[NET]: Inline net_device_stats

Network drivers which keep stats allocate their own stats structure
then write a get_stats() function to return them.  It would be nice if
this were done by default.

1) Add a new "stats" field to "struct net_device".
2) Add a new feature field to say "this driver uses the internal one"
3) Have a default "get_stats" which returns NULL if that feature not set.
4) Change callers to check result of get_stats call for NULL, not if
   ->get_stats is set.

This should not break backwards compatibility with older drivers, yet
allow modern drivers to shed some boilerplate code.

Lightly tested: works for a modified lguest network driver.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 3 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 86dc9f693f66..fec8cf27f75d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -817,7 +817,6 @@ static int default_rebuild_header(struct sk_buff *skb)
         return 1;
 }
 
-
 /**
  *      dev_open        - prepare an interface for use.
  *      @dev:   device to open
@@ -2096,9 +2095,9 @@ void dev_seq_stop(struct seq_file *seq, void *v)
 
 static void dev_seq_printf_stats(struct seq_file *seq, struct net_device *dev)
 {
-        if (dev->get_stats) {
-                struct net_device_stats *stats = dev->get_stats(dev);
+        struct net_device_stats *stats = dev->get_stats(dev);
 
+        if (stats) {
                 seq_printf(seq, "%6s:%8lu %7lu %4lu %4lu %4lu %5lu %10lu %9lu "
                                 "%8lu %7lu %4lu %4lu %4lu %5lu %7lu %10lu\n",
                            dev->name, stats->rx_bytes, stats->rx_packets,
@@ -3282,6 +3281,13 @@ out:
         mutex_unlock(&net_todo_run_mutex);
 }
 
+static struct net_device_stats *maybe_internal_stats(struct net_device *dev)
+{
+        if (dev->features & NETIF_F_INTERNAL_STATS)
+                return &dev->stats;
+        return NULL;
+}
+
 /**
  *      alloc_netdev - allocate network device
  *      @sizeof_priv:   size of private data to allocate space for
@@ -3317,6 +3323,7 @@ struct net_device *alloc_netdev(int sizeof_priv, const char *name,
         if (sizeof_priv)
                 dev->priv = netdev_priv(dev);
 
+        dev->get_stats = maybe_internal_stats;
         setup(dev);
         strcpy(dev->name, name);
         return dev;