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Date: Sun, 23 Nov 2008 07:59:32 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Eric Dumazet <dada1@...mosbay.com>
Cc: David Miller <davem@...emloft.net>,
Corey Minyard <minyard@....org>,
Stephen Hemminger <shemminger@...tta.com>,
benny+usenet@...rsen.dk,
Linux Netdev List <netdev@...r.kernel.org>,
Christoph Lameter <cl@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Evgeniy Polyakov <zbr@...emap.net>,
Christian Bell <christian@...i.com>
Subject: Re: [PATCH] net: Convert TCP/DCCP listening hash tables to use RCU
On Sun, Nov 23, 2008 at 10:33:28AM +0100, Eric Dumazet wrote:
> Hi David
>
> Please find patch to convert TCP/DCCP listening hash tables
> to RCU.
>
> A followup patch will cleanup all sk_node fields and macros
> that are not used anymore.
>
> Thanks
>
> [PATCH] net: Convert TCP/DCCP listening hash tables to use RCU
>
> This is the last step to be able to perform full RCU lookups
> in __inet_lookup() : After established/timewait tables, we
> add RCU lookups to listening hash table.
>
> The only trick here is that a socket of a given type (TCP ipv4,
> TCP ipv6, ...) can now flight between two different tables
> (established and listening) during a RCU grace period, so we
> must use different 'nulls' end-of-chain values for two tables.
>
> We define a large value :
>
> #define LISTENING_NULLS_BASE (1U << 29)
I do like this use of the full set up upper bits! However, wouldn't it
be a good idea to use a larger base value for 64-bit systems, perhaps
using CONFIG_64BIT to choose? 500M entries might not seem like that
many in a few years time...
Thanx, Paul
> So that slots in listening table are guaranteed to have different
> end-of-chain values than slots in established table. A reader can
> still detect it finished its lookup in the right chain.
>
> Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
> ---
> include/net/inet_hashtables.h | 9 +
> net/ipv4/inet_diag.c | 4
> net/ipv4/inet_hashtables.c | 148 ++++++++++++++++----------------
> net/ipv4/tcp_ipv4.c | 8 -
> net/ipv6/inet6_hashtables.c | 94 ++++++++++++--------
> 5 files changed, 147 insertions(+), 116 deletions(-)
> diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
> index ec7ee2e..df90118 100644
> --- a/include/net/inet_hashtables.h
> +++ b/include/net/inet_hashtables.h
> @@ -99,9 +99,16 @@ struct inet_bind_hashbucket {
> struct hlist_head chain;
> };
>
> +/*
> + * Sockets can be hashed in established or listening table
> + * We must use different 'nulls' end-of-chain value for listening
> + * hash table, or we might find a socket that was closed and
> + * reallocated/inserted into established hash table
> + */
> +#define LISTENING_NULLS_BASE (1U << 29)
> struct inet_listen_hashbucket {
> spinlock_t lock;
> - struct hlist_head head;
> + struct hlist_nulls_head head;
> };
>
> /* This is for listening sockets, thus all sockets which possess wildcards. */
> diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
> index 998a78f..588a779 100644
> --- a/net/ipv4/inet_diag.c
> +++ b/net/ipv4/inet_diag.c
> @@ -720,13 +720,13 @@ static int inet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
>
> for (i = s_i; i < INET_LHTABLE_SIZE; i++) {
> struct sock *sk;
> - struct hlist_node *node;
> + struct hlist_nulls_node *node;
> struct inet_listen_hashbucket *ilb;
>
> num = 0;
> ilb = &hashinfo->listening_hash[i];
> spin_lock_bh(&ilb->lock);
> - sk_for_each(sk, node, &ilb->head) {
> + sk_nulls_for_each(sk, node, &ilb->head) {
> struct inet_sock *inet = inet_sk(sk);
>
> if (num < s_num) {
> diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
> index 4c273a9..11fcb87 100644
> --- a/net/ipv4/inet_hashtables.c
> +++ b/net/ipv4/inet_hashtables.c
> @@ -110,78 +110,79 @@ void __inet_inherit_port(struct sock *sk, struct sock *child)
>
> EXPORT_SYMBOL_GPL(__inet_inherit_port);
>
> +static inline int compute_score(struct sock *sk, struct net *net,
> + const unsigned short hnum, const __be32 daddr,
> + const int dif)
> +{
> + int score = -1;
> + struct inet_sock *inet = inet_sk(sk);
> +
> + if (net_eq(sock_net(sk), net) && inet->num == hnum &&
> + !ipv6_only_sock(sk)) {
> + __be32 rcv_saddr = inet->rcv_saddr;
> + score = sk->sk_family == PF_INET ? 1 : 0;
> + if (rcv_saddr) {
> + if (rcv_saddr != daddr)
> + return -1;
> + score += 2;
> + }
> + if (sk->sk_bound_dev_if) {
> + if (sk->sk_bound_dev_if != dif)
> + return -1;
> + score += 2;
> + }
> + }
> + return score;
> +}
> +
> /*
> * Don't inline this cruft. Here are some nice properties to exploit here. The
> * BSD API does not allow a listening sock to specify the remote port nor the
> * remote address for the connection. So always assume those are both
> * wildcarded during the search since they can never be otherwise.
