From: Hans Wippel <hwippel@xxxxxxxxxxxxx> This patch splits up the functions smc_connect_rdma and smc_listen_work into smaller functions. Signed-off-by: Hans Wippel <hwippel@xxxxxxxxxxxxx> Signed-off-by: Ursula Braun <ubraun@xxxxxxxxxxxxx> --- net/smc/af_smc.c | 559 +++++++++++++++++++++++++++++++------------------------ 1 file changed, 318 insertions(+), 241 deletions(-) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 9871604ebb53..48530dab5c94 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -396,165 +396,186 @@ static void smc_link_save_peer_info(struct smc_link *link, link->peer_mtu = clc->qp_mtu; } -/* setup for RDMA connection of client */ -static int smc_connect_rdma(struct smc_sock *smc) +/* fall back during connect */ +static int smc_connect_fallback(struct smc_sock *smc) { - struct smc_clc_msg_accept_confirm aclc; - int local_contact = SMC_FIRST_CONTACT; - struct smc_ib_device *smcibdev; - struct smc_link *link; - u8 srv_first_contact; - int reason_code = 0; - int rc = 0; - u8 ibport; - - sock_hold(&smc->sk); /* sock put in passive closing */ + smc->use_fallback = true; + smc_copy_sock_settings_to_clc(smc); + if (smc->sk.sk_state == SMC_INIT) + smc->sk.sk_state = SMC_ACTIVE; + return 0; +} - if (smc->use_fallback) - goto out_connected; +/* decline and fall back during connect */ +static int smc_connect_decline_fallback(struct smc_sock *smc, int reason_code) +{ + int rc; - if (!tcp_sk(smc->clcsock->sk)->syn_smc) { - /* peer has not signalled SMC-capability */ - smc->use_fallback = true; - goto out_connected; + if (reason_code < 0) /* error, fallback is not possible */ + return reason_code; + if (reason_code != SMC_CLC_DECL_REPLY) { + rc = smc_clc_send_decline(smc, reason_code); + if (rc < 0) + return rc; } + return smc_connect_fallback(smc); +} - /* IPSec connections opt out of SMC-R optimizations */ - if (using_ipsec(smc)) { - reason_code = SMC_CLC_DECL_IPSEC; - goto decline_rdma; - } +/* abort connecting */ +static int smc_connect_abort(struct smc_sock *smc, int reason_code, + int local_contact) +{ + if (local_contact == SMC_FIRST_CONTACT) + smc_lgr_forget(smc->conn.lgr); + mutex_unlock(&smc_create_lgr_pending); + smc_conn_free(&smc->conn); + if (reason_code < 0 && smc->sk.sk_state == SMC_INIT) + sock_put(&smc->sk); /* passive closing */ + return reason_code; +} + +/* check if there is a rdma device available for this connection. */ +/* called for connect and listen */ +static int smc_check_rdma(struct smc_sock *smc, struct smc_ib_device **ibdev, + u8 *ibport) +{ + int reason_code = 0; /* PNET table look up: search active ib_device and port * within same PNETID that also contains the ethernet device * used for the internal TCP socket */ - smc_pnet_find_roce_resource(smc->clcsock->sk, &smcibdev, &ibport); - if (!smcibdev) { + smc_pnet_find_roce_resource(smc->clcsock->sk, ibdev, ibport); + if (!