From: Julian Anastasov <ja@xxxxxx>
Convert __ip_vs_conntbl_lock_array as follows:
- readers that do not modify conn lists will use RCU lock
- updaters that modify lists will use spinlock_t
Now for conn lookups we will use RCU read-side
critical section. Without using __ip_vs_conn_get such
places have access to connection fields and can
dereference some pointers like pe and pe_data plus
the ability to update timer expiration. If full access
is required we contend for reference.
We add barrier in __ip_vs_conn_put, so that
other CPUs see the refcnt operation after other writes.
With the introduction of ip_vs_conn_unlink()
we try to reorganize ip_vs_conn_expire(), so that
unhashing of connections that should stay more time is
avoided, even if it is for very short time.
Signed-off-by: Julian Anastasov <ja@xxxxxx>
Signed-off by: Hans Schillstrom <hans@xxxxxxxxxxxxxxx>
Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
---
include/net/ip_vs.h | 12 ++
net/netfilter/ipvs/ip_vs_conn.c | 230 +++++++++++++++++++++------------------
2 files changed, 134 insertions(+), 108 deletions(-)
diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index f46db3f..72ca406 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -620,6 +620,8 @@ struct ip_vs_conn {
const struct ip_vs_pe *pe;
char *pe_data;
__u8 pe_data_len;
+
+ struct rcu_head rcu_head;
};
/*
@@ -1173,9 +1175,19 @@ struct ip_vs_conn * ip_vs_conn_out_get_proto(int af, const struct sk_buff *skb,
const struct ip_vs_iphdr *iph,
int inverse);
+/* Get reference to gain full access to conn.
+ * By default, RCU read-side critical sections have access only to
+ * conn fields and its PE data, see ip_vs_conn_rcu_free() for reference.
+ */
+static inline bool __ip_vs_conn_get(struct ip_vs_conn *cp)
+{
+ return atomic_inc_not_zero(&cp->refcnt);
+}
+
/* put back the conn without restarting its timer */
static inline void __ip_vs_conn_put(struct ip_vs_conn *cp)
{
+ smp_mb__before_atomic_dec();
atomic_dec(&cp->refcnt);
}
extern void ip_vs_conn_put(struct ip_vs_conn *cp);
diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c
index 704e514..b0cd2be 100644
--- a/net/netfilter/ipvs/ip_vs_conn.c
+++ b/net/netfilter/ipvs/ip_vs_conn.c
@@ -79,51 +79,21 @@ static unsigned int ip_vs_conn_rnd __read_mostly;
struct ip_vs_aligned_lock
{
- rwlock_t l;
+ spinlock_t l;
} __attribute__((__aligned__(SMP_CACHE_BYTES)));
/* lock array for conn table */
static struct ip_vs_aligned_lock
__ip_vs_conntbl_lock_array[CT_LOCKARRAY_SIZE] __cacheline_aligned;
-static inline void ct_read_lock(unsigned int key)
-{
- read_lock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
-}
-
-static inline void ct_read_unlock(unsigned int key)
-{
- read_unlock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
-}
-
static inline void ct_write_lock(unsigned int key)
{
- write_lock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
+ spin_lock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}
static inline void ct_write_unlock(unsigned int key)
{
- write_unlock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
-}
-
-static inline void ct_read_lock_bh(unsigned int key)
-{
- read_lock_bh(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
-}
-
-static inline void ct_read_unlock_bh(unsigned int key)
-{
- read_unlock_bh(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
-}
-
-static inline void ct_write_lock_bh(unsigned int key)
-{
- write_lock_bh(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
-}
-
-static inline void ct_write_unlock_bh(unsigned int key)
-{
- write_unlock_bh(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
+ spin_unlock(&__ip_vs_conntbl_lock_array[key&CT_LOCKARRAY_MASK].l);
}
@@ -201,9 +171,9 @@ static inline int ip_vs_conn_hash(struct ip_vs_conn *cp)
spin_lock(&cp->lock);
if (!(cp->flags & IP_VS_CONN_F_HASHED)) {
- hlist_add_head(&cp->c_list, &ip_vs_conn_tab[hash]);
cp->flags |= IP_VS_CONN_F_HASHED;
atomic_inc(&cp->refcnt);
+ hlist_add_head_rcu(&cp->c_list, &ip_vs_conn_tab[hash]);
ret = 1;
} else {
pr_err("%s(): request for already hashed, called from %pF\n",
@@ -220,7 +190,7 @@ static inline int ip_vs_conn_hash(struct ip_vs_conn *cp)
/*
* UNhashes ip_vs_conn from ip_vs_conn_tab.
- * returns bool success.
+ * returns bool success. Caller should hold conn reference.
*/
static inline int ip_vs_conn_unhash(struct ip_vs_conn *cp)
{
@@ -234,7 +204,7 @@ static inline int ip_vs_conn_unhash(struct ip_vs_conn *cp)
spin_lock(&cp->lock);
if (cp->flags & IP_VS_CONN_F_HASHED) {
- hlist_del(&cp->c_list);
+ hlist_del_rcu(&cp->c_list);
cp->flags &= ~IP_VS_CONN_F_HASHED;
atomic_dec(&cp->refcnt);
ret = 1;
@@ -247,6 +217,36 @@ static inline int ip_vs_conn_unhash(struct ip_vs_conn *cp)
return ret;
}
+/* Try to unlink ip_vs_conn from ip_vs_conn_tab.
+ * returns bool success.
+ */
+static inline bool ip_vs_conn_unlink(struct ip_vs_conn *cp)
+{
+ unsigned int hash;
+ bool ret;
+
+ hash = ip_vs_conn_hashkey_conn(cp);
+
+ ct_write_lock(hash);
+ spin_lock(&cp->lock);
+
+ if (cp->flags & IP_VS_CONN_F_HASHED) {
+ ret = false;
+ /* Decrease refcnt and unlink conn only if we are last user */
+ if (atomic_cmpxchg(&cp->refcnt, 1, 0) == 1) {
+ hlist_del_rcu(&cp->c_list);
+ cp->flags &= ~IP_VS_CONN_F_HASHED;
+ ret = true;
+ }
+ } else
+ ret = atomic_read(&cp->refcnt) ? false : true;
+
+ spin_unlock(&cp->lock);
+ ct_write_unlock(hash);
+
+ return ret;
+}
+
/*
* Gets ip_vs_conn associated with supplied parameters in the ip_vs_conn_tab.
@@ -262,9 +262,9 @@ __ip_vs_conn_in_get(const struct ip_vs_conn_param *p)
hash = ip_vs_conn_hashkey_param(p, false);
- ct_read_lock(hash);
+ rcu_read_lock();
- hlist_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
+ hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
if (cp->af == p->af &&
p->cport == cp->cport && p->vport == cp->vport &&
ip_vs_addr_equal(p->af, p->caddr, &cp->caddr) &&
@@ -272,14 +272,15 @@ __ip_vs_conn_in_get(const struct ip_vs_conn_param *p)
((!p->cport) ^ (!(cp->flags & IP_VS_CONN_F_NO_CPORT))) &&
p->protocol == cp->protocol &&
ip_vs_conn_net_eq(cp, p->net)) {
+ if (!__ip_vs_conn_get(cp))
+ continue;
/* HIT */
- atomic_inc(&cp->refcnt);
- ct_read_unlock(hash);
+ rcu_read_unlock();
return cp;
}
}
- ct_read_unlock(hash);
+ rcu_read_unlock();
return NULL;
}
@@ -346,14 +347,16 @@ struct ip_vs_conn *ip_vs_ct_in_get(const struct ip_vs_conn_param *p)
hash = ip_vs_conn_hashkey_param(p, false);
- ct_read_lock(hash);
+ rcu_read_lock();
- hlist_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
+ hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
