Preparing for udp 4-tuple hash (uhash4 for short).

To implement uhash4 without cache line missing when lookup, hslot2 is
used to record the number of hashed sockets in hslot4. Thus adding a new
struct udp_hslot_main with field hash4_cnt, which is used by hash2. The
new struct is used to avoid doubling the size of udp_hslot.

Before uhash4 lookup, firstly checking hash4_cnt to see if there are
hashed sks in hslot4. Because hslot2 is always used in lookup, there is
no cache line miss.

Related helpers are updated, and use the helpers as possible.

uhash4 is implemented in following patches.

Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
---
 include/net/udp.h | 37 +++++++++++++++++++++++++++++++++----
 net/ipv4/udp.c    | 44 +++++++++++++++++++++++---------------------
 net/ipv6/udp.c    | 15 ++++++---------
 3 files changed, 62 insertions(+), 34 deletions(-)

diff --git a/include/net/udp.h b/include/net/udp.h
index 61222545ab1cf..f4e04616c27fc 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -50,7 +50,7 @@ struct udp_skb_cb {
 #define UDP_SKB_CB(__skb)	((struct udp_skb_cb *)((__skb)->cb))
 
 /**
- *	struct udp_hslot - UDP hash slot
+ *	struct udp_hslot - UDP hash slot used by udp_table.hash
  *
  *	@head:	head of list of sockets
  *	@count:	number of sockets in 'head' list
@@ -60,7 +60,21 @@ struct udp_hslot {
 	struct hlist_head	head;
 	int			count;
 	spinlock_t		lock;
-} __attribute__((aligned(2 * sizeof(long))));
+} __aligned(2 * sizeof(long));
+
+/**
+ *	struct udp_hslot_main - UDP hash slot used by udp_table.hash2
+ *
+ *	@hslot:	basic hash slot
+ *	@hash4_cnt: number of sockets in hslot4 of the same (local port, local address)
+ */
+struct udp_hslot_main {
+	struct udp_hslot	hslot; /* must be the first member */
+#if !IS_ENABLED(CONFIG_BASE_SMALL)
+	u32			hash4_cnt;
+#endif
+} __aligned(2 * sizeof(long));
+#define UDP_HSLOT_MAIN(__hslot) ((struct udp_hslot_main *)(__hslot))
 
 /**
  *	struct udp_table - UDP table
@@ -72,7 +86,7 @@ struct udp_hslot {
  */
 struct udp_table {
 	struct udp_hslot	*hash;
-	struct udp_hslot	*hash2;
+	struct udp_hslot_main	*hash2;
 	unsigned int		mask;
 	unsigned int		log;
 };
@@ -84,6 +98,7 @@ static inline struct udp_hslot *udp_hashslot(struct udp_table *table,
 {
 	return &table->hash[udp_hashfn(net, num, table->mask)];
 }
+
 /*
  * For secondary hash, net_hash_mix() is performed before calling
  * udp_hashslot2(), this explains difference with udp_hashslot()
@@ -91,8 +106,22 @@ static inline struct udp_hslot *udp_hashslot(struct udp_table *table,
 static inline struct udp_hslot *udp_hashslot2(struct udp_table *table,
 					      unsigned int hash)
 {
-	return &table->hash2[hash & table->mask];
+	return &table->hash2[hash & table->mask].hslot;
+}
+
+#if IS_ENABLED(CONFIG_BASE_SMALL)
+static inline void udp_table_hash4_init(struct udp_table *table)
+{
+}
+#else /* !CONFIG_BASE_SMALL */
+
+/* Must be called with table->hash2 initialized */
+static inline void udp_table_hash4_init(struct udp_table *table)
+{
+	for (int i = 0; i <= table->mask; i++)
+		table->hash2[i].hash4_cnt = 0;
 }
+#endif /* CONFIG_BASE_SMALL */
 
 extern struct proto udp_prot;
 
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 0e24916b39d46..2fdac5fae2a80 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -486,13 +486,12 @@ struct sock *__udp4_lib_lookup(const struct net *net, __be32 saddr,
 		int sdif, struct udp_table *udptable, struct sk_buff *skb)
 {
 	unsigned short hnum = ntohs(dport);
-	unsigned int hash2, slot2;
 	struct udp_hslot *hslot2;
 	struct sock *result, *sk;
+	unsigned int hash2;
 
 	hash2 = ipv4_portaddr_hash(net, daddr, hnum);
-	slot2 = hash2 & udptable->mask;
-	hslot2 = &udptable->hash2[slot2];
+	hslot2 = udp_hashslot2(udptable, hash2);
 
