llc: replace the socket list with a local address based hash

For the cases where a lot of interfaces are used in conjunction with a
lot of LLC sockets bound to the same SAP, the iteration of the socket
list becomes prohibitively expensive.

Replacing the list with a a local address based hash significantly
improves the bind and listener lookup operations as well as the
datagram delivery.

Connected sockets delivery is also improved, but this patch does not
address the case where we have lots of sockets with the same local
address connected to different remote addresses.

In order to keep the socket sanity checks alive and fast a socket
counter was added to the SAP structure.

Signed-off-by: Octavian Purdila <opurdila@ixiacom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 51 insertions, 19 deletions

diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c
index 10cdfe2..a8dde9b 100644
--- a/net/llc/llc_conn.c
+++ b/net/llc/llc_conn.c
@@ -498,10 +498,12 @@ static struct sock *__llc_lookup_established(struct llc_sap *sap,
 {
 	struct sock *rc;
 	struct hlist_nulls_node *node;
+	int slot = llc_sk_laddr_hashfn(sap, laddr);
+	struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];
 
 	rcu_read_lock();
 again:
-	sk_nulls_for_each_rcu(rc, node, &sap->sk_list) {
+	sk_nulls_for_each_rcu(rc, node, laddr_hb) {
 		if (llc_estab_match(sap, daddr, laddr, rc)) {
 			/* Extra checks required by SLAB_DESTROY_BY_RCU */
 			if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
@@ -515,6 +517,13 @@ again:
 		}
 	}
 	rc = NULL;
+	/*
+	 * if the nulls value we got at the end of this lookup is
+	 * not the expected one, we must restart lookup.
+	 * We probably met an item that was moved to another chain.
+	 */
+	if (unlikely(get_nulls_value(node) != slot))
+		goto again;
 found:
 	rcu_read_unlock();
 	return rc;
@@ -540,29 +549,20 @@ static inline bool llc_listener_match(const struct llc_sap *sap,
 
 	return sk->sk_type == SOCK_STREAM && sk->sk_state == TCP_LISTEN &&
 		llc->laddr.lsap == laddr->lsap &&
-		(llc_mac_match(llc->laddr.mac, laddr->mac) ||
-		 llc_mac_null(llc->laddr.mac));
+		llc_mac_match(llc->laddr.mac, laddr->mac);
 }
 
-/**
- *	llc_lookup_listener - Finds listener for local MAC + SAP
- *	@sap: SAP
- *	@laddr: address of local LLC (MAC + SAP)
- *
- *	Search connection list of the SAP and finds connection listening on
- *	local mac, and local sap. Returns pointer for parent socket found,
- *	%NULL otherwise.
- *	Caller has to make sure local_bh is disabled.
- */
-static struct sock *llc_lookup_listener(struct llc_sap *sap,
-					struct llc_addr *laddr)
+static struct sock *__llc_lookup_listener(struct llc_sap *sap,
+					  struct llc_addr *laddr)
 {
 	struct sock *rc;
 	struct hlist_nulls_node *node;
+	int slot = llc_sk_laddr_hashfn(sap, laddr);
+	struct hlist_nulls_head *laddr_hb = &sap->sk_laddr_hash[slot];
 
 	rcu_read_lock();
 again:
-	sk_nulls_for_each_rcu(rc, node, &sap->sk_list) {
+	sk_nulls_for_each_rcu(rc, node, laddr_hb) {
 		if (llc_listener_match(sap, laddr, rc)) {
 			/* Extra checks required by SLAB_DESTROY_BY_RCU */
 			if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
@@ -576,11 +576,40 @@ again:
 		}
 	}
 	rc = NULL;
+	/*
+	 * if the nulls value we got at the end of this lookup is
+	 * not the expected one, we must restart lookup.
+	 * We probably met an item that was moved to another chain.
+	 */
+	if (unlikely(get_nulls_value(node) != slot))
+		goto again;
 found:
 	rcu_read_unlock();
 	return rc;
 }
 
+/**
+ *	llc_lookup_listener - Finds listener for local MAC + SAP
+ *	@sap: SAP
+ *	@laddr: address of local LLC (MAC + SAP)
+ *
+ *	Search connection list of the SAP and finds connection listening on
+ *	local mac, and local sap. Returns pointer for parent socket found,
+ *	%NULL otherwise.
+ *	Caller has to make sure local_bh is disabled.
+ */
+static struct sock *llc_lookup_listener(struct llc_sap *sap,
+					struct llc_addr *laddr)
+{
+	static struct llc_addr null_addr;
+	struct sock *rc = __llc_lookup_listener(sap, laddr);
+
+	if (!rc)
+		rc = __llc_lookup_listener(sap, &null_addr);
+
+	return rc;
+}
+
 static struct sock *__llc_lookup(struct llc_sap *sap,
 				 struct llc_addr *daddr,
 				 struct llc_addr *laddr)
@@ -678,18 +707,20 @@ static int llc_find_offset(int state, int ev_type)
  *	@sap: SAP
  *	@sk: socket
  *
- *	This function adds a socket to sk_list of a SAP.
+ *	This function adds a socket to the hash tables of a SAP.
  */
 void llc_sap_add_socket(struct llc_sap *sap, struct sock *sk)
 {
 	struct llc_sock *llc = llc_sk(sk);
 	struct hlist_head *dev_hb = llc_sk_dev_hash(sap, llc->dev->ifindex);
+	struct hlist_nulls_head *laddr_hb = llc_sk_laddr_hash(sap, &llc->laddr);
 
 	llc_sap_hold(sap);
 	llc_sk(sk)->sap = sap;
 
 	spin_lock_bh(&sap->sk_lock);
-	sk_nulls_add_node_rcu(sk, &sap->sk_list);
+	sap->sk_count++;
+	sk_nulls_add_node_rcu(sk, laddr_hb);
 	hlist_add_head(&llc->dev_hash_node, dev_hb);
 	spin_unlock_bh(&sap->sk_lock);
 }
@@ -699,7 +730,7 @@ void llc_sap_add_socket(struct llc_sap *sap, struct sock *sk)
  *	@sap: SAP
  *	@sk: socket
  *
- *	This function removes a connection from sk_list of a SAP if
+ *	This function removes a connection from the hash tables of a SAP if
  *	the connection was in this list.
  */
 void llc_sap_remove_socket(struct llc_sap *sap, struct sock *sk)
@@ -709,6 +740,7 @@ void llc_sap_remove_socket(struct llc_sap *sap, struct sock *sk)
 	spin_lock_bh(&sap->sk_lock);
 	sk_nulls_del_node_init_rcu(sk);
 	hlist_del(&llc->dev_hash_node);
+	sap->sk_count--;
 	spin_unlock_bh(&sap->sk_lock);
 	llc_sap_put(sap);
 }