(*ibdev)) reason_code = SMC_CLC_DECL_CNFERR; /* configuration error */ - goto decline_rdma; - } + + return reason_code; +} + +/* CLC handshake during connect */ +static int smc_connect_clc(struct smc_sock *smc, + struct smc_clc_msg_accept_confirm *aclc, + struct smc_ib_device *ibdev, u8 ibport) +{ + int rc = 0; /* do inband token exchange */ - reason_code = smc_clc_send_proposal(smc, smcibdev, ibport); - if (reason_code < 0) { - rc = reason_code; - goto out_err; - } - if (reason_code > 0) /* configuration error */ - goto decline_rdma; + rc = smc_clc_send_proposal(smc, ibdev, ibport); + if (rc) + return rc; /* receive SMC Accept CLC message */ - reason_code = smc_clc_wait_msg(smc, &aclc, sizeof(aclc), - SMC_CLC_ACCEPT); - if (reason_code < 0) { - rc = reason_code; - goto out_err; - } - if (reason_code > 0) - goto decline_rdma; + return smc_clc_wait_msg(smc, aclc, sizeof(*aclc), SMC_CLC_ACCEPT); +} + +/* setup for RDMA connection of client */ +static int smc_connect_rdma(struct smc_sock *smc, + struct smc_clc_msg_accept_confirm *aclc, + struct smc_ib_device *ibdev, u8 ibport) +{ + int local_contact = SMC_FIRST_CONTACT; + struct smc_link *link; + int reason_code = 0; - srv_first_contact = aclc.hdr.flag; mutex_lock(&smc_create_lgr_pending); - local_contact = smc_conn_create(smc, smcibdev, ibport, &aclc.lcl, - srv_first_contact); + local_contact = smc_conn_create(smc, ibdev, ibport, &aclc->lcl, + aclc->hdr.flag); if (local_contact < 0) { - rc = local_contact; - if (rc == -ENOMEM) + if (local_contact == -ENOMEM) reason_code = SMC_CLC_DECL_MEM;/* insufficient memory*/ - else if (rc == -ENOLINK) + else if (local_contact == -ENOLINK) reason_code = SMC_CLC_DECL_SYNCERR; /* synchr. error */ else reason_code = SMC_CLC_DECL_INTERR; /* other error */ - goto decline_rdma_unlock; + return smc_connect_abort(smc, reason_code, 0); } link = &smc->conn.lgr->lnk[SMC_SINGLE_LINK]; - smc_conn_save_peer_info(smc, &aclc); + smc_conn_save_peer_info(smc, aclc); /* create send buffer and rmb */ - rc = smc_buf_create(smc); - if (rc) { - reason_code = SMC_CLC_DECL_MEM; - goto decline_rdma_unlock; - } + if (smc_buf_create(smc)) + return smc_connect_abort(smc, SMC_CLC_DECL_MEM, local_contact); if (local_contact == SMC_FIRST_CONTACT) - smc_link_save_peer_info(link, &aclc); + smc_link_save_peer_info(link, aclc); - rc = smc_rmb_rtoken_handling(&smc->conn, &aclc); - if (rc) { - reason_code = SMC_CLC_DECL_INTERR; - goto decline_rdma_unlock; - } + if (smc_rmb_rtoken_handling(&smc->conn, aclc)) + return smc_connect_abort(smc, SMC_CLC_DECL_INTERR, + local_contact); smc_close_init(smc); smc_rx_init(smc); if (local_contact == SMC_FIRST_CONTACT) { - rc = smc_ib_ready_link(link); - if (rc) { - reason_code = SMC_CLC_DECL_INTERR; - goto decline_rdma_unlock; - } + if (smc_ib_ready_link(link)) + return smc_connect_abort(smc, SMC_CLC_DECL_INTERR, + local_contact); } else { - if (!smc->conn.rmb_desc->reused) { - if (smc_reg_rmb(link, smc->conn.rmb_desc, true)) { - reason_code = SMC_CLC_DECL_INTERR; - goto decline_rdma_unlock; - } - } + if (!smc->conn.rmb_desc->reused && + smc_reg_rmb(link, smc->conn.rmb_desc, true)) + return smc_connect_abort(smc, SMC_CLC_DECL_INTERR, + local_contact); } smc_rmb_sync_sg_for_device(&smc->conn); - rc = smc_clc_send_confirm(smc); - if (rc) - goto out_err_unlock; + reason_code = smc_clc_send_confirm(smc); + if (reason_code) + return smc_connect_abort(smc, reason_code, local_contact); + + smc_tx_init(smc); if (local_contact == SMC_FIRST_CONTACT) { /* QP confirmation over RoCE fabric */ reason_code = smc_clnt_conf_first_link(smc); - if (reason_code < 0) { - rc = reason_code; - goto out_err_unlock; - } - if (reason_code > 0) - goto decline_rdma_unlock; + if (reason_code) + return smc_connect_abort(smc, reason_code, + local_contact); } - mutex_unlock(&smc_create_lgr_pending); - smc_tx_init(smc); -out_connected: