[PATCH v3 2/2] net: add sysfs attribute for enabling threaded NAPI

[Felix Fietkau]

This can be used to enable threaded NAPI on drivers that did not explicitly
request it.

Suggested-by: Eric Dumazet <eric.duma...@gmail.com>
Signed-off-by: Felix Fietkau <n...@nbd.name>
---
 net/core/net-sysfs.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index efec66fa78b7..d7f7df715b60 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -472,6 +472,52 @@ static ssize_t proto_down_store(struct device *dev,
 }
 NETDEVICE_SHOW_RW(proto_down, fmt_dec);
 
+static int change_napi_threaded(struct net_device *dev, unsigned long val)
+{
+       struct napi_struct *napi;
+
+       if (list_empty(&dev->napi_list))
+               return -EOPNOTSUPP;
+
+       list_for_each_entry(napi, &dev->napi_list, dev_list) {
+               if (val)
+                       set_bit(NAPI_STATE_THREADED, &napi->state);
+               else
+                       clear_bit(NAPI_STATE_THREADED, &napi->state);
+       }
+
+       return 0;
+}
+
+static ssize_t napi_threaded_store(struct device *dev,
+                               struct device_attribute *attr,
+                               const char *buf, size_t len)
+{
+       return netdev_store(dev, attr, buf, len, change_napi_threaded);
+}
+
+static ssize_t napi_threaded_show(struct device *dev,
+                                 struct device_attribute *attr,
+                                 char *buf)
+{
+       struct net_device *netdev = to_net_dev(dev);
+       struct napi_struct *napi;
+       bool enabled = false;
+
+       if (!rtnl_trylock())
+               return restart_syscall();
+
+       list_for_each_entry(napi, &netdev->napi_list, dev_list) {
+               if (test_bit(NAPI_STATE_THREADED, &napi->state))
+                       enabled = true;
+       }
+
+       rtnl_unlock();
+
+       return sprintf(buf, fmt_dec, enabled);
+}
+static DEVICE_ATTR_RW(napi_threaded);
+
 static ssize_t phys_port_id_show(struct device *dev,
                                 struct device_attribute *attr, char *buf)
 {
@@ -564,6 +610,7 @@ static struct attribute *net_class_attrs[] __ro_after_init 
= {
        &dev_attr_tx_queue_len.attr,
        &dev_attr_gro_flush_timeout.attr,
        &dev_attr_napi_defer_hard_irqs.attr,
+       &dev_attr_napi_threaded.attr,
        &dev_attr_phys_port_id.attr,
        &dev_attr_phys_port_name.attr,
        &dev_attr_phys_switch_id.attr,
-- 
2.28.0