android_kernel_xiaomi_sm8350/net/ipv4/inet_timewait_sock.c
Eric W. Biederman 575f4cd5a5 net: Use rcu lookups in inet_twsk_purge.
While we are looking up entries to free there is no reason to take
the lock in inet_twsk_purge.  We have to drop locks and restart
occassionally anyway so adding a few more in case we get on the
wrong list because of a timewait move is no big deal.  At the
same time not taking the lock for long periods of time is much
more polite to the rest of the users of the hash table.

In my test configuration of killing 4k network namespaces
this change causes 4k back to back runs of inet_twsk_purge on an
empty hash table to go from roughly 20.7s to 3.3s, and the total
time to destroy 4k network namespaces goes from roughly 44s to
3.3s.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-12-03 12:23:47 -08:00

467 lines
13 KiB
C

/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* Generic TIME_WAIT sockets functions
*
* From code orinally in TCP
*/
#include <linux/kernel.h>
#include <linux/kmemcheck.h>
#include <net/inet_hashtables.h>
#include <net/inet_timewait_sock.h>
#include <net/ip.h>
/* Must be called with locally disabled BHs. */
static void __inet_twsk_kill(struct inet_timewait_sock *tw,
struct inet_hashinfo *hashinfo)
{
struct inet_bind_hashbucket *bhead;
struct inet_bind_bucket *tb;
/* Unlink from established hashes. */
spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
spin_lock(lock);
if (hlist_nulls_unhashed(&tw->tw_node)) {
spin_unlock(lock);
return;
}
hlist_nulls_del_rcu(&tw->tw_node);
sk_nulls_node_init(&tw->tw_node);
spin_unlock(lock);
/* Disassociate with bind bucket. */
bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
hashinfo->bhash_size)];
spin_lock(&bhead->lock);
tb = tw->tw_tb;
__hlist_del(&tw->tw_bind_node);
tw->tw_tb = NULL;
inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
spin_unlock(&bhead->lock);
#ifdef SOCK_REFCNT_DEBUG
if (atomic_read(&tw->tw_refcnt) != 1) {
printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n",
tw->tw_prot->name, tw, atomic_read(&tw->tw_refcnt));
}
#endif
inet_twsk_put(tw);
}
static noinline void inet_twsk_free(struct inet_timewait_sock *tw)
{
struct module *owner = tw->tw_prot->owner;
twsk_destructor((struct sock *)tw);
#ifdef SOCK_REFCNT_DEBUG
pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
#endif
release_net(twsk_net(tw));
kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
module_put(owner);
}
void inet_twsk_put(struct inet_timewait_sock *tw)
{
if (atomic_dec_and_test(&tw->tw_refcnt))
inet_twsk_free(tw);
}
EXPORT_SYMBOL_GPL(inet_twsk_put);
/*
* Enter the time wait state. This is called with locally disabled BH.
* Essentially we whip up a timewait bucket, copy the relevant info into it
* from the SK, and mess with hash chains and list linkage.
*/
void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
struct inet_hashinfo *hashinfo)
{
const struct inet_sock *inet = inet_sk(sk);
const struct inet_connection_sock *icsk = inet_csk(sk);
struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
struct inet_bind_hashbucket *bhead;
/* Step 1: Put TW into bind hash. Original socket stays there too.
Note, that any socket with inet->num != 0 MUST be bound in
binding cache, even if it is closed.
*/
bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
hashinfo->bhash_size)];
spin_lock(&bhead->lock);
tw->tw_tb = icsk->icsk_bind_hash;
WARN_ON(!icsk->icsk_bind_hash);
inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
spin_unlock(&bhead->lock);
spin_lock(lock);
/*
* Step 2: Hash TW into TIMEWAIT chain.
* Should be done before removing sk from established chain
* because readers are lockless and search established first.
*/
atomic_inc(&tw->tw_refcnt);
inet_twsk_add_node_rcu(tw, &ehead->twchain);
/* Step 3: Remove SK from established hash. */
if (__sk_nulls_del_node_init_rcu(sk))
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
spin_unlock(lock);
}
EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state)
{
struct inet_timewait_sock *tw =
kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
GFP_ATOMIC);
if (tw != NULL) {
const struct inet_sock *inet = inet_sk(sk);
kmemcheck_annotate_bitfield(tw, flags);
/* Give us an identity. */
tw->tw_daddr = inet->inet_daddr;
tw->tw_rcv_saddr = inet->inet_rcv_saddr;
tw->tw_bound_dev_if = sk->sk_bound_dev_if;
tw->tw_num = inet->inet_num;
tw->tw_state = TCP_TIME_WAIT;
tw->tw_substate = state;
tw->tw_sport = inet->inet_sport;
tw->tw_dport = inet->inet_dport;
tw->tw_family = sk->sk_family;
tw->tw_reuse = sk->sk_reuse;
tw->tw_hash = sk->sk_hash;
tw->tw_ipv6only = 0;
tw->tw_transparent = inet->transparent;
tw->tw_prot = sk->sk_prot_creator;
twsk_net_set(tw, hold_net(sock_net(sk)));
atomic_set(&tw->tw_refcnt, 1);
inet_twsk_dead_node_init(tw);
__module_get(tw->tw_prot->owner);
}
return tw;
}
EXPORT_SYMBOL_GPL(inet_twsk_alloc);
/* Returns non-zero if quota exceeded. */
static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
const int slot)
{
struct inet_timewait_sock *tw;
struct hlist_node *node;
unsigned int killed;
int ret;
/* NOTE: compare this to previous version where lock
* was released after detaching chain. It was racy,
* because tw buckets are scheduled in not serialized context
* in 2.3 (with netfilter), and with softnet it is common, because
* soft irqs are not sequenced.
