linux-kernel - [PATCH net-next] sctp: deduplicate identical skb_checksum

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Date:   Wed, 29 May 2019 17:39:41 +0200
From:   Matteo Croce <mcroce@...hat.com>
To:     linux-sctp@...r.kernel.org, netdev@...r.kernel.org
Cc:     Vlad Yasevich <vyasevich@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next] sctp: deduplicate identical skb_checksum_ops

The same skb_checksum_ops struct is defined twice in two different places,
leading to code duplication. Declare it as a global variable into a common
header instead of allocating it on the stack on each function call.
bloat-o-meter reports a slight code shrink.

add/remove: 1/1 grow/shrink: 0/10 up/down: 128/-1282 (-1154)
Function                                     old     new   delta
sctp_csum_ops                                  -     128    +128
crc32c_csum_ops                               16       -     -16
sctp_rcv                                    6616    6583     -33
sctp_packet_pack                            4542    4504     -38
nf_conntrack_sctp_packet                    4980    4926     -54
execute_masked_set_action                   6453    6389     -64
tcf_csum_sctp                                575     428    -147
sctp_gso_segment                            1292    1126    -166
sctp_csum_check                              579     412    -167
sctp_snat_handler                            957     772    -185
sctp_dnat_handler                           1321    1132    -189
l4proto_manip_pkt                           2536    2313    -223
Total: Before=359297613, After=359296459, chg -0.00%

Reviewed-by: Xin Long <lucien.xin@...il.com>
Signed-off-by: Matteo Croce <mcroce@...hat.com>
---
 include/net/sctp/checksum.h | 12 +++++++-----
 net/sctp/offload.c          |  7 +------
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/include/net/sctp/checksum.h b/include/net/sctp/checksum.h
index 314699333bec..5a9bb09f32b6 100644
--- a/include/net/sctp/checksum.h
+++ b/include/net/sctp/checksum.h
@@ -43,19 +43,21 @@ static inline __wsum sctp_csum_combine(__wsum csum, __wsum csum2,
 						   (__force __u32)csum2, len);
 }
 
+static const struct skb_checksum_ops sctp_csum_ops = {
+	.update  = sctp_csum_update,
+	.combine = sctp_csum_combine,
+};
+
 static inline __le32 sctp_compute_cksum(const struct sk_buff *skb,
 					unsigned int offset)
 {
 	struct sctphdr *sh = (struct sctphdr *)(skb->data + offset);
-	const struct skb_checksum_ops ops = {
-		.update  = sctp_csum_update,
-		.combine = sctp_csum_combine,
-	};
 	__le32 old = sh->checksum;
 	__wsum new;
 
 	sh->checksum = 0;
-	new = ~__skb_checksum(skb, offset, skb->len - offset, ~(__wsum)0, &ops);
+	new = ~__skb_checksum(skb, offset, skb->len - offset, ~(__wsum)0,
+			      &sctp_csum_ops);
 	sh->checksum = old;
 
 	return cpu_to_le32((__force __u32)new);
diff --git a/net/sctp/offload.c b/net/sctp/offload.c
index edfcf16e704c..dac46dfadab5 100644
--- a/net/sctp/offload.c
+++ b/net/sctp/offload.c
@@ -103,11 +103,6 @@ static const struct net_offload sctp6_offload = {
 	},
 };
 
-static const struct skb_checksum_ops crc32c_csum_ops = {
-	.update  = sctp_csum_update,
-	.combine = sctp_csum_combine,
-};
-
 int __init sctp_offload_init(void)
 {
 	int ret;
@@ -120,7 +115,7 @@ int __init sctp_offload_init(void)
 	if (ret)
 		goto ipv4;
 
-	crc32c_csum_stub = &crc32c_csum_ops;
+	crc32c_csum_stub = &sctp_csum_ops;
 	return ret;
 
 ipv4:
-- 
2.21.0