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inet: simplify timewait refcounting

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timewait sockets have a complex refcounting logic.
Once we realize it should be similar to established and
syn_recv sockets, we can use sk_nulls_del_node_init_rcu()
and remove inet_twsk_unhash()

In particular, deferred inet_twsk_put() added in commit
13475a30b6 ("tcp: connect() race with timewait reuse")
looks unecessary : When removing a timewait socket from
ehash or bhash, caller must own a reference on the socket
anyway.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2015-07-08 14:28:29 -07:00 committed by David S. Miller
parent 3fd2f1b9d9
commit fc01538f9f
5 changed files with 21 additions and 68 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/net/inet_hashtables.h
View File

@ -205,8 +205,8 @@ void inet_put_port(struct sock *sk);
void inet_hashinfo_init(struct inet_hashinfo *h);
int __inet_hash_nolisten(struct sock *sk, struct inet_timewait_sock *tw);
int __inet_hash(struct sock *sk, struct inet_timewait_sock *tw);
void __inet_hash_nolisten(struct sock *sk, struct sock *osk);
void __inet_hash(struct sock *sk, struct sock *osk);
void inet_hash(struct sock *sk);
void inet_unhash(struct sock *sk);

6
include/net/inet_timewait_sock.h
View File

@ -100,10 +100,8 @@ static inline struct inet_timewait_sock *inet_twsk(const struct sock *sk)
void inet_twsk_free(struct inet_timewait_sock *tw);
void inet_twsk_put(struct inet_timewait_sock *tw);
int inet_twsk_unhash(struct inet_timewait_sock *tw);
int inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
struct inet_hashinfo *hashinfo);
void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
struct inet_hashinfo *hashinfo);
struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk,
struct inet_timewait_death_row *dr,

31
net/ipv4/inet_hashtables.c
View File

@ -343,7 +343,6 @@ static int __inet_check_established(struct inet_timewait_death_row *death_row,
struct sock *sk2;
const struct hlist_nulls_node *node;
struct inet_timewait_sock *tw = NULL;
int twrefcnt = 0;
spin_lock(lock);
@ -371,12 +370,10 @@ static int __inet_check_established(struct inet_timewait_death_row *death_row,
WARN_ON(!sk_unhashed(sk));
__sk_nulls_add_node_rcu(sk, &head->chain);
if (tw) {
twrefcnt = inet_twsk_unhash(tw);
sk_nulls_del_node_init_rcu((struct sock *)tw);
NET_INC_STATS_BH(net, LINUX_MIB_TIMEWAITRECYCLED);
}
spin_unlock(lock);
if (twrefcnt)
inet_twsk_put(tw);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
if (twp) {
@ -384,7 +381,6 @@ static int __inet_check_established(struct inet_timewait_death_row *death_row,
} else if (tw) {
/* Silly. Should hash-dance instead... */
inet_twsk_deschedule(tw);
inet_twsk_put(tw);
}
return 0;
@ -403,13 +399,12 @@ static u32 inet_sk_port_offset(const struct sock *sk)
inet->inet_dport);
}
int __inet_hash_nolisten(struct sock *sk, struct inet_timewait_sock *tw)
void __inet_hash_nolisten(struct sock *sk, struct sock *osk)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
struct hlist_nulls_head *list;
struct inet_ehash_bucket *head;
spinlock_t *lock;
int twrefcnt = 0;
WARN_ON(!sk_unhashed(sk));
@ -420,23 +415,22 @@ int __inet_hash_nolisten(struct sock *sk, struct inet_timewait_sock *tw)
spin_lock(lock);
__sk_nulls_add_node_rcu(sk, list);
if (tw) {
WARN_ON(sk->sk_hash != tw->tw_hash);
twrefcnt = inet_twsk_unhash(tw);
if (osk) {
WARN_ON(sk->sk_hash != osk->sk_hash);
sk_nulls_del_node_init_rcu(osk);
}
spin_unlock(lock);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
return twrefcnt;
}
EXPORT_SYMBOL_GPL(__inet_hash_nolisten);
int __inet_hash(struct sock *sk, struct inet_timewait_sock *tw)
void __inet_hash(struct sock *sk, struct sock *osk)
{
struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
struct inet_listen_hashbucket *ilb;
if (sk->sk_state != TCP_LISTEN)
return __inet_hash_nolisten(sk, tw);
return __inet_hash_nolisten(sk, osk);
WARN_ON(!sk_unhashed(sk));
ilb = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
@ -445,7 +439,6 @@ int __inet_hash(struct sock *sk, struct inet_timewait_sock *tw)
__sk_nulls_add_node_rcu(sk, &ilb->head);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
spin_unlock(&ilb->lock);
return 0;
}
EXPORT_SYMBOL(__inet_hash);
@ -492,7 +485,6 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
struct inet_bind_bucket *tb;
int ret;
struct net *net = sock_net(sk);
int twrefcnt = 1;
if (!snum) {
int i, remaining, low, high, port;
@ -560,18 +552,15 @@ ok:
inet_bind_hash(sk, tb, port);
if (sk_unhashed(sk)) {
inet_sk(sk)->inet_sport = htons(port);
twrefcnt += __inet_hash_nolisten(sk, tw);
__inet_hash_nolisten(sk, (struct sock *)tw);
}
if (tw)
twrefcnt += inet_twsk_bind_unhash(tw, hinfo);
inet_twsk_bind_unhash(tw, hinfo);
spin_unlock(&head->lock);
if (tw) {
inet_twsk_deschedule(tw);
while (twrefcnt) {
twrefcnt--;
inet_twsk_put(tw);
}
inet_twsk_put(tw);
}
ret = 0;

