Replace rwlock on xfrm_policy_afinfo with rcu

xfrm_policy_afinfo is read mosly data structure.
Write on xfrm_policy_afinfo is done only at the
time of configuration.
So rwlocks can be safely replaced with RCU.

RCUs usage optimizes the performance.

Signed-off-by: Priyanka Jain <Priyanka.Jain@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 21 insertions, 18 deletions

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index c5a5165a5927..5ad4d2c4b83c 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -42,13 +42,14 @@ static DEFINE_SPINLOCK(xfrm_policy_sk_bundle_lock);
 static struct dst_entry *xfrm_policy_sk_bundles;
 static DEFINE_RWLOCK(xfrm_policy_lock);
 
-static DEFINE_RWLOCK(xfrm_policy_afinfo_lock);
-static struct xfrm_policy_afinfo *xfrm_policy_afinfo[NPROTO];
+static DEFINE_SPINLOCK(xfrm_policy_afinfo_lock);
+static struct xfrm_policy_afinfo __rcu *xfrm_policy_afinfo[NPROTO]
+                                                __read_mostly;
 
 static struct kmem_cache *xfrm_dst_cache __read_mostly;
 
 static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family);
-static void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo);
+static inline void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo);
 static void xfrm_init_pmtu(struct dst_entry *dst);
 static int stale_bundle(struct dst_entry *dst);
 static int xfrm_bundle_ok(struct xfrm_dst *xdst);
@@ -2418,7 +2419,7 @@ int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
                 return -EINVAL;
         if (unlikely(afinfo->family >= NPROTO))
                 return -EAFNOSUPPORT;
-        write_lock_bh(&xfrm_policy_afinfo_lock);
+        spin_lock_bh(&xfrm_policy_afinfo_lock);
         if (unlikely(xfrm_policy_afinfo[afinfo->family] != NULL))
                 err = -ENOBUFS;
         else {
@@ -2439,9 +2440,9 @@ int xfrm_policy_register_afinfo(struct xfrm_policy_afinfo *afinfo)
                         dst_ops->neigh_lookup = xfrm_neigh_lookup;
                 if (likely(afinfo->garbage_collect == NULL))
                         afinfo->garbage_collect = xfrm_garbage_collect_deferred;
-                xfrm_policy_afinfo[afinfo->family] = afinfo;
+                rcu_assign_pointer(xfrm_policy_afinfo[afinfo->family], afinfo);
         }
-        write_unlock_bh(&xfrm_policy_afinfo_lock);
+        spin_unlock_bh(&xfrm_policy_afinfo_lock);
 
         rtnl_lock();
         for_each_net(net) {
@@ -2474,13 +2475,14 @@ int xfrm_policy_unregister_afinfo(struct xfrm_policy_afinfo *afinfo)
                 return -EINVAL;
         if (unlikely(afinfo->family >= NPROTO))
                 return -EAFNOSUPPORT;
-        write_lock_bh(&xfrm_policy_afinfo_lock);
+        spin_lock_bh(&xfrm_policy_afinfo_lock);
         if (likely(xfrm_policy_afinfo[afinfo->family] != NULL)) {
                 if (unlikely(xfrm_policy_afinfo[afinfo->family] != afinfo))
                         err = -EINVAL;
                 else {
                         struct dst_ops *dst_ops = afinfo->dst_ops;
-                        xfrm_policy_afinfo[afinfo->family] = NULL;
+                        rcu_assign_pointer(xfrm_policy_afinfo[afinfo->family],
+                                                                        NULL);
                         dst_ops->kmem_cachep = NULL;
                         dst_ops->check = NULL;
                         dst_ops->negative_advice = NULL;
@@ -2488,7 +2490,8 @@ int xfrm_policy_unregister_afinfo(struct xfrm_policy_afinfo *afinfo)
                         afinfo->garbage_collect = NULL;
                 }
         }
-        write_unlock_bh(&xfrm_policy_afinfo_lock);
+        spin_unlock_bh(&xfrm_policy_afinfo_lock);
+        synchronize_rcu();
         return err;
 }
 EXPORT_SYMBOL(xfrm_policy_unregister_afinfo);
@@ -2497,16 +2500,16 @@ static void __net_init xfrm_dst_ops_init(struct net *net)
 {
         struct xfrm_policy_afinfo *afinfo;
 
-        read_lock_bh(&xfrm_policy_afinfo_lock);
-        afinfo = xfrm_policy_afinfo[AF_INET];
+        rcu_read_lock_bh();
+        afinfo = rcu_dereference(xfrm_policy_afinfo[AF_INET]);
         if (afinfo)
                 net->xfrm.xfrm4_dst_ops = *afinfo->dst_ops;
 #if IS_ENABLED(CONFIG_IPV6)
-        afinfo = xfrm_policy_afinfo[AF_INET6];
+        afinfo = rcu_dereference(xfrm_policy_afinfo[AF_INET6]);
         if (afinfo)
                 net->xfrm.xfrm6_dst_ops = *afinfo->dst_ops;
 #endif
-        read_unlock_bh(&xfrm_policy_afinfo_lock);
+        rcu_read_unlock_bh();
 }
 
 static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family)
@@ -2514,16 +2517,16 @@ static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family)
         struct xfrm_policy_afinfo *afinfo;
         if (unlikely(family >= NPROTO))
                 return NULL;
-        read_lock(&xfrm_policy_afinfo_lock);
-        afinfo = xfrm_policy_afinfo[family];
+        rcu_read_lock();
+        afinfo = rcu_dereference(xfrm_policy_afinfo[family]);
         if (unlikely(!afinfo))
-                read_unlock(&xfrm_policy_afinfo_lock);
+                rcu_read_unlock();
         return afinfo;
 }
 
-static void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo)
+static inline void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo)
 {
-        read_unlock(&xfrm_policy_afinfo_lock);
+        rcu_read_unlock();
 }
 
 static int xfrm_dev_event(struct notifier_block *this, unsigned long event, void *ptr)