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authorAlexander Duyck <alexander.h.duyck@intel.com>2012-05-02 18:18:42 +0000
committerDavid S. Miller <davem@davemloft.net>2012-05-03 01:34:37 -0400
commit2996d31f9f292cce67cd9105dc0a4a5ee43d2f14 (patch)
tree4368e35e13d083a40530c88de554de8d88c0aa41 /net/core/skbuff.c
parentb081f85c2977b1cbb6e635d53d9512f1ef985972 (diff)
downloadlwn-2996d31f9f292cce67cd9105dc0a4a5ee43d2f14.tar.gz
lwn-2996d31f9f292cce67cd9105dc0a4a5ee43d2f14.zip
net: Stop decapitating clones that have a head_frag
This change is meant ot prevent stealing the skb->head to use as a page in the event that the skb->head was cloned. This allows the other clones to track each other via shinfo->dataref. Without this we break down to two methods for tracking the reference count, one being dataref, the other being the page count. As a result it becomes difficult to track how many references there are to skb->head. Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com> Cc: Eric Dumazet <edumazet@google.com> Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/skbuff.c')
-rw-r--r--net/core/skbuff.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 52ba2b5e803d..9e8caa0c4f72 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1699,17 +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;
+ bool head_is_locked = !skb->head_frag || skb_cloned(skb);
/* 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 skb->head_frag is set, this 'linear' part is backed by a
+ * fragment, and if the head is not shared with any clones then
+ * we can avoid a copy since we own the head portion of this page.
*/
if (__splice_segment(virt_to_page(skb->data),
(unsigned long) skb->data & (PAGE_SIZE - 1),
skb_headlen(skb),
offset, len, skb, spd,
- head_is_linear,
+ head_is_locked,
sk, pipe))
return true;