[PATCH v2 net-next 4/5] tcp: Save unnecessary inet_twsk_purge() calls.
From: Kuniyuki Iwashima <hidden>
Date: 2022-08-29 16:21:47
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
While destroying netns, we call inet_twsk_purge() in tcp_sk_exit_batch() and tcpv6_net_exit_batch() for AF_INET and AF_INET6. These commands trigger the kernel to walk through the potentially big ehash twice even though the netns has no TIME_WAIT sockets. # ip netns add test # ip netns del test AF_INET6 uses module_init() to be loaded after AF_INET which uses fs_initcall(), so tcpv6_net_ops is always registered after tcp_sk_ops. Also, we clean up netns in the reverse order, so tcpv6_net_exit_batch() is always called before tcp_sk_exit_batch(). The characteristic enables us to save such unneeded iterations. This change eliminates the tax by the additional unshare() described in the next patch to guarantee the per-netns ehash size. Signed-off-by: Kuniyuki Iwashima <redacted> --- include/net/tcp.h | 1 + net/ipv4/tcp_ipv4.c | 6 ++++-- net/ipv4/tcp_minisocks.c | 24 ++++++++++++++++++++++++ net/ipv6/tcp_ipv6.c | 2 +- 4 files changed, 30 insertions(+), 3 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index d10962b9f0d0..f60996c1d7b3 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h@@ -346,6 +346,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb); void tcp_rcv_space_adjust(struct sock *sk); int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp); void tcp_twsk_destructor(struct sock *sk); +void tcp_twsk_purge(struct list_head *net_exit_list, int family); ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index b07930643b11..f4a502d57d45 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c@@ -3109,8 +3109,10 @@ static void __net_exit tcp_sk_exit(struct net *net) 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)) + if (refcount_dec_and_test(&tcp_death_row->tw_refcount)) { kfree(tcp_death_row); + net->ipv4.tcp_death_row = NULL; + } } static int __net_init tcp_sk_init(struct net *net)
@@ -3210,7 +3212,7 @@ static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list) { struct net *net; - inet_twsk_purge(&tcp_hashinfo, AF_INET); + tcp_twsk_purge(net_exit_list, AF_INET); list_for_each_entry(net, net_exit_list, exit_list) tcp_fastopen_ctx_destroy(net);
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 361aad67c6d6..9168c5a33344 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c@@ -347,6 +347,30 @@ void tcp_twsk_destructor(struct sock *sk) } EXPORT_SYMBOL_GPL(tcp_twsk_destructor); +void tcp_twsk_purge(struct list_head *net_exit_list, int family) +{ + struct net *net; + + list_for_each_entry(net, net_exit_list, exit_list) { + if (!net->ipv4.tcp_death_row) + continue; + + /* AF_INET6 using module_init() is always registered after + * AF_INET using fs_initcall() and cleaned up in the reverse + * order. + * + * The last refcount is decremented later in tcp_sk_exit(). + */ + if (IS_ENABLED(CONFIG_IPV6) && family == AF_INET6 && + refcount_read(&net->ipv4.tcp_death_row->tw_refcount) == 1) + continue; + + inet_twsk_purge(&tcp_hashinfo, family); + break; + } +} +EXPORT_SYMBOL_GPL(tcp_twsk_purge); + /* Warning : This function is called without sk_listener being locked. * Be sure to read socket fields once, as their value could change under us. */
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 27b2fd98a2c4..9cbc7f0d7149 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c@@ -2229,7 +2229,7 @@ static void __net_exit tcpv6_net_exit(struct net *net) static void __net_exit tcpv6_net_exit_batch(struct list_head *net_exit_list) { - inet_twsk_purge(&tcp_hashinfo, AF_INET6); + tcp_twsk_purge(net_exit_list, AF_INET6); } static struct pernet_operations tcpv6_net_ops = {
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2.30.2