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>

5 files changed, 64 insertions, 89 deletions

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index bdf784c422b5..8b63394ec24c 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -44,12 +44,7 @@ atomic_t dccp_orphan_count = ATOMIC_INIT(0);
 
 EXPORT_SYMBOL_GPL(dccp_orphan_count);
 
-struct inet_hashinfo __cacheline_aligned dccp_hashinfo = {
-        .lhash_lock     = RW_LOCK_UNLOCKED,
-        .lhash_users    = ATOMIC_INIT(0),
-        .lhash_wait = __WAIT_QUEUE_HEAD_INITIALIZER(dccp_hashinfo.lhash_wait),
-};
-
+struct inet_hashinfo dccp_hashinfo;
 EXPORT_SYMBOL_GPL(dccp_hashinfo);
 
 /* the maximum queue length for tx in packets. 0 is no limit */
@@ -1030,6 +1025,7 @@ static int __init dccp_init(void)
         BUILD_BUG_ON(sizeof(struct dccp_skb_cb) >
                      FIELD_SIZEOF(struct sk_buff, cb));
 
+        inet_hashinfo_init(&dccp_hashinfo);
         dccp_hashinfo.bind_bucket_cachep =
                 kmem_cache_create("dccp_bind_bucket",
                                   sizeof(struct inet_bind_bucket), 0,
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;
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index fd269cfef0ec..377d004e5723 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -111,35 +111,6 @@ void __inet_inherit_port(struct sock *sk, struct sock *child)
 EXPORT_SYMBOL_GPL(__inet_inherit_port);
 
 /*
- * This lock without WQ_FLAG_EXCLUSIVE is good on UP and it can be very bad on SMP.
- * Look, when several writers sleep and reader wakes them up, all but one
- * immediately hit write lock and grab all the cpus. Exclusive sleep solves
- * this, _but_ remember, it adds useless work on UP machines (wake up each
- * exclusive lock release). It should be ifdefed really.
- */
-void inet_listen_wlock(struct inet_hashinfo *hashinfo)
-        __acquires(hashinfo->lhash_lock)
-{
-        write_lock(&hashinfo->lhash_lock);
-
-        if (atomic_read(&hashinfo->lhash_users)) {
-                DEFINE_WAIT(wait);
-
-                for (;;) {
-                        prepare_to_wait_exclusive(&hashinfo->lhash_wait,
-                                                  &wait, TASK_UNINTERRUPTIBLE);
-                        if (!atomic_read(&hashinfo->lhash_users))
-                                break;
-                        write_unlock_bh(&hashinfo->lhash_lock);
-                        schedule();
-                        write_lock_bh(&hashinfo->lhash_lock);
-                }
-
-                finish_wait(&hashinfo->lhash_wait, &wait);
-        }
-}
-
-/*
  * Don't inline this cruft. Here are some nice properties to exploit here. The
  * BSD API does not allow a listening sock to specify the remote port nor the
  * remote address for the connection. So always assume those are both
@@ -191,25 +162,25 @@ struct sock *__inet_lookup_listener(struct net *net,
                                     const int dif)
 {
         struct sock *sk = NULL;
-        const struct hlist_head *head;
+        struct inet_listen_hashbucket *ilb;
 
-        read_lock(&hashinfo->lhash_lock);
-        head = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
-        if (!hlist_empty(head)) {
-                const struct inet_sock *inet = inet_sk((sk = __sk_head(head)));
+        ilb = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
+        spin_lock(&ilb->lock);
+        if (!hlist_empty(&ilb->head)) {
+                const struct inet_sock *inet = inet_sk((sk = __sk_head(&ilb->head)));
 
                 if (inet->num == hnum && !sk->sk_node.next &&
                     (!inet->rcv_saddr || inet->rcv_saddr == daddr) &&
                     (sk->sk_family == PF_INET || !ipv6_only_sock(sk)) &&
                     !sk->sk_bound_dev_if && net_eq(sock_net(sk), net))
                         goto sherry_cache;
-                sk = inet_lookup_listener_slow(net, head, daddr, hnum, dif);
+                sk = inet_lookup_listener_slow(net, &ilb->head, daddr, hnum, dif);
         }
         if (sk) {
 sherry_cache:
                 sock_hold(sk);
         }
-        read_unlock(&hashinfo->lhash_lock);
+        spin_unlock(&ilb->lock);
         return sk;
 }
 EXPORT_SYMBOL_GPL(__inet_lookup_listener);
@@ -389,8 +360,7 @@ EXPORT_SYMBOL_GPL(__inet_hash_nolisten);
 static void __inet_hash(struct sock *sk)
 {
         struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
-        struct hlist_head *list;
-        rwlock_t *lock;
+        struct inet_listen_hashbucket *ilb;
 
         if (sk->sk_state != TCP_LISTEN) {
                 __inet_hash_nolisten(sk);
@@ -398,14 +368,12 @@ static void __inet_hash(struct sock *sk)
         }
 
