neigh: Protect neigh->ha[] with a seqlock

Add a seqlock in struct neighbour to protect neigh->ha[], and avoid
dirtying neighbour in stress situation (many different flows / dsts)

Dirtying takes place because of read_lock(&n->lock) and n->used writes.

Switching to a seqlock, and writing n->used only on jiffies changes
permits less dirtying.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 4 deletions

diff --git a/net/sched/sch_teql.c b/net/sched/sch_teql.c
index feaabc103ce6..401af9596709 100644
--- a/net/sched/sch_teql.c
+++ b/net/sched/sch_teql.c
@@ -241,11 +241,11 @@ __teql_resolve(struct sk_buff *skb, struct sk_buff *skb_res, struct net_device *
         }
         if (neigh_event_send(n, skb_res) == 0) {
                 int err;
+                char haddr[MAX_ADDR_LEN];
 
-                read_lock(&n->lock);
-                err = dev_hard_header(skb, dev, ntohs(skb->protocol),
-                                      n->ha, NULL, skb->len);
-                read_unlock(&n->lock);
+                neigh_ha_snapshot(haddr, n, dev);
+                err = dev_hard_header(skb, dev, ntohs(skb->protocol), haddr,
+                                      NULL, skb->len);
 
                 if (err < 0) {
                         neigh_release(n);