Merge branch 'udpv6_lockless_send'

Vladislav Yasevich says:

====================
ipv6: Add lockless UDP send path

This series introduces a lockless UDPv6 send path similar to
what Herbert Xu did for IPv4 a while ago.

There are some difference from IPv4.  IPv6 caching for flow
label is a bit different, as well as it requires another cork
cork structure that holds the IPv6 ancillary data.

Please take a look.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -125,6 +125,12 @@ struct ipv6_mc_socklist;
 struct ipv6_ac_socklist;
 struct ipv6_fl_socklist;
 
+struct inet6_cork {
+	struct ipv6_txoptions *opt;
+	u8 hop_limit;
+	u8 tclass;
+};
+
 /**
  * struct ipv6_pinfo - ipv6 private area
  *
@@ -217,11 +223,7 @@ struct ipv6_pinfo {
 	struct ipv6_txoptions	*opt;
 	struct sk_buff		*pktoptions;
 	struct sk_buff		*rxpmtu;
-	struct {
-		struct ipv6_txoptions *opt;
-		u8 hop_limit;
-		u8 tclass;
-	} cork;
+	struct inet6_cork	cork;
 };
 
 /* WARNING: don't change the layout of the members in {raw,udp,tcp}6_sock! */

include/net/ipv6.h

@@ -788,6 +788,25 @@ int ip6_push_pending_frames(struct sock *sk);
 
 void ip6_flush_pending_frames(struct sock *sk);
 
+int ip6_send_skb(struct sk_buff *skb);
+
+struct sk_buff *__ip6_make_skb(struct sock *sk, struct sk_buff_head *queue,
+			       struct inet_cork_full *cork,
+			       struct inet6_cork *v6_cork);
+struct sk_buff *ip6_make_skb(struct sock *sk,
+			     int getfrag(void *from, char *to, int offset,
+					 int len, int odd, struct sk_buff *skb),
+			     void *from, int length, int transhdrlen,
+			     int hlimit, int tclass, struct ipv6_txoptions *opt,
+			     struct flowi6 *fl6, struct rt6_info *rt,
+			     unsigned int flags, int dontfrag);
+
+static inline struct sk_buff *ip6_finish_skb(struct sock *sk)
+{
+	return __ip6_make_skb(sk, &sk->sk_write_queue, &inet_sk(sk)->cork,
+			      &inet6_sk(sk)->cork);
+}
+
 int ip6_dst_lookup(struct sock *sk, struct dst_entry **dst, struct flowi6 *fl6);
 struct dst_entry *ip6_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
 				      const struct in6_addr *final_dst);

net/ipv6/udp.c

@@ -990,9 +990,10 @@ static void udp6_hwcsum_outgoing(struct sock *sk, struct sk_buff *skb,
 {
 	unsigned int offset;
 	struct udphdr *uh = udp_hdr(skb);
+	struct sk_buff *frags = skb_shinfo(skb)->frag_list;
 	__wsum csum = 0;
 
-	if (skb_queue_len(&sk->sk_write_queue) == 1) {
+	if (!frags) {
 		/* Only one fragment on the socket.  */
 		skb->csum_start = skb_transport_header(skb) - skb->head;
 		skb->csum_offset = offsetof(struct udphdr, check);
@@ -1008,9 +1009,9 @@ static void udp6_hwcsum_outgoing(struct sock *sk, struct sk_buff *skb,
 
 		skb->ip_summed = CHECKSUM_NONE;
 
-		skb_queue_walk(&sk->sk_write_queue, skb) {
-			csum = csum_add(csum, skb->csum);
-		}
+		do {
+			csum = csum_add(csum, frags->csum);
+		} while ((frags = frags->next));
 
 		uh->check = csum_ipv6_magic(saddr, daddr, len, IPPROTO_UDP,
 					    csum);
@@ -1023,26 +1024,15 @@ static void udp6_hwcsum_outgoing(struct sock *sk, struct sk_buff *skb,
  *	Sending
  */
 
-static int udp_v6_push_pending_frames(struct sock *sk)
+static int udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6)
 {
-	struct sk_buff *skb;
+	struct sock *sk = skb->sk;
 	struct udphdr *uh;
-	struct udp_sock  *up = udp_sk(sk);
-	struct inet_sock *inet = inet_sk(sk);
-	struct flowi6 *fl6;
 	int err = 0;
 	int is_udplite = IS_UDPLITE(sk);
 	__wsum csum = 0;
-
-	if (up->pending == AF_INET)
-		return udp_push_pending_frames(sk);
-
-	fl6 = &inet->cork.fl.u.ip6;
-
-	/* Grab the skbuff where UDP header space exists. */
-	skb = skb_peek(&sk->sk_write_queue);
-	if (skb == NULL)
-		goto out;
+	int offset = skb_transport_offset(skb);
+	int len = skb->len - offset;
 
