Merge branch 'improve-neigh_flush_dev-performance'

Gilad Naaman says:

====================
Improve neigh_flush_dev performance

This patchsets improves the performance of neigh_flush_dev.

Currently, the only way to implement it requires traversing
all neighbours known to the kernel, across all network-namespaces.

This means that some flows are slowed down as a function of neigh-scale,
even if the specific link they're handling has little to no neighbours.

In order to solve this, this patchset adds a netdev->neighbours list,
as well as making the original linked-list doubly-, so that it is
possible to unlink neighbours without traversing the hash-bucket to
obtain the previous neighbour.

The original use-case we encountered was mass-deletion of links (12K
VLANs) while there are 50K ARPs and 50K NDPs in the system; though the
slowdowns would also appear when the links are set down.
====================

Link: https://patch.msgid.link/20241107160444.2913124-1-gnaaman@drivenets.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/net_cachelines/net_device.rst

@@ -188,4 +188,5 @@ u64                                 max_pacing_offload_horizon
 struct_napi_config*                 napi_config
 unsigned_long                       gro_flush_timeout
 u32                                 napi_defer_hard_irqs
+struct hlist_head                   neighbours[2]
 =================================== =========================== =================== =================== ===================================================================================

include/linux/netdevice.h

@@ -52,6 +52,7 @@
 #include <net/net_trackers.h>
 #include <net/net_debug.h>
 #include <net/dropreason-core.h>
+#include <net/neighbour_tables.h>
 
 struct netpoll_info;
 struct device;
@@ -2032,6 +2033,9 @@ enum netdev_reg_state {
  *	@napi_defer_hard_irqs:	If not zero, provides a counter that would
  *				allow to avoid NIC hard IRQ, on busy queues.
  *
+ *	@neighbours:	List heads pointing to this device's neighbours'
+ *			dev_list, one per address-family.
+ *
  *	FIXME: cleanup struct net_device such that network protocol info
  *	moves out.
  */
@@ -2440,6 +2444,9 @@ struct net_device {
 	 */
 	struct net_shaper_hierarchy *net_shaper_hierarchy;
 #endif
+
+	struct hlist_head neighbours[NEIGH_NR_TABLES];
+
 	u8			priv[] ____cacheline_aligned
 				       __counted_by(priv_len);
 } ____cacheline_aligned;

include/net/neighbour.h

@@ -29,6 +29,7 @@
 #include <linux/sysctl.h>
 #include <linux/workqueue.h>
 #include <net/rtnetlink.h>
+#include <net/neighbour_tables.h>
 
 /*
  * NUD stands for "neighbor unreachability detection"
@@ -135,7 +136,8 @@ 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 hlist_node	dev_list;
 	struct neigh_table	*tbl;
 	struct neigh_parms	*parms;
 	unsigned long		confirmed;
@@ -190,7 +192,7 @@ 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];
 	struct rcu_head		rcu;
@@ -236,13 +238,6 @@ struct neigh_table {
 	struct pneigh_entry	**phash_buckets;
 };
 
-enum {
-	NEIGH_ARP_TABLE = 0,
-	NEIGH_ND_TABLE = 1,
-	NEIGH_NR_TABLES,
-	NEIGH_LINK_TABLE = NEIGH_NR_TABLES /* Pseudo table for neigh_xmit */
-};
-
 static inline int neigh_parms_family(struct neigh_parms *p)
 {
 	return p->tbl->family;
@@ -275,6 +270,12 @@ static inline void *neighbour_priv(const struct neighbour *n)
 
 extern const struct nla_policy nda_policy[];
 
+#define neigh_for_each_in_bucket(pos, head) hlist_for_each_entry(pos, head, hash)
+#define neigh_for_each_in_bucket_rcu(pos, head) \
+	hlist_for_each_entry_rcu(pos, head, hash)
+#define neigh_for_each_in_bucket_safe(pos, tmp, head) \
+	hlist_for_each_entry_safe(pos, tmp, head, hash)
+
 static inline bool neigh_key_eq32(const struct neighbour *n, const void *pkey)
 {
 	return *(const u32 *)n->primary_key == *(const u32 *)pkey;
@@ -303,12 +304,9 @@ static inline struct neighbour *___neigh_lookup_noref(
 	u32 hash_val;
 
 	hash_val = hash(pkey, dev, nht->hash_rnd) >> (32 - nht->hash_shift);
-	for (n = rcu_dereference(nht->hash_buckets[hash_val]);
-	     n != NULL;
-	     n = rcu_dereference(n->next)) {
+	neigh_for_each_in_bucket_rcu(n, &nht->hash_heads[hash_val])
 		if (n->dev == dev && key_eq(n, pkey))
 			return n;
-	}
 
 	return NULL;
 }
@@ -349,7 +347,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb,
 int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, u32 flags,
 		 u32 nlmsg_pid);
 void __neigh_set_probe_once(struct neighbour *neigh);
-bool neigh_remove_one(struct neighbour *ndel, struct neigh_table *tbl);
+bool neigh_remove_one(struct neighbour *ndel);
 void neigh_changeaddr(struct neigh_table *tbl, struct net_device *dev);
 int neigh_ifdown(struct neigh_table *tbl, struct net_device *dev);
 int neigh_carrier_down(struct neigh_table *tbl, struct net_device *dev);

include/net/neighbour_tables.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _NET_NEIGHBOUR_TABLES_H
+#define _NET_NEIGHBOUR_TABLES_H
+
+enum {
+	NEIGH_ARP_TABLE = 0,
+	NEIGH_ND_TABLE = 1,
+	NEIGH_NR_TABLES,
+	NEIGH_LINK_TABLE = NEIGH_NR_TABLES /* Pseudo table for neigh_xmit */
+};
+
+#endif

net/core/neighbour.c

@@ -60,6 +60,25 @@ static int pneigh_ifdown_and_unlock(struct neigh_table *tbl,
 static const struct seq_operations neigh_stat_seq_ops;
 #endif
 
+static struct hlist_head *neigh_get_dev_table(struct net_device *dev, int family)
+{
+	int i;
+
+	switch (family) {
+	default:
+		DEBUG_NET_WARN_ON_ONCE(1);
+		fallthrough; /* to avoid panic by null-ptr-deref */
+	case AF_INET:
+		i = NEIGH_ARP_TABLE;
+		break;
+	case AF_INET6:
+		i = NEIGH_ND_TABLE;
+		break;
+	}
+
+	return &dev->neighbours[i];
+}
+
 /*
    Neighbour hash table buckets are protected with rwlock tbl->lock.
 
@@ -204,18 +223,14 @@ 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);
+		hlist_del_rcu(&n->dev_list);
 		neigh_mark_dead(n);
 		retval = true;
 	}
@@ -225,29 +240,6 @@ 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) -
@@ -275,7 +267,7 @@ 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;
@@ -379,54 +371,42 @@ static void pneigh_queue_purge(struct sk_buff_head *list, struct net *net,
 static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev,
 			    bool skip_perm)
 {
-	int i;
-	struct neigh_hash_table *nht;
+	struct hlist_head *dev_head;
+	struct hlist_node *tmp;
+	struct neighbour *n;
 
-	nht = rcu_dereference_protected(tbl->nht,
-					lockdep_is_held(&tbl->lock));
+	dev_head = neigh_get_dev_table(dev, tbl->family);
 
-	for (i = 0; i < (1 << nht->hash_shift); i++) {
-		struct neighbour *n;
-		struct neighbour __rcu **np = &nht->hash_buckets[i];
+	hlist_for_each_entry_safe(n, tmp, dev_head, dev_list) {
+		if (skip_perm && n->nud_state & NUD_PERMANENT)
+			continue;
 
-		while ((n = rcu_dereference_protected(*np,
-					lockdep_is_held(&tbl->lock))) != NULL) {
-			if (dev && n->dev != dev) {
-				np = &n->next;
-				continue;
-			}
-			if (skip_perm && n->nud_state & NUD_PERMANENT) {
-				np = &n->next;
-				continue;
-			}
-			rcu_assign_pointer(*np,
-				   rcu_dereference_protected(n->next,
-						lockdep_is_held(&tbl->lock)));
-			write_lock(&n->lock);
-			neigh_del_timer(n);
-			neigh_mark_dead(n);
-			if (refcount_read(&n->refcnt) != 1) {
-				/* The most unpleasant situation.
-				   We must destroy neighbour entry,
-				   but someone still uses it.
-
-				   The destroy will be delayed until
-				   the last user releases us, but
-				   we must kill timers etc. and move
-				   it to safe state.
-				 */
-				__skb_queue_purge(&n->arp_queue);
-				n->arp_queue_len_bytes = 0;
-				WRITE_ONCE(n->output, neigh_blackhole);
-				if (n->nud_state & NUD_VALID)
-					n->nud_state = NUD_NOARP;
-				else
-					n->nud_state = NUD_NONE;
-				neigh_dbg(2, "neigh %p is stray\n", n);
-			}
-			write_unlock(&n->lock);
-			neigh_cleanup_and_release(n);
+		hlist_del_rcu(&n->hash);
+		hlist_del_rcu(&n->dev_list);
+		write_lock(&n->lock);
+		neigh_del_timer(n);
+		neigh_mark_dead(n);
+		if (refcount_read(&n->refcnt) != 1) {
+			/* The most unpleasant situation.
+			 * We must destroy neighbour entry,
+			 * but someone still uses it.
+			 *
+			 * The destroy will be delayed until
+			 * the last user releases us, but
+			 * we must kill timers etc. and move
+			 * it to safe state.
+			 */
+			__skb_queue_purge(&n->arp_queue);
+			n->arp_queue_len_bytes = 0;
+			WRITE_ONCE(n->output, neigh_blackhole);
+			if (n->nud_state & NUD_VALID)
+				n->nud_state = NUD_NOARP;
+			else
+				n->nud_state = NUD_NONE;
+			neigh_dbg(2, "neigh %p is stray\n", n);
 		}
+		write_unlock(&n->lock);
+		neigh_cleanup_and_release(n);
 	}
 }
 
@@ -529,20 +509,21 @@ 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 size = (1 << shift) * sizeof(struct hlist_head);
+	struct hlist_head *hash_heads;
 	struct neigh_hash_table *ret;
-	struct neighbour __rcu **buckets;
 	int i;
 
 	ret = kmalloc(sizeof(*ret), GFP_ATOMIC);
 	if (!ret)
 		return NULL;
-	buckets = kvzalloc(size, GFP_ATOMIC);
-	if (!buckets) {
+
+	hash_heads = kvzalloc(size, GFP_ATOMIC);
+	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++)
 		neigh_get_hash_rnd(&ret->hash_rnd[i]);
@@ -555,7 +536,7 @@ 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);
 }
 
@@ -574,24 +555,17 @@ 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 hlist_node *tmp;
+		struct neighbour *n;
 
-		for (n = rcu_dereference_protected(old_nht->hash_buckets[i],
-						   lockdep_is_held(&tbl->lock));
-		     n != NULL;
-		     n = next) {
+		neigh_for_each_in_bucket_safe(n, tmp, &old_nht->hash_heads[i]) {
 			hash = tbl->hash(n->primary_key, n->dev,
 					 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]);
 		}
 	}
 
@@ -678,11 +652,7 @@ ___neigh_create(struct neigh_table *tbl, const void *pkey,
 		goto out_tbl_unlock;
 	}
 
-	for (n1 = rcu_dereference_protected(nht->hash_buckets[hash_val],
-					    lockdep_is_held(&tbl->lock));
-	     n1 != NULL;
-	     n1 = rcu_dereference_protected(n1->next,
-			lockdep_is_held(&tbl->lock))) {
+	neigh_for_each_in_bucket(n1, &nht->hash_heads[hash_val]) {
 		if (dev == n1->dev && !memcmp(n1->primary_key, n->primary_key, key_len)) {
 			if (want_ref)
 				neigh_hold(n1);
@@ -698,10 +668,11 @@ ___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]);
+
+	hlist_add_head_rcu(&n->dev_list,
+			   neigh_get_dev_table(dev, tbl->family));
+
 	write_unlock_bh(&tbl->lock);
 	neigh_dbg(2, "neigh %p is created\n", n);
 	rc = n;
@@ -933,10 +904,10 @@ static void neigh_connect(struct neighbour *neigh)
 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 neighbour __rcu **np;
-	unsigned int i;
 	struct neigh_hash_table *nht;
+	struct hlist_node *tmp;
+	struct neighbour *n;
+	unsigned int i;
 
