On Fri, Sep 22, 2006 at 10:33:48PM -0700, Andrew Morton ([email protected]) wrote:
> > The NET_IP_ALIGN existed not just for fun :) There are ramifications
> > for removing it.
>
> It's still there, isn't it?
>
> For the 9k MTU case, for example, we end up allocating 16384 byte skbs
> instead of 32786 kbytes ones.
This patch will not help - netdev_alloc_skb() adds additional
NET_SKB_PAD and then alloc_skb() adds sizeof(struct skb_shared_info).
And even if you acconut for them in adapter->rx_buf_len, chip still can
overwrite that area (in the thread mentioned in this e-mail thread
before I posted such patch and received a dump of sizes chip receives -
there were a lot of _different_ ones which were too close to the limit).
>
> diff -puN drivers/net/e1000/e1000_main.c~e1000-account-for-net_ip_align-when-calculating-bufsiz drivers/net/e1000/e1000_main.c
> --- a/drivers/net/e1000/e1000_main.c~e1000-account-for-net_ip_align-when-calculating-bufsiz
> +++ a/drivers/net/e1000/e1000_main.c
> @@ -1101,7 +1101,7 @@ e1000_sw_init(struct e1000_adapter *adap
>
> pci_read_config_word(pdev, PCI_COMMAND, &hw->pci_cmd_word);
>
> - adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE;
> + adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE + NET_IP_ALIGN;
> adapter->rx_ps_bsize0 = E1000_RXBUFFER_128;
> hw->max_frame_size = netdev->mtu +
> ENET_HEADER_SIZE + ETHERNET_FCS_SIZE;
> @@ -3163,26 +3163,27 @@ e1000_change_mtu(struct net_device *netd
> * larger slab size
> * i.e. RXBUFFER_2048 --> size-4096 slab */
>
> - if (max_frame <= E1000_RXBUFFER_256)
> + if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_256)
> adapter->rx_buffer_len = E1000_RXBUFFER_256;
> - else if (max_frame <= E1000_RXBUFFER_512)
> + else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_512)
> adapter->rx_buffer_len = E1000_RXBUFFER_512;
> - else if (max_frame <= E1000_RXBUFFER_1024)
> + else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_1024)
> adapter->rx_buffer_len = E1000_RXBUFFER_1024;
> - else if (max_frame <= E1000_RXBUFFER_2048)
> + else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_2048)
> adapter->rx_buffer_len = E1000_RXBUFFER_2048;
> - else if (max_frame <= E1000_RXBUFFER_4096)
> + else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_4096)
> adapter->rx_buffer_len = E1000_RXBUFFER_4096;
> - else if (max_frame <= E1000_RXBUFFER_8192)
> + else if (max_frame + NET_IP_ALIGN <= E1000_RXBUFFER_8192)
> adapter->rx_buffer_len = E1000_RXBUFFER_8192;
> - else if (max_frame <= E1000_RXBUFFER_16384)
> + else
> adapter->rx_buffer_len = E1000_RXBUFFER_16384;
>
> /* adjust allocation if LPE protects us, and we aren't using SBP */
> if (!adapter->hw.tbi_compatibility_on &&
> ((max_frame == MAXIMUM_ETHERNET_FRAME_SIZE) ||
> (max_frame == MAXIMUM_ETHERNET_VLAN_SIZE)))
> - adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE;
> + adapter->rx_buffer_len = MAXIMUM_ETHERNET_VLAN_SIZE +
> + NET_IP_ALIGN;
>
> netdev->mtu = new_mtu;
>
> @@ -4002,7 +4003,8 @@ e1000_alloc_rx_buffers(struct e1000_adap
> struct e1000_buffer *buffer_info;
> struct sk_buff *skb;
> unsigned int i;
> - unsigned int bufsz = adapter->rx_buffer_len + NET_IP_ALIGN;
> + /* we have already accounted for NET_IP_ALIGN */
> + unsigned int bufsz = adapter->rx_buffer_len;
>
> i = rx_ring->next_to_use;
> buffer_info = &rx_ring->buffer_info[i];
> _
>
> -
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--
Evgeniy Polyakov
-
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