if (!ip_vs_conn_net_eq(cp, p->net))
continue;
if (p->pe_data && p->pe->ct_match) {
- if (p->pe == cp->pe && p->pe->ct_match(p, cp))
- goto out;
+ if (p->pe == cp->pe && p->pe->ct_match(p, cp)) {
+ if (__ip_vs_conn_get(cp))
+ goto out;
+ }
continue;
}
@@ -365,15 +368,15 @@ struct ip_vs_conn *ip_vs_ct_in_get(const struct ip_vs_conn_param *p)
p->af, p->vaddr, &cp->vaddr) &&
p->cport == cp->cport && p->vport == cp->vport &&
cp->flags & IP_VS_CONN_F_TEMPLATE &&
- p->protocol == cp->protocol)
- goto out;
+ p->protocol == cp->protocol) {
+ if (__ip_vs_conn_get(cp))
+ goto out;
+ }
}
cp = NULL;
out:
- if (cp)
- atomic_inc(&cp->refcnt);
- ct_read_unlock(hash);
+ rcu_read_unlock();
IP_VS_DBG_BUF(9, "template lookup/in %s %s:%d->%s:%d %s\n",
ip_vs_proto_name(p->protocol),
@@ -398,23 +401,24 @@ struct ip_vs_conn *ip_vs_conn_out_get(const struct ip_vs_conn_param *p)
*/
hash = ip_vs_conn_hashkey_param(p, true);
- ct_read_lock(hash);
+ rcu_read_lock();
- hlist_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
+ hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
if (cp->af == p->af &&
p->vport == cp->cport && p->cport == cp->dport &&
ip_vs_addr_equal(p->af, p->vaddr, &cp->caddr) &&
ip_vs_addr_equal(p->af, p->caddr, &cp->daddr) &&
p->protocol == cp->protocol &&
ip_vs_conn_net_eq(cp, p->net)) {
+ if (!__ip_vs_conn_get(cp))
+ continue;
/* HIT */
- atomic_inc(&cp->refcnt);
ret = cp;
break;
}
}
- ct_read_unlock(hash);
+ rcu_read_unlock();
IP_VS_DBG_BUF(9, "lookup/out %s %s:%d->%s:%d %s\n",
ip_vs_proto_name(p->protocol),
@@ -757,41 +761,36 @@ int ip_vs_check_template(struct ip_vs_conn *ct)
* Simply decrease the refcnt of the template,
* don't restart its timer.
*/
- atomic_dec(&ct->refcnt);
+ __ip_vs_conn_put(ct);
return 0;
}
return 1;
}
+static void ip_vs_conn_rcu_free(struct rcu_head *head)
+{
+ struct ip_vs_conn *cp = container_of(head, struct ip_vs_conn,
+ rcu_head);
+
+ ip_vs_pe_put(cp->pe);
+ kfree(cp->pe_data);
+ kmem_cache_free(ip_vs_conn_cachep, cp);
+}
+
static void ip_vs_conn_expire(unsigned long data)
{
struct ip_vs_conn *cp = (struct ip_vs_conn *)data;
struct net *net = ip_vs_conn_net(cp);
struct netns_ipvs *ipvs = net_ipvs(net);
- cp->timeout = 60*HZ;
-
- /*
- * hey, I'm using it
- */
- atomic_inc(&cp->refcnt);
-
/*
* do I control anybody?
*/
if (atomic_read(&cp->n_control))
goto expire_later;
- /*
- * unhash it if it is hashed in the conn table
- */
- if (!ip_vs_conn_unhash(cp) && !(cp->flags & IP_VS_CONN_F_ONE_PACKET))
- goto expire_later;
-
- /*
- * refcnt==1 implies I'm the only one referrer
- */
- if (likely(atomic_read(&cp->refcnt) == 1)) {
+ /* Unlink conn if not referenced anymore */
+ if (likely(ip_vs_conn_unlink(cp))) {
/* delete the timer if it is activated by other users */
del_timer(&cp->timer);
@@ -810,38 +809,41 @@ static void ip_vs_conn_expire(unsigned long data)
ip_vs_conn_drop_conntrack(cp);
}
- ip_vs_pe_put(cp->pe);
- kfree(cp->pe_data);
if (unlikely(cp->app != NULL))
ip_vs_unbind_app(cp);
ip_vs_unbind_dest(cp);
if (cp->flags & IP_VS_CONN_F_NO_CPORT)
atomic_dec(&ip_vs_conn_no_cport_cnt);
+ call_rcu(&cp->rcu_head, ip_vs_conn_rcu_free);
atomic_dec(&ipvs->conn_count);
-
- kmem_cache_free(ip_vs_conn_cachep, cp);
return;
}
- /* hash it back to the table */
- ip_vs_conn_hash(cp);
-
expire_later:
- IP_VS_DBG(7, "delayed: conn->refcnt-1=%d conn->n_control=%d\n",
- atomic_read(&cp->refcnt)-1,
+ IP_VS_DBG(7, "delayed: conn->refcnt=%d conn->n_control=%d\n",
+ atomic_read(&cp->refcnt),
atomic_read(&cp->n_control));
+ atomic_inc(&cp->refcnt);
+ cp->timeout = 60*HZ;
+
if (ipvs->sync_state & IP_VS_STATE_MASTER)
ip_vs_sync_conn(net, cp, sysctl_sync_threshold(ipvs));
ip_vs_conn_put(cp);
}
-
+/* Modify timer, so that it expires as soon as possible.
+ * Can be called without reference only if under RCU lock.
+ */
void ip_vs_conn_expire_now(struct ip_vs_conn *cp)
{
- if (del_timer(&cp->timer))
- mod_timer(&cp->timer, jiffies);
+ /* Using mod_timer_pending will ensure the timer is not
+ * modified after the final del_timer in ip_vs_conn_expire.
+ */
+ if (timer_pending(&cp->timer) &&
+ time_after(cp->timer.expires, jiffies))
+ mod_timer_pending(&cp->timer, jiffies);
}
@@ -952,14 +954,17 @@ static void *ip_vs_conn_array(struct seq_file *seq, loff_t pos)
struct ip_vs_iter_state *iter = seq->private;
for (idx = 0; idx < ip_vs_conn_tab_size; idx++) {
- ct_read_lock_bh(idx);
- hlist_for_each_entry(cp, &ip_vs_conn_tab[idx], c_list) {
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[idx], c_list) {
+ /* __ip_vs_conn_get() is not needed by
+ * ip_vs_conn_seq_show and ip_vs_conn_sync_seq_show
+ */
if (pos-- == 0) {
iter->l = &ip_vs_conn_tab[idx];
return cp;
}
}
- ct_read_unlock_bh(idx);
+ rcu_read_unlock();
}
return NULL;
@@ -977,6 +982,7 @@ static void *ip_vs_conn_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
struct ip_vs_conn *cp = v;
struct ip_vs_iter_state *iter = seq->private;
+ struct hlist_node *e;
struct hlist_head *l = iter->l;
int idx;
@@ -985,19 +991,19 @@ static void *ip_vs_conn_seq_next(struct seq_file *seq, void *v, loff_t *pos)
return ip_vs_conn_array(seq, 0);
/* more on same hash chain? */
- if (cp->c_list.next)
- return hlist_entry(cp->c_list.next, struct ip_vs_conn, c_list);
+ e = rcu_dereference(hlist_next_rcu(&cp->c_list));
+ if (e)
+ return hlist_entry(e, struct ip_vs_conn, c_list);
+ rcu_read_unlock();
idx = l - ip_vs_conn_tab;
- ct_read_unlock_bh(idx);
-
while (++idx < ip_vs_conn_tab_size) {
- ct_read_lock_bh(idx);
- hlist_for_each_entry(cp, &ip_vs_conn_tab[idx], c_list) {
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[idx], c_list) {
iter->l = &ip_vs_conn_tab[idx];
return cp;
}
- ct_read_unlock_bh(idx);
+ rcu_read_unlock();
}
iter->l = NULL;
return NULL;
@@ -1009,7 +1015,7 @@ static void ip_vs_conn_seq_stop(struct seq_file *seq, void *v)
struct hlist_head *l = iter->l;
if (l)
- ct_read_unlock_bh(l - ip_vs_conn_tab);
+ rcu_read_unlock();
}
static int ip_vs_conn_seq_show(struct seq_file *seq, void *v)
@@ -1188,7 +1194,7 @@ static inline int todrop_entry(struct ip_vs_conn *cp)
void ip_vs_random_dropentry(struct net *net)
{
int idx;
- struct ip_vs_conn *cp;
+ struct ip_vs_conn *cp, *cp_c;
/*
* Randomly scan 1/32 of the whole table every second
@@ -1199,9 +1205,9 @@ void ip_vs_random_dropentry(struct net *net)
/*
* Lock is actually needed in this loop.
*/
- ct_write_lock_bh(hash);
+ rcu_read_lock();
- hlist_for_each_entry(cp, &ip_vs_conn_tab[hash], c_list) {
+ hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
if (cp->flags & IP_VS_CONN_F_TEMPLATE)
/* connection template */
continue;
@@ -1228,12 +1234,15 @@ void ip_vs_random_dropentry(struct net *net)
IP_VS_DBG(4, "del connection\n");
ip_vs_conn_expire_now(cp);
- if (cp->control) {
+ cp_c = cp->control;
+ /* cp->control is valid only with reference to cp */
+ if (cp_c && __ip_vs_conn_get(cp)) {
IP_VS_DBG(4, "del conn template\n");
- ip_vs_conn_expire_now(cp->control);
+ ip_vs_conn_expire_now(cp_c);
+ __ip_vs_conn_put(cp);
}
}
- ct_write_unlock_bh(hash);
+ rcu_read_unlock();
}
}
@@ -1244,7 +1253,7 @@ void ip_vs_random_dropentry(struct net *net)
static void ip_vs_conn_flush(struct net *net)
{
int idx;
- struct ip_vs_conn *cp;
+ struct ip_vs_conn *cp, *cp_c;
struct netns_ipvs *ipvs = net_ipvs(net);
flush_again:
@@ -1252,19 +1261,22 @@ flush_again:
/*
* Lock is actually needed in this loop.
*/
- ct_write_lock_bh(idx);
+ rcu_read_lock();
- hlist_for_each_entry(cp, &ip_vs_conn_tab[idx], c_list) {
+ hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[idx], c_list) {
if (!ip_vs_conn_net_eq(cp, net))
continue;
IP_VS_DBG(4, "del connection\n");
ip_vs_conn_expire_now(cp);
- if (cp->control) {
+ cp_c = cp->control;
+ /* cp->control is valid only with reference to cp */
+ if (cp_c && __ip_vs_conn_get(cp)) {
IP_VS_DBG(4, "del conn template\n");
- ip_vs_conn_expire_now(cp->control);
+ ip_vs_conn_expire_now(cp_c);
+ __ip_vs_conn_put(cp);
}
}
- ct_write_unlock_bh(idx);
+ rcu_read_unlock();
}
/* the counter may be not NULL, because maybe some conn entries
@@ -1331,7 +1343,7 @@ int __init ip_vs_conn_init(void)
INIT_HLIST_HEAD(&ip_vs_conn_tab[idx]);
for (idx = 0; idx < CT_LOCKARRAY_SIZE; idx++) {
- rwlock_init(&__ip_vs_conntbl_lock_array[idx].l);
+ spin_lock_init(&__ip_vs_conntbl_lock_array[idx].l);
}
/* calculate the random value for connection hash */
@@ -1342,6 +1354,8 @@ int __init ip_vs_conn_init(void)
void ip_vs_conn_cleanup(void)
{
+ /* Wait all ip_vs_conn_rcu_free() callbacks to complete */
+ rcu_barrier();
/* Release the empty cache */
kmem_cache_destroy(ip_vs_conn_cachep);
vfree(ip_vs_conn_tab);
--
1.7.10.4
--
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