xfrm: replace rwlock on xfrm_state_afinfo with rcu

Similar to commit 418a99ac6ad487dc9c42e6b0e85f941af56330f2
(Replace rwlock on xfrm_policy_afinfo with rcu), the rwlock
on xfrm_state_afinfo can be replaced by RCU too.

Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

1 files changed, 16 insertions, 17 deletions

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 05db2362a231..64780a6f7b86 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -158,8 +158,8 @@ out_unlock:
         mutex_unlock(&hash_resize_mutex);
 }
 
-static DEFINE_RWLOCK(xfrm_state_afinfo_lock);
-static struct xfrm_state_afinfo *xfrm_state_afinfo[NPROTO];
+static DEFINE_SPINLOCK(xfrm_state_afinfo_lock);
+static struct xfrm_state_afinfo __rcu *xfrm_state_afinfo[NPROTO];
 
 static DEFINE_SPINLOCK(xfrm_state_gc_lock);
 
@@ -173,17 +173,16 @@ static struct xfrm_state_afinfo *xfrm_state_lock_afinfo(unsigned int family)
         struct xfrm_state_afinfo *afinfo;
         if (unlikely(family >= NPROTO))
                 return NULL;
-        write_lock_bh(&xfrm_state_afinfo_lock);
+        spin_lock_bh(&xfrm_state_afinfo_lock);
         afinfo = xfrm_state_afinfo[family];
         if (unlikely(!afinfo))
-                write_unlock_bh(&xfrm_state_afinfo_lock);
+                spin_unlock_bh(&xfrm_state_afinfo_lock);
         return afinfo;
 }
 
 static void xfrm_state_unlock_afinfo(struct xfrm_state_afinfo *afinfo)
-        __releases(xfrm_state_afinfo_lock)
 {
-        write_unlock_bh(&xfrm_state_afinfo_lock);
+        spin_unlock_bh(&xfrm_state_afinfo_lock);
 }
 
 int xfrm_register_type(const struct xfrm_type *type, unsigned short family)
@@ -1845,12 +1844,12 @@ int xfrm_state_register_afinfo(struct xfrm_state_afinfo *afinfo)
                 return -EINVAL;
         if (unlikely(afinfo->family >= NPROTO))
                 return -EAFNOSUPPORT;
-        write_lock_bh(&xfrm_state_afinfo_lock);
+        spin_lock_bh(&xfrm_state_afinfo_lock);
         if (unlikely(xfrm_state_afinfo[afinfo->family] != NULL))
                 err = -ENOBUFS;
         else
-                xfrm_state_afinfo[afinfo->family] = afinfo;
-        write_unlock_bh(&xfrm_state_afinfo_lock);
+                rcu_assign_pointer(xfrm_state_afinfo[afinfo->family], afinfo);
+        spin_unlock_bh(&xfrm_state_afinfo_lock);
         return err;
 }
 EXPORT_SYMBOL(xfrm_state_register_afinfo);
@@ -1862,14 +1861,15 @@ int xfrm_state_unregister_afinfo(struct xfrm_state_afinfo *afinfo)
                 return -EINVAL;
         if (unlikely(afinfo->family >= NPROTO))
                 return -EAFNOSUPPORT;
-        write_lock_bh(&xfrm_state_afinfo_lock);
+        spin_lock_bh(&xfrm_state_afinfo_lock);
         if (likely(xfrm_state_afinfo[afinfo->family] != NULL)) {
                 if (unlikely(xfrm_state_afinfo[afinfo->family] != afinfo))
                         err = -EINVAL;
                 else
-                        xfrm_state_afinfo[afinfo->family] = NULL;
+                        RCU_INIT_POINTER(xfrm_state_afinfo[afinfo->family], NULL);
         }
-        write_unlock_bh(&xfrm_state_afinfo_lock);
+        spin_unlock_bh(&xfrm_state_afinfo_lock);
+        synchronize_rcu();
         return err;
 }
 EXPORT_SYMBOL(xfrm_state_unregister_afinfo);
@@ -1879,17 +1879,16 @@ static struct xfrm_state_afinfo *xfrm_state_get_afinfo(unsigned int family)
         struct xfrm_state_afinfo *afinfo;
         if (unlikely(family >= NPROTO))
                 return NULL;
-        read_lock(&xfrm_state_afinfo_lock);
-        afinfo = xfrm_state_afinfo[family];
+        rcu_read_lock();
+        afinfo = rcu_dereference(xfrm_state_afinfo[family]);
         if (unlikely(!afinfo))
-                read_unlock(&xfrm_state_afinfo_lock);
+                rcu_read_unlock();
         return afinfo;
 }
 
 static void xfrm_state_put_afinfo(struct xfrm_state_afinfo *afinfo)
-        __releases(xfrm_state_afinfo_lock)
 {
-        read_unlock(&xfrm_state_afinfo_lock);
+        rcu_read_unlock();
 }
 
 /* Temporarily located here until net/xfrm/xfrm_tunnel.c is created */