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net: Get rid of rtnl_link_stats64 / net_device_stats union

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In commit be1f3c2c02 "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 28172739f0 "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>
This commit is contained in:
Ben Hutchings 2010-07-09 09:11:52 +00:00 • committed by David S. Miller
parent cc7b86c1a8
commit 3cfde79c6c
4 changed files with 56 additions and 49 deletions
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31
net/core/dev.c
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@ -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);