Regression: ixgb warning on MTU change

On Wed, 24 Sep 2008, Breno Leitao wrote:
> I just found an issue related to ixgb that seems to be a regression.
> After the interface is up and running (packets already transmitted), if
> I try to change the MTU, running "ifconfig ethX mtu 70", for example,
> causes the following warning[1].
> 
> Bisecting I found that the commit that caused this warning is
> fc2d14e36c69a8d44a2f5230835b54e95025363e. Reverting it solves the
> problem, ie, no more warnings.
> 
> Digging further, I found that just removing the following line added
> by fc2d14e36c69a8d44a2f5230835b54e95025363e's patch
> "buffer_info->dma = 0;", also solves the problem.
> 

Thanks for the report, I think this patch should fix it.  Please test and 
let us know.  This was compile tested only.

----

From: Jesse Brandeburg <jesse.brandeburg@intel.com>

ixgb: fix bug when freeing resources

It was pointed out by Breno Leitao <leitao@linux.vnet.ibm.com> that
ixgb would crash on PPC when an IOMMU was in use, if change_mtu was
called.

It appears to be a pretty simple issue in the driver that wasn't discovered
because most systems don't run with an IOMMU.  The driver needs to only unmap
buffers that are mapped (duh).

CC: Breno Leitao <leitao@linux.vnet.ibm.com>

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
---
 drivers/net/ixgb/ixgb_main.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)


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Hi Jesse, 

Brandeburg, Jesse wrote:
> On Wed, 24 Sep 2008, Breno Leitao wrote:
> Thanks for the report, I think this patch should fix it.  Please test and 
> let us know.  This was compile tested only.
I just tested this patch and it fixed that problem.  

Thanks

> ----
> 
> From: Jesse Brandeburg <jesse.brandeburg@intel.com>
> 
> ixgb: fix bug when freeing resources
> 
> It was pointed out by Breno Leitao <leitao@linux.vnet.ibm.com> that
> ixgb would crash on PPC when an IOMMU was in use, if change_mtu was
> called.
> 
> It appears to be a pretty simple issue in the driver that wasn't discovered
> because most systems don't run with an IOMMU.  The driver needs to only unmap
> buffers that are mapped (duh).
> 
> CC: Breno Leitao <leitao@linux.vnet.ibm.com>
> 
> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
> ---
>  drivers/net/ixgb/ixgb_main.c |    8 +++++---
>  1 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ixgb/ixgb_main.c b/drivers/net/ixgb/ixgb_main.c
> index aa75385..be3c7dc 100644
> --- a/drivers/net/ixgb/ixgb_main.c
> +++ b/drivers/net/ixgb/ixgb_main.c
> @@ -977,15 +977,17 @@ ixgb_clean_rx_ring(struct ixgb_adapter *adapter)
> 
>  	for (i = 0; i < rx_ring->count; i++) {
>  		buffer_info = &rx_ring->buffer_info[i];
> -		if (buffer_info->skb) {
> -
> +		if (buffer_info->dma) {
>  			pci_unmap_single(pdev,
>  					 buffer_info->dma,
>  					 buffer_info->length,
>  					 PCI_DMA_FROMDEVICE);
> +			buffer_info->dma = 0;
> +			buffer_info->length = 0;
> +		}
> 
> +		if (buffer_info->skb) {
>  			dev_kfree_skb(buffer_info->skb);
> -
>  			buffer_info->skb = NULL;
>  		}
>  	}
> 
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