netdev - [PATCH net 3/3] net-device: move lstats in net_device_read

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Date: Thu,  8 Feb 2024 14:43:23 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, Naman Gulati <namangulati@...gle.com>, 
	Coco Li <lixiaoyan@...gle.com>, Wei Wang <weiwan@...gle.com>, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>, Simon Horman <horms@...nel.org>
Subject: [PATCH net 3/3] net-device: move lstats in net_device_read_txrx

dev->lstats is notably used from loopback ndo_start_xmit()
and other virtual drivers.

Per cpu stats updates are dirtying per-cpu data,
but the pointer itself is read-only.

Fixes: 43a71cd66b9c ("net-device: reorganize net_device fast path variables")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Coco Li <lixiaoyan@...gle.com>
Cc: Simon Horman <horms@...nel.org>
---
 Documentation/networking/net_cachelines/net_device.rst |  4 ++--
 include/linux/netdevice.h                              | 10 +++++-----
 net/core/dev.c                                         |  3 ++-
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/Documentation/networking/net_cachelines/net_device.rst b/Documentation/networking/net_cachelines/net_device.rst
index e75a53593bb9606f1c0595d8f7227881ec932b9c..dceb49d56a91158232543e920c7ed23bed74106e 100644
--- a/Documentation/networking/net_cachelines/net_device.rst
+++ b/Documentation/networking/net_cachelines/net_device.rst
@@ -136,8 +136,8 @@ struct_netpoll_info*                npinfo                  -
 possible_net_t                      nd_net                  -                   read_mostly         (dev_net)napi_busy_loop,tcp_v(4/6)_rcv,ip(v6)_rcv,ip(6)_input,ip(6)_input_finish
 void*                               ml_priv                                                         
 enum_netdev_ml_priv_type            ml_priv_type                                                    
-struct_pcpu_lstats__percpu*         lstats                                                          
-struct_pcpu_sw_netstats__percpu*    tstats                                                          
+struct_pcpu_lstats__percpu*         lstats                  read_mostly                             dev_lstats_add()
+struct_pcpu_sw_netstats__percpu*    tstats                  read_mostly                             dev_sw_netstats_tx_add()
 struct_pcpu_dstats__percpu*         dstats                                                          
 struct_garp_port*                   garp_port                                                       
 struct_mrp_port*                    mrp_port                                                        
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 118c40258d07b787adf518e576e75545e4bae846..ef7bfbb9849733fa7f1f097ba53a36a68cc3384b 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2141,6 +2141,11 @@ struct net_device {
 
 	/* TXRX read-mostly hotpath */
 	__cacheline_group_begin(net_device_read_txrx);
+	union {
+		struct pcpu_lstats __percpu		*lstats;
+		struct pcpu_sw_netstats __percpu	*tstats;
+		struct pcpu_dstats __percpu		*dstats;
+	};
 	unsigned int		flags;
 	unsigned short		hard_header_len;
 	netdev_features_t	features;
@@ -2395,11 +2400,6 @@ struct net_device {
 	enum netdev_ml_priv_type	ml_priv_type;
 
 	enum netdev_stat_type		pcpu_stat_type:8;
-	union {
-		struct pcpu_lstats __percpu		*lstats;
-		struct pcpu_sw_netstats __percpu	*tstats;
-		struct pcpu_dstats __percpu		*dstats;
-	};
 
 #if IS_ENABLED(CONFIG_GARP)
 	struct garp_port __rcu	*garp_port;
diff --git a/net/core/dev.c b/net/core/dev.c
index cb2dab0feee0abe758479a7a001342bf6613df08..9bb792cecc16f07449a91e4ca96357600d7453f9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11652,11 +11652,12 @@ static void __init net_dev_struct_check(void)
 	CACHELINE_ASSERT_GROUP_SIZE(struct net_device, net_device_read_tx, 160);
 
 	/* TXRX read-mostly hotpath */
+	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_txrx, lstats);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_txrx, flags);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_txrx, hard_header_len);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_txrx, features);
 	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_txrx, ip6_ptr);
-	CACHELINE_ASSERT_GROUP_SIZE(struct net_device, net_device_read_txrx, 30);
+	CACHELINE_ASSERT_GROUP_SIZE(struct net_device, net_device_read_txrx, 38);
 
 	/* RX read-mostly hotpath */
 	CACHELINE_ASSERT_GROUP_MEMBER(struct net_device, net_device_read_rx, ptype_specific);
-- 
2.43.0.594.gd9cf4e227d-goog