net: makes skb_splice_bits() aware of skb->head_frag

__skb_splice_bits() can check if skb to be spliced has its skb->head mapped to a page fragment, instead of a kmalloc() area. If so we can avoid a copy of the skb head and get a reference on underlying page. Signed-off-by: Eric Dumazet <[email protected]> Cc: Ilpo Järvinen <[email protected]> Cc: Herbert Xu <[email protected]> Cc: Maciej Żenczykowski <[email protected]> Cc: Neal Cardwell <[email protected]> Cc: Tom Herbert <[email protected]> Cc: Jeff Kirsher <[email protected]> Cc: Ben Hutchings <[email protected]> Cc: Matt Carlson <[email protected]> Cc: Michael Chan <[email protected]> Signed-off-by: David S. Miller <[email protected]>
mrcsosa · May 1, 2012 · 1d0c0b3 · 1d0c0b3
1 parent 329033f
commit 1d0c0b3
Showing 1 changed file with 7 additions and 3 deletions.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
@@ -1699,14 +1699,18 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
 			      struct splice_pipe_desc *spd, struct sock *sk)
 {
 	int seg;
+	bool head_is_linear = !skb->head_frag;
 
-	/*
-	 * map the linear part
+	/* map the linear part :
+	 * If skb->head_frag is set, this 'linear' part is backed
+	 * by a fragment, and we can avoid a copy.
 	 */
 	if (__splice_segment(virt_to_page(skb->data),
 			     (unsigned long) skb->data & (PAGE_SIZE - 1),
 			     skb_headlen(skb),
-			     offset, len, skb, spd, true, sk, pipe))
+			     offset, len, skb, spd,
+			     head_is_linear,
+			     sk, pipe))
 		return true;
 
 	/*