From nobody Sun Apr 12 21:47:41 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 67DBEC10F1B for ; Mon, 19 Dec 2022 17:08:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231840AbiLSRI4 (ORCPT ); Mon, 19 Dec 2022 12:08:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232339AbiLSRIe (ORCPT ); Mon, 19 Dec 2022 12:08:34 -0500 Received: from out30-42.freemail.mail.aliyun.com (out30-42.freemail.mail.aliyun.com [115.124.30.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF82C13D4F; Mon, 19 Dec 2022 09:08:23 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046056;MF=guwen@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0VXiBJum_1671469699; Received: from localhost(mailfrom:guwen@linux.alibaba.com fp:SMTPD_---0VXiBJum_1671469699) by smtp.aliyun-inc.com; Tue, 20 Dec 2022 01:08:21 +0800 From: Wen Gu To: kgraul@linux.ibm.com, wenjia@linux.ibm.com, jaka@linux.ibm.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH net-next 5/5] net/smc: logic of cursors update in SMC-D loopback connections Date: Tue, 20 Dec 2022 01:07:48 +0800 Message-Id: <1671469668-82691-6-git-send-email-guwen@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1671469668-82691-1-git-send-email-guwen@linux.alibaba.com> References: <1671469668-82691-1-git-send-email-guwen@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Since local sndbuf of SMC-D loopback connection shares the same physical memory region with peer RMB, the logic of cursors update needs to be adapted. The main difference from original implementation is need to ensure that the data copied to local sndbuf won't overwrite the unconsumed data of peer. So, for SMC-D loopback connections: 1. TX a. don't update fin_curs when send out cdc msg. b. fin_curs and sndbuf_space update will be deferred until receiving peer cons_curs update. 2. RX a. same as before. peer sndbuf is as large as local rmb, which guarantees that prod_curs will behind prep_curs. Signed-off-by: Wen Gu --- net/smc/smc_cdc.c | 53 +++++++++++++++++++++++++++++++++++++++-------= ---- net/smc/smc_loopback.c | 7 +++++++ 2 files changed, 49 insertions(+), 11 deletions(-) diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c index 61f5ff7..586472a 100644 --- a/net/smc/smc_cdc.c +++ b/net/smc/smc_cdc.c @@ -253,17 +253,26 @@ int smcd_cdc_msg_send(struct smc_connection *conn) return rc; smc_curs_copy(&conn->rx_curs_confirmed, &curs, conn); conn->local_rx_ctrl.prod_flags.cons_curs_upd_req =3D 0; - /* Calculate transmitted data and increment free send buffer space */ - diff =3D smc_curs_diff(conn->sndbuf_desc->len, &conn->tx_curs_fin, - &conn->tx_curs_sent); - /* increased by confirmed number of bytes */ - smp_mb__before_atomic(); - atomic_add(diff, &conn->sndbuf_space); - /* guarantee 0 <=3D sndbuf_space <=3D sndbuf_desc->len */ - smp_mb__after_atomic(); - smc_curs_copy(&conn->tx_curs_fin, &conn->tx_curs_sent, conn); + if (!conn->lgr->smcd->is_loopback) { + /* Note: + * For smcd loopback device: + * + * Don't update the fin_curs and sndbuf_space here. + * Update fin_curs when peer consumes the data in RMB. + */ =20 - smc_tx_sndbuf_nonfull(smc); + /* Calculate transmitted data and increment free send buffer space */ + diff =3D smc_curs_diff(conn->sndbuf_desc->len, &conn->tx_curs_fin, + &conn->tx_curs_sent); + /* increased by confirmed number of bytes */ + smp_mb__before_atomic(); + atomic_add(diff, &conn->sndbuf_space); + /* guarantee 0 <=3D sndbuf_space <=3D sndbuf_desc->len */ + smp_mb__after_atomic(); + smc_curs_copy(&conn->tx_curs_fin, &conn->tx_curs_sent, conn); + + smc_tx_sndbuf_nonfull(smc); + } return rc; } =20 @@ -321,7 +330,7 @@ static void smc_cdc_msg_recv_action(struct smc_sock *sm= c, { union smc_host_cursor cons_old, prod_old; struct smc_connection *conn =3D &smc->conn; - int diff_cons, diff_prod; + int diff_cons, diff_prod, diff_tx; =20 smc_curs_copy(&prod_old, &conn->local_rx_ctrl.prod, conn); smc_curs_copy(&cons_old, &conn->local_rx_ctrl.cons, conn); @@ -337,6 +346,28 @@ static void smc_cdc_msg_recv_action(struct smc_sock *s= mc, atomic_add(diff_cons, &conn->peer_rmbe_space); /* guarantee 0 <=3D peer_rmbe_space <=3D peer_rmbe_size */ smp_mb__after_atomic(); + + /* For smcd loopback device: + * Update of peer cons_curs indicates that + * 1. peer rmbe space increases. + * 2. local sndbuf space increases. + * + * So local sndbuf fin_curs should be equal to peer RMB cons_curs. + */ + if (conn->lgr->is_smcd && + conn->lgr->smcd->is_loopback) { + /* calculate peer rmb consumed data */ + diff_tx =3D smc_curs_diff(conn->sndbuf_desc->len, &conn->tx_curs_fin, + &conn->local_rx_ctrl.cons); + /* increase local sndbuf space and fin_curs */ + smp_mb__before_atomic(); + atomic_add(diff_tx, &conn->sndbuf_space); + /* guarantee 0 <=3D sndbuf_space <=3D sndbuf_desc->len */ + smp_mb__after_atomic(); + smc_curs_copy(&conn->tx_curs_fin, &conn->local_rx_ctrl.cons, conn); + + smc_tx_sndbuf_nonfull(smc); + } } =20 diff_prod =3D smc_curs_diff(conn->rmb_desc->len, &prod_old, diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c index 2c8540d..9b2bdf282 100644 --- a/net/smc/smc_loopback.c +++ b/net/smc/smc_loopback.c @@ -223,6 +223,13 @@ int lo_move_data(struct smcd_dev *smcd, u64 dmb_tok, u= nsigned int idx, struct lo_dmb_node *rmb_node =3D NULL, *tmp_node; struct lo_dev *ldev =3D smcd->priv; =20 + if (!sf) { + /* no need to move data. + * sndbuf is equal to peer rmb. + */ + return 0; + } + read_lock(&ldev->dmb_ht_lock); hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_tok) { if (tmp_node->token =3D=3D dmb_tok) { --=20 1.8.3.1