*/
killed = 0;
ret = 0;
rescan:
inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) {
__inet_twsk_del_dead_node(tw);
spin_unlock(&twdr->death_lock);
__inet_twsk_kill(tw, twdr->hashinfo);
#ifdef CONFIG_NET_NS
NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED);
#endif
inet_twsk_put(tw);
killed++;
spin_lock(&twdr->death_lock);
if (killed > INET_TWDR_TWKILL_QUOTA) {
ret = 1;
break;
}
/* While we dropped twdr->death_lock, another cpu may have
* killed off the next TW bucket in the list, therefore
* do a fresh re-read of the hlist head node with the
* lock reacquired. We still use the hlist traversal
* macro in order to get the prefetches.
*/
goto rescan;
}
twdr->tw_count -= killed;
#ifndef CONFIG_NET_NS
NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITED, killed);
#endif
return ret;
}
void inet_twdr_hangman(unsigned long data)
{
struct inet_timewait_death_row *twdr;
int unsigned need_timer;
twdr = (struct inet_timewait_death_row *)data;
spin_lock(&twdr->death_lock);
if (twdr->tw_count == 0)
goto out;
need_timer = 0;
if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
twdr->thread_slots |= (1 << twdr->slot);
schedule_work(&twdr->twkill_work);
need_timer = 1;
} else {
/* We purged the entire slot, anything left? */
if (twdr->tw_count)
need_timer = 1;
twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
}
if (need_timer)
mod_timer(&twdr->tw_timer, jiffies + twdr->period);
out:
spin_unlock(&twdr->death_lock);
}
EXPORT_SYMBOL_GPL(inet_twdr_hangman);
void inet_twdr_twkill_work(struct work_struct *work)
{
struct inet_timewait_death_row *twdr =
container_of(work, struct inet_timewait_death_row, twkill_work);
int i;
BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) >
(sizeof(twdr->thread_slots) * 8));
while (twdr->thread_slots) {
spin_lock_bh(&twdr->death_lock);
for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
if (!(twdr->thread_slots & (1 << i)))
continue;
while (inet_twdr_do_twkill_work(twdr, i) != 0) {
if (need_resched()) {
spin_unlock_bh(&twdr->death_lock);
schedule();
spin_lock_bh(&twdr->death_lock);
}
}
twdr->thread_slots &= ~(1 << i);
}
spin_unlock_bh(&twdr->death_lock);
}
}
EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);
/* These are always called from BH context. See callers in
* tcp_input.c to verify this.
*/
/* This is for handling early-kills of TIME_WAIT sockets. */
void inet_twsk_deschedule(struct inet_timewait_sock *tw,
struct inet_timewait_death_row *twdr)
{
spin_lock(&twdr->death_lock);
if (inet_twsk_del_dead_node(tw)) {
inet_twsk_put(tw);
if (--twdr->tw_count == 0)
del_timer(&twdr->tw_timer);
}
spin_unlock(&twdr->death_lock);
__inet_twsk_kill(tw, twdr->hashinfo);
}
EXPORT_SYMBOL(inet_twsk_deschedule);
void inet_twsk_schedule(struct inet_timewait_sock *tw,
struct inet_timewait_death_row *twdr,
const int timeo, const int timewait_len)
{
struct hlist_head *list;
int slot;
/* timeout := RTO * 3.5
*
* 3.5 = 1+2+0.5 to wait for two retransmits.
*
* RATIONALE: if FIN arrived and we entered TIME-WAIT state,
* our ACK acking that FIN can be lost. If N subsequent retransmitted
* FINs (or previous seqments) are lost (probability of such event
* is p^(N+1), where p is probability to lose single packet and
* time to detect the loss is about RTO*(2^N - 1) with exponential
* backoff). Normal timewait length is calculated so, that we
* waited at least for one retransmitted FIN (maximal RTO is 120sec).
