From: Trond Myklebust Subject: Re: [PATCH] NLM: add network test when host expire but hold lock at nlm_gc_hosts Date: Wed, 02 Dec 2009 09:29:03 -0500 Message-ID: <1259764143.2663.10.camel@localhost> References: <4B163798.7010309@cn.fujitsu.com> <20091202072644.31c5d17e@tlielax.poochiereds.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Mi Jinlong , NFSv3 list , "J. Bruce Fields" To: Jeff Layton Return-path: Received: from mail-out2.uio.no ([129.240.10.58]:40909 "EHLO mail-out2.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753644AbZLBO3F (ORCPT ); Wed, 2 Dec 2009 09:29:05 -0500 In-Reply-To: <20091202072644.31c5d17e-9yPaYZwiELC+kQycOl6kW4xkIHaj4LzF@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Wed, 2009-12-02 at 07:26 -0500, Jeff Layton wrote: > On Wed, 02 Dec 2009 17:47:04 +0800 > Mi Jinlong wrote: > > > After a client get lock, it's network partition for some reasons. > > other client cannot get lock success forever. > > > > This patch can avoid this problem using rpc_ping to test client's > > network when host expired but hold lock. > > > > If the client's network is partition, server will release client's > > lock, other client will get lock success. > > > > Signed-off-by: mijinlong@cn.fujitsu.com > > Yikes! That sounds like it'll make locking subject to the reliability > of the network. I don't think that's a good idea. > > What might be more reasonable is to consider implementing something > like the clear_locks command in Solaris. That is, a way for an admin to > remove server-side locks held by a client that he knows is never going > to come back. With that, this sort of thing at least becomes a willful > act... Agreed on both counts. We should not be changing the semantics of either NFSv3 or NLM at this time. That will break existing setups that are treating NFSv3 as being a stable platform. As I've said in previous correspondence: NFSv4 already offers lease based locking. If people are worried about network partitions and/or locks being held by clients that are dead, then they can switch to that. On the other hand, a clear_locks command could be useful in order to tell a server that a given client is dead. It should be fairly easy to leverage the existing NSM/statd protocol to implement this. Trond