[PATCH net-next v4 5/6] Remove bare neighbour::next pointer

[Gilad Naaman <gnaaman@drivenets.com>]

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

Signed-off-by: Gilad Naaman <gnaaman@drivenets.com>
---
 include/net/neighbour.h |   2 -
 net/core/neighbour.c    | 128 ++++++++--------------------------------
 2 files changed, 24 insertions(+), 106 deletions(-)

diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index c0c35a15d2ad..21c0c20a0ed5 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -135,7 +135,6 @@ struct neigh_statistics {
 #define NEIGH_CACHE_STAT_INC(tbl, field) this_cpu_inc((tbl)->stats->field)
 
 struct neighbour {
-	struct neighbour __rcu	*next;
 	struct hlist_node	hash;
 	struct neigh_table	*tbl;
 	struct neigh_parms	*parms;
@@ -191,7 +190,6 @@ struct pneigh_entry {
 #define NEIGH_NUM_HASH_RND	4
 
 struct neigh_hash_table {
-	struct neighbour __rcu	**hash_buckets;
 	struct hlist_head	*hash_heads;
 	unsigned int		hash_shift;
 	__u32			hash_rnd[NEIGH_NUM_HASH_RND];
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index cca524a55c97..61b5f0d4896a 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -205,49 +205,24 @@ 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 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;
-	}
-	write_unlock(&n->lock);
-	if (retval)
-		neigh_cleanup_and_release(n);
-	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;
+	bool retval = false;
 
 	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;
+	write_lock(&ndel->lock);
+	if (refcount_read(&ndel->refcnt) == 1) {
+		hlist_del_rcu(&ndel->hash);
+		neigh_mark_dead(ndel);
+		retval = true;
 	}
-	return false;
+	write_unlock(&ndel->lock);
+	if (retval)
+		neigh_cleanup_and_release(ndel);
+	return retval;
 }
 
 static int neigh_forced_gc(struct neigh_table *tbl)
@@ -389,20 +364,13 @@ static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev,
 
 	for (i = 0; i < (1 << nht->hash_shift); i++) {
 		struct neighbour *n;
-		struct neighbour __rcu **np = &nht->hash_buckets[i];
 
 		neigh_for_each(n, &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);
@@ -426,7 +394,6 @@ static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev,
 					n->nud_state = NUD_NONE;
 				neigh_dbg(2, "neigh %p is stray\n", n);
 			}
-			np = &n->next;
 			write_unlock(&n->lock);
 			neigh_cleanup_and_release(n);
 		}
@@ -532,39 +499,26 @@ static void neigh_get_hash_rnd(u32 *x)
 
 static struct neigh_hash_table *neigh_hash_alloc(unsigned int shift)
 {
-	size_t size = (1 << shift) * sizeof(struct neighbour *);
-	size_t hash_heads_size = (1 << shift) * sizeof(struct hlist_head);
+	size_t size = (1 << shift) * sizeof(struct hlist_head);
 	struct neigh_hash_table *ret;
 	struct hlist_head *hash_heads;
-	struct neighbour __rcu **buckets;
 	int i;
 
 	ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
 	if (!ret)
 		return NULL;
 	if (size <= PAGE_SIZE) {
-		buckets = kzalloc(size, GFP_ATOMIC);
-		hash_heads = kzalloc(hash_heads_size, GFP_ATOMIC);
-		if (!hash_heads)
-			kfree(buckets);
+		hash_heads = kzalloc(size, GFP_ATOMIC);
 	} else {
-		buckets = (struct neighbour __rcu **)
-			  __get_free_pages(GFP_ATOMIC | __GFP_ZERO,
-					   get_order(size));
-		kmemleak_alloc(buckets, size, 1, GFP_ATOMIC);
-
 		hash_heads = (struct hlist_head *)
 			  __get_free_pages(GFP_ATOMIC | __GFP_ZERO,
-					   get_order(hash_heads_size));
-		kmemleak_alloc(hash_heads, hash_heads_size, 1, GFP_ATOMIC);
-		if (!hash_heads)
-			free_pages((unsigned long)buckets, get_order(size));
+					   get_order(size));
+		kmemleak_alloc(hash_heads, size, 1, GFP_ATOMIC);
 	}
-	if (!buckets || !hash_heads) {
+	if (!hash_heads) {
 		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++)
@@ -577,23 +531,14 @@ static void neigh_hash_free_rcu(struct rcu_head *head)
 	struct neigh_hash_table *nht = container_of(head,
 						    struct neigh_hash_table,
 						    rcu);
-	size_t size = (1 << nht->hash_shift) * sizeof(struct neighbour *);
-	struct neighbour __rcu **buckets = nht->hash_buckets;
-	size_t hash_heads_size = (1 << nht->hash_shift) * sizeof(struct hlist_head);
+	size_t size = (1 << nht->hash_shift) * sizeof(struct hlist_head);
 	struct hlist_head *hash_heads = nht->hash_heads;
 
-	if (size <= PAGE_SIZE) {
-		kfree(buckets);
-	} else {
-		kmemleak_free(buckets);
-		free_pages((unsigned long)buckets, get_order(size));
-	}
-
-	if (hash_heads_size < PAGE_SIZE) {
+	if (size < PAGE_SIZE) {
 		kfree(hash_heads);
 	} else {
 		kmemleak_free(hash_heads);
-		free_pages((unsigned long)hash_heads, get_order(hash_heads_size));
+		free_pages((unsigned long)hash_heads, get_order(size));
 	}
 	kfree(nht);
 }
@@ -613,7 +558,7 @@ static struct neigh_hash_table *neigh_hash_grow(struct neigh_table *tbl,
 		return old_nht;
 
 	for (i = 0; i < (1 << old_nht->hash_shift); i++) {
-		struct neighbour *n, *next;
+		struct neighbour *n;
 		struct hlist_node *tmp;
 
 		neigh_for_each_safe(n, tmp, &old_nht->hash_heads[i]) {
@@ -621,14 +566,7 @@ static struct neigh_hash_table *neigh_hash_grow(struct neigh_table *tbl,
 					 new_nht->hash_rnd);
 
 			hash >>= (32 - new_nht->hash_shift);
-			next = rcu_dereference_protected(n->next,
-						lockdep_is_held(&tbl->lock));
 
-			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]);
 		}
@@ -733,10 +671,6 @@ ___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);
@@ -971,7 +905,6 @@ static void neigh_periodic_work(struct work_struct *work)
 	struct neigh_table *tbl = container_of(work, struct neigh_table, gc_work.work);
 	struct neighbour *n;
 	struct hlist_node *tmp;
-	struct neighbour __rcu **np;
 	unsigned int i;
 	struct neigh_hash_table *nht;
 
@@ -998,7 +931,6 @@ 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_safe(n, tmp, &nht->hash_heads[i]) {
 			unsigned int state;
@@ -1009,7 +941,7 @@ 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) &&
@@ -1020,9 +952,6 @@ 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);
@@ -1030,9 +959,6 @@ 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
@@ -3118,22 +3044,16 @@ void __neigh_for_each_release(struct neigh_table *tbl,
 	for (chain = 0; chain < (1 << nht->hash_shift); chain++) {
 		struct neighbour *n;
 		struct hlist_node *tmp;
-		struct neighbour __rcu **np;
 
-		np = &nht->hash_buckets[chain];
 		neigh_for_each_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);
-- 
2.46.0