netdev - Re: [PATCH v2 net-next 05/15] net: sgi: ioc3-eth: allocate space for desc rings only once

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Date:   Thu, 29 Aug 2019 14:05:37 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Thomas Bogendoerfer <tbogendoerfer@...e.de>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 05/15] net: sgi: ioc3-eth: allocate space
 for desc rings only once

On Thu, 29 Aug 2019 17:50:03 +0200, Thomas Bogendoerfer wrote:
> Memory for descriptor rings are allocated/freed, when interface is
> brought up/down. Since the size of the rings is not changeable by
> hardware, we now allocate rings now during probe and free it, when
> device is removed.
> 
> Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@...e.de>
> ---
>  drivers/net/ethernet/sgi/ioc3-eth.c | 103 ++++++++++++++++++------------------
>  1 file changed, 51 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/net/ethernet/sgi/ioc3-eth.c b/drivers/net/ethernet/sgi/ioc3-eth.c
> index ba18a53fbbe6..d9d94a55ac34 100644
> --- a/drivers/net/ethernet/sgi/ioc3-eth.c
> +++ b/drivers/net/ethernet/sgi/ioc3-eth.c
> @@ -803,25 +803,17 @@ static void ioc3_free_rings(struct ioc3_private *ip)
>  	struct sk_buff *skb;
>  	int rx_entry, n_entry;
>  
> -	if (ip->txr) {
> -		ioc3_clean_tx_ring(ip);
> -		free_pages((unsigned long)ip->txr, 2);
> -		ip->txr = NULL;
> -	}
> +	ioc3_clean_tx_ring(ip);
>  
> -	if (ip->rxr) {
> -		n_entry = ip->rx_ci;
> -		rx_entry = ip->rx_pi;
> +	n_entry = ip->rx_ci;
> +	rx_entry = ip->rx_pi;
>  
> -		while (n_entry != rx_entry) {
> -			skb = ip->rx_skbs[n_entry];
> -			if (skb)
> -				dev_kfree_skb_any(skb);
> +	while (n_entry != rx_entry) {
> +		skb = ip->rx_skbs[n_entry];
> +		if (skb)
> +			dev_kfree_skb_any(skb);

I think dev_kfree_skb_any() accepts NULL

>  
> -			n_entry = (n_entry + 1) & RX_RING_MASK;
> -		}
> -		free_page((unsigned long)ip->rxr);
> -		ip->rxr = NULL;
> +		n_entry = (n_entry + 1) & RX_RING_MASK;
>  	}
>  }
>  
> @@ -829,49 +821,34 @@ static void ioc3_alloc_rings(struct net_device *dev)
>  {
>  	struct ioc3_private *ip = netdev_priv(dev);
>  	struct ioc3_erxbuf *rxb;
> -	unsigned long *rxr;
>  	int i;
>  
> -	if (!ip->rxr) {
> -		/* Allocate and initialize rx ring.  4kb = 512 entries  */
> -		ip->rxr = (unsigned long *)get_zeroed_page(GFP_ATOMIC);
> -		rxr = ip->rxr;
> -		if (!rxr)
> -			pr_err("%s: get_zeroed_page() failed!\n", __func__);
> -
> -		/* Now the rx buffers.  The RX ring may be larger but
> -		 * we only allocate 16 buffers for now.  Need to tune
> -		 * this for performance and memory later.
> -		 */
> -		for (i = 0; i < RX_BUFFS; i++) {
> -			struct sk_buff *skb;
> +	/* Now the rx buffers.  The RX ring may be larger but
> +	 * we only allocate 16 buffers for now.  Need to tune
> +	 * this for performance and memory later.
> +	 */
> +	for (i = 0; i < RX_BUFFS; i++) {
> +		struct sk_buff *skb;
>  
> -			skb = ioc3_alloc_skb(RX_BUF_ALLOC_SIZE, GFP_ATOMIC);
> -			if (!skb) {
> -				show_free_areas(0, NULL);
> -				continue;
> -			}
> +		skb = ioc3_alloc_skb(RX_BUF_ALLOC_SIZE, GFP_ATOMIC);
> +		if (!skb) {
> +			show_free_areas(0, NULL);
> +			continue;
> +		}
>  
> -			ip->rx_skbs[i] = skb;
> +		ip->rx_skbs[i] = skb;
>  
> -			/* Because we reserve afterwards. */
> -			skb_put(skb, (1664 + RX_OFFSET));
> -			rxb = (struct ioc3_erxbuf *)skb->data;
> -			rxr[i] = cpu_to_be64(ioc3_map(rxb, 1));
> -			skb_reserve(skb, RX_OFFSET);
> -		}
> -		ip->rx_ci = 0;
> -		ip->rx_pi = RX_BUFFS;
> +		/* Because we reserve afterwards. */
> +		skb_put(skb, (1664 + RX_OFFSET));
> +		rxb = (struct ioc3_erxbuf *)skb->data;
> +		ip->rxr[i] = cpu_to_be64(ioc3_map(rxb, 1));
> +		skb_reserve(skb, RX_OFFSET);
>  	}
> +	ip->rx_ci = 0;
> +	ip->rx_pi = RX_BUFFS;
>  
> -	if (!ip->txr) {
> -		/* Allocate and initialize tx rings.  16kb = 128 bufs.  */
> -		ip->txr = (struct ioc3_etxd *)__get_free_pages(GFP_KERNEL, 2);
> -		if (!ip->txr)
> -			pr_err("%s: __get_free_pages() failed!\n", __func__);
> -		ip->tx_pi = 0;
> -		ip->tx_ci = 0;
> -	}
> +	ip->tx_pi = 0;
> +	ip->tx_ci = 0;
>  }
>  
>  static void ioc3_init_rings(struct net_device *dev)
> @@ -1239,6 +1216,23 @@ static int ioc3_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  	timer_setup(&ip->ioc3_timer, ioc3_timer, 0);
>  
>  	ioc3_stop(ip);
> +
> +	/* Allocate and rx ring.  4kb = 512 entries  */
> +	ip->rxr = (unsigned long *)get_zeroed_page(GFP_ATOMIC);
> +	if (!ip->rxr) {
> +		pr_err("ioc3-eth: rx ring allocation failed\n");
> +		err = -ENOMEM;
> +		goto out_stop;
> +	}
> +
> +	/* Allocate tx rings.  16kb = 128 bufs.  */
> +	ip->txr = (struct ioc3_etxd *)__get_free_pages(GFP_KERNEL, 2);
> +	if (!ip->txr) {
> +		pr_err("ioc3-eth: tx ring allocation failed\n");
> +		err = -ENOMEM;
> +		goto out_stop;
> +	}

Please just use kcalloc()/kmalloc_array() here, and make sure the flags
are set to GFP_KERNEL whenever possible. Here and in ioc3_alloc_rings()
it looks like GFP_ATOMIC is unnecessary.