datapath: use skb_list_walk_safe helper for gso segments

Upstream commit:
    commit 2cec4448db38758832c2edad439f99584bb8fa0d
    Author: Jason A. Donenfeld <Jason@zx2c4.com>
    Date:   Mon Jan 13 18:42:29 2020 -0500

    net: openvswitch: use skb_list_walk_safe helper for gso segments

    This is a straight-forward conversion case for the new function, keeping
    the flow of the existing code as intact as possible.

    Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Acked-by: Yi-Hung Wei <yihung.wei@gmail.com>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

datapath/datapath.c

@@ -343,8 +343,7 @@ static int queue_gso_packets(struct datapath *dp, struct sk_buff *skb,
 	}
 #endif
 	/* Queue all of the segments. */
-	skb = segs;
-	do {
+	skb_list_walk_safe(segs, skb, nskb) {
 		*OVS_CB(skb) = ovs_cb;
 #ifdef HAVE_SKB_GSO_UDP
 		if (gso_type & SKB_GSO_UDP && skb != segs)
@@ -354,17 +353,15 @@ static int queue_gso_packets(struct datapath *dp, struct sk_buff *skb,
 		if (err)
 			break;
 
-	} while ((skb = skb->next));
+	}
 
 	/* Free all of the segments. */
-	skb = segs;
-	do {
-		nskb = skb->next;
+	skb_list_walk_safe(segs, skb, nskb) {
 		if (err)
 			kfree_skb(skb);
 		else
 			consume_skb(skb);
-	} while ((skb = nskb));
+	}
 	return err;
 }
 

datapath/linux/compat/include/linux/skbuff.h

@@ -487,4 +487,11 @@ static inline __u32 skb_get_hash_raw(const struct sk_buff *skb)
 }
 #endif
 
+#ifndef skb_list_walk_safe
+/* Iterate through singly-linked GSO fragments of an skb. */
+#define skb_list_walk_safe(first, skb, next_skb)                               \
+	for ((skb) = (first), (next_skb) = (skb) ? (skb)->next : NULL; (skb);  \
+	     (skb) = (next_skb), (next_skb) = (skb) ? (skb)->next : NULL)
+#endif
+
 #endif