From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from relay.parallels.com ([195.214.232.42]:34564 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750896Ab2DKKfA convert rfc822-to-8bit (ORCPT ); Wed, 11 Apr 2012 06:35:00 -0400 Message-ID: <4F855E3D.6090306@parallels.com> Date: Wed, 11 Apr 2012 14:34:37 +0400 From: Stanislav Kinsbursky MIME-Version: 1.0 To: "J. Bruce Fields" CC: Jeff Layton , "linux-nfs@vger.kernel.org" Subject: Re: [PATCH][RFC] nfsd/lockd: have locks_in_grace take a sb arg References: <1333455279-11200-1-git-send-email-jlayton@redhat.com> <4F841D2A.9020504@parallels.com> <20120410081612.65dd25fa@tlielax.poochiereds.net> <4F842BAE.2010804@parallels.com> <20120410202251.GH18465@fieldses.org> In-Reply-To: <20120410202251.GH18465@fieldses.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: 11.04.2012 00:22, J. Bruce Fields пишет: > On Tue, Apr 10, 2012 at 04:46:38PM +0400, Stanislav Kinsbursky wrote: >> 10.04.2012 16:16, Jeff Layton пишет: >>> On Tue, 10 Apr 2012 15:44:42 +0400 >>> >>> (sorry about the earlier truncated reply, my MUA has a mind of its own >>> this morning) >>> >> >> OK then. Previous letter confused me a bit. >> >>> >>> TBH, I haven't considered that in depth. That is a valid situation, but >>> one that's discouraged. It's very difficult (and expensive) to >>> sequester off portions of a filesystem for serving. >>> >>> A filehandle is somewhat analogous to a device/inode combination. When >>> the server gets a filehandle, it has to determine "is this within a >>> path that's exported to this host"? That process is called subtree >>> checking. It's expensive and difficult to handle. It's always better to >>> export along filesystem boundaries. >>> >>> My suggestion would be to simply not deal with those cases in this >>> patch. Possibly we could force no_subtree_check when we export an fs >>> with a locks_in_grace option defined. >>> >> >> Sorry, but without dealing with those cases your patch looks a bit... Useless. >> I.e. it changes nothing, it there will be no support from file >> systems, going to be exported. >> But how are you going to push developers to implement these calls? >> Or, even if you'll try to implement them by yourself, how they will >> looks like? >> Simple check only for superblock looks bad to me, because any other >> start of NFSd will lead to grace period for all other containers >> (which uses the same filesystem). > > That's the correct behavior, and it sounds simple to implement. Let's > just do that. > > If somebody doesn't like the grace period from another container > intruding on their use of the same filesystem, they should either > arrange to export different filesystems (not just different subtrees) > from their containers, or arrange to start all their containers at the > same time so their grace periods overlap. > Starting all at once is not a very good solution. When you start 100 containers simultaneously - then you can't predict, when the process as a whole will succeed (it will produce heavy load on all subsystems). Moreover, there is also server restart... Anyway, I agree with the idea of this patch. Please, have a look at new export option I mentioned in "Grace period" thread. -- Best regards, Stanislav Kinsbursky