Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933417AbZGPVV7 (ORCPT ); Thu, 16 Jul 2009 17:21:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933359AbZGPVV6 (ORCPT ); Thu, 16 Jul 2009 17:21:58 -0400 Received: from mail-out2.uio.no ([129.240.10.58]:43515 "EHLO mail-out2.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933404AbZGPVV6 (ORCPT ); Thu, 16 Jul 2009 17:21:58 -0400 Subject: Re: [PATCH 16/20] ceph: nfs re-export support From: Trond Myklebust To: Sage Weil Cc: "J. Bruce Fields" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: References: <1247693090-27796-8-git-send-email-sage@newdream.net> <1247693090-27796-9-git-send-email-sage@newdream.net> <1247693090-27796-10-git-send-email-sage@newdream.net> <1247693090-27796-11-git-send-email-sage@newdream.net> <1247693090-27796-12-git-send-email-sage@newdream.net> <1247693090-27796-13-git-send-email-sage@newdream.net> <1247693090-27796-14-git-send-email-sage@newdream.net> <1247693090-27796-15-git-send-email-sage@newdream.net> <1247693090-27796-16-git-send-email-sage@newdream.net> <1247693090-27796-17-git-send-email-sage@newdream.net> <20090716192755.GE2495@fieldses.org> Content-Type: text/plain Date: Thu, 16 Jul 2009 17:21:51 -0400 Message-Id: <1247779311.12292.162.camel@heimdal.trondhjem.org> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit X-UiO-Ratelimit-Test: rcpts/h 8 msgs/h 3 sum rcpts/h 9 sum msgs/h 3 total rcpts 883 max rcpts/h 27 ratelimit 0 X-UiO-Spam-info: not spam, SpamAssassin (score=-5.0, required=5.0, autolearn=disabled, UIO_MAIL_IS_INTERNAL=-5, uiobl=NO, uiouri=_URIID_) X-UiO-Scanned: DA49A938B43E53DAEF55BD5C20494A052007AF3D X-UiO-SPAM-Test: remote_host: 68.40.207.222 spam_score: -49 maxlevel 80 minaction 2 bait 0 mail/h: 3 total 64 max/h 5 blacklist 0 greylist 0 ratelimit 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1402 Lines: 30 On Thu, 2009-07-16 at 12:50 -0700, Sage Weil wrote: > On Thu, 16 Jul 2009, J. Bruce Fields wrote: > > On Wed, Jul 15, 2009 at 02:24:46PM -0700, Sage Weil wrote: > > > Basic NFS re-export support is included. This mostly works. However, > > > Ceph's MDS design precludes the ability to generate a (small) > > > filehandle that will be valid forever, so this is of limited utility. > > > > Is there any hope of fixing that? > > Yes, but it requires some additional ondisk metadata the MDS isn't > maintaining yet (a parent directory backpointer on file objects). > > The MDS changes will mean more random IO for rename intensive workloads, > but the backpointers would also be useful for rebuilding the directory > tree in the event of some catastrophic metadata loss or corruption. > (Currently they're only there for directories, not all files.) Note that a filehandle that contains parent directory information is still not one that is valid forever. It will change in the case of a cross-directory rename, and so isn't a filehandle in the NFSv2/v3 sense. Even in the NFSv4 case, it would have to be labelled as 'volatile'. Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/