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Commit c5adde94 authored by Ying Xue's avatar Ying Xue Committed by David S. Miller
Browse files

netlink: eliminate nl_sk_hash_lock 



As rhashtable_lookup_compare_insert() can guarantee the process
of search and insertion is atomic, it's safe to eliminate the
nl_sk_hash_lock. After this, object insertion or removal will
be protected with per bucket lock on write side while object
lookup is guarded with rcu read lock on read side.

Signed-off-by: default avatarYing Xue <ying.xue@windriver.com>
Cc: Thomas Graf <tgraf@suug.ch>
Acked-by: default avatarThomas Graf <tgraf@suug.ch>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7a868d1e

net/netlink/af_netlink.c

+20 −13
Original line number Diff line number Diff line
@@ -98,7 +98,7 @@ static void netlink_skb_destructor(struct sk_buff *skb); 


/* nl_table locking explained:

 * Lookup and traversal are protected with an RCU read-side lock. Insertion

 * and removal are protected with nl_sk_hash_lock while using RCU list

 * and removal are protected with per bucket lock while using RCU list

 * modification primitives and may run in parallel to RCU protected lookups.

 * Destruction of the Netlink socket may only occur *after* nl_table_lock has

 * been acquired * either during or after the socket has been removed from
@@ -110,10 +110,6 @@ static atomic_t nl_table_users = ATOMIC_INIT(0); 


#define nl_deref_protected(X) rcu_dereference_protected(X, lockdep_is_held(&nl_table_lock));



/* Protects netlink socket hash table mutations */

DEFINE_MUTEX(nl_sk_hash_lock);

EXPORT_SYMBOL_GPL(nl_sk_hash_lock);



static ATOMIC_NOTIFIER_HEAD(netlink_chain);



static DEFINE_SPINLOCK(netlink_tap_lock);
@@ -998,6 +994,19 @@ static struct sock *__netlink_lookup(struct netlink_table *table, u32 portid, 
					 &netlink_compare, &arg);

}



static bool __netlink_insert(struct netlink_table *table, struct sock *sk,

			     struct net *net)

{

	struct netlink_compare_arg arg = {

		.net = net,

		.portid = nlk_sk(sk)->portid,

	};



	return rhashtable_lookup_compare_insert(&table->hash,

						&nlk_sk(sk)->node,

						&netlink_compare, &arg);

}



static struct sock *netlink_lookup(struct net *net, int protocol, u32 portid)

{

	struct netlink_table *table = &nl_table[protocol];
@@ -1043,9 +1052,7 @@ static int netlink_insert(struct sock *sk, struct net *net, u32 portid) 
	struct netlink_table *table = &nl_table[sk->sk_protocol];

	int err = -EADDRINUSE;



	mutex_lock(&nl_sk_hash_lock);

	if (__netlink_lookup(table, portid, net))

		goto err;

	lock_sock(sk);



	err = -EBUSY;

	if (nlk_sk(sk)->portid)
@@ -1058,10 +1065,12 @@ static int netlink_insert(struct sock *sk, struct net *net, u32 portid) 


	nlk_sk(sk)->portid = portid;

	sock_hold(sk);

	rhashtable_insert(&table->hash, &nlk_sk(sk)->node);

	if (__netlink_insert(table, sk, net))

		err = 0;

	else

		sock_put(sk);

err:

	mutex_unlock(&nl_sk_hash_lock);

	release_sock(sk);

	return err;

}
@@ -1069,13 +1078,11 @@ static void netlink_remove(struct sock *sk) 
{

	struct netlink_table *table;



	mutex_lock(&nl_sk_hash_lock);

	table = &nl_table[sk->sk_protocol];

	if (rhashtable_remove(&table->hash, &nlk_sk(sk)->node)) {

		WARN_ON(atomic_read(&sk->sk_refcnt) == 1);

		__sock_put(sk);

	}

	mutex_unlock(&nl_sk_hash_lock);



	netlink_table_grab();

	if (nlk_sk(sk)->subscriptions) {

net/netlink/af_netlink.h

+0 −1
Original line number Diff line number Diff line
@@ -74,6 +74,5 @@ struct netlink_table { 


extern struct netlink_table *nl_table;

extern rwlock_t nl_table_lock;

extern struct mutex nl_sk_hash_lock;



#endif

net/netlink/diag.c

+5 −5
Original line number Diff line number Diff line
@@ -103,7 +103,7 @@ static int __netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb, 
{

	struct netlink_table *tbl = &nl_table[protocol];

	struct rhashtable *ht = &tbl->hash;

	const struct bucket_table *htbl = rht_dereference(ht->tbl, ht);

	const struct bucket_table *htbl = rht_dereference_rcu(ht->tbl, ht);

	struct net *net = sock_net(skb->sk);

	struct netlink_diag_req *req;

	struct netlink_sock *nlsk;
@@ -115,7 +115,7 @@ static int __netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb, 
	for (i = 0; i < htbl->size; i++) {

		struct rhash_head *pos;



		rht_for_each_entry(nlsk, pos, htbl, i, node) {

		rht_for_each_entry_rcu(nlsk, pos, htbl, i, node) {

			sk = (struct sock *)nlsk;



			if (!net_eq(sock_net(sk), net))
@@ -172,7 +172,7 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) 


	req = nlmsg_data(cb->nlh);



	mutex_lock(&nl_sk_hash_lock);

	rcu_read_lock();

	read_lock(&nl_table_lock);



	if (req->sdiag_protocol == NDIAG_PROTO_ALL) {
@@ -186,7 +186,7 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) 
	} else {

		if (req->sdiag_protocol >= MAX_LINKS) {

			read_unlock(&nl_table_lock);

			mutex_unlock(&nl_sk_hash_lock);

			rcu_read_unlock();

			return -ENOENT;

		}
@@ -194,7 +194,7 @@ static int netlink_diag_dump(struct sk_buff *skb, struct netlink_callback *cb) 
	}



	read_unlock(&nl_table_lock);

	mutex_unlock(&nl_sk_hash_lock);

	rcu_read_unlock();



	return skb->len;

}