net: gro: decouple GRO from the NAPI layer

In fact, these two are not tied closely to each other. The only
requirements to GRO are to use it in the BH context and have some
sane limits on the packet batches, e.g. NAPI has a limit of its
budget (64/8/etc.).
Move purely GRO fields into a new structure, &gro_node. Embed it
into &napi_struct and adjust all the references.
gro_node::cached_napi_id is effectively the same as
napi_struct::napi_id, but to be used on GRO hotpath to mark skbs.
napi_struct::napi_id is now a fully control path field.

Three Ethernet drivers use napi_gro_flush() not really meant to be
exported, so move it to <net/gro.h> and add that include there.
napi_gro_receive() is used in more than 100 drivers, keep it
in <linux/netdevice.h>.
This does not make GRO ready to use outside of the NAPI context
yet.

Tested-by: Daniel Xu <dxu@dxuuu.xyz>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 28 insertions, 9 deletions

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 2094d3edda73..26a0c4e4d963 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -340,11 +340,27 @@ struct gro_list {
 };
 
 /*
- * size of gro hash buckets, must less than bit number of
- * napi_struct::gro_bitmask
+ * size of gro hash buckets, must be <= the number of bits in
+ * gro_node::bitmask
  */
 #define GRO_HASH_BUCKETS	8
 
+/**
+ * struct gro_node - structure to support Generic Receive Offload
+ * @bitmask: bitmask to indicate used buckets in @hash
+ * @hash: hashtable of pending aggregated skbs, separated by flows
+ * @rx_list: list of pending ``GRO_NORMAL`` skbs
+ * @rx_count: cached current length of @rx_list
+ * @cached_napi_id: napi_struct::napi_id cached for hotpath, 0 for standalone
+ */
+struct gro_node {
+	unsigned long		bitmask;
+	struct gro_list		hash[GRO_HASH_BUCKETS];
+	struct list_head	rx_list;
+	u32			rx_count;
+	u32			cached_napi_id;
+};
+
 /*
  * Structure for per-NAPI config
  */
@@ -371,7 +387,6 @@ struct napi_struct {
 	unsigned long		state;
 	int			weight;
 	u32			defer_hard_irqs_count;
-	unsigned long		gro_bitmask;
 	int			(*poll)(struct napi_struct *, int);
 #ifdef CONFIG_NETPOLL
 	/* CPU actively polling if netpoll is configured */
@@ -380,11 +395,8 @@ struct napi_struct {
 	/* CPU on which NAPI has been scheduled for processing */
 	int			list_owner;
 	struct net_device	*dev;
-	struct gro_list		gro_hash[GRO_HASH_BUCKETS];
 	struct sk_buff		*skb;
-	struct list_head	rx_list; /* Pending GRO_NORMAL skbs */
-	int			rx_count; /* length of rx_list */
-	unsigned int		napi_id; /* protected by netdev_lock */
+	struct gro_node		gro;
 	struct hrtimer		timer;
 	/* all fields past this point are write-protected by netdev_lock */
 	struct task_struct	*thread;
@@ -392,6 +404,7 @@ struct napi_struct {
 	unsigned long		irq_suspend_timeout;
 	u32			defer_hard_irqs;
 	/* control-path-only fields follow */
+	u32			napi_id;
 	struct list_head	dev_list;
 	struct hlist_node	napi_hash_node;
 	int			irq;
@@ -4131,8 +4144,14 @@ int netif_receive_skb(struct sk_buff *skb);
 int netif_receive_skb_core(struct sk_buff *skb);
 void netif_receive_skb_list_internal(struct list_head *head);
 void netif_receive_skb_list(struct list_head *head);
-gro_result_t napi_gro_receive(struct napi_struct *napi, struct sk_buff *skb);
-void napi_gro_flush(struct napi_struct *napi, bool flush_old);
+gro_result_t gro_receive_skb(struct gro_node *gro, struct sk_buff *skb);
+
+static inline gro_result_t napi_gro_receive(struct napi_struct *napi,
+					    struct sk_buff *skb)
+{
+	return gro_receive_skb(&napi->gro, skb);
+}
+
 struct sk_buff *napi_get_frags(struct napi_struct *napi);
 gro_result_t napi_gro_frags(struct napi_struct *napi);