         WARN_ON(!sk_unhashed(sk));
-        list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
-        lock = &hashinfo->lhash_lock;
+        ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
 
-        inet_listen_wlock(hashinfo);
-        __sk_add_node(sk, list);
+        spin_lock(&ilb->lock);
+        __sk_add_node(sk, &ilb->head);
         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
-        write_unlock(lock);
-        wake_up(&hashinfo->lhash_wait);
+        spin_unlock(&ilb->lock);
 }
 
 void inet_hash(struct sock *sk)
@@ -420,29 +388,27 @@ EXPORT_SYMBOL_GPL(inet_hash);
 
 void inet_unhash(struct sock *sk)
 {
-        rwlock_t *lock;
         struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
 
         if (sk_unhashed(sk))
-                goto out;
+                return;
 
         if (sk->sk_state == TCP_LISTEN) {
-                local_bh_disable();
-                inet_listen_wlock(hashinfo);
-                lock = &hashinfo->lhash_lock;
+                struct inet_listen_hashbucket *ilb;
+
+                ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
+                spin_lock_bh(&ilb->lock);
                 if (__sk_del_node_init(sk))
                         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
+                spin_unlock_bh(&ilb->lock);
         } else {
-                lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
+                rwlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
+
                 write_lock_bh(lock);
                 if (__sk_nulls_del_node_init_rcu(sk))
                         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
+                write_unlock_bh(lock);
         }
-
-        write_unlock_bh(lock);
-out:
-        if (sk->sk_state == TCP_LISTEN)
-                wake_up(&hashinfo->lhash_wait);
 }
 EXPORT_SYMBOL_GPL(inet_unhash);
 
@@ -556,3 +522,13 @@ int inet_hash_connect(struct inet_timewait_death_row *death_row,
 }
 
 EXPORT_SYMBOL_GPL(inet_hash_connect);
+
+void inet_hashinfo_init(struct inet_hashinfo *h)
+{
+        int i;
+
+        for (i = 0; i < INET_LHTABLE_SIZE; i++)
+                spin_lock_init(&h->listening_hash[i].lock);
+}
+
+EXPORT_SYMBOL_GPL(inet_hashinfo_init);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5559fea61e87..330b08a12274 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -97,11 +97,7 @@ struct tcp_md5sig_key *tcp_v4_md5_do_lookup(struct sock *sk, __be32 addr)
 }
 #endif
 
-struct inet_hashinfo __cacheline_aligned tcp_hashinfo = {
-        .lhash_lock  = __RW_LOCK_UNLOCKED(tcp_hashinfo.lhash_lock),
-        .lhash_users = ATOMIC_INIT(0),
-        .lhash_wait  = __WAIT_QUEUE_HEAD_INITIALIZER(tcp_hashinfo.lhash_wait),
-};
+struct inet_hashinfo tcp_hashinfo;
 
 static inline __u32 tcp_v4_init_sequence(struct sk_buff *skb)
 {
@@ -1874,15 +1870,18 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
         struct inet_connection_sock *icsk;
         struct hlist_node *node;
         struct sock *sk = cur;
+        struct inet_listen_hashbucket *ilb;
         struct tcp_iter_state *st = seq->private;
         struct net *net = seq_file_net(seq);
 
         if (!sk) {
                 st->bucket = 0;
-                sk = sk_head(&tcp_hashinfo.listening_hash[0]);
+                ilb = &tcp_hashinfo.listening_hash[0];
+                spin_lock_bh(&ilb->lock);
+                sk = sk_head(&ilb->head);
                 goto get_sk;
         }
-
+        ilb = &tcp_hashinfo.listening_hash[st->bucket];
         ++st->num;
 
         if (st->state == TCP_SEQ_STATE_OPENREQ) {
@@ -1932,8 +1931,11 @@ start_req:
                 }
                 read_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
         }
+        spin_unlock_bh(&ilb->lock);
         if (++st->bucket < INET_LHTABLE_SIZE) {
-                sk = sk_head(&tcp_hashinfo.listening_hash[st->bucket]);
+                ilb = &tcp_hashinfo.listening_hash[st->bucket];
+                spin_lock_bh(&ilb->lock);
+                sk = sk_head(&ilb->head);
                 goto get_sk;
         }
         cur = NULL;
@@ -2066,12 +2068,10 @@ static void *tcp_get_idx(struct seq_file *seq, loff_t pos)
         void *rc;
         struct tcp_iter_state *st = seq->private;
 
