X-Git-Url: http://git.alex.org.uk

diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
index 3c513ce..824e5f1 100644
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -3,8 +3,6 @@
  *
  *  This source is covered by the GNU GPL, the same as all kernel sources.
  *
- *  Version:	$Id: inetpeer.c,v 1.7 2001/09/20 21:22:50 davem Exp $
- *
  *  Authors:	Andrey V. Savochkin <saw@msu.ru>
  */
 
@@ -14,13 +12,14 @@
 #include <linux/interrupt.h>
 #include <linux/spinlock.h>
 #include <linux/random.h>
-#include <linux/sched.h>
 #include <linux/timer.h>
 #include <linux/time.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/net.h>
+#include <net/ip.h>
 #include <net/inetpeer.h>
+#include <net/secure_seq.h>
 
 /*
  *  Theory of operations.
@@ -53,58 +52,73 @@
  *  lookups performed with disabled BHs.
  *
  *  Serialisation issues.
- *  1.  Nodes may appear in the tree only with the pool write lock held.
- *  2.  Nodes may disappear from the tree only with the pool write lock held
+ *  1.  Nodes may appear in the tree only with the pool lock held.
+ *  2.  Nodes may disappear from the tree only with the pool lock held
  *      AND reference count being 0.
  *  3.  Nodes appears and disappears from unused node list only under
  *      "inet_peer_unused_lock".
  *  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
- *		v4daddr: unchangeable
- *		ip_id_count: idlock
+ *		daddr: unchangeable
+ *		ip_id_count: atomic value (no lock needed)
  */
 
-/* Exported for inet_getid inline function.  */
-DEFINE_SPINLOCK(inet_peer_idlock);
-
-static kmem_cache_t *peer_cachep;
+static struct kmem_cache *peer_cachep __read_mostly;
 
 #define node_height(x) x->avl_height
-static struct inet_peer peer_fake_node = {
-	.avl_left	= &peer_fake_node,
-	.avl_right	= &peer_fake_node,
+
+#define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
+#define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
+static const struct inet_peer peer_fake_node = {
+	.avl_left	= peer_avl_empty_rcu,
+	.avl_right	= peer_avl_empty_rcu,
 	.avl_height	= 0
 };
-#define peer_avl_empty (&peer_fake_node)
-static struct inet_peer *peer_root = peer_avl_empty;
-static DEFINE_RWLOCK(peer_pool_lock);
+
+struct inet_peer_base {
+	struct inet_peer __rcu *root;
+	spinlock_t	lock;
+	int		total;
+};
+
+static struct inet_peer_base v4_peers = {
+	.root		= peer_avl_empty_rcu,
+	.lock		= __SPIN_LOCK_UNLOCKED(v4_peers.lock),
+	.total		= 0,
+};
+
+static struct inet_peer_base v6_peers = {
+	.root		= peer_avl_empty_rcu,
+	.lock		= __SPIN_LOCK_UNLOCKED(v6_peers.lock),
+	.total		= 0,
+};
+
 #define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
 
-static volatile int peer_total;
 /* Exported for sysctl_net_ipv4.  */
-int inet_peer_threshold = 65536 + 128;	/* start to throw entries more
+int inet_peer_threshold __read_mostly = 65536 + 128;	/* start to throw entries more
 					 * aggressively at this stage */
-int inet_peer_minttl = 120 * HZ;	/* TTL under high load: 120 sec */
-int inet_peer_maxttl = 10 * 60 * HZ;	/* usual time to live: 10 min */
-
-static struct inet_peer *inet_peer_unused_head;
-/* Exported for inet_putpeer inline function.  */
-struct inet_peer **inet_peer_unused_tailp = &inet_peer_unused_head;
-DEFINE_SPINLOCK(inet_peer_unused_lock);
-#define PEER_MAX_CLEANUP_WORK 30
+int inet_peer_minttl __read_mostly = 120 * HZ;	/* TTL under high load: 120 sec */
+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 {
+	struct list_head	list;
+	spinlock_t		lock;
+} unused_peers = {
+	.list			= LIST_HEAD_INIT(unused_peers.list),
+	.lock			= __SPIN_LOCK_UNLOCKED(unused_peers.lock),
+};
 
 static void peer_check_expire(unsigned long dummy);
-static struct timer_list peer_periodic_timer =
-	TIMER_INITIALIZER(peer_check_expire, 0, 0);
+static DEFINE_TIMER(peer_periodic_timer, peer_check_expire, 0, 0);
 
