neighbour: Remove bare neighbour::next pointer

Remove the now-unused neighbour::next pointer, leaving struct neighbour
solely with the hlist_node implementation.

Signed-off-by: Gilad Naaman <gnaaman@drivenets.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241107160444.2913124-6-gnaaman@drivenets.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 11 insertions, 81 deletions

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index f99354d768c2..59f359c7b5e3 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -204,18 +204,12 @@ static void neigh_update_flags(struct neighbour *neigh, u32 flags, int *notify,
 	}
 }
 
-static bool neigh_del(struct neighbour *n, struct neighbour __rcu **np,
-		      struct neigh_table *tbl)
+bool neigh_remove_one(struct neighbour *n)
 {
 	bool retval = false;
 
 	write_lock(&n->lock);
 	if (refcount_read(&n->refcnt) == 1) {
-		struct neighbour *neigh;
-
-		neigh = rcu_dereference_protected(n->next,
-						  lockdep_is_held(&tbl->lock));
-		rcu_assign_pointer(*np, neigh);
 		hlist_del_rcu(&n->hash);
 		neigh_mark_dead(n);
 		retval = true;
@@ -226,29 +220,6 @@ static bool neigh_del(struct neighbour *n, struct neighbour __rcu **np,
 	return retval;
 }
 
-bool neigh_remove_one(struct neighbour *ndel, struct neigh_table *tbl)
-{
-	struct neigh_hash_table *nht;
-	void *pkey = ndel->primary_key;
-	u32 hash_val;
-	struct neighbour *n;
-	struct neighbour __rcu **np;
-
-	nht = rcu_dereference_protected(tbl->nht,
-					lockdep_is_held(&tbl->lock));
-	hash_val = tbl->hash(pkey, ndel->dev, nht->hash_rnd);
-	hash_val = hash_val >> (32 - nht->hash_shift);
-
-	np = &nht->hash_buckets[hash_val];
-	while ((n = rcu_dereference_protected(*np,
-					      lockdep_is_held(&tbl->lock)))) {
-		if (n == ndel)
-			return neigh_del(n, np, tbl);
-		np = &n->next;
-	}
-	return false;
-}
-
 static int neigh_forced_gc(struct neigh_table *tbl)
 {
 	int max_clean = atomic_read(&tbl->gc_entries) -
@@ -276,7 +247,7 @@ static int neigh_forced_gc(struct neigh_table *tbl)
 				remove = true;
 			write_unlock(&n->lock);
 
-			if (remove && neigh_remove_one(n, tbl))
+			if (remove && neigh_remove_one(n))
 				shrunk++;
 			if (shrunk >= max_clean)
 				break;
@@ -387,22 +358,15 @@ static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev,
 					lockdep_is_held(&tbl->lock));
 
 	for (i = 0; i < (1 << nht->hash_shift); i++) {
-		struct neighbour __rcu **np = &nht->hash_buckets[i];
 		struct hlist_node *tmp;
 		struct neighbour *n;
 
 		neigh_for_each_in_bucket_safe(n, tmp, &nht->hash_heads[i]) {
-			if (dev && n->dev != dev) {
-				np = &n->next;
+			if (dev && n->dev != dev)
 				continue;
-			}
-			if (skip_perm && n->nud_state & NUD_PERMANENT) {
-				np = &n->next;
+			if (skip_perm && n->nud_state & NUD_PERMANENT)
 				continue;
-			}
-			rcu_assign_pointer(*np,
-				   rcu_dereference_protected(n->next,
-						lockdep_is_held(&tbl->lock)));
+
 			hlist_del_rcu(&n->hash);
 			write_lock(&n->lock);
 			neigh_del_timer(n);
@@ -531,9 +495,7 @@ static void neigh_get_hash_rnd(u32 *x)
 
 static struct neigh_hash_table *neigh_hash_alloc(unsigned int shift)
 {
-	size_t hash_heads_size = (1 << shift) * sizeof(struct hlist_head);
-	size_t size = (1 << shift) * sizeof(struct neighbour *);
-	struct neighbour __rcu **buckets;
+	size_t size = (1 << shift) * sizeof(struct hlist_head);
 	struct hlist_head *hash_heads;
 	struct neigh_hash_table *ret;
 	int i;
@@ -542,18 +504,11 @@ static struct neigh_hash_table *neigh_hash_alloc(unsigned int shift)
 	if (!ret)
 		return NULL;
 
-	buckets = kvzalloc(size, GFP_ATOMIC);
-	if (!buckets) {
-		kfree(ret);
-		return NULL;
-	}
-	hash_heads = kvzalloc(hash_heads_size, GFP_ATOMIC);
+	hash_heads = kvzalloc(size, GFP_ATOMIC);
 	if (!hash_heads) {
-		kvfree(buckets);
 		kfree(ret);
 		return NULL;
 	}
-	ret->hash_buckets = buckets;
 	ret->hash_heads = hash_heads;
 	ret->hash_shift = shift;
 	for (i = 0; i < NEIGH_NUM_HASH_RND; i++)
@@ -567,7 +522,6 @@ static void neigh_hash_free_rcu(struct rcu_head *head)
 						    struct neigh_hash_table,
 						    rcu);
 
