udpv6: Add lockless sendmsg() support

This commit adds the same functionaliy to IPv6 that
commit 903ab86d195cca295379699299c5fc10beba31c7
Author: Herbert Xu <herbert@gondor.apana.org.au>
Date:   Tue Mar 1 02:36:48 2011 +0000

    udp: Add lockless transmit path

added to IPv4.

UDP transmit path can now run without a socket lock,
thus allowing multiple threads to send to a single socket
more efficiently.
This is only used when corking/MSG_MORE is not used.

Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 67a3d70f7ac48d8c881cad7f1663e43822aad618..d048d46779fc55407e9c45d123d6ba7dd6858782 100644 (file)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1177,6 +1177,7 @@ do_udp_sendmsg:
        if (len > INT_MAX - sizeof(struct udphdr))
                return -EMSGSIZE;
 
+       getfrag  =  is_udplite ?  udplite_getfrag : ip_generic_getfrag;
        if (up->pending) {
                /*
                 * There are pending frames.
@@ -1307,6 +1308,20 @@ do_udp_sendmsg:
                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. */
@@ -1324,7 +1339,6 @@ do_append_data:
        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,
@@ -1336,6 +1350,11 @@ do_append_data:
        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,
@@ -1352,9 +1371,6 @@ do_append_data:
                dst = NULL;
        }
 
-       if (err > 0)
-               err = np->recverr ? net_xmit_errno(err) : 0;
-       release_sock(sk);
 out:
        dst_release(dst);
        fl6_sock_release(flowlabel);