[PATCH net-next-2.6 1/2] net: Get rid of rtnl_link_stats64 / net_device_stats union

[PATCH net-next-2.6 1/2] net: Get rid of rtnl_link_stats64 / net_device_stats union

[Ben Hutchings]

In commit be1f3c2c027cc5ad735df6a45a542ed1db7ec48b "net: Enable 64-bit
net device statistics on 32-bit architectures" I redefined struct
net_device_stats so that it could be used in a union with struct
rtnl_link_stats64, avoiding the need for explicit copying or
conversion between the two.  However, this is unsafe because there is
no locking required and no lock consistently held around calls to
dev_get_stats() and use of the statistics structure it returns.

In commit 28172739f0a276eb8d6ca917b3974c2edb036da3 "net: fix 64 bit
counters on 32 bit arches" Eric Dumazet dealt with that problem by
requiring callers of dev_get_stats() to provide storage for the
result.  This means that the net_device::stats64 field and the padding
in struct net_device_stats are now redundant, so remove them.

Update the comment on net_device_ops::ndo_get_stats64 to reflect its
new usage.

Change dev_txq_stats_fold() to use struct rtnl_link_stats64, since
that is what all its callers are really using and it is no longer
going to be compatible with struct net_device_stats.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
 drivers/net/macvlan.c     |    2 +-
 include/linux/netdevice.h |   70 ++++++++++++++++++---------------------------
 net/8021q/vlan_dev.c      |    2 +-
 net/core/dev.c            |   19 +++++++++---
 4 files changed, 44 insertions(+), 49 deletions(-)

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 6112f14..1b28aae 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -436,7 +436,7 @@ static struct rtnl_link_stats64 *macvlan_dev_get_stats64(struct net_device *dev,
 {
 	struct macvlan_dev *vlan = netdev_priv(dev);
 
-	dev_txq_stats_fold(dev, (struct net_device_stats *)stats);
+	dev_txq_stats_fold(dev, stats);
 
 	if (vlan->rx_stats) {
 		struct macvlan_rx_stats *p, accum = {0};
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8018f6b..17e95e3 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -162,42 +162,32 @@ static inline bool dev_xmit_complete(int rc)
 /*
  *	Old network device statistics. Fields are native words
  *	(unsigned long) so they can be read and written atomically.
- *	Each field is padded to 64 bits for compatibility with
- *	rtnl_link_stats64.
  */
 
-#if BITS_PER_LONG == 64
-#define NET_DEVICE_STATS_DEFINE(name)	unsigned long name
-#elif defined(__LITTLE_ENDIAN)
-#define NET_DEVICE_STATS_DEFINE(name)	unsigned long name, pad_ ## name
-#else
-#define NET_DEVICE_STATS_DEFINE(name)	unsigned long pad_ ## name, name
-#endif
-
 struct net_device_stats {
-	NET_DEVICE_STATS_DEFINE(rx_packets);
-	NET_DEVICE_STATS_DEFINE(tx_packets);
-	NET_DEVICE_STATS_DEFINE(rx_bytes);
-	NET_DEVICE_STATS_DEFINE(tx_bytes);
-	NET_DEVICE_STATS_DEFINE(rx_errors);
-	NET_DEVICE_STATS_DEFINE(tx_errors);
-	NET_DEVICE_STATS_DEFINE(rx_dropped);
-	NET_DEVICE_STATS_DEFINE(tx_dropped);
-	NET_DEVICE_STATS_DEFINE(multicast);
-	NET_DEVICE_STATS_DEFINE(collisions);
-	NET_DEVICE_STATS_DEFINE(rx_length_errors);
-	NET_DEVICE_STATS_DEFINE(rx_over_errors);
-	NET_DEVICE_STATS_DEFINE(rx_crc_errors);
-	NET_DEVICE_STATS_DEFINE(rx_frame_errors);
-	NET_DEVICE_STATS_DEFINE(rx_fifo_errors);
-	NET_DEVICE_STATS_DEFINE(rx_missed_errors);
-	NET_DEVICE_STATS_DEFINE(tx_aborted_errors);
-	NET_DEVICE_STATS_DEFINE(tx_carrier_errors);
-	NET_DEVICE_STATS_DEFINE(tx_fifo_errors);
-	NET_DEVICE_STATS_DEFINE(tx_heartbeat_errors);
-	NET_DEVICE_STATS_DEFINE(tx_window_errors);
-	NET_DEVICE_STATS_DEFINE(rx_compressed);
-	NET_DEVICE_STATS_DEFINE(tx_compressed);
+	unsigned long	rx_packets;
+	unsigned long	tx_packets;
+	unsigned long	rx_bytes;
+	unsigned long	tx_bytes;
+	unsigned long	rx_errors;
+	unsigned long	tx_errors;
+	unsigned long	rx_dropped;
+	unsigned long	tx_dropped;
+	unsigned long	multicast;
+	unsigned long	collisions;
+	unsigned long	rx_length_errors;
+	unsigned long	rx_over_errors;
+	unsigned long	rx_crc_errors;
+	unsigned long	rx_frame_errors;
+	unsigned long	rx_fifo_errors;
+	unsigned long	rx_missed_errors;
+	unsigned long	tx_aborted_errors;
+	unsigned long	tx_carrier_errors;
+	unsigned long	tx_fifo_errors;
+	unsigned long	tx_heartbeat_errors;
+	unsigned long	tx_window_errors;
+	unsigned long	rx_compressed;
+	unsigned long	tx_compressed;
 };
 
