This patch backports several critical bug fixes related to
locking and data consistency in nf_conncount code.

This backport is based on the following upstream net-next upstream commits.
a007232 ("netfilter: nf_conncount: fix argument order to find_next_bit")
c80f10b ("netfilter: nf_conncount: speculative garbage collection on empty 
lists")
2f971a8 ("netfilter: nf_conncount: move all list iterations under spinlock")
df4a902 ("netfilter: nf_conncount: merge lookup and add functions")
e8cfb37 ("netfilter: nf_conncount: restart search when nodes have been erased")
f7fcc98 ("netfilter: nf_conncount: split gc in two phases")
4cd273b ("netfilter: nf_conncount: don't skip eviction when age is negative")
c78e781 ("netfilter: nf_conncount: replace CONNCOUNT_LOCK_SLOTS with 
CONNCOUNT_SLOTS")
d4e7df1 ("netfilter: nf_conncount: use rb_link_node_rcu() instead of 
rb_link_node()")
53ca0f2 ("netfilter: nf_conncount: remove wrong condition check routine")
3c5cdb1 ("netfilter: nf_conncount: fix unexpected permanent node of list.")
31568ec ("netfilter: nf_conncount: fix list_del corruption in conn_free")
fd3e71a ("netfilter: nf_conncount: use spin_lock_bh instead of spin_lock")

This patch adds additional compat code so that it can build on
all supported kernel versions.

In addition, this patch helps OVS datapath to always choose bug-fixed
nf_conncount code. If kernel already has these fixes, then kernel's
nf_conncount is being used. Otherwise, OVS falls back to use compat
nf_conncount functions.

Travis tests are at
https://travis-ci.org/yifsun/ovs-travis/builds/569056850
On latest RHEL kernel, 'make check-kmod' runs good.

VMware-BZ: #2396471

Signed-off-by: Yifeng Sun <pkusunyif...@gmail.com>
---
v1->v2: Add fixes to support old kernel versions, as suggested by YiHung.
v2->v3: Backport more upstream patches. Thanks YiHung for reviewing.
 acinclude.m4                                       |   6 +-
 datapath/linux/Modules.mk                          |   3 +-
 datapath/linux/compat/include/linux/rbtree.h       |  19 ++
 .../include/net/netfilter/nf_conntrack_count.h     |   7 -
 datapath/linux/compat/nf_conncount.c               | 290 ++++++++++-----------
 5 files changed, 161 insertions(+), 164 deletions(-)
 create mode 100644 datapath/linux/compat/include/linux/rbtree.h

diff --git a/acinclude.m4 b/acinclude.m4
index 116ffcf9096d..f0e38898b17a 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -713,7 +713,9 @@ AC_DEFUN([OVS_CHECK_LINUX_COMPAT], [
   OVS_GREP_IFELSE([$KSRC/include/net/netfilter/nf_nat.h], [nf_nat_range2])
   OVS_GREP_IFELSE([$KSRC/include/net/netfilter/nf_conntrack_seqadj.h], 
[nf_ct_seq_adjust])
   OVS_GREP_IFELSE([$KSRC/include/net/netfilter/nf_conntrack_count.h], 
[nf_conncount_gc_list],
-                  [OVS_DEFINE([HAVE_UPSTREAM_NF_CONNCOUNT])])
+                  
[OVS_GREP_IFELSE([$KSRC/include/net/netfilter/nf_conntrack_count.h],
+                                   [int nf_conncount_add],
+                                   [], 
[OVS_DEFINE([HAVE_UPSTREAM_NF_CONNCOUNT])])])
 
