Commit 767e97e1 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

neigh: RCU conversion of struct neighbour 



This is the second step for neighbour RCU conversion.

(first was commit d6bf7817 : RCU conversion of neigh hash table)

neigh_lookup() becomes lockless, but still take a reference on found
neighbour. (no more read_lock()/read_unlock() on tbl->lock)

struct neighbour gets an additional rcu_head field and is freed after an
RCU grace period.

Future work would need to eventually not take a reference on neighbour
for temporary dst (DST_NOCACHE), but this would need dst->_neighbour to
use a noref bit like we did for skb->_dst.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 546add79

include/net/neighbour.h

+3 −2
Original line number Diff line number Diff line
@@ -91,7 +91,7 @@ struct neigh_statistics { 
#define NEIGH_CACHE_STAT_INC(tbl, field) this_cpu_inc((tbl)->stats->field)



struct neighbour {

	struct neighbour	*next;

	struct neighbour __rcu	*next;

	struct neigh_table	*tbl;

	struct neigh_parms	*parms;

	struct net_device	*dev;
@@ -111,6 +111,7 @@ struct neighbour { 
	struct sk_buff_head	arp_queue;

	struct timer_list	timer;

	const struct neigh_ops	*ops;

	struct rcu_head		rcu;

	u8			primary_key[0];

};
@@ -139,7 +140,7 @@ struct pneigh_entry { 
 */



struct neigh_hash_table {

	struct neighbour	**hash_buckets;

	struct neighbour __rcu	**hash_buckets;

	unsigned int		hash_mask;

	__u32			hash_rnd;

	struct rcu_head		rcu;

net/core/neighbour.c

+85 −52
Original line number Diff line number Diff line
@@ -139,10 +139,12 @@ static int neigh_forced_gc(struct neigh_table *tbl) 
	nht = rcu_dereference_protected(tbl->nht,

					lockdep_is_held(&tbl->lock));

	for (i = 0; i <= nht->hash_mask; i++) {

		struct neighbour *n, **np;

		struct neighbour *n;

		struct neighbour __rcu **np;



		np = &nht->hash_buckets[i];

		while ((n = *np) != NULL) {

		while ((n = rcu_dereference_protected(*np,

					lockdep_is_held(&tbl->lock))) != NULL) {

			/* Neighbour record may be discarded if:

			 * - nobody refers to it.

			 * - it is not permanent
@@ -150,7 +152,9 @@ static int neigh_forced_gc(struct neigh_table *tbl) 
			write_lock(&n->lock);

			if (atomic_read(&n->refcnt) == 1 &&

			    !(n->nud_state & NUD_PERMANENT)) {

				*np	= n->next;

				rcu_assign_pointer(*np,

					rcu_dereference_protected(n->next,

						  lockdep_is_held(&tbl->lock)));

				n->dead = 1;

				shrunk	= 1;

				write_unlock(&n->lock);
@@ -208,14 +212,18 @@ static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev) 
					lockdep_is_held(&tbl->lock));



	for (i = 0; i <= nht->hash_mask; i++) {

		struct neighbour *n, **np = &nht->hash_buckets[i];

		struct neighbour *n;

		struct neighbour __rcu **np = &nht->hash_buckets[i];



		while ((n = *np) != NULL) {

		while ((n = rcu_dereference_protected(*np,

					lockdep_is_held(&tbl->lock))) != NULL) {

			if (dev && n->dev != dev) {

				np = &n->next;

				continue;

			}

			*np = n->next;

			rcu_assign_pointer(*np,

				   rcu_dereference_protected(n->next,

						lockdep_is_held(&tbl->lock)));

			write_lock(&n->lock);

			neigh_del_timer(n);

			n->dead = 1;
@@ -323,7 +331,7 @@ static struct neigh_hash_table *neigh_hash_alloc(unsigned int entries) 
		kfree(ret);

		return NULL;

	}

	ret->hash_buckets = buckets;

	rcu_assign_pointer(ret->hash_buckets, buckets);

	ret->hash_mask = entries - 1;

	get_random_bytes(&ret->hash_rnd, sizeof(ret->hash_rnd));

	return ret;
@@ -362,17 +370,22 @@ static struct neigh_hash_table *neigh_hash_grow(struct neigh_table *tbl, 
	for (i = 0; i <= old_nht->hash_mask; i++) {

		struct neighbour *n, *next;



		for (n = old_nht->hash_buckets[i];

		for (n = rcu_dereference_protected(old_nht->hash_buckets[i],

						   lockdep_is_held(&tbl->lock));

		     n != NULL;

		     n = next) {

			hash = tbl->hash(n->primary_key, n->dev,

					 new_nht->hash_rnd);



			hash &= new_nht->hash_mask;

			next = n->next;

			next = rcu_dereference_protected(n->next,

						lockdep_is_held(&tbl->lock));



			n->next = new_nht->hash_buckets[hash];

			new_nht->hash_buckets[hash] = n;

			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);

