From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6848B30BB8E; Tue, 2 Sep 2025 14:29:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756823380; cv=none; b=Q2CWBghupFrTpUVx1Tj+pjhWErlyrnukddx6kKJP5Gqs0izZLgufbMnKmr+hV7NtyIur6pr/IUHELYVKsLnAbSyRFI1ZBbrBypy8LR1YL4h6CzpAlaBQVz+7Z1rN2hBMfXJRsosQxw2ZKzsRdSkNanZ4NK4S78+VVQ1+rQZenKU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756823380; c=relaxed/simple; bh=1zyqOsWCpBHLp7tk2b1nYjE1/RsNnyOSL4BtknCMfxU=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=JhZ/ifLBoIU8wDqEWA+8E2vKUTKoOcH/plOfWQRxUK5x7tFlDaMzJ1r8dXG8TTAfAvUWE0K+aCcabdmqHX9iXO+5VBsTbRzEHte8Lj/HR1o+8QBi+361ouJR4jnKtgNMaCFI3kCqzS92IBiOhUno4RllxGKfNsoQ5Z43b3jl7eQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ujlO/tZD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ujlO/tZD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CBA1EC4CEED; Tue, 2 Sep 2025 14:29:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756823379; bh=1zyqOsWCpBHLp7tk2b1nYjE1/RsNnyOSL4BtknCMfxU=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=ujlO/tZD/1299PYiYmgRwQZewByu4dUpPkYU5WVaafGsmseZz70JiWSei0NKZvL/+ 3THiQActmBSnyamODa9k4Cm2qKX3e3Cc1YwY1fpSClKnCR5/AFI0t9YQ+E4Qs965eG K8fQil50jNomzGPb7tfGpEU91RyY/E/I1WLG1YzQpLLCRYyrJgFHsF3yXyVz3v1F19 fSqJjbk4jzDhdkbwWxH6c0W2pSZ7GjIbY1d9xlyh29lD4x/1J5pjhh1ftkQIDKTZ+9 CQGfiVJWykj0ZjMbcspXLDQriKrMZdMDAkprTxYfUZVgFzJ5FrBHKxKbrY2y/lfocH ULuPEf8wzwcXg== Message-ID: <7f0c2dfbcebcacef8afa0b8d7cbdd6d84296cbcb.camel@kernel.org> Subject: Re: [PATCH] nfsd: remove long-standing revoked delegations by force From: Jeff Layton To: Li Lingfeng , chuck.lever@oracle.com, neil@brown.name, okorniev@redhat.com, Dai.Ngo@oracle.com, tom@talpey.com, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Cc: yukuai1@huaweicloud.com, houtao1@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com, lilingfeng@huaweicloud.com, zhangjian496@huawei.com Date: Tue, 02 Sep 2025 10:29:37 -0400 In-Reply-To: References: <20250902022237.1488709-1-lilingfeng3@huawei.com> <1ece2978-239c-4939-bb16-0c7c64614c66@huawei.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw 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Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-09-02 at 22:21 +0800, Li Lingfeng wrote: > =E5=9C=A8 2025/9/2 21:40, Jeff Layton =E5=86=99=E9=81=93: > > On Tue, 2025-09-02 at 20:10 +0800, Li Lingfeng wrote: > > > Hi, > > >=20 > > > =E5=9C=A8 2025/9/2 18:21, Jeff Layton =E5=86=99=E9=81=93: > > > > On Tue, 2025-09-02 at 10:22 +0800, Li Lingfeng wrote: > > > > > When file access conflicts occur between clients, the server reca= lls > > > > > delegations. If the client holding delegation fails to return it = after > > > > > a recall, nfs4_laundromat adds the delegation to cl_revoked list. > > > > > This causes subsequent SEQUENCE operations to set the > > > > > SEQ4_STATUS_RECALLABLE_STATE_REVOKED flag, forcing the client to > > > > > validate all delegations and return the revoked one. > > > > >=20 > > > > > However, if the client fails to return the delegation due to a ti= meout > > > > > after receiving the recall or a server bug, the delegation remain= s in the > > > > > server's cl_revoked list. The client marks it revoked and won't f= ind it > > > > > upon detecting SEQ4_STATUS_RECALLABLE_STATE_REVOKED. This leads t= o a loop: > > > > > the server persistently sets SEQ4_STATUS_RECALLABLE_STATE_REVOKED= , and the > > > > > client repeatedly tests all delegations, severely impacting perfo= rmance > > > > > when numerous delegations exist. > > > > >=20 > > > > It is a performance impact, but I don't get the "loop" here. Are yo= u > > > > saying that this problem compounds itself? That testing all delegat= ions > > > > causes others to be revoked? > > > The delegation will be removed from server->delegations in client aft= er > > > NFSPROC4_CLNT_DELEGRETURN is performed. > > > nfs4_delegreturn_done > > > =C2=A0nfs_delegation_mark_returned > > > =C2=A0 nfs_detach_delegation > > > =C2=A0 =C2=A0nfs_detach_delegation_locked > > > =C2=A0 =C2=A0 list_del_rcu // remove delegation from server->delega= tions > > >=20 > > > From the client's perspective, the delegation has been returned, bu= t on > > > the server side, it is left in the cl_revoked list.