netdev: reshuffle netif_napi_add() APIs to allow dropping weight

Most drivers should not have to worry about selecting the right
weight for their NAPI instances and pass NAPI_POLL_WEIGHT.
It'd be best if we didn't require the argument at all and selected
the default internally.

This change prepares the ground for such reshuffling, allowing
for a smooth transition. The following API should remain after
the next release cycle:
  netif_napi_add()
  netif_napi_add_weight()
  netif_napi_add_tx()
  netif_napi_add_tx_weight()
Where the _weight() variants take an explicit weight argument.
I opted for a _weight() suffix rather than a __ prefix, because
we use __ in places to mean that caller needs to also issue a
synchronize_net() call.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20220502232703.396351-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/netdevice.h

@@ -2499,37 +2499,53 @@ static inline void *netdev_priv(const struct net_device *dev)
  */
 #define NAPI_POLL_WEIGHT 64
 
+void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
+			   int (*poll)(struct napi_struct *, int), int weight);
+
 /**
- *	netif_napi_add - initialize a NAPI context
- *	@dev:  network device
- *	@napi: NAPI context
- *	@poll: polling function
- *	@weight: default weight
+ * netif_napi_add() - initialize a NAPI context
+ * @dev:  network device
+ * @napi: NAPI context
+ * @poll: polling function
+ * @weight: default weight
  *
  * netif_napi_add() must be used to initialize a NAPI context prior to calling
  * *any* of the other NAPI-related functions.
  */
-void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
-		    int (*poll)(struct napi_struct *, int), int weight);
+static inline void
+netif_napi_add(struct net_device *dev, struct napi_struct *napi,
+	       int (*poll)(struct napi_struct *, int), int weight)
+{
+	netif_napi_add_weight(dev, napi, poll, weight);
+}
+
+static inline void
+netif_napi_add_tx_weight(struct net_device *dev,
+			 struct napi_struct *napi,
+			 int (*poll)(struct napi_struct *, int),
+			 int weight)
+{
+	set_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state);
+	netif_napi_add_weight(dev, napi, poll, weight);
+}
+
+#define netif_tx_napi_add netif_napi_add_tx_weight
 
 /**
- *	netif_tx_napi_add - initialize a NAPI context
- *	@dev:  network device
- *	@napi: NAPI context
- *	@poll: polling function
- *	@weight: default weight
+ * netif_napi_add_tx() - initialize a NAPI context to be used for Tx only
+ * @dev:  network device
+ * @napi: NAPI context
+ * @poll: polling function
  *
  * This variant of netif_napi_add() should be used from drivers using NAPI
  * to exclusively poll a TX queue.
  * This will avoid we add it into napi_hash[], thus polluting this hash table.
  */
-static inline void netif_tx_napi_add(struct net_device *dev,
+static inline void netif_napi_add_tx(struct net_device *dev,
 				     struct napi_struct *napi,
-				     int (*poll)(struct napi_struct *, int),
-				     int weight)
+				     int (*poll)(struct napi_struct *, int))
 {
-	set_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state);
-	netif_napi_add(dev, napi, poll, weight);
+	netif_napi_add_tx_weight(dev, napi, poll, NAPI_POLL_WEIGHT);
 }
 
 /**

net/core/dev.c

@@ -6303,8 +6303,8 @@ int dev_set_threaded(struct net_device *dev, bool threaded)
 }
 EXPORT_SYMBOL(dev_set_threaded);
 
-void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
-		    int (*poll)(struct napi_struct *, int), int weight)
+void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
+			   int (*poll)(struct napi_struct *, int), int weight)
 {
 	if (WARN_ON(test_and_set_bit(NAPI_STATE_LISTED, &napi->state)))
 		return;
@@ -6337,7 +6337,7 @@ void netif_napi_add(struct net_device *dev, struct napi_struct *napi,
 	if (dev->threaded && napi_kthread_create(napi))
 		dev->threaded = 0;
 }
-EXPORT_SYMBOL(netif_napi_add);
+EXPORT_SYMBOL(netif_napi_add_weight);
 
 void napi_disable(struct napi_struct *n)
 {