		}

	}
@@ -394,15 +407,18 @@ struct neighbour *neigh_lookup(struct neigh_table *tbl, const void *pkey, 
	rcu_read_lock_bh();

	nht = rcu_dereference_bh(tbl->nht);

	hash_val = tbl->hash(pkey, dev, nht->hash_rnd) & nht->hash_mask;

	read_lock(&tbl->lock);

	for (n = nht->hash_buckets[hash_val]; n; n = n->next) {



	for (n = rcu_dereference_bh(nht->hash_buckets[hash_val]);

	     n != NULL;

	     n = rcu_dereference_bh(n->next)) {

		if (dev == n->dev && !memcmp(n->primary_key, pkey, key_len)) {

			neigh_hold(n);

			if (!atomic_inc_not_zero(&n->refcnt))

				n = NULL;

			NEIGH_CACHE_STAT_INC(tbl, hits);

			break;

		}

	}

	read_unlock(&tbl->lock);



	rcu_read_unlock_bh();

	return n;

}
@@ -421,16 +437,19 @@ struct neighbour *neigh_lookup_nodev(struct neigh_table *tbl, struct net *net, 
	rcu_read_lock_bh();

	nht = rcu_dereference_bh(tbl->nht);

	hash_val = tbl->hash(pkey, NULL, nht->hash_rnd) & nht->hash_mask;

	read_lock(&tbl->lock);

	for (n = nht->hash_buckets[hash_val]; n; n = n->next) {



	for (n = rcu_dereference_bh(nht->hash_buckets[hash_val]);

	     n != NULL;

	     n = rcu_dereference_bh(n->next)) {

		if (!memcmp(n->primary_key, pkey, key_len) &&

		    net_eq(dev_net(n->dev), net)) {

			neigh_hold(n);

			if (!atomic_inc_not_zero(&n->refcnt))

				n = NULL;

			NEIGH_CACHE_STAT_INC(tbl, hits);

			break;

		}

	}

	read_unlock(&tbl->lock);



	rcu_read_unlock_bh();

	return n;

}
@@ -483,7 +502,11 @@ struct neighbour *neigh_create(struct neigh_table *tbl, const void *pkey, 
		goto out_tbl_unlock;

	}



	for (n1 = nht->hash_buckets[hash_val]; n1; n1 = n1->next) {

	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))) {

		if (dev == n1->dev && !memcmp(n1->primary_key, pkey, key_len)) {

			neigh_hold(n1);

			rc = n1;
@@ -491,10 +514,12 @@ struct neighbour *neigh_create(struct neigh_table *tbl, const void *pkey, 
		}

	}



	n->next = nht->hash_buckets[hash_val];

	nht->hash_buckets[hash_val] = n;

	n->dead = 0;

	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);

	write_unlock_bh(&tbl->lock);

	NEIGH_PRINTK2("neigh %p is created.\n", n);

	rc = n;
@@ -651,6 +676,12 @@ static inline void neigh_parms_put(struct neigh_parms *parms) 
		neigh_parms_destroy(parms);

}



static void neigh_destroy_rcu(struct rcu_head *head)

{

	struct neighbour *neigh = container_of(head, struct neighbour, rcu);



	kmem_cache_free(neigh->tbl->kmem_cachep, neigh);

}

/*

 *	neighbour must already be out of the table;

 *
@@ -690,7 +721,7 @@ void neigh_destroy(struct neighbour *neigh) 
	NEIGH_PRINTK2("neigh %p is destroyed.\n", neigh);



	atomic_dec(&neigh->tbl->entries);

	kmem_cache_free(neigh->tbl->kmem_cachep, neigh);

	call_rcu(&neigh->rcu, neigh_destroy_rcu);

}

EXPORT_SYMBOL(neigh_destroy);
@@ -731,7 +762,8 @@ 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, **np;

	struct neighbour *n;

	struct neighbour __rcu **np;

	unsigned int i;

	struct neigh_hash_table *nht;
@@ -756,7 +788,8 @@ static void neigh_periodic_work(struct work_struct *work) 
	for (i = 0 ; i <= nht->hash_mask; i++) {

		np = &nht->hash_buckets[i];



		while ((n = *np) != NULL) {

		while ((n = rcu_dereference_protected(*np,

				lockdep_is_held(&tbl->lock))) != NULL) {

			unsigned int state;



			write_lock(&n->lock);
@@ -1213,8 +1246,8 @@ static void neigh_hh_init(struct neighbour *n, struct dst_entry *dst, 
}



/* This function can be used in contexts, where only old dev_queue_xmit

   worked, f.e. if you want to override normal output path (eql, shaper),

   but resolution is not made yet.

 * worked, f.e. if you want to override normal output path (eql, shaper),

 * but resolution is not made yet.

