Return-Path: Received: from cn.fujitsu.com ([222.73.24.84]:59305 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750946Ab0IHBd6 (ORCPT ); Tue, 7 Sep 2010 21:33:58 -0400 Message-ID: <4C86E7FA.7020701@cn.fujitsu.com> Date: Wed, 08 Sep 2010 09:33:46 +0800 From: Bian Naimeng To: Trond Myklebust CC: linux-nfs@vger.kernel.org, "J. Bruce Fields" Subject: Re: [PATCH 2/2] We should clear NFS_DELEGATED_STATE after return delegation References: <4C592F85.8070308@cn.fujitsu.com> <4C59306A.9090302@cn.fujitsu.com> <1280925913.3011.23.camel@heimdal.trondhjem.org> <4C5A213F.9000506@cn.fujitsu.com> <1281013423.2948.1.camel@heimdal.trondhjem.org> <4C5B8B48.4050008@cn.fujitsu.com> <1281101448.3586.11.camel@heimdal.trondhjem.org> <4C68EDAE.5000201@cn.fujitsu.com> <1282087012.18385.30.camel@heimdal.trondhjem.org> <4C7DF56B.3040206@cn.fujitsu.com> <1283897068.9097.15.camel@heimdal.trondhjem.org> In-Reply-To: <1283897068.9097.15.camel@heimdal.trondhjem.org> Content-Type: text/plain; charset=Shift_JIS Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 >>> OK. I see agree that is a race, but AFAICS, your fix means that we end >>> up with an nfs_state structure that has cleared NFS_DELEGATED_STATE, but >>> that did not recover its open stateid. >>> >> Hi trond, what do you think about this one? > > Hi Bian, > > See comments/questions below. > Thanks for your answer. >> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c >> index 36400d3..c0c0320 100644 >> --- a/fs/nfs/nfs4proc.c >> +++ b/fs/nfs/nfs4proc.c >> @@ -900,8 +900,18 @@ static int update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_stat >> >> rcu_read_lock(); >> deleg_cur = rcu_dereference(nfsi->delegation); >> - if (deleg_cur == NULL) >> + if (deleg_cur == NULL) { >> + if (delegation == NULL && >> + test_bit(NFS_DELEGATED_STATE, &state->flags)) { > > Any reason why we can't ditch the 'test_bit'? > Because i am not sure it's ok that we just clear_bit at here. If you think it's ok, i'd be fine with removing this test_bit. >> + /*FIXME: If the state has NFS_DELEGATED_STATE bit, >> + * we catch a race. Maybe should recover its open >> + * stateid, here we just clear the NFS_DELEGATED_STATE >> + * bit. > > Can this ever be called with both deleg_cur==NULL and > open_stateid==NULL? If so, then we still have a bug. > Yes, i will add a checking. Thanks very much. >> + */ >> + clear_bit(NFS_DELEGATED_STATE, &state->flags); >> + } >> goto no_delegation; >> + } >> >> spin_lock(&deleg_cur->lock); >> if (nfsi->delegation != deleg_cur || -- Regards Bian Naimeng