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From:   Jakob Koschel <jakobkoschel@gmail.com>
To:     "David S. Miller" <davem@davemloft.net>
Cc:     Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
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        Vladimir Oltean <olteanv@gmail.com>,
        Lars Povlsen <lars.povlsen@microchip.com>,
        Steen Hegelund <Steen.Hegelund@microchip.com>,
        UNGLinuxDriver@microchip.com, Ariel Elior <aelior@marvell.com>,
        Manish Chopra <manishc@marvell.com>,
        Edward Cree <ecree.xilinx@gmail.com>,
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        Jiri Pirko <jiri@resnulli.us>,
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        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Casper Andersson <casper.casan@gmail.com>,
        Jakob Koschel <jakobkoschel@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>, Jason Gunthorpe <jgg@ziepe.ca>,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
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        Eric Dumazet <edumazet@google.com>,
        Xu Wang <vulab@iscas.ac.cn>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linuxppc-dev@lists.ozlabs.org, bpf@vger.kernel.org,
        Mike Rapoport <rppt@kernel.org>,
        "Brian Johannesmeyer" <bjohannesmeyer@gmail.com>,
        Cristiano Giuffrida <c.giuffrida@vu.nl>,
        "Bos, H.J." <h.j.bos@vu.nl>
Subject: [PATCH net-next v5 14/18] sfc: Remove usage of list iterator for list_add() after the loop body
Date:   Wed, 27 Apr 2022 18:06:31 +0200
Message-Id: <20220427160635.420492-15-jakobkoschel@gmail.com>
In-Reply-To: <20220427160635.420492-1-jakobkoschel@gmail.com>
References: <20220427160635.420492-1-jakobkoschel@gmail.com>
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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 &new->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@gmail.com>
---
 drivers/net/ethernet/sfc/rx_common.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/sfc/rx_common.c b/drivers/net/ethernet/sfc/rx_common.c
index fa8b9aacca11..74c056210e0b 100644
--- a/drivers/net/ethernet/sfc/rx_common.c
+++ b/drivers/net/ethernet/sfc/rx_common.c
@@ -560,14 +560,17 @@ struct efx_rss_context *efx_alloc_rss_context_entry(struct efx_nic *efx)
 {
 	struct list_head *head = &efx->rss_context.list;
 	struct efx_rss_context *ctx, *new;
+	struct list_head *pos = head;
 	u32 id = 1; /* Don't use zero, that refers to the master RSS context */
 
 	WARN_ON(!mutex_is_locked(&efx->rss_lock));
 
 	/* Search for first gap in the numbering */
 	list_for_each_entry(ctx, head, list) {
-		if (ctx->user_id != id)
+		if (ctx->user_id != id) {
+			pos = &ctx->list;
 			break;
+		}
 		id++;
 		/* Check for wrap.  If this happens, we have nearly 2^32
 		 * allocated RSS contexts, which seems unlikely.
@@ -585,7 +588,7 @@ struct efx_rss_context *efx_alloc_rss_context_entry(struct efx_nic *efx)
 
 	/* Insert the new entry into the gap */
 	new->user_id = id;
-	list_add_tail(&new->list, &ctx->list);
+	list_add_tail(&new->list, pos);
 	return new;
 }
 
-- 
2.25.1