 #endif  /*  __KERNEL__  */
@@ -666,14 +656,13 @@ struct netdev_rx_queue {
  *	Callback uses when the transmitter has not made any progress
  *	for dev->watchdog ticks.
  *
- * struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev
+ * struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev,
  *                      struct rtnl_link_stats64 *storage);
  * struct net_device_stats* (*ndo_get_stats)(struct net_device *dev);
  *	Called when a user wants to get the network device usage
  *	statistics. Drivers must do one of the following:
- *	1. Define @ndo_get_stats64 to update a rtnl_link_stats64 structure
- *	   (which should normally be dev->stats64) and return a ponter to
- *	   it. The structure must not be changed asynchronously.
+ *	1. Define @ndo_get_stats64 to fill in a zero-initialised
+ *	   rtnl_link_stats64 structure passed by the caller.
  *	2. Define @ndo_get_stats to update a net_device_stats structure
  *	   (which should normally be dev->stats) and return a pointer to
  *	   it. The structure may be changed asynchronously only if each
@@ -888,10 +877,7 @@ struct net_device {
 	int			ifindex;
 	int			iflink;
 
-	union {
-		struct rtnl_link_stats64 stats64;
-		struct net_device_stats stats;
-	};
+	struct net_device_stats	stats;
 
 #ifdef CONFIG_WIRELESS_EXT
 	/* List of functions to handle Wireless Extensions (instead of ioctl).
@@ -2147,7 +2133,7 @@ extern void		dev_mcast_init(void);
 extern const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
 						     struct rtnl_link_stats64 *storage);
 extern void		dev_txq_stats_fold(const struct net_device *dev,
-					   struct net_device_stats *stats);
+					   struct rtnl_link_stats64 *stats);
 
 extern int		netdev_max_backlog;
 extern int		netdev_tstamp_prequeue;
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 7865a4c..e66c9bf 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -805,7 +805,7 @@ static u32 vlan_ethtool_get_flags(struct net_device *dev)
 
 static struct rtnl_link_stats64 *vlan_dev_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
 {
-	dev_txq_stats_fold(dev, (struct net_device_stats *)stats);
+	dev_txq_stats_fold(dev, stats);
 
 	if (vlan_dev_info(dev)->vlan_rx_stats) {
 		struct vlan_rx_stats *p, accum = {0};
diff --git a/net/core/dev.c b/net/core/dev.c
index eb4201c..5ec2eec 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5274,10 +5274,10 @@ void netdev_run_todo(void)
 /**
  *	dev_txq_stats_fold - fold tx_queues stats
  *	@dev: device to get statistics from
- *	@stats: struct net_device_stats to hold results
+ *	@stats: struct rtnl_link_stats64 to hold results
  */
 void dev_txq_stats_fold(const struct net_device *dev,
-			struct net_device_stats *stats)
+			struct rtnl_link_stats64 *stats)
 {
 	unsigned long tx_bytes = 0, tx_packets = 0, tx_dropped = 0;
 	unsigned int i;
@@ -5311,17 +5311,26 @@ const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
 					      struct rtnl_link_stats64 *storage)
 {
 	const struct net_device_ops *ops = dev->netdev_ops;
+	size_t i, n = sizeof(*storage) / sizeof(u64);
+	u64 *stats64 = (u64 *)storage;
+	const unsigned long *stats;
 
