tipc: purge tipc_net_lock lock

Now tipc routing hierarchy comprises the structures 'node', 'link'and
'bearer'. The whole hierarchy is protected by a big read/write lock,
tipc_net_lock, to ensure that nothing is added or removed while code
is accessing any of these structures. Obviously the locking policy
makes node, link and bearer components closely bound together so that
their relationship becomes unnecessarily complex. In the worst case,
such locking policy not only has a negative influence on performance,
but also it's prone to lead to deadlock occasionally.

In order o decouple the complex relationship between bearer and node
as well as link, the locking policy is adjusted as follows:

- Bearer level
  RTNL lock is used on update side, and RCU is used on read side.
  Meanwhile, all bearer instances including broadcast bearer are
  saved into bearer_list array.

- Node and link level
  All node instances are saved into two tipc_node_list and node_htable
  lists. The two lists are protected by node_list_lock on write side,
  and they are guarded with RCU lock on read side. All members in node
  structure including link instances are protected by node spin lock.

- The relationship between bearer and node
  When link accesses bearer, it first needs to find the bearer with
  its bearer identity from the bearer_list array. When bearer accesses
  node, it can iterate the node_htable hash list with the node
  address to find the corresponding node.

In the new locking policy, every component has its private locking
solution and the relationship between bearer and node is very simple,
that is, they can find each other with node address or bearer identity
from node_htable hash list or bearer_list array.

Until now above all changes have been done, so tipc_net_lock can be
removed safely.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Tested-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 21 deletions

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index c24a351..1bd96eb 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -198,7 +198,6 @@ struct sk_buff *tipc_bearer_get_names(void)
 	if (!buf)
 		return NULL;
 
-	read_lock_bh(&tipc_net_lock);
 	for (i = 0; media_info_array[i] != NULL; i++) {
 		for (j = 0; j < MAX_BEARERS; j++) {
 			b = rtnl_dereference(bearer_list[j]);
@@ -211,7 +210,6 @@ struct sk_buff *tipc_bearer_get_names(void)
 			}
 		}
 	}
-	read_unlock_bh(&tipc_net_lock);
 	return buf;
 }
 
@@ -285,13 +283,11 @@ int tipc_enable_bearer(const char *name, u32 disc_domain, u32 priority)
 		return -EINVAL;
 	}
 
-	write_lock_bh(&tipc_net_lock);
-
 	m_ptr = tipc_media_find(b_names.media_name);
 	if (!m_ptr) {
 		pr_warn("Bearer <%s> rejected, media <%s> not registered\n",
 			name, b_names.media_name);
-		goto exit;
+		return -EINVAL;
 	}
 
 	if (priority == TIPC_MEDIA_LINK_PRI)
@@ -309,14 +305,14 @@ restart:
 		if (!strcmp(name, b_ptr->name)) {
 			pr_warn("Bearer <%s> rejected, already enabled\n",
 				name);
-			goto exit;
+			return -EINVAL;
 		}
 		if ((b_ptr->priority == priority) &&
 		    (++with_this_prio > 2)) {
 			if (priority-- == 0) {
 				pr_warn("Bearer <%s> rejected, duplicate priority\n",
 					name);
-				goto exit;
+				return -EINVAL;
 			}
 			pr_warn("Bearer <%s> priority adjustment required %u->%u\n",
 				name, priority + 1, priority);
@@ -326,21 +322,20 @@ restart:
 	if (bearer_id >= MAX_BEARERS) {
 		pr_warn("Bearer <%s> rejected, bearer limit reached (%u)\n",
 			name, MAX_BEARERS);
-		goto exit;
+		return -EINVAL;
 	}
 
 	b_ptr = kzalloc(sizeof(*b_ptr), GFP_ATOMIC);
-	if (!b_ptr) {
-		res = -ENOMEM;
-		goto exit;
-	}
+	if (!b_ptr)
+		return -ENOMEM;
+
 	strcpy(b_ptr->name, name);
 	b_ptr->media = m_ptr;
 	res = m_ptr->enable_media(b_ptr);
 	if (res) {
 		pr_warn("Bearer <%s> rejected, enable failure (%d)\n",
 			name, -res);
-		goto exit;
+		return -EINVAL;
 	}
 
 	b_ptr->identity = bearer_id;
@@ -355,7 +350,7 @@ restart:
 		bearer_disable(b_ptr, false);
 		pr_warn("Bearer <%s> rejected, discovery object creation failed\n",
 			name);
-		goto exit;
+		return -EINVAL;
 	}
 
 	rcu_assign_pointer(bearer_list[bearer_id], b_ptr);
@@ -363,8 +358,6 @@ restart:
 	pr_info("Enabled bearer <%s>, discovery domain %s, priority %u\n",
 		name,
 		tipc_addr_string_fill(addr_string, disc_domain), priority);
-exit:
-	write_unlock_bh(&tipc_net_lock);
 	return res;
 }
 
@@ -373,19 +366,17 @@ exit:
  */
 static int tipc_reset_bearer(struct tipc_bearer *b_ptr)
 {
-	read_lock_bh(&tipc_net_lock);
 	pr_info("Resetting bearer <%s>\n", b_ptr->name);
 	tipc_disc_delete(b_ptr->link_req);
 	tipc_link_reset_list(b_ptr->identity);
 	tipc_disc_create(b_ptr, &b_ptr->bcast_addr);
-	read_unlock_bh(&tipc_net_lock);
 	return 0;
 }
 
 /**
  * bearer_disable
  *
- * Note: This routine assumes caller holds tipc_net_lock.
+ * Note: This routine assumes caller holds RTNL lock.
  */
 static void bearer_disable(struct tipc_bearer *b_ptr, bool shutting_down)
 {
@@ -412,7 +403,6 @@ int tipc_disable_bearer(const char *name)
 	struct tipc_bearer *b_ptr;
 	int res;
 
-	write_lock_bh(&tipc_net_lock);
 	b_ptr = tipc_bearer_find(name);
 	if (b_ptr == NULL) {
 		pr_warn("Attempt to disable unknown bearer <%s>\n", name);
@@ -421,7 +411,6 @@ int tipc_disable_bearer(const char *name)
 		bearer_disable(b_ptr, false);
 		res = 0;
 	}
-	write_unlock_bh(&tipc_net_lock);
 	return res;
 }