From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D47FEC433E6 for ; Thu, 7 Jan 2021 09:52:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A24682333F for ; Thu, 7 Jan 2021 09:52:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727989AbhAGJwG (ORCPT ); Thu, 7 Jan 2021 04:52:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41018 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727961AbhAGJv7 (ORCPT ); Thu, 7 Jan 2021 04:51:59 -0500 Received: from mail-ej1-x632.google.com (mail-ej1-x632.google.com [IPv6:2a00:1450:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 78DBAC0612FF for ; Thu, 7 Jan 2021 01:51:17 -0800 (PST) Received: by mail-ej1-x632.google.com with SMTP id qw4so8759405ejb.12 for ; Thu, 07 Jan 2021 01:51:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=Nem25OmsmkjNSBbvqZ41iqgC+QLTepbfzN5gUedefIM=; b=QTQfk6NwC9aHiSW6tnJLMlXC49jVo3IefyXWD0DWThFSllY63Yv3fUoW+YjVwpt25i uCA+UqbZKtGMIlv1RSc5ftENwzGJvR9YNjMSt4ZHkvYyRpDufgt15CSN+rnjiVZjjfDW 3wJfv2FZmNhs8vELqjCL12M/iDl9SKTnjpqUkpID2HEQONSpiy/Oz3vkiJOZFjgn3QSU 6BCew6hQqi9Xd+3p4evemicLXAhzqpZxuIUFhEvxhPPaRs3YI7Hoy/62Zwj+1apUox+m 9BXQsF36qHS4Y4gQuB2RCbljS642phou8/u9B2AWWkD5lvtGeBZyAe7jc8Ww2w/Y8IxY TMUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Nem25OmsmkjNSBbvqZ41iqgC+QLTepbfzN5gUedefIM=; b=HiteX04TuyXY0PzPmJ0qHfPRDZSkpxKWDBRi0Fh2p16KLITd/flpfJmLANMbYfhx/7 SfZR4yO9E/fDedAs229TUmJV6I025+y/1d5JOlYCcZyUwHLDwesPM7g8m3Ijt4HFwyh9 plIAFxEerIGnDFmgVYN+wMnDvOCIYHt5E0OypSoLtFGJXMOs+fMm7VEJdTzR6mCIsxQq e1AKsX7A0YAVmJXCbUIzuoq9k9dX/qLEGIZ60jxSVIyMF28Hux19syz/zi9RL7qiU574 u83fJ9JMsTJCx+8AmwByB86DRNKqJ0afWrE4mGVJdG1oD2tIFVbjHk1XQvRm6tN9vCvx c5vA== X-Gm-Message-State: AOAM532vXVUN7CwT2VPfFLqDPFVGe1MiLtzHzSlkJgpOoZnch8O2+QQw aWXXx1hN9Snj9g62dyxwUtqEU9DvbkgFNA== X-Google-Smtp-Source: ABdhPJywu7JlHdM+ODHSPcaQ4L3iYf8jBzPnnhNkefzoyske7RnJ1LBa0+3vUVnll1dtMJPUMiu18w== X-Received: by 2002:a17:906:c097:: with SMTP id f23mr5909527ejz.136.1610013076245; Thu, 07 Jan 2021 01:51:16 -0800 (PST) Received: from localhost.localdomain (5-12-227-87.residential.rdsnet.ro. [5.12.227.87]) by smtp.gmail.com with ESMTPSA id k15sm2251571ejc.79.2021.01.07.01.51.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Jan 2021 01:51:15 -0800 (PST) From: Vladimir Oltean To: "David S . Miller" , Jakub Kicinski Cc: netdev@vger.kernel.org, Andrew Lunn , Florian Fainelli , Cong Wang , Stephen Hemminger , Eric Dumazet , George McCollister , Oleksij Rempel , Jay Vosburgh , Veaceslav Falico , Andy Gospodarek , Arnd Bergmann , Taehee Yoo , Jiri Pirko , Florian Westphal Subject: [PATCH v3 net-next 09/12] net: net_failover: ensure .ndo_get_stats64 can sleep Date: Thu, 7 Jan 2021 11:49:48 +0200 Message-Id: <20210107094951.1772183-10-olteanv@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210107094951.1772183-1-olteanv@gmail.com> References: <20210107094951.1772183-1-olteanv@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Vladimir Oltean The failover framework sets up a virtio_net interface [ when it has the VIRTIO_NET_F_STANDBY feature ] and a VF interface, having the same MAC address, in a standby/active relationship. When the active VF is unplugged, the standby virtio_net temporarily kicks in. The failover framework registers a common upper for the