Re: ~3 hours old git tree: Virtual device lo asks to queue packet!

[Patrick McHardy]

Patrick McHardy wrote:
> Arkadiusz Miskiewicz wrote:
> 
>>>>CONFIG_NETDEVICES_MULTIQUEUE=y
>>>
>>>Does it go away if you disable this option?
>>
>>
>>Yes, it goes away after disabling this.
> 
> 
> I don't see a bug in the code itself, maybe the queue_mapping points
> to an invalid subqueue. Could you please try this patch and post the
> output?


OK I see what the problem is. The loopback device is statically
allocated, so it doesn't have any room for the subqueues reserved.

The easiest fix would be to use egress_subqueue[1] in struct
net_device, but I think that may cause warnings with newer gccs
when using a constant index that is > 0. OTOH using constant
indices doesn't seem to make much sense for the subqueue array.

Arkadiusz, does this patch fix the problem?

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index da7a13c..bf9399c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -575,7 +575,7 @@ struct net_device
 
        /* The TX queue control structures */
        unsigned int                    egress_subqueue_count;
-       struct net_device_subqueue      egress_subqueue[0];
+       struct net_device_subqueue      egress_subqueue[1];
 };
 #define to_net_dev(d) container_of(d, struct net_device, dev)
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 13a0d9f..4af0207 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3619,7 +3619,7 @@ struct net_device *alloc_netdev_mq(int sizeof_priv, const 
char *name,
 
        /* ensure 32-byte alignment of both the device and private area */
        alloc_size = (sizeof(*dev) + NETDEV_ALIGN_CONST +
-                    (sizeof(struct net_device_subqueue) * queue_count)) &
+                    (sizeof(struct net_device_subqueue) * (queue_count - 1))) &
                     ~NETDEV_ALIGN_CONST;
        alloc_size += sizeof_priv + NETDEV_ALIGN_CONST;
 
@@ -3637,7 +3637,7 @@ struct net_device *alloc_netdev_mq(int sizeof_priv, const 
char *name,
                dev->priv = ((char *)dev +
                             ((sizeof(struct net_device) +
                               (sizeof(struct net_device_subqueue) *
-                               queue_count) + NETDEV_ALIGN_CONST)
+                               (queue_count - 1)) + NETDEV_ALIGN_CONST)
                              & ~NETDEV_ALIGN_CONST));
        }