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55 lines
2.2 KiB
Diff
55 lines
2.2 KiB
Diff
From: David Woodhouse <dwmw2@infradead.org>
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Date: Thu, 17 Sep 2015 11:19:53 +0100
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Subject: [PATCH] solos-pci: Increase headroom on received packets
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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A comment in include/linux/skbuff.h says that:
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* Various parts of the networking layer expect at least 32 bytes of
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* headroom, you should not reduce this.
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This was demonstrated by a panic when handling fragmented IPv6 packets:
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http://marc.info/?l=linux-netdev&m=144236093519172&w=2
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It's not entirely clear if that comment is still valid — and if it is,
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perhaps netif_rx() ought to be enforcing it with a warning.
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But either way, it is rather stupid from a performance point of view
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for us to be receiving packets into a buffer which doesn't have enough
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room to prepend an Ethernet header — it means that *every* incoming
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packet is going to be need to be reallocated. So let's fix that.
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Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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---
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--- a/drivers/atm/solos-pci.c
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+++ b/drivers/atm/solos-pci.c
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@@ -805,7 +805,12 @@ static void solos_bh(unsigned long card_
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continue;
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}
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- skb = alloc_skb(size + 1, GFP_ATOMIC);
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+ /* Use netdev_alloc_skb() because it adds NET_SKB_PAD of
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+ * headroom, and ensures we can route packets back out an
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+ * Ethernet interface (for example) without having to
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+ * reallocate. Adding NET_IP_ALIGN also ensures that both
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+ * PPPoATM and PPPoEoBR2684 packets end up aligned. */
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+ skb = netdev_alloc_skb_ip_align(NULL, size + 1);
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if (!skb) {
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if (net_ratelimit())
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dev_warn(&card->dev->dev, "Failed to allocate sk_buff for RX\n");
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@@ -869,7 +874,10 @@ static void solos_bh(unsigned long card_
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/* Allocate RX skbs for any ports which need them */
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if (card->using_dma && card->atmdev[port] &&
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!card->rx_skb[port]) {
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- struct sk_buff *skb = alloc_skb(RX_DMA_SIZE, GFP_ATOMIC);
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+ /* Unlike the MMIO case (qv) we can't add NET_IP_ALIGN
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+ * here; the FPGA can only DMA to addresses which are
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+ * aligned to 4 bytes. */
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+ struct sk_buff *skb = dev_alloc_skb(RX_DMA_SIZE);
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if (skb) {
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SKB_CB(skb)->dma_addr =
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dma_map_single(&card->dev->dev, skb->data,
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