udp: add a counter into udp_hslot

Adds a counter in udp_hslot to keep an accurate count
of sockets present in chain.

This will permit to upcoming UDP lookup algo to chose
the shortest chain when secondary hash is added.

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

2 files changed, 11 insertions, 0 deletions

diff --git a/include/net/udp.h b/include/net/udp.h
index 22aa2e7eb1d7..9167281e47dc 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -50,8 +50,16 @@ struct udp_skb_cb {
 };
 #define UDP_SKB_CB(__skb)       ((struct udp_skb_cb *)((__skb)->cb))
 
+/**
+ *      struct udp_hslot - UDP hash slot
+ *
+ *      @head:  head of list of sockets
+ *      @count: number of sockets in 'head' list
+ *      @lock:  spinlock protecting changes to head/count
+ */
 struct udp_hslot {
         struct hlist_nulls_head head;
+        int                     count;
         spinlock_t              lock;
 } __attribute__((aligned(2 * sizeof(long))));
 
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index d5e75e976513..ffc837643a04 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -218,6 +218,7 @@ found:
         sk->sk_hash = snum;
         if (sk_unhashed(sk)) {
                 sk_nulls_add_node_rcu(sk, &hslot->head);
+                hslot->count++;
                 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
         }
         error = 0;
@@ -1053,6 +1054,7 @@ void udp_lib_unhash(struct sock *sk)
 
                 spin_lock_bh(&hslot->lock);
                 if (sk_nulls_del_node_init_rcu(sk)) {
+                        hslot->count--;
                         inet_sk(sk)->inet_num = 0;
                         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
                 }
@@ -1862,6 +1864,7 @@ void __init udp_table_init(struct udp_table *table, const char *name)
         }
         for (i = 0; i <= table->mask; i++) {
                 INIT_HLIST_NULLS_HEAD(&table->hash[i].head, i);
+                table->hash[i].count = 0;
                 spin_lock_init(&table->hash[i].lock);
         }
 }