   OVS_GREP_IFELSE([$KSRC/include/linux/random.h], [prandom_u32])
   OVS_GREP_IFELSE([$KSRC/include/linux/random.h], [prandom_u32_max])
@@ -1012,6 +1014,8 @@ AC_DEFUN([OVS_CHECK_LINUX_COMPAT], [
                   [OVS_DEFINE([HAVE_GRE_CALC_HLEN])])
   OVS_GREP_IFELSE([$KSRC/include/net/gre.h], [ip_gre_calc_hlen],
                   [OVS_DEFINE([HAVE_IP_GRE_CALC_HLEN])])
+  OVS_GREP_IFELSE([$KSRC/include/linux/rbtree.h], [rb_link_node_rcu],
+                  [OVS_DEFINE([HAVE_RBTREE_RB_LINK_NODE_RCU])])
 
   if cmp -s datapath/linux/kcompat.h.new \
             datapath/linux/kcompat.h >/dev/null 2>&1; then
diff --git a/datapath/linux/Modules.mk b/datapath/linux/Modules.mk
index cbb29f1c69d0..69d7faeac414 100644
--- a/datapath/linux/Modules.mk
+++ b/datapath/linux/Modules.mk
@@ -116,5 +116,6 @@ openvswitch_headers += \
        linux/compat/include/uapi/linux/netfilter.h \
        linux/compat/include/linux/mm.h \
        linux/compat/include/linux/netfilter.h \
-       linux/compat/include/linux/overflow.h
+       linux/compat/include/linux/overflow.h \
+       linux/compat/include/linux/rbtree.h
 EXTRA_DIST += linux/compat/build-aux/export-check-whitelist
diff --git a/datapath/linux/compat/include/linux/rbtree.h 
b/datapath/linux/compat/include/linux/rbtree.h
new file mode 100644
index 000000000000..dbf20ff0e0b8
--- /dev/null
+++ b/datapath/linux/compat/include/linux/rbtree.h
@@ -0,0 +1,19 @@
+#ifndef __LINUX_RBTREE_WRAPPER_H
+#define __LINUX_RBTREE_WRAPPER_H 1
+
+#include_next <linux/rbtree.h>
+
+#ifndef HAVE_RBTREE_RB_LINK_NODE_RCU
+#include <linux/rcupdate.h>
+
+static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node 
*parent,
+                                   struct rb_node **rb_link)
+{
+       node->__rb_parent_color = (unsigned long)parent;
+       node->rb_left = node->rb_right = NULL;
+
+       rcu_assign_pointer(*rb_link, node);
+}
+#endif
+
+#endif /* __LINUX_RBTREE_WRAPPER_H */
diff --git a/datapath/linux/compat/include/net/netfilter/nf_conntrack_count.h 
b/datapath/linux/compat/include/net/netfilter/nf_conntrack_count.h
index 614017309efe..2143136aa617 100644
--- a/datapath/linux/compat/include/net/netfilter/nf_conntrack_count.h
+++ b/datapath/linux/compat/include/net/netfilter/nf_conntrack_count.h
@@ -21,17 +21,10 @@ static inline void rpl_nf_conncount_modexit(void)
 #define CONFIG_NETFILTER_CONNCOUNT 1
 struct nf_conncount_data;
 
-enum nf_conncount_list_add {
-       NF_CONNCOUNT_ADDED,     /* list add was ok */
-       NF_CONNCOUNT_ERR,       /* -ENOMEM, must drop skb */
-       NF_CONNCOUNT_SKIP,      /* list is already reclaimed by gc */
-};
-
 struct nf_conncount_list {
        spinlock_t list_lock;
        struct list_head head;  /* connections with the same filtering key */
        unsigned int count;     /* length of list */
-       bool dead;
 };
 
 struct nf_conncount_data
diff --git a/datapath/linux/compat/nf_conncount.c 
b/datapath/linux/compat/nf_conncount.c
index eeae440f872d..97bdfb933b95 100644
--- a/datapath/linux/compat/nf_conncount.c
+++ b/datapath/linux/compat/nf_conncount.c
@@ -38,12 +38,6 @@
 
 #define CONNCOUNT_SLOTS                256U
 
-#ifdef CONFIG_LOCKDEP
-#define CONNCOUNT_LOCK_SLOTS   8U
-#else
-#define CONNCOUNT_LOCK_SLOTS   256U
-#endif
-
 #define CONNCOUNT_GC_MAX_NODES 8
 #define MAX_KEYLEN             5
 