 	if (ops->ndo_get_stats64) {
 		memset(storage, 0, sizeof(*storage));
 		return ops->ndo_get_stats64(dev, storage);
 	}
+
 	if (ops->ndo_get_stats) {
-		memcpy(storage, ops->ndo_get_stats(dev), sizeof(*storage));
+		stats = (const unsigned long *)ops->ndo_get_stats(dev);
+		for (i = 0; i < n; i++)
+			stats64[i] = stats[i];
 		return storage;
 	}
-	memcpy(storage, &dev->stats, sizeof(*storage));
-	dev_txq_stats_fold(dev, (struct net_device_stats *)storage);
+
+	stats = (const unsigned long *)&dev->stats;
+	for (i = 0; i < n; i++)
+		stats64[i] = stats[i];
+	dev_txq_stats_fold(dev, storage);
 	return storage;
 }
 EXPORT_SYMBOL(dev_get_stats);
-- 
1.6.2.5


-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

[PATCH net-next-2.6 2/2] net: Document that dev_get_stats() returns the given pointer

[Ben Hutchings]

Document that dev_get_stats() returns the same stats pointer it was
given.  Remove const qualification from the returned pointer since the
caller may do what it likes with that structure.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
 include/linux/netdevice.h |    4 ++--
 net/core/dev.c            |   12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 17e95e3..c4fedf0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2130,8 +2130,8 @@ extern void		netdev_features_change(struct net_device *dev);
 /* Load a device via the kmod */
 extern void		dev_load(struct net *net, const char *name);
 extern void		dev_mcast_init(void);
-extern const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
-						     struct rtnl_link_stats64 *storage);
+extern struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
+					       struct rtnl_link_stats64 *storage);
 extern void		dev_txq_stats_fold(const struct net_device *dev,
 					   struct rtnl_link_stats64 *stats);
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 5ec2eec..2605a68 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5302,13 +5302,13 @@ EXPORT_SYMBOL(dev_txq_stats_fold);
  *	@dev: device to get statistics from
  *	@storage: place to store stats
  *
- *	Get network statistics from device. The device driver may provide
- *	its own method by setting dev->netdev_ops->get_stats64 or
- *	dev->netdev_ops->get_stats; otherwise the internal statistics
- *	structure is used.
+ *	Get network statistics from device. Return @storage.
+ *	The device driver may provide its own method by setting
+ *	dev->netdev_ops->get_stats64 or dev->netdev_ops->get_stats;
+ *	otherwise the internal statistics structure is used.
  */
-const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
-					      struct rtnl_link_stats64 *storage)
+struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
+					struct rtnl_link_stats64 *storage)
 {
 	const struct net_device_ops *ops = dev->netdev_ops;
 	size_t i, n = sizeof(*storage) / sizeof(u64);
-- 
1.6.2.5

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: [PATCH net-next-2.6 1/2] net: Get rid of rtnl_link_stats64 / net_device_stats union

[Eric Dumazet]