active and the standby interface, which is what the application layer uses. This is similar to bonding/team. The statistics of the upper interface are the sum of the statistics of the active and of the standby interface. There is an effort to convert .ndo_get_stats64 to sleepable context, and for that to work, we need to prevent callers of dev_get_stats from using atomic locking. The failover driver needs protection via an RCU read-side critical section to access the standby and the active interface. This has two features: - It is atomic: this needs to change. - It is reentrant: this is ok, because generally speaking, dev_get_stats is recursive, and taking global locks is a bad thing from a recursive context. A better locking architecture would be to do what the team driver does. Instead of using something as broad as the rtnl_mutex to ensure serialization of updates, it should use something more specific, like a private mutex. This patch adds that and names it slaves_lock. The slaves_lock now protects the only updater, the rcu_assign_pointer sections from net_failover_slave_register. In the team driver, a separate lockdep class is created for each team lock, to account for possible nesting (team over team over ...). For the net_failover driver, we can do something simpler, which is to just not hold any lock while we call dev_get_stats recursively. We can "cheat" and use dev_hold to take a reference on the active and backup interfaces, and netdev_wait_allrefs() will just have to wait until we finish. Signed-off-by: Vladimir Oltean --- Changes in v3: None. Changes in v2: Switched to the new scheme of holding just a refcnt to the slave interfaces while recursing with dev_get_stats. drivers/net/net_failover.c | 62 +++++++++++++++++++++++++++----------- include/net/net_failover.h | 9 ++++-- 2 files changed, 52 insertions(+), 19 deletions(-) diff --git a/drivers/net/net_failover.c b/drivers/net/net_failover.c index 4f83165412bd..c83066b0ef70 100644 --- a/drivers/net/net_failover.c +++ b/drivers/net/net_failover.c @@ -27,6 +27,9 @@ #include #include +#define nfo_dereference(nfo_info, p) \ + rcu_dereference_protected(p, lockdep_is_held(&nfo_info->slaves_lock)) + static bool net_failover_xmit_ready(struct net_device *dev) { return netif_running(dev) && netif_carrier_ok(dev); @@ -183,32 +186,48 @@ static void net_failover_get_stats(struct net_device *dev, struct rtnl_link_stats64 *stats) { struct net_failover_info *nfo_info = netdev_priv(dev); - struct rtnl_link_stats64 temp; - struct net_device *slave_dev; + struct rtnl_link_stats64 primary_stats; + struct rtnl_link_stats64 standby_stats; + struct net_device *primary_dev; + struct net_device *standby_dev; - spin_lock(&nfo_info->stats_lock); - memcpy(stats, &nfo_info->failover_stats, sizeof(*stats)); + mutex_lock(&nfo_info->slaves_lock); - rcu_read_lock(); + primary_dev = nfo_dereference(nfo_info, nfo_info->primary_dev); + if (primary_dev) + dev_hold(primary_dev); - slave_dev = rcu_dereference(nfo_info->primary_dev); - if (slave_dev) { - dev_get_stats(slave_dev, &temp); - net_failover_fold_stats(stats, &temp, &nfo_info->primary_stats); - memcpy(&nfo_info->primary_stats, &temp, sizeof(temp)); + standby_dev = nfo_dereference(nfo_info, nfo_info->standby_dev); + if (standby_dev) + dev_hold(standby_dev); + + mutex_unlock(&nfo_info->slaves_lock); + + /* Don't hold slaves_lock while calling dev_get_stats, just a + * reference to ensure they won't get unregistered. + */ + if (primary_dev) { + dev_get_stats(primary_dev, &primary_stats); + dev_put(primary_dev); } - slave_dev = rcu_dereference(nfo_info->standby_dev); - if (slave_dev) { - dev_get_stats(slave_dev, &temp); - net_failover_fold_stats(stats, &temp, &nfo_info->standby_stats); - memcpy(&nfo_info->standby_stats, &temp, sizeof(temp)); + if (standby_dev) { + dev_get_stats(standby_dev, &standby_stats); + dev_put(standby_dev); } - rcu_read_unlock(); + mutex_lock(&nfo_info->stats_lock); + + memcpy(stats, &nfo_info->failover_stats, sizeof(*stats)); + + net_failover_fold_stats(stats, &primary_stats, &nfo_info->primary_stats); + memcpy(&nfo_info->primary_stats, &primary_stats, sizeof(primary_stats)); + net_failover_fold_stats(stats, &standby_stats, &nfo_info->standby_stats); + memcpy(&nfo_info->standby_stats, &standby_stats, sizeof(standby_stats)); memcpy(&nfo_info->failover_stats, stats, sizeof(*stats)); - spin_unlock(&nfo_info->stats_lock); + + mutex_unlock(&nfo_info->stats_lock); } static int net_failover_change_mtu(struct net_device *dev, int new_mtu) @@ -540,6 +559,8 @@ static int net_failover_slave_register(struct net_device *slave_dev, primary_dev = rtnl_dereference(nfo_info->primary_dev); slave_is_standby = slave_dev->dev.parent == failover_dev->dev.parent; + mutex_lock(&nfo_info->slaves_lock); + if (slave_is_standby) { rcu_assign_pointer(nfo_info->standby_dev, slave_dev); standby_dev = slave_dev; @@ -552,6 +573,8 @@ static int net_failover_slave_register(struct net_device *slave_dev, failover_dev->max_mtu = slave_dev->max_mtu; } + mutex_unlock(&nfo_info->slaves_lock); + net_failover_lower_state_changed(slave_dev, primary_dev, standby_dev); net_failover_compute_features(failover_dev); @@ -709,6 +732,7 @@ static struct failover_ops net_failover_ops = { struct failover *net_failover_create(struct net_device *standby_dev) { struct device *dev = standby_dev->dev.parent; + struct net_failover_info *nfo_info; struct net_device *failover_dev; struct failover *failover; int err; @@ -753,6 +777,10 @@ struct failover *net_failover_create(struct net_device *standby_dev) failover_dev->min_mtu = standby_dev->min_mtu; failover_dev->max_mtu = standby_dev->max_mtu; + nfo_info = netdev_priv(failover_dev); + mutex_init(&nfo_info->slaves_lock); + mutex_init(&nfo_info->stats_lock); + err = register_netdev(failover_dev); if (err) { dev_err(dev, "Unable to register failover_dev!\n"); diff --git a/include/net/net_failover.h b/include/net/net_failover.h index b12a1c469d1c..988cdfaf14ca 100644 --- a/include/net/net_failover.h +++ b/include/net/net_failover.h @@ -23,8 +23,13 @@ struct net_failover_info { /* aggregated stats */ struct rtnl_link_stats64 failover_stats; - /* spinlock while updating stats */ - spinlock_t stats_lock; + /* lock for updating stats */ + struct mutex stats_lock; + + /* lock for protecting lower interfaces. + * TODO: convert all rtnl_dereference instances to nfo_dereference + */ + struct mutex slaves_lock; }; struct failover *net_failover_create(struct net_device *standby_dev); -- 2.25.1