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tcp: Don't allocate tcp_death_row outside of struct netns_ipv4.

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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
fbb8295248 ("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 04c494e68a ("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 <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Kuniyuki Iwashima 2022-09-07 18:10:18 -07:00 • committed by Jakub Kicinski
parent 08eaef9040
commit e9bd0cca09
7 changed files with 15 additions and 25 deletions
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2
net/ipv6/tcp_ipv6.c
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@ -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;