Merge branch 'tipc-next'

Ying Xue says:

====================
tipc: clean up bearer and node layer

This is another commit series which aims at facilitating future
changes to the locking policy around nodes, links and bearers.

Currently, the 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 any of these structures is being accessed. Obviously
the locking policy makes node, link and bearer components closely
bound together so that their relationship becomes extremely 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 to 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.

But, prior to these changes, we need to do some necessary cleanup and
code consolidation. This is what we do with this commit series. In a
later series we will replace net_lock with RTNL as well as RCU lock
to deploy the new locking policy.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 53 insertions, 54 deletions

diff --git a/net/tipc/node.c b/net/tipc/node.c
index 0b0f6c7da965..1d3a4999a70f 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -2,7 +2,7 @@
  * net/tipc/node.c: TIPC node management routines
  *
  * Copyright (c) 2000-2006, 2012 Ericsson AB
- * Copyright (c) 2005-2006, 2010-2011, Wind River Systems
+ * Copyright (c) 2005-2006, 2010-2014, Wind River Systems
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -44,13 +44,11 @@
 static void node_lost_contact(struct tipc_node *n_ptr);
 static void node_established_contact(struct tipc_node *n_ptr);
 
-static DEFINE_SPINLOCK(node_create_lock);
-
 static struct hlist_head node_htable[NODE_HTABLE_SIZE];
 LIST_HEAD(tipc_node_list);
 static u32 tipc_num_nodes;
-
-static atomic_t tipc_num_links = ATOMIC_INIT(0);
+static u32 tipc_num_links;
+static DEFINE_SPINLOCK(node_list_lock);
 
 /*
  * A trivial power-of-two bitmask technique is used for speed, since this
@@ -73,37 +71,26 @@ struct tipc_node *tipc_node_find(u32 addr)
 	if (unlikely(!in_own_cluster_exact(addr)))
 		return NULL;
 
-	hlist_for_each_entry(node, &node_htable[tipc_hashfn(addr)], hash) {
-		if (node->addr == addr)
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(node, &node_htable[tipc_hashfn(addr)], hash) {
+		if (node->addr == addr) {
+			rcu_read_unlock();
 			return node;
+		}
 	}
+	rcu_read_unlock();
 	return NULL;
 }
 
-/**
- * tipc_node_create - create neighboring node
- *
- * Currently, this routine is called by neighbor discovery code, which holds
- * net_lock for reading only.  We must take node_create_lock to ensure a node
- * isn't created twice if two different bearers discover the node at the same
- * time.  (It would be preferable to switch to holding net_lock in write mode,
- * but this is a non-trivial change.)
- */
 struct tipc_node *tipc_node_create(u32 addr)
 {
 	struct tipc_node *n_ptr, *temp_node;
 
-	spin_lock_bh(&node_create_lock);
-
-	n_ptr = tipc_node_find(addr);
-	if (n_ptr) {
-		spin_unlock_bh(&node_create_lock);
-		return n_ptr;
-	}
+	spin_lock_bh(&node_list_lock);
 
 	n_ptr = kzalloc(sizeof(*n_ptr), GFP_ATOMIC);
 	if (!n_ptr) {
-		spin_unlock_bh(&node_create_lock);
+		spin_unlock_bh(&node_list_lock);
 		pr_warn("Node creation failed, no memory\n");
 		return NULL;
 	}
@@ -114,31 +101,41 @@ struct tipc_node *tipc_node_create(u32 addr)
 	INIT_LIST_HEAD(&n_ptr->list);
 	INIT_LIST_HEAD(&n_ptr->nsub);
 
-	hlist_add_head(&n_ptr->hash, &node_htable[tipc_hashfn(addr)]);
+	hlist_add_head_rcu(&n_ptr->hash, &node_htable[tipc_hashfn(addr)]);
 
-	list_for_each_entry(temp_node, &tipc_node_list, list) {
+	list_for_each_entry_rcu(temp_node, &tipc_node_list, list) {
 		if (n_ptr->addr < temp_node->addr)
 			break;
 	}
-	list_add_tail(&n_ptr->list, &temp_node->list);
+	list_add_tail_rcu(&n_ptr->list, &temp_node->list);
 	n_ptr->block_setup = WAIT_PEER_DOWN;
 	n_ptr->signature = INVALID_NODE_SIG;
 
 	tipc_num_nodes++;
 
-	spin_unlock_bh(&node_create_lock);
+	spin_unlock_bh(&node_list_lock);
 	return n_ptr;
 }
 
-void tipc_node_delete(struct tipc_node *n_ptr)
+static void tipc_node_delete(struct tipc_node *n_ptr)
 {
-	list_del(&n_ptr->list);
-	hlist_del(&n_ptr->hash);
-	kfree(n_ptr);
+	list_del_rcu(&n_ptr->list);
+	hlist_del_rcu(&n_ptr->hash);
+	kfree_rcu(n_ptr, rcu);
 
 	tipc_num_nodes--;
 }
 
+void tipc_node_stop(void)
+{
+	struct tipc_node *node, *t_node;
+
+	spin_lock_bh(&node_list_lock);
+	list_for_each_entry_safe(node, t_node, &tipc_node_list, list)
+		tipc_node_delete(node);
+	spin_unlock_bh(&node_list_lock);
+}
+
 /**
  * tipc_node_link_up - handle addition of link
  *
@@ -243,7 +240,9 @@ int tipc_node_is_up(struct tipc_node *n_ptr)
 void tipc_node_attach_link(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
 {
 	n_ptr->links[l_ptr->b_ptr->identity] = l_ptr;
-	atomic_inc(&tipc_num_links);
+	spin_lock_bh(&node_list_lock);
+	tipc_num_links++;
+	spin_unlock_bh(&node_list_lock);
 	n_ptr->link_cnt++;
 }
 
