net: Convert GRO SKB handling to list_head.

Manage pending per-NAPI GRO packets via list_head.

Return an SKB pointer from the GRO receive handlers.  When GRO receive
handlers return non-NULL, it means that this SKB needs to be completed
at this time and removed from the NAPI queue.

Several operations are greatly simplified by this transformation,
especially timing out the oldest SKB in the list when gro_count
exceeds MAX_GRO_SKBS, and napi_gro_flush() which walks the queue
in reverse order.

Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 36 insertions, 35 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 15e125558c76..06b218a2870f 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1384,12 +1384,12 @@ out:
 }
 EXPORT_SYMBOL(inet_gso_segment);
 
-struct sk_buff **inet_gro_receive(struct sk_buff **head, struct sk_buff *skb)
+struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb)
 {
 	const struct net_offload *ops;
-	struct sk_buff **pp = NULL;
-	struct sk_buff *p;
+	struct sk_buff *pp = NULL;
 	const struct iphdr *iph;
+	struct sk_buff *p;
 	unsigned int hlen;
 	unsigned int off;
 	unsigned int id;
@@ -1425,7 +1425,7 @@ struct sk_buff **inet_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 	flush = (u16)((ntohl(*(__be32 *)iph) ^ skb_gro_len(skb)) | (id & ~IP_DF));
 	id >>= 16;
 
-	for (p = *head; p; p = p->next) {
+	list_for_each_entry(p, head, list) {
 		struct iphdr *iph2;
 		u16 flush_id;
 
@@ -1505,8 +1505,8 @@ out:
 }
 EXPORT_SYMBOL(inet_gro_receive);
 
-static struct sk_buff **ipip_gro_receive(struct sk_buff **head,
-					 struct sk_buff *skb)
+static struct sk_buff *ipip_gro_receive(struct list_head *head,
+					struct sk_buff *skb)
 {
 	if (NAPI_GRO_CB(skb)->encap_mark) {
 		NAPI_GRO_CB(skb)->flush = 1;
diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
index 7cf755ef9efb..bbeecd13e534 100644
--- a/net/ipv4/esp4_offload.c
+++ b/net/ipv4/esp4_offload.c
@@ -28,8 +28,8 @@
 #include <linux/spinlock.h>
 #include <net/udp.h>
 
-static struct sk_buff **esp4_gro_receive(struct sk_buff **head,
-					 struct sk_buff *skb)
+static struct sk_buff *esp4_gro_receive(struct list_head *head,
+					struct sk_buff *skb)
 {
 	int offset = skb_gro_offset(skb);
 	struct xfrm_offload *xo;
diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 1540db65241a..efdc9e1f741e 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -224,14 +224,14 @@ drop:
 	return 0;
 }
 
-static struct sk_buff **fou_gro_receive(struct sock *sk,
-					struct sk_buff **head,
-					struct sk_buff *skb)
+static struct sk_buff *fou_gro_receive(struct sock *sk,
+				       struct list_head *head,
+				       struct sk_buff *skb)
 {
-	const struct net_offload *ops;
-	struct sk_buff **pp = NULL;
 	u8 proto = fou_from_sock(sk)->protocol;
 	const struct net_offload **offloads;
+	const struct net_offload *ops;
+	struct sk_buff *pp = NULL;
 
 	/* We can clear the encap_mark for FOU as we are essentially doing
 	 * one of two possible things.  We are either adding an L4 tunnel
@@ -305,13 +305,13 @@ static struct guehdr *gue_gro_remcsum(struct sk_buff *skb, unsigned int off,
 	return guehdr;
 }
 
-static struct sk_buff **gue_gro_receive(struct sock *sk,
-					struct sk_buff **head,
-					struct sk_buff *skb)
+static struct sk_buff *gue_gro_receive(struct sock *sk,
+				       struct list_head *head,
+				       struct sk_buff *skb)
 {
 	const struct net_offload **offloads;
 	const struct net_offload *ops;
-	struct sk_buff **pp = NULL;
+	struct sk_buff *pp = NULL;
 	struct sk_buff *p;
 	struct guehdr *guehdr;
 	size_t len, optlen, hdrlen, off;
@@ -397,7 +397,7 @@ static struct sk_buff **gue_gro_receive(struct sock *sk,
 
 	skb_gro_pull(skb, hdrlen);
 