-	kvfree(nht->hash_buckets);
 	kvfree(nht->hash_heads);
 	kfree(nht);
 }
@@ -596,11 +550,6 @@ static struct neigh_hash_table *neigh_hash_grow(struct neigh_table *tbl,
 
 			hash >>= (32 - new_nht->hash_shift);
 
-			rcu_assign_pointer(n->next,
-					   rcu_dereference_protected(
-						new_nht->hash_buckets[hash],
-						lockdep_is_held(&tbl->lock)));
-			rcu_assign_pointer(new_nht->hash_buckets[hash], n);
 			hlist_del_rcu(&n->hash);
 			hlist_add_head_rcu(&n->hash, &new_nht->hash_heads[hash]);
 		}
@@ -705,10 +654,6 @@ ___neigh_create(struct neigh_table *tbl, const void *pkey,
 		list_add_tail(&n->managed_list, &n->tbl->managed_list);
 	if (want_ref)
 		neigh_hold(n);
-	rcu_assign_pointer(n->next,
-			   rcu_dereference_protected(nht->hash_buckets[hash_val],
-						     lockdep_is_held(&tbl->lock)));
-	rcu_assign_pointer(nht->hash_buckets[hash_val], n);
 	hlist_add_head_rcu(&n->hash, &nht->hash_heads[hash_val]);
 	write_unlock_bh(&tbl->lock);
 	neigh_dbg(2, "neigh %p is created\n", n);
@@ -942,7 +887,6 @@ static void neigh_periodic_work(struct work_struct *work)
 {
 	struct neigh_table *tbl = container_of(work, struct neigh_table, gc_work.work);
 	struct neigh_hash_table *nht;
-	struct neighbour __rcu **np;
 	struct hlist_node *tmp;
 	struct neighbour *n;
 	unsigned int i;
@@ -970,8 +914,6 @@ static void neigh_periodic_work(struct work_struct *work)
 		goto out;
 
 	for (i = 0 ; i < (1 << nht->hash_shift); i++) {
-		np = &nht->hash_buckets[i];
-
 		neigh_for_each_in_bucket_safe(n, tmp, &nht->hash_heads[i]) {
 			unsigned int state;
 
@@ -981,7 +923,7 @@ static void neigh_periodic_work(struct work_struct *work)
 			if ((state & (NUD_PERMANENT | NUD_IN_TIMER)) ||
 			    (n->flags & NTF_EXT_LEARNED)) {
 				write_unlock(&n->lock);
-				goto next_elt;
+				continue;
 			}
 
 			if (time_before(n->used, n->confirmed) &&
@@ -992,9 +934,6 @@ static void neigh_periodic_work(struct work_struct *work)
 			    (state == NUD_FAILED ||
 			     !time_in_range_open(jiffies, n->used,
 						 n->used + NEIGH_VAR(n->parms, GC_STALETIME)))) {
-				rcu_assign_pointer(*np,
-					rcu_dereference_protected(n->next,
-						lockdep_is_held(&tbl->lock)));
 				hlist_del_rcu(&n->hash);
 				neigh_mark_dead(n);
 				write_unlock(&n->lock);
@@ -1002,9 +941,6 @@ static void neigh_periodic_work(struct work_struct *work)
 				continue;
 			}
 			write_unlock(&n->lock);
-
-next_elt:
-			np = &n->next;
 		}
 		/*
 		 * It's fine to release lock here, even if hash table
@@ -1951,7 +1887,7 @@ static int neigh_delete(struct sk_buff *skb, struct nlmsghdr *nlh,
 			     NETLINK_CB(skb).portid, extack);
 	write_lock_bh(&tbl->lock);
 	neigh_release(neigh);
-	neigh_remove_one(neigh, tbl);
+	neigh_remove_one(neigh);
 	write_unlock_bh(&tbl->lock);
 
 out:
@@ -3108,24 +3044,18 @@ void __neigh_for_each_release(struct neigh_table *tbl,
 	nht = rcu_dereference_protected(tbl->nht,
 					lockdep_is_held(&tbl->lock));
 	for (chain = 0; chain < (1 << nht->hash_shift); chain++) {
-		struct neighbour __rcu **np;
 		struct hlist_node *tmp;
 		struct neighbour *n;
 
-		np = &nht->hash_buckets[chain];
 		neigh_for_each_in_bucket_safe(n, tmp, &nht->hash_heads[chain]) {
 			int release;
 
 			write_lock(&n->lock);
 			release = cb(n);
 			if (release) {
-				rcu_assign_pointer(*np,
-					rcu_dereference_protected(n->next,
-						lockdep_is_held(&tbl->lock)));
 				hlist_del_rcu(&n->hash);
 				neigh_mark_dead(n);
-			} else
-				np = &n->next;
+			}
 			write_unlock(&n->lock);
 			if (release)
 				neigh_cleanup_and_release(n);
diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 11c1519b3699..cb9a7ed8abd3 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1215,7 +1215,7 @@ int arp_invalidate(struct net_device *dev, __be32 ip, bool force)
 					   NEIGH_UPDATE_F_ADMIN, 0);
 		write_lock_bh(&tbl->lock);
 		neigh_release(neigh);
-		neigh_remove_one(neigh, tbl);
+		neigh_remove_one(neigh);
 		write_unlock_bh(&tbl->lock);
 	}