bonding: fix bond_get_stats()

bond_get_stats() can be called from rtnetlink (with RTNL held)
or from /proc/net/dev seq handler (with RCU held)

The logic added in commit 5f0c5f73e5ef ("bonding: make global bonding
stats more reliable") kind of assumed only one cpu could run there.

If multiple threads are reading /proc/net/dev, stats can be really
messed up after a while.

A second problem is that some fields are 32bit, so we need to properly
handle the wrap around problem.

Given that RTNL is not always held, we need to use
bond_for_each_slave_rcu().

Fixes: 5f0c5f73e5ef ("bonding: make global bonding stats more reliable")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Andy Gospodarek <gospo@cumulusnetworks.com>
Cc: Jay Vosburgh <j.vosburgh@gmail.com>
Cc: Veaceslav Falico <vfalico@gmail.com>
Reviewed-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 270b39c8357f2931523872b1d708ae195092bc9c..941ec99cd3b69b6c9d3596e5b65b6aa89bc960c7 100644 (file)
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3301,6 +3301,30 @@ static int bond_close(struct net_device *bond_dev)
        return 0;
 }
 
+/* fold stats, assuming all rtnl_link_stats64 fields are u64, but
+ * that some drivers can provide 32bit values only.
+ */
+static void bond_fold_stats(struct rtnl_link_stats64 *_res,
+                           const struct rtnl_link_stats64 *_new,
+                           const struct rtnl_link_stats64 *_old)
+{
+       const u64 *new = (const u64 *)_new;
+       const u64 *old = (const u64 *)_old;
+       u64 *res = (u64 *)_res;
+       int i;
+
+       for (i = 0; i < sizeof(*_res) / sizeof(u64); i++) {
+               u64 nv = new[i];
+               u64 ov = old[i];
+
+               /* detects if this particular field is 32bit only */
+               if (((nv | ov) >> 32) == 0)
+                       res[i] += (u32)nv - (u32)ov;
+               else
+                       res[i] += nv - ov;
+       }
+}
+
 static struct rtnl_link_stats64 *bond_get_stats(struct net_device *bond_dev,
                                                struct rtnl_link_stats64 *stats)
 {
@@ -3309,44 +3333,23 @@ static struct rtnl_link_stats64 *bond_get_stats(struct net_device *bond_dev,
        struct list_head *iter;
        struct slave *slave;
 
+       spin_lock(&bond->stats_lock);
        memcpy(stats, &bond->bond_stats, sizeof(*stats));
 
-       bond_for_each_slave(bond, slave, iter) {
-               const struct rtnl_link_stats64 *sstats =
+       rcu_read_lock();
+       bond_for_each_slave_rcu(bond, slave, iter) {
+               const struct rtnl_link_stats64 *new =
                        dev_get_stats(slave->dev, &temp);
-               struct rtnl_link_stats64 *pstats = &slave->slave_stats;
-
-               stats->rx_packets +=  sstats->rx_packets - pstats->rx_packets;
-               stats->rx_bytes += sstats->rx_bytes - pstats->rx_bytes;
-               stats->rx_errors += sstats->rx_errors - pstats->rx_errors;
-               stats->rx_dropped += sstats->rx_dropped - pstats->rx_dropped;
-               stats->rx_nohandler += sstats->rx_nohandler - pstats->rx_nohandler;
-
-               stats->tx_packets += sstats->tx_packets - pstats->tx_packets;;
-               stats->tx_bytes += sstats->tx_bytes - pstats->tx_bytes;
-               stats->tx_errors += sstats->tx_errors - pstats->tx_errors;
-               stats->tx_dropped += sstats->tx_dropped - pstats->tx_dropped;
-
-               stats->multicast += sstats->multicast - pstats->multicast;
-               stats->collisions += sstats->collisions - pstats->collisions;
-
-               stats->rx_length_errors += sstats->rx_length_errors - pstats->rx_length_errors;
-               stats->rx_over_errors += sstats->rx_over_errors - pstats->rx_over_errors;
-               stats->rx_crc_errors += sstats->rx_crc_errors - pstats->rx_crc_errors;
-               stats->rx_frame_errors += sstats->rx_frame_errors - pstats->rx_frame_errors;
-               stats->rx_fifo_errors += sstats->rx_fifo_errors - pstats->rx_fifo_errors;
-               stats->rx_missed_errors += sstats->rx_missed_errors - pstats->rx_missed_errors;
-
-               stats->tx_aborted_errors += sstats->tx_aborted_errors - pstats->tx_aborted_errors;
-               stats->tx_carrier_errors += sstats->tx_carrier_errors - pstats->tx_carrier_errors;
-               stats->tx_fifo_errors += sstats->tx_fifo_errors - pstats->tx_fifo_errors;
-               stats->tx_heartbeat_errors += sstats->tx_heartbeat_errors - pstats->tx_heartbeat_errors;
-               stats->tx_window_errors += sstats->tx_window_errors - pstats->tx_window_errors;
+
+               bond_fold_stats(stats, new, &slave->slave_stats);
 
                /* save off the slave stats for the next run */
-               memcpy(pstats, sstats, sizeof(*sstats));
+               memcpy(&slave->slave_stats, new, sizeof(*new));
        }
+       rcu_read_unlock();
+
        memcpy(&bond->bond_stats, stats, sizeof(*stats));
+       spin_unlock(&bond->stats_lock);
 
        return stats;
 }
@@ -4160,6 +4163,7 @@ void bond_setup(struct net_device *bond_dev)
        struct bonding *bond = netdev_priv(bond_dev);
 
        spin_lock_init(&bond->mode_lock);
+       spin_lock_init(&bond->stats_lock);
        bond->params = bonding_defaults;
 
        /* Initialize pointers */

diff --git a/include/net/bonding.h b/include/net/bonding.h
index ee6c52053aa324800f82baf4cbe2674f47d56399..791800ddd6d90de23d7b7acea7a91e500e646eda 100644 (file)
--- a/include/net/bonding.h
+++ b/include/net/bonding.h
@@ -215,6 +215,7 @@ struct bonding {
         * ALB mode (6) - to sync the use and modifications of its hash table
         */
        spinlock_t mode_lock;
+       spinlock_t stats_lock;
        u8       send_peer_notif;
        u8       igmp_retrans;
 #ifdef CONFIG_PROC_FS