tcp: optimize some skb_shinfo(skb) uses

Compiler doesn't know skb_shinfo(skb) pointer is usually constant.

By using a temporary variable, we help generating smaller code.

For example, tcp_init_nondata_skb() is inlined after this patch.

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

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 7820f3a..993da00 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -363,15 +363,17 @@ static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
  */
 static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
 {
+       struct skb_shared_info *shinfo = skb_shinfo(skb);
+
        skb->ip_summed = CHECKSUM_PARTIAL;
        skb->csum = 0;
 
        TCP_SKB_CB(skb)->tcp_flags = flags;
        TCP_SKB_CB(skb)->sacked = 0;
 
-       skb_shinfo(skb)->gso_segs = 1;
-       skb_shinfo(skb)->gso_size = 0;
-       skb_shinfo(skb)->gso_type = 0;
+       shinfo->gso_segs = 1;
+       shinfo->gso_size = 0;
+       shinfo->gso_type = 0;
 
        TCP_SKB_CB(skb)->seq = seq;
        if (flags & (TCPHDR_SYN | TCPHDR_FIN))
@@ -986,6 +988,8 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
 static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
                                 unsigned int mss_now)
 {
+       struct skb_shared_info *shinfo = skb_shinfo(skb);
+
        /* Make sure we own this skb before messing gso_size/gso_segs */
        WARN_ON_ONCE(skb_cloned(skb));
 
@@ -993,13 +997,13 @@ static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
                /* Avoid the costly divide in the normal
                 * non-TSO case.
                 */
-               skb_shinfo(skb)->gso_segs = 1;
-               skb_shinfo(skb)->gso_size = 0;
-               skb_shinfo(skb)->gso_type = 0;
+               shinfo->gso_segs = 1;
+               shinfo->gso_size = 0;
+               shinfo->gso_type = 0;
        } else {
-               skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
-               skb_shinfo(skb)->gso_size = mss_now;
-               skb_shinfo(skb)->gso_type = sk->sk_gso_type;
+               shinfo->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
+               shinfo->gso_size = mss_now;
+               shinfo->gso_type = sk->sk_gso_type;
        }
 }
 
@@ -1146,6 +1150,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
  */
 static void __pskb_trim_head(struct sk_buff *skb, int len)
 {
+       struct skb_shared_info *shinfo;
        int i, k, eat;
 
        eat = min_t(int, len, skb_headlen(skb));
@@ -1157,23 +1162,24 @@ static void __pskb_trim_head(struct sk_buff *skb, int len)
        }
        eat = len;
        k = 0;
-       for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
-               int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
+       shinfo = skb_shinfo(skb);
+       for (i = 0; i < shinfo->nr_frags; i++) {
+               int size = skb_frag_size(&shinfo->frags[i]);
 
                if (size <= eat) {
                        skb_frag_unref(skb, i);
                        eat -= size;
                } else {
-                       skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
+                       shinfo->frags[k] = shinfo->frags[i];
                        if (eat) {
-                               skb_shinfo(skb)->frags[k].page_offset += eat;
-                               skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat);
+                               shinfo->frags[k].page_offset += eat;
+                               skb_frag_size_sub(&shinfo->frags[k], eat);
                                eat = 0;
                        }
                        k++;
                }
        }
-       skb_shinfo(skb)->nr_frags = k;
+       shinfo->nr_frags = k;
 
        skb_reset_tail_pointer(skb);
        skb->data_len -= len;