Le vendredi 09 juillet 2010 à 00:29 +0100, Ben Hutchings a écrit :
> In commit be1f3c2c027cc5ad735df6a45a542ed1db7ec48b "net: Enable 64-bit
> net device statistics on 32-bit architectures" I redefined struct
> net_device_stats so that it could be used in a union with struct
> rtnl_link_stats64, avoiding the need for explicit copying or
> conversion between the two.  However, this is unsafe because there is
> no locking required and no lock consistently held around calls to
> dev_get_stats() and use of the statistics structure it returns.
> 
> In commit 28172739f0a276eb8d6ca917b3974c2edb036da3 "net: fix 64 bit
> counters on 32 bit arches" Eric Dumazet dealt with that problem by
> requiring callers of dev_get_stats() to provide storage for the
> result.  This means that the net_device::stats64 field and the padding
> in struct net_device_stats are now redundant, so remove them.
> 
> Update the comment on net_device_ops::ndo_get_stats64 to reflect its
> new usage.
> 
> Change dev_txq_stats_fold() to use struct rtnl_link_stats64, since
> that is what all its callers are really using and it is no longer
> going to be compatible with struct net_device_stats.
> 
> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
> ---
>  drivers/net/macvlan.c     |    2 +-
>  include/linux/netdevice.h |   70 ++++++++++++++++++---------------------------
>  net/8021q/vlan_dev.c      |    2 +-
>  net/core/dev.c            |   19 +++++++++---
>  4 files changed, 44 insertions(+), 49 deletions(-)
> 
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index 6112f14..1b28aae 100644
> --- a/drivers/net/macvlan.c
> +++ b/drivers/net/macvlan.c
> @@ -436,7 +436,7 @@ static struct rtnl_link_stats64 *macvlan_dev_get_stats64(struct net_device *dev,
>  {
>  	struct macvlan_dev *vlan = netdev_priv(dev);
>  
> -	dev_txq_stats_fold(dev, (struct net_device_stats *)stats);
> +	dev_txq_stats_fold(dev, stats);
>  
>  	if (vlan->rx_stats) {
>  		struct macvlan_rx_stats *p, accum = {0};
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 8018f6b..17e95e3 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -162,42 +162,32 @@ static inline bool dev_xmit_complete(int rc)
>  /*
>   *	Old network device statistics. Fields are native words
>   *	(unsigned long) so they can be read and written atomically.
> - *	Each field is padded to 64 bits for compatibility with
> - *	rtnl_link_stats64.
>   */
>  
> -#if BITS_PER_LONG == 64
> -#define NET_DEVICE_STATS_DEFINE(name)	unsigned long name
> -#elif defined(__LITTLE_ENDIAN)
> -#define NET_DEVICE_STATS_DEFINE(name)	unsigned long name, pad_ ## name
> -#else
> -#define NET_DEVICE_STATS_DEFINE(name)	unsigned long pad_ ## name, name
> -#endif
> -
>  struct net_device_stats {
> -	NET_DEVICE_STATS_DEFINE(rx_packets);
> -	NET_DEVICE_STATS_DEFINE(tx_packets);
> -	NET_DEVICE_STATS_DEFINE(rx_bytes);
> -	NET_DEVICE_STATS_DEFINE(tx_bytes);
> -	NET_DEVICE_STATS_DEFINE(rx_errors);
> -	NET_DEVICE_STATS_DEFINE(tx_errors);
> -	NET_DEVICE_STATS_DEFINE(rx_dropped);
> -	NET_DEVICE_STATS_DEFINE(tx_dropped);
> -	NET_DEVICE_STATS_DEFINE(multicast);
> -	NET_DEVICE_STATS_DEFINE(collisions);
> -	NET_DEVICE_STATS_DEFINE(rx_length_errors);
> -	NET_DEVICE_STATS_DEFINE(rx_over_errors);
> -	NET_DEVICE_STATS_DEFINE(rx_crc_errors);
> -	NET_DEVICE_STATS_DEFINE(rx_frame_errors);
> -	NET_DEVICE_STATS_DEFINE(rx_fifo_errors);
> -	NET_DEVICE_STATS_DEFINE(rx_missed_errors);
> -	NET_DEVICE_STATS_DEFINE(tx_aborted_errors);
> -	NET_DEVICE_STATS_DEFINE(tx_carrier_errors);
> -	NET_DEVICE_STATS_DEFINE(tx_fifo_errors);
> -	NET_DEVICE_STATS_DEFINE(tx_heartbeat_errors);
> -	NET_DEVICE_STATS_DEFINE(tx_window_errors);
> -	NET_DEVICE_STATS_DEFINE(rx_compressed);
> -	NET_DEVICE_STATS_DEFINE(tx_compressed);
> +	unsigned long	rx_packets;
> +	unsigned long	tx_packets;
> +	unsigned long	rx_bytes;
> +	unsigned long	tx_bytes;
> +	unsigned long	rx_errors;
> +	unsigned long	tx_errors;
> +	unsigned long	rx_dropped;
> +	unsigned long	tx_dropped;
> +	unsigned long	multicast;
> +	unsigned long	collisions;
> +	unsigned long	rx_length_errors;