[1]. > > >=20 > > > Subsequently, every sequence from the client will be flagged with > > > SEQ4_STATUS_RECALLABLE_STATE_REVOKED as long as cl_revoked remains > > > non-empty. > > > nfsd4_sequence > > > =C2=A0seq->status_flags |=3D SEQ4_STATUS_RECALLABLE_STATE_REVOKED > > >=20 > > > When the client detects SEQ4_STATUS_RECALLABLE_STATE_REVOKED while > > > processing a sequence result, it sets NFS_DELEGATION_TEST_EXPIRED for= all > > > delegations and wakes up the state manager for handling. > > > nfs41_sequence_done > > > =C2=A0nfs41_sequence_process > > > =C2=A0 nfs41_handle_sequence_flag_errors > > > =C2=A0 =C2=A0nfs41_handle_recallable_state_revoked > > > =C2=A0 =C2=A0 nfs_test_expired_all_delegations > > > =C2=A0 =C2=A0 =C2=A0nfs_mark_test_expired_all_delegations > > > =C2=A0 =C2=A0 =C2=A0 nfs_delegation_mark_test_expired_server > > > =C2=A0 =C2=A0 =C2=A0 =C2=A0// set NFS_DELEGATION_TEST_EXPIRED for d= elegations in > > > server->delegations > > > =C2=A0 =C2=A0 =C2=A0nfs4_schedule_state_manager > > >=20 > > > The state manager tests all delegations except the one that was retur= ned, > > > as it is no longer in server->delegations. > > > nfs4_state_manager > > > =C2=A0nfs4_begin_drain_session > > > =C2=A0nfs_reap_expired_delegations > > > =C2=A0 nfs_server_reap_expired_delegations > > > =C2=A0 =C2=A0// test delegations in server->delegations > > >=20 > > > There may be a loop: > > > 1) send a sequence(client) > > > 2) return SEQ4_STATUS_RECALLABLE_STATE_REVOKED(server) > > > 3) set NFS_DELEGATION_TEST_EXPIRED for all delegations(client) > > > 4) test all delegations by state manager(client) > > > 5) send another sequence(client) > > >=20 > > > The state manager's traversal of delegations occurs between > > > nfs4_begin_drain_session and nfs4_end_drain_session. Non-privileged r= equests > > > will be blocked because the NFS4_SLOT_TBL_DRAINING flag is set. If th= ere are > > > many delegations to traverse, this blocking time can be relatively lo= ng. > > > > > Since abnormal delegations are removed from flc_lease via nfs4_la= undromat > > > > > --> revoke_delegation --> destroy_unhashed_deleg --> > > > > > nfs4_unlock_deleg_lease --> kernel_setlease, and do not block new= open > > > > > requests indefinitely, retaining such a delegation on the server = is > > > > > unnecessary. > > > > >=20 > > > > > Reported-by: Zhang Jian > > > > > Fixes: 3bd64a5ba171 ("nfsd4: implement SEQ4_STATUS_RECALLABLE_STA= TE_REVOKED") > > > > > Closes: https://lore.kernel.org/all/ff8debe9-6877-4cf7-ba29-fc98e= ae0ffa0@huawei.com/ > > > > > Signed-off-by: Li Lingfeng > > > > > --- > > > > > fs/nfsd/nfs4state.c | 11 +++++++++++ > > > > > 1 file changed, 11 insertions(+) > > > > >=20 > > > > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > > > > > index 88c347957da5..aa65a685dbb9 100644 > > > > > --- a/fs/nfsd/nfs4state.c > > > > > +++ b/fs/nfsd/nfs4state.c > > > > > @@ -4326,6 +4326,8 @@ nfsd4_sequence(struct svc_rqst *rqstp, stru= ct nfsd4_compound_state *cstate, > > > > > int buflen; > > > > > struct net *net =3D SVC_NET(rqstp); > > > > > struct nfsd_net *nn =3D net_generic(net, nfsd_net_id); > > > > > + struct list_head *pos, *next; > > > > > + struct nfs4_delegation *dp; > > > > > =20 > > > > > if (resp->opcnt !