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Commit e02d494d authored by James Chapman's avatar James Chapman Committed by David S. Miller
Browse files

l2tp: Convert rwlock to RCU 



Reader/write locks are discouraged because they are slower than spin
locks. So this patch converts the rwlocks used in the per_net structs
to rcu.

Signed-off-by: default avatarJames Chapman <jchapman@katalix.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 309795f4

net/l2tp/l2tp_core.c

+42 −36
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/module.h>

#include <linux/string.h>

#include <linux/list.h>

#include <linux/rculist.h>

#include <linux/uaccess.h>



#include <linux/kernel.h>
@@ -105,9 +106,9 @@ static atomic_t l2tp_session_count; 
static unsigned int l2tp_net_id;

struct l2tp_net {

	struct list_head l2tp_tunnel_list;

	rwlock_t l2tp_tunnel_list_lock;

	spinlock_t l2tp_tunnel_list_lock;

	struct hlist_head l2tp_session_hlist[L2TP_HASH_SIZE_2];

	rwlock_t l2tp_session_hlist_lock;

	spinlock_t l2tp_session_hlist_lock;

};



static inline struct l2tp_net *l2tp_pernet(struct net *net)
@@ -139,14 +140,14 @@ static struct l2tp_session *l2tp_session_find_2(struct net *net, u32 session_id) 
	struct l2tp_session *session;

	struct hlist_node *walk;



	read_lock_bh(&pn->l2tp_session_hlist_lock);

	hlist_for_each_entry(session, walk, session_list, global_hlist) {

	rcu_read_lock_bh();

	hlist_for_each_entry_rcu(session, walk, session_list, global_hlist) {

		if (session->session_id == session_id) {

			read_unlock_bh(&pn->l2tp_session_hlist_lock);

			rcu_read_unlock_bh();

			return session;

		}

	}

	read_unlock_bh(&pn->l2tp_session_hlist_lock);

	rcu_read_unlock_bh();



	return NULL;

}
@@ -225,17 +226,17 @@ struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname) 
	struct hlist_node *walk;

	struct l2tp_session *session;



	read_lock_bh(&pn->l2tp_session_hlist_lock);

	rcu_read_lock_bh();

	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {

		hlist_for_each_entry(session, walk, &pn->l2tp_session_hlist[hash], global_hlist) {

		hlist_for_each_entry_rcu(session, walk, &pn->l2tp_session_hlist[hash], global_hlist) {

			if (!strcmp(session->ifname, ifname)) {

				read_unlock_bh(&pn->l2tp_session_hlist_lock);

				rcu_read_unlock_bh();

				return session;

			}

		}

	}



	read_unlock_bh(&pn->l2tp_session_hlist_lock);

	rcu_read_unlock_bh();



	return NULL;

}
@@ -248,14 +249,14 @@ struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id) 
	struct l2tp_tunnel *tunnel;

	struct l2tp_net *pn = l2tp_pernet(net);



	read_lock_bh(&pn->l2tp_tunnel_list_lock);

	list_for_each_entry(tunnel, &pn->l2tp_tunnel_list, list) {

	rcu_read_lock_bh();

	list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {

		if (tunnel->tunnel_id == tunnel_id) {

			read_unlock_bh(&pn->l2tp_tunnel_list_lock);

			rcu_read_unlock_bh();

			return tunnel;

		}

	}

	read_unlock_bh(&pn->l2tp_tunnel_list_lock);

	rcu_read_unlock_bh();



	return NULL;

}
@@ -267,15 +268,15 @@ struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth) 
	struct l2tp_tunnel *tunnel;

	int count = 0;



	read_lock_bh(&pn->l2tp_tunnel_list_lock);

	list_for_each_entry(tunnel, &pn->l2tp_tunnel_list, list) {

	rcu_read_lock_bh();

	list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) {

		if (++count > nth) {

			read_unlock_bh(&pn->l2tp_tunnel_list_lock);

			rcu_read_unlock_bh();

			return tunnel;

		}

	}



	read_unlock_bh(&pn->l2tp_tunnel_list_lock);

	rcu_read_unlock_bh();



	return NULL;

