@@ -1894,12 +1894,15 @@ static inline int skb_clone_writable(const struct sk_buff *skb, unsigned int len
static inline int __skb_cow(struct sk_buff *skb, unsigned int headroom,
int cloned)
{
+ unsigned int alloc_headroom = headroom;
int delta = 0;
if (headroom < NET_SKB_PAD)
- headroom = NET_SKB_PAD;
- if (headroom > skb_headroom(skb))
- delta = headroom - skb_headroom(skb);
+ alloc_headroom = NET_SKB_PAD;
+ if (headroom > skb_headroom(skb) ||
+ (cloned && alloc_headroom > skb_headroom(skb))) {
+ delta = alloc_headroom - skb_headroom(skb);
+ }
if (delta || cloned)
return pskb_expand_head(skb, ALIGN(delta, NET_SKB_PAD), 0,
At the beginning of __skb_cow, headroom gets set to a minimum of NET_SKB_PAD. This causes unnecessary reallocations if the buffer was not cloned and the headroom is just below NET_SKB_PAD, but still more than the amount requested by the caller. This was showing up frequently in my tests on VLAN tx, where vlan_insert_tag calls skb_cow_head(skb, VLAN_HLEN). Fix this by only setting the headroom delta if either there is less headroom than specified by the caller, or if reallocation has to be done anyway because the skb was cloned. Signed-off-by: Felix Fietkau <nbd@openwrt.org> --- include/linux/skbuff.h | 9 ++++++--- 1 files changed, 6 insertions(+), 3 deletions(-)