From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 7E91E46F48B; Tue, 21 Jul 2026 19:43:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784663007; cv=none; b=SkSVRyqLEd3zo2wEaF8Zz85iaes7K1J16SYpS3jrQAzIo3MH7GwtEmCgn/DyjuY9FM5IhLjeauZWcsuW5/SFJOpwUH2sH+9byBwdHQjFgaM++9kjoDhjvD6w0MJPH7RbKkc/m7dmIYfpzReGDGF1kMmu94Q4IpqXk3kZIiqzlo0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784663007; c=relaxed/simple; bh=9GXISyiCNyjdWSXz0YqBrHl83X5/7U7eln0CXfOSbbI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ND+qv6Pwf4PdAaMyGUQxnIVNnH3HeWhIOxSwwJkY9QFBUww7Vg7HBavuig32rxHYDEjq/MA0khVVHkVkknIHylvhqwpPRyGHfEqfiO/QDPD5BmxVrl9d2hPZZDeq2DvGuFhEgJReANGPT43L++MEcQn1prPLuYRbyCAQZBJHr1A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xiOO3hLk; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xiOO3hLk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E50491F000E9; Tue, 21 Jul 2026 19:43:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784663006; bh=gZumLV07qvg4j7VtJvXjCCHehm07US+qe6J5purDnow=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=xiOO3hLkTcQpCeVsZ8R55SJgiXtj0f9IzWfpfY8HN92Jcxnue4MNVVUB9OUFzfgzP 3EW8MBNrOxxsCTKbl+yUfFy1uMvY5t47Tx0cFm/SQ64KaJpMReeDddIqEyPsZxjoMb 6w1ADLkGuOwwbmo2CZib4wAV5YiaqE/8DMJur0gA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kuniyuki Iwashima , Eric Dumazet , Paolo Abeni , Sasha Levin Subject: [PATCH 6.12 0661/1276] rtnetlink: Add per-netns RTNL. Date: Tue, 21 Jul 2026 17:18:24 +0200 Message-ID: <20260721152500.898462711@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152446.065700225@linuxfoundation.org> References: <20260721152446.065700225@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kuniyuki Iwashima [ Upstream commit 76aed95319da25d6884dff01d5f0149e4b542f96 ] The goal is to break RTNL down into per-netns mutex. This patch adds per-netns mutex and its helper functions, rtnl_net_lock() and rtnl_net_unlock(). rtnl_net_lock() acquires the global RTNL and per-netns RTNL mutex, and rtnl_net_unlock() releases them. We will replace 800+ rtnl_lock() with rtnl_net_lock() and finally removes rtnl_lock() in rtnl_net_lock(). When we need to nest per-netns RTNL mutex, we will use __rtnl_net_lock(), and its locking order is defined by rtnl_net_lock_cmp_fn() as follows: 1. init_net is first 2. netns address ascending order Note that the conversion will be done under CONFIG_DEBUG_NET_SMALL_RTNL with LOCKDEP so that we can carefully add the extra mutex without slowing down RTNL operations during conversion. Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Signed-off-by: Paolo Abeni Stable-dep-of: 17dc3b245de4 ("ipv6: fix missing notification for ignore_routes_with_linkdown") Signed-off-by: Sasha Levin --- include/linux/rtnetlink.h | 21 ++++++++++++++ include/net/net_namespace.h | 4 +++ net/Kconfig.debug | 15 ++++++++++ net/core/net_namespace.c | 6 ++++ net/core/rtnetlink.c | 58 +++++++++++++++++++++++++++++++++++++ 5 files changed, 104 insertions(+) diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h index a7da7dfc06a2a4..067098030ad2c6 100644 --- a/include/linux/rtnetlink.h +++ b/include/linux/rtnetlink.h @@ -95,6 +95,27 @@ static inline bool lockdep_rtnl_is_held(void) #define rcu_replace_pointer_rtnl(rp, p) \ rcu_replace_pointer(rp, p, lockdep_rtnl_is_held()) +#ifdef CONFIG_DEBUG_NET_SMALL_RTNL +void __rtnl_net_lock(struct net *net); +void __rtnl_net_unlock(struct net *net); +void rtnl_net_lock(struct net *net); +void rtnl_net_unlock(struct net *net); +int rtnl_net_lock_cmp_fn(const struct lockdep_map *a, const struct lockdep_map *b); +#else +static inline void __rtnl_net_lock(struct net *net) {} +static inline void __rtnl_net_unlock(struct net *net) {} + +static inline void rtnl_net_lock(struct net *net) +{ + rtnl_lock(); +} + +static inline void rtnl_net_unlock(struct net *net) +{ + rtnl_unlock(); +} +#endif + static inline struct netdev_queue *dev_ingress_queue(struct net_device *dev) { return rtnl_dereference(dev->ingress_queue); diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h index 022ee2fc627cff..47181fd749b256 100644 --- a/include/net/net_namespace.h +++ b/include/net/net_namespace.h @@ -189,6 +189,10 @@ struct net { #if IS_ENABLED(CONFIG_SMC) struct netns_smc smc; #endif +#ifdef CONFIG_DEBUG_NET_SMALL_RTNL + /* Move to a better place when the config guard is removed. */ + struct mutex rtnl_mutex; +#endif } __randomize_layout; #include diff --git a/net/Kconfig.debug b/net/Kconfig.debug index 5e3fffe707ddce..277fab8c4d77ca 100644 --- a/net/Kconfig.debug +++ b/net/Kconfig.debug @@ -24,3 +24,18 @@ config DEBUG_NET help Enable extra sanity checks in networking. This is mostly used by fuzzers, but is safe to select. + +config DEBUG_NET_SMALL_RTNL + bool "Add extra per-netns mutex inside RTNL" + depends on DEBUG_KERNEL && NET && LOCK_DEBUGGING_SUPPORT + select PROVE_LOCKING + default n + help + rtnl_lock() is being replaced with rtnl_net_lock() that + acquires the global RTNL and a small per-netns RTNL mutex. + + During the conversion, rtnl_net_lock() just adds an extra + mutex in every RTNL scope and slows down the operations. + + Once the conversion completes, rtnl_lock() will be removed + and rtnetlink will gain per-netns scalability. diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c index bb4ae3864ad256..cc03e3fd85fcdb 100644 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -334,6 +334,12 @@ static __net_init void preinit_net(struct net *net, struct user_namespace *user_ idr_init(&net->netns_ids); spin_lock_init(&net->nsid_lock); mutex_init(&net->ipv4.ra_mutex); + +#ifdef CONFIG_DEBUG_NET_SMALL_RTNL + mutex_init(&net->rtnl_mutex); + lock_set_cmp_fn(&net->rtnl_mutex, rtnl_net_lock_cmp_fn, NULL); +#endif + preinit_net_sysctl(net); } diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 118612325ce9e1..5b29f6ce12bc4a 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -179,6 +179,64 @@ bool lockdep_rtnl_is_held(void) EXPORT_SYMBOL(lockdep_rtnl_is_held); #endif /* #ifdef CONFIG_PROVE_LOCKING */ +#ifdef CONFIG_DEBUG_NET_SMALL_RTNL +void __rtnl_net_lock(struct net *net) +{ + ASSERT_RTNL(); + + mutex_lock(&net->rtnl_mutex); +} +EXPORT_SYMBOL(__rtnl_net_lock); + +void __rtnl_net_unlock(struct net *net) +{ + ASSERT_RTNL(); + + mutex_unlock(&net->rtnl_mutex); +} +EXPORT_SYMBOL(__rtnl_net_unlock); + +void rtnl_net_lock(struct net *net) +{ + rtnl_lock(); + __rtnl_net_lock(net); +} +EXPORT_SYMBOL(rtnl_net_lock); + +void rtnl_net_unlock(struct net *net) +{ + __rtnl_net_unlock(net); + rtnl_unlock(); +} +EXPORT_SYMBOL(rtnl_net_unlock); + +static int rtnl_net_cmp_locks(const struct net *net_a, const struct net *net_b) +{ + if (net_eq(net_a, net_b)) + return 0; + + /* always init_net first */ + if (net_eq(net_a, &init_net)) + return -1; + + if (net_eq(net_b, &init_net)) + return 1; + + /* otherwise lock in ascending order */ + return net_a < net_b ? -1 : 1; +} + +int rtnl_net_lock_cmp_fn(const struct lockdep_map *a, const struct lockdep_map *b) +{ + const struct net *net_a, *net_b; + + net_a = container_of(a, struct net, rtnl_mutex.dep_map); + net_b = container_of(b, struct net, rtnl_mutex.dep_map); + + return rtnl_net_cmp_locks(net_a, net_b); +} +#endif + static struct rtnl_link __rcu *__rcu *rtnl_msg_handlers[RTNL_FAMILY_MAX + 1]; static inline int rtm_msgindex(int msgtype) -- 2.53.0