net neigh: RCU conversion of neigh hash table

David

This is the first step for RCU conversion of neigh code.

Next patches will convert hash_buckets[] and "struct neighbour" to RCU
protected objects.

Thanks

[PATCH net-next] net neigh: RCU conversion of neigh hash table

Instead of storing hash_buckets, hash_mask and hash_rnd in "struct
neigh_table", a new structure is defined :

struct neigh_hash_table {
       struct neighbour        **hash_buckets;
       unsigned int            hash_mask;
       __u32                   hash_rnd;
       struct rcu_head         rcu;
};

And "struct neigh_table" has an RCU protected pointer to such a
neigh_hash_table.

This means the signature of (*hash)() function changed: We need to add a
third parameter with the actual hash_rnd value, since this is not
anymore a neigh_table field.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/neighbour.h

@@ -138,13 +138,22 @@ struct pneigh_entry {
  *	neighbour table manipulation
  */
 
+struct neigh_hash_table {
+	struct neighbour	**hash_buckets;
+	unsigned int		hash_mask;
+	__u32			hash_rnd;
+	struct rcu_head		rcu;
+};
+
 
 struct neigh_table {
 	struct neigh_table	*next;
 	int			family;
 	int			entry_size;
 	int			key_len;
-	__u32			(*hash)(const void *pkey, const struct net_device *);
+	__u32			(*hash)(const void *pkey,
+					const struct net_device *dev,
+					__u32 hash_rnd);
 	int			(*constructor)(struct neighbour *);
 	int			(*pconstructor)(struct pneigh_entry *);
 	void			(*pdestructor)(struct pneigh_entry *);
@@ -165,9 +174,7 @@ struct neigh_table {
 	unsigned long		last_rand;
 	struct kmem_cache	*kmem_cachep;
 	struct neigh_statistics	__percpu *stats;
-	struct neighbour	**hash_buckets;
-	unsigned int		hash_mask;
-	__u32			hash_rnd;
+	struct neigh_hash_table __rcu *nht;
 	struct pneigh_entry	**phash_buckets;
 };
 
@@ -237,6 +244,7 @@ extern void pneigh_for_each(struct neigh_table *tbl, void (*cb)(struct pneigh_en
 struct neigh_seq_state {
 	struct seq_net_private p;
 	struct neigh_table *tbl;
+	struct neigh_hash_table *nht;
 	void *(*neigh_sub_iter)(struct neigh_seq_state *state,
 				struct neighbour *n, loff_t *pos);
 	unsigned int bucket;

net/atm/clip.c

@@ -310,9 +310,9 @@ static int clip_constructor(struct neighbour *neigh)
 	return 0;
 }
 
-static u32 clip_hash(const void *pkey, const struct net_device *dev)
+static u32 clip_hash(const void *pkey, const struct net_device *dev, __u32 rnd)
 {
-	return jhash_2words(*(u32 *) pkey, dev->ifindex, clip_tbl.hash_rnd);
+	return jhash_2words(*(u32 *) pkey, dev->ifindex, rnd);
 }
 
 static struct neigh_table clip_tbl = {