af_unix: Add helpers to calculate hashes.

This patch adds three helper functions that calculate hashes for unbound
sockets and bound sockets with BSD/abstract addresses.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/unix/af_unix.c

@@ -123,15 +123,38 @@ DEFINE_SPINLOCK(unix_table_lock);
 EXPORT_SYMBOL_GPL(unix_table_lock);
 static atomic_long_t unix_nr_socks;
 
+/* SMP locking strategy:
+ *    hash table is protected with spinlock unix_table_lock
+ *    each socket state is protected by separate spin lock.
+ */
 
-static struct hlist_head *unix_sockets_unbound(void *addr)
+static unsigned int unix_unbound_hash(struct sock *sk)
 {
-	unsigned long hash = (unsigned long)addr;
+	unsigned long hash = (unsigned long)sk;
 
 	hash ^= hash >> 16;
 	hash ^= hash >> 8;
-	hash %= UNIX_HASH_SIZE;
-	return &unix_socket_table[UNIX_HASH_SIZE + hash];
+	hash ^= sk->sk_type;
+
+	return UNIX_HASH_SIZE + (hash & (UNIX_HASH_SIZE - 1));
+}
+
+static unsigned int unix_bsd_hash(struct inode *i)
+{
+	return i->i_ino & (UNIX_HASH_SIZE - 1);
+}
+
+static unsigned int unix_abstract_hash(struct sockaddr_un *sunaddr,
+				       int addr_len, int type)
+{
+	__wsum csum = csum_partial(sunaddr, addr_len, 0);
+	unsigned int hash;
+
+	hash = (__force unsigned int)csum_fold(csum);
+	hash ^= hash >> 8;
+	hash ^= type;
+
+	return hash & (UNIX_HASH_SIZE - 1);
 }
 
 #ifdef CONFIG_SECURITY_NETWORK
@@ -162,20 +185,6 @@ static inline bool unix_secdata_eq(struct scm_cookie *scm, struct sk_buff *skb)
 }
 #endif /* CONFIG_SECURITY_NETWORK */
 
-/*
- *  SMP locking strategy:
- *    hash table is protected with spinlock unix_table_lock
- *    each socket state is protected by separate spin lock.
- */
-
-static inline unsigned int unix_hash_fold(__wsum n)
-{
-	unsigned int hash = (__force unsigned int)csum_fold(n);
-
-	hash ^= hash>>8;
-	return hash&(UNIX_HASH_SIZE-1);
-}
-
 #define unix_peer(sk) (unix_sk(sk)->peer)
 
 static inline int unix_our_peer(struct sock *sk, struct sock *osk)
@@ -334,11 +343,11 @@ static inline struct sock *unix_find_socket_byname(struct net *net,
 
 static struct sock *unix_find_socket_byinode(struct inode *i)
 {
+	unsigned int hash = unix_bsd_hash(i);
 	struct sock *s;
 
 	spin_lock(&unix_table_lock);
-	sk_for_each(s,
-		    &unix_socket_table[i->i_ino & (UNIX_HASH_SIZE - 1)]) {
+	sk_for_each(s, &unix_socket_table[hash]) {
 		struct dentry *dentry = unix_sk(s)->path.dentry;
 
 		if (dentry && d_backing_inode(dentry) == i) {
@@ -899,7 +908,7 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern,
 	init_waitqueue_head(&u->peer_wait);
 	init_waitqueue_func_entry(&u->peer_wake, unix_dgram_peer_wake_relay);
 	memset(&u->scm_stat, 0, sizeof(struct scm_stat));
-	unix_insert_socket(unix_sockets_unbound(sk), sk);
+	unix_insert_socket(&unix_socket_table[unix_unbound_hash(sk)], sk);
 
 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
 
@@ -1010,11 +1019,11 @@ static struct sock *unix_find_abstract(struct net *net,
 				       struct sockaddr_un *sunaddr,
 				       int addr_len, int type)
 {
-	unsigned int hash = unix_hash_fold(csum_partial(sunaddr, addr_len, 0));
+	unsigned int hash = unix_abstract_hash(sunaddr, addr_len, type);
 	struct dentry *dentry;
 	struct sock *sk;
 
-	sk = unix_find_socket_byname(net, sunaddr, addr_len, type ^ hash);
+	sk = unix_find_socket_byname(net, sunaddr, addr_len, hash);
 	if (!sk)
 		return ERR_PTR(-ECONNREFUSED);
 
@@ -1066,8 +1075,7 @@ static int unix_autobind(struct sock *sk)
 retry:
 	addr->len = sprintf(addr->name->sun_path + 1, "%05x", ordernum) +
 		offsetof(struct sockaddr_un, sun_path) + 1;
-	addr->hash = unix_hash_fold(csum_partial(addr->name, addr->len, 0));
-	addr->hash ^= sk->sk_type;
+	addr->hash = unix_abstract_hash(addr->name, addr->len, sk->sk_type);
 
 	spin_lock(&unix_table_lock);
 	ordernum = (ordernum+1)&0xFFFFF;
@@ -1144,7 +1152,7 @@ static int unix_bind_bsd(struct sock *sk, struct sockaddr_un *sunaddr,
 		goto out_unlock;
 
 	addr->hash = UNIX_HASH_SIZE;
-	hash = d_backing_inode(dentry)->i_ino & (UNIX_HASH_SIZE - 1);
+	hash = unix_bsd_hash(d_backing_inode(dentry));
 	spin_lock(&unix_table_lock);
 	u->path.mnt = mntget(parent.mnt);
 	u->path.dentry = dget(dentry);
@@ -1187,9 +1195,7 @@ static int unix_bind_abstract(struct sock *sk, struct sockaddr_un *sunaddr,
 		goto out_mutex;
 	}
 
-	addr->hash = unix_hash_fold(csum_partial(addr->name, addr->len, 0));
-	addr->hash ^= sk->sk_type;
-
+	addr->hash = unix_abstract_hash(addr->name, addr->len, sk->sk_type);
 	spin_lock(&unix_table_lock);
 
 	if (__unix_find_socket_byname(sock_net(sk), addr->name, addr->len,