[RFC PATCH v5 2/2] virtio/vsock: check argument to avoid no effect call

From: Arseniy Krasnov <avkrasnov@sberdevices.ru>
To: Stefan Hajnoczi <stefanha@redhat.com>,
	Stefano Garzarella <sgarzare@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Bobby Eshleman <bobby.eshleman@bytedance.com>
Cc: <kvm@vger.kernel.org>,
	<virtualization@lists.linux-foundation.org>,
	<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<kernel@sberdevices.ru>, <oxffffaa@gmail.com>,
	<avkrasnov@sberdevices.ru>
Subject: [RFC PATCH v5 2/2] virtio/vsock: check argument to avoid no effect call
Date: Wