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l2tp: Convert rwlock to RCU
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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: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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James Chapman authored and David S. Miller committed Apr 3, 2010
1 parent 309795f commit e02d494
Showing 1 changed file with 42 additions and 36 deletions.
78 changes: 42 additions & 36 deletions net/l2tp/l2tp_core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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;
}
Expand All @@ -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;
}
Expand All @@ -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;
}
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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,
l2tp_session_id_hash_2(pn, session_id));
write_unlock_bh(&pn->l2tp_session_hlist_lock);
spin_lock_bh(&pn->l2tp_session_hlist_lock);
hlist_add_head_rcu(&session->global_hlist,
l2tp_session_id_hash_2(pn, session_id));
spin_unlock_bh(&pn->l2tp_session_hlist_lock);
synchronize_rcu();
}

/* Ignore management session in session count value */
Expand All @@ -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)
Expand Down

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