> +	unsigned long	rx_over_errors;
> +	unsigned long	rx_crc_errors;
> +	unsigned long	rx_frame_errors;
> +	unsigned long	rx_fifo_errors;
> +	unsigned long	rx_missed_errors;
> +	unsigned long	tx_aborted_errors;
> +	unsigned long	tx_carrier_errors;
> +	unsigned long	tx_fifo_errors;
> +	unsigned long	tx_heartbeat_errors;
> +	unsigned long	tx_window_errors;
> +	unsigned long	rx_compressed;
> +	unsigned long	tx_compressed;
>  };
>  
>  #endif  /*  __KERNEL__  */
> @@ -666,14 +656,13 @@ struct netdev_rx_queue {
>   *	Callback uses when the transmitter has not made any progress
>   *	for dev->watchdog ticks.
>   *
> - * struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev
> + * struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev,
>   *                      struct rtnl_link_stats64 *storage);
>   * struct net_device_stats* (*ndo_get_stats)(struct net_device *dev);
>   *	Called when a user wants to get the network device usage
>   *	statistics. Drivers must do one of the following:
> - *	1. Define @ndo_get_stats64 to update a rtnl_link_stats64 structure
> - *	   (which should normally be dev->stats64) and return a ponter to
> - *	   it. The structure must not be changed asynchronously.
> + *	1. Define @ndo_get_stats64 to fill in a zero-initialised
> + *	   rtnl_link_stats64 structure passed by the caller.
>   *	2. Define @ndo_get_stats to update a net_device_stats structure
>   *	   (which should normally be dev->stats) and return a pointer to
>   *	   it. The structure may be changed asynchronously only if each
> @@ -888,10 +877,7 @@ struct net_device {
>  	int			ifindex;
>  	int			iflink;
>  
> -	union {
> -		struct rtnl_link_stats64 stats64;
> -		struct net_device_stats stats;
> -	};
> +	struct net_device_stats	stats;
>  
>  #ifdef CONFIG_WIRELESS_EXT
>  	/* List of functions to handle Wireless Extensions (instead of ioctl).
> @@ -2147,7 +2133,7 @@ extern void		dev_mcast_init(void);
>  extern const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
>  						     struct rtnl_link_stats64 *storage);
>  extern void		dev_txq_stats_fold(const struct net_device *dev,
> -					   struct net_device_stats *stats);
> +					   struct rtnl_link_stats64 *stats);
>  
>  extern int		netdev_max_backlog;
>  extern int		netdev_tstamp_prequeue;
> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
> index 7865a4c..e66c9bf 100644
> --- a/net/8021q/vlan_dev.c
> +++ b/net/8021q/vlan_dev.c
> @@ -805,7 +805,7 @@ static u32 vlan_ethtool_get_flags(struct net_device *dev)
>  
>  static struct rtnl_link_stats64 *vlan_dev_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
>  {
> -	dev_txq_stats_fold(dev, (struct net_device_stats *)stats);
> +	dev_txq_stats_fold(dev, stats);
>  
>  	if (vlan_dev_info(dev)->vlan_rx_stats) {
>  		struct vlan_rx_stats *p, accum = {0};
> diff --git a/net/core/dev.c b/net/core/dev.c
> index eb4201c..5ec2eec 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -5274,10 +5274,10 @@ void netdev_run_todo(void)
>  /**
>   *	dev_txq_stats_fold - fold tx_queues stats
>   *	@dev: device to get statistics from
> - *	@stats: struct net_device_stats to hold results
> + *	@stats: struct rtnl_link_stats64 to hold results
>   */
>  void dev_txq_stats_fold(const struct net_device *dev,
> -			struct net_device_stats *stats)
> +			struct rtnl_link_stats64 *stats)
>  {
>  	unsigned long tx_bytes = 0, tx_packets = 0, tx_dropped = 0;
>  	unsigned int i;
> @@ -5311,17 +5311,26 @@ const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
>  					      struct rtnl_link_stats64 *storage)
>  {
>  	const struct net_device_ops *ops = dev->netdev_ops;
> +	size_t i, n = sizeof(*storage) / sizeof(u64);
> +	u64 *stats64 = (u64 *)storage;
> +	const unsigned long *stats;
>  
>  	if (ops->ndo_get_stats64) {
>  		memset(storage, 0, sizeof(*storage));
>  		return ops->ndo_get_stats64(dev, storage);
>  	}
> +
>  	if (ops->ndo_get_stats) {
> -		memcpy(storage, ops->ndo_get_stats(dev), sizeof(*storage));
> +		stats = (const unsigned long *)ops->ndo_get_stats(dev);
> +		for (i = 0; i < n; i++)
> +			stats64[i] = stats[i];

