tcp: md5: remove spinlock usage in fast path

TCP md5 code uses per cpu variables but protects access to them with
a shared spinlock, which is a contention point.

[ tcp_md5sig_pool_lock is locked twice per incoming packet ]

Makes things much simpler, by allocating crypto structures once, first
time a socket needs md5 keys, and not deallocating them as they are
really small.

Next step would be to allow crypto allocations being done in a NUMA
aware way.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 9 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 719652305a29..d20ede0c9593 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1026,7 +1026,7 @@ int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
         key = sock_kmalloc(sk, sizeof(*key), gfp);
         if (!key)
                 return -ENOMEM;
-        if (hlist_empty(&md5sig->head) && !tcp_alloc_md5sig_pool(sk)) {
+        if (!tcp_alloc_md5sig_pool()) {
                 sock_kfree_s(sk, key, sizeof(*key));
                 return -ENOMEM;
         }
@@ -1044,9 +1044,7 @@ EXPORT_SYMBOL(tcp_md5_do_add);
 
 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr, int family)
 {
-        struct tcp_sock *tp = tcp_sk(sk);
         struct tcp_md5sig_key *key;
-        struct tcp_md5sig_info *md5sig;
 
         key = tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&addr, AF_INET);
         if (!key)
@@ -1054,10 +1052,6 @@ int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr, int family)
         hlist_del_rcu(&key->node);
         atomic_sub(sizeof(*key), &sk->sk_omem_alloc);
         kfree_rcu(key, rcu);
-        md5sig = rcu_dereference_protected(tp->md5sig_info,
-                                           sock_owned_by_user(sk));
-        if (hlist_empty(&md5sig->head))
-                tcp_free_md5sig_pool();
         return 0;
 }
 EXPORT_SYMBOL(tcp_md5_do_del);
@@ -1071,8 +1065,6 @@ static void tcp_clear_md5_list(struct sock *sk)
 
         md5sig = rcu_dereference_protected(tp->md5sig_info, 1);
 
-        if (!hlist_empty(&md5sig->head))
-                tcp_free_md5sig_pool();
         hlist_for_each_entry_safe(key, n, &md5sig->head, node) {
                 hlist_del_rcu(&key->node);
                 atomic_sub(sizeof(*key), &sk->sk_omem_alloc);