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>
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index f353095..d8e540c 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -502,10 +502,8 @@
if (n) {
n->used = jiffies;
- if (n->nud_state&NUD_VALID || neigh_event_send(n, skb) == 0) {
- read_lock_bh(&n->lock);
- memcpy(haddr, n->ha, dev->addr_len);
- read_unlock_bh(&n->lock);
+ if (n->nud_state & NUD_VALID || neigh_event_send(n, skb) == 0) {
+ neigh_ha_snapshot(haddr, n, dev);
neigh_release(n);
return 0;
}