inet: simplify timewait refcounting

timewait sockets have a complex refcounting logic.
Once we realize it should be similar to established and
syn_recv sockets, we can use sk_nulls_del_node_init_rcu()
and remove inet_twsk_unhash()

In particular, deferred inet_twsk_put() added in commit
13475a30b66cd ("tcp: connect() race with timewait reuse")
looks unecessary : When removing a timewait socket from
ehash or bhash, caller must own a reference on the socket
anyway.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 36 deletions

diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 2ffbd16b79e0..92cd4d50404e 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -18,28 +18,6 @@
 
 
 /**
- *	inet_twsk_unhash - unhash a timewait socket from established hash
- *	@tw: timewait socket
- *
- *	unhash a timewait socket from established hash, if hashed.
- *	ehash lock must be held by caller.
- *	Returns 1 if caller should call inet_twsk_put() after lock release.
- */
-int inet_twsk_unhash(struct inet_timewait_sock *tw)
-{
-	if (hlist_nulls_unhashed(&tw->tw_node))
-		return 0;
-
-	hlist_nulls_del_rcu(&tw->tw_node);
-	sk_nulls_node_init(&tw->tw_node);
-	/*
-	 * We cannot call inet_twsk_put() ourself under lock,
-	 * caller must call it for us.
-	 */
-	return 1;
-}
-
-/**
  *	inet_twsk_bind_unhash - unhash a timewait socket from bind hash
  *	@tw: timewait socket
  *	@hashinfo: hashinfo pointer
@@ -48,35 +26,29 @@ int inet_twsk_unhash(struct inet_timewait_sock *tw)
  *	bind hash lock must be held by caller.
  *	Returns 1 if caller should call inet_twsk_put() after lock release.
  */
-int inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
+void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
 			  struct inet_hashinfo *hashinfo)
 {
 	struct inet_bind_bucket *tb = tw->tw_tb;
 
 	if (!tb)
-		return 0;
+		return;
 
 	__hlist_del(&tw->tw_bind_node);
 	tw->tw_tb = NULL;
 	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
-	/*
-	 * We cannot call inet_twsk_put() ourself under lock,
-	 * caller must call it for us.
-	 */
-	return 1;
+	__sock_put((struct sock *)tw);
 }
 
 /* Must be called with locally disabled BHs. */
 static void inet_twsk_kill(struct inet_timewait_sock *tw)
 {
 	struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
-	struct inet_bind_hashbucket *bhead;
-	int refcnt;
-	/* Unlink from established hashes. */
 	spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
+	struct inet_bind_hashbucket *bhead;
 
 	spin_lock(lock);
-	refcnt = inet_twsk_unhash(tw);
+	sk_nulls_del_node_init_rcu((struct sock *)tw);
 	spin_unlock(lock);
 
 	/* Disassociate with bind bucket. */
@@ -84,11 +56,9 @@ static void inet_twsk_kill(struct inet_timewait_sock *tw)
 			hashinfo->bhash_size)];
 
 	spin_lock(&bhead->lock);
-	refcnt += inet_twsk_bind_unhash(tw, hashinfo);
+	inet_twsk_bind_unhash(tw, hashinfo);
 	spin_unlock(&bhead->lock);
 
-	BUG_ON(refcnt >= atomic_read(&tw->tw_refcnt));
-	atomic_sub(refcnt, &tw->tw_refcnt);
 	atomic_dec(&tw->tw_dr->tw_count);
 	inet_twsk_put(tw);
 }