-/* Exported for sysctl_net_ipv4.  */
-int inet_peer_gc_mintime = 10 * HZ,
-    inet_peer_gc_maxtime = 120 * HZ;
 
 /* Called from ip_output.c:ip_init  */
 void __init inet_initpeers(void)
@@ -126,11 +140,8 @@ void __init inet_initpeers(void)
 
 	peer_cachep = kmem_cache_create("inet_peer_cache",
 			sizeof(struct inet_peer),
-			0, SLAB_HWCACHE_ALIGN,
-			NULL, NULL);
-
-	if (!peer_cachep)
-		panic("cannot create inet_peer_cache");
+			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC,
+			NULL);
 
 	/* All the timers, started at system startup tend
 	   to synchronize. Perturb it a bit.
@@ -144,123 +155,194 @@ void __init inet_initpeers(void)
 /* Called with or without local BH being disabled. */
 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 */
+	if (!list_empty(&p->unused)) {
+		spin_lock_bh(&unused_peers.lock);
+		list_del_init(&p->unused);
+		spin_unlock_bh(&unused_peers.lock);
 	}
-	spin_unlock_bh(&inet_peer_unused_lock);
 }
 
-/* Called with local BH disabled and the pool lock held. */
-#define lookup(daddr) 						\
+static int addr_compare(const struct inetpeer_addr *a,
+			const struct inetpeer_addr *b)
+{
+	int i, n = (a->family == AF_INET ? 1 : 4);
+
+	for (i = 0; i < n; i++) {
+		if (a->a6[i] == b->a6[i])
+			continue;
+		if (a->a6[i] < b->a6[i])
+			return -1;
+		return 1;
+	}
+
+	return 0;
+}
+
+/*
+ * Called with local BH disabled and the pool lock held.
+ */
+#define lookup(_daddr, _stack, _base)				\
 ({								\
-	struct inet_peer *u, **v;				\
-	stackptr = stack;					\
-	*stackptr++ = &peer_root;				\
-	for (u = peer_root; u != peer_avl_empty; ) {		\
-		if (daddr == u->v4daddr)			\
+	struct inet_peer *u;					\
+	struct inet_peer __rcu **v;				\
+								\
+	stackptr = _stack;					\
+	*stackptr++ = &_base->root;				\
+	for (u = rcu_dereference_protected(_base->root,		\
+			lockdep_is_held(&_base->lock));		\
+	     u != peer_avl_empty; ) {				\
+		int cmp = addr_compare(_daddr, &u->daddr);	\
+		if (cmp == 0)					\
 			break;					\
-		if (daddr < u->v4daddr)				\
+		if (cmp == -1)					\
 			v = &u->avl_left;			\
 		else						\
 			v = &u->avl_right;			\
 		*stackptr++ = v;				\
-		u = *v;						\
+		u = rcu_dereference_protected(*v,		\
+			lockdep_is_held(&_base->lock));		\
 	}							\
 	u;							\
 })
 
