net: cache skb_shinfo() in skb_try_coalesce()

Compiler does not really know that skb_shinfo(to|from) are constants
in skb_try_coalesce(), lets cache their values to shrink code.

We might even take care of skb_zcopy() calls later.

$ size net/core/skbuff.o.before net/core/skbuff.o
   text	   data	    bss	    dec	    hex	filename
  40727	   1298	      0	  42025	   a429	net/core/skbuff.o.before
  40631	   1298	      0	  41929	   a3c9	net/core/skbuff.o

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

1 files changed, 16 insertions, 13 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index d98c2e3ce2bf..822a90e56aea 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4767,6 +4767,7 @@ EXPORT_SYMBOL(kfree_skb_partial);
 bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
                       bool *fragstolen, int *delta_truesize)
 {
+        struct skb_shared_info *to_shinfo, *from_shinfo;
         int i, delta, len = from->len;
 
         *fragstolen = false;
@@ -4781,7 +4782,9 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
                 return true;
         }
 
-        if (skb_has_frag_list(to) || skb_has_frag_list(from))
+        to_shinfo = skb_shinfo(to);
+        from_shinfo = skb_shinfo(from);
+        if (to_shinfo->frag_list || from_shinfo->frag_list)
                 return false;
         if (skb_zcopy(to) || skb_zcopy(from))
                 return false;
@@ -4790,8 +4793,8 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
                 struct page *page;
                 unsigned int offset;
 
-                if (skb_shinfo(to)->nr_frags +
-                    skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS)
+                if (to_shinfo->nr_frags +
+                    from_shinfo->nr_frags >= MAX_SKB_FRAGS)
                         return false;
 
                 if (skb_head_is_locked(from))
@@ -4802,12 +4805,12 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
                 page = virt_to_head_page(from->head);
                 offset = from->data - (unsigned char *)page_address(page);
 
-                skb_fill_page_desc(to, skb_shinfo(to)->nr_frags,
+                skb_fill_page_desc(to, to_shinfo->nr_frags,
                                    page, offset, skb_headlen(from));
                 *fragstolen = true;
         } else {
-                if (skb_shinfo(to)->nr_frags +
-                    skb_shinfo(from)->nr_frags > MAX_SKB_FRAGS)
+                if (to_shinfo->nr_frags +
+                    from_shinfo->nr_frags > MAX_SKB_FRAGS)
                         return false;
 
                 delta = from->truesize - SKB_TRUESIZE(skb_end_offset(from));
@@ -4815,19 +4818,19 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
 
         WARN_ON_ONCE(delta < len);
 
-        memcpy(skb_shinfo(to)->frags + skb_shinfo(to)->nr_frags,
-               skb_shinfo(from)->frags,
-               skb_shinfo(from)->nr_frags * sizeof(skb_frag_t));
-        skb_shinfo(to)->nr_frags += skb_shinfo(from)->nr_frags;
+        memcpy(to_shinfo->frags + to_shinfo->nr_frags,
+               from_shinfo->frags,
+               from_shinfo->nr_frags * sizeof(skb_frag_t));
+        to_shinfo->nr_frags += from_shinfo->nr_frags;
 
         if (!skb_cloned(from))
-                skb_shinfo(from)->nr_frags = 0;
+                from_shinfo->nr_frags = 0;
 
         /* if the skb is not cloned this does nothing
          * since we set nr_frags to 0.
          */
-        for (i = 0; i < skb_shinfo(from)->nr_frags; i++)
-                skb_frag_ref(from, i);
+        for (i = 0; i < from_shinfo->nr_frags; i++)
+                __skb_frag_ref(&from_shinfo->frags[i]);
 
         to->truesize += delta;
         to->len += len;