net: add sysfs attribute to control napi threaded mode

this patch addis a new sysfs attribute to the network
device class. Said attribute is a bitmask that allows controlling
the threaded mode for all the napi instances of the given
network device.

The threaded mode can be switched only if related network device
is down.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>

2 files changed, 54 insertions, 0 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index fa40bdc0e2c45..9e8a886ab8be0 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1961,6 +1961,7 @@ struct net_device {
 	spinlock_t		addr_list_lock;
 	unsigned char		name_assign_type;
 	bool			uc_promisc;
+	bool			napi_threaded;
 	struct netdev_hw_addr_list	uc;
 	struct netdev_hw_addr_list	mc;
 	struct netdev_hw_addr_list	dev_addrs;
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 7bd6440c63bf5..9c97cdb09f308 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -537,6 +537,58 @@ static ssize_t phys_switch_id_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(phys_switch_id);
 
+static ssize_t threaded_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct net_device *netdev = to_net_dev(dev);
+	size_t count = 0;
+
+	if (!rtnl_trylock())
+		return restart_syscall();
+
+	if (dev_isalive(netdev))
+		count = snprintf(buf, PAGE_SIZE, "%u\n", netdev->napi_threaded);
+	rtnl_unlock();
+
+	return count;
+}
+
+static ssize_t threaded_store(struct device *dev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t len)
+{
+	struct net_device *netdev = to_net_dev(dev);
+	size_t ret;
+	bool val;
+
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	if (!rtnl_trylock())
+		return restart_syscall();
+
+	if (!dev_isalive(netdev)) {
+		ret = len;
+		goto unlock;
+	}
+
+	if (netdev->flags & IFF_UP) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	ret = kstrtobool(buf, &val);
+	if (ret < 0)
+		goto unlock;
+	netdev->napi_threaded = val;
+	ret = len;
+
+unlock:
+	rtnl_unlock();
+	return ret;
+}
+static DEVICE_ATTR_RW(threaded);
+
 static struct attribute *net_class_attrs[] __ro_after_init = {
 	&dev_attr_netdev_group.attr,
 	&dev_attr_type.attr,
@@ -569,6 +621,7 @@ static struct attribute *net_class_attrs[] __ro_after_init = {
 	&dev_attr_proto_down.attr,
 	&dev_attr_carrier_up_count.attr,
 	&dev_attr_carrier_down_count.attr,
+	&dev_attr_threaded.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(net_class);