[INET]: Use list_head-s in inetpeer.c

The inetpeer.c tracks the LRU list of inet_perr-s, but makes
it by hands. Use the list_head-s for this.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/inetpeer.h

@@ -22,7 +22,7 @@ struct inet_peer
 	__be32			v4daddr;	/* peer's address */
 	__u16			avl_height;
 	__u16			ip_id_count;	/* IP ID for the next packet */
-	struct inet_peer	*unused_next, **unused_prevp;
+	struct list_head	unused;
 	__u32			dtime;		/* the time of last use of not
 						 * referenced entries */
 	atomic_t		refcnt;

net/ipv4/inetpeer.c

@@ -61,7 +61,7 @@
  *  4.  Global variable peer_total is modified under the pool lock.
  *  5.  struct inet_peer fields modification:
  *		avl_left, avl_right, avl_parent, avl_height: pool lock
- *		unused_next, unused_prevp: unused node list lock
+ *		unused: unused node list lock
  *		refcnt: atomically against modifications on other CPU;
  *		   usually under some other lock to prevent node disappearing
  *		dtime: unused node list lock
@@ -94,8 +94,7 @@ int inet_peer_maxttl __read_mostly = 10 * 60 * HZ;	/* usual time to live: 10 min
 int inet_peer_gc_mintime __read_mostly = 10 * HZ;
 int inet_peer_gc_maxtime __read_mostly = 120 * HZ;
 
-static struct inet_peer *inet_peer_unused_head;
-static struct inet_peer **inet_peer_unused_tailp = &inet_peer_unused_head;
+static LIST_HEAD(unused_peers);
 static DEFINE_SPINLOCK(inet_peer_unused_lock);
 
 static void peer_check_expire(unsigned long dummy);
@@ -138,15 +137,7 @@ void __init inet_initpeers(void)
 static void unlink_from_unused(struct inet_peer *p)
 {
 	spin_lock_bh(&inet_peer_unused_lock);
-	if (p->unused_prevp != NULL) {
-		/* On unused list. */
-		*p->unused_prevp = p->unused_next;
-		if (p->unused_next != NULL)
-			p->unused_next->unused_prevp = p->unused_prevp;
-		else
-			inet_peer_unused_tailp = p->unused_prevp;
-		p->unused_prevp = NULL; /* mark it as removed */
-	}
+	list_del_init(&p->unused);
 	spin_unlock_bh(&inet_peer_unused_lock);
 }
 
@@ -337,24 +328,24 @@ static void unlink_from_pool(struct inet_peer *p)
 /* May be called with local BH enabled. */
 static int cleanup_once(unsigned long ttl)
 {
-	struct inet_peer *p;
+	struct inet_peer *p = NULL;
 
 	/* Remove the first entry from the list of unused nodes. */
 	spin_lock_bh(&inet_peer_unused_lock);
-	p = inet_peer_unused_head;
-	if (p != NULL) {
-		__u32 delta = (__u32)jiffies - p->dtime;
+	if (!list_empty(&unused_peers)) {
+		__u32 delta;
+
+		p = list_first_entry(&unused_peers, struct inet_peer, unused);
+		delta = (__u32)jiffies - p->dtime;
+
 		if (delta < ttl) {
 			/* Do not prune fresh entries. */
 			spin_unlock_bh(&inet_peer_unused_lock);
 			return -1;
 		}
-		inet_peer_unused_head = p->unused_next;
-		if (p->unused_next != NULL)
-			p->unused_next->unused_prevp = p->unused_prevp;
-		else
-			inet_peer_unused_tailp = p->unused_prevp;
-		p->unused_prevp = NULL; /* mark as not on the list */
+
+		list_del_init(&p->unused);
+
 		/* Grab an extra reference to prevent node disappearing
 		 * before unlink_from_pool() call. */
 		atomic_inc(&p->refcnt);
@@ -412,7 +403,7 @@ struct inet_peer *inet_getpeer(__be32 daddr, int create)
 
 	/* Link the node. */
 	link_to_pool(n);
-	n->unused_prevp = NULL; /* not on the list */
+	INIT_LIST_HEAD(&n->unused);
 	peer_total++;
 	write_unlock_bh(&peer_pool_lock);
 
@@ -467,10 +458,7 @@ void inet_putpeer(struct inet_peer *p)
 {
 	spin_lock_bh(&inet_peer_unused_lock);
 	if (atomic_dec_and_test(&p->refcnt)) {
-		p->unused_prevp = inet_peer_unused_tailp;
-		p->unused_next = NULL;
-		*inet_peer_unused_tailp = p;
-		inet_peer_unused_tailp = &p->unused_next;
+		list_add_tail(&p->unused, &unused_peers);
 		p->dtime = (__u32)jiffies;
 	}
 	spin_unlock_bh(&inet_peer_unused_lock);