ethtool: runtime-resume netdev parent before ethtool ioctl ops

If a network device is runtime-suspended then:
- network device may be flagged as detached and all ethtool ops (even if not
  accessing the device) will fail because netif_device_present() returns
  false
- ethtool ops may fail because device is not accessible (e.g. because being
  in D3 in case of a PCI device)

It may not be desirable that userspace can't use even simple ethtool ops
that not access the device if interface or link is down. To be more friendly
to userspace let's ensure that device is runtime-resumed when executing the
respective ethtool op in kernel.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ethtool/ioctl.c

@@ -24,6 +24,7 @@
 #include <linux/rtnetlink.h>
 #include <linux/sched/signal.h>
 #include <linux/net.h>
+#include <linux/pm_runtime.h>
 #include <net/devlink.h>
 #include <net/xdp_sock_drv.h>
 #include <net/flow_offload.h>
@@ -2692,7 +2693,7 @@ int dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr)
 	int rc;
 	netdev_features_t old_features;
 
-	if (!dev || !netif_device_present(dev))
+	if (!dev)
 		return -ENODEV;
 
 	if (copy_from_user(&ethcmd, useraddr, sizeof(ethcmd)))
@@ -2748,10 +2749,18 @@ int dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr)
 			return -EPERM;
 	}
 
+	if (dev->dev.parent)
+		pm_runtime_get_sync(dev->dev.parent);
+
+	if (!netif_device_present(dev)) {
+		rc = -ENODEV;
+		goto out;
+	}
+
 	if (dev->ethtool_ops->begin) {
 		rc = dev->ethtool_ops->begin(dev);
 		if (rc < 0)
-			return rc;
+			goto out;
 	}
 	old_features = dev->features;
 
@@ -2970,6 +2979,9 @@ int dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr)
 
 	if (old_features != dev->features)
 		netdev_features_change(dev);
+out:
+	if (dev->dev.parent)
+		pm_runtime_put(dev->dev.parent);
 
 	return rc;
 }