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Commit ce816eb0 authored by David Woodhouse's avatar David Woodhouse Committed by David S. Miller
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solos-pci: Increase headroom on received packets 

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: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 88c79664

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,