[IPSEC] xfrm: Undo afinfo lock proliferation

The number of locks used to manage afinfo structures can easily be reduced
down to one each for policy and state respectively.  This is based on the
observation that the write locks are only held by module insertion/removal
which are very rare events so there is no need to further differentiate
between the insertion of modules like ipv6 versus esp6.

The removal of the read locks in xfrm4_policy.c/xfrm6_policy.c might look
suspicious at first.  However, after you realise that nobody ever takes
the corresponding write lock you'll feel better :)

As far as I can gather it's an attempt to guard against the removal of
the corresponding modules.  Since neither module can be unloaded at all
we can leave it to whoever fixes up IPv6 unloading :)

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 37 insertions, 30 deletions

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index b469c8b..44b64a5 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -46,45 +46,43 @@ static DEFINE_SPINLOCK(xfrm_policy_gc_lock);
 
 static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family);
 static void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo);
+static struct xfrm_policy_afinfo *xfrm_policy_lock_afinfo(unsigned int family);
+static void xfrm_policy_unlock_afinfo(struct xfrm_policy_afinfo *afinfo);
 
 int xfrm_register_type(struct xfrm_type *type, unsigned short family)
 {
-	struct xfrm_policy_afinfo *afinfo = xfrm_policy_get_afinfo(family);
-	struct xfrm_type_map *typemap;
+	struct xfrm_policy_afinfo *afinfo = xfrm_policy_lock_afinfo(family);
+	struct xfrm_type **typemap;
 	int err = 0;
 
 	if (unlikely(afinfo == NULL))
 		return -EAFNOSUPPORT;
 	typemap = afinfo->type_map;
 
-	write_lock_bh(&typemap->lock);
-	if (likely(typemap->map[type->proto] == NULL))
-		typemap->map[type->proto] = type;
+	if (likely(typemap[type->proto] == NULL))
+		typemap[type->proto] = type;
 	else
 		err = -EEXIST;
-	write_unlock_bh(&typemap->lock);
-	xfrm_policy_put_afinfo(afinfo);
+	xfrm_policy_unlock_afinfo(afinfo);
 	return err;
 }
 EXPORT_SYMBOL(xfrm_register_type);
 
 int xfrm_unregister_type(struct xfrm_type *type, unsigned short family)
 {
-	struct xfrm_policy_afinfo *afinfo = xfrm_policy_get_afinfo(family);
-	struct xfrm_type_map *typemap;
+	struct xfrm_policy_afinfo *afinfo = xfrm_policy_lock_afinfo(family);
+	struct xfrm_type **typemap;
 	int err = 0;
 
 	if (unlikely(afinfo == NULL))
 		return -EAFNOSUPPORT;
 	typemap = afinfo->type_map;
 
-	write_lock_bh(&typemap->lock);
-	if (unlikely(typemap->map[type->proto] != type))
+	if (unlikely(typemap[type->proto] != type))
 		err = -ENOENT;
 	else
-		typemap->map[type->proto] = NULL;
-	write_unlock_bh(&typemap->lock);
-	xfrm_policy_put_afinfo(afinfo);
+		typemap[type->proto] = NULL;
+	xfrm_policy_unlock_afinfo(afinfo);
 	return err;
 }
 EXPORT_SYMBOL(xfrm_unregister_type);
@@ -92,7 +90,7 @@ EXPORT_SYMBOL(xfrm_unregister_type);
 struct xfrm_type *xfrm_get_type(u8 proto, unsigned short family)
 {
 	struct xfrm_policy_afinfo *afinfo;
-	struct xfrm_type_map *typemap;
+	struct xfrm_type **typemap;
 	struct xfrm_type *type;
 	int modload_attempted = 0;
 
@@ -102,11 +100,9 @@ retry:
 		return NULL;
 	typemap = afinfo->type_map;
 
-	read_lock(&typemap->lock);
-	type = typemap->map[proto];
+	type = typemap[proto];
 	if (unlikely(type && !try_module_get(type->owner)))
 		type = NULL;
-	read_unlock(&typemap->lock);
 	if (!type && !modload_attempted) {
 		xfrm_policy_put_afinfo(afinfo);
 		request_module("xfrm-type-%d-%d",
@@ -1306,17 +1302,31 @@ static struct xfrm_policy_afinfo *xfrm_policy_get_afinfo(unsigned short family)
 		return NULL;
 	read_lock(&xfrm_policy_afinfo_lock);
 	afinfo = xfrm_policy_afinfo[family];
-	if (likely(afinfo != NULL))
-		read_lock(&afinfo->lock);
-	read_unlock(&xfrm_policy_afinfo_lock);
+	if (unlikely(!afinfo))
+		read_unlock(&xfrm_policy_afinfo_lock);
 	return afinfo;
 }
 
 static void xfrm_policy_put_afinfo(struct xfrm_policy_afinfo *afinfo)
 {
-	if (unlikely(afinfo == NULL))
-		return;
-	read_unlock(&afinfo->lock);
+	read_unlock(&xfrm_policy_afinfo_lock);
+}
+
+static struct xfrm_policy_afinfo *xfrm_policy_lock_afinfo(unsigned int family)
+{
+	struct xfrm_policy_afinfo *afinfo;
+	if (unlikely(family >= NPROTO))
+		return NULL;
+	write_lock_bh(&xfrm_policy_afinfo_lock);
+	afinfo = xfrm_policy_afinfo[family];
+	if (unlikely(!afinfo))
+		write_unlock_bh(&xfrm_policy_afinfo_lock);
+	return afinfo;
+}
+
+static void xfrm_policy_unlock_afinfo(struct xfrm_policy_afinfo *afinfo)
+{
+	write_unlock_bh(&xfrm_policy_afinfo_lock);
 }
 
 static int xfrm_dev_event(struct notifier_block *this, unsigned long event, void *ptr)
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 93a2f36..ee62c23 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1103,17 +1103,14 @@ static struct xfrm_state_afinfo *xfrm_state_get_afinfo(unsigned short family)
 		return NULL;
 	read_lock(&xfrm_state_afinfo_lock);
 	afinfo = xfrm_state_afinfo[family];
-	if (likely(afinfo != NULL))
-		read_lock(&afinfo->lock);
-	read_unlock(&xfrm_state_afinfo_lock);
+	if (unlikely(!afinfo))
+		read_unlock(&xfrm_state_afinfo_lock);
 	return afinfo;
 }
 
 static void xfrm_state_put_afinfo(struct xfrm_state_afinfo *afinfo)
 {
-	if (unlikely(afinfo == NULL))
-		return;
-	read_unlock(&afinfo->lock);
+	read_unlock(&xfrm_state_afinfo_lock);
 }
 
 /* Temporarily located here until net/xfrm/xfrm_tunnel.c is created */