 	NEIGH_CACHE_STAT_INC(tbl, periodic_gc_runs);
 
@@ -961,10 +932,7 @@ 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];
-
-		while ((n = rcu_dereference_protected(*np,
-				lockdep_is_held(&tbl->lock))) != NULL) {
+		neigh_for_each_in_bucket_safe(n, tmp, &nht->hash_heads[i]) {
 			unsigned int state;
 
 			write_lock(&n->lock);
@@ -973,7 +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) &&
@@ -984,18 +952,14 @@ 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);
+				hlist_del_rcu(&n->dev_list);
 				neigh_mark_dead(n);
 				write_unlock(&n->lock);
 				neigh_cleanup_and_release(n);
 				continue;
 			}
 			write_unlock(&n->lock);
-
-next_elt:
-			np = &n->next;
 		}
 		/*
 		 * It's fine to release lock here, even if hash table
@@ -1942,7 +1906,7 @@ 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:
@@ -2713,9 +2677,8 @@ static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
 	for (h = s_h; h < (1 << nht->hash_shift); h++) {
 		if (h > s_h)
 			s_idx = 0;
-		for (n = rcu_dereference(nht->hash_buckets[h]), idx = 0;
-		     n != NULL;
-		     n = rcu_dereference(n->next)) {
+		idx = 0;
+		neigh_for_each_in_bucket_rcu(n, &nht->hash_heads[h]) {
 			if (idx < s_idx || !net_eq(dev_net(n->dev), net))
 				goto next;
 			if (neigh_ifindex_filtered(n->dev, filter->dev_idx) ||
@@ -3082,9 +3045,7 @@ void neigh_for_each(struct neigh_table *tbl, void (*cb)(struct neighbour *, void
 	for (chain = 0; chain < (1 << nht->hash_shift); chain++) {
 		struct neighbour *n;
 
-		for (n = rcu_dereference(nht->hash_buckets[chain]);
-		     n != NULL;
-		     n = rcu_dereference(n->next))
+		neigh_for_each_in_bucket(n, &nht->hash_heads[chain])
 			cb(n, cookie);
 	}
 	read_unlock_bh(&tbl->lock);
@@ -3096,29 +3057,25 @@ EXPORT_SYMBOL(neigh_for_each);
 void __neigh_for_each_release(struct neigh_table *tbl,
 			      int (*cb)(struct neighbour *))
 {
-	int chain;
 	struct neigh_hash_table *nht;
+	int chain;
 
 	nht = rcu_dereference_protected(tbl->nht,
 					lockdep_is_held(&tbl->lock));
 	for (chain = 0; chain < (1 << nht->hash_shift); chain++) {
+		struct hlist_node *tmp;
 		struct neighbour *n;
-		struct neighbour __rcu **np;
 
-		np = &nht->hash_buckets[chain];
-		while ((n = rcu_dereference_protected(*np,
-					lockdep_is_held(&tbl->lock))) != NULL) {
+		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);
+				hlist_del_rcu(&n->dev_list);
 				neigh_mark_dead(n);
-			} else
-				np = &n->next;
+			}
 			write_unlock(&n->lock);
 			if (release)
 				neigh_cleanup_and_release(n);
@@ -3175,43 +3132,53 @@ EXPORT_SYMBOL(neigh_xmit);
 
