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, 6 insertions, 34 deletions

diff --git a/net/tipc/link.c b/net/tipc/link.c
index 229d478494b9..c723ee90219d 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -835,7 +835,6 @@ int tipc_link_xmit(struct sk_buff *buf, u32 dest, u32 selector)
 	struct tipc_node *n_ptr;
 	int res = -ELINKCONG;
 
-	read_lock_bh(&tipc_net_lock);
 	n_ptr = tipc_node_find(dest);
 	if (n_ptr) {
 		tipc_node_lock(n_ptr);
@@ -848,7 +847,6 @@ int tipc_link_xmit(struct sk_buff *buf, u32 dest, u32 selector)
 	} else {
 		kfree_skb(buf);
 	}
-	read_unlock_bh(&tipc_net_lock);
 	return res;
 }
 
@@ -912,7 +910,6 @@ void tipc_link_names_xmit(struct list_head *message_list, u32 dest)
 	if (list_empty(message_list))
 		return;
 
-	read_lock_bh(&tipc_net_lock);
 	n_ptr = tipc_node_find(dest);
 	if (n_ptr) {
 		tipc_node_lock(n_ptr);
@@ -927,7 +924,6 @@ void tipc_link_names_xmit(struct list_head *message_list, u32 dest)
 		}
 		tipc_node_unlock(n_ptr);
 	}
-	read_unlock_bh(&tipc_net_lock);
 
 	/* discard the messages if they couldn't be sent */
 	list_for_each_safe(buf, temp_buf, ((struct sk_buff *)message_list)) {
@@ -989,7 +985,6 @@ again:
 	if (unlikely(res < 0))
 		return res;
 
-	read_lock_bh(&tipc_net_lock);
 	node = tipc_node_find(destaddr);
 	if (likely(node)) {
 		tipc_node_lock(node);
@@ -1000,7 +995,6 @@ again:
 							  &sender->max_pkt);
 exit:
 				tipc_node_unlock(node);
-				read_unlock_bh(&tipc_net_lock);
 				return res;
 			}
 
@@ -1017,7 +1011,6 @@ exit:
 			 */
 			sender->max_pkt = l_ptr->max_pkt;
 			tipc_node_unlock(node);
-			read_unlock_bh(&tipc_net_lock);
 
 
 			if ((msg_hdr_sz(hdr) + res) <= sender->max_pkt)
@@ -1028,7 +1021,6 @@ exit:
 		}
 		tipc_node_unlock(node);
 	}
-	read_unlock_bh(&tipc_net_lock);
 
 	/* Couldn't find a link to the destination node */
 	kfree_skb(buf);
@@ -1273,12 +1265,9 @@ static void link_reset_all(unsigned long addr)
 	char addr_string[16];
 	u32 i;
 
-	read_lock_bh(&tipc_net_lock);
 	n_ptr = tipc_node_find((u32)addr);
-	if (!n_ptr) {
-		read_unlock_bh(&tipc_net_lock);
+	if (!n_ptr)
 		return;	/* node no longer exists */
-	}
 
 	tipc_node_lock(n_ptr);
 
@@ -1293,7 +1282,6 @@ static void link_reset_all(unsigned long addr)
 	}
 
 	tipc_node_unlock(n_ptr);
-	read_unlock_bh(&tipc_net_lock);
 }
 
 static void link_retransmit_failure(struct tipc_link *l_ptr,
@@ -1458,7 +1446,6 @@ static int link_recv_buf_validate(struct sk_buff *buf)
  */
 void tipc_rcv(struct sk_buff *head, struct tipc_bearer *b_ptr)
 {
-	read_lock_bh(&tipc_net_lock);
 	while (head) {
 		struct tipc_node *n_ptr;
 		struct tipc_link *l_ptr;
@@ -1646,7 +1633,6 @@ unlock_discard:
 discard:
 		kfree_skb(buf);
 	}
-	read_unlock_bh(&tipc_net_lock);
 }
 