-/* Called with local BH disabled and the pool write lock held. */
-#define lookup_rightempty(start)				\
+/*
+ * Called with rcu_read_lock_bh()
+ * Because we hold no lock against a writer, its quite possible we fall
+ * in an endless loop.
+ * But every pointer we follow is guaranteed to be valid thanks to RCU.
+ * We exit from this function if number of links exceeds PEER_MAXDEPTH
+ */
+static struct inet_peer *lookup_rcu_bh(const struct inetpeer_addr *daddr,
+				       struct inet_peer_base *base)
+{
+	struct inet_peer *u = rcu_dereference_bh(base->root);
+	int count = 0;
+
+	while (u != peer_avl_empty) {
+		int cmp = addr_compare(daddr, &u->daddr);
+		if (cmp == 0) {
+			/* Before taking a reference, check if this entry was
+			 * deleted, unlink_from_pool() sets refcnt=-1 to make
+			 * distinction between an unused entry (refcnt=0) and
+			 * a freed one.
+			 */
+			if (unlikely(!atomic_add_unless(&u->refcnt, 1, -1)))
+				u = NULL;
+			return u;
+		}
+		if (cmp == -1)
+			u = rcu_dereference_bh(u->avl_left);
+		else
+			u = rcu_dereference_bh(u->avl_right);
+		if (unlikely(++count == PEER_MAXDEPTH))
+			break;
+	}
+	return NULL;
+}
+
+/* Called with local BH disabled and the pool lock held. */
+#define lookup_rightempty(start, base)				\
 ({								\
-	struct inet_peer *u, **v;				\
+	struct inet_peer *u;					\
+	struct inet_peer __rcu **v;				\
 	*stackptr++ = &start->avl_left;				\
 	v = &start->avl_left;					\
-	for (u = *v; u->avl_right != peer_avl_empty; ) {	\
+	for (u = rcu_dereference_protected(*v,			\
+			lockdep_is_held(&base->lock));		\
+	     u->avl_right != peer_avl_empty_rcu; ) {		\
 		v = &u->avl_right;				\
 		*stackptr++ = v;				\
-		u = *v;						\
+		u = rcu_dereference_protected(*v,		\
+			lockdep_is_held(&base->lock));		\
 	}							\
 	u;							\
 })
 
-/* Called with local BH disabled and the pool write lock held.
+/* Called with local BH disabled and the pool lock held.
  * Variable names are the proof of operation correctness.
- * Look into mm/map_avl.c for more detail description of the ideas.  */
-static void peer_avl_rebalance(struct inet_peer **stack[],
-		struct inet_peer ***stackend)
+ * Look into mm/map_avl.c for more detail description of the ideas.
+ */
+static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
+			       struct inet_peer __rcu ***stackend,
+			       struct inet_peer_base *base)
 {
-	struct inet_peer **nodep, *node, *l, *r;
+	struct inet_peer __rcu **nodep;
+	struct inet_peer *node, *l, *r;
 	int lh, rh;
 
