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bonding: refine bond_fold_stats() wrap detection 

Some device drivers reset their stats at down/up events, possibly
fooling bonding stats, since they operate with relative deltas.

It is nearly not possible to fix drivers, since some of them compute the
tx/rx counters based on per rx/tx queue stats, and the queues can be
reconfigured (ethtool -L) between the down/up sequence.

Lets avoid accumulating 'negative' values that render bonding stats
useless.

It is better to lose small deltas, assuming the bonding stats are
fetched at a reasonable frequency.

Fixes: 5f0c5f73e5 ("bonding: make global bonding stats more reliable")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2017-03-29 10:45:44 -07:00 committed by David S. Miller
parent ed8bfd5c1c
commit 142c6594ac
1 changed files with 8 additions and 3 deletions
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11
drivers/net/bonding/bond_main.c
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@ -3332,12 +3332,17 @@ static void bond_fold_stats(struct rtnl_link_stats64 *_res,
for (i = 0; i < sizeof(*_res) / sizeof(u64); i++) {
u64 nv = new[i];
u64 ov = old[i];
s64 delta = nv - ov;
/* detects if this particular field is 32bit only */
if (((nv | ov) >> 32) == 0)
res[i] += (u32)nv - (u32)ov;
else
res[i] += nv - ov;
delta = (s64)(s32)((u32)nv - (u32)ov);
/* filter anomalies, some drivers reset their stats
* at down/up events.
*/
if (delta > 0)
res[i] += delta;
}
}