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: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
David S. Miller
parent
546add7946
commit
767e97e1e0
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@ -91,7 +91,7 @@ struct neigh_statistics {
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#define NEIGH_CACHE_STAT_INC(tbl, field) this_cpu_inc((tbl)->stats->field)
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struct neighbour {
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struct neighbour *next;
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struct neighbour __rcu *next;
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struct neigh_table *tbl;
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struct neigh_parms *parms;
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struct net_device *dev;
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@ -111,6 +111,7 @@ struct neighbour {
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struct sk_buff_head arp_queue;
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struct timer_list timer;
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const struct neigh_ops *ops;
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struct rcu_head rcu;
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u8 primary_key[0];
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};
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@ -139,7 +140,7 @@ struct pneigh_entry {
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*/
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struct neigh_hash_table {
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struct neighbour **hash_buckets;
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struct neighbour __rcu **hash_buckets;
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unsigned int hash_mask;
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__u32 hash_rnd;
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struct rcu_head rcu;
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@ -139,10 +139,12 @@ static int neigh_forced_gc(struct neigh_table *tbl)
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nht = rcu_dereference_protected(tbl->nht,
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lockdep_is_held(&tbl->lock));
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for (i = 0; i <= nht->hash_mask; i++) {
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struct neighbour *n, **np;
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struct neighbour *n;
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struct neighbour __rcu **np;
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np = &nht->hash_buckets[i];
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while ((n = *np) != NULL) {
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while ((n = rcu_dereference_protected(*np,
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lockdep_is_held(&tbl->lock))) != NULL) {
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/* Neighbour record may be discarded if:
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* - nobody refers to it.
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* - it is not permanent
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@ -150,7 +152,9 @@ static int neigh_forced_gc(struct neigh_table *tbl)
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write_lock(&n->lock);
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if (atomic_read(&n->refcnt) == 1 &&
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!(n->nud_state & NUD_PERMANENT)) {
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*np = n->next;
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rcu_assign_pointer(*np,
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rcu_dereference_protected(n->next,
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lockdep_is_held(&tbl->lock)));
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n->dead = 1;
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shrunk = 1;
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write_unlock(&n->lock);
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@ -208,14 +212,18 @@ static void neigh_flush_dev(struct neigh_table *tbl, struct net_device *dev)
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lockdep_is_held(&tbl->lock));
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for (i = 0; i <= nht->hash_mask; i++) {
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struct neighbour *n, **np = &nht->hash_buckets[i];
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struct neighbour *n;
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struct neighbour __rcu **np = &nht->hash_buckets[i];
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while ((n = *np) != NULL) {
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while ((n = rcu_dereference_protected(*np,
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lockdep_is_held(&tbl->lock))) != NULL) {
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if (dev && n->dev != dev) {
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np = &n->next;
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continue;
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}
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*np = n->next;
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rcu_assign_pointer(*np,
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rcu_dereference_protected(n->next,
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lockdep_is_held(&tbl->lock)));
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write_lock(&n->lock);
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neigh_del_timer(n);
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n->dead = 1;
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@ -323,7 +331,7 @@ static struct neigh_hash_table *neigh_hash_alloc(unsigned int entries)
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kfree(ret);
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return NULL;
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}
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ret->hash_buckets = buckets;
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rcu_assign_pointer(ret->hash_buckets, buckets);
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ret->hash_mask = entries - 1;
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get_random_bytes(&ret->hash_rnd, sizeof(ret->hash_rnd));
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return ret;
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@ -362,17 +370,22 @@ static struct neigh_hash_table *neigh_hash_grow(struct neigh_table *tbl,
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for (i = 0; i <= old_nht->hash_mask; i++) {
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struct neighbour *n, *next;
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for (n = old_nht->hash_buckets[i];
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for (n = rcu_dereference_protected(old_nht->hash_buckets[i],
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lockdep_is_held(&tbl->lock));
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n != NULL;
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n = next) {
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hash = tbl->hash(n->primary_key, n->dev,
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new_nht->hash_rnd);
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hash &= new_nht->hash_mask;
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next = n->next;
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next = rcu_dereference_protected(n->next,
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lockdep_is_held(&tbl->lock));
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n->next = new_nht->hash_buckets[hash];
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new_nht->hash_buckets[hash] = n;
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rcu_assign_pointer(n->next,
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rcu_dereference_protected(
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new_nht->hash_buckets[hash],
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lockdep_is_held(&tbl->lock)));
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rcu_assign_pointer(new_nht->hash_buckets[hash], n);
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}
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}
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@ -394,15 +407,18 @@ struct neighbour *neigh_lookup(struct neigh_table *tbl, const void *pkey,
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rcu_read_lock_bh();
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nht = rcu_dereference_bh(tbl->nht);
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hash_val = tbl->hash(pkey, dev, nht->hash_rnd) & nht->hash_mask;
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read_lock(&tbl->lock);
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for (n = nht->hash_buckets[hash_val]; n; n = n->next) {
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for (n = rcu_dereference_bh(nht->hash_buckets[hash_val]);
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n != NULL;
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n = rcu_dereference_bh(n->next)) {
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if (dev == n->dev && !memcmp(n->primary_key, pkey, key_len)) {
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neigh_hold(n);
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if (!atomic_inc_not_zero(&n->refcnt))
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n = NULL;
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NEIGH_CACHE_STAT_INC(tbl, hits);
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break;
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}
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}
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read_unlock(&tbl->lock);
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rcu_read_unlock_bh();
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return n;
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}
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@ -421,16 +437,19 @@ struct neighbour *neigh_lookup_nodev(struct neigh_table *tbl, struct net *net,
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rcu_read_lock_bh();
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nht = rcu_dereference_bh(tbl->nht);
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hash_val = tbl->hash(pkey, NULL, nht->hash_rnd) & nht->hash_mask;
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read_lock(&tbl->lock);
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for (n = nht->hash_buckets[hash_val]; n; n = n->next) {
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for (n = rcu_dereference_bh(nht->hash_buckets[hash_val]);
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n != NULL;
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n = rcu_dereference_bh(n->next)) {
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if (!memcmp(n->primary_key, pkey, key_len) &&
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net_eq(dev_net(n->dev), net)) {
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neigh_hold(n);
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if (!atomic_inc_not_zero(&n->refcnt))
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n = NULL;
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NEIGH_CACHE_STAT_INC(tbl, hits);
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break;
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}
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}
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read_unlock(&tbl->lock);
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rcu_read_unlock_bh();
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return n;
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}
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@ -483,7 +502,11 @@ struct neighbour *neigh_create(struct neigh_table *tbl, const void *pkey,
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goto out_tbl_unlock;
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}
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for (n1 = nht->hash_buckets[hash_val]; n1; n1 = n1->next) {
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for (n1 = rcu_dereference_protected(nht->hash_buckets[hash_val],
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lockdep_is_held(&tbl->lock));
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n1 != NULL;
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n1 = rcu_dereference_protected(n1->next,
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lockdep_is_held(&tbl->lock))) {
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if (dev == n1->dev && !memcmp(n1->primary_key, pkey, key_len)) {
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neigh_hold(n1);
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rc = n1;
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@ -491,10 +514,12 @@ struct neighbour *neigh_create(struct neigh_table *tbl, const void *pkey,
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}
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}
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n->next = nht->hash_buckets[hash_val];
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nht->hash_buckets[hash_val] = n;
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n->dead = 0;
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neigh_hold(n);
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rcu_assign_pointer(n->next,
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rcu_dereference_protected(nht->hash_buckets[hash_val],
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lockdep_is_held(&tbl->lock)));
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rcu_assign_pointer(nht->hash_buckets[hash_val], n);
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write_unlock_bh(&tbl->lock);
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NEIGH_PRINTK2("neigh %p is created.\n", n);
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rc = n;
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@ -651,6 +676,12 @@ static inline void neigh_parms_put(struct neigh_parms *parms)
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neigh_parms_destroy(parms);
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}
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static void neigh_destroy_rcu(struct rcu_head *head)
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{
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struct neighbour *neigh = container_of(head, struct neighbour, rcu);
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kmem_cache_free(neigh->tbl->kmem_cachep, neigh);
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}
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/*
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* neighbour must already be out of the table;
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*
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@ -690,7 +721,7 @@ void neigh_destroy(struct neighbour *neigh)
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NEIGH_PRINTK2("neigh %p is destroyed.\n", neigh);
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atomic_dec(&neigh->tbl->entries);
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kmem_cache_free(neigh->tbl->kmem_cachep, neigh);
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call_rcu(&neigh->rcu, neigh_destroy_rcu);
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}
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EXPORT_SYMBOL(neigh_destroy);
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@ -731,7 +762,8 @@ static void neigh_connect(struct neighbour *neigh)
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static void neigh_periodic_work(struct work_struct *work)
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{
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struct neigh_table *tbl = container_of(work, struct neigh_table, gc_work.work);
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struct neighbour *n, **np;
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struct neighbour *n;
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struct neighbour __rcu **np;
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unsigned int i;
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struct neigh_hash_table *nht;
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@ -756,7 +788,8 @@ static void neigh_periodic_work(struct work_struct *work)
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for (i = 0 ; i <= nht->hash_mask; i++) {
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np = &nht->hash_buckets[i];
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while ((n = *np) != NULL) {
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while ((n = rcu_dereference_protected(*np,
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lockdep_is_held(&tbl->lock))) != NULL) {
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unsigned int state;
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write_lock(&n->lock);
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@ -1213,8 +1246,8 @@ static void neigh_hh_init(struct neighbour *n, struct dst_entry *dst,
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}
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/* This function can be used in contexts, where only old dev_queue_xmit
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worked, f.e. if you want to override normal output path (eql, shaper),
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but resolution is not made yet.
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* worked, f.e. if you want to override normal output path (eql, shaper),
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* but resolution is not made yet.
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*/
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int neigh_compat_output(struct sk_buff *skb)
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@ -2123,7 +2156,7 @@ static void neigh_update_notify(struct neighbour *neigh)
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static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
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struct netlink_callback *cb)
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{
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struct net * net = sock_net(skb->sk);
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struct net *net = sock_net(skb->sk);
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struct neighbour *n;
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int rc, h, s_h = cb->args[1];
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int idx, s_idx = idx = cb->args[2];
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@ -2132,13 +2165,14 @@ static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
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rcu_read_lock_bh();
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nht = rcu_dereference_bh(tbl->nht);
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read_lock(&tbl->lock);
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for (h = 0; h <= nht->hash_mask; h++) {
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if (h < s_h)
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continue;
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if (h > s_h)
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s_idx = 0;
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for (n = nht->hash_buckets[h], idx = 0; n; n = n->next) {
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for (n = rcu_dereference_bh(nht->hash_buckets[h]), idx = 0;
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n != NULL;
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n = rcu_dereference_bh(n->next)) {
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if (!net_eq(dev_net(n->dev), net))
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continue;
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if (idx < s_idx)
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@ -2150,13 +2184,12 @@ static int neigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
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rc = -1;
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goto out;
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}
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next:
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next:
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idx++;
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}
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}
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rc = skb->len;
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out:
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read_unlock(&tbl->lock);
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rcu_read_unlock_bh();
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cb->args[1] = h;
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cb->args[2] = idx;
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@ -2195,11 +2228,13 @@ void neigh_for_each(struct neigh_table *tbl, void (*cb)(struct neighbour *, void
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rcu_read_lock_bh();
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nht = rcu_dereference_bh(tbl->nht);
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read_lock(&tbl->lock);
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read_lock(&tbl->lock); /* avoid resizes */
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for (chain = 0; chain <= nht->hash_mask; chain++) {
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struct neighbour *n;
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for (n = nht->hash_buckets[chain]; n; n = n->next)
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for (n = rcu_dereference_bh(nht->hash_buckets[chain]);
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n != NULL;
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n = rcu_dereference_bh(n->next))
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cb(n, cookie);
