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/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 @@
/**
* 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 @@
}
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 @@
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);