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From: Florian Westphal <fw@strlen.de>
To: <netfilter-devel@vger.kernel.org>
Cc: Florian Westphal <fw@strlen.de>
Subject: [PATCH nf-next 1/4] netfilter: nf_tables: remove unneeded conditional
Date: Fri, 14 Apr 2023 15:01:31 +0200	[thread overview]
Message-ID: <20230414130134.29040-2-fw@strlen.de> (raw)
In-Reply-To: <20230414130134.29040-1-fw@strlen.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@strlen.de>
---
 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,
-- 
2.39.2


  reply	other threads:[~2023-04-14 13:01 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-14 13:01 [PATCH nf-next 0/4] netfilter: nf_tables: shrink stack usage a bit more Florian Westphal
2023-04-14 13:01 ` Florian Westphal [this message]
2023-04-14 13:01 ` [PATCH nf-next 2/4] netfilter: nf_tables: do not store pktinfo in traceinfo structure Florian Westphal
2023-04-14 13:01 ` [PATCH nf-next 3/4] netfilter: nf_tables: do not store verdict " Florian Westphal
2023-04-14 13:01 ` [PATCH nf-next 4/4] netfilter: nf_tables: do not store rule " Florian Westphal

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