Patchwork [PATCHv2,1/2] net: Enable 64-bit net device statistics on 32-bit architectures

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Submitter Ben Hutchings
Date June 4, 2010, 10:04 p.m.
Message ID <1275689093.2095.36.camel@achroite.uk.solarflarecom.com>
Download mbox | patch
Permalink /patch/54725/
State Changes Requested
Delegated to: David Miller
Headers show

Comments

Ben Hutchings - June 4, 2010, 10:04 p.m.
Use struct rtnl_link_stats64 as the statistics structure.

On 32-bit architectures, insert 32 bits of padding after/before each
field of struct net_device_stats to make its layout compatible with
struct rtnl_link_stats64.  Add an anonymous union in net_device; move
stats into the union and add struct rtnl_link_stats64 stats64.

Add net_device_ops::ndo_get_stats64, implementations of which will
return a pointer to struct rtnl_link_stats64.  Drivers that implement
this operation must not update the structure asynchronously.

Change dev_get_stats() to call ndo_get_stats64 if available, and to
return a pointer to struct rtnl_link_stats64.  Change callers of
dev_get_stats() accordingly.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
---
This time without the horrible accessor macros.

Ben.

 include/linux/if_link.h   |    3 +-
 include/linux/netdevice.h |   91 ++++++++++++++++++++++++++------------------
 net/8021q/vlanproc.c      |   13 +++---
 net/core/dev.c            |   19 +++++----
 net/core/net-sysfs.c      |   12 +++---
 net/core/rtnetlink.c      |    6 +-
 6 files changed, 83 insertions(+), 61 deletions(-)
David Miller - June 8, 2010, 4:18 a.m.
From: Ben Hutchings <bhutchings@solarflare.com>
Date: Fri, 04 Jun 2010 23:04:53 +0100

> +#if BITS_PER_LONG == 64
> +#define NET_DEVICE_STATS_DEFINE(name)	u64 name
> +#elif defined(__LITTLE_ENDIAN)
> +#define NET_DEVICE_STATS_DEFINE(name)	u32 name, pad_ ## name
> +#else
> +#define NET_DEVICE_STATS_DEFINE(name)	u32 pad_ ## name, name
> +#endif
> +
 ...
> +	NET_DEVICE_STATS_DEFINE(rx_packets);
> +	NET_DEVICE_STATS_DEFINE(tx_packets);
> +	NET_DEVICE_STATS_DEFINE(rx_bytes);
 ...
>  	static const char fmt[] = "%30s %12lu\n";
> +	static const char fmt64[] = "%30s %12llu\n";
 ...
> +	seq_printf(seq, fmt64, "total frames received", stats->rx_packets);
> +	seq_printf(seq, fmt64, "total bytes received", stats->rx_bytes);
> +	seq_printf(seq, fmt64, "Broadcast/Multicast Rcvd", stats->multicast);

I guess you only built this on a 64-bit platform that defines u64 as a
long long type.

The rest of the world will receive tons of warnings for these print
statements.

You have basically 3 cases to handle:

1) u64 defined as "unsigned long long"

2) u64 defined as "unsigned long"

3) u32 defined as "unsigned int"

And the whole tree needs to be inspected to make sure there isn't going
to be fallout in areas your patch didn't take care of wrt. printf format
strings and the like.

What was always "unsigned long" is now a variable type, therefore using
a fixed printf format string is impossible unless you always cast these
things when passed in as printf arguments.

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Ben Hutchings - June 8, 2010, 11:35 a.m.
On Mon, 2010-06-07 at 21:18 -0700, David Miller wrote:
> From: Ben Hutchings <bhutchings@solarflare.com>
> Date: Fri, 04 Jun 2010 23:04:53 +0100
> 
> > +#if BITS_PER_LONG == 64
> > +#define NET_DEVICE_STATS_DEFINE(name)	u64 name
> > +#elif defined(__LITTLE_ENDIAN)
> > +#define NET_DEVICE_STATS_DEFINE(name)	u32 name, pad_ ## name
> > +#else
> > +#define NET_DEVICE_STATS_DEFINE(name)	u32 pad_ ## name, name
> > +#endif
> > +
>  ...
> > +	NET_DEVICE_STATS_DEFINE(rx_packets);
> > +	NET_DEVICE_STATS_DEFINE(tx_packets);
> > +	NET_DEVICE_STATS_DEFINE(rx_bytes);
>  ...
> >  	static const char fmt[] = "%30s %12lu\n";
> > +	static const char fmt64[] = "%30s %12llu\n";
>  ...
> > +	seq_printf(seq, fmt64, "total frames received", stats->rx_packets);
> > +	seq_printf(seq, fmt64, "total bytes received", stats->rx_bytes);
> > +	seq_printf(seq, fmt64, "Broadcast/Multicast Rcvd", stats->multicast);
> 
> I guess you only built this on a 64-bit platform that defines u64 as a
> long long type.

