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From: Colin King <colin.king@canonical.com>
To: Eric Dumazet <edumazet@google.com>,
	"David S . Miller" <davem@davemloft.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	netdev@vger.kernel.org
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] tcp: remove redundant check on tskb
Date: Thu,  4 Apr 2019 15:46:03 +0100	[thread overview]
Message-ID: <20190404144603.27682-1-colin.king@canonical.com> (raw)

From: Colin Ian King <colin.king@canonical.com>

The non-null check on tskb is always false because it is in an else
path of a check on tskb and hence tskb is null in this code block.
This is check is therefore redundant and can be removed as well
as the label coalesc.

if (tsbk) {
        ...
} else {
        ...
        if (unlikely(!skb)) {
                if (tskb)       /* can never be true, redundant code */
                        goto coalesc;
                return;
        }
}

Addresses-Coverity: ("Logically dead code")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 net/ipv4/tcp_output.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e265d1aeeb66..32061928b054 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3088,7 +3088,6 @@ void tcp_send_fin(struct sock *sk)
 		tskb = skb_rb_last(&sk->tcp_rtx_queue);
 
 	if (tskb) {
-coalesce:
 		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
 		TCP_SKB_CB(tskb)->end_seq++;
 		tp->write_seq++;
@@ -3104,11 +3103,9 @@ void tcp_send_fin(struct sock *sk)
 		}
 	} else {
 		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
-		if (unlikely(!skb)) {
-			if (tskb)
-				goto coalesce;
+		if (unlikely(!skb))
 			return;
-		}
+
 		INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
 		skb_reserve(skb, MAX_TCP_HEADER);
 		sk_forced_mem_schedule(sk, skb->truesize);
-- 
2.20.1


WARNING: multiple messages have this Message-ID (diff)
From: Colin King <colin.king@canonical.com>
To: Eric Dumazet <edumazet@google.com>,
	"David S . Miller" <davem@davemloft.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	netdev@vger.kernel.org
Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] tcp: remove redundant check on tskb
Date: Thu, 04 Apr 2019 14:46:03 +0000	[thread overview]
Message-ID: <20190404144603.27682-1-colin.king@canonical.com> (raw)

From: Colin Ian King <colin.king@canonical.com>

The non-null check on tskb is always false because it is in an else
path of a check on tskb and hence tskb is null in this code block.
This is check is therefore redundant and can be removed as well
as the label coalesc.

if (tsbk) {
        ...
} else {
        ...
        if (unlikely(!skb)) {
                if (tskb)       /* can never be true, redundant code */
                        goto coalesc;
                return;
        }
}

Addresses-Coverity: ("Logically dead code")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 net/ipv4/tcp_output.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e265d1aeeb66..32061928b054 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3088,7 +3088,6 @@ void tcp_send_fin(struct sock *sk)
 		tskb = skb_rb_last(&sk->tcp_rtx_queue);
 
 	if (tskb) {
-coalesce:
 		TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN;
 		TCP_SKB_CB(tskb)->end_seq++;
 		tp->write_seq++;
@@ -3104,11 +3103,9 @@ void tcp_send_fin(struct sock *sk)
 		}
 	} else {
 		skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation);
-		if (unlikely(!skb)) {
-			if (tskb)
-				goto coalesce;
+		if (unlikely(!skb))
 			return;
-		}
+
 		INIT_LIST_HEAD(&skb->tcp_tsorted_anchor);
 		skb_reserve(skb, MAX_TCP_HEADER);
 		sk_forced_mem_schedule(sk, skb->truesize);
-- 
2.20.1

             reply	other threads:[~2019-04-04 14:46 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-04 14:46 Colin King [this message]
2019-04-04 14:46 ` [PATCH] tcp: remove redundant check on tskb Colin King
2019-04-04 15:05 ` Dan Carpenter
2019-04-04 15:05   ` Dan Carpenter
2019-04-05  6:47 ` Mukesh Ojha
2019-04-05  6:59   ` Mukesh Ojha
2019-04-05  7:46 ` Eric Dumazet
2019-04-05  7:46   ` Eric Dumazet
2019-04-07  1:18 ` David Miller
2019-04-07  1:18   ` David Miller

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