@@ -54,7 +48,6 @@ struct nf_conncount_tuple {
        struct nf_conntrack_zone        zone;
        int                             cpu;
        u32                             jiffies32;
-       struct rcu_head                 rcu_head;
 };
 
 struct nf_conncount_rb {
@@ -64,7 +57,7 @@ struct nf_conncount_rb {
        struct rcu_head rcu_head;
 };
 
-static spinlock_t nf_conncount_locks[CONNCOUNT_LOCK_SLOTS] 
__cacheline_aligned_in_smp;
+static spinlock_t nf_conncount_locks[CONNCOUNT_SLOTS] 
__cacheline_aligned_in_smp;
 
 struct nf_conncount_data {
        unsigned int keylen;
@@ -93,74 +86,25 @@ static int key_diff(const u32 *a, const u32 *b, unsigned 
int klen)
        return memcmp(a, b, klen * sizeof(u32));
 }
 
-static enum nf_conncount_list_add
-nf_conncount_add(struct nf_conncount_list *list,
-                const struct nf_conntrack_tuple *tuple,
-                const struct nf_conntrack_zone *zone)
-{
-       struct nf_conncount_tuple *conn;
-
-       if (WARN_ON_ONCE(list->count > INT_MAX))
-               return NF_CONNCOUNT_ERR;
-
-       conn = kmem_cache_alloc(conncount_conn_cachep, GFP_ATOMIC);
-       if (conn == NULL)
-               return NF_CONNCOUNT_ERR;
-
-       conn->tuple = *tuple;
-       conn->zone = *zone;
-       conn->cpu = raw_smp_processor_id();
-       conn->jiffies32 = (u32)jiffies;
-       spin_lock(&list->list_lock);
-       if (list->dead == true) {
-               kmem_cache_free(conncount_conn_cachep, conn);
-               spin_unlock(&list->list_lock);
-               return NF_CONNCOUNT_SKIP;
-       }
-       list_add_tail(&conn->node, &list->head);
-       list->count++;
-       spin_unlock(&list->list_lock);
-       return NF_CONNCOUNT_ADDED;
-}
-
-static void __conn_free(struct rcu_head *h)
-{
-       struct nf_conncount_tuple *conn;
-
-       conn = container_of(h, struct nf_conncount_tuple, rcu_head);
-       kmem_cache_free(conncount_conn_cachep, conn);
-}
-
-static bool conn_free(struct nf_conncount_list *list,
+static void conn_free(struct nf_conncount_list *list,
                      struct nf_conncount_tuple *conn)
 {
-       bool free_entry = false;
-
-       spin_lock(&list->list_lock);
-
-       if (list->count == 0) {
-               spin_unlock(&list->list_lock);
-               return free_entry;
-       }
+       lockdep_assert_held(&list->list_lock);
 
        list->count--;
-       list_del_rcu(&conn->node);
-       if (list->count == 0)
-               free_entry = true;
+       list_del(&conn->node);
 
-       spin_unlock(&list->list_lock);
-       call_rcu(&conn->rcu_head, __conn_free);
-       return free_entry;
+       kmem_cache_free(conncount_conn_cachep, conn);
 }
 
 static const struct nf_conntrack_tuple_hash *
 find_or_evict(struct net *net, struct nf_conncount_list *list,
-             struct nf_conncount_tuple *conn, bool *free_entry)
+             struct nf_conncount_tuple *conn)
 {
        const struct nf_conntrack_tuple_hash *found;
        unsigned long a, b;
        int cpu = raw_smp_processor_id();
-       __s32 age;
+       u32 age;
 
        found = nf_conntrack_find_get(net, &conn->zone, &conn->tuple);
        if (found)
@@ -175,52 +119,45 @@ find_or_evict(struct net *net, struct nf_conncount_list 
*list,
         */
        age = a - b;
        if (conn->cpu == cpu || age >= 2) {
-               *free_entry = conn_free(list, conn);
+               conn_free(list, conn);
                return ERR_PTR(-ENOENT);
        }
 
        return ERR_PTR(-EAGAIN);
 }
 
-static void nf_conncount_lookup(struct net *net,
-                        struct nf_conncount_list *list,
-                        const struct nf_conntrack_tuple *tuple,
-                        const struct nf_conntrack_zone *zone,
-                        bool *addit)
+static int __nf_conncount_add(struct net *net,
+                             struct nf_conncount_list *list,
+                             const struct nf_conntrack_tuple *tuple,
+                             const struct nf_conntrack_zone *zone)
 {
        const struct nf_conntrack_tuple_hash *found;
        struct nf_conncount_tuple *conn, *conn_n;
        struct nf_conn *found_ct;
        unsigned int collect = 0;
-       bool free_entry = false;
-
-       /* best effort only */
-       *addit = tuple ? true : false;
 
        /* check the saved connections */
        list_for_each_entry_safe(conn, conn_n, &list->head, node) {
                if (collect > CONNCOUNT_GC_MAX_NODES)
                        break;
 
-               found = find_or_evict(net, list, conn, &free_entry);
+               found = find_or_evict(net, list, conn);
                if (IS_ERR(found)) {
                        /* Not found, but might be about to be confirmed */
                        if (PTR_ERR(found) == -EAGAIN) {
-                               if (!tuple)
-                                       continue;
-
                                if (nf_ct_tuple_equal(&conn->tuple, tuple) &&
                                    nf_ct_zone_id(&conn->zone, conn->zone.dir) 
==
                                    nf_ct_zone_id(zone, zone->dir))
-                                       *addit = false;
-                       } else if (PTR_ERR(found) == -ENOENT)
+                                       return 0; /* already exists */
+                       } else {
                                collect++;
+                       }
                        continue;
                }
 
                found_ct = nf_ct_tuplehash_to_ctrack(found);
 
-               if (tuple && nf_ct_tuple_equal(&conn->tuple, tuple) &&
+               if (nf_ct_tuple_equal(&conn->tuple, tuple) &&
                    nf_ct_zone_equal(found_ct, zone, zone->dir)) {
                        /*
                         * We should not see tuples twice unless someone hooks
@@ -228,7 +165,8 @@ static void nf_conncount_lookup(struct net *net,
                         *
                         * Attempt to avoid a re-add in this case.
                         */
-                       *addit = false;
+                       nf_ct_put(found_ct);
+                       return 0;
                } else if (already_closed(found_ct)) {
                        /*
                         * we do not care about connections which are
@@ -242,34 +180,64 @@ static void nf_conncount_lookup(struct net *net,
 
                nf_ct_put(found_ct);
        }
+
+       if (WARN_ON_ONCE(list->count > INT_MAX))
+               return -EOVERFLOW;
+
+       conn = kmem_cache_alloc(conncount_conn_cachep, GFP_ATOMIC);
+       if (conn == NULL)
+               return -ENOMEM;
+
+       conn->tuple = *tuple;
+       conn->zone = *zone;
+       conn->cpu = raw_smp_processor_id();
+       conn->jiffies32 = (u32)jiffies;
+       list_add_tail(&conn->node, &list->head);
+       list->count++;
+       return 0;
+}
+
+int nf_conncount_add(struct net *net,
+                    struct nf_conncount_list *list,
+                    const struct nf_conntrack_tuple *tuple,
+                    const struct nf_conntrack_zone *zone)
+{
+       int ret;
+
+       /* check the saved connections */
+       spin_lock_bh(&list->list_lock);
+       ret = __nf_conncount_add(net, list, tuple, zone);
+       spin_unlock_bh(&list->list_lock);
+
+       return ret;
 }
 
 static void nf_conncount_list_init(struct nf_conncount_list *list)
 {
        spin_lock_init(&list->list_lock);
        INIT_LIST_HEAD(&list->head);
-       list->count = 1;
-       list->dead = false;
+       list->count = 0;
 }
 
-/* Return true if the list is empty */
+/* Return true if the list is empty. Must be called with BH disabled. */
 static bool nf_conncount_gc_list(struct net *net,
-                         struct nf_conncount_list *list)
+                                struct nf_conncount_list *list)
 {
        const struct nf_conntrack_tuple_hash *found;
        struct nf_conncount_tuple *conn, *conn_n;
        struct nf_conn *found_ct;
        unsigned int collected = 0;
-       bool free_entry = false;
+       bool ret = false;
+
+       /* don't bother if other cpu is already doing GC */
+       if (!spin_trylock(&list->list_lock))
+               return false;
 
        list_for_each_entry_safe(conn, conn_n, &list->head, node) {
-               found = find_or_evict(net, list, conn, &free_entry);
+               found = find_or_evict(net, list, conn);
                if (IS_ERR(found)) {
-                       if (PTR_ERR(found) == -ENOENT)  {
-                               if (free_entry)
-                                       return true;
+                       if (PTR_ERR(found) == -ENOENT)
                                collected++;
-                       }
                        continue;
                }
 
@@ -280,17 +248,21 @@ static bool nf_conncount_gc_list(struct net *net,
                         * closed already -> ditch it
                         */
                        nf_ct_put(found_ct);
-                       if (conn_free(list, conn))
-                               return true;
+                       conn_free(list, conn);
                        collected++;
                        continue;
                }
 
                nf_ct_put(found_ct);
                if (collected > CONNCOUNT_GC_MAX_NODES)
-                       return false;
+                       break;
        }
-       return false;
+
+       if (!list->count)
+               ret = true;
+       spin_unlock(&list->list_lock);
+
+       return ret;
 }
 
 static void __tree_nodes_free(struct rcu_head *h)
@@ -301,6 +273,7 @@ static void __tree_nodes_free(struct rcu_head *h)
        kmem_cache_free(conncount_rb_cachep, rbconn);
 }
 
+/* caller must hold tree nf_conncount_locks[] lock */
 static void tree_nodes_free(struct rb_root *root,
                            struct nf_conncount_rb *gc_nodes[],
                            unsigned int gc_count)
@@ -310,8 +283,7 @@ static void tree_nodes_free(struct rb_root *root,
        while (gc_count) {
                rbconn = gc_nodes[--gc_count];
                spin_lock(&rbconn->list.list_lock);
-               if (rbconn->list.count == 0 && rbconn->list.dead == false) {
-                       rbconn->list.dead = true;
+               if (!rbconn->list.count) {
                        rb_erase(&rbconn->node, root);
                        call_rcu(&rbconn->rcu_head, __tree_nodes_free);
                }
@@ -331,20 +303,19 @@ insert_tree(struct net *net,
            struct rb_root *root,
            unsigned int hash,
            const u32 *key,
-           u8 keylen,
            const struct nf_conntrack_tuple *tuple,
            const struct nf_conntrack_zone *zone)
 {
-       enum nf_conncount_list_add ret;
        struct nf_conncount_rb *gc_nodes[CONNCOUNT_GC_MAX_NODES];
        struct rb_node **rbnode, *parent;
        struct nf_conncount_rb *rbconn;
        struct nf_conncount_tuple *conn;
        unsigned int count = 0, gc_count = 0;
-       bool node_found = false;
-
-       spin_lock_bh(&nf_conncount_locks[hash % CONNCOUNT_LOCK_SLOTS]);
+       u8 keylen = data->keylen;
+       bool do_gc = true;
 
+       spin_lock_bh(&nf_conncount_locks[hash]);
+restart:
        parent = NULL;
        rbnode = &(root->rb_node);
        while (*rbnode) {
@@ -358,45 +329,32 @@ insert_tree(struct net *net,
                } else if (diff > 0) {
                        rbnode = &((*rbnode)->rb_right);
                } else {
-                       /* unlikely: other cpu added node already */
-                       node_found = true;
-                       ret = nf_conncount_add(&rbconn->list, tuple, zone);
-                       if (ret == NF_CONNCOUNT_ERR) {
+                       int ret;
+
+                       ret = nf_conncount_add(net, &rbconn->list, tuple, zone);
+                       if (ret)
                                count = 0; /* hotdrop */
-                       } else if (ret == NF_CONNCOUNT_ADDED) {
+                       else
                                count = rbconn->list.count;
-                       } else {
-                               /* NF_CONNCOUNT_SKIP, rbconn is already
-                                * reclaimed by gc, insert a new tree node
-                                */
-                               node_found = false;
-                       }
-                       break;
+                       tree_nodes_free(root, gc_nodes, gc_count);
+                       goto out_unlock;
                }
 
                if (gc_count >= ARRAY_SIZE(gc_nodes))
                        continue;
 
-               if (nf_conncount_gc_list(net, &rbconn->list))
+               if (do_gc && nf_conncount_gc_list(net, &rbconn->list))
                        gc_nodes[gc_count++] = rbconn;
        }
 
        if (gc_count) {
                tree_nodes_free(root, gc_nodes, gc_count);
-               /* tree_node_free before new allocation permits
-                * allocator to re-use newly free'd object.
-                *
-                * This is a rare event; in most cases we will find
-                * existing node to re-use. (or gc_count is 0).
-                */
-
-               if (gc_count >= ARRAY_SIZE(gc_nodes))
-                       schedule_gc_worker(data, hash);
+               schedule_gc_worker(data, hash);
+               gc_count = 0;
+               do_gc = false;
+               goto restart;
        }
 
-       if (node_found)
-               goto out_unlock;
-
        /* expected case: match, insert new node */
        rbconn = kmem_cache_alloc(conncount_rb_cachep, GFP_ATOMIC);
        if (rbconn == NULL)
@@ -415,11 +373,12 @@ insert_tree(struct net *net,
        nf_conncount_list_init(&rbconn->list);
        list_add(&conn->node, &rbconn->list.head);
        count = 1;
+       rbconn->list.count = count;
 
-       rb_link_node(&rbconn->node, parent, rbnode);
+       rb_link_node_rcu(&rbconn->node, parent, rbnode);
        rb_insert_color(&rbconn->node, root);
 out_unlock:
-       spin_unlock_bh(&nf_conncount_locks[hash % CONNCOUNT_LOCK_SLOTS]);
+       spin_unlock_bh(&nf_conncount_locks[hash]);
        return count;
 }
 
@@ -430,7 +389,6 @@ count_tree(struct net *net,
           const struct nf_conntrack_tuple *tuple,
           const struct nf_conntrack_zone *zone)
 {
-       enum nf_conncount_list_add ret;
        struct rb_root *root;
        struct rb_node *parent;
        struct nf_conncount_rb *rbconn;
@@ -443,7 +401,6 @@ count_tree(struct net *net,
        parent = rcu_dereference_raw(root->rb_node);
        while (parent) {
                int diff;
-               bool addit;
 
                rbconn = rb_entry(parent, struct nf_conncount_rb, node);
 
@@ -453,31 +410,36 @@ count_tree(struct net *net,
                } else if (diff > 0) {
                        parent = rcu_dereference_raw(parent->rb_right);
                } else {
-                       /* same source network -> be counted! */
-                       nf_conncount_lookup(net, &rbconn->list, tuple, zone,
-                                           &addit);
+                       int ret;
 
-                       if (!addit)
+                       if (!tuple) {
+                               nf_conncount_gc_list(net, &rbconn->list);
                                return rbconn->list.count;
+                       }
 
-                       ret = nf_conncount_add(&rbconn->list, tuple, zone);
-                       if (ret == NF_CONNCOUNT_ERR) {
-                               return 0; /* hotdrop */
-                       } else if (ret == NF_CONNCOUNT_ADDED) {
-                               return rbconn->list.count;
-                       } else {
-                               /* NF_CONNCOUNT_SKIP, rbconn is already
-                                * reclaimed by gc, insert a new tree node
-                                */
+                       spin_lock_bh(&rbconn->list.list_lock);
+                       /* Node might be about to be free'd.
+                        * We need to defer to insert_tree() in this case.
+                        */
+                       if (rbconn->list.count == 0) {
+                               spin_unlock_bh(&rbconn->list.list_lock);
                                break;
                        }
+
+                       /* same source network -> be counted! */
+                       ret = __nf_conncount_add(net, &rbconn->list, tuple, 
zone);
+                       spin_unlock_bh(&rbconn->list.list_lock);
+                       if (ret)
+                               return 0; /* hotdrop */
+                       else
+                               return rbconn->list.count;
                }
        }
 
        if (!tuple)
                return 0;
 
-       return insert_tree(net, data, root, hash, key, keylen, tuple, zone);
+       return insert_tree(net, data, root, hash, key, tuple, zone);
 }
 
 static void tree_gc_worker(struct work_struct *work)
@@ -488,27 +450,48 @@ static void tree_gc_worker(struct work_struct *work)
        struct rb_node *node;
        unsigned int tree, next_tree, gc_count = 0;
 
-       tree = data->gc_tree % CONNCOUNT_LOCK_SLOTS;
+       tree = data->gc_tree % CONNCOUNT_SLOTS;
        root = &data->root[tree];
 
+       local_bh_disable();
        rcu_read_lock();
        for (node = rb_first(root); node != NULL; node = rb_next(node)) {
                rbconn = rb_entry(node, struct nf_conncount_rb, node);
                if (nf_conncount_gc_list(data->net, &rbconn->list))
-                       gc_nodes[gc_count++] = rbconn;
+                       gc_count++;
        }
        rcu_read_unlock();
+       local_bh_enable();
+
+       cond_resched();
 
        spin_lock_bh(&nf_conncount_locks[tree]);
+       if (gc_count < ARRAY_SIZE(gc_nodes))
+               goto next; /* do not bother */
 
-       if (gc_count) {
-               tree_nodes_free(root, gc_nodes, gc_count);
+       gc_count = 0;
+       node = rb_first(root);
+       while (node != NULL) {
+               rbconn = rb_entry(node, struct nf_conncount_rb, node);
+               node = rb_next(node);
+
+               if (rbconn->list.count > 0)
+                       continue;
+
+               gc_nodes[gc_count++] = rbconn;
+               if (gc_count >= ARRAY_SIZE(gc_nodes)) {
+                       tree_nodes_free(root, gc_nodes, gc_count);
+                       gc_count = 0;
+               }
        }
 
+       tree_nodes_free(root, gc_nodes, gc_count);
+next:
+
        clear_bit(tree, data->pending_trees);
 
        next_tree = (tree + 1) % CONNCOUNT_SLOTS;
-       next_tree = find_next_bit(data->pending_trees, next_tree, 
CONNCOUNT_SLOTS);
+       next_tree = find_next_bit(data->pending_trees, CONNCOUNT_SLOTS, 
next_tree);
 
        if (next_tree < CONNCOUNT_SLOTS) {
                data->gc_tree = next_tree;
@@ -533,7 +516,7 @@ unsigned int rpl_nf_conncount_count(struct net *net,
 EXPORT_SYMBOL_GPL(rpl_nf_conncount_count);
 
 struct nf_conncount_data *rpl_nf_conncount_init(struct net *net, unsigned int 
family,
-                                           unsigned int keylen)
+                                               unsigned int keylen)
 {
        struct nf_conncount_data *data;
        int ret, i;
@@ -609,10 +592,7 @@ int rpl_nf_conncount_modinit(void)
 {
        int i;
 
-       BUILD_BUG_ON(CONNCOUNT_LOCK_SLOTS > CONNCOUNT_SLOTS);
-       BUILD_BUG_ON((CONNCOUNT_SLOTS % CONNCOUNT_LOCK_SLOTS) != 0);
-
-       for (i = 0; i < CONNCOUNT_LOCK_SLOTS; ++i)
+       for (i = 0; i < CONNCOUNT_SLOTS; ++i)
                spin_lock_init(&nf_conncount_locks[i]);
 
        conncount_conn_cachep = kmem_cache_create("nf_conncount_tuple",
-- 
2.7.4

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