There was some disussion of formatting u64 / unsigned long long in the
past and I thought the outcome of that was that u64 should always be
defined as unsigned long long.  (See commits fe33332 and 9018113.)

[...]
> And the whole tree needs to be inspected to make sure there isn't going
> to be fallout in areas your patch didn't take care of wrt. printf format
> strings and the like.
> 
> What was always "unsigned long" is now a variable type, therefore using
> a fixed printf format string is impossible unless you always cast these
> things when passed in as printf arguments.

Yes, that's true if there are drivers out there printing members of
net_device_stats.  I admit I haven't checked for that.  (Hmm, might be
time to try Coccinelle.)

Ben.
Ben Hutchings - June 8, 2010, 3:56 p.m.
On Tue, 2010-06-08 at 12:35 +0100, Ben Hutchings wrote:
[...]
> > And the whole tree needs to be inspected to make sure there isn't going
> > to be fallout in areas your patch didn't take care of wrt. printf format
> > strings and the like.
> > 
> > What was always "unsigned long" is now a variable type, therefore using
> > a fixed printf format string is impossible unless you always cast these
> > things when passed in as printf arguments.
> 
> Yes, that's true if there are drivers out there printing members of
> net_device_stats.  I admit I haven't checked for that.  (Hmm, might be
> time to try Coccinelle.)

There are a few of those, so I'll keep the declared type as unsigned
long rather than making the sizes explicit.

Ben.

Patch

diff --git a/include/linux/if_link.h b/include/linux/if_link.h
index 85c812d..7fcad2e 100644
--- a/include/linux/if_link.h
+++ b/include/linux/if_link.h
@@ -4,7 +4,7 @@ 
 #include <linux/types.h>
 #include <linux/netlink.h>
 
-/* The struct should be in sync with struct net_device_stats */
+/* This struct should be in sync with struct rtnl_link_stats64 */
 struct rtnl_link_stats {
 	__u32	rx_packets;		/* total packets received	*/
 	__u32	tx_packets;		/* total packets transmitted	*/
@@ -37,6 +37,7 @@  struct rtnl_link_stats {
 	__u32	tx_compressed;
 };
 
+/* The main device statistics structure */
 struct rtnl_link_stats64 {
 	__u64	rx_packets;		/* total packets received	*/
 	__u64	tx_packets;		/* total packets transmitted	*/
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a249161..dceacc2 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -159,45 +159,49 @@  static inline bool dev_xmit_complete(int rc)
 #define MAX_HEADER (LL_MAX_HEADER + 48)
 #endif
 
-#endif  /*  __KERNEL__  */
-
 /*
- *	Network device statistics. Akin to the 2.0 ether stats but
- *	with byte counters.
+ *	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)	u64 name
+#elif defined(__LITTLE_ENDIAN)
+#define NET_DEVICE_STATS_DEFINE(name)	u32 name, pad_ ## name
+#else
+#define NET_DEVICE_STATS_DEFINE(name)	u32 pad_ ## name, name
+#endif
+
 struct net_device_stats {
-	unsigned long	rx_packets;		/* total packets received	*/
-	unsigned long	tx_packets;		/* total packets transmitted	*/
-	unsigned long	rx_bytes;		/* total bytes received 	*/
-	unsigned long	tx_bytes;		/* total bytes transmitted	*/
-	unsigned long	rx_errors;		/* bad packets received		*/
-	unsigned long	tx_errors;		/* packet transmit problems	*/
-	unsigned long	rx_dropped;		/* no space in linux buffers	*/
-	unsigned long	tx_dropped;		/* no space available in linux	*/
-	unsigned long	multicast;		/* multicast packets received	*/
-	unsigned long	collisions;
-
-	/* detailed rx_errors: */
-	unsigned long	rx_length_errors;
-	unsigned long	rx_over_errors;		/* receiver ring buff overflow	*/
-	unsigned long	rx_crc_errors;		/* recved pkt with crc error	*/
-	unsigned long	rx_frame_errors;	/* recv'd frame alignment error */
-	unsigned long	rx_fifo_errors;		/* recv'r fifo overrun		*/
-	unsigned long	rx_missed_errors;	/* receiver missed packet	*/
-
-	/* detailed tx_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;
-	
-	/* for cslip etc */
-	unsigned long	rx_compressed;
-	unsigned long	tx_compressed;
+	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);
 };
 
