neighbour: Drop read_lock_bh(&tbl->lock) in pneigh_lookup().

Now, all callers of pneigh_lookup() are under RCU, and the read
lock there is no longer needed.

Let's drop the lock, inline __pneigh_lookup_1() to pneigh_lookup(),
and call it from pneigh_create().

The next patch will remove tbl->lock from pneigh_create().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250716221221.442239-14-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index e7bd8111f97f4b0590988a93ab58714e0a137760..38f0067068c5652448cc7e607168b873aa5ebc73 100644 (file)
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -720,23 +720,6 @@ static u32 pneigh_hash(const void *pkey, unsigned int key_len)
        return hash_val;
 }
 
-static struct pneigh_entry *__pneigh_lookup_1(struct pneigh_entry *n,
-                                             struct net *net,
-                                             const void *pkey,
-                                             unsigned int key_len,
-                                             struct net_device *dev)
-{
-       while (n) {
-               if (!memcmp(n->key, pkey, key_len) &&
-                   net_eq(pneigh_net(n), net) &&
-                   (n->dev == dev || !n->dev))
-                       return n;
-
-               n = rcu_dereference_protected(n->next, 1);
-       }
-       return NULL;
-}
-
 struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl,
                                   struct net *net, const void *pkey,
                                   struct net_device *dev)
@@ -747,13 +730,19 @@ struct pneigh_entry *pneigh_lookup(struct neigh_table *tbl,
 
        key_len = tbl->key_len;
        hash_val = pneigh_hash(pkey, key_len);
+       n = rcu_dereference_check(tbl->phash_buckets[hash_val],
+                                 lockdep_is_held(&tbl->lock));
 
-       read_lock_bh(&tbl->lock);
-       n = __pneigh_lookup_1(rcu_dereference_protected(tbl->phash_buckets[hash_val], 1),
-                             net, pkey, key_len, dev);
-       read_unlock_bh(&tbl->lock);
+       while (n) {
+               if (!memcmp(n->key, pkey, key_len) &&
+                   net_eq(pneigh_net(n), net) &&
+                   (n->dev == dev || !n->dev))
+                       return n;
 
-       return n;
+               n = rcu_dereference_check(n->next, lockdep_is_held(&tbl->lock));
+       }
+
+       return NULL;
 }
 EXPORT_IPV6_MOD(pneigh_lookup);
 
@@ -762,19 +751,18 @@ struct pneigh_entry *pneigh_create(struct neigh_table *tbl,
                                   struct net_device *dev)
 {
        struct pneigh_entry *n;
-       unsigned int key_len = tbl->key_len;
-       u32 hash_val = pneigh_hash(pkey, key_len);
+       unsigned int key_len;
+       u32 hash_val;
 
        ASSERT_RTNL();
 
        read_lock_bh(&tbl->lock);
-       n = __pneigh_lookup_1(rcu_dereference_protected(tbl->phash_buckets[hash_val], 1),
-                             net, pkey, key_len, dev);
+       n = pneigh_lookup(tbl, net, pkey, dev);
        read_unlock_bh(&tbl->lock);
-
        if (n)
                goto out;
 
+       key_len = tbl->key_len;
        n = kzalloc(sizeof(*n) + key_len, GFP_KERNEL);
        if (!n)
                goto out;
@@ -791,6 +779,7 @@ struct pneigh_entry *pneigh_create(struct neigh_table *tbl,
                goto out;
        }
 
+       hash_val = pneigh_hash(pkey, key_len);
        write_lock_bh(&tbl->lock);
        n->next = tbl->phash_buckets[hash_val];
        rcu_assign_pointer(tbl->phash_buckets[hash_val], n);