| Message ID | 1497054551.736.99.camel@edumazet-glaptop3.roam.corp.google.com |
|---|---|
| State | RFC, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Eric Dumazet <eric.dumazet@gmail.com> Date: Fri, 09 Jun 2017 17:29:11 -0700 > On Fri, 2017-06-09 at 15:16 -0700, Stephen Hemminger wrote: >> On Fri, 9 Jun 2017 16:29:47 +0200 >> Dominik Heidler <dheidler@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 <tparkin@katalix.com> >> > Fixes: 7b7c0719cd7a ("l2tp: avoid deadlock in l2tp stats update") >> > Signed-off-by: Dominik Heidler <dheidler@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. > > But they do not want 64bit counters, and not per cpu counters for a > driver handling few packets per second. > > Just use native size of "unsigned long". Ahh yeah, indeed. I've applied this l2tp patch, therefore. > We use the same atomic_long_t for (struct netdev)->rx_dropped, > tx_dropped & rx_nohandler > > So I guess same fix is needed in dev_get_stats() Looks like it, I'll apply a formal submission of this.
diff --git a/net/core/dev.c b/net/core/dev.c index 54bb8d99d26afcc1a9c5a56f1e8c2d1f6e06db98..1a66a8761f9a579c9bf6b6ab5b1415770adcf76b 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -7785,9 +7785,9 @@ struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev, } else { netdev_stats_to_stats64(storage, &dev->stats); } - storage->rx_dropped += atomic_long_read(&dev->rx_dropped); - storage->tx_dropped += atomic_long_read(&dev->tx_dropped); - storage->rx_nohandler += atomic_long_read(&dev->rx_nohandler); + storage->rx_dropped += (unsigned long)atomic_long_read(&dev->rx_dropped); + storage->tx_dropped += (unsigned long)atomic_long_read(&dev->tx_dropped); + storage->rx_nohandler += (unsigned long)atomic_long_read(&dev->rx_nohandler); return storage; } EXPORT_SYMBOL(dev_get_stats);