 	while (stackend > stack) {
 		nodep = *--stackend;
-		node = *nodep;
-		l = node->avl_left;
-		r = node->avl_right;
+		node = rcu_dereference_protected(*nodep,
+				lockdep_is_held(&base->lock));
+		l = rcu_dereference_protected(node->avl_left,
+				lockdep_is_held(&base->lock));
+		r = rcu_dereference_protected(node->avl_right,
+				lockdep_is_held(&base->lock));
 		lh = node_height(l);
 		rh = node_height(r);
 		if (lh > rh + 1) { /* l: RH+2 */
 			struct inet_peer *ll, *lr, *lrl, *lrr;
 			int lrh;
-			ll = l->avl_left;
-			lr = l->avl_right;
+			ll = rcu_dereference_protected(l->avl_left,
+				lockdep_is_held(&base->lock));
+			lr = rcu_dereference_protected(l->avl_right,
+				lockdep_is_held(&base->lock));
 			lrh = node_height(lr);
 			if (lrh <= node_height(ll)) {	/* ll: RH+1 */
-				node->avl_left = lr;	/* lr: RH or RH+1 */
-				node->avl_right = r;	/* r: RH */
+				RCU_INIT_POINTER(node->avl_left, lr);	/* lr: RH or RH+1 */
+				RCU_INIT_POINTER(node->avl_right, r);	/* r: RH */
 				node->avl_height = lrh + 1; /* RH+1 or RH+2 */
-				l->avl_left = ll;	/* ll: RH+1 */
-				l->avl_right = node;	/* node: RH+1 or RH+2 */
+				RCU_INIT_POINTER(l->avl_left, ll);       /* ll: RH+1 */
+				RCU_INIT_POINTER(l->avl_right, node);	/* node: RH+1 or RH+2 */
 				l->avl_height = node->avl_height + 1;
-				*nodep = l;
+				RCU_INIT_POINTER(*nodep, l);
 			} else { /* ll: RH, lr: RH+1 */
-				lrl = lr->avl_left;	/* lrl: RH or RH-1 */
-				lrr = lr->avl_right;	/* lrr: RH or RH-1 */
-				node->avl_left = lrr;	/* lrr: RH or RH-1 */
-				node->avl_right = r;	/* r: RH */
+				lrl = rcu_dereference_protected(lr->avl_left,
+					lockdep_is_held(&base->lock));	/* lrl: RH or RH-1 */
+				lrr = rcu_dereference_protected(lr->avl_right,
+					lockdep_is_held(&base->lock));	/* lrr: RH or RH-1 */
+				RCU_INIT_POINTER(node->avl_left, lrr);	/* lrr: RH or RH-1 */
+				RCU_INIT_POINTER(node->avl_right, r);	/* r: RH */
 				node->avl_height = rh + 1; /* node: RH+1 */
-				l->avl_left = ll;	/* ll: RH */
-				l->avl_right = lrl;	/* lrl: RH or RH-1 */
+				RCU_INIT_POINTER(l->avl_left, ll);	/* ll: RH */
+				RCU_INIT_POINTER(l->avl_right, lrl);	/* lrl: RH or RH-1 */
 				l->avl_height = rh + 1;	/* l: RH+1 */
-				lr->avl_left = l;	/* l: RH+1 */
-				lr->avl_right = node;	/* node: RH+1 */
+				RCU_INIT_POINTER(lr->avl_left, l);	/* l: RH+1 */
+				RCU_INIT_POINTER(lr->avl_right, node);	/* node: RH+1 */
 				lr->avl_height = rh + 2;
-				*nodep = lr;
+				RCU_INIT_POINTER(*nodep, lr);
 			}
 		} else if (rh > lh + 1) { /* r: LH+2 */
 			struct inet_peer *rr, *rl, *rlr, *rll;
 			int rlh;
-			rr = r->avl_right;
-			rl = r->avl_left;
+			rr = rcu_dereference_protected(r->avl_right,
+				lockdep_is_held(&base->lock));
+			rl = rcu_dereference_protected(r->avl_left,
+				lockdep_is_held(&base->lock));
 			rlh = node_height(rl);
 			if (rlh <= node_height(rr)) {	/* rr: LH+1 */
-				node->avl_right = rl;	/* rl: LH or LH+1 */
-				node->avl_left = l;	/* l: LH */
+				RCU_INIT_POINTER(node->avl_right, rl);	/* rl: LH or LH+1 */
+				RCU_INIT_POINTER(node->avl_left, l);	/* l: LH */
 				node->avl_height = rlh + 1; /* LH+1 or LH+2 */
-				r->avl_right = rr;	/* rr: LH+1 */
-				r->avl_left = node;	/* node: LH+1 or LH+2 */
+				RCU_INIT_POINTER(r->avl_right, rr);	/* rr: LH+1 */
+				RCU_INIT_POINTER(r->avl_left, node);	/* node: LH+1 or LH+2 */
 				r->avl_height = node->avl_height + 1;
-				*nodep = r;
+				RCU_INIT_POINTER(*nodep, r);
 			} else { /* rr: RH, rl: RH+1 */
-				rlr = rl->avl_right;	/* rlr: LH or LH-1 */
-				rll = rl->avl_left;	/* rll: LH or LH-1 */
-				node->avl_right = rll;	/* rll: LH or LH-1 */
-				node->avl_left = l;	/* l: LH */
+				rlr = rcu_dereference_protected(rl->avl_right,
+					lockdep_is_held(&base->lock));	/* rlr: LH or LH-1 */
+				rll = rcu_dereference_protected(rl->avl_left,
+					lockdep_is_held(&base->lock));	/* rll: LH or LH-1 */
+				RCU_INIT_POINTER(node->avl_right, rll);	/* rll: LH or LH-1 */
+				RCU_INIT_POINTER(node->avl_left, l);	/* l: LH */
 				node->avl_height = lh + 1; /* node: LH+1 */
-				r->avl_right = rr;	/* rr: LH */
-				r->avl_left = rlr;	/* rlr: LH or LH-1 */
+				RCU_INIT_POINTER(r->avl_right, rr);	/* rr: LH */
+				RCU_INIT_POINTER(r->avl_left, rlr);	/* rlr: LH or LH-1 */
 				r->avl_height = lh + 1;	/* r: LH+1 */
-				rl->avl_right = r;	/* r: LH+1 */
-				rl->avl_left = node;	/* node: LH+1 */
+				RCU_INIT_POINTER(rl->avl_right, r);	/* r: LH+1 */
+				RCU_INIT_POINTER(rl->avl_left, node);	/* node: LH+1 */
 				rl->avl_height = lh + 2;
-				*nodep = rl;
+				RCU_INIT_POINTER(*nodep, rl);
 			}
 		} else {
 			node->avl_height = (lh > rh ? lh : rh) + 1;
@@ -268,99 +350,117 @@ static void peer_avl_rebalance(struct inet_peer **stack[],
 	}
 }
 