 	/*
 	 * Create a UDP header
@@ -1050,29 +1040,28 @@ static int udp_v6_push_pending_frames(struct sock *sk)
 	uh = udp_hdr(skb);
 	uh->source = fl6->fl6_sport;
 	uh->dest = fl6->fl6_dport;
-	uh->len = htons(up->len);
+	uh->len = htons(len);
 	uh->check = 0;
 
 	if (is_udplite)
-		csum = udplite_csum_outgoing(sk, skb);
-	else if (up->no_check6_tx) {   /* UDP csum disabled */
+		csum = udplite_csum(skb);
+	else if (udp_sk(sk)->no_check6_tx) {   /* UDP csum disabled */
 		skb->ip_summed = CHECKSUM_NONE;
 		goto send;
 	} else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */
-		udp6_hwcsum_outgoing(sk, skb, &fl6->saddr, &fl6->daddr,
-				     up->len);
+		udp6_hwcsum_outgoing(sk, skb, &fl6->saddr, &fl6->daddr, len);
 		goto send;
 	} else
-		csum = udp_csum_outgoing(sk, skb);
+		csum = udp_csum(skb);
 
 	/* add protocol-dependent pseudo-header */
 	uh->check = csum_ipv6_magic(&fl6->saddr, &fl6->daddr,
-				    up->len, fl6->flowi6_proto, csum);
+				    len, fl6->flowi6_proto, csum);
 	if (uh->check == 0)
 		uh->check = CSUM_MANGLED_0;
 
 send:
-	err = ip6_push_pending_frames(sk);
+	err = ip6_send_skb(skb);
 	if (err) {
 		if (err == -ENOBUFS && !inet6_sk(sk)->recverr) {
 			UDP6_INC_STATS_USER(sock_net(sk),
@@ -1082,6 +1071,30 @@ static int udp_v6_push_pending_frames(struct sock *sk)
 	} else
 		UDP6_INC_STATS_USER(sock_net(sk),
 				    UDP_MIB_OUTDATAGRAMS, is_udplite);
+	return err;
+}
+
+static int udp_v6_push_pending_frames(struct sock *sk)
+{
+	struct sk_buff *skb;
+	struct udp_sock  *up = udp_sk(sk);
+	struct flowi6 fl6;
+	int err = 0;
+
+	if (up->pending == AF_INET)
+		return udp_push_pending_frames(sk);
+
+	/* ip6_finish_skb will release the cork, so make a copy of
+	 * fl6 here.
+	 */
+	fl6 = inet_sk(sk)->cork.fl.u.ip6;
+
+	skb = ip6_finish_skb(sk);
+	if (!skb)
+		goto out;
+
+	err = udp_v6_send_skb(skb, &fl6);
+
 out:
 	up->len = 0;
 	up->pending = 0;
@@ -1164,6 +1177,7 @@ int udpv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	if (len > INT_MAX - sizeof(struct udphdr))
 		return -EMSGSIZE;
 
+	getfrag  =  is_udplite ?  udplite_getfrag : ip_generic_getfrag;
 	if (up->pending) {
 		/*
 		 * There are pending frames.
@@ -1294,6 +1308,20 @@ int udpv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 		goto do_confirm;
 back_from_confirm:
 
+	/* Lockless fast path for the non-corking case */
+	if (!corkreq) {
+		struct sk_buff *skb;
+
+		skb = ip6_make_skb(sk, getfrag, msg, ulen,
+				   sizeof(struct udphdr), hlimit, tclass, opt,
+				   &fl6, (struct rt6_info *)dst,
+				   msg->msg_flags, dontfrag);
+		err = PTR_ERR(skb);
+		if (!IS_ERR_OR_NULL(skb))
+			err = udp_v6_send_skb(skb, &fl6);
+		goto release_dst;
+	}
+
 	lock_sock(sk);
 	if (unlikely(up->pending)) {
 		/* The socket is already corked while preparing it. */
@@ -1311,7 +1339,6 @@ int udpv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	if (dontfrag < 0)
 		dontfrag = np->dontfrag;
 	up->len += ulen;
-	getfrag  =  is_udplite ?  udplite_getfrag : ip_generic_getfrag;
 	err = ip6_append_data(sk, getfrag, msg, ulen,
 		sizeof(struct udphdr), hlimit, tclass, opt, &fl6,
 		(struct rt6_info *)dst,
@@ -1323,6 +1350,11 @@ int udpv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	else if (unlikely(skb_queue_empty(&sk->sk_write_queue)))
 		up->pending = 0;
 
+	if (err > 0)
+		err = np->recverr ? net_xmit_errno(err) : 0;
+	release_sock(sk);
+
+release_dst:
 	if (dst) {
 		if (connected) {
 			ip6_dst_store(sk, dst,
@@ -1339,9 +1371,6 @@ int udpv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 		dst = NULL;
 	}
 
-	if (err > 0)
-		err = np->recverr ? net_xmit_errno(err) : 0;
-	release_sock(sk);
 out:
 	dst_release(dst);
 	fl6_sock_release(flowlabel);