From: Kuniyuki Iwashima Date: Thu, 8 Sep 2022 01:10:18 +0000 (-0700) Subject: tcp: Don't allocate tcp_death_row outside of struct netns_ipv4. X-Git-Tag: v6.6.17~6504^2~163^2~4 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=e9bd0cca09d13ac2f08d25e195203e42d4ad1ce8;p=platform%2Fkernel%2Flinux-rpi.git tcp: Don't allocate tcp_death_row outside of struct netns_ipv4. We will soon introduce an optional per-netns ehash and access hash tables via net->ipv4.tcp_death_row->hashinfo instead of &tcp_hashinfo in most places. It could harm the fast path because dereferences of two fields in net and tcp_death_row might incur two extra cache line misses. To save one dereference, let's place tcp_death_row back in netns_ipv4 and fetch hashinfo via net->ipv4.tcp_death_row"."hashinfo. Note tcp_death_row was initially placed in netns_ipv4, and commit fbb8295248e1 ("tcp: allocate tcp_death_row outside of struct netns_ipv4") changed it to a pointer so that we can fire TIME_WAIT timers after freeing net. However, we don't do so after commit 04c494e68a13 ("Revert "tcp/dccp: get rid of inet_twsk_purge()""), so we need not define tcp_death_row as a pointer. Also, we move refcount_dec_and_test(&tw_refcount) from tcp_sk_exit() to tcp_sk_exit_batch() as a debug check. Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Signed-off-by: Jakub Kicinski --- diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index 6320a76..2c7df93 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -34,6 +34,7 @@ struct inet_hashinfo; struct inet_timewait_death_row { refcount_t tw_refcount; + /* Padding to avoid false sharing, tw_refcount can be often written */ struct inet_hashinfo *hashinfo ____cacheline_aligned_in_smp; int sysctl_max_tw_buckets; }; @@ -41,7 +42,7 @@ struct inet_timewait_death_row { struct tcp_fastopen_context; struct netns_ipv4 { - struct inet_timewait_death_row *tcp_death_row; + struct inet_timewait_death_row tcp_death_row; #ifdef CONFIG_SYSCTL struct ctl_table_header *forw_hdr; diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c index 47ccc34..71d3bb0 100644 --- a/net/ipv4/inet_timewait_sock.c +++ b/net/ipv4/inet_timewait_sock.c @@ -59,9 +59,7 @@ static void inet_twsk_kill(struct inet_timewait_sock *tw) inet_twsk_bind_unhash(tw, hashinfo); spin_unlock(&bhead->lock); - if (refcount_dec_and_test(&tw->tw_dr->tw_refcount)) - kfree(tw->tw_dr); - + refcount_dec(&tw->tw_dr->tw_refcount); inet_twsk_put(tw); } diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c index 0088a4c..5386f46 100644 --- a/net/ipv4/proc.c +++ b/net/ipv4/proc.c @@ -59,7 +59,7 @@ static int sockstat_seq_show(struct seq_file *seq, void *v) socket_seq_show(seq); seq_printf(seq, "TCP: inuse %d orphan %d tw %d alloc %d mem %ld\n", sock_prot_inuse_get(net, &tcp_prot), orphans, - refcount_read(&net->ipv4.tcp_death_row->tw_refcount) - 1, + refcount_read(&net->ipv4.tcp_death_row.tw_refcount) - 1, sockets, proto_memory_allocated(&tcp_prot)); seq_printf(seq, "UDP: inuse %d mem %ld\n", sock_prot_inuse_get(net, &udp_prot), diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 5490c28..4d7c110 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -530,10 +530,9 @@ static struct ctl_table ipv4_table[] = { }; static struct ctl_table ipv4_net_table[] = { - /* tcp_max_tw_buckets must be first in this table. */ { .procname = "tcp_max_tw_buckets", -/* .data = &init_net.ipv4.tcp_death_row.sysctl_max_tw_buckets, */ + .data = &init_net.ipv4.tcp_death_row.sysctl_max_tw_buckets, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec @@ -1361,8 +1360,7 @@ static __net_init int ipv4_sysctl_init_net(struct net *net) if (!table) goto err_alloc; - /* skip first entry (sysctl_max_tw_buckets) */ - for (i = 1; i < ARRAY_SIZE(ipv4_net_table) - 1; i++) { + for (i = 0; i < ARRAY_SIZE(ipv4_net_table) - 1; i++) { if (table[i].data) { /* Update the variables to point into * the current struct net @@ -1377,8 +1375,6 @@ static __net_init int ipv4_sysctl_init_net(struct net *net) } } - table[0].data = &net->ipv4.tcp_death_row->sysctl_max_tw_buckets; - net->ipv4.ipv4_hdr = register_net_sysctl(net, "net/ipv4", table); if (!net->ipv4.ipv4_hdr) goto err_reg; diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index a07243f..3930b6a 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -292,7 +292,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len) * complete initialization after this. */ tcp_set_state(sk, TCP_SYN_SENT); - tcp_death_row = net->ipv4.tcp_death_row; + tcp_death_row = &net->ipv4.tcp_death_row; err = inet_hash_connect(tcp_death_row, sk); if (err) goto failure; @@ -3091,13 +3091,9 @@ EXPORT_SYMBOL(tcp_prot); static void __net_exit tcp_sk_exit(struct net *net) { - struct inet_timewait_death_row *tcp_death_row = net->ipv4.tcp_death_row; - if (net->ipv4.tcp_congestion_control) bpf_module_put(net->ipv4.tcp_congestion_control, net->ipv4.tcp_congestion_control->owner); - if (refcount_dec_and_test(&tcp_death_row->tw_refcount)) - kfree(tcp_death_row); } static int __net_init tcp_sk_init(struct net *net) @@ -3129,13 +3125,10 @@ static int __net_init tcp_sk_init(struct net *net) net->ipv4.sysctl_tcp_tw_reuse = 2; net->ipv4.sysctl_tcp_no_ssthresh_metrics_save = 1; - net->ipv4.tcp_death_row = kzalloc(sizeof(struct inet_timewait_death_row), GFP_KERNEL); - if (!net->ipv4.tcp_death_row) - return -ENOMEM; - refcount_set(&net->ipv4.tcp_death_row->tw_refcount, 1); + refcount_set(&net->ipv4.tcp_death_row.tw_refcount, 1); cnt = tcp_hashinfo.ehash_mask + 1; - net->ipv4.tcp_death_row->sysctl_max_tw_buckets = cnt / 2; - net->ipv4.tcp_death_row->hashinfo = &tcp_hashinfo; + net->ipv4.tcp_death_row.sysctl_max_tw_buckets = cnt / 2; + net->ipv4.tcp_death_row.hashinfo = &tcp_hashinfo; net->ipv4.sysctl_max_syn_backlog = max(128, cnt / 128); net->ipv4.sysctl_tcp_sack = 1; @@ -3201,8 +3194,10 @@ static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list) inet_twsk_purge(&tcp_hashinfo, AF_INET); - list_for_each_entry(net, net_exit_list, exit_list) + list_for_each_entry(net, net_exit_list, exit_list) { + WARN_ON_ONCE(!refcount_dec_and_test(&net->ipv4.tcp_death_row.tw_refcount)); tcp_fastopen_ctx_destroy(net); + } } static struct pernet_operations __net_initdata tcp_sk_ops = { diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c index 80ce27f..8bddb2a 100644 --- a/net/ipv4/tcp_minisocks.c +++ b/net/ipv4/tcp_minisocks.c @@ -250,7 +250,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo) struct net *net = sock_net(sk); struct inet_timewait_sock *tw; - tw = inet_twsk_alloc(sk, net->ipv4.tcp_death_row, state); + tw = inet_twsk_alloc(sk, &net->ipv4.tcp_death_row, state); if (tw) { struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw); diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 5c562d6..eb1da7a 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -325,7 +325,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr, inet->inet_dport = usin->sin6_port; tcp_set_state(sk, TCP_SYN_SENT); - tcp_death_row = net->ipv4.tcp_death_row; + tcp_death_row = &net->ipv4.tcp_death_row; err = inet6_hash_connect(tcp_death_row, sk); if (err) goto late_failure;