netdev - [PATCH net-next 06/19] netfilter: nf_tables: remove unneeded conditional

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Message-Id: <20230421235021.216950-7-pablo@netfilter.org>
Date:   Sat, 22 Apr 2023 01:50:08 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, kuba@...nel.org,
        pabeni@...hat.com, edumazet@...gle.com
Subject: [PATCH net-next 06/19] netfilter: nf_tables: remove unneeded conditional

From: Florian Westphal <fw@...len.de>

This helper is inlined, so keep it as small as possible.

If the static key is true, there is only a very small chance
that info->trace is false:

1. tracing was enabled at this very moment, the static key was
   updated to active right after nft_do_table was called.

2. tracing was disabled at this very moment.
   trace->info is already false, the static key is about to
   be patched to false soon.

In both cases, no event will be sent because info->trace
is false (checked in noinline slowpath). info->nf_trace is irrelevant.

The nf_trace update is redunant in this case, but this will only
happen for short duration, when static key flips.

       text  data   bss   dec   hex filename
old:   2980   192    32  3204   c84 nf_tables_core.o
new:   2964   192    32  3188   c74i nf_tables_core.o

Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_tables_core.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c
index 89c05b64c2a2..bed855638050 100644
--- a/net/netfilter/nf_tables_core.c
+++ b/net/netfilter/nf_tables_core.c
@@ -67,10 +67,8 @@ static inline void nft_trace_packet(const struct nft_pktinfo *pkt,
 static inline void nft_trace_copy_nftrace(const struct nft_pktinfo *pkt,
 					  struct nft_traceinfo *info)
 {
-	if (static_branch_unlikely(&nft_trace_enabled)) {
-		if (info->trace)
-			info->nf_trace = pkt->skb->nf_trace;
-	}
+	if (static_branch_unlikely(&nft_trace_enabled))
+		info->nf_trace = pkt->skb->nf_trace;
 }

 static void nft_bitwise_fast_eval(const struct nft_expr *expr,
-- 
2.30.2