net: listening_hash get a spinlock per bucket

This patch prepares RCU migration of listening_hash table for
TCP/DCCP protocols.

listening_hash table being small (32 slots per protocol), we add
a spinlock for each slot, instead of a single rwlock for whole table.

This should reduce hold time of readers, and writers concurrency.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 41b36720e977..1cb154ed75ad 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -718,13 +718,15 @@ static int inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
                 if (!(r->idiag_states & (TCPF_LISTEN | TCPF_SYN_RECV)))
                         goto skip_listen_ht;
 
-                inet_listen_lock(hashinfo);
                 for (i = s_i; i < INET_LHTABLE_SIZE; i++) {
                         struct sock *sk;
                         struct hlist_node *node;
+                        struct inet_listen_hashbucket *ilb;
 
                         num = 0;
-                        sk_for_each(sk, node, &hashinfo->listening_hash[i]) {
+                        ilb = &hashinfo->listening_hash[i];
+                        spin_lock_bh(&ilb->lock);
+                        sk_for_each(sk, node, &ilb->head) {
                                 struct inet_sock *inet = inet_sk(sk);
 
                                 if (num < s_num) {
@@ -742,7 +744,7 @@ static int inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
                                         goto syn_recv;
 
                                 if (inet_csk_diag_dump(sk, skb, cb) < 0) {
-                                        inet_listen_unlock(hashinfo);
+                                        spin_unlock_bh(&ilb->lock);
                                         goto done;
                                 }
 
@@ -751,7 +753,7 @@ syn_recv:
                                         goto next_listen;
 
                                 if (inet_diag_dump_reqs(skb, sk, cb) < 0) {
-                                        inet_listen_unlock(hashinfo);
+                                        spin_unlock_bh(&ilb->lock);
                                         goto done;
                                 }
 
@@ -760,12 +762,12 @@ next_listen:
                                 cb->args[4] = 0;
                                 ++num;
                         }
+                        spin_unlock_bh(&ilb->lock);
 
                         s_num = 0;
                         cb->args[3] = 0;
                         cb->args[4] = 0;
                 }
-                inet_listen_unlock(hashinfo);
 skip_listen_ht:
                 cb->args[0] = 1;
                 s_i = num = s_num = 0;