=3D 1) > > > > > return nfserr_sequence_pos; > > > > > @@ -4470,6 +4472,15 @@ nfsd4_sequence(struct svc_rqst *rqstp, str= uct nfsd4_compound_state *cstate, > > > > > default: > > > > > seq->status_flags =3D 0; > > > > > } > > > > > + if (!list_empty(&clp->cl_revoked)) { > > > > > + list_for_each_safe(pos, next, &clp->cl_revoked) { > > > > > + dp =3D list_entry(pos, struct nfs4_delegation, dl_recall_lru)= ; > > > > > + if (dp->dl_time < (ktime_get_boottime_seconds() - 2 * nn->nfs= d4_lease)) { > > > > > + list_del_init(&dp->dl_recall_lru); > > > > > + nfs4_put_stid(&dp->dl_stid); > > > > > + } > > > > > + } > > FYI: this list is protected by the clp->cl_lock. You need to hold it to > > do this list walk. > >=20 > > > > > + } > > > > > if (!list_empty(&clp->cl_revoked)) > > > > > seq->status_flags |=3D SEQ4_STATUS_RECALLABLE_STATE_REVOKED; > > > > > if (atomic_read(&clp->cl_admin_revoked)) > > > > This seems like a violation of the spec. AIUI, the server is requir= ed > > > > to hang onto a record of the delegation until the client does the > > > > TEST_STATEID/FREE_STATEID dance to remove it. Just discarding them = like > > > > this seems wrong. > > > Our expected outcome was that the client would release the abnormal > > > delegation via TEST_STATEID/FREE_STATEID upon detecting its invalidit= y. > > > However, this problematic delegation is no longer present in the > > > client's server->delegations list=E2=80=94whether due to client-side = timeouts or > > > the server-side bug [1]. > > > > Should we instead just administratively evict the client since it's > > > > clearly not behaving right in this case? > > > Thanks for the suggestion. While administratively evicting the client= would > > > certainly resolve the immediate delegation issue, I'm concerned that > > > approach > > > might be a bit heavy-handed. > > > The problematic behavior seems isolated to a single delegation. Meanw= hile, > > > the client itself likely has numerous other open files and active sta= te on > > > the server. Forcing a complete client reconnect would tear down all t= hat > > > state, which could cause significant application disruption and be pe= rceived > > > as a service outage from the client's perspective. > > >=20 > > > [1] > > > https://lore.kernel.org/all/de669327-c93a-49e5-a53b-bda9e67d34a2@huaw= ei.com/ > > >=20 > > > Thanks, > > > Lingfeng > > Ok, I get the problem, but I still disagree with the solution. I don't > > think we can just time these things out. Ideally we'd close the race > > window, but the sc_status field is protected by the global state_lock > > and I don't think we want to take it in revoke_delegation. > >=20 > > The best solution I can see is to have destroy_delegation() > > unconditionally set SC_STATUS_CLOSED, and then you can do the list walk > > above, but checking for that flag instead of testing for a timeout. > This might potentially affect the normal TEST_STATEID/FREE_STATEID flow, > as nfsd4_free_stateid() branches differently based on whether > SC_STATUS_CLOSED is set. Alternatively, I was wondering if you could > suggest a workaround to avoid this issue? >=20 I can't think of any workarounds other than turning off delegations altogether. I guess your concern is that TEST_STATEID and FREE_STATEID would return BAD_STATEID in this case, even though the entry was still (technically) on the cl_revoked list? That seems like correct behavior. The client did send DELEGRETURN, after all. > >=20 > > I'm still not thrilled with this solution though. It makes SEQUENCE a > > bit more heavyweight than I'd like. I'm starting to think that we need > > to rework the overall delegation locking, but that's an ugly problem to > > tackle. --=20 Jeff Layton