From: Eric Dumazet <edumazet@google.com>
Date: Sat, 30 Apr 2016 17:19:29 +0000 (-0700)
Subject: net: relax expensive skb_unclone() in iptunnel_handle_offloads()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=9580bf2edb402b3afaf9c5a4efb6953f993ef52e;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

net: relax expensive skb_unclone() in iptunnel_handle_offloads()

Locally generated TCP GSO packets having to go through a GRE/SIT/IPIP
tunnel have to go through an expensive skb_unclone()

Reallocating skb->head is a lot of work.

Test should really check if a 'real clone' of the packet was done.

TCP does not care if the original gso_type is changed while the packet
travels in the stack.

This adds skb_header_unclone() which is a variant of skb_clone()
using skb_header_cloned() check instead of skb_cloned().

This variant can probably be used from other points.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c84a5a1078c5..c413c588a24f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1325,6 +1325,16 @@ static inline int skb_header_cloned(const struct sk_buff *skb)
 	return dataref != 1;
 }
 
+static inline int skb_header_unclone(struct sk_buff *skb, gfp_t pri)
+{
+	might_sleep_if(gfpflags_allow_blocking(pri));
+
+	if (skb_header_cloned(skb))
+		return pskb_expand_head(skb, 0, 0, pri);
+
+	return 0;
+}
+
 /**
  *	skb_header_release - release reference to header
  *	@skb: buffer to operate on
diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c
index 786fa7ca28e0..9118b0e640ba 100644
--- a/net/ipv4/ip_tunnel_core.c
+++ b/net/ipv4/ip_tunnel_core.c
@@ -157,7 +157,7 @@ int iptunnel_handle_offloads(struct sk_buff *skb,
 	}
 
 	if (skb_is_gso(skb)) {
-		err = skb_unclone(skb, GFP_ATOMIC);
+		err = skb_header_unclone(skb, GFP_ATOMIC);
 		if (unlikely(err))
 			return err;
 		skb_shinfo(skb)->gso_type |= gso_type_mask;