neigh: RCU conversion of struct neighbour

This is the second step for neighbour RCU conversion.

(first was commit d6bf7817 : RCU conversion of neigh hash table)

neigh_lookup() becomes lockless, but still take a reference on found
neighbour. (no more read_lock()/read_unlock() on tbl->lock)

struct neighbour gets an additional rcu_head field and is freed after an
RCU grace period.

Future work would need to eventually not take a reference on neighbour
for temporary dst (DST_NOCACHE), but this would need dst->_neighbour to
use a noref bit like we did for skb->_dst.

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

1 files changed, 3 insertions, 2 deletions

diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 37845dae6488..a4538d553704 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -91,7 +91,7 @@ struct neigh_statistics {
 #define NEIGH_CACHE_STAT_INC(tbl, field) this_cpu_inc((tbl)->stats->field)
 
 struct neighbour {
-        struct neighbour        *next;
+        struct neighbour __rcu  *next;
         struct neigh_table      *tbl;
         struct neigh_parms      *parms;
         struct net_device       *dev;
@@ -111,6 +111,7 @@ struct neighbour {
         struct sk_buff_head     arp_queue;
         struct timer_list       timer;
         const struct neigh_ops  *ops;
+        struct rcu_head         rcu;
         u8                      primary_key[0];
 };
 
@@ -139,7 +140,7 @@ struct pneigh_entry {
  */
 
 struct neigh_hash_table {
-        struct neighbour        **hash_buckets;
+        struct neighbour __rcu  **hash_buckets;
         unsigned int            hash_mask;
         __u32                   hash_rnd;
         struct rcu_head         rcu;