-/* Called with local BH disabled and the pool write lock held. */
-#define link_to_pool(n)						\
+/* Called with local BH disabled and the pool lock held. */
+#define link_to_pool(n, base)					\
 do {								\
 	n->avl_height = 1;					\
-	n->avl_left = peer_avl_empty;				\
-	n->avl_right = peer_avl_empty;				\
-	**--stackptr = n;					\
-	peer_avl_rebalance(stack, stackptr);			\
-} while(0)
+	n->avl_left = peer_avl_empty_rcu;			\
+	n->avl_right = peer_avl_empty_rcu;			\
+	/* lockless readers can catch us now */			\
+	rcu_assign_pointer(**--stackptr, n);			\
+	peer_avl_rebalance(stack, stackptr, base);		\
+} while (0)
+
+static void inetpeer_free_rcu(struct rcu_head *head)
+{
+	kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
+}
 
 /* May be called with local BH enabled. */
-static void unlink_from_pool(struct inet_peer *p)
+static void unlink_from_pool(struct inet_peer *p, struct inet_peer_base *base,
+			     struct inet_peer __rcu **stack[PEER_MAXDEPTH])
 {
 	int do_free;
 
 	do_free = 0;
 
-	write_lock_bh(&peer_pool_lock);
+	spin_lock_bh(&base->lock);
 	/* Check the reference counter.  It was artificially incremented by 1
-	 * in cleanup() function to prevent sudden disappearing.  If the
-	 * reference count is still 1 then the node is referenced only as `p'
-	 * here and from the pool.  So under the exclusive pool lock it's safe
-	 * to remove the node and free it later. */
-	if (atomic_read(&p->refcnt) == 1) {
-		struct inet_peer **stack[PEER_MAXDEPTH];
-		struct inet_peer ***stackptr, ***delp;
-		if (lookup(p->v4daddr) != p)
+	 * in cleanup() function to prevent sudden disappearing.  If we can
+	 * atomically (because of lockless readers) take this last reference,
+	 * it's safe to remove the node and free it later.
+	 * We use refcnt=-1 to alert lockless readers this entry is deleted.
+	 */
+	if (atomic_cmpxchg(&p->refcnt, 1, -1) == 1) {
+		struct inet_peer __rcu ***stackptr, ***delp;
+		if (lookup(&p->daddr, stack, base) != p)
 			BUG();
 		delp = stackptr - 1; /* *delp[0] == p */
-		if (p->avl_left == peer_avl_empty) {
+		if (p->avl_left == peer_avl_empty_rcu) {
 			*delp[0] = p->avl_right;
 			--stackptr;
 		} else {
 			/* look for a node to insert instead of p */
 			struct inet_peer *t;
-			t = lookup_rightempty(p);
-			if (*stackptr[-1] != t)
-				BUG();
+			t = lookup_rightempty(p, base);
+			BUG_ON(rcu_dereference_protected(*stackptr[-1],
+					lockdep_is_held(&base->lock)) != t);
 			**--stackptr = t->avl_left;
-			/* t is removed, t->v4daddr > x->v4daddr for any
+			/* t is removed, t->daddr > x->daddr for any
 			 * x in p->avl_left subtree.
 			 * Put t in the old place of p. */
-			*delp[0] = t;
+			RCU_INIT_POINTER(*delp[0], t);
 			t->avl_left = p->avl_left;
 			t->avl_right = p->avl_right;
 			t->avl_height = p->avl_height;
-			if (delp[1] != &p->avl_left)
-				BUG();
+			BUG_ON(delp[1] != &p->avl_left);
 			delp[1] = &t->avl_left; /* was &p->avl_left */
 		}
-		peer_avl_rebalance(stack, stackptr);
-		peer_total--;
+		peer_avl_rebalance(stack, stackptr, base);
+		base->total--;
 		do_free = 1;
 	}
-	write_unlock_bh(&peer_pool_lock);
+	spin_unlock_bh(&base->lock);
 