+#endif  /*  __KERNEL__  */
+
 
 /* Media selection options. */
 enum {
@@ -660,10 +664,19 @@  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 net_device_stats* (*ndo_get_stats)(struct net_device *dev);
  *	Called when a user wants to get the network device usage
- *	statistics. If not defined, the counters in dev->stats will
- *	be used.
+ *	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.
+ *	2. Define @ndo_get_stats to update a net_device_stats64 structure
+ *	   (which should normally be dev->stats) and return a pointer to
+ *	   it. The structure may be changed asynchronously only if each
+ *	   field is written atomically.
+ *	3. Update dev->stats asynchronously and atomically, and define
+ *	   neither operation.
  *
  * void (*ndo_vlan_rx_register)(struct net_device *dev, struct vlan_group *grp);
  *	If device support VLAN receive accleration
@@ -718,6 +731,7 @@  struct net_device_ops {
 						   struct neigh_parms *);
 	void			(*ndo_tx_timeout) (struct net_device *dev);
 
+	struct rtnl_link_stats64* (*ndo_get_stats64)(struct net_device *dev);
 	struct net_device_stats* (*ndo_get_stats)(struct net_device *dev);
 
 	void			(*ndo_vlan_rx_register)(struct net_device *dev,
@@ -867,7 +881,10 @@  struct net_device {
 	int			ifindex;
 	int			iflink;
 
-	struct net_device_stats	stats;
+	union {
+		struct rtnl_link_stats64 stats64;
+		struct net_device_stats stats;
+	};
 
 #ifdef CONFIG_WIRELESS_EXT
 	/* List of functions to handle Wireless Extensions (instead of ioctl).
@@ -2118,7 +2135,7 @@  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 net_device_stats *dev_get_stats(struct net_device *dev);
+extern const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev);
 extern void		dev_txq_stats_fold(const struct net_device *dev, struct net_device_stats *stats);
 
 extern int		netdev_max_backlog;
diff --git a/net/8021q/vlanproc.c b/net/8021q/vlanproc.c
index afead35..df56f5c 100644
--- a/net/8021q/vlanproc.c
+++ b/net/8021q/vlanproc.c
@@ -278,8 +278,9 @@  static int vlandev_seq_show(struct seq_file *seq, void *offset)
 {
 	struct net_device *vlandev = (struct net_device *) seq->private;
 	const struct vlan_dev_info *dev_info = vlan_dev_info(vlandev);
-	const struct net_device_stats *stats;
+	const struct rtnl_link_stats64 *stats;
 	static const char fmt[] = "%30s %12lu\n";
+	static const char fmt64[] = "%30s %12llu\n";
 	int i;
 
 	if (!is_vlan_dev(vlandev))
@@ -291,12 +292,12 @@  static int vlandev_seq_show(struct seq_file *seq, void *offset)
 		   vlandev->name, dev_info->vlan_id,
 		   (int)(dev_info->flags & 1), vlandev->priv_flags);
 
-	seq_printf(seq, fmt, "total frames received", stats->rx_packets);
-	seq_printf(seq, fmt, "total bytes received", stats->rx_bytes);
-	seq_printf(seq, fmt, "Broadcast/Multicast Rcvd", stats->multicast);
+	seq_printf(seq, fmt64, "total frames received", stats->rx_packets);
+	seq_printf(seq, fmt64, "total bytes received", stats->rx_bytes);
+	seq_printf(seq, fmt64, "Broadcast/Multicast Rcvd", stats->multicast);
 	seq_puts(seq, "\n");
-	seq_printf(seq, fmt, "total frames transmitted", stats->tx_packets);
-	seq_printf(seq, fmt, "total bytes transmitted", stats->tx_bytes);
+	seq_printf(seq, fmt64, "total frames transmitted", stats->tx_packets);
+	seq_printf(seq, fmt64, "total bytes transmitted", stats->tx_bytes);
 	seq_printf(seq, fmt, "total headroom inc",
 		   dev_info->cnt_inc_headroom_on_tx);
 	seq_printf(seq, fmt, "total encap on xmit",
diff --git a/net/core/dev.c b/net/core/dev.c
index 983a3c1..71a6fd8 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3686,10 +3686,10 @@  void dev_seq_stop(struct seq_file *seq, void *v)
 
 static void dev_seq_printf_stats(struct seq_file *seq, struct net_device *dev)
 {
-	const struct net_device_stats *stats = dev_get_stats(dev);
+	const struct rtnl_link_stats64 *stats = dev_get_stats(dev);
 
