Re: [PATCH net] net: dlink: handle dma_map_single() failure properly

On Sun, Oct 05, 2025 at 02:22:43PM +0900, Yeounsu Moon wrote:

Hello Simon.

I'm currenly re-writing the code as you suggested. I think `alloc_list()` 
can easily adopt the `goto` pattern, but for others functions, it's not 
that straightforward.

My question is whether a style combining `goto`, `continue`, and `break`
would be acceptable in this context:

	if (np->cur_rx - np->old_rx >= RX_RING_SIZE) {
		printk(KERN_INFO "Try to recover rx ring exhausted...\n");
		/* Re-allocate skbuffs to fill the descriptor ring */
		for (; np->cur_rx - np->old_rx > 0; np->old_rx++) {
			struct sk_buff *skb;
			dma_addr_t addr;
			entry = np->old_rx % RX_RING_SIZE;
			/* Dropped packets don't need to re-allocate */
			if (np->rx_skbuff[entry])
				goto fill_entry;

			skb = netdev_alloc_skb_ip_align(dev, np->rx_buf_sz);
			if (skb == NULL)
				goto out_clear_fraginfo;

			addr = dma_map_single(&np->pdev->dev, skb->data,
					      np->rx_buf_sz,
					      DMA_FROM_DEVICE);
			if (dma_mapping_error(&np->pdev->dev, addr))
				goto out_kfree_skb;

			np->rx_skbuff[entry] = skb;
			np->rx_ring[entry].fraginfo = cpu_to_le64(addr);
fill_entry:
			np->rx_ring[entry].fraginfo |=
			    cpu_to_le64((u64)np->rx_buf_sz << 48);
			np->rx_ring[entry].status = 0;
			continue;

out_kfree_skb:
			dev_kfree_skb_irq(skb);
out_clear_fraginfo:
			np->rx_ring[entry].fraginfo = 0;
			printk(KERN_INFO
			       "%s: Still unable to re-allocate Rx skbuff.#%d\n"
			       , dev->name, entry);
			break;
		} /* end for */
	} /* end if */
	spin_unlock_irqrestore (&np->rx_lock, flags);
	np->timer.expires = jiffies + next_tick;
	add_timer(&np->timer);
}

Or is there any better way to handle errors here?
I'd appreciate your guidance.

Sorry for the slow response, I've been ill for the past few days.

I did also consider the option above. That is handling the
errors in the loop. And I can see some merit in that approach,
e.g. reduced scope of variables.

But I think the more idiomatic approach is to handle them 'here'.
That is, at the end of the function. So I would lean towards
that option.