linux-kernel - [PATCH v2 4/5] 9p: virtio: skip incrementing unused variable

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Message-Id: <20230427-scan-build-v2-4-bb96a6e6a33b@codewreck.org>
Date:   Wed, 03 May 2023 16:49:28 +0900
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     Eric Van Hensbergen <ericvh@...il.com>,
        Latchesar Ionkov <lucho@...kov.net>,
        Christian Schoenebeck <linux_oss@...debyte.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     Simon Horman <simon.horman@...igine.com>, v9fs@...ts.linux.dev,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Dominique Martinet <asmadeus@...ewreck.org>
Subject: [PATCH v2 4/5] 9p: virtio: skip incrementing unused variable

Fix the following scan-build warning:
net/9p/trans_virtio.c:504:3: warning: Value stored to 'in' is never read [deadcode.DeadStores]
                in += pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
                ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I'm honestly not 100% sure about this one; I'm tempted to think we
could (should?) just check the return value of pack_sg_list_p to skip
the in_sgs++ and setting sgs[] if it didn't process anything, but I'm
not sure it should ever happen so this is probably fine as is.

Just removing the assignment at least makes it clear the return value
isn't used, so it's an improvement in terms of readability.

Reviewed-by: Simon Horman <simon.horman@...igine.com>
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
---
 net/9p/trans_virtio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index f3f678289423..e305071eb7b8 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -501,8 +501,8 @@ p9_virtio_zc_request(struct p9_client *client, struct p9_req_t *req,
 
 	if (in_pages) {
 		sgs[out_sgs + in_sgs++] = chan->sg + out + in;
-		in += pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
-				     in_pages, in_nr_pages, offs, inlen);
+		pack_sg_list_p(chan->sg, out + in, VIRTQUEUE_NUM,
+			       in_pages, in_nr_pages, offs, inlen);
 	}
 
 	BUG_ON(out_sgs + in_sgs > ARRAY_SIZE(sgs));

-- 
2.39.2