 	if (do_free)
-		kmem_cache_free(peer_cachep, p);
+		call_rcu_bh(&p->rcu, inetpeer_free_rcu);
 	else
 		/* The node is used again.  Decrease the reference counter
 		 * back.  The loop "cleanup -> unlink_from_unused
 		 *   -> unlink_from_pool -> putpeer -> link_to_unused
 		 *   -> cleanup (for the same node)"
 		 * doesn't really exist because the entry will have a
-		 * recent deletion time and will not be cleaned again soon. */
+		 * recent deletion time and will not be cleaned again soon.
+		 */
 		inet_putpeer(p);
 }
 
+static struct inet_peer_base *family_to_base(int family)
+{
+	return (family == AF_INET ? &v4_peers : &v6_peers);
+}
+
+static struct inet_peer_base *peer_to_base(struct inet_peer *p)
+{
+	return family_to_base(p->daddr.family);
+}
+
 /* May be called with local BH enabled. */
-static int cleanup_once(unsigned long ttl)
+static int cleanup_once(unsigned long ttl, struct inet_peer __rcu **stack[PEER_MAXDEPTH])
 {
-	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) {
-		if (time_after(p->dtime + ttl, jiffies)) {
+	spin_lock_bh(&unused_peers.lock);
+	if (!list_empty(&unused_peers.list)) {
+		__u32 delta;
+
+		p = list_first_entry(&unused_peers.list, struct inet_peer, unused);
+		delta = (__u32)jiffies - p->dtime;
+
+		if (delta < ttl) {
 			/* Do not prune fresh entries. */
-			spin_unlock_bh(&inet_peer_unused_lock);
+			spin_unlock_bh(&unused_peers.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);
 	}
-	spin_unlock_bh(&inet_peer_unused_lock);
+	spin_unlock_bh(&unused_peers.lock);
 
 	if (p == NULL)
 		/* It means that the total number of USED entries has
@@ -368,94 +468,116 @@ static int cleanup_once(unsigned long ttl)
 		 * happen because of entry limits in route cache. */
 		return -1;
 
-	unlink_from_pool(p);
+	unlink_from_pool(p, peer_to_base(p), stack);
 	return 0;
 }
 
 /* Called with or without local BH being disabled. */
-struct inet_peer *inet_getpeer(__u32 daddr, int create)
+struct inet_peer *inet_getpeer(struct inetpeer_addr *daddr, int create)
 {
-	struct inet_peer *p, *n;
-	struct inet_peer **stack[PEER_MAXDEPTH], ***stackptr;
+	struct inet_peer __rcu **stack[PEER_MAXDEPTH], ***stackptr;
+	struct inet_peer_base *base = family_to_base(daddr->family);
+	struct inet_peer *p;
 
-	/* Look up for the address quickly. */
-	read_lock_bh(&peer_pool_lock);
-	p = lookup(daddr);
-	if (p != peer_avl_empty)
-		atomic_inc(&p->refcnt);
-	read_unlock_bh(&peer_pool_lock);
+	/* Look up for the address quickly, lockless.
+	 * Because of a concurrent writer, we might not find an existing entry.
+	 */
+	rcu_read_lock_bh();
+	p = lookup_rcu_bh(daddr, base);
+	rcu_read_unlock_bh();
+
+	if (p) {
+		/* The existing node has been found.
+		 * Remove the entry from unused list if it was there.
+		 */
+		unlink_from_unused(p);
+		return p;
+	}
 