-	for (p = *head; p; p = p->next) {
+	list_for_each_entry(p, head, list) {
 		const struct guehdr *guehdr2;
 
 		if (!NAPI_GRO_CB(p)->same_flow)
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 1859c473b21a..b9673c21be45 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -108,10 +108,10 @@ out:
 	return segs;
 }
 
-static struct sk_buff **gre_gro_receive(struct sk_buff **head,
-					struct sk_buff *skb)
+static struct sk_buff *gre_gro_receive(struct list_head *head,
+				       struct sk_buff *skb)
 {
-	struct sk_buff **pp = NULL;
+	struct sk_buff *pp = NULL;
 	struct sk_buff *p;
 	const struct gre_base_hdr *greh;
 	unsigned int hlen, grehlen;
@@ -182,7 +182,7 @@ static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 					     null_compute_pseudo);
 	}
 
-	for (p = *head; p; p = p->next) {
+	list_for_each_entry(p, head, list) {
 		const struct gre_base_hdr *greh2;
 
 		if (!NAPI_GRO_CB(p)->same_flow)
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 8cc7c3487330..f5aee641f825 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -180,9 +180,9 @@ out:
 	return segs;
 }
 
-struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
+struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
 {
-	struct sk_buff **pp = NULL;
+	struct sk_buff *pp = NULL;
 	struct sk_buff *p;
 	struct tcphdr *th;
 	struct tcphdr *th2;
@@ -220,7 +220,7 @@ struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 	len = skb_gro_len(skb);
 	flags = tcp_flag_word(th);
 
-	for (; (p = *head); head = &p->next) {
+	list_for_each_entry(p, head, list) {
 		if (!NAPI_GRO_CB(p)->same_flow)
 			continue;
 
@@ -233,7 +233,7 @@ struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 
 		goto found;
 	}
-
+	p = NULL;
 	goto out_check_final;
 
 found:
@@ -263,7 +263,7 @@ found:
 	flush |= (len - 1) >= mss;
 	flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
 
-	if (flush || skb_gro_receive(head, skb)) {
+	if (flush || skb_gro_receive(p, skb)) {
 		mss = 1;
 		goto out_check_final;
 	}
@@ -277,7 +277,7 @@ out_check_final:
 					TCP_FLAG_FIN));
 
 	if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
-		pp = head;
+		pp = p;
 
 out:
 	NAPI_GRO_CB(skb)->flush |= (flush != 0);
@@ -302,7 +302,7 @@ int tcp_gro_complete(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(tcp_gro_complete);
 
-static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
+static struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
 {
 	/* Don't bother verifying checksum if we're going to flush anyway. */
 	if (!NAPI_GRO_CB(skb)->flush &&
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 92dc9e5a7ff3..ac46c1c55c99 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -343,10 +343,11 @@ out:
 	return segs;
 }
 
-struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
-				 struct udphdr *uh, udp_lookup_t lookup)
+struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
+				struct udphdr *uh, udp_lookup_t lookup)
 {
-	struct sk_buff *p, **pp = NULL;
+	struct sk_buff *pp = NULL;
+	struct sk_buff *p;
 	struct udphdr *uh2;
 	unsigned int off = skb_gro_offset(skb);
 	int flush = 1;
@@ -371,7 +372,7 @@ struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
 unflush:
 	flush = 0;
 
-	for (p = *head; p; p = p->next) {
+	list_for_each_entry(p, head, list) {
 		if (!NAPI_GRO_CB(p)->same_flow)
 			continue;
 
@@ -399,8 +400,8 @@ out:
 }
 EXPORT_SYMBOL(udp_gro_receive);
 
-static struct sk_buff **udp4_gro_receive(struct sk_buff **head,
-					 struct sk_buff *skb)
+static struct sk_buff *udp4_gro_receive(struct list_head *head,
+					struct sk_buff *skb)
 {
 	struct udphdr *uh = udp_gro_udphdr(skb);