-Reply-To: <200806020437.m524bWiW027508@agora.fsl.cs.sunysb.edu> Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, Jun 2, 2008 at 10:07 AM, Erez Zadok wrote: > > Nevertheless, I can understand if the embedded community wants lightweight > unioning. Union Mounts initially may not support everything that unionfs > does, but it should be smaller, and it should be enough I believe for the > basic unioning uses --- perhaps even for the embedded community. If so, > then I suggest people offer to help Bharata and Jan Blunk's efforts, rather > than [sic] cramming unioning into a single file system. > Though Union Mount effort has become slow and silent lately, some of us are still working on it. While I worked on readdir support lately, Jan Blunck and David Woodhouse are working on having a generic whiteout support for linux. Talking about help, Union Mount effort could take a generous help in getting directory listing implementation right. We first tried to handle duplicate elimination (during readdir) inside the kernel entirely. The outcome was neither clean nor efficient. (http://lkml.org/lkml/2007/12/5/147). Then there was a suggestion to push the duplicate elimination to userspace. When that was tried out (http://lkml.org/lkml/2008/4/29/248), we were told that NFS support is going to be an issue. (BTW NFS support is going to be an issue irrespective of where directory listing is implemented: kernel or userspace). Some insights into feasibility of supporting NFS with Union Mount from people who understand NFS better would be very helpful. Regards, Bharata. -- http://bharata.sulekha.com/blog/posts.htm