From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH net 6/6] kaweth: use skb_cow_head() to deal with cloned skbs Date: Wed, 19 Apr 2017 09:59:26 -0700 Message-ID: <20170419165926.30631-7-edumazet@google.com> References: <20170419165926.30631-1-edumazet@google.com> Cc: netdev , James Hughes , Eric Dumazet , Eric Dumazet To: "David S . Miller" Return-path: Received: from mail-yb0-f174.google.com ([209.85.213.174]:33742 "EHLO mail-yb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967313AbdDSRCI (ORCPT ); Wed, 19 Apr 2017 13:02:08 -0400 Received: by mail-yb0-f174.google.com with SMTP id 81so8939783ybp.0 for ; Wed, 19 Apr 2017 10:02:08 -0700 (PDT) In-Reply-To: <20170419165926.30631-1-edumazet@google.com> Sender: netdev-owner@vger.kernel.org List-ID: We can use skb_cow_head() to properly deal with clones, especially the ones coming from TCP stack that allow their head being modified. This avoids a copy. Signed-off-by: Eric Dumazet Cc: James Hughes --- drivers/net/usb/kaweth.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/drivers/net/usb/kaweth.c b/drivers/net/usb/kaweth.c index 876f02f4945eafdc2fb5cfa0f9dcb54d9b498af4..2a2c3edb6bad0b3bd257c3a101d100ad3b00cc59 100644 --- a/drivers/net/usb/kaweth.c +++ b/drivers/net/usb/kaweth.c @@ -803,18 +803,12 @@ static netdev_tx_t kaweth_start_xmit(struct sk_buff *skb, } /* We now decide whether we can put our special header into the sk_buff */ - if (skb_cloned(skb) || skb_headroom(skb) < 2) { - /* no such luck - we make our own */ - struct sk_buff *copied_skb; - copied_skb = skb_copy_expand(skb, 2, 0, GFP_ATOMIC); - dev_kfree_skb_irq(skb); - skb = copied_skb; - if (!copied_skb) { - kaweth->stats.tx_errors++; - netif_start_queue(net); - spin_unlock_irq(&kaweth->device_lock); - return NETDEV_TX_OK; - } + if (skb_cow_head(skb, 2)) { + kaweth->stats.tx_errors++; + netif_start_queue(net); + spin_unlock_irq(&kaweth->device_lock); + dev_kfree_skb_any(skb); + return NETDEV_TX_OK; } private_header = (__le16 *)__skb_push(skb, 2); -- 2.12.2.816.g2cccc81164-goog