Subject: Re: [PATCH net-next] xen-netback: Follow-up patch for grant mapping series

From: Zoltan Kiss <[email-masked]>
Date: Fri, 21 Mar 2014 19:31:21 +0000

On 21/03/14 09:41, Ian Campbell wrote:
> On Thu, 2014-03-20 at 19:32 +0000, Zoltan Kiss wrote:
>> Ian made some late comments about the grant mapping series, I incorporated the
>> outcomes into this patch. Additional comments, refactoring etc.
>
> I don't know how davem feels about merging these kinds of thing into one
> patch but from my point of view the least thing to do is to enumerate
> the cleanups -- so that people can verify that the patch does infact do
> exactly what it says it does, no more, no less.
Ok, I'll make a detailed list in the commit message about what are the 
changes, and fix up the typos you mentioned below.
>
>> Signed-off-by: Zoltan Kiss <[email-masked]>
>> ---
>> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
>> index 6837bfc..fa19538 100644
>> --- a/drivers/net/xen-netback/interface.c
>> +++ b/drivers/net/xen-netback/interface.c
>> @@ -576,15 +576,15 @@ void xenvif_disconnect(struct xenvif *vif)
>>   void xenvif_free(struct xenvif *vif)
>>   {
>>   	int i, unmap_timeout = 0;
>> -	/* Here we want to avoid timeout messages if an skb can be legitimatly
>> -	 * stucked somewhere else. Realisticly this could be an another vif's
>> +	/* Here we want to avoid timeout messages if an skb can be legitimately
>> +	 * stuck somewhere else. Realistically this could be an another vif's
>>   	 * internal or QDisc queue. That another vif also has this
>>   	 * rx_drain_timeout_msecs timeout, but the timer only ditches the
>>   	 * internal queue. After that, the QDisc queue can put in worst case
>>   	 * XEN_NETIF_RX_RING_SIZE / MAX_SKB_FRAGS skbs into that another vif's
>>   	 * internal queue, so we need several rounds of such timeouts until we
>>   	 * can be sure that no another vif should have skb's from us. We are
>> -	 * not sending more skb's, so newly stucked packets are not interesting
>> +	 * not sending more skb's, so newly stuck packets are not interesting
>>   	 * for us here.
>>   	 */
>>   	unsigned int worst_case_skb_lifetime = (rx_drain_timeout_msecs/1000) *
>> @@ -599,6 +599,13 @@ void xenvif_free(struct xenvif *vif)
>>   				netdev_err(vif->dev,
>>   					   "Page still granted! Index: %x\n",
>>   					   i);
>> +			/* If there are still unmapped pages, reset the loop to
>> +			 * start mchecking again. We shouldn't exit here until
>
> "checking"
>
>> +			 * dealloc thread and NAPI instance release all the
>> +			 * pages. If a kernel bug cause the skbs stall
>
> "causes the skbs to stall"
>
>> +			 * somewhere, the interface couldn't be brought down
>> +			 * properly.
>
> I'm not sure what you are saying here exactly. Perhaps you means
> s/couldn't/cannot/?