 	/* Lookup connected or non-wildcard socket */
 	result = udp4_lib_lookup2(net, saddr, sport,
@@ -519,8 +518,7 @@ struct sock *__udp4_lib_lookup(const struct net *net, __be32 saddr,
 
 	/* Lookup wildcard sockets */
 	hash2 = ipv4_portaddr_hash(net, htonl(INADDR_ANY), hnum);
-	slot2 = hash2 & udptable->mask;
-	hslot2 = &udptable->hash2[slot2];
+	hslot2 = udp_hashslot2(udptable, hash2);
 
 	result = udp4_lib_lookup2(net, saddr, sport,
 				  htonl(INADDR_ANY), hnum, dif, sdif,
@@ -2268,7 +2266,7 @@ static int __udp4_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
 			    udptable->mask;
 		hash2 = ipv4_portaddr_hash(net, daddr, hnum) & udptable->mask;
 start_lookup:
-		hslot = &udptable->hash2[hash2];
+		hslot = &udptable->hash2[hash2].hslot;
 		offset = offsetof(typeof(*sk), __sk_common.skc_portaddr_node);
 	}
 
@@ -2539,14 +2537,13 @@ static struct sock *__udp4_lib_demux_lookup(struct net *net,
 	struct udp_table *udptable = net->ipv4.udp_table;
 	INET_ADDR_COOKIE(acookie, rmt_addr, loc_addr);
 	unsigned short hnum = ntohs(loc_port);
-	unsigned int hash2, slot2;
 	struct udp_hslot *hslot2;
+	unsigned int hash2;
 	__portpair ports;
 	struct sock *sk;
 
 	hash2 = ipv4_portaddr_hash(net, loc_addr, hnum);
-	slot2 = hash2 & udptable->mask;
-	hslot2 = &udptable->hash2[slot2];
+	hslot2 = udp_hashslot2(udptable, hash2);
 	ports = INET_COMBINED_PORTS(rmt_port, hnum);
 
 	udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
@@ -3187,7 +3184,7 @@ static struct sock *bpf_iter_udp_batch(struct seq_file *seq)
 	batch_sks = 0;
 
 	for (; state->bucket <= udptable->mask; state->bucket++) {
-		struct udp_hslot *hslot2 = &udptable->hash2[state->bucket];
+		struct udp_hslot *hslot2 = &udptable->hash2[state->bucket].hslot;
 
 		if (hlist_empty(&hslot2->head))
 			continue;
@@ -3428,10 +3425,11 @@ __setup("uhash_entries=", set_uhash_entries);
 
 void __init udp_table_init(struct udp_table *table, const char *name)
 {
-	unsigned int i;
+	unsigned int i, slot_size;
 
+	slot_size = sizeof(struct udp_hslot) + sizeof(struct udp_hslot_main);
 	table->hash = alloc_large_system_hash(name,
-					      2 * sizeof(struct udp_hslot),
+					      slot_size,
 					      uhash_entries,
 					      21, /* one slot per 2 MB */
 					      0,
@@ -3440,17 +3438,18 @@ void __init udp_table_init(struct udp_table *table, const char *name)
 					      UDP_HTABLE_SIZE_MIN,
 					      UDP_HTABLE_SIZE_MAX);
 
-	table->hash2 = table->hash + (table->mask + 1);
+	table->hash2 = (void *)(table->hash + (table->mask + 1));
 	for (i = 0; i <= table->mask; i++) {
 		INIT_HLIST_HEAD(&table->hash[i].head);
 		table->hash[i].count = 0;
 		spin_lock_init(&table->hash[i].lock);
 	}
 	for (i = 0; i <= table->mask; i++) {
-		INIT_HLIST_HEAD(&table->hash2[i].head);
-		table->hash2[i].count = 0;
-		spin_lock_init(&table->hash2[i].lock);
+		INIT_HLIST_HEAD(&table->hash2[i].hslot.head);
+		table->hash2[i].hslot.count = 0;
+		spin_lock_init(&table->hash2[i].hslot.lock);
 	}
+	udp_table_hash4_init(table);
 }
 
 u32 udp_flow_hashrnd(void)
@@ -3476,18 +3475,20 @@ static void __net_init udp_sysctl_init(struct net *net)
 static struct udp_table __net_init *udp_pernet_table_alloc(unsigned int hash_entries)
 {
 	struct udp_table *udptable;
+	unsigned int slot_size;
 	int i;
 
 	udptable = kmalloc(sizeof(*udptable), GFP_KERNEL);
 	if (!udptable)
 		goto out;
 
