Merge branch 'neighbor-More-gc_list-changes'

David Ahern says:

====================
neighbor: More gc_list changes

More gc_list changes and cleanups.

The first 2 patches are bug fixes from the first gc_list change.
Specifically, fix the locking order to be consistent - table lock
followed by neighbor lock, and then entries in the FAILED state
should always be candidates for forced_gc without waiting for any
time span (return to the eviction logic prior to the separate gc_list).

Patch 3 removes 2 now unnecessary arguments to neigh_del.

Patch 4 moves a helper from a header file to core code in preparation
for Patch 5 which removes NTF_EXT_LEARNED entries from the gc_list.
These entries are already exempt from forced_gc; patch 5 removes them
from consideration and makes them on par with PERMANENT entries given
that they are also managed by userspace.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/neighbour.h

@@ -549,24 +549,6 @@ static inline void neigh_ha_snapshot(char *dst, const struct neighbour *n,
 	} while (read_seqretry(&n->ha_lock, seq));
 }
 
-static inline void neigh_update_ext_learned(struct neighbour *neigh, u32 flags,
-					    int *notify)
-{
-	u8 ndm_flags = 0;
-
-	if (!(flags & NEIGH_UPDATE_F_ADMIN))
-		return;
-
-	ndm_flags |= (flags & NEIGH_UPDATE_F_EXT_LEARNED) ? NTF_EXT_LEARNED : 0;
-	if ((neigh->flags ^ ndm_flags) & NTF_EXT_LEARNED) {
-		if (ndm_flags & NTF_EXT_LEARNED)
-			neigh->flags |= NTF_EXT_LEARNED;
-		else
-			neigh->flags &= ~NTF_EXT_LEARNED;
-		*notify = 1;
-	}
-}
-
 static inline void neigh_update_is_router(struct neighbour *neigh, u32 flags,
 					  int *notify)
 {

net/core/neighbour.c

@@ -127,40 +127,62 @@ static void neigh_mark_dead(struct neighbour *n)
 	}
 }
 
-static void neigh_change_state(struct neighbour *n, u8 new)
+static void neigh_update_gc_list(struct neighbour *n)
 {
-	bool on_gc_list = !list_empty(&n->gc_list);
-	bool new_is_perm = new & NUD_PERMANENT;
+	bool on_gc_list, exempt_from_gc;
 
-	n->nud_state = new;
+	write_lock_bh(&n->tbl->lock);
+	write_lock(&n->lock);
 
-	/* remove from the gc list if new state is permanent;
-	 * add to the gc list if new state is not permanent
+	/* remove from the gc list if new state is permanent or if neighbor
+	 * is externally learned; otherwise entry should be on the gc list
 	 */
-	if (new_is_perm && on_gc_list) {
-		write_lock_bh(&n->tbl->lock);
-		list_del_init(&n->gc_list);
-		write_unlock_bh(&n->tbl->lock);
+	exempt_from_gc = n->nud_state & NUD_PERMANENT ||
+			 n->flags & NTF_EXT_LEARNED;
+	on_gc_list = !list_empty(&n->gc_list);
 
+	if (exempt_from_gc && on_gc_list) {
+		list_del_init(&n->gc_list);
 		atomic_dec(&n->tbl->gc_entries);
-	} else if (!new_is_perm && !on_gc_list) {
+	} else if (!exempt_from_gc && !on_gc_list) {
 		/* add entries to the tail; cleaning removes from the front */
-		write_lock_bh(&n->tbl->lock);
 		list_add_tail(&n->gc_list, &n->tbl->gc_list);
+		atomic_inc(&n->tbl->gc_entries);
+	}
+
+	write_unlock(&n->lock);
 	write_unlock_bh(&n->tbl->lock);
+}
 
-		atomic_inc(&n->tbl->gc_entries);
+static bool neigh_update_ext_learned(struct neighbour *neigh, u32 flags,
+				     int *notify)
+{
+	bool rc = false;
+	u8 ndm_flags;
+
+	if (!(flags & NEIGH_UPDATE_F_ADMIN))
+		return rc;
+
+	ndm_flags = (flags & NEIGH_UPDATE_F_EXT_LEARNED) ? NTF_EXT_LEARNED : 0;
+	if ((neigh->flags ^ ndm_flags) & NTF_EXT_LEARNED) {
+		if (ndm_flags & NTF_EXT_LEARNED)
+			neigh->flags |= NTF_EXT_LEARNED;
+		else
+			neigh->flags &= ~NTF_EXT_LEARNED;
+		rc = true;
+		*notify = 1;
 	}
+
+	return rc;
 }
 
-static bool neigh_del(struct neighbour *n, __u8 state, __u8 flags,
-		      struct neighbour __rcu **np, struct neigh_table *tbl)
+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 && !(n->nud_state & state) &&
-	    !(n->flags & flags)) {
+	if (refcount_read(&n->refcnt) == 1) {
 		struct neighbour *neigh;
 
 		neigh = rcu_dereference_protected(n->next,
@@ -192,7 +214,7 @@ bool neigh_remove_one(struct neighbour *ndel, struct neigh_table *tbl)
 	while ((n = rcu_dereference_protected(*np,
 					      lockdep_is_held(&tbl->lock)))) {
 		if (n == ndel)
-			return neigh_del(n, 0, 0, np, tbl);
+			return neigh_del(n, np, tbl);
 		np = &n->next;
 	}
 	return false;
@@ -202,9 +224,7 @@ static int neigh_forced_gc(struct neigh_table *tbl)
 {
 	int max_clean = atomic_read(&tbl->gc_entries) - tbl->gc_thresh2;
 	unsigned long tref = jiffies - 5 * HZ;
-	u8 flags = NTF_EXT_LEARNED;
 	struct neighbour *n, *tmp;
-	u8 state = NUD_PERMANENT;
 	int shrunk = 0;
 
