netdev - Re: [PATCH] jme: Fix DMA unmap warning

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Date:	Wed, 7 May 2014 01:55:00 +0530 (IST)
From:	Govindarajulu Varadarajan <_govind@....com>
To:	Neil Horman <nhorman@...driver.com>
cc:	netdev@...r.kernel.org, Guo-Fu Tseng <cooldavid@...ldavid.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] jme: Fix DMA unmap warning



On Mon, 5 May 2014, Neil Horman wrote:

> The jme driver forgot to check the return status from pci_map_page in its tx
> path, causing a dma api warning on unmap.  Easy fix, just do the check and
> augment the tx path to tell the stack that the driver is busy so we re-queue the
> frame.
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>
> CC: Guo-Fu Tseng <cooldavid@...ldavid.org>
> CC: "David S. Miller" <davem@...emloft.net>
> ---
> drivers/net/ethernet/jme.c | 53 ++++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 47 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/ethernet/jme.c b/drivers/net/ethernet/jme.c
> index b0c6050..6e664d9 100644
> --- a/drivers/net/ethernet/jme.c
> +++ b/drivers/net/ethernet/jme.c
> @@ -1988,7 +1988,7 @@ jme_alloc_txdesc(struct jme_adapter *jme,
> 	return idx;
> }
>
> -static void
> +static int
> jme_fill_tx_map(struct pci_dev *pdev,
> 		struct txdesc *txdesc,
> 		struct jme_buffer_info *txbi,
> @@ -2005,6 +2005,9 @@ jme_fill_tx_map(struct pci_dev *pdev,
> 				len,
> 				PCI_DMA_TODEVICE);
>
> +	if (unlikely(pci_dma_mapping_error(pdev, dmaaddr)))
> +		return -EINVAL;
> +
> 	pci_dma_sync_single_for_device(pdev,
> 				       dmaaddr,
> 				       len,
> @@ -2021,9 +2024,30 @@ jme_fill_tx_map(struct pci_dev *pdev,
>
> 	txbi->mapping = dmaaddr;
> 	txbi->len = len;
> +	return 0;
> }
>
> -static void
> +static void jme_drop_tx_map(struct jme_adapter *jme, int startidx, int endidx)
> +{
> +	struct jme_ring *txring = &(jme->txring[0]);
> +	struct jme_buffer_info *txbi = txring->bufinf, *ctxbi;
> +	int mask = jme->tx_ring_mask;
> +	int j;
> +
> +	for (j = startidx ; j < endidx ; ++j) {
> +		ctxbi = txbi + ((startidx + j + 2) & (mask));
> +		pci_unmap_page(jme->pdev,
> +				ctxbi->mapping,
> +				ctxbi->len,
> +				PCI_DMA_TODEVICE);
> +
> +				ctxbi->mapping = 0;
> +				ctxbi->len = 0;

Alignment, a tab from 'for'
> +	}
> +
> +}
> +
> +static int
> jme_map_tx_skb(struct jme_adapter *jme, struct sk_buff *skb, int idx)
> {
> 	struct jme_ring *txring = &(jme->txring[0]);
> @@ -2034,25 +2058,37 @@ jme_map_tx_skb(struct jme_adapter *jme, struct sk_buff *skb, int idx)
> 	int mask = jme->tx_ring_mask;
> 	const struct skb_frag_struct *frag;
> 	u32 len;
> +	int ret = 0;
>
> 	for (i = 0 ; i < nr_frags ; ++i) {
> 		frag = &skb_shinfo(skb)->frags[i];
> 		ctxdesc = txdesc + ((idx + i + 2) & (mask));
> 		ctxbi = txbi + ((idx + i + 2) & (mask));
>
> -		jme_fill_tx_map(jme->pdev, ctxdesc, ctxbi,
> +		ret = jme_fill_tx_map(jme->pdev, ctxdesc, ctxbi,
> 				skb_frag_page(frag),
> 				frag->page_offset, skb_frag_size(frag), hidma);
> +		if (ret) {
> +			jme_drop_tx_map(jme, idx, idx+i);
> +			goto out;

Why not just return here, you are using out:, only once.

Govind
> +		}
> +
> 	}
>
> 	len = skb_is_nonlinear(skb) ? skb_headlen(skb) : skb->len;
> 	ctxdesc = txdesc + ((idx + 1) & (mask));
> 	ctxbi = txbi + ((idx + 1) & (mask));
> -	jme_fill_tx_map(jme->pdev, ctxdesc, ctxbi, virt_to_page(skb->data),
> +	ret = jme_fill_tx_map(jme->pdev, ctxdesc, ctxbi, virt_to_page(skb->data),
> 			offset_in_page(skb->data), len, hidma);
> +	if (ret)
> +		jme_drop_tx_map(jme, idx, idx+i);
> +
> +out:
> +	return ret;
>
> }
>
> +
> static int
> jme_tx_tso(struct sk_buff *skb, __le16 *mss, u8 *flags)
> {
> @@ -2131,6 +2167,7 @@ jme_fill_tx_desc(struct jme_adapter *jme, struct sk_buff *skb, int idx)
> 	struct txdesc *txdesc;
> 	struct jme_buffer_info *txbi;
> 	u8 flags;
> +	int ret = 0;
>
> 	txdesc = (struct txdesc *)txring->desc + idx;
> 	txbi = txring->bufinf + idx;
> @@ -2155,7 +2192,10 @@ jme_fill_tx_desc(struct jme_adapter *jme, struct sk_buff *skb, int idx)
> 	if (jme_tx_tso(skb, &txdesc->desc1.mss, &flags))
> 		jme_tx_csum(jme, skb, &flags);
> 	jme_tx_vlan(skb, &txdesc->desc1.vlan, &flags);
> -	jme_map_tx_skb(jme, skb, idx);
> +	ret = jme_map_tx_skb(jme, skb, idx);
> +	if (ret)
> +		return ret;
> +
> 	txdesc->desc1.flags = flags;
> 	/*
> 	 * Set tx buffer info after telling NIC to send
> @@ -2228,7 +2268,8 @@ jme_start_xmit(struct sk_buff *skb, struct net_device *netdev)
> 		return NETDEV_TX_BUSY;
> 	}
>
> -	jme_fill_tx_desc(jme, skb, idx);
> +	if (jme_fill_tx_desc(jme, skb, idx))
> +		return NETDEV_TX_BUSY;
>
> 	jwrite32(jme, JME_TXCS, jme->reg_txcs |
> 				TXCS_SELECT_QUEUE0 |
> -- 
> 1.8.3.1
>
> --
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