Re: [Qemu-devel] [PATCH V2] net: don't use set/get_pointer() in set/get_netdev()

[Jason Wang]

On 10/10/2014 09:03 PM, Markus Armbruster wrote:
> Jason Wang <address@hidden> writes:
>
>> Commit 1ceef9f27359cbe92ef124bf74de6f792e71f6fb (net: multiqueue
>> support) tries to use set_pointer() and get_pointer() to set and get
>> NICPeers which is not a pointer defined in DEFINE_PROP_NETDEV. This
>> trick works but result a unclean and fragile implementation (e.g
>> print_netdev and parse_netdev).
>>
>> This patch solves this issue by not using set/get_pinter() and set and
>> get netdev directly in set_netdev() and get_netdev(). After this the
>> parse_netdev() and print_netdev() were no longer used and dropped from
>> the source.
>>
>> Cc: Markus Armbruster <address@hidden>
>> Cc: Stefan Hajnoczi <address@hidden>
>> Cc: Peter Maydell <address@hidden>
>> Signed-off-by: Jason Wang <address@hidden>
>> ---
>> Changes from V1:
>> - validate ncs pointer before accessing them, this fixes the qtest failure
>>   on arm.
>> ---
>>  hw/core/qdev-properties-system.c | 71 
>> ++++++++++++++++++++++------------------
>>  1 file changed, 39 insertions(+), 32 deletions(-)
>>
>> diff --git a/hw/core/qdev-properties-system.c 
>> b/hw/core/qdev-properties-system.c
>> index ae0900f..6939ea5 100644
>> --- a/hw/core/qdev-properties-system.c
>> +++ b/hw/core/qdev-properties-system.c
>> @@ -176,41 +176,67 @@ PropertyInfo qdev_prop_chr = {
>>  };
>>  
>>  /* --- netdev device --- */
>> +static void get_netdev(Object *obj, Visitor *v, void *opaque,
>> +                       const char *name, Error **errp)
>> +{
>> +    DeviceState *dev = DEVICE(obj);
>> +    Property *prop = opaque;
>> +    NICPeers *peers_ptr = qdev_get_prop_ptr(dev, prop);
>> +    char *p = g_strdup(peers_ptr->ncs[0] ? peers_ptr->ncs[0]->name : "");
> Can ->ncs[0]->name ever be null?

Seems not, id is mandatory for netdev.
>
>>  
>> -static int parse_netdev(DeviceState *dev, const char *str, void **ptr)
>> +    visit_type_str(v, &p, name, errp);
>> +    g_free(p);
>> +}
>> +
>> +static void set_netdev(Object *obj, Visitor *v, void *opaque,
>> +                       const char *name, Error **errp)
>>  {
>> -    NICPeers *peers_ptr = (NICPeers *)ptr;
>> +    DeviceState *dev = DEVICE(obj);
>> +    Property *prop = opaque;
>> +    NICPeers *peers_ptr = qdev_get_prop_ptr(dev, prop);
>>      NetClientState **ncs = peers_ptr->ncs;
>>      NetClientState *peers[MAX_QUEUE_NUM];
>> -    int queues, i = 0;
>> -    int ret;
>> +    Error *local_err = NULL;
>> +    int err, queues, i = 0;
>> +    char *str;
>> +
>> +    if (dev->realized) {
>> +        qdev_prop_set_after_realize(dev, name, errp);
>> +        return;
>> +    }
>> +
>> +    visit_type_str(v, &str, name, &local_err);
>> +    if (local_err) {
>> +        error_propagate(errp, local_err);
>> +        return;
>> +    }
>>  
>>      queues = qemu_find_net_clients_except(str, peers,
>>                                            NET_CLIENT_OPTIONS_KIND_NIC,
>>                                            MAX_QUEUE_NUM);
>>      if (queues == 0) {
>> -        ret = -ENOENT;
>> +        err = -ENOENT;
>>          goto err;
>>      }
>>  
>>      if (queues > MAX_QUEUE_NUM) {
>> -        ret = -E2BIG;
>> +        err = -E2BIG;
> error_set_from_qdev_prop_error() does not accept -E2BIG.
>
> You could call error_setg(...) directly instead.

Ok.
>>          goto err;
>>      }
>>  
>>      for (i = 0; i < queues; i++) {
>>          if (peers[i] == NULL) {
>> -            ret = -ENOENT;
>> +            err = -ENOENT;
>>              goto err;
>>          }
>>  
>>          if (peers[i]->peer) {
>> -            ret = -EEXIST;
>> +            err = -EEXIST;
>>              goto err;
>>          }
>>  
>>          if (ncs[i]) {
>> -            ret = -EINVAL;
>> +            err = -EINVAL;
> error_set_from_qdev_prop_error() does not accept -EINVAL, either.

Ok.
>>              goto err;
>>          }
>>  
>> @@ -219,31 +245,12 @@ static int parse_netdev(DeviceState *dev, const char 
>> *str, void **ptr)
>>      }
>>  
>>      peers_ptr->queues = queues;
>> -
>> -    return 0;
>> +    g_free(str);
>> +    return;
>>  
>>  err:
> Label err clashes with local variable err.  Harmless, but maybe you'd
> like to rename one of them.

It was used in "error_set_from_qdev_prop_error(errp, err, dev, prop, str);"
>> -    return ret;
>> -}
>> -
>> -static char *print_netdev(void *ptr)
>> -{
>> -    NetClientState *netdev = ptr;
>> -    const char *val = netdev->name ? netdev->name : "";
>> -
>> -    return g_strdup(val);
>> -}
>> -
>> -static void get_netdev(Object *obj, Visitor *v, void *opaque,
>> -                       const char *name, Error **errp)
>> -{
>> -    get_pointer(obj, v, opaque, print_netdev, name, errp);
>> -}
>> -
>> -static void set_netdev(Object *obj, Visitor *v, void *opaque,
>> -                       const char *name, Error **errp)
>> -{
>> -    set_pointer(obj, v, opaque, parse_netdev, name, errp);
>> +    error_set_from_qdev_prop_error(errp, err, dev, prop, str);
>> +    g_free(str);
>>  }
>>  
>>  PropertyInfo qdev_prop_netdev = {
> Instead of
>
>         g_free(str);
>         return;
>
>     err:
>         error_set_from_qdev_prop_error(errp, err, dev, prop, str);
>         g_free(str);
>     }
>
> You could exploit that error_set_from_qdev_prop_error() does nothing
> when err is 0:
>
>     out:
>         g_free(str);
>         error_set_from_qdev_prop_error(errp, err, dev, prop, str);
>         g_free(str);
>     }

This looks more clean, will do.

Thanks