>
>> +			 */
>>   			i = -1;
>>   		}
>>   	}
>> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
>> index 1c336f6..0e46184b 100644
>> --- a/drivers/net/xen-netback/netback.c
>> +++ b/drivers/net/xen-netback/netback.c
>> @@ -56,7 +56,7 @@ bool separate_tx_rx_irq = 1;
>>   module_param(separate_tx_rx_irq, bool, 0644);
>>
>>   /* When guest ring is filled up, qdisc queues the packets for us, but we have
>> - * to timeout them, otherwise other guests' packets can get stucked there
>> + * to timeout them, otherwise other guests' packets can get stuck there
>>    */
>>   unsigned int rx_drain_timeout_msecs = 10000;
>>   module_param(rx_drain_timeout_msecs, uint, 0444);
>> @@ -99,6 +99,9 @@ static inline unsigned long idx_to_kaddr(struct xenvif *vif,
>>   	return (unsigned long)pfn_to_kaddr(idx_to_pfn(vif, idx));
>>   }
>>
>> +#define callback_param(vif, pending_idx) \
>> +	(vif->pending_tx_info[pending_idx].callback_struct)
>> +
>>   /* Find the containing VIF's structure from a pointer in pending_tx_info array
>>    */
>>   static inline struct xenvif* ubuf_to_vif(struct ubuf_info *ubuf)
>> @@ -1025,12 +1028,12 @@ static void xenvif_fill_frags(struct xenvif *vif, struct sk_buff *skb)
>>   		/* If this is not the first frag, chain it to the previous*/
>>   		if (unlikely(prev_pending_idx == INVALID_PENDING_IDX))
>>   			skb_shinfo(skb)->destructor_arg =
>> -				&vif->pending_tx_info[pending_idx].callback_struct;
>> +				&callback_param(vif, pending_idx);
>>   		else if (likely(pending_idx != prev_pending_idx))
>> -			vif->pending_tx_info[prev_pending_idx].callback_struct.ctx =
>> -				&(vif->pending_tx_info[pending_idx].callback_struct);
>> +			callback_param(vif, prev_pending_idx).ctx =
>> +				&callback_param(vif, pending_idx);
>>
>> -		vif->pending_tx_info[pending_idx].callback_struct.ctx = NULL;
>> +		callback_param(vif, pending_idx).ctx = NULL;
>>   		prev_pending_idx = pending_idx;
>>
>>   		txp = &vif->pending_tx_info[pending_idx].req;
>> @@ -1400,13 +1403,13 @@ static int xenvif_tx_submit(struct xenvif *vif)
>>   		memcpy(skb->data,
>>   		       (void *)(idx_to_kaddr(vif, pending_idx)|txp->offset),
>>   		       data_len);
>> -		vif->pending_tx_info[pending_idx].callback_struct.ctx = NULL;
>> +		callback_param(vif, pending_idx).ctx = NULL;
>>   		if (data_len < txp->size) {
>>   			/* Append the packet payload as a fragment. */
>>   			txp->offset += data_len;
>>   			txp->size -= data_len;
>>   			skb_shinfo(skb)->destructor_arg =
>> -				&vif->pending_tx_info[pending_idx].callback_struct;
>> +				&callback_param(vif, pending_idx);
>>   		} else {
>>   			/* Schedule a response immediately. */
>>   			xenvif_idx_unmap(vif, pending_idx);
>> @@ -1550,7 +1553,6 @@ static inline void xenvif_tx_dealloc_action(struct xenvif *vif)
>>   					    idx_to_kaddr(vif, pending_idx),
>>   					    GNTMAP_host_map,
>>   					    vif->grant_tx_handle[pending_idx]);
>> -			/* Btw. already unmapped? */
>>   			xenvif_grant_handle_reset(vif, pending_idx);
>>   			++gop;
>>   		}
>> @@ -1683,12 +1685,20 @@ void xenvif_idx_unmap(struct xenvif *vif, u16 pending_idx)
>>   			    idx_to_kaddr(vif, pending_idx),
>>   			    GNTMAP_host_map,
>>   			    vif->grant_tx_handle[pending_idx]);
>> -	/* Btw. already unmapped? */
>>   	xenvif_grant_handle_reset(vif, pending_idx);
>>
>>   	ret = gnttab_unmap_refs(&tx_unmap_op, NULL,
>>   				&vif->mmap_pages[pending_idx], 1);
>> -	BUG_ON(ret);
>> +	if (ret) {
>> +		netdev_err(vif->dev,
>> +			   "Unmap fail: ret: %d pending_idx: %d host_addr: %llx handle: %x status: %d\n",
>> +			   ret,
>> +			   pending_idx,
>> +			   tx_unmap_op.host_addr,
>> +			   tx_unmap_op.handle,
>> +			   tx_unmap_op.status);
>> +		BUG();
>> +	}
>>
>>   	xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_OKAY);
>>   }
>
>