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Commit f2707015 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

ax88179_178a: avoid copy of tx tcp packets 



ax88179_tx_fixup() has quite complex code trying to push 8 bytes
of control data (len/mss), but fails to do it properly for TCP packets,
incurring an extra copy and point of memory allocation failure.

Lets use the simple and approved way.

dev->needed_headroom being 8, all frames should have 8 bytes of
headroom, so the extra copy should be unlikely anyway.

This patch should improve performance for TCP xmits.

Reported-by: default avatarMing Lei <ming.lei@canonical.com>
Tested-by: default avatarMing Lei <ming.lei@canonical.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0e76a3a5

drivers/net/usb/ax88179_178a.c

+4 −17
Original line number Diff line number Diff line
@@ -1169,30 +1169,17 @@ ax88179_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags) 
	int frame_size = dev->maxpacket;

	int mss = skb_shinfo(skb)->gso_size;

	int headroom;

	int tailroom;



	tx_hdr1 = skb->len;

	tx_hdr2 = mss;

	if (((skb->len + 8) % frame_size) == 0)

		tx_hdr2 |= 0x80008000;	/* Enable padding */



	headroom = skb_headroom(skb);

	tailroom = skb_tailroom(skb);

	headroom = skb_headroom(skb) - 8;



	if (!skb_header_cloned(skb) &&

	    !skb_cloned(skb) &&

	    (headroom + tailroom) >= 8) {

		if (headroom < 8) {

			skb->data = memmove(skb->head + 8, skb->data, skb->len);

			skb_set_tail_pointer(skb, skb->len);

		}

	} else {

		struct sk_buff *skb2;



		skb2 = skb_copy_expand(skb, 8, 0, flags);

	if ((skb_header_cloned(skb) || headroom < 0) &&

	    pskb_expand_head(skb, headroom < 0 ? 8 : 0, 0, GFP_ATOMIC)) {

		dev_kfree_skb_any(skb);

		skb = skb2;

		if (!skb)

		return NULL;

	}