+	/* retry an exact lookup, taking the lock before.
+	 * At least, nodes should be hot in our cache.
+	 */
+	spin_lock_bh(&base->lock);
+	p = lookup(daddr, stack, base);
 	if (p != peer_avl_empty) {
-		/* The existing node has been found. */
+		atomic_inc(&p->refcnt);
+		spin_unlock_bh(&base->lock);
 		/* Remove the entry from unused list if it was there. */
 		unlink_from_unused(p);
 		return p;
 	}
+	p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;
+	if (p) {
+		p->daddr = *daddr;
+		atomic_set(&p->refcnt, 1);
+		atomic_set(&p->rid, 0);
+		atomic_set(&p->ip_id_count, secure_ip_id(daddr->a4));
+		p->tcp_ts_stamp = 0;
+		INIT_LIST_HEAD(&p->unused);
+
+
+		/* Link the node. */
+		link_to_pool(p, base);
+		base->total++;
+	}
+	spin_unlock_bh(&base->lock);
 
-	if (!create)
-		return NULL;
-
-	/* Allocate the space outside the locked region. */
-	n = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);
-	if (n == NULL)
-		return NULL;
-	n->v4daddr = daddr;
-	atomic_set(&n->refcnt, 1);
-	n->ip_id_count = secure_ip_id(daddr);
-	n->tcp_ts_stamp = 0;
-
-	write_lock_bh(&peer_pool_lock);
-	/* Check if an entry has suddenly appeared. */
-	p = lookup(daddr);
-	if (p != peer_avl_empty)
-		goto out_free;
-
-	/* Link the node. */
-	link_to_pool(n);
-	n->unused_prevp = NULL; /* not on the list */
-	peer_total++;
-	write_unlock_bh(&peer_pool_lock);
-
-	if (peer_total >= inet_peer_threshold)
+	if (base->total >= inet_peer_threshold)
 		/* Remove one less-recently-used entry. */
-		cleanup_once(0);
-
-	return n;
-
-out_free:
-	/* The appropriate node is already in the pool. */
-	atomic_inc(&p->refcnt);
-	write_unlock_bh(&peer_pool_lock);
-	/* Remove the entry from unused list if it was there. */
-	unlink_from_unused(p);
-	/* Free preallocated the preallocated node. */
-	kmem_cache_free(peer_cachep, n);
+		cleanup_once(0, stack);
+
 	return p;
 }
 
+static int compute_total(void)
+{
+	return v4_peers.total + v6_peers.total;
+}
+EXPORT_SYMBOL_GPL(inet_getpeer);
+
 /* Called with local BH disabled. */
 static void peer_check_expire(unsigned long dummy)
 {
-	int i;
-	int ttl;
+	unsigned long now = jiffies;
+	int ttl, total;
+	struct inet_peer __rcu **stack[PEER_MAXDEPTH];
 
-	if (peer_total >= inet_peer_threshold)
+	total = compute_total();
+	if (total >= inet_peer_threshold)
 		ttl = inet_peer_minttl;
 	else
 		ttl = inet_peer_maxttl
 				- (inet_peer_maxttl - inet_peer_minttl) / HZ *
-					peer_total / inet_peer_threshold * HZ;
-	for (i = 0; i < PEER_MAX_CLEANUP_WORK && !cleanup_once(ttl); i++);
+					total / inet_peer_threshold * HZ;
+	while (!cleanup_once(ttl, stack)) {
+		if (jiffies != now)
+			break;
+	}
 
 	/* Trigger the timer after inet_peer_gc_mintime .. inet_peer_gc_maxtime
 	 * interval depending on the total number of entries (more entries,
 	 * less interval). */
-	if (peer_total >= inet_peer_threshold)
+	total = compute_total();
+	if (total >= inet_peer_threshold)
 		peer_periodic_timer.expires = jiffies + inet_peer_gc_mintime;
 	else
 		peer_periodic_timer.expires = jiffies
 			+ inet_peer_gc_maxtime
 			- (inet_peer_gc_maxtime - inet_peer_gc_mintime) / HZ *
-				peer_total / inet_peer_threshold * HZ;
+				total / inet_peer_threshold * HZ;
 	add_timer(&peer_periodic_timer);
 }
+
+void inet_putpeer(struct inet_peer *p)
+{
+	local_bh_disable();
+
+	if (atomic_dec_and_lock(&p->refcnt, &unused_peers.lock)) {
+		list_add_tail(&p->unused, &unused_peers.list);
+		p->dtime = (__u32)jiffies;
+		spin_unlock(&unused_peers.lock);
+	}
+
+	local_bh_enable();
+}
+EXPORT_SYMBOL_GPL(inet_putpeer);