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Message-ID: <1278649543.2435.105.camel@edumazet-laptop>
Date: Fri, 09 Jul 2010 06:25:43 +0200
From: Eric Dumazet <eric.dumazet@...il.com>
To: Ben Hutchings <bhutchings@...arflare.com>
Cc: David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
linux-net-drivers@...arflare.com
Subject: Re: [PATCH net-next-2.6 1/2] net: Get rid of rtnl_link_stats64 /
net_device_stats union
Le vendredi 09 juillet 2010 à 00:29 +0100, Ben Hutchings a écrit :
> 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.
>
> Signed-off-by: Ben Hutchings <bhutchings@...arflare.com>
> ---
> drivers/net/macvlan.c | 2 +-
> include/linux/netdevice.h | 70 ++++++++++++++++++---------------------------
> net/8021q/vlan_dev.c | 2 +-
> net/core/dev.c | 19 +++++++++---
> 4 files changed, 44 insertions(+), 49 deletions(-)
>
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index 6112f14..1b28aae 100644
> --- 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
> --- 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 7865a4c..e66c9bf 100644
> --- 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..5ec2eec 100644
> --- 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;
> @@ -5311,17 +5311,26 @@ const struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
> struct rtnl_link_stats64 *storage)
> {
> const struct net_device_ops *ops = dev->netdev_ops;
> + size_t i, n = sizeof(*storage) / sizeof(u64);
> + u64 *stats64 = (u64 *)storage;
> + const unsigned long *stats;
>
> if (ops->ndo_get_stats64) {
> memset(storage, 0, sizeof(*storage));
> return ops->ndo_get_stats64(dev, storage);
> }
> +
> if (ops->ndo_get_stats) {
> - memcpy(storage, ops->ndo_get_stats(dev), sizeof(*storage));
> + stats = (const unsigned long *)ops->ndo_get_stats(dev);
> + for (i = 0; i < n; i++)
> + stats64[i] = stats[i];
This could be a small helper function, to hide the sizeof(*storage) /
sizeof(u64) magic..
static void stats_to_stats64(struct rtnl_link_stats64 *dst,
const net_device_stats *src)
{
#if BITS_PER_LONG == 64
BUILD_BUG_ON(sizeof(*dst) != sizeof(*src));
memcpy(dst, src, sizeof(*src));
#else
size_t i, n = sizeof(*dst) / sizeof(u64);
u64 *stats64 = (u64 *)dst;
const unsigned long *stats = (const unsigned long *)src;
BUILD_BUG_ON(sizeof(*src) != n * sizeof(unsigned long));
for (i = 0; i < n, i++)
stats64[i] = stats[i];
#endif
}
Thanks !
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