diff mbox

[net-next,02/21] udp: call dst_hold_safe() in udp_sk_rx_set_dst()

Message ID 20170616174744.139688-3-tracywwnj@gmail.com
State Changes Requested, archived
Delegated to: David Miller
Headers show

Commit Message

Wei Wang June 16, 2017, 5:47 p.m. UTC 
From: Wei Wang <weiwan@google.com>

In udp_v4/6_early_demux() code, we try to hold dst->__refcnt for
dst with DST_NOCACHE flag. This is because later in udp_sk_rx_dst_set()
function, we will try to cache this dst in sk for connected case.
However, a better way to achieve this is to not try to hold dst in
early_demux(), but in udp_sk_rx_dst_set(), call dst_hold_safe(). This
approach is also more consistant with how tcp is handling it. And it
will make later changes simpler.

Signed-off-by: Wei Wang <weiwan@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
---
 net/ipv4/udp.c | 22 ++++++++++------------
 net/ipv6/udp.c | 14 ++++++--------
 2 files changed, 16 insertions(+), 20 deletions(-)

Comments

David Miller June 16, 2017, 7:02 p.m. UTC | #1 
From: Wei Wang <tracywwnj@gmail.com>
Date: Fri, 16 Jun 2017 10:47:25 -0700

> +	if (dst)
> +		/* set noref for now.
> +		 * any place which wants to hold dst has to call
> +		 * dst_hold_safe()
> +		 */
> +		skb_dst_set_noref(skb, dst);

You must enclose the code in curly braces if you want to put a comment
in this one-line basic block of the 'if' statement.

Otherwise it's hard to read.

Likewise for the other similar change in this file.

THanks.
Wei Wang June 16, 2017, 7:06 p.m. UTC | #2 
On Fri, Jun 16, 2017 at 12:02 PM, David Miller <davem@davemloft.net> wrote:
> From: Wei Wang <tracywwnj@gmail.com>
> Date: Fri, 16 Jun 2017 10:47:25 -0700
>
>> +     if (dst)
>> +             /* set noref for now.
>> +              * any place which wants to hold dst has to call
>> +              * dst_hold_safe()
>> +              */
>> +             skb_dst_set_noref(skb, dst);
>
> You must enclose the code in curly braces if you want to put a comment
> in this one-line basic block of the 'if' statement.
>
> Otherwise it's hard to read.
>
> Likewise for the other similar change in this file.
>

Got it. Will update in the next version.
diff mbox

Patch

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 2bc638c48b86..99fb1fb90ad3 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1977,9 +1977,10 @@  static void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
 {
 	struct dst_entry *old;
 
-	dst_hold(dst);
-	old = xchg(&sk->sk_rx_dst, dst);
-	dst_release(old);
+	if (dst_hold_safe(dst)) {
+		old = xchg(&sk->sk_rx_dst, dst);
+		dst_release(old);
+	}
 }
 
 /*
@@ -2302,15 +2303,12 @@  void udp_v4_early_demux(struct sk_buff *skb)
 
 	if (dst)
 		dst = dst_check(dst, 0);
-	if (dst) {
-		/* DST_NOCACHE can not be used without taking a reference */
-		if (dst->flags & DST_NOCACHE) {
-			if (likely(atomic_inc_not_zero(&dst->__refcnt)))
-				skb_dst_set(skb, dst);
-		} else {
-			skb_dst_set_noref(skb, dst);
-		}
-	}
+	if (dst)
+		/* set noref for now.
+		 * any place which wants to hold dst has to call
+		 * dst_hold_safe()
+		 */
+		skb_dst_set_noref(skb, dst);
 }
 
 int udp_rcv(struct sk_buff *skb)
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 2e9b52bded2d..a2152e2138ff 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -919,14 +919,12 @@  static void udp_v6_early_demux(struct sk_buff *skb)
 
 	if (dst)
 		dst = dst_check(dst, inet6_sk(sk)->rx_dst_cookie);
-	if (dst) {
-		if (dst->flags & DST_NOCACHE) {
-			if (likely(atomic_inc_not_zero(&dst->__refcnt)))
-				skb_dst_set(skb, dst);
-		} else {
-			skb_dst_set_noref(skb, dst);
-		}
-	}
+	if (dst)
+		/* set noref for now.
+		 * any place which wants to hold dst has to call
+		 * dst_hold_safe()
+		 */
+		skb_dst_set_noref(skb, dst);
 }
 
 static __inline__ int udpv6_rcv(struct sk_buff *skb)