-	udptable->hash = vmalloc_huge(hash_entries * 2 * sizeof(struct udp_hslot),
+	slot_size = sizeof(struct udp_hslot) + sizeof(struct udp_hslot_main);
+	udptable->hash = vmalloc_huge(hash_entries * slot_size,
 				      GFP_KERNEL_ACCOUNT);
 	if (!udptable->hash)
 		goto free_table;
 
-	udptable->hash2 = udptable->hash + hash_entries;
+	udptable->hash2 = (void *)(udptable->hash + hash_entries);
 	udptable->mask = hash_entries - 1;
 	udptable->log = ilog2(hash_entries);
 
@@ -3496,10 +3497,11 @@ static struct udp_table __net_init *udp_pernet_table_alloc(unsigned int hash_ent
 		udptable->hash[i].count = 0;
 		spin_lock_init(&udptable->hash[i].lock);
 
-		INIT_HLIST_HEAD(&udptable->hash2[i].head);
-		udptable->hash2[i].count = 0;
-		spin_lock_init(&udptable->hash2[i].lock);
+		INIT_HLIST_HEAD(&udptable->hash2[i].hslot.head);
+		udptable->hash2[i].hslot.count = 0;
+		spin_lock_init(&udptable->hash2[i].hslot.lock);
 	}
+	udp_table_hash4_init(udptable);
 
 	return udptable;
 
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 0cef8ae5d1ea1..0d7aac9d44e59 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -224,13 +224,12 @@ struct sock *__udp6_lib_lookup(const struct net *net,
 			       struct sk_buff *skb)
 {
 	unsigned short hnum = ntohs(dport);
-	unsigned int hash2, slot2;
 	struct udp_hslot *hslot2;
 	struct sock *result, *sk;
+	unsigned int hash2;
 
 	hash2 = ipv6_portaddr_hash(net, daddr, hnum);
-	slot2 = hash2 & udptable->mask;
-	hslot2 = &udptable->hash2[slot2];
+	hslot2 = udp_hashslot2(udptable, hash2);
 
 	/* Lookup connected or non-wildcard sockets */
 	result = udp6_lib_lookup2(net, saddr, sport,
@@ -257,8 +256,7 @@ struct sock *__udp6_lib_lookup(const struct net *net,
 
 	/* Lookup wildcard sockets */
 	hash2 = ipv6_portaddr_hash(net, &in6addr_any, hnum);
-	slot2 = hash2 & udptable->mask;
-	hslot2 = &udptable->hash2[slot2];
+	hslot2 = udp_hashslot2(udptable, hash2);
 
 	result = udp6_lib_lookup2(net, saddr, sport,
 				  &in6addr_any, hnum, dif, sdif,
@@ -859,7 +857,7 @@ static int __udp6_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
 			    udptable->mask;
 		hash2 = ipv6_portaddr_hash(net, daddr, hnum) & udptable->mask;
 start_lookup:
-		hslot = &udptable->hash2[hash2];
+		hslot = &udptable->hash2[hash2].hslot;
 		offset = offsetof(typeof(*sk), __sk_common.skc_portaddr_node);
 	}
 
@@ -1065,14 +1063,13 @@ static struct sock *__udp6_lib_demux_lookup(struct net *net,
 {
 	struct udp_table *udptable = net->ipv4.udp_table;
 	unsigned short hnum = ntohs(loc_port);
-	unsigned int hash2, slot2;
 	struct udp_hslot *hslot2;
+	unsigned int hash2;
 	__portpair ports;
 	struct sock *sk;
 
 	hash2 = ipv6_portaddr_hash(net, loc_addr, hnum);
-	slot2 = hash2 & udptable->mask;
-	hslot2 = &udptable->hash2[slot2];
+	hslot2 = udp_hashslot2(udptable, hash2);
 	ports = INET_COMBINED_PORTS(rmt_port, hnum);
 
 	udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
-- 
2.32.0.3.g01195cf9f