netdev - Re: [PATCH net v5 2/2] net/ps3_gelic_net: Use dma_mapping

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Date:   Tue, 14 Feb 2023 18:28:03 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Geoff Levand <geoff@...radead.org>
CC:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>
Subject: Re: [PATCH net v5 2/2] net/ps3_gelic_net: Use dma_mapping_error

From: Geoff Levand <geoff@...radead.org>
Date: Sun, 12 Feb 2023 18:00:58 +0000

> The current Gelic Etherenet driver was checking the return value of its
> dma_map_single call, and not using the dma_mapping_error() routine.
> 
> Fixes runtime problems like these:
> 
>   DMA-API: ps3_gelic_driver sb_05: device driver failed to check map error
>   WARNING: CPU: 0 PID: 0 at kernel/dma/debug.c:1027 .check_unmap+0x888/0x8dc
> 
> Fixes: 02c1889166b4 (ps3: gigabit ethernet driver for PS3, take3)
> Signed-off-by: Geoff Levand <geoff@...radead.org>
> ---
>  drivers/net/ethernet/toshiba/ps3_gelic_net.c | 41 ++++++++++----------
>  1 file changed, 20 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/net/ethernet/toshiba/ps3_gelic_net.c b/drivers/net/ethernet/toshiba/ps3_gelic_net.c
> index 2bb68e60d0d5..0e52bb99e344 100644
> --- a/drivers/net/ethernet/toshiba/ps3_gelic_net.c
> +++ b/drivers/net/ethernet/toshiba/ps3_gelic_net.c
> @@ -309,22 +309,30 @@ static int gelic_card_init_chain(struct gelic_card *card,
>  				 struct gelic_descr_chain *chain,
>  				 struct gelic_descr *start_descr, int no)
>  {
> -	int i;
> +	struct device *dev = ctodev(card);
>  	struct gelic_descr *descr;
> +	int i;
>  
> -	descr = start_descr;
> -	memset(descr, 0, sizeof(*descr) * no);
> +	memset(start_descr, 0, no * sizeof(*start_descr));
>  
>  	/* set up the hardware pointers in each descriptor */
> -	for (i = 0; i < no; i++, descr++) {
> +	for (i = 0, descr = start_descr; i < no; i++, descr++) {
>  		gelic_descr_set_status(descr, GELIC_DESCR_DMA_NOT_IN_USE);
>  		descr->bus_addr =
>  			dma_map_single(ctodev(card), descr,
>  				       GELIC_DESCR_SIZE,
>  				       DMA_BIDIRECTIONAL);
>  
> -		if (!descr->bus_addr)
> -			goto iommu_error;
> +		if (unlikely(dma_mapping_error(dev, descr->bus_addr))) {

dma_mapping_error() already has unlikely() inside.

> +			dev_err(dev, "%s:%d: dma_mapping_error\n", __func__,
> +				__LINE__);
> +
> +			for (i--, descr--; i >= 0; i--, descr--) {
> +				dma_unmap_single(ctodev(card), descr->bus_addr,
> +					GELIC_DESCR_SIZE, DMA_BIDIRECTIONAL);
> +			}
> +			return -ENOMEM;
> +		}
>  
>  		descr->next = descr + 1;
>  		descr->prev = descr - 1;
> @@ -346,14 +354,6 @@ static int gelic_card_init_chain(struct gelic_card *card,
>  	(descr - 1)->next_descr_addr = 0;
>  
>  	return 0;
> -
> -iommu_error:
> -	for (i--, descr--; 0 <= i; i--, descr--)
> -		if (descr->bus_addr)
> -			dma_unmap_single(ctodev(card), descr->bus_addr,
> -					 GELIC_DESCR_SIZE,
> -					 DMA_BIDIRECTIONAL);
> -	return -ENOMEM;
>  }
>  
>  /**
> @@ -408,13 +408,12 @@ static int gelic_descr_prepare_rx(struct gelic_card *card,
>  	descr->buf_addr = dma_map_single(dev, descr->skb->data, descr->buf_size,
>  		DMA_FROM_DEVICE);
>  
> -	if (!descr->buf_addr) {
> +	if (unlikely(dma_mapping_error(dev, descr->buf_addr))) {

Same.

> +		dev_err(dev, "%s:%d: dma_mapping_error\n", __func__, __LINE__);

It is fast path. You're not allowed to use plain printk on fast path,
since you may generate then thousands of messages per second.
Consider looking at _ratelimit family of functions.

>  		dev_kfree_skb_any(descr->skb);
>  		descr->buf_addr = 0;
>  		descr->buf_size = 0;
>  		descr->skb = NULL;
> -		dev_info(dev,
> -			 "%s:Could not iommu-map rx buffer\n", __func__);
>  		gelic_descr_set_status(descr, GELIC_DESCR_DMA_NOT_IN_USE);
>  		return -ENOMEM;
>  	}
> @@ -774,6 +773,7 @@ static int gelic_descr_prepare_tx(struct gelic_card *card,
>  				  struct gelic_descr *descr,
>  				  struct sk_buff *skb)
>  {
> +	struct device *dev = ctodev(card);
>  	dma_addr_t buf;
>  
>  	if (card->vlan_required) {
> @@ -788,11 +788,10 @@ static int gelic_descr_prepare_tx(struct gelic_card *card,
>  		skb = skb_tmp;
>  	}
>  
> -	buf = dma_map_single(ctodev(card), skb->data, skb->len, DMA_TO_DEVICE);
> +	buf = dma_map_single(dev, skb->data, skb->len, DMA_TO_DEVICE);
>  
> -	if (!buf) {
> -		dev_err(ctodev(card),
> -			"dma map 2 failed (%p, %i). Dropping packet\n",
> +	if (unlikely(dma_mapping_error(dev, buf))) {
> +		dev_err(dev, "dma map 2 failed (%p, %i). Dropping packet\n",

Same, same (for both lines).

>  			skb->data, skb->len);
>  		return -ENOMEM;
>  	}
Thanks,
Olek