* [ BTW Linux. following BSD, violates this requirement waiting
* only for 60sec, we should wait at least for 240 secs.
* Well, 240 consumes too much of resources 8)
* ]
* This interval is not reduced to catch old duplicate and
* responces to our wandering segments living for two MSLs.
* However, if we use PAWS to detect
* old duplicates, we can reduce the interval to bounds required
* by RTO, rather than MSL. So, if peer understands PAWS, we
* kill tw bucket after 3.5*RTO (it is important that this number
* is greater than TS tick!) and detect old duplicates with help
* of PAWS.
*/
slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
spin_lock(&twdr->death_lock);
/* Unlink it, if it was scheduled */
if (inet_twsk_del_dead_node(tw))
twdr->tw_count--;
else
atomic_inc(&tw->tw_refcnt);
if (slot >= INET_TWDR_RECYCLE_SLOTS) {
/* Schedule to slow timer */
if (timeo >= timewait_len) {
slot = INET_TWDR_TWKILL_SLOTS - 1;
} else {
slot = DIV_ROUND_UP(timeo, twdr->period);
if (slot >= INET_TWDR_TWKILL_SLOTS)
slot = INET_TWDR_TWKILL_SLOTS - 1;
}
tw->tw_ttd = jiffies + timeo;
slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
list = &twdr->cells[slot];
} else {
tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK);
if (twdr->twcal_hand < 0) {
twdr->twcal_hand = 0;
twdr->twcal_jiffie = jiffies;
twdr->twcal_timer.expires = twdr->twcal_jiffie +
(slot << INET_TWDR_RECYCLE_TICK);
add_timer(&twdr->twcal_timer);
} else {
if (time_after(twdr->twcal_timer.expires,
jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
mod_timer(&twdr->twcal_timer,
jiffies + (slot << INET_TWDR_RECYCLE_TICK));
slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
}
list = &twdr->twcal_row[slot];
}
hlist_add_head(&tw->tw_death_node, list);
if (twdr->tw_count++ == 0)
mod_timer(&twdr->tw_timer, jiffies + twdr->period);
spin_unlock(&twdr->death_lock);
}
EXPORT_SYMBOL_GPL(inet_twsk_schedule);
void inet_twdr_twcal_tick(unsigned long data)
{
struct inet_timewait_death_row *twdr;
int n, slot;
unsigned long j;
unsigned long now = jiffies;
int killed = 0;
int adv = 0;
twdr = (struct inet_timewait_death_row *)data;
spin_lock(&twdr->death_lock);
if (twdr->twcal_hand < 0)
goto out;
slot = twdr->twcal_hand;
j = twdr->twcal_jiffie;
for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
if (time_before_eq(j, now)) {
struct hlist_node *node, *safe;
struct inet_timewait_sock *tw;
inet_twsk_for_each_inmate_safe(tw, node, safe,
&twdr->twcal_row[slot]) {
__inet_twsk_del_dead_node(tw);
__inet_twsk_kill(tw, twdr->hashinfo);
#ifdef CONFIG_NET_NS
NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
#endif
inet_twsk_put(tw);
killed++;
}
} else {
if (!adv) {
adv = 1;
twdr->twcal_jiffie = j;
twdr->twcal_hand = slot;
}
if (!hlist_empty(&twdr->twcal_row[slot])) {
mod_timer(&twdr->twcal_timer, j);
goto out;
}
}
j += 1 << INET_TWDR_RECYCLE_TICK;
slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
}
twdr->twcal_hand = -1;
out:
if ((twdr->tw_count -= killed) == 0)
del_timer(&twdr->tw_timer);
#ifndef CONFIG_NET_NS
NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITKILLED, killed);
#endif
spin_unlock(&twdr->death_lock);
}
EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);
void inet_twsk_purge(struct net *net, struct inet_hashinfo *hashinfo,
struct inet_timewait_death_row *twdr, int family)
{
struct inet_timewait_sock *tw;
struct sock *sk;
struct hlist_nulls_node *node;
unsigned int slot;
for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
restart_rcu:
rcu_read_lock();
restart:
sk_nulls_for_each_rcu(sk, node, &head->twchain) {
tw = inet_twsk(sk);
if (!net_eq(twsk_net(tw), net) ||
tw->tw_family != family)
continue;
if (unlikely(!atomic_inc_not_zero(&tw->tw_refcnt)))
continue;
if (unlikely(!net_eq(twsk_net(tw), net) ||
tw->tw_family != family)) {
inet_twsk_put(tw);
goto restart;
}
rcu_read_unlock();
inet_twsk_deschedule(tw, twdr);
inet_twsk_put(tw);
goto restart_rcu;
}
/* 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) != slot)
goto restart;
rcu_read_unlock();
}
}
EXPORT_SYMBOL_GPL(inet_twsk_purge);