}
@@ -1167,9 +1168,10 @@ void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel) 
			if (tunnel->version != L2TP_HDR_VER_2) {

				struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);



				write_lock_bh(&pn->l2tp_session_hlist_lock);

				hlist_del_init(&session->global_hlist);

				write_unlock_bh(&pn->l2tp_session_hlist_lock);

				spin_lock_bh(&pn->l2tp_session_hlist_lock);

				hlist_del_init_rcu(&session->global_hlist);

				spin_unlock_bh(&pn->l2tp_session_hlist_lock);

				synchronize_rcu();

			}



			if (session->session_close != NULL)
@@ -1206,9 +1208,10 @@ void l2tp_tunnel_free(struct l2tp_tunnel *tunnel) 
	       "%s: free...\n", tunnel->name);



	/* Remove from tunnel list */

	write_lock_bh(&pn->l2tp_tunnel_list_lock);

	list_del_init(&tunnel->list);

	write_unlock_bh(&pn->l2tp_tunnel_list_lock);

	spin_lock_bh(&pn->l2tp_tunnel_list_lock);

	list_del_rcu(&tunnel->list);

	spin_unlock_bh(&pn->l2tp_tunnel_list_lock);

	synchronize_rcu();



	atomic_dec(&l2tp_tunnel_count);

	kfree(tunnel);
@@ -1310,9 +1313,10 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32 


	/* Add tunnel to our list */

	INIT_LIST_HEAD(&tunnel->list);

	write_lock_bh(&pn->l2tp_tunnel_list_lock);

	list_add(&tunnel->list, &pn->l2tp_tunnel_list);

	write_unlock_bh(&pn->l2tp_tunnel_list_lock);

	spin_lock_bh(&pn->l2tp_tunnel_list_lock);

	list_add_rcu(&tunnel->list, &pn->l2tp_tunnel_list);

	spin_unlock_bh(&pn->l2tp_tunnel_list_lock);

	synchronize_rcu();

	atomic_inc(&l2tp_tunnel_count);



	/* Bump the reference count. The tunnel context is deleted
@@ -1370,9 +1374,10 @@ void l2tp_session_free(struct l2tp_session *session) 
		if (tunnel->version != L2TP_HDR_VER_2) {

			struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);



			write_lock_bh(&pn->l2tp_session_hlist_lock);

			hlist_del_init(&session->global_hlist);

			write_unlock_bh(&pn->l2tp_session_hlist_lock);

			spin_lock_bh(&pn->l2tp_session_hlist_lock);

			hlist_del_init_rcu(&session->global_hlist);

			spin_unlock_bh(&pn->l2tp_session_hlist_lock);

			synchronize_rcu();

		}



		if (session->session_id != 0)
@@ -1494,10 +1499,11 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn 
		if (tunnel->version != L2TP_HDR_VER_2) {

			struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);



			write_lock_bh(&pn->l2tp_session_hlist_lock);

			hlist_add_head(&session->global_hlist,

			spin_lock_bh(&pn->l2tp_session_hlist_lock);

			hlist_add_head_rcu(&session->global_hlist,

					   l2tp_session_id_hash_2(pn, session_id));

			write_unlock_bh(&pn->l2tp_session_hlist_lock);

			spin_unlock_bh(&pn->l2tp_session_hlist_lock);

			synchronize_rcu();

		}



		/* Ignore management session in session count value */
@@ -1524,12 +1530,12 @@ static __net_init int l2tp_init_net(struct net *net) 
		return -ENOMEM;



	INIT_LIST_HEAD(&pn->l2tp_tunnel_list);

	rwlock_init(&pn->l2tp_tunnel_list_lock);

	spin_lock_init(&pn->l2tp_tunnel_list_lock);



	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++)

		INIT_HLIST_HEAD(&pn->l2tp_session_hlist[hash]);



	rwlock_init(&pn->l2tp_session_hlist_lock);

	spin_lock_init(&pn->l2tp_session_hlist_lock);



	err = net_assign_generic(net, l2tp_net_id, pn);

	if (err)