 /**
@@ -2408,8 +2394,6 @@ void tipc_link_set_queue_limits(struct tipc_link *l_ptr, u32 window)
 /* tipc_link_find_owner - locate owner node of link by link's name
  * @name: pointer to link name string
  * @bearer_id: pointer to index in 'node->links' array where the link was found.
- * Caller must hold 'tipc_net_lock' to ensure node and bearer are not deleted;
- * this also prevents link deletion.
  *
  * Returns pointer to node owning the link, or 0 if no matching link is found.
  */
@@ -2471,7 +2455,7 @@ static int link_value_is_valid(u16 cmd, u32 new_value)
  * @new_value: new value of link, bearer, or media setting
  * @cmd: which link, bearer, or media attribute to set (TIPC_CMD_SET_LINK_*)
  *
- * Caller must hold 'tipc_net_lock' to ensure link/bearer/media is not deleted.
+ * Caller must hold RTNL lock to ensure link/bearer/media is not deleted.
  *
  * Returns 0 if value updated and negative value on error.
  */
@@ -2577,9 +2561,7 @@ struct sk_buff *tipc_link_cmd_config(const void *req_tlv_area, int req_tlv_space
 						   " (cannot change setting on broadcast link)");
 	}
 
-	read_lock_bh(&tipc_net_lock);
 	res = link_cmd_set_value(args->name, new_value, cmd);
-	read_unlock_bh(&tipc_net_lock);
 	if (res)
 		return tipc_cfg_reply_error_string("cannot change link setting");
 
@@ -2613,22 +2595,18 @@ struct sk_buff *tipc_link_cmd_reset_stats(const void *req_tlv_area, int req_tlv_
 			return tipc_cfg_reply_error_string("link not found");
 		return tipc_cfg_reply_none();
 	}
-	read_lock_bh(&tipc_net_lock);
 	node = tipc_link_find_owner(link_name, &bearer_id);
-	if (!node) {
-		read_unlock_bh(&tipc_net_lock);
+	if (!node)
 		return tipc_cfg_reply_error_string("link not found");
-	}
+
 	tipc_node_lock(node);
 	l_ptr = node->links[bearer_id];
 	if (!l_ptr) {
 		tipc_node_unlock(node);
-		read_unlock_bh(&tipc_net_lock);
 		return tipc_cfg_reply_error_string("link not found");
 	}
 	link_reset_statistics(l_ptr);
 	tipc_node_unlock(node);
-	read_unlock_bh(&tipc_net_lock);
 	return tipc_cfg_reply_none();
 }
 
@@ -2661,18 +2639,15 @@ static int tipc_link_stats(const char *name, char *buf, const u32 buf_size)
 	if (!strcmp(name, tipc_bclink_name))
 		return tipc_bclink_stats(buf, buf_size);
 
-	read_lock_bh(&tipc_net_lock);
 	node = tipc_link_find_owner(name, &bearer_id);
-	if (!node) {
-		read_unlock_bh(&tipc_net_lock);
+	if (!node)
 		return 0;
-	}
+
 	tipc_node_lock(node);
 
 	l = node->links[bearer_id];
 	if (!l) {
 		tipc_node_unlock(node);
-		read_unlock_bh(&tipc_net_lock);
 		return 0;
 	}
 
@@ -2738,7 +2713,6 @@ static int tipc_link_stats(const char *name, char *buf, const u32 buf_size)
 			     (s->accu_queue_sz / s->queue_sz_counts) : 0);
 
 	tipc_node_unlock(node);
-	read_unlock_bh(&tipc_net_lock);
 	return ret;
 }
 
@@ -2789,7 +2763,6 @@ u32 tipc_link_get_max_pkt(u32 dest, u32 selector)
 	if (dest == tipc_own_addr)
 		return MAX_MSG_SIZE;
 
-	read_lock_bh(&tipc_net_lock);
 	n_ptr = tipc_node_find(dest);
 	if (n_ptr) {
 		tipc_node_lock(n_ptr);
@@ -2798,7 +2771,6 @@ u32 tipc_link_get_max_pkt(u32 dest, u32 selector)
 			res = l_ptr->max_pkt;
 		tipc_node_unlock(n_ptr);
 	}
-	read_unlock_bh(&tipc_net_lock);
 	return res;
 }