On Fri, 9 Jun 2017 16:29:47 +0200
Dominik Heidler <dheid...@suse.de> wrote:
> This fixes a counter problem on 32bit systems:
> When the rx_bytes counter reached 2 GiB, it jumpd to (2^64 Bytes - 2GiB)
> Bytes.
>
> rtnl_link_stats64 has __u64 type and atomic_long_read returns
> atomic_long_t which is signed. Due to the conversation
> we get an incorrect value on 32bit systems if the MSB of
> the atomic_long_t value is set.
>
> CC: Tom Parkin <tpar...@katalix.com>
> Fixes: 7b7c0719cd7a ("l2tp: avoid deadlock in l2tp stats update")
> Signed-off-by: Dominik Heidler <dheid...@suse.de>
> ---
> net/l2tp/l2tp_eth.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
> index 8b21af7321b9..668a75e002e9 100644
> --- a/net/l2tp/l2tp_eth.c
> +++ b/net/l2tp/l2tp_eth.c
> @@ -114,12 +114,13 @@ static void l2tp_eth_get_stats64(struct net_device *dev,
> {
> struct l2tp_eth *priv = netdev_priv(dev);
>
> - stats->tx_bytes = atomic_long_read(&priv->tx_bytes);
> - stats->tx_packets = atomic_long_read(&priv->tx_packets);
> - stats->tx_dropped = atomic_long_read(&priv->tx_dropped);
> - stats->rx_bytes = atomic_long_read(&priv->rx_bytes);
> - stats->rx_packets = atomic_long_read(&priv->rx_packets);
> - stats->rx_errors = atomic_long_read(&priv->rx_errors);
> + stats->tx_bytes = (unsigned long) atomic_long_read(&priv->tx_bytes);
> + stats->tx_packets = (unsigned long) atomic_long_read(&priv->tx_packets);
> + stats->tx_dropped = (unsigned long) atomic_long_read(&priv->tx_dropped);
> + stats->rx_bytes = (unsigned long) atomic_long_read(&priv->rx_bytes);
> + stats->rx_packets = (unsigned long) atomic_long_read(&priv->rx_packets);
> + stats->rx_errors = (unsigned long) atomic_long_read(&priv->rx_errors);
> +
> }
>
> static const struct net_device_ops l2tp_eth_netdev_ops = {
This is not the right way to fix this.
1. shouldn't be using atomic's for network counters, look at other network
devices.
2. should be using u64_stats_fetch api to handle 64 bit counters.