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}
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read_unlock(&tbl->lock);
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@ -2217,16 +2252,20 @@ void __neigh_for_each_release(struct neigh_table *tbl,
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nht = rcu_dereference_protected(tbl->nht,
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lockdep_is_held(&tbl->lock));
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for (chain = 0; chain <= nht->hash_mask; chain++) {
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struct neighbour *n, **np;
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struct neighbour *n;
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struct neighbour __rcu **np;
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np = &nht->hash_buckets[chain];
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while ((n = *np) != NULL) {
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while ((n = rcu_dereference_protected(*np,
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lockdep_is_held(&tbl->lock))) != NULL) {
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int release;
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write_lock(&n->lock);
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release = cb(n);
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if (release) {
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*np = n->next;
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rcu_assign_pointer(*np,
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rcu_dereference_protected(n->next,
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lockdep_is_held(&tbl->lock)));
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n->dead = 1;
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} else
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np = &n->next;
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@ -2250,7 +2289,7 @@ static struct neighbour *neigh_get_first(struct seq_file *seq)
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state->flags &= ~NEIGH_SEQ_IS_PNEIGH;
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for (bucket = 0; bucket <= nht->hash_mask; bucket++) {
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n = nht->hash_buckets[bucket];
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n = rcu_dereference_bh(nht->hash_buckets[bucket]);
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while (n) {
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if (!net_eq(dev_net(n->dev), net))
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@ -2267,8 +2306,8 @@ static struct neighbour *neigh_get_first(struct seq_file *seq)
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break;
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if (n->nud_state & ~NUD_NOARP)
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break;
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next:
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n = n->next;
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next:
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n = rcu_dereference_bh(n->next);
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}
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if (n)
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@ -2292,7 +2331,7 @@ static struct neighbour *neigh_get_next(struct seq_file *seq,
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if (v)
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return n;
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}
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n = n->next;
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n = rcu_dereference_bh(n->next);
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while (1) {
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while (n) {
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@ -2309,8 +2348,8 @@ static struct neighbour *neigh_get_next(struct seq_file *seq,
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if (n->nud_state & ~NUD_NOARP)
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break;
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next:
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n = n->next;
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next:
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n = rcu_dereference_bh(n->next);
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}
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if (n)
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@ -2319,7 +2358,7 @@ static struct neighbour *neigh_get_next(struct seq_file *seq,
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if (++state->bucket > nht->hash_mask)
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break;
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n = nht->hash_buckets[state->bucket];
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n = rcu_dereference_bh(nht->hash_buckets[state->bucket]);
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}
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if (n && pos)
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@ -2417,7 +2456,6 @@ static void *neigh_get_idx_any(struct seq_file *seq, loff_t *pos)
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}
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void *neigh_seq_start(struct seq_file *seq, loff_t *pos, struct neigh_table *tbl, unsigned int neigh_seq_flags)
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__acquires(tbl->lock)
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__acquires(rcu_bh)
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{
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struct neigh_seq_state *state = seq->private;
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@ -2428,7 +2466,7 @@ void *neigh_seq_start(struct seq_file *seq, loff_t *pos, struct neigh_table *tbl
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rcu_read_lock_bh();
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state->nht = rcu_dereference_bh(tbl->nht);
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read_lock(&tbl->lock);
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return *pos ? neigh_get_idx_any(seq, pos) : SEQ_START_TOKEN;
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}
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EXPORT_SYMBOL(neigh_seq_start);
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@ -2461,13 +2499,8 @@ out:
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EXPORT_SYMBOL(neigh_seq_next);
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void neigh_seq_stop(struct seq_file *seq, void *v)
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__releases(tbl->lock)
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__releases(rcu_bh)
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{
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struct neigh_seq_state *state = seq->private;
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struct neigh_table *tbl = state->tbl;
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read_unlock(&tbl->lock);
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rcu_read_unlock_bh();
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}
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EXPORT_SYMBOL(neigh_seq_stop);
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