linux-kernel - [PATCH net-next v4 15/18] net: netcp: Remove usage of list iterator for list

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Date:   Fri, 15 Apr 2022 14:29:44 +0200
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Ariel Elior <aelior@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        Edward Cree <ecree.xilinx@...il.com>,
        Martin Habets <habetsm.xilinx@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Jiri Pirko <jiri@...nulli.us>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Casper Andersson <casper.casan@...il.com>,
        Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
        Jakob Koschel <jakobkoschel@...il.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Arnd Bergmann <arnd@...db.de>,
        Colin Ian King <colin.king@...el.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Xu Wang <vulab@...as.ac.cn>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, bpf@...r.kernel.org,
        Mike Rapoport <rppt@...nel.org>,
        "Brian Johannesmeyer" <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: [PATCH net-next v4 15/18] net: netcp: Remove usage of list iterator for list_add() after loop body

In preparation to limit the scope of a list iterator to the list
traversal loop, use a dedicated pointer pointing to the location
where the element should be inserted [1].

Before, the code implicitly used the head when no element was found
when using &next->list. The new 'pos' variable is set to the list head
by default and overwritten if the list exits early, marking the
insertion point for list_add().

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
---
 drivers/net/ethernet/ti/netcp_core.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/ti/netcp_core.c b/drivers/net/ethernet/ti/netcp_core.c
index 16507bff652a..f25104b5a31b 100644
--- a/drivers/net/ethernet/ti/netcp_core.c
+++ b/drivers/net/ethernet/ti/netcp_core.c
@@ -471,6 +471,7 @@ struct netcp_hook_list {
 int netcp_register_txhook(struct netcp_intf *netcp_priv, int order,
 			  netcp_hook_rtn *hook_rtn, void *hook_data)
 {
+	struct list_head *pos = &netcp_priv->txhook_list_head;
 	struct netcp_hook_list *entry;
 	struct netcp_hook_list *next;
 	unsigned long flags;
@@ -485,10 +486,12 @@ int netcp_register_txhook(struct netcp_intf *netcp_priv, int order,
 
 	spin_lock_irqsave(&netcp_priv->lock, flags);
 	list_for_each_entry(next, &netcp_priv->txhook_list_head, list) {
-		if (next->order > order)
+		if (next->order > order) {
+			pos = &next->list;
 			break;
+		}
 	}
-	__list_add(&entry->list, next->list.prev, &next->list);
+	list_add_tail(&entry->list, pos);
 	spin_unlock_irqrestore(&netcp_priv->lock, flags);
 
 	return 0;
@@ -520,6 +523,7 @@ EXPORT_SYMBOL_GPL(netcp_unregister_txhook);
 int netcp_register_rxhook(struct netcp_intf *netcp_priv, int order,
 			  netcp_hook_rtn *hook_rtn, void *hook_data)
 {
+	struct list_head *pos = &netcp_priv->rxhook_list_head;
 	struct netcp_hook_list *entry;
 	struct netcp_hook_list *next;
 	unsigned long flags;
@@ -534,10 +538,12 @@ int netcp_register_rxhook(struct netcp_intf *netcp_priv, int order,
 
 	spin_lock_irqsave(&netcp_priv->lock, flags);
 	list_for_each_entry(next, &netcp_priv->rxhook_list_head, list) {
-		if (next->order > order)
+		if (next->order > order) {
+			pos = &next->list;
 			break;
+		}
 	}
-	__list_add(&entry->list, next->list.prev, &next->list);
+	list_add_tail(&entry->list, pos);
 	spin_unlock_irqrestore(&netcp_priv->lock, flags);
 
 	return 0;
-- 
2.25.1