net: inet: Retire port only listening_hash

The listen sk is currently stored in two hash tables,
listening_hash (hashed by port) and lhash2 (hashed by port and address).

After commit 0ee58dad5b06 ("net: tcp6: prefer listeners bound to an address")
and commit d9fbc7f6431f ("net: tcp: prefer listeners bound to an address"),
the TCP-SYN lookup fast path does not use listening_hash.

The commit 05c0b35709c5 ("tcp: seq_file: Replace listening_hash with lhash2")
also moved the seq_file (/proc/net/tcp) iteration usage from
listening_hash to lhash2.

There are still a few listening_hash usages left.
One of them is inet_reuseport_add_sock() which uses the listening_hash
to search a listen sk during the listen() system call.  This turns
out to be very slow on use cases that listen on many different
VIPs at a popular port (e.g. 443).  [ On top of the slowness in
adding to the tail in the IPv6 case ].  The latter patch has a
selftest to demonstrate this case.

This patch takes this chance to move all remaining listening_hash
usages to lhash2 and then retire listening_hash.

Since most changes need to be done together, it is hard to cut
the listening_hash to lhash2 switch into small patches.  The
changes in this patch is highlighted here for the review
purpose.

1. Because of the listening_hash removal, lhash2 can use the
   sk->sk_nulls_node instead of the icsk->icsk_listen_portaddr_node.
   This will also keep the sk_unhashed() check to work as is
   after stop adding sk to listening_hash.

   The union is removed from inet_listen_hashbucket because
   only nulls_head is needed.

2. icsk->icsk_listen_portaddr_node and its helpers are removed.

3. The current lhash2 users needs to iterate with sk_nulls_node
   instead of icsk_listen_portaddr_node.

   One case is in the inet[6]_lhash2_lookup().

   Another case is the seq_file iterator in tcp_ipv4.c.
   One thing to note is sk_nulls_next() is needed
   because the old inet_lhash2_for_each_icsk_continue()
   does a "next" first before iterating.

4. Move the remaining listening_hash usage to lhash2

   inet_reuseport_add_sock() which this series is
   trying to improve.

   inet_diag.c and mptcp_diag.c are the final two
   remaining use cases and is moved to lhash2 now also.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 1 insertions, 40 deletions

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index 103fc7a30e60..1b8706719d4f 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -111,10 +111,7 @@ struct inet_bind_hashbucket {
 #define LISTENING_NULLS_BASE (1U << 29)
 struct inet_listen_hashbucket {
 	spinlock_t		lock;
-	union {
-		struct hlist_head	head;
-		struct hlist_nulls_head	nulls_head;
-	};
+	struct hlist_nulls_head	nulls_head;
 };
 
 /* This is for listening sockets, thus all sockets which possess wildcards. */
@@ -142,32 +139,8 @@ struct inet_hashinfo {
 	/* The 2nd listener table hashed by local port and address */
 	unsigned int			lhash2_mask;
 	struct inet_listen_hashbucket	*lhash2;
-
-	/* All the above members are written once at bootup and
-	 * never written again _or_ are predominantly read-access.
-	 *
-	 * Now align to a new cache line as all the following members
-	 * might be often dirty.
-	 */
-	/* All sockets in TCP_LISTEN state will be in listening_hash.
-	 * This is the only table where wildcard'd TCP sockets can
-	 * exist.  listening_hash is only hashed by local port number.
-	 * If lhash2 is initialized, the same socket will also be hashed
-	 * to lhash2 by port and address.
-	 */
-	struct inet_listen_hashbucket	listening_hash[INET_LHTABLE_SIZE]
-					____cacheline_aligned_in_smp;
 };
 
-#define inet_lhash2_for_each_icsk_continue(__icsk) \
-	hlist_for_each_entry_continue(__icsk, icsk_listen_portaddr_node)
-
-#define inet_lhash2_for_each_icsk(__icsk, list) \
-	hlist_for_each_entry(__icsk, list, icsk_listen_portaddr_node)
-
-#define inet_lhash2_for_each_icsk_rcu(__icsk, list) \
-	hlist_for_each_entry_rcu(__icsk, list, icsk_listen_portaddr_node)
-
 static inline struct inet_listen_hashbucket *
 inet_lhash2_bucket(struct inet_hashinfo *h, u32 hash)
 {
@@ -229,23 +202,11 @@ static inline u32 inet_bhashfn(const struct net *net, const __u16 lport,
 void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
 		    const unsigned short snum);
 
-/* These can have wildcards, don't try too hard. */
-static inline u32 inet_lhashfn(const struct net *net, const unsigned short num)
-{
-	return (num + net_hash_mix(net)) & (INET_LHTABLE_SIZE - 1);
-}
-
-static inline int inet_sk_listen_hashfn(const struct sock *sk)
-{
-	return inet_lhashfn(sock_net(sk), inet_sk(sk)->inet_num);
-}
-
 /* Caller must disable local BH processing. */
 int __inet_inherit_port(const struct sock *sk, struct sock *child);
 
 void inet_put_port(struct sock *sk);
 
-void inet_hashinfo_init(struct inet_hashinfo *h);
 void inet_hashinfo2_init(struct inet_hashinfo *h, const char *name,
 			 unsigned long numentries, int scale,
 			 unsigned long low_limit,