-	seq_printf(seq, "%6s: %7lu %7lu %4lu %4lu %4lu %5lu %10lu %9lu "
-		   "%8lu %7lu %4lu %4lu %4lu %5lu %7lu %10lu\n",
+	seq_printf(seq, "%6s: %7llu %7llu %4llu %4llu %4llu %5llu %10llu %9llu "
+		   "%8llu %7llu %4llu %4llu %4llu %5llu %7llu %10llu\n",
 		   dev->name, stats->rx_bytes, stats->rx_packets,
 		   stats->rx_errors,
 		   stats->rx_dropped + stats->rx_missed_errors,
@@ -5266,18 +5266,21 @@  EXPORT_SYMBOL(dev_txq_stats_fold);
  *	@dev: device to get statistics from
  *
  *	Get network statistics from device. The device driver may provide
- *	its own method by setting dev->netdev_ops->get_stats; otherwise
- *	the internal statistics structure is used.
+ *	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 net_device_stats *dev_get_stats(struct net_device *dev)
+const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev)
 {
 	const struct net_device_ops *ops = dev->netdev_ops;
 
+	if (ops->ndo_get_stats64)
+		return ops->ndo_get_stats64(dev);
 	if (ops->ndo_get_stats)
-		return ops->ndo_get_stats(dev);
+		return (struct rtnl_link_stats64 *)ops->ndo_get_stats(dev);
 
 	dev_txq_stats_fold(dev, &dev->stats);
-	return &dev->stats;
+	return &dev->stats64;
 }
 EXPORT_SYMBOL(dev_get_stats);
 
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 99e7052..ea3bb4c 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -29,6 +29,7 @@  static const char fmt_hex[] = "%#x\n";
 static const char fmt_long_hex[] = "%#lx\n";
 static const char fmt_dec[] = "%d\n";
 static const char fmt_ulong[] = "%lu\n";
+static const char fmt_u64[] = "%llu\n";
 
 static inline int dev_isalive(const struct net_device *dev)
 {
@@ -324,14 +325,13 @@  static ssize_t netstat_show(const struct device *d,
 	struct net_device *dev = to_net_dev(d);
 	ssize_t ret = -EINVAL;
 
-	WARN_ON(offset > sizeof(struct net_device_stats) ||
-			offset % sizeof(unsigned long) != 0);
+	WARN_ON(offset > sizeof(struct rtnl_link_stats64) ||
+			offset % sizeof(u64) != 0);
 
 	read_lock(&dev_base_lock);
 	if (dev_isalive(dev)) {
-		const struct net_device_stats *stats = dev_get_stats(dev);
-		ret = sprintf(buf, fmt_ulong,
-			      *(unsigned long *)(((u8 *) stats) + offset));
+		const struct rtnl_link_stats64 *stats = dev_get_stats(dev);
+		ret = sprintf(buf, fmt_u64, *(u64 *)(((u8 *) stats) + offset));
 	}
 	read_unlock(&dev_base_lock);
 	return ret;
@@ -343,7 +343,7 @@  static ssize_t show_##name(struct device *d,				\
 			   struct device_attribute *attr, char *buf) 	\
 {									\
 	return netstat_show(d, attr, buf,				\
-			    offsetof(struct net_device_stats, name));	\
+			    offsetof(struct rtnl_link_stats64, name));	\
 }									\
 static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 1a2af24..e645778 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -579,7 +579,7 @@  static unsigned int rtnl_dev_combine_flags(const struct net_device *dev,
 }
 
 static void copy_rtnl_link_stats(struct rtnl_link_stats *a,
-				 const struct net_device_stats *b)
+				 const struct rtnl_link_stats64 *b)
 {
 	a->rx_packets = b->rx_packets;
 	a->tx_packets = b->tx_packets;
@@ -610,7 +610,7 @@  static void copy_rtnl_link_stats(struct rtnl_link_stats *a,
 	a->tx_compressed = b->tx_compressed;
 }
 
-static void copy_rtnl_link_stats64(void *v, const struct net_device_stats *b)
+static void copy_rtnl_link_stats64(void *v, const struct rtnl_link_stats64 *b)
 {
 	struct rtnl_link_stats64 a;
 
@@ -791,7 +791,7 @@  static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 {
 	struct ifinfomsg *ifm;
 	struct nlmsghdr *nlh;
-	const struct net_device_stats *stats;
+	const struct rtnl_link_stats64 *stats;
 	struct nlattr *attr;
 
 	nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags);