skbuff: add an api to orphan frags

commit a353e0ce0fd42d8859260666d1e9b10f2abd4698 upstream.

Many places do
       if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY))
		skb_copy_ubufs(skb, gfp_mask);
to copy and invoke frag destructors if necessary.
Add an inline helper for this.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c445e52..40c2726 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1632,6 +1632,22 @@ static inline void skb_orphan(struct sk_buff *skb)
        skb->sk         = NULL;
 }
 
+/**
+ *     skb_orphan_frags - orphan the frags contained in a buffer
+ *     @skb: buffer to orphan frags from
+ *     @gfp_mask: allocation mask for replacement pages
+ *
+ *     For each frag in the SKB which needs a destructor (i.e. has an
+ *     owner) create a copy of that frag and release the original
+ *     page by calling the destructor.
+ */
+static inline int skb_orphan_frags(struct sk_buff *skb, gfp_t gfp_mask)
+{
+       if (likely(!(skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY)))
+               return 0;
+       return skb_copy_ubufs(skb, gfp_mask);
+}
+
 /**
  *     __skb_queue_purge - empty a list
  *     @list: list to empty