This could be a small helper function, to hide the sizeof(*storage) /
sizeof(u64) magic..

static void stats_to_stats64(struct rtnl_link_stats64 *dst,
			     const net_device_stats *src)
{
#if BITS_PER_LONG == 64
	BUILD_BUG_ON(sizeof(*dst) != sizeof(*src));
	memcpy(dst, src, sizeof(*src));
#else
	size_t i, n = sizeof(*dst) / sizeof(u64);
	u64 *stats64 = (u64 *)dst;
	const unsigned long *stats = (const unsigned long *)src;

	BUILD_BUG_ON(sizeof(*src) != n * sizeof(unsigned long));
	for (i = 0; i < n, i++)
		stats64[i] = stats[i];
#endif
 }
 

Thanks !

Re: [PATCH net-next-2.6 1/2] net: Get rid of rtnl_link_stats64 / net_device_stats union

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Fri, 09 Jul 2010 06:25:43 +0200

> This could be a small helper function, to hide the sizeof(*storage) /
> sizeof(u64) magic..
> 
> static void stats_to_stats64(struct rtnl_link_stats64 *dst,
> 			     const net_device_stats *src)
> {

Ben, please add Eric' suggestion and respin your second patch as
well.

Thanks!

Re: [PATCH net-next-2.6 1/2] net: Get rid of rtnl_link_stats64 / net_device_stats union

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Fri, 09 Jul 2010 23:08:54 +0200

> Le vendredi 09 juillet 2010 à 20:11 +0100, Ben Hutchings a écrit :
>> In commit be1f3c2c027cc5ad735df6a45a542ed1db7ec48b "net: Enable 64-bit
>> net device statistics on 32-bit architectures" I redefined struct
>> net_device_stats so that it could be used in a union with struct
>> rtnl_link_stats64, avoiding the need for explicit copying or
>> conversion between the two.  However, this is unsafe because there is
>> no locking required and no lock consistently held around calls to
>> dev_get_stats() and use of the statistics structure it returns.
>> 
>> In commit 28172739f0a276eb8d6ca917b3974c2edb036da3 "net: fix 64 bit
>> counters on 32 bit arches" Eric Dumazet dealt with that problem by
>> requiring callers of dev_get_stats() to provide storage for the
>> result.  This means that the net_device::stats64 field and the padding
>> in struct net_device_stats are now redundant, so remove them.
>> 
>> Update the comment on net_device_ops::ndo_get_stats64 to reflect its
>> new usage.
>> 
>> Change dev_txq_stats_fold() to use struct rtnl_link_stats64, since
>> that is what all its callers are really using and it is no longer
>> going to be compatible with struct net_device_stats.
>> 
>> Eric Dumazet suggested the separate function for the structure
>> conversion.
>> 
>> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
> 
> Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

Applied.

Re: [PATCH net-next-2.6 1/2] net: Get rid of rtnl_link_stats64 / net_device_stats union

[Eric Dumazet]

Le vendredi 09 juillet 2010 à 20:11 +0100, Ben Hutchings a écrit :
> In commit be1f3c2c027cc5ad735df6a45a542ed1db7ec48b "net: Enable 64-bit
> net device statistics on 32-bit architectures" I redefined struct
> net_device_stats so that it could be used in a union with struct
> rtnl_link_stats64, avoiding the need for explicit copying or
> conversion between the two.  However, this is unsafe because there is
> no locking required and no lock consistently held around calls to
> dev_get_stats() and use of the statistics structure it returns.
> 
> In commit 28172739f0a276eb8d6ca917b3974c2edb036da3 "net: fix 64 bit
> counters on 32 bit arches" Eric Dumazet dealt with that problem by
> requiring callers of dev_get_stats() to provide storage for the
> result.  This means that the net_device::stats64 field and the padding
> in struct net_device_stats are now redundant, so remove them.
> 
> Update the comment on net_device_ops::ndo_get_stats64 to reflect its
> new usage.
> 
> Change dev_txq_stats_fold() to use struct rtnl_link_stats64, since
> that is what all its callers are really using and it is no longer
> going to be compatible with struct net_device_stats.
> 
> Eric Dumazet suggested the separate function for the structure
> conversion.
> 
> Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

Thanks !

[PATCH net-next-2.6 1/2] net: Get rid of rtnl_link_stats64 / net_device_stats union

[Ben Hutchings]

In commit be1f3c2c027cc5ad735df6a45a542ed1db7ec48b "net: Enable 64-bit
net device statistics on 32-bit architectures" I redefined struct
net_device_stats so that it could be used in a union with struct
rtnl_link_stats64, avoiding the need for explicit copying or
conversion between the two.  However, this is unsafe because there is
no locking required and no lock consistently held around calls to
dev_get_stats() and use of the statistics structure it returns.

In commit 28172739f0a276eb8d6ca917b3974c2edb036da3 "net: fix 64 bit
counters on 32 bit arches" Eric Dumazet dealt with that problem by
requiring callers of dev_get_stats() to provide storage for the
result.  This means that the net_device::stats64 field and the padding
in struct net_device_stats are now redundant, so remove them.

Update the comment on net_device_ops::ndo_get_stats64 to reflect its
new usage.

Change dev_txq_stats_fold() to use struct rtnl_link_stats64, since
that is what all its callers are really using and it is no longer
going to be compatible with struct net_device_stats.

