1 files changed, 28 insertions, 103 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ec8b4b7ee2e2..32c9e83f44a6 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2863,104 +2863,42 @@ int tcp_gro_complete(struct sk_buff *skb)
 EXPORT_SYMBOL(tcp_gro_complete);
 
 #ifdef CONFIG_TCP_MD5SIG
-static unsigned long tcp_md5sig_users;
-static struct tcp_md5sig_pool __percpu *tcp_md5sig_pool;
-static DEFINE_SPINLOCK(tcp_md5sig_pool_lock);
+static DEFINE_PER_CPU(struct tcp_md5sig_pool, tcp_md5sig_pool);
+static DEFINE_MUTEX(tcp_md5sig_mutex);
+static bool tcp_md5sig_pool_populated = false;
 
-static void __tcp_free_md5sig_pool(struct tcp_md5sig_pool __percpu *pool)
+static void __tcp_alloc_md5sig_pool(void)
 {
 	int cpu;
 
 	for_each_possible_cpu(cpu) {
-		struct tcp_md5sig_pool *p = per_cpu_ptr(pool, cpu);
+		if (!per_cpu(tcp_md5sig_pool, cpu).md5_desc.tfm) {
+			struct crypto_hash *hash;
 
-		if (p->md5_desc.tfm)
-			crypto_free_hash(p->md5_desc.tfm);
-	}
-	free_percpu(pool);
-}
-
-void tcp_free_md5sig_pool(void)
-{
-	struct tcp_md5sig_pool __percpu *pool = NULL;
-
-	spin_lock_bh(&tcp_md5sig_pool_lock);
-	if (--tcp_md5sig_users == 0) {
-		pool = tcp_md5sig_pool;
-		tcp_md5sig_pool = NULL;
+			hash = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
+			if (IS_ERR_OR_NULL(hash))
+				return;
+			per_cpu(tcp_md5sig_pool, cpu).md5_desc.tfm = hash;
+		}
 	}
-	spin_unlock_bh(&tcp_md5sig_pool_lock);
-	if (pool)
-		__tcp_free_md5sig_pool(pool);
+	/* before setting tcp_md5sig_pool_populated, we must commit all writes
+	 * to memory. See smp_rmb() in tcp_get_md5sig_pool()
+	 */
+	smp_wmb();
+	tcp_md5sig_pool_populated = true;
 }
-EXPORT_SYMBOL(tcp_free_md5sig_pool);
 
-static struct tcp_md5sig_pool __percpu *
-__tcp_alloc_md5sig_pool(struct sock *sk)
+bool tcp_alloc_md5sig_pool(void)
 {
-	int cpu;
-	struct tcp_md5sig_pool __percpu *pool;
-
-	pool = alloc_percpu(struct tcp_md5sig_pool);
-	if (!pool)
-		return NULL;
-
-	for_each_possible_cpu(cpu) {
-		struct crypto_hash *hash;
+	if (unlikely(!tcp_md5sig_pool_populated)) {
+		mutex_lock(&tcp_md5sig_mutex);
 
-		hash = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
-		if (!hash || IS_ERR(hash))
-			goto out_free;
+		if (!tcp_md5sig_pool_populated)
+			__tcp_alloc_md5sig_pool();
 
-		per_cpu_ptr(pool, cpu)->md5_desc.tfm = hash;
+		mutex_unlock(&tcp_md5sig_mutex);
 	}
-	return pool;
-out_free:
-	__tcp_free_md5sig_pool(pool);
-	return NULL;
-}
-
-struct tcp_md5sig_pool __percpu *tcp_alloc_md5sig_pool(struct sock *sk)
-{
-	struct tcp_md5sig_pool __percpu *pool;
-	int alloc = 0;
-
-retry:
-	spin_lock_bh(&tcp_md5sig_pool_lock);
-	pool = tcp_md5sig_pool;
-	if (tcp_md5sig_users++ == 0) {
-		alloc = 1;
-		spin_unlock_bh(&tcp_md5sig_pool_lock);
-	} else if (!pool) {
-		tcp_md5sig_users--;
-		spin_unlock_bh(&tcp_md5sig_pool_lock);
-		cpu_relax();
-		goto retry;
-	} else
-		spin_unlock_bh(&tcp_md5sig_pool_lock);
-
-	if (alloc) {
-		/* we cannot hold spinlock here because this may sleep. */
-		struct tcp_md5sig_pool __percpu *p;
-
-		p = __tcp_alloc_md5sig_pool(sk);
-		spin_lock_bh(&tcp_md5sig_pool_lock);
-		if (!p) {
-			tcp_md5sig_users--;
-			spin_unlock_bh(&tcp_md5sig_pool_lock);
-			return NULL;
-		}
-		pool = tcp_md5sig_pool;
-		if (pool) {
-			/* oops, it has already been assigned. */
-			spin_unlock_bh(&tcp_md5sig_pool_lock);
-			__tcp_free_md5sig_pool(p);
-		} else {
-			tcp_md5sig_pool = pool = p;
-			spin_unlock_bh(&tcp_md5sig_pool_lock);
-		}
-	}
-	return pool;
+	return tcp_md5sig_pool_populated;
 }
 EXPORT_SYMBOL(tcp_alloc_md5sig_pool);
 
@@ -2974,31 +2912,18 @@ EXPORT_SYMBOL(tcp_alloc_md5sig_pool);
  */
 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void)
 {
-	struct tcp_md5sig_pool __percpu *p;
-
 	local_bh_disable();
 
-	spin_lock(&tcp_md5sig_pool_lock);
-	p = tcp_md5sig_pool;
-	if (p)
-		tcp_md5sig_users++;
-	spin_unlock(&tcp_md5sig_pool_lock);
-
-	if (p)
-		return this_cpu_ptr(p);
-
+	if (tcp_md5sig_pool_populated) {
+		/* coupled with smp_wmb() in __tcp_alloc_md5sig_pool() */
+		smp_rmb();
+		return this_cpu_ptr(&tcp_md5sig_pool);
+	}
 	local_bh_enable();
 	return NULL;
 }
 EXPORT_SYMBOL(tcp_get_md5sig_pool);
 
-void tcp_put_md5sig_pool(void)
-{
-	local_bh_enable();
-	tcp_free_md5sig_pool();
-}
-EXPORT_SYMBOL(tcp_put_md5sig_pool);
-
 int tcp_md5_hash_header(struct tcp_md5sig_pool *hp,
 			const struct tcphdr *th)
 {