solos-pci: Increase headroom on received packets (ce816eb0) · Commits · 戴 / test

A comment in include/linux/skbuff.h says that: * Various parts of the networking layer expect at least 32 bytes of * headroom, you should not reduce this. This was demonstrated by a panic when handling fragmented IPv6 packets: http://marc.info/?l=linux-netdev&m=144236093519172&w=2 It's not entirely clear if that comment is still valid — and if it is, perhaps netif_rx() ought to be enforcing it with a warning. But either way, it is rather stupid from a performance point of view for us to be receiving packets into a buffer which doesn't have enough room to prepend an Ethernet header — it means that *every* incoming packet is going to be need to be reallocated. So let's fix that. Signed-off-by:

David Woodhouse <David.Woodhouse@intel.com> Acked-by:

Eric Dumazet <edumazet@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/atm/solos-pci.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -805,7 +805,12 @@ static void solos_bh(unsigned long card_arg)
		continue;
		}

		skb = alloc_skb(size + 1, GFP_ATOMIC);
		/* Use netdev_alloc_skb() because it adds NET_SKB_PAD of
		* headroom, and ensures we can route packets back out an
		* Ethernet interface (for example) without having to
		* reallocate. Adding NET_IP_ALIGN also ensures that both
		* PPPoATM and PPPoEoBR2684 packets end up aligned. */
		skb = netdev_alloc_skb_ip_align(NULL, size + 1);
		if (!skb) {
		if (net_ratelimit())
		dev_warn(&card->dev->dev, "Failed to allocate sk_buff for RX\n");
		@@ -869,7 +874,10 @@ static void solos_bh(unsigned long card_arg)
		/* Allocate RX skbs for any ports which need them */
		if (card->using_dma && card->atmdev[port] &&
		!card->rx_skb[port]) {
		struct sk_buff *skb = alloc_skb(RX_DMA_SIZE, GFP_ATOMIC);
		/* Unlike the MMIO case (qv) we can't add NET_IP_ALIGN
		* here; the FPGA can only DMA to addresses which are
		* aligned to 4 bytes. */
		struct sk_buff *skb = dev_alloc_skb(RX_DMA_SIZE);
		if (skb) {
		SKB_CB(skb)->dma_addr =
		dma_map_single(&card->dev->dev, skb->data,

Admin message