@@ -255,7 +254,9 @@ void tipc_node_detach_link(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
 		if (l_ptr != n_ptr->links[i])
 			continue;
 		n_ptr->links[i] = NULL;
-		atomic_dec(&tipc_num_links);
+		spin_lock_bh(&node_list_lock);
+		tipc_num_links--;
+		spin_unlock_bh(&node_list_lock);
 		n_ptr->link_cnt--;
 	}
 }
@@ -341,27 +342,28 @@ struct sk_buff *tipc_node_get_nodes(const void *req_tlv_area, int req_tlv_space)
 		return tipc_cfg_reply_error_string(TIPC_CFG_INVALID_VALUE
 						   " (network address)");
 
-	read_lock_bh(&tipc_net_lock);
+	spin_lock_bh(&node_list_lock);
 	if (!tipc_num_nodes) {
-		read_unlock_bh(&tipc_net_lock);
+		spin_unlock_bh(&node_list_lock);
 		return tipc_cfg_reply_none();
 	}
 
 	/* For now, get space for all other nodes */
 	payload_size = TLV_SPACE(sizeof(node_info)) * tipc_num_nodes;
 	if (payload_size > 32768u) {
-		read_unlock_bh(&tipc_net_lock);
+		spin_unlock_bh(&node_list_lock);
 		return tipc_cfg_reply_error_string(TIPC_CFG_NOT_SUPPORTED
 						   " (too many nodes)");
 	}
+	spin_unlock_bh(&node_list_lock);
+
 	buf = tipc_cfg_reply_alloc(payload_size);
-	if (!buf) {
-		read_unlock_bh(&tipc_net_lock);
+	if (!buf)
 		return NULL;
-	}
 
 	/* Add TLVs for all nodes in scope */
-	list_for_each_entry(n_ptr, &tipc_node_list, list) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(n_ptr, &tipc_node_list, list) {
 		if (!tipc_in_scope(domain, n_ptr->addr))
 			continue;
 		node_info.addr = htonl(n_ptr->addr);
@@ -369,8 +371,7 @@ struct sk_buff *tipc_node_get_nodes(const void *req_tlv_area, int req_tlv_space)
 		tipc_cfg_append_tlv(buf, TIPC_TLV_NODE_INFO,
 				    &node_info, sizeof(node_info));
 	}
-
-	read_unlock_bh(&tipc_net_lock);
+	rcu_read_unlock();
 	return buf;
 }
 
@@ -393,21 +394,19 @@ struct sk_buff *tipc_node_get_links(const void *req_tlv_area, int req_tlv_space)
 	if (!tipc_own_addr)
 		return tipc_cfg_reply_none();
 
-	read_lock_bh(&tipc_net_lock);
-
+	spin_lock_bh(&node_list_lock);
 	/* Get space for all unicast links + broadcast link */
-	payload_size = TLV_SPACE(sizeof(link_info)) *
-		(atomic_read(&tipc_num_links) + 1);
+	payload_size = TLV_SPACE((sizeof(link_info)) * (tipc_num_links + 1));
 	if (payload_size > 32768u) {
-		read_unlock_bh(&tipc_net_lock);
+		spin_unlock_bh(&node_list_lock);
 		return tipc_cfg_reply_error_string(TIPC_CFG_NOT_SUPPORTED
 						   " (too many links)");
 	}
+	spin_unlock_bh(&node_list_lock);
+
 	buf = tipc_cfg_reply_alloc(payload_size);
-	if (!buf) {
-		read_unlock_bh(&tipc_net_lock);
+	if (!buf)
 		return NULL;
-	}
 
 	/* Add TLV for broadcast link */
 	link_info.dest = htonl(tipc_cluster_mask(tipc_own_addr));
@@ -416,7 +415,8 @@ struct sk_buff *tipc_node_get_links(const void *req_tlv_area, int req_tlv_space)
 	tipc_cfg_append_tlv(buf, TIPC_TLV_LINK_INFO, &link_info, sizeof(link_info));
 
 	/* Add TLVs for any other links in scope */
-	list_for_each_entry(n_ptr, &tipc_node_list, list) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(n_ptr, &tipc_node_list, list) {
 		u32 i;
 
 		if (!tipc_in_scope(domain, n_ptr->addr))
@@ -433,7 +433,6 @@ struct sk_buff *tipc_node_get_links(const void *req_tlv_area, int req_tlv_space)
 		}
 		tipc_node_unlock(n_ptr);
 	}
-
-	read_unlock_bh(&tipc_net_lock);
+	rcu_read_unlock();
 	return buf;
 }