Eric Dumazet suggested the separate function for the structure
conversion.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
 drivers/net/macvlan.c     |    2 +-
 include/linux/netdevice.h |   70 ++++++++++++++++++---------------------------
 net/8021q/vlan_dev.c      |    2 +-
 net/core/dev.c            |   31 ++++++++++++++++---
 4 files changed, 56 insertions(+), 49 deletions(-)

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 6112f14..1b28aae 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -436,7 +436,7 @@ static struct rtnl_link_stats64 *macvlan_dev_get_stats64(struct net_device *dev,
 {
 	struct macvlan_dev *vlan = netdev_priv(dev);
 
-	dev_txq_stats_fold(dev, (struct net_device_stats *)stats);
+	dev_txq_stats_fold(dev, stats);
 
 	if (vlan->rx_stats) {
 		struct macvlan_rx_stats *p, accum = {0};
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8018f6b..17e95e3 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -162,42 +162,32 @@ static inline bool dev_xmit_complete(int rc)
 /*
  *	Old network device statistics. Fields are native words
  *	(unsigned long) so they can be read and written atomically.
- *	Each field is padded to 64 bits for compatibility with
- *	rtnl_link_stats64.
  */
 
-#if BITS_PER_LONG == 64
-#define NET_DEVICE_STATS_DEFINE(name)	unsigned long name
-#elif defined(__LITTLE_ENDIAN)
-#define NET_DEVICE_STATS_DEFINE(name)	unsigned long name, pad_ ## name
-#else
-#define NET_DEVICE_STATS_DEFINE(name)	unsigned long pad_ ## name, name
-#endif
-
 struct net_device_stats {
-	NET_DEVICE_STATS_DEFINE(rx_packets);
-	NET_DEVICE_STATS_DEFINE(tx_packets);
-	NET_DEVICE_STATS_DEFINE(rx_bytes);
-	NET_DEVICE_STATS_DEFINE(tx_bytes);
-	NET_DEVICE_STATS_DEFINE(rx_errors);
-	NET_DEVICE_STATS_DEFINE(tx_errors);
-	NET_DEVICE_STATS_DEFINE(rx_dropped);
-	NET_DEVICE_STATS_DEFINE(tx_dropped);
-	NET_DEVICE_STATS_DEFINE(multicast);
-	NET_DEVICE_STATS_DEFINE(collisions);
-	NET_DEVICE_STATS_DEFINE(rx_length_errors);
-	NET_DEVICE_STATS_DEFINE(rx_over_errors);
-	NET_DEVICE_STATS_DEFINE(rx_crc_errors);
-	NET_DEVICE_STATS_DEFINE(rx_frame_errors);
-	NET_DEVICE_STATS_DEFINE(rx_fifo_errors);
-	NET_DEVICE_STATS_DEFINE(rx_missed_errors);
-	NET_DEVICE_STATS_DEFINE(tx_aborted_errors);
-	NET_DEVICE_STATS_DEFINE(tx_carrier_errors);
-	NET_DEVICE_STATS_DEFINE(tx_fifo_errors);
-	NET_DEVICE_STATS_DEFINE(tx_heartbeat_errors);
-	NET_DEVICE_STATS_DEFINE(tx_window_errors);
-	NET_DEVICE_STATS_DEFINE(rx_compressed);
-	NET_DEVICE_STATS_DEFINE(tx_compressed);
+	unsigned long	rx_packets;
+	unsigned long	tx_packets;
+	unsigned long	rx_bytes;
+	unsigned long	tx_bytes;
+	unsigned long	rx_errors;
+	unsigned long	tx_errors;
+	unsigned long	rx_dropped;
+	unsigned long	tx_dropped;
+	unsigned long	multicast;
+	unsigned long	collisions;
+	unsigned long	rx_length_errors;
+	unsigned long	rx_over_errors;
+	unsigned long	rx_crc_errors;
+	unsigned long	rx_frame_errors;
+	unsigned long	rx_fifo_errors;
+	unsigned long	rx_missed_errors;
+	unsigned long	tx_aborted_errors;
+	unsigned long	tx_carrier_errors;
+	unsigned long	tx_fifo_errors;
+	unsigned long	tx_heartbeat_errors;
+	unsigned long	tx_window_errors;
+	unsigned long	rx_compressed;
+	unsigned long	tx_compressed;
 };
 