> */
> -static struct sock *inet_lookup_listener_slow(struct net *net,
> - const struct hlist_head *head,
> - const __be32 daddr,
> - const unsigned short hnum,
> - const int dif)
> -{
> - struct sock *result = NULL, *sk;
> - const struct hlist_node *node;
> - int hiscore = -1;
> -
> - sk_for_each(sk, node, head) {
> - const struct inet_sock *inet = inet_sk(sk);
> -
> - if (net_eq(sock_net(sk), net) && inet->num == hnum &&
> - !ipv6_only_sock(sk)) {
> - const __be32 rcv_saddr = inet->rcv_saddr;
> - int score = sk->sk_family == PF_INET ? 1 : 0;
> -
> - if (rcv_saddr) {
> - if (rcv_saddr != daddr)
> - continue;
> - score += 2;
> - }
> - if (sk->sk_bound_dev_if) {
> - if (sk->sk_bound_dev_if != dif)
> - continue;
> - score += 2;
> - }
> - if (score == 5)
> - return sk;
> - if (score > hiscore) {
> - hiscore = score;
> - result = sk;
> - }
> - }
> - }
> - return result;
> -}
>
> -/* Optimize the common listener case. */
> +
> struct sock *__inet_lookup_listener(struct net *net,
> struct inet_hashinfo *hashinfo,
> const __be32 daddr, const unsigned short hnum,
> const int dif)
> {
> - struct sock *sk = NULL;
> - struct inet_listen_hashbucket *ilb;
> + struct sock *sk, *result;
> + struct hlist_nulls_node *node;
> + unsigned int hash = inet_lhashfn(net, hnum);
> + struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
> + int score, hiscore;
>
> - ilb = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
> - spin_lock(&ilb->lock);
> - if (!hlist_empty(&ilb->head)) {
> - const struct inet_sock *inet = inet_sk((sk = __sk_head(&ilb->head)));
> -
> - if (inet->num == hnum && !sk->sk_node.next &&
> - (!inet->rcv_saddr || inet->rcv_saddr == daddr) &&
> - (sk->sk_family == PF_INET || !ipv6_only_sock(sk)) &&
> - !sk->sk_bound_dev_if && net_eq(sock_net(sk), net))
> - goto sherry_cache;
> - sk = inet_lookup_listener_slow(net, &ilb->head, daddr, hnum, dif);
> + rcu_read_lock();
> +begin:
> + result = NULL;
> + hiscore = -1;
> + sk_nulls_for_each_rcu(sk, node, &ilb->head) {
> + score = compute_score(sk, net, hnum, daddr, dif);
> + if (score > hiscore) {
> + result = sk;
> + hiscore = score;
> + }
> }
> - if (sk) {
> -sherry_cache:
> - sock_hold(sk);
> + /*
> + * if the nulls value we got at the end of this lookup is
> + * not the expected one, we must restart lookup.
> + * We probably met an item that was moved to another chain.
> + */
> + if (get_nulls_value(node) != hash + LISTENING_NULLS_BASE)
> + goto begin;
> + if (result) {
> + if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
> + result = NULL;
> + else if (unlikely(compute_score(result, net, hnum, daddr,
> + dif) < hiscore)) {
> + sock_put(result);
> + goto begin;
> + }
> }
> - spin_unlock(&ilb->lock);
> - return sk;
> + rcu_read_unlock();
> + return result;
> }
> EXPORT_SYMBOL_GPL(__inet_lookup_listener);
>
> @@ -370,7 +371,7 @@ static void __inet_hash(struct sock *sk)
> ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
>
> spin_lock(&ilb->lock);
> - __sk_add_node(sk, &ilb->head);
> + __sk_nulls_add_node_rcu(sk, &ilb->head);
> sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
> spin_unlock(&ilb->lock);
> }
> @@ -388,26 +389,22 @@ EXPORT_SYMBOL_GPL(inet_hash);
> void inet_unhash(struct sock *sk)
> {
> struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
> + spinlock_t *lock;
> + int done;
>
> if (sk_unhashed(sk))
> return;
>
> - if (sk->sk_state == TCP_LISTEN) {
> - struct inet_listen_hashbucket *ilb;
> + if (sk->sk_state == TCP_LISTEN)
> + lock = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)].lock;
> + else
> + lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
>
> - ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
> - spin_lock_bh(&ilb->lock);
> - if (__sk_del_node_init(sk))
> - sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
> - spin_unlock_bh(&ilb->lock);
> - } else {
> - spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
> -
> - spin_lock_bh(lock);
> - if (__sk_nulls_del_node_init_rcu(sk))
> - sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
> - spin_unlock_bh(lock);
> - }
> + spin_lock_bh(lock);
> + done =__sk_nulls_del_node_init_rcu(sk);
> + spin_unlock_bh(lock);
> + if (done)
> + sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
> }
> EXPORT_SYMBOL_GPL(inet_unhash);
>
> @@ -526,8 +523,11 @@ void inet_hashinfo_init(struct inet_hashinfo *h)
> {
> int i;
>
> - for (i = 0; i < INET_LHTABLE_SIZE; i++)
> + for (i = 0; i < INET_LHTABLE_SIZE; i++) {
> spin_lock_init(&h->listening_hash[i].lock);
> + INIT_HLIST_NULLS_HEAD(&h->listening_hash[i].head,
> + i + LISTENING_NULLS_BASE);
> + }
> }
>
> EXPORT_SYMBOL_GPL(inet_hashinfo_init);
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index a81caa1..cab2458 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -1868,7 +1868,7 @@ static inline struct inet_timewait_sock *tw_next(struct inet_timewait_sock *tw)
> static void *listening_get_next(struct seq_file *seq, void *cur)
> {
> struct inet_connection_sock *icsk;
> - struct hlist_node *node;
> + struct hlist_nulls_node *node;
> struct sock *sk = cur;
> struct inet_listen_hashbucket *ilb;
> struct tcp_iter_state *st = seq->private;
> @@ -1878,7 +1878,7 @@ static void *listening_get_next(struct seq_file *seq, void *cur)
> st->bucket = 0;
> ilb = &tcp_hashinfo.listening_hash[0];
> spin_lock_bh(&ilb->lock);
> - sk = sk_head(&ilb->head);
> + sk = sk_nulls_head(&ilb->head);
> goto get_sk;
> }
> ilb = &tcp_hashinfo.listening_hash[st->bucket];
> @@ -1914,7 +1914,7 @@ get_req:
> sk = sk_next(sk);
> }
> get_sk:
> - sk_for_each_from(sk, node) {
> + sk_nulls_for_each_from(sk, node) {
> if (sk->sk_family == st->family && net_eq(sock_net(sk), net)) {
> cur = sk;
> goto out;
> @@ -1935,7 +1935,7 @@ start_req:
> if (++st->bucket < INET_LHTABLE_SIZE) {
