linux-kernel - [PATCH v2 3/8] vsock/virtio: Move length check to callers of virtio_vsock_skb_rx

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Message-Id: <20250701164507.14883-4-will@kernel.org>
Date: Tue,  1 Jul 2025 17:45:02 +0100
From: Will Deacon <will@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Will Deacon <will@...nel.org>,
	Keir Fraser <keirf@...gle.com>,
	Steven Moreland <smoreland@...gle.com>,
	Frederick Mayle <fmayle@...gle.com>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	Stefano Garzarella <sgarzare@...hat.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	netdev@...r.kernel.org,
	virtualization@...ts.linux.dev
Subject: [PATCH v2 3/8] vsock/virtio: Move length check to callers of virtio_vsock_skb_rx_put()

virtio_vsock_skb_rx_put() only calls skb_put() if the length in the
packet header is not zero even though skb_put() handles this case
gracefully.

Remove the functionally redundant check from virtio_vsock_skb_rx_put()
and, on the assumption that this is a worthwhile optimisation for
handling credit messages, augment the existing length checks in
virtio_transport_rx_work() to elide the call for zero-length payloads.
Note that the vhost code already has similar logic in
vhost_vsock_alloc_skb().

Signed-off-by: Will Deacon <will@...nel.org>
---
 include/linux/virtio_vsock.h     | 4 +---
 net/vmw_vsock/virtio_transport.c | 4 +++-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 36fb3edfa403..eb6980aa19fd 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -52,9 +52,7 @@ static inline void virtio_vsock_skb_rx_put(struct sk_buff *skb)
 	u32 len;
 
 	len = le32_to_cpu(virtio_vsock_hdr(skb)->len);
-
-	if (len > 0)
-		skb_put(skb, len);
+	skb_put(skb, len);
 }
 
 static inline struct sk_buff *virtio_vsock_alloc_skb(unsigned int size, gfp_t mask)
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index bd2c6aaa1a93..488e6ddc6ffa 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -656,7 +656,9 @@ static void virtio_transport_rx_work(struct work_struct *work)
 				continue;
 			}
 
-			virtio_vsock_skb_rx_put(skb);
+			if (payload_len)
+				virtio_vsock_skb_rx_put(skb);
+
 			virtio_transport_deliver_tap_pkt(skb);
 			virtio_transport_recv_pkt(&virtio_transport, skb);
 		}
-- 
2.50.0.727.gbf7dc18ff4-goog