 */



int neigh_compat_output(struct sk_buff *skb)
@@ -2132,13 +2165,14 @@ static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb, 
	rcu_read_lock_bh();

	nht = rcu_dereference_bh(tbl->nht);



	read_lock(&tbl->lock);

	for (h = 0; h <= nht->hash_mask; h++) {

		if (h < s_h)

			continue;

		if (h > s_h)

			s_idx = 0;

		for (n = nht->hash_buckets[h], idx = 0; n; n = n->next) {

		for (n = rcu_dereference_bh(nht->hash_buckets[h]), idx = 0;

		     n != NULL;

		     n = rcu_dereference_bh(n->next)) {

			if (!net_eq(dev_net(n->dev), net))

				continue;

			if (idx < s_idx)
@@ -2156,7 +2190,6 @@ static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb, 
	}

	rc = skb->len;

out:

	read_unlock(&tbl->lock);

	rcu_read_unlock_bh();

	cb->args[1] = h;

	cb->args[2] = idx;
@@ -2195,11 +2228,13 @@ void neigh_for_each(struct neigh_table *tbl, void (*cb)(struct neighbour *, void 
	rcu_read_lock_bh();

	nht = rcu_dereference_bh(tbl->nht);



	read_lock(&tbl->lock);

	read_lock(&tbl->lock); /* avoid resizes */

	for (chain = 0; chain <= nht->hash_mask; chain++) {

		struct neighbour *n;



		for (n = nht->hash_buckets[chain]; n; n = n->next)

		for (n = rcu_dereference_bh(nht->hash_buckets[chain]);

		     n != NULL;

		     n = rcu_dereference_bh(n->next))

			cb(n, cookie);

	}

	read_unlock(&tbl->lock);
@@ -2217,16 +2252,20 @@ void __neigh_for_each_release(struct neigh_table *tbl, 
	nht = rcu_dereference_protected(tbl->nht,

					lockdep_is_held(&tbl->lock));

	for (chain = 0; chain <= nht->hash_mask; chain++) {

		struct neighbour *n, **np;

		struct neighbour *n;

		struct neighbour __rcu **np;



		np = &nht->hash_buckets[chain];

		while ((n = *np) != NULL) {

		while ((n = rcu_dereference_protected(*np,

					lockdep_is_held(&tbl->lock))) != NULL) {

			int release;



			write_lock(&n->lock);

			release = cb(n);

			if (release) {

				*np = n->next;

				rcu_assign_pointer(*np,

					rcu_dereference_protected(n->next,

						lockdep_is_held(&tbl->lock)));

				n->dead = 1;

			} else

				np = &n->next;
@@ -2250,7 +2289,7 @@ static struct neighbour *neigh_get_first(struct seq_file *seq) 


	state->flags &= ~NEIGH_SEQ_IS_PNEIGH;

	for (bucket = 0; bucket <= nht->hash_mask; bucket++) {

		n = nht->hash_buckets[bucket];

		n = rcu_dereference_bh(nht->hash_buckets[bucket]);



		while (n) {

			if (!net_eq(dev_net(n->dev), net))
@@ -2268,7 +2307,7 @@ static struct neighbour *neigh_get_first(struct seq_file *seq) 
			if (n->nud_state & ~NUD_NOARP)

				break;

next:

			n = n->next;

			n = rcu_dereference_bh(n->next);

		}



		if (n)
@@ -2292,7 +2331,7 @@ static struct neighbour *neigh_get_next(struct seq_file *seq, 
		if (v)

			return n;

	}

	n = n->next;

	n = rcu_dereference_bh(n->next);



	while (1) {

		while (n) {
@@ -2310,7 +2349,7 @@ static struct neighbour *neigh_get_next(struct seq_file *seq, 
			if (n->nud_state & ~NUD_NOARP)

				break;

next:

			n = n->next;

			n = rcu_dereference_bh(n->next);

		}



		if (n)
@@ -2319,7 +2358,7 @@ static struct neighbour *neigh_get_next(struct seq_file *seq, 
		if (++state->bucket > nht->hash_mask)

			break;



		n = nht->hash_buckets[state->bucket];

		n = rcu_dereference_bh(nht->hash_buckets[state->bucket]);

	}



	if (n && pos)
@@ -2417,7 +2456,6 @@ static void *neigh_get_idx_any(struct seq_file *seq, loff_t *pos) 
}



void *neigh_seq_start(struct seq_file *seq, loff_t *pos, struct neigh_table *tbl, unsigned int neigh_seq_flags)

	__acquires(tbl->lock)

	__acquires(rcu_bh)

{

	struct neigh_seq_state *state = seq->private;
@@ -2428,7 +2466,7 @@ void *neigh_seq_start(struct seq_file *seq, loff_t *pos, struct neigh_table *tbl 


	rcu_read_lock_bh();

	state->nht = rcu_dereference_bh(tbl->nht);

	read_lock(&tbl->lock);



	return *pos ? neigh_get_idx_any(seq, pos) : SEQ_START_TOKEN;

}

EXPORT_SYMBOL(neigh_seq_start);
@@ -2461,13 +2499,8 @@ out: 
EXPORT_SYMBOL(neigh_seq_next);



void neigh_seq_stop(struct seq_file *seq, void *v)

	__releases(tbl->lock)

	__releases(rcu_bh)

{

	struct neigh_seq_state *state = seq->private;

	struct neigh_table *tbl = state->tbl;



	read_unlock(&tbl->lock);

	rcu_read_unlock_bh();

}

EXPORT_SYMBOL(neigh_seq_stop);

CRA Git | Maintained and supported by SUSTech CRA and CCSE