42
net/ipv4/inet_timewait_sock.c
View File

@ -17,28 +17,6 @@
#include <net/ip.h>
/**
* inet_twsk_unhash - unhash a timewait socket from established hash
* @tw: timewait socket
*
* unhash a timewait socket from established hash, if hashed.
* ehash lock must be held by caller.
* Returns 1 if caller should call inet_twsk_put() after lock release.
*/
int inet_twsk_unhash(struct inet_timewait_sock *tw)
{
if (hlist_nulls_unhashed(&tw->tw_node))
return 0;
hlist_nulls_del_rcu(&tw->tw_node);
sk_nulls_node_init(&tw->tw_node);
/*
* We cannot call inet_twsk_put() ourself under lock,
* caller must call it for us.
*/
return 1;
}
/**
* inet_twsk_bind_unhash - unhash a timewait socket from bind hash
* @tw: timewait socket
@ -48,35 +26,29 @@ int inet_twsk_unhash(struct inet_timewait_sock *tw)
* bind hash lock must be held by caller.
* Returns 1 if caller should call inet_twsk_put() after lock release.
*/
int inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
void inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
struct inet_hashinfo *hashinfo)
{
struct inet_bind_bucket *tb = tw->tw_tb;
if (!tb)
return 0;
return;
__hlist_del(&tw->tw_bind_node);
tw->tw_tb = NULL;
inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
/*
* We cannot call inet_twsk_put() ourself under lock,
* caller must call it for us.
*/
return 1;
__sock_put((struct sock *)tw);
}
/* Must be called with locally disabled BHs. */
static void inet_twsk_kill(struct inet_timewait_sock *tw)
{
struct inet_hashinfo *hashinfo = tw->tw_dr->hashinfo;
struct inet_bind_hashbucket *bhead;
int refcnt;
/* Unlink from established hashes. */
spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
struct inet_bind_hashbucket *bhead;
spin_lock(lock);
refcnt = inet_twsk_unhash(tw);
sk_nulls_del_node_init_rcu((struct sock *)tw);
spin_unlock(lock);
/* Disassociate with bind bucket. */
@ -84,11 +56,9 @@ static void inet_twsk_kill(struct inet_timewait_sock *tw)
hashinfo->bhash_size)];
spin_lock(&bhead->lock);
refcnt += inet_twsk_bind_unhash(tw, hashinfo);
inet_twsk_bind_unhash(tw, hashinfo);
spin_unlock(&bhead->lock);
BUG_ON(refcnt >= atomic_read(&tw->tw_refcnt));
atomic_sub(refcnt, &tw->tw_refcnt);
atomic_dec(&tw->tw_dr->tw_count);
inet_twsk_put(tw);
}

6
net/ipv6/inet6_hashtables.c
View File

@ -207,7 +207,6 @@ static int __inet6_check_established(struct inet_timewait_death_row *death_row,
struct sock *sk2;
const struct hlist_nulls_node *node;
struct inet_timewait_sock *tw = NULL;
int twrefcnt = 0;
spin_lock(lock);
@ -234,12 +233,10 @@ static int __inet6_check_established(struct inet_timewait_death_row *death_row,
WARN_ON(!sk_unhashed(sk));
__sk_nulls_add_node_rcu(sk, &head->chain);
if (tw) {
twrefcnt = inet_twsk_unhash(tw);
sk_nulls_del_node_init_rcu((struct sock *)tw);
NET_INC_STATS_BH(net, LINUX_MIB_TIMEWAITRECYCLED);
}
spin_unlock(lock);
if (twrefcnt)
inet_twsk_put(tw);
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
if (twp) {
@ -247,7 +244,6 @@ static int __inet6_check_established(struct inet_timewait_death_row *death_row,
} else if (tw) {
/* Silly. Should hash-dance instead... */
inet_twsk_deschedule(tw);
inet_twsk_put(tw);
}
return 0;