Re: [PATCH net-next] tcp: fix the calculation of sysctl_max_tw_buckets in tcp_sk_init()
From: David Miller <davem@davemloft.net>
Date: 2018-08-06 20:41:20
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From: Yafang Shao <redacted> Date: Mon, 6 Aug 2018 19:47:00 +0800
tcp_hashinfo.ehash_mask is always an odd number, which is set in function
alloc_large_system_hash(). See bellow,
if (_hash_mask)
*_hash_mask = (1 << log2qty) - 1; <<< always odd number
Hence the local variable 'cnt' is a even number, as a result of that it is
no difference to do the incrementation here.
Maybe the compiler could also optimize it, but this code is a little ugly.
Fix: fee83d09 ("ipv4: Namespaceify tcp_max_syn_backlog knob")The correct tag is "Fixes: "
quoted hunk ↗ jump to hunk
@@ -2543,7 +2543,7 @@ static int __net_init tcp_sk_init(struct net *net) net->ipv4.sysctl_tcp_tw_reuse = 2; cnt = tcp_hashinfo.ehash_mask + 1; - net->ipv4.tcp_death_row.sysctl_max_tw_buckets = (cnt + 1) / 2; + net->ipv4.tcp_death_row.sysctl_max_tw_buckets = cnt / 2; net->ipv4.tcp_death_row.hashinfo = &tcp_hashinfo;
This is completely harmless, and does no harm. You aren't "fixing" anything.