[PATCH] xen-netback: use local var in xenvif_tx_check_gop() instead of re-calculating

[Jan Beulich <jbeulich@xxxxxxxx>]

shinfo already holds the result of skb_shinfo(skb) at this point - no
need to re-invoke the construct even twice.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -557,8 +557,8 @@ check_frags:
        }
 
        if (skb_has_frag_list(skb) && !first_shinfo) {
-               first_shinfo = skb_shinfo(skb);
-               shinfo = skb_shinfo(skb_shinfo(skb)->frag_list);
+               first_shinfo = shinfo;
+               shinfo = skb_shinfo(shinfo->frag_list);
                nr_frags = shinfo->nr_frags;
 
                goto check_frags;