 	NEIGH_CACHE_STAT_INC(tbl, forced_gc_runs);
@@ -216,7 +236,7 @@ static int neigh_forced_gc(struct neigh_table *tbl)
 			bool remove = false;
 
 			write_lock(&n->lock);
-			if (!(n->nud_state & state) && !(n->flags & flags) &&
+			if ((n->nud_state == NUD_FAILED) ||
 			    time_after(tref, n->updated))
 				remove = true;
 			write_unlock(&n->lock);
@@ -355,13 +375,13 @@ EXPORT_SYMBOL(neigh_ifdown);
 
 static struct neighbour *neigh_alloc(struct neigh_table *tbl,
 				     struct net_device *dev,
-				     bool permanent)
+				     bool exempt_from_gc)
 {
 	struct neighbour *n = NULL;
 	unsigned long now = jiffies;
 	int entries;
 
-	if (permanent)
+	if (exempt_from_gc)
 		goto do_alloc;
 
 	entries = atomic_inc_return(&tbl->gc_entries) - 1;
@@ -403,7 +423,7 @@ static struct neighbour *neigh_alloc(struct neigh_table *tbl,
 	return n;
 
 out_entries:
-	if (!permanent)
+	if (!exempt_from_gc)
 		atomic_dec(&tbl->gc_entries);
 	goto out;
 }
@@ -550,9 +570,9 @@ EXPORT_SYMBOL(neigh_lookup_nodev);
 static struct neighbour *___neigh_create(struct neigh_table *tbl,
 					 const void *pkey,
 					 struct net_device *dev,
-					 bool permanent, bool want_ref)
+					 bool exempt_from_gc, bool want_ref)
 {
-	struct neighbour *n1, *rc, *n = neigh_alloc(tbl, dev, permanent);
+	struct neighbour *n1, *rc, *n = neigh_alloc(tbl, dev, exempt_from_gc);
 	u32 hash_val;
 	unsigned int key_len = tbl->key_len;
 	int error;
@@ -618,7 +638,7 @@ static struct neighbour *___neigh_create(struct neigh_table *tbl,
 	}
 
 	n->dead = 0;
-	if (!permanent)
+	if (!exempt_from_gc)
 		list_add_tail(&n->gc_list, &n->tbl->gc_list);
 
 	if (want_ref)
@@ -1194,6 +1214,7 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
 			  u8 new, u32 flags, u32 nlmsg_pid,
 			  struct netlink_ext_ack *extack)
 {
+	bool ext_learn_change = false;
 	u8 old;
 	int err;
 	int notify = 0;
@@ -1214,13 +1235,13 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
 		goto out;
 	}
 
-	neigh_update_ext_learned(neigh, flags, &notify);
+	ext_learn_change = neigh_update_ext_learned(neigh, flags, &notify);
 
 	if (!(new & NUD_VALID)) {
 		neigh_del_timer(neigh);
 		if (old & NUD_CONNECTED)
 			neigh_suspect(neigh);
-		neigh_change_state(neigh, new);
+		neigh->nud_state = new;
 		err = 0;
 		notify = old & NUD_VALID;
 		if ((old & (NUD_INCOMPLETE | NUD_PROBE)) &&
@@ -1299,7 +1320,7 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
 						((new & NUD_REACHABLE) ?
 						 neigh->parms->reachable_time :
 						 0)));
-		neigh_change_state(neigh, new);
+		neigh->nud_state = new;
 		notify = 1;
 	}
 
@@ -1360,6 +1381,9 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
 		neigh_update_is_router(neigh, flags, &notify);
 	write_unlock_bh(&neigh->lock);
 
+	if (((new ^ old) & NUD_PERMANENT) || ext_learn_change)
+		neigh_update_gc_list(neigh);
+
 	if (notify)
 		neigh_update_notify(neigh, nlmsg_pid);
 
@@ -1862,14 +1886,16 @@ static int neigh_add(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	neigh = neigh_lookup(tbl, dst, dev);
 	if (neigh == NULL) {
+		bool exempt_from_gc;
+
 		if (!(nlh->nlmsg_flags & NLM_F_CREATE)) {
 			err = -ENOENT;
 			goto out;
 		}
 
-		neigh = ___neigh_create(tbl, dst, dev,
-					ndm->ndm_state & NUD_PERMANENT,
-					true);
+		exempt_from_gc = ndm->ndm_state & NUD_PERMANENT ||
+				 ndm->ndm_flags & NTF_EXT_LEARNED;
+		neigh = ___neigh_create(tbl, dst, dev, exempt_from_gc, true);
 		if (IS_ERR(neigh)) {
 			err = PTR_ERR(neigh);
 			goto out;