Thread (10 messages) 10 messages, 3 authors, 2019-02-13

Re: [PATCH RFC v2 1/3] UDP: enable GRO by default.

From: Paolo Abeni <pabeni@redhat.com>
Date: 2019-01-28 15:30:19

Hi,

On Mon, 2019-01-28 at 09:50 +0100, Steffen Klassert wrote:
quoted hunk ↗ jump to hunk
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 64f9715173ac..584635db9231 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -392,35 +392,24 @@ static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
 	return NULL;
 }
 
-INDIRECT_CALLABLE_DECLARE(struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
-						   __be16 sport, __be16 dport));
 struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
-				struct udphdr *uh, udp_lookup_t lookup)
+				struct udphdr *uh, struct sock *sk)
 {
 	struct sk_buff *pp = NULL;
 	struct sk_buff *p;
 	struct udphdr *uh2;
 	unsigned int off = skb_gro_offset(skb);
 	int flush = 1;
-	struct sock *sk;
-
-	rcu_read_lock();
-	sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
-				udp4_lib_lookup_skb, skb, uh->source, uh->dest);
-	if (!sk)
-		goto out_unlock;
 
-	if (udp_sk(sk)->gro_enabled) {
+	if (!sk || !udp_sk(sk)->gro_receive) {
 		pp = call_gro_receive(udp_gro_receive_segment, head, skb);
-		rcu_read_unlock();
 		return pp;
 	}
 
 	if (NAPI_GRO_CB(skb)->encap_mark ||
 	    (skb->ip_summed != CHECKSUM_PARTIAL &&
 	     NAPI_GRO_CB(skb)->csum_cnt == 0 &&
-	     !NAPI_GRO_CB(skb)->csum_valid) ||
-	    !udp_sk(sk)->gro_receive)
+	     !NAPI_GRO_CB(skb)->csum_valid))
 		goto out_unlock;
Here I think an additional chunk is missing: the caller is holding the
rcu lock, we should drop the rcu_read_unlock() from this function (and
likely rename the associated label).
 
quoted hunk ↗ jump to hunk
 	/* mark that this skb passed once through the tunnel gro layer */
@@ -459,8 +448,10 @@ INDIRECT_CALLABLE_SCOPE
 struct sk_buff *udp4_gro_receive(struct list_head *head, struct sk_buff *skb)
 {
 	struct udphdr *uh = udp_gro_udphdr(skb);
+	struct sk_buff *pp;
+	struct sock *sk;
 
-	if (unlikely(!uh) || !static_branch_unlikely(&udp_encap_needed_key))
+	if (unlikely(!uh))
 		goto flush;
 
 	/* Don't bother verifying checksum if we're going to flush anyway. */
@@ -475,7 +466,11 @@ struct sk_buff *udp4_gro_receive(struct list_head *head, struct sk_buff *skb)
 					     inet_gro_compute_pseudo);
 skip:
 	NAPI_GRO_CB(skb)->is_ipv6 = 0;
-	return udp_gro_receive(head, skb, uh, udp4_lib_lookup_skb);
+	rcu_read_lock();
+	sk = static_branch_unlikely(&udp_encap_needed_key) ? udp4_lib_lookup_skb(skb, uh->source, uh->dest) : NULL;
+	pp = udp_gro_receive(head, skb, uh, sk);
+	rcu_read_unlock();
+	return pp;
 
 flush:
 	NAPI_GRO_CB(skb)->flush = 1;
_Unrelated_ to this patch, but IIRC the RCU lock is already help by
dev_gro_receive(), so IMHO a follow-up patch could possibly remove the
lock here and make the code smaller. 

Apart from first point above, I like this patch a lot!

Paolo
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