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Date: Mon, 12 Jan 2015 14:52:23 +0800
From: Ying Xue <ying.xue@...driver.com>
To: <tgraf@...g.ch>
CC: <davem@...emloft.net>, <netdev@...r.kernel.org>
Subject: [PATCH net-next v2 2/3] 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: Ying Xue <ying.xue@...driver.com>
Cc: Thomas Graf <tgraf@...g.ch>
---
net/netlink/af_netlink.c | 33 ++++++++++++++++++++-------------
net/netlink/af_netlink.h | 1 -
net/netlink/diag.c | 10 +++++-----
3 files changed, 25 insertions(+), 19 deletions(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 298e1df..01b702d 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -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);
- err = 0;
+ 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) {
diff --git a/net/netlink/af_netlink.h b/net/netlink/af_netlink.h
index fd96fa7..7518375 100644
--- a/net/netlink/af_netlink.h
+++ b/net/netlink/af_netlink.h
@@ -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
diff --git a/net/netlink/diag.c b/net/netlink/diag.c
index fcca36d..bb59a7e 100644
--- a/net/netlink/diag.c
+++ b/net/netlink/diag.c
@@ -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;
}
--
1.7.9.5
--
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