> ilb = &tcp_hashinfo.listening_hash[st->bucket];
> spin_lock_bh(&ilb->lock);
> - sk = sk_head(&ilb->head);
> + sk = sk_nulls_head(&ilb->head);
> goto get_sk;
> }
> cur = NULL;
> diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
> index e0fd681..8fe267f 100644
> --- a/net/ipv6/inet6_hashtables.c
> +++ b/net/ipv6/inet6_hashtables.c
> @@ -33,7 +33,7 @@ void __inet6_hash(struct sock *sk)
>
> ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
> spin_lock(&ilb->lock);
> - __sk_add_node(sk, &ilb->head);
> + __sk_nulls_add_node_rcu(sk, &ilb->head);
> spin_unlock(&ilb->lock);
> } else {
> unsigned int hash;
> @@ -118,47 +118,71 @@ out:
> }
> EXPORT_SYMBOL(__inet6_lookup_established);
>
> +static int inline compute_score(struct sock *sk, struct net *net,
> + const unsigned short hnum,
> + const struct in6_addr *daddr,
> + const int dif)
> +{
> + int score = -1;
> +
> + if (net_eq(sock_net(sk), net) && inet_sk(sk)->num == hnum &&
> + sk->sk_family == PF_INET6) {
> + const struct ipv6_pinfo *np = inet6_sk(sk);
> +
> + score = 1;
> + if (!ipv6_addr_any(&np->rcv_saddr)) {
> + if (!ipv6_addr_equal(&np->rcv_saddr, daddr))
> + return -1;
> + score++;
> + }
> + if (sk->sk_bound_dev_if) {
> + if (sk->sk_bound_dev_if != dif)
> + return -1;
> + score++;
> + }
> + }
> + return score;
> +}
> +
> struct sock *inet6_lookup_listener(struct net *net,
> struct inet_hashinfo *hashinfo, const struct in6_addr *daddr,
> const unsigned short hnum, const int dif)
> {
> struct sock *sk;
> - const struct hlist_node *node;
> - struct sock *result = NULL;
> - int score, hiscore = 0;
> - struct inet_listen_hashbucket *ilb;
> -
> - ilb = &hashinfo->listening_hash[inet_lhashfn(net, hnum)];
> - spin_lock(&ilb->lock);
> - sk_for_each(sk, node, &ilb->head) {
> - if (net_eq(sock_net(sk), net) && inet_sk(sk)->num == hnum &&
> - sk->sk_family == PF_INET6) {
> - const struct ipv6_pinfo *np = inet6_sk(sk);
> -
> - score = 1;
> - if (!ipv6_addr_any(&np->rcv_saddr)) {
> - if (!ipv6_addr_equal(&np->rcv_saddr, daddr))
> - continue;
> - score++;
> - }
> - if (sk->sk_bound_dev_if) {
> - if (sk->sk_bound_dev_if != dif)
> - continue;
> - score++;
> - }
> - if (score == 3) {
> - result = sk;
> - break;
> - }
> - if (score > hiscore) {
> - hiscore = score;
> - result = sk;
> - }
> + const struct hlist_nulls_node *node;
> + struct sock *result;
> + int score, hiscore;
> + unsigned int hash = inet_lhashfn(net, hnum);
> + struct inet_listen_hashbucket *ilb = &hashinfo->listening_hash[hash];
> +
> + rcu_read_lock();
> +begin:
> + result = NULL;
> + hiscore = -1;
> + sk_nulls_for_each(sk, node, &ilb->head) {
> + score = compute_score(sk, net, hnum, daddr, dif);
> + if (score > hiscore) {
> + hiscore = score;
> + result = sk;
> }
> }
> - if (result)
> - sock_hold(result);
> - spin_unlock(&ilb->lock);
> + /*
> + * if the nulls value we got at the end of this lookup is
> + * not the expected one, we must restart lookup.
> + * We probably met an item that was moved to another chain.
> + */
> + if (get_nulls_value(node) != hash + LISTENING_NULLS_BASE)
> + goto begin;
> + if (result) {
> + if (unlikely(!atomic_inc_not_zero(&result->sk_refcnt)))
> + result = NULL;
> + else if (unlikely(compute_score(result, net, hnum, daddr,
> + dif) < hiscore)) {
> + sock_put(result);
> + goto begin;
> + }
> + }
> + rcu_read_unlock();
> return result;
> }
>
--
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