net: Get rid of rtnl_link_stats64 / net_device_stats union

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 6112f14..1b28aae 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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);