smc_copy_sock_settings_to_clc(smc); if (smc->sk.sk_state == SMC_INIT) smc->sk.sk_state = SMC_ACTIVE; - return rc ? rc : local_contact; + return 0; +} -decline_rdma_unlock: - if (local_contact == SMC_FIRST_CONTACT) - smc_lgr_forget(smc->conn.lgr); - mutex_unlock(&smc_create_lgr_pending); - smc_conn_free(&smc->conn); -decline_rdma: - /* RDMA setup failed, switch back to TCP */ - smc->use_fallback = true; - if (reason_code && (reason_code != SMC_CLC_DECL_REPLY)) { - rc = smc_clc_send_decline(smc, reason_code); - if (rc < 0) - goto out_err; - } - goto out_connected; +/* perform steps before actually connecting */ +static int __smc_connect(struct smc_sock *smc) +{ + struct smc_clc_msg_accept_confirm aclc; + struct smc_ib_device *ibdev; + int rc = 0; + u8 ibport; -out_err_unlock: - if (local_contact == SMC_FIRST_CONTACT) - smc_lgr_forget(smc->conn.lgr); - mutex_unlock(&smc_create_lgr_pending); - smc_conn_free(&smc->conn); -out_err: - if (smc->sk.sk_state == SMC_INIT) - sock_put(&smc->sk); /* passive closing */ - return rc; + sock_hold(&smc->sk); /* sock put in passive closing */ + + if (smc->use_fallback) + return smc_connect_fallback(smc); + + /* if peer has not signalled SMC-capability, fall back */ + if (!tcp_sk(smc->clcsock->sk)->syn_smc) + return smc_connect_fallback(smc); + + /* IPSec connections opt out of SMC-R optimizations */ + if (using_ipsec(smc)) + return smc_connect_decline_fallback(smc, SMC_CLC_DECL_IPSEC); + + /* check if a RDMA device is available; if not, fall back */ + if (smc_check_rdma(smc, &ibdev, &ibport)) + return smc_connect_decline_fallback(smc, SMC_CLC_DECL_CNFERR); + + /* perform CLC handshake */ + rc = smc_connect_clc(smc, &aclc, ibdev, ibport); + if (rc) + return smc_connect_decline_fallback(smc, rc); + + /* connect using rdma */ + rc = smc_connect_rdma(smc, &aclc, ibdev, ibport); + if (rc) + return smc_connect_decline_fallback(smc, rc); + + return 0; } static int smc_connect(struct socket *sock, struct sockaddr *addr, @@ -590,8 +611,7 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr, if (rc) goto out; - /* setup RDMA connection */ - rc = smc_connect_rdma(smc); + rc = __smc_connect(smc); if (rc < 0) goto out; else @@ -789,182 +809,239 @@ static int smc_serv_conf_first_link(struct smc_sock *smc) return 0; } -/* setup for RDMA connection of server */ -static void smc_listen_work(struct work_struct *work) +/* listen worker: finish */ +static void smc_listen_out(struct smc_sock *new_smc) { - struct smc_sock *new_smc = container_of(work, struct smc_sock, - smc_listen_work); - struct smc_clc_msg_proposal_prefix *pclc_prfx; - struct socket *newclcsock = new_smc->clcsock; struct smc_sock *lsmc = new_smc->listen_smc; - struct smc_clc_msg_accept_confirm cclc; - int local_contact = SMC_REUSE_CONTACT; struct sock *newsmcsk = &new_smc->sk; - struct smc_clc_msg_proposal *pclc; - struct smc_ib_device *smcibdev; - u8 buf[SMC_CLC_MAX_LEN]; - struct smc_link *link; - int reason_code = 0; - int rc = 0; - u8 ibport; - if (new_smc->use_fallback) - goto out_connected; - - /* check if peer is smc capable */ - if (!tcp_sk(newclcsock->sk)->syn_smc) { - new_smc->use_fallback = true; - goto out_connected; + lock_sock_nested(&lsmc->sk, SINGLE_DEPTH_NESTING); + if (lsmc->sk.sk_state == SMC_LISTEN) { + smc_accept_enqueue(&lsmc->sk, newsmcsk); + } else { /* no longer listening */ + smc_close_non_accepted(newsmcsk); } + release_sock(&lsmc->sk); - /* do inband token exchange - - *wait for and receive SMC Proposal CLC message - */ - reason_code = smc_clc_wait_msg(new_smc, &buf, sizeof(buf), - SMC_CLC_PROPOSAL); - if (reason_code < 0) - goto out_err; - if (reason_code > 0) - goto decline_rdma; + /* Wake up accept */ + lsmc->sk.sk_data_ready(&lsmc->sk); + sock_put(&lsmc->sk); /* sock_hold in smc_tcp_listen_work */ +} - /* IPSec connections opt out of SMC-R optimizations */ - if (using_ipsec(new_smc)) { - reason_code = SMC_CLC_DECL_IPSEC; - goto decline_rdma; - } +/* listen worker: finish in state connected */ +static void smc_listen_out_connected(struct smc_sock *new_smc) +{ + struct sock *newsmcsk = &new_smc->sk; - /* PNET table look up: search active ib_device and port - * within same PNETID that also contains the ethernet device - * used for the internal TCP socket - */ - smc_pnet_find_roce_resource(newclcsock->sk, &smcibdev, &ibport); - if (!smcibdev) { - reason_code = SMC_CLC_DECL_CNFERR; /* configuration error */ - goto decline_rdma; + sk_refcnt_debug_inc(newsmcsk); + if (newsmcsk->sk_state == SMC_INIT) + newsmcsk->sk_state = SMC_ACTIVE; + + smc_listen_out(new_smc); +} + +/* listen worker: finish in error state */ +static void smc_listen_out_err(struct smc_sock *new_smc) +{ + struct sock *newsmcsk = &new_smc->sk; + + if (newsmcsk->sk_state == SMC_INIT) + sock_put(&new_smc->sk); /* passive closing */ + newsmcsk->sk_state = SMC_CLOSED; + smc_conn_free(&new_smc->conn); + + smc_listen_out(new_smc); +} + +/* listen worker: decline and fall back if possible */ +static void smc_listen_decline(struct smc_sock *new_smc, int reason_code, + int local_contact) +{ + /* RDMA setup failed, switch back to TCP */ + if (local_contact == SMC_FIRST_CONTACT) + smc_lgr_forget(new_smc->conn.lgr); + if (reason_code < 0) { /* error, no fallback possible */ + smc_listen_out_err(new_smc); + return; + } + smc_conn_free(&new_smc->conn); + new_smc->use_fallback = true; + if (reason_code && reason_code != SMC_CLC_DECL_REPLY) { + if (smc_clc_send_decline(new_smc, reason_code) < 0) { + smc_listen_out_err(new_smc); + return; + } } + smc_listen_out_connected(new_smc); +} + +/* listen worker: check prefixes */ +static int smc_listen_rdma_check(struct smc_sock *new_smc, + struct smc_clc_msg_proposal *pclc) +{ + struct smc_clc_msg_proposal_prefix *pclc_prfx; + struct socket *newclcsock = new_smc->clcsock; - pclc = (struct smc_clc_msg_proposal *)&buf; pclc_prfx = smc_clc_proposal_get_prefix(pclc); + if (smc_clc_prfx_match(newclcsock, pclc_prfx)) + return SMC_CLC_DECL_CNFERR; - rc = smc_clc_prfx_match(newclcsock, pclc_prfx); - if (rc) { - reason_code = SMC_CLC_DECL_CNFERR; /* configuration error */ - goto decline_rdma; - } + return 0; +} +/* listen worker: initialize connection and buffers */ +static int smc_listen_rdma_init(struct smc_sock *new_smc, + struct smc_clc_msg_proposal *pclc, + struct smc_ib_device *ibdev, u8 ibport, + int *local_contact) +{ /* allocate connection / link group */ - mutex_lock(&smc_create_lgr_pending); - local_contact = smc_conn_create(new_smc, smcibdev, ibport, &pclc->lcl, - 0); - if (local_contact < 0) { - rc = local_contact; - if (rc == -ENOMEM) - reason_code = SMC_CLC_DECL_MEM;/* insufficient memory*/ - goto decline_rdma_unlock; + *local_contact = smc_conn_create(new_smc, ibdev, ibport, &pclc->lcl, 0); + if (*local_contact < 0) { + if (*local_contact == -ENOMEM) + return SMC_CLC_DECL_MEM;/* insufficient memory*/ + return SMC_CLC_DECL_INTERR; /* other error */ } - link = &new_smc->conn.lgr->lnk[SMC_SINGLE_LINK]; /* create send buffer and rmb */ - rc = smc_buf_create(new_smc); - if (rc) { - reason_code = SMC_CLC_DECL_MEM; - goto decline_rdma_unlock; - } + if (smc_buf_create(new_smc)) + return SMC_CLC_DECL_MEM; - smc_close_init(new_smc); - smc_rx_init(new_smc); + return 0; +} + +/* listen worker: register buffers */ +static int smc_listen_rdma_reg(struct smc_sock *new_smc, int local_contact) +{ + struct smc_link *link = &new_smc->conn.lgr->lnk[SMC_SINGLE_LINK]; if (local_contact != SMC_FIRST_CONTACT) { if (!new_smc->conn.rmb_desc->reused) { - if (smc_reg_rmb(link, new_smc->conn.rmb_desc, true)) { - reason_code = SMC_CLC_DECL_INTERR; - goto decline_rdma_unlock; - } + if (smc_reg_rmb(link, new_smc->conn.rmb_desc, true)) + return SMC_CLC_DECL_INTERR; } } smc_rmb_sync_sg_for_device(&new_smc->conn); - rc = smc_clc_send_accept(new_smc, local_contact); - if (rc) - goto out_err_unlock; + return 0; +} + +/* listen worker: finish RDMA setup */ +static void smc_listen_rdma_finish(struct smc_sock *new_smc, + struct smc_clc_msg_accept_confirm *cclc, + int local_contact) +{ + struct smc_link *link = &new_smc->conn.lgr->lnk[SMC_SINGLE_LINK]; + int reason_code = 0; - /* receive SMC Confirm CLC message */ - reason_code = smc_clc_wait_msg(new_smc, &cclc, sizeof(cclc), - SMC_CLC_CONFIRM); - if (reason_code < 0) - goto out_err_unlock; - if (reason_code > 0) - goto decline_rdma_unlock; - smc_conn_save_peer_info(new_smc, &cclc); if (local_contact == SMC_FIRST_CONTACT) - smc_link_save_peer_info(link, &cclc); + smc_link_save_peer_info(link, cclc); - rc = smc_rmb_rtoken_handling(&new_smc->conn, &cclc); - if (rc) { + if (smc_rmb_rtoken_handling(&new_smc->conn, cclc)) { reason_code = SMC_CLC_DECL_INTERR; - goto decline_rdma_unlock; + goto decline; } if (local_contact == SMC_FIRST_CONTACT) { - rc = smc_ib_ready_link(link); - if (rc) { + if (smc_ib_ready_link(link)) { reason_code = SMC_CLC_DECL_INTERR; - goto decline_rdma_unlock; + goto decline; } /* QP confirmation over RoCE fabric */ reason_code = smc_serv_conf_first_link(new_smc); - if (reason_code < 0) - /* peer is not aware of a problem */ - goto out_err_unlock; - if (reason_code > 0) - goto decline_rdma_unlock; + if (reason_code) + goto decline; } + return; - smc_tx_init(new_smc); +decline: mutex_unlock(&smc_create_lgr_pending); + smc_listen_decline(new_smc, reason_code, local_contact); +} -out_connected: - sk_refcnt_debug_inc(newsmcsk); - if (newsmcsk->sk_state == SMC_INIT) - newsmcsk->sk_state = SMC_ACTIVE; -enqueue: - lock_sock_nested(&lsmc->sk, SINGLE_DEPTH_NESTING); - if (lsmc->sk.sk_state == SMC_LISTEN) { - smc_accept_enqueue(&lsmc->sk, newsmcsk); - } else { /* no longer listening */ - smc_close_non_accepted(newsmcsk); +/* setup for RDMA connection of server */ +static void smc_listen_work(struct work_struct *work) +{ + struct smc_sock *new_smc = container_of(work, struct smc_sock, + smc_listen_work); + struct socket *newclcsock = new_smc->clcsock; + struct smc_clc_msg_accept_confirm cclc; + struct smc_clc_msg_proposal *pclc; + struct