From: Julian Anastasov Date: Thu, 21 Mar 2013 09:58:10 +0000 (+0200) Subject: ipvs: convert connection locking X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=088339a57d6042;p=linux-beck.git ipvs: convert connection locking 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 Signed-off by: Hans Schillstrom Signed-off-by: Simon Horman --- diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h index b06aa6c939fa..5700b07b5186 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; }; /* @@ -1185,9 +1187,19 @@ 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 704e514e02ab..b0cd2be01d75 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);