Subject: Re: [PATCH net-next] sunvnet: improve error handling when a remote crashes

From: David L Stevens <[email-masked]>
Date: Mon, 26 Jan 2015 14:48:31 -0500

This patch has a dependency on another one in my tree, so it won't apply; I'll
resubmit as a set.

							+-DLS

On 01/26/2015 02:10 PM, David L Stevens wrote:
> If a remote machine crashes while there are pending transmit buffers, the
> sunvnet driver reallocates the ring descriptors giving us enries that have
> state VIO_DESC_FREE but also an allocated skb. This results in a BUG_ON()
> call when the remote reboots and we reach that point in the ring.
> 
> This patch:
> 
> 1) clears pending tx packets in the ring on port reset
> 2) changes a BUG_ON() to a pr_warn() when a remote host has given us an invalid
> 	descriptor state
> 3) collapses multiple active buffer frees in a ring to a single message per
> 	ring and adds the device name and remote MAC address
> 
> This fixes the particular problem of not cleaning up pending buffers on a
> reset, but also prevents us from crashing if the remote handles descriptors
> out of order or sets an unexpected state for a descriptor.
> 
> Signed-off-by: David L Stevens <[email-masked]>
> ---
>  drivers/net/ethernet/sun/sunvnet.c |   68 +++++++++++++++++++++---------------
>  1 files changed, 40 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c
> index fe044f3..3733ae6 100644
> --- a/drivers/net/ethernet/sun/sunvnet.c
> +++ b/drivers/net/ethernet/sun/sunvnet.c
> @@ -50,6 +50,7 @@ MODULE_VERSION(DRV_MODULE_VERSION);
>  #define	VNET_MAX_RETRIES	10
>  
>  static int __vnet_tx_trigger(struct vnet_port *port, u32 start);
> +static void vnet_port_reset(struct vnet_port *port);
>  
>  /* Ordered from largest major to lowest */
>  static struct vio_version vnet_versions[] = {
> @@ -736,9 +737,7 @@ ldc_ctrl:
>  		vio_link_state_change(vio, event);
>  
>  		if (event == LDC_EVENT_RESET) {
> -			port->rmtu = 0;
> -			port->tso = true;
> -			port->tsolen = 0;
> +			vnet_port_reset(port);
>  			vio_port_up(vio);
>  		}
>  		port->rx_event = 0;
> @@ -934,36 +933,36 @@ static struct sk_buff *vnet_clean_tx_ring(struct vnet_port *port,
>  
>  	*pending = 0;
>  
> -	txi = dr->prod-1;
> -	if (txi < 0)
> -		txi = VNET_TX_RING_SIZE-1;
> -
> +	txi = dr->prod;
>  	for (i = 0; i < VNET_TX_RING_SIZE; ++i) {
>  		struct vio_net_desc *d;
>  
> -		d = vio_dring_entry(dr, txi);
> -
> -		if (d->hdr.state == VIO_DESC_DONE) {
> -			if (port->tx_bufs[txi].skb) {
> -				BUG_ON(port->tx_bufs[txi].skb->next);
> +		--txi;
> +		if (txi < 0)
> +			txi = VNET_TX_RING_SIZE-1;
>  
> -				port->tx_bufs[txi].skb->next = skb;
> -				skb = port->tx_bufs[txi].skb;
> -				port->tx_bufs[txi].skb = NULL;
> +		d = vio_dring_entry(dr, txi);
>  
> -				ldc_unmap(port->vio.lp,
> -					  port->tx_bufs[txi].cookies,
> -					  port->tx_bufs[txi].ncookies);
> -			}
> -			d->hdr.state = VIO_DESC_FREE;
> -		} else if (d->hdr.state == VIO_DESC_READY) {
> +		if (d->hdr.state == VIO_DESC_READY) {
>  			(*pending)++;
> -		} else if (d->hdr.state == VIO_DESC_FREE) {
> -			break;
> +			continue;
>  		}
> -		--txi;
> -		if (txi < 0)
> -			txi = VNET_TX_RING_SIZE-1;
> +		if (port->tx_bufs[txi].skb) {
> +			if (d->hdr.state != VIO_DESC_DONE)
> +				pr_warn("invalid ring buffer state %d\n",
> +					d->hdr.state);
> +			BUG_ON(port->tx_bufs[txi].skb->next);
> +
> +			port->tx_bufs[txi].skb->next = skb;
> +			skb = port->tx_bufs[txi].skb;
> +			port->tx_bufs[txi].skb = NULL;
> +
> +			ldc_unmap(port->vio.lp,
> +				  port->tx_bufs[txi].cookies,
> +				  port->tx_bufs[txi].ncookies);
> +		} else if (d->hdr.state == VIO_DESC_FREE)
> +			break;
> +		d->hdr.state = VIO_DESC_FREE;
>  	}
>  	return skb;
>  }
> @@ -1633,7 +1632,9 @@ static const struct ethtool_ops vnet_ethtool_ops = {
>  
>  static void vnet_port_free_tx_bufs(struct vnet_port *port)
>  {
> +	struct net_device *dev = port->vp->dev;
>  	struct vio_dring_state *dr;
> +	bool active_freed = false;
>  	int i;
>  
>  	dr = &port->vio.drings[VIO_DRIVER_TX_RING];
> @@ -1649,8 +1650,7 @@ static void vnet_port_free_tx_bufs(struct vnet_port *port)
>  			continue;
>  
>  		d = vio_dring_entry(dr, i);
> -		if (d->hdr.state == VIO_DESC_READY)
> -			pr_warn("active transmit buffers freed\n");
> +		active_freed |= d->hdr.state == VIO_DESC_READY;
>  
>  		ldc_unmap(port->vio.lp,
>  			  port->tx_bufs[i].cookies,
> @@ -1662,6 +1662,9 @@ static void vnet_port_free_tx_bufs(struct vnet_port *port)
>  	ldc_free_exp_dring(port->vio.lp, dr->base,
>  			   (dr->entry_size * dr->num_entries),
>  			   dr->cookies, dr->ncookies);
> +	if (active_freed)
> +		pr_warn("%s: active transmit buffers freed for remote %pM\n",
> +			dev->name, port->raddr);
>  	dr->base = NULL;
>  	dr->entry_size = 0;
>  	dr->num_entries = 0;
> @@ -1669,6 +1672,15 @@ static void vnet_port_free_tx_bufs(struct vnet_port *port)
>  	dr->ncookies = 0;
>  }
>  
> +static void vnet_port_reset(struct vnet_port *port)
> +{
> +	del_timer(&port->clean_timer);
> +	vnet_port_free_tx_bufs(port);
> +	port->rmtu = 0;
> +	port->tso = true;
> +	port->tsolen = 0;
> +}
> +
>  static int vnet_port_alloc_tx_ring(struct vnet_port *port)
>  {
>  	struct vio_dring_state *dr;
>