smc_ib_device *ibdev; + u8 buf[SMC_CLC_MAX_LEN]; + int local_contact = 0; + int reason_code = 0; + int rc = 0; + u8 ibport; + + if (new_smc->use_fallback) { + smc_listen_out_connected(new_smc); + return; } - release_sock(&lsmc->sk); - /* Wake up accept */ - lsmc->sk.sk_data_ready(&lsmc->sk); - sock_put(&lsmc->sk); /* sock_hold in smc_tcp_listen_work */ - return; + /* check if peer is smc capable */ + if (!tcp_sk(newclcsock->sk)->syn_smc) { + new_smc->use_fallback = true; + smc_listen_out_connected(new_smc); + return; + } -decline_rdma_unlock: - if (local_contact == SMC_FIRST_CONTACT) - smc_lgr_forget(new_smc->conn.lgr); - mutex_unlock(&smc_create_lgr_pending); -decline_rdma: - /* RDMA setup failed, switch back to TCP */ - smc_conn_free(&new_smc->conn); - new_smc->use_fallback = true; - if (reason_code && (reason_code != SMC_CLC_DECL_REPLY)) { - if (smc_clc_send_decline(new_smc, reason_code) < 0) - goto out_err; + /* do inband token exchange - + * wait for and receive SMC Proposal CLC message + */ + pclc = (struct smc_clc_msg_proposal *)&buf; + reason_code = smc_clc_wait_msg(new_smc, pclc, SMC_CLC_MAX_LEN, + SMC_CLC_PROPOSAL); + if (reason_code) { + smc_listen_decline(new_smc, reason_code, 0); + return; } - goto out_connected; -out_err_unlock: - if (local_contact == SMC_FIRST_CONTACT) - smc_lgr_forget(new_smc->conn.lgr); + /* IPSec connections opt out of SMC-R optimizations */ + if (using_ipsec(new_smc)) { + smc_listen_decline(new_smc, SMC_CLC_DECL_IPSEC, 0); + return; + } + + mutex_lock(&smc_create_lgr_pending); + smc_close_init(new_smc); + smc_rx_init(new_smc); + smc_tx_init(new_smc); + + /* check if RDMA is available */ + if (smc_check_rdma(new_smc, &ibdev, &ibport) || + smc_listen_rdma_check(new_smc, pclc) || + smc_listen_rdma_init(new_smc, pclc, ibdev, ibport, + &local_contact) || + smc_listen_rdma_reg(new_smc, local_contact)) { + /* SMC not supported, decline */ + mutex_unlock(&smc_create_lgr_pending); + smc_listen_decline(new_smc, SMC_CLC_DECL_CNFERR, local_contact); + return; + } + + /* send SMC Accept CLC message */ + rc = smc_clc_send_accept(new_smc, local_contact); + if (rc) { + mutex_unlock(&smc_create_lgr_pending); + smc_listen_decline(new_smc, rc, local_contact); + return; + } + + /* receive SMC Confirm CLC message */ + reason_code = smc_clc_wait_msg(new_smc, &cclc, sizeof(cclc), + SMC_CLC_CONFIRM); + if (reason_code) { + mutex_unlock(&smc_create_lgr_pending); + smc_listen_decline(new_smc, reason_code, local_contact); + return; + } + + /* finish worker */ + smc_listen_rdma_finish(new_smc, &cclc, local_contact); + smc_conn_save_peer_info(new_smc, &cclc); mutex_unlock(&smc_create_lgr_pending); -out_err: - if (newsmcsk->sk_state == SMC_INIT) - sock_put(&new_smc->sk); /* passive closing */ - newsmcsk->sk_state = SMC_CLOSED; - smc_conn_free(&new_smc->conn); - goto enqueue; /* queue new sock with sk_err set */ + smc_listen_out_connected(new_smc); } static void smc_tcp_listen_work(struct work_struct *work) @@ -1225,7 +1302,7 @@ static __poll_t smc_poll(struct file *file, struct socket *sock, if (sk->sk_state == SMC_INIT && mask & EPOLLOUT && smc->clcsock->sk->sk_state != TCP_CLOSE) { - rc = smc_connect_rdma(smc); + rc = __smc_connect(smc); if (rc < 0) mask |= EPOLLERR; /* success cases including fallback */ -- 2.16.3 -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html