 #endif  /*  __KERNEL__  */
@@ -666,14 +656,13 @@ struct netdev_rx_queue {
  *	Callback uses when the transmitter has not made any progress
  *	for dev->watchdog ticks.
  *
- * struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev
+ * struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev,
  *                      struct rtnl_link_stats64 *storage);
  * struct net_device_stats* (*ndo_get_stats)(struct net_device *dev);
  *	Called when a user wants to get the network device usage
  *	statistics. Drivers must do one of the following:
- *	1. Define @ndo_get_stats64 to update a rtnl_link_stats64 structure
- *	   (which should normally be dev->stats64) and return a ponter to
- *	   it. The structure must not be changed asynchronously.
+ *	1. Define @ndo_get_stats64 to fill in a zero-initialised
+ *	   rtnl_link_stats64 structure passed by the caller.
  *	2. Define @ndo_get_stats to update a net_device_stats structure
  *	   (which should normally be dev->stats) and return a pointer to
  *	   it. The structure may be changed asynchronously only if each
@@ -888,10 +877,7 @@ struct net_device {
 	int			ifindex;
 	int			iflink;
 
-	union {
-		struct rtnl_link_stats64 stats64;
-		struct net_device_stats stats;
-	};
+	struct net_device_stats	stats;
 
 #ifdef CONFIG_WIRELESS_EXT
 	/* List of functions to handle Wireless Extensions (instead of ioctl).
@@ -2147,7 +2133,7 @@ extern void		dev_mcast_init(void);
 extern const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
 						     struct rtnl_link_stats64 *storage);
 extern void		dev_txq_stats_fold(const struct net_device *dev,
-					   struct net_device_stats *stats);
+					   struct rtnl_link_stats64 *stats);
 
 extern int		netdev_max_backlog;
 extern int		netdev_tstamp_prequeue;
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index a1b8171..7cb285f 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -805,7 +805,7 @@ static u32 vlan_ethtool_get_flags(struct net_device *dev)
 
 static struct rtnl_link_stats64 *vlan_dev_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
 {
-	dev_txq_stats_fold(dev, (struct net_device_stats *)stats);
+	dev_txq_stats_fold(dev, stats);
 
 	if (vlan_dev_info(dev)->vlan_rx_stats) {
 		struct vlan_rx_stats *p, accum = {0};
diff --git a/net/core/dev.c b/net/core/dev.c
index eb4201c..79ee26e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5274,10 +5274,10 @@ void netdev_run_todo(void)
 /**
  *	dev_txq_stats_fold - fold tx_queues stats
  *	@dev: device to get statistics from
- *	@stats: struct net_device_stats to hold results
+ *	@stats: struct rtnl_link_stats64 to hold results
  */
 void dev_txq_stats_fold(const struct net_device *dev,
-			struct net_device_stats *stats)
+			struct rtnl_link_stats64 *stats)
 {
 	unsigned long tx_bytes = 0, tx_packets = 0, tx_dropped = 0;
 	unsigned int i;
@@ -5297,6 +5297,27 @@ void dev_txq_stats_fold(const struct net_device *dev,
 }
 EXPORT_SYMBOL(dev_txq_stats_fold);
 
+/* Convert net_device_stats to rtnl_link_stats64.  They have the same
+ * fields in the same order, with only the type differing.
+ */
+static void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64,
+				    const struct net_device_stats *netdev_stats)
+{
+#if BITS_PER_LONG == 64
+        BUILD_BUG_ON(sizeof(*stats64) != sizeof(*netdev_stats));
+        memcpy(stats64, netdev_stats, sizeof(*stats64));
+#else
+	size_t i, n = sizeof(*stats64) / sizeof(u64);
+	const unsigned long *src = (const unsigned long *)netdev_stats;
+	u64 *dst = (u64 *)stats64;
+
+	BUILD_BUG_ON(sizeof(*netdev_stats) / sizeof(unsigned long) !=
+		     sizeof(*stats64) / sizeof(u64));
+	for (i = 0; i < n; i++)
+		dst[i] = src[i];
+#endif
+}
+
 /**
  *	dev_get_stats	- get network device statistics
  *	@dev: device to get statistics from
@@ -5317,11 +5338,11 @@ const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
 		return ops->ndo_get_stats64(dev, storage);
 	}
 	if (ops->ndo_get_stats) {
-		memcpy(storage, ops->ndo_get_stats(dev), sizeof(*storage));
+		netdev_stats_to_stats64(storage, ops->ndo_get_stats(dev));
 		return storage;
 	}
-	memcpy(storage, &dev->stats, sizeof(*storage));
-	dev_txq_stats_fold(dev, (struct net_device_stats *)storage);
+	netdev_stats_to_stats64(storage, &dev->stats);
+	dev_txq_stats_fold(dev, storage);
 	return storage;
 }
 EXPORT_SYMBOL(dev_get_stats);
-- 
1.6.2.5


-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.