-        inet_listen_lock(&tcp_hashinfo);
         st->state = TCP_SEQ_STATE_LISTENING;
         rc        = listening_get_idx(seq, &pos);
 
         if (!rc) {
-                inet_listen_unlock(&tcp_hashinfo);
                 st->state = TCP_SEQ_STATE_ESTABLISHED;
                 rc        = established_get_idx(seq, pos);
         }
@@ -2103,7 +2103,6 @@ static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
         case TCP_SEQ_STATE_LISTENING:
                 rc = listening_get_next(seq, v);
                 if (!rc) {
-                        inet_listen_unlock(&tcp_hashinfo);
                         st->state = TCP_SEQ_STATE_ESTABLISHED;
                         rc        = established_get_first(seq);
                 }
@@ -2130,7 +2129,7 @@ static void tcp_seq_stop(struct seq_file *seq, void *v)
                 }
         case TCP_SEQ_STATE_LISTENING:
                 if (v != SEQ_START_TOKEN)
-                        inet_listen_unlock(&tcp_hashinfo);
+                        spin_unlock_bh(&tcp_hashinfo.listening_hash[st->bucket].lock);
                 break;
         case TCP_SEQ_STATE_TIME_WAIT:
         case TCP_SEQ_STATE_ESTABLISHED:
@@ -2405,6 +2404,7 @@ static struct pernet_operations __net_initdata tcp_sk_ops = {
 
 void __init tcp_v4_init(void)
 {
+        inet_hashinfo_init(&tcp_hashinfo);
         if (register_pernet_device(&tcp_sk_ops))
                 panic("Failed to create the TCP control socket.\n");
 }
diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index c1b4d401fd95..21544b9be259 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -25,30 +25,30 @@
 void __inet6_hash(struct sock *sk)
 {
         struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
-        rwlock_t *lock;
 
         WARN_ON(!sk_unhashed(sk));
 
         if (sk->sk_state == TCP_LISTEN) {
-                struct hlist_head *list;
+                struct inet_listen_hashbucket *ilb;
 
-                list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
-                lock = &hashinfo->lhash_lock;
-                inet_listen_wlock(hashinfo);
-                __sk_add_node(sk, list);
+                ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
+                spin_lock(&ilb->lock);
+                __sk_add_node(sk, &ilb->head);
+                spin_unlock(&ilb->lock);
         } else {
                 unsigned int hash;
                 struct hlist_nulls_head *list;
+                rwlock_t *lock;
 
                 sk->sk_hash = hash = inet6_sk_ehashfn(sk);
                 list = &inet_ehash_bucket(hashinfo, hash)->chain;
                 lock = inet_ehash_lockp(hashinfo, hash);
                 write_lock(lock);
                 __sk_nulls_add_node_rcu(sk, list);
+                write_unlock(lock);
         }
 
         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
-        write_unlock(lock);
 }
 EXPORT_SYMBOL(__inet6_hash);
 
@@ -126,10 +126,11 @@ struct sock *inet6_lookup_listener(struct net *net,
         const struct hlist_node *node;
         struct sock *result = NULL;
         int score, hiscore = 0;
+        struct inet_listen_hashbucket *ilb;
 
-        read_lock(&hashinfo->lhash_lock);
-        sk_for_each(sk, node,
-                        &hashinfo->listening_hash[inet_lhashfn(net, hnum)]) {
+        ilb = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
+        spin_lock(&ilb->lock);
+        sk_for_each(sk, node, &ilb->head) {
                 if (net_eq(sock_net(sk), net) && inet_sk(sk)->num == hnum &&
                                 sk->sk_family == PF_INET6) {
                         const struct ipv6_pinfo *np = inet6_sk(sk);
@@ -157,7 +158,7 @@ struct sock *inet6_lookup_listener(struct net *net,
         }
         if (result)
                 sock_hold(result);
-        read_unlock(&hashinfo->lhash_lock);
+        spin_unlock(&ilb->lock);
         return result;
 }