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SubjectRe: [PATCH] forcedeth: Fix WARNINGS that result when DMA mapping is not checked
On 12/27/2012 02:05 PM, Eric Dumazet wrote:
> On Thu, 2012-12-27 at 13:42 -0600, Larry Finger wrote:
>> With 3.8-rc1, the first call of pci_map_single() that is not checked
>> with a corresponding pci_dma_mapping_error() call results in a warning
>> with a splat as follows:
>>
>> WARNING: at lib/dma-debug.c:933 check_unmap+0x480/0x950()
>> Hardware name: HP Pavilion dv2700 Notebook PC
>> forcedeth 0000:00:0a.0: DMA-API: device driver failed to check
>> map error[device address=0x00000000b176e002] [size=90 bytes] [mapped as single]
>>
>> Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
>> ---
>> drivers/net/ethernet/nvidia/forcedeth.c | 23 +++++++++++++++++++++++
>> 1 file changed, 23 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/nvidia/forcedeth.c b/drivers/net/ethernet/nvidia/forcedeth.c
>> index 653487d..de39cf2 100644
>> --- a/drivers/net/ethernet/nvidia/forcedeth.c
>> +++ b/drivers/net/ethernet/nvidia/forcedeth.c
>> @@ -1821,6 +1821,11 @@ static int nv_alloc_rx(struct net_device *dev)
>> skb->data,
>> skb_tailroom(skb),
>> PCI_DMA_FROMDEVICE);
>> + if (pci_dma_mapping_error(np->pci_dev,
>> + np->put_rx_ctx->dma)) {
>> + dev_kfree_skb_any(skb);
>
> skb has no destructor yet, kfree_skb(skb) should be fine

OK.

>
>> + goto packet_dropped;
>> + }
>> np->put_rx_ctx->dma_len = skb_tailroom(skb);
>> np->put_rx.orig->buf = cpu_to_le32(np->put_rx_ctx->dma);
>> wmb();
>> @@ -1830,6 +1835,7 @@ static int nv_alloc_rx(struct net_device *dev)
>> if (unlikely(np->put_rx_ctx++ == np->last_rx_ctx))
>> np->put_rx_ctx = np->first_rx_ctx;
>> } else {
>> +packet_dropped:
>> u64_stats_update_begin(&np->swstats_rx_syncp);
>> np->stat_rx_dropped++;
>> u64_stats_update_end(&np->swstats_rx_syncp);
>> @@ -1856,6 +1862,11 @@ static int nv_alloc_rx_optimized(struct net_device *dev)
>> skb->data,
>> skb_tailroom(skb),
>> PCI_DMA_FROMDEVICE);
>> + if (pci_dma_mapping_error(np->pci_dev,
>> + np->put_rx_ctx->dma)) {
>> + dev_kfree_skb_any(skb);
>> + goto packet_dropped;
>> + }
>> np->put_rx_ctx->dma_len = skb_tailroom(skb);
>> np->put_rx.ex->bufhigh = cpu_to_le32(dma_high(np->put_rx_ctx->dma));
>> np->put_rx.ex->buflow = cpu_to_le32(dma_low(np->put_rx_ctx->dma));
>> @@ -1866,6 +1877,7 @@ static int nv_alloc_rx_optimized(struct net_device *dev)
>> if (unlikely(np->put_rx_ctx++ == np->last_rx_ctx))
>> np->put_rx_ctx = np->first_rx_ctx;
>> } else {
>> +packet_dropped:
>> u64_stats_update_begin(&np->swstats_rx_syncp);
>> np->stat_rx_dropped++;
>> u64_stats_update_end(&np->swstats_rx_syncp);
>> @@ -2217,6 +2229,9 @@ static netdev_tx_t nv_start_xmit(struct sk_buff *skb, struct net_device *dev)
>> bcnt = (size > NV_TX2_TSO_MAX_SIZE) ? NV_TX2_TSO_MAX_SIZE : size;
>> np->put_tx_ctx->dma = pci_map_single(np->pci_dev, skb->data + offset, bcnt,
>> PCI_DMA_TODEVICE);
>> + if (pci_dma_mapping_error(np->pci_dev,
>> + np->put_tx_ctx->dma))
>> + return NETDEV_TX_BUSY;
>
> Really this is not going to work very well : caller will call this in a
> loop.

Any suggestions on what value should be returned, or does the caller need to be
modified?

Thanks for the review,

Larry



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