 #ifdef CONFIG_PROC_FS
 
-static struct neighbour *neigh_get_first(struct seq_file *seq)
+static struct neighbour *neigh_get_valid(struct seq_file *seq,
+					 struct neighbour *n,
+					 loff_t *pos)
 {
 	struct neigh_seq_state *state = seq->private;
 	struct net *net = seq_file_net(seq);
+
+	if (!net_eq(dev_net(n->dev), net))
+		return NULL;
+
+	if (state->neigh_sub_iter) {
+		loff_t fakep = 0;
+		void *v;
+
+		v = state->neigh_sub_iter(state, n, pos ? pos : &fakep);
+		if (!v)
+			return NULL;
+		if (pos)
+			return v;
+	}
+
+	if (!(state->flags & NEIGH_SEQ_SKIP_NOARP))
+		return n;
+
+	if (READ_ONCE(n->nud_state) & ~NUD_NOARP)
+		return n;
+
+	return NULL;
+}
+
+static struct neighbour *neigh_get_first(struct seq_file *seq)
+{
+	struct neigh_seq_state *state = seq->private;
 	struct neigh_hash_table *nht = state->nht;
-	struct neighbour *n = NULL;
-	int bucket;
+	struct neighbour *n, *tmp;
 
 	state->flags &= ~NEIGH_SEQ_IS_PNEIGH;
-	for (bucket = 0; bucket < (1 << nht->hash_shift); bucket++) {
-		n = rcu_dereference(nht->hash_buckets[bucket]);
 
-		while (n) {
-			if (!net_eq(dev_net(n->dev), net))
-				goto next;
-			if (state->neigh_sub_iter) {
-				loff_t fakep = 0;
-				void *v;
-
-				v = state->neigh_sub_iter(state, n, &fakep);
-				if (!v)
-					goto next;
-			}
-			if (!(state->flags & NEIGH_SEQ_SKIP_NOARP))
-				break;
-			if (READ_ONCE(n->nud_state) & ~NUD_NOARP)
-				break;
-next:
-			n = rcu_dereference(n->next);
+	while (++state->bucket < (1 << nht->hash_shift)) {
+		neigh_for_each_in_bucket(n, &nht->hash_heads[state->bucket]) {
+			tmp = neigh_get_valid(seq, n, NULL);
+			if (tmp)
+				return tmp;
 		}
-
-		if (n)
-			break;
 	}
-	state->bucket = bucket;
 
-	return n;
+	return NULL;
 }
 
 static struct neighbour *neigh_get_next(struct seq_file *seq,
@@ -3219,46 +3186,28 @@ static struct neighbour *neigh_get_next(struct seq_file *seq,
 					loff_t *pos)
 {
 	struct neigh_seq_state *state = seq->private;
-	struct net *net = seq_file_net(seq);
-	struct neigh_hash_table *nht = state->nht;
+	struct neighbour *tmp;
 
 	if (state->neigh_sub_iter) {
 		void *v = state->neigh_sub_iter(state, n, pos);
+
 		if (v)
 			return n;
 	}
-	n = rcu_dereference(n->next);
 
-	while (1) {
-		while (n) {
-			if (!net_eq(dev_net(n->dev), net))
-				goto next;
-			if (state->neigh_sub_iter) {
-				void *v = state->neigh_sub_iter(state, n, pos);
-				if (v)
-					return n;
-				goto next;
-			}
-			if (!(state->flags & NEIGH_SEQ_SKIP_NOARP))
-				break;
-
-			if (READ_ONCE(n->nud_state) & ~NUD_NOARP)
-				break;
-next:
-			n = rcu_dereference(n->next);
+	hlist_for_each_entry_continue(n, hash) {
+		tmp = neigh_get_valid(seq, n, pos);
+		if (tmp) {
+			n = tmp;
+			goto out;
 		}
-
-		if (n)
-			break;
-
-		if (++state->bucket >= (1 << nht->hash_shift))
-			break;
-
-		n = rcu_dereference(nht->hash_buckets[state->bucket]);
 	}
 
+	n = neigh_get_first(seq);
+out:
 	if (n && pos)
 		--(*pos);
+
 	return n;
 }
 
@@ -3361,7 +3310,7 @@ void *neigh_seq_start(struct seq_file *seq, loff_t *pos, struct neigh_table *tbl
 	struct neigh_seq_state *state = seq->private;
 
 	state->tbl = tbl;
-	state->bucket = 0;
+	state->bucket = -1;
 	state->flags = (neigh_seq_flags & ~NEIGH_SEQ_IS_PNEIGH);
 
 	rcu_read_lock();

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);
 	}