raw: complete rcu conversion

raw_diag_dump() can use rcu_read_lock() instead of read_lock()

Now the hashinfo lock is only used from process context,
in write mode only, we can convert it to a spinlock,
and we do not need to block BH anymore.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20220620100509.3493504-1-eric.dumazet@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

include/net/raw.h

@@ -32,15 +32,15 @@ int raw_rcv(struct sock *, struct sk_buff *);
 #define RAW_HTABLE_SIZE	MAX_INET_PROTOS
 
 struct raw_hashinfo {
-	rwlock_t lock;
+	spinlock_t lock;
 	struct hlist_nulls_head ht[RAW_HTABLE_SIZE];
 };
 
 static inline void raw_hashinfo_init(struct raw_hashinfo *hashinfo)
 {
 	int i;
 
-	rwlock_init(&hashinfo->lock);
+	spin_lock_init(&hashinfo->lock);
 	for (i = 0; i < RAW_HTABLE_SIZE; i++)
 		INIT_HLIST_NULLS_HEAD(&hashinfo->ht[i], i);
 }

net/ipv4/raw.c

@@ -95,10 +95,10 @@ int raw_hash_sk(struct sock *sk)
 
 	hlist = &h->ht[inet_sk(sk)->inet_num & (RAW_HTABLE_SIZE - 1)];
 
-	write_lock_bh(&h->lock);
+	spin_lock(&h->lock);
 	__sk_nulls_add_node_rcu(sk, hlist);
 	sock_set_flag(sk, SOCK_RCU_FREE);
-	write_unlock_bh(&h->lock);
+	spin_unlock(&h->lock);
 	sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
 
 	return 0;
@@ -109,10 +109,10 @@ void raw_unhash_sk(struct sock *sk)
 {
 	struct raw_hashinfo *h = sk->sk_prot->h.raw_hash;
 
-	write_lock_bh(&h->lock);
+	spin_lock(&h->lock);
 	if (__sk_nulls_del_node_init_rcu(sk))
 		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
-	write_unlock_bh(&h->lock);
+	spin_unlock(&h->lock);
 }
 EXPORT_SYMBOL_GPL(raw_unhash_sk);
 

net/ipv4/raw_diag.c

@@ -156,7 +156,7 @@ static void raw_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
 	s_slot = cb->args[0];
 	num = s_num = cb->args[1];
 
-	read_lock(&hashinfo->lock);
+	rcu_read_lock();
 	for (slot = s_slot; slot < RAW_HTABLE_SIZE; s_num = 0, slot++) {
 		num = 0;
 
@@ -184,7 +184,7 @@ static void raw_diag_dump(struct sk_buff *skb, struct netlink_callback *cb,
 	}
 
 out_unlock:
-	read_unlock(&hashinfo->lock);
+	rcu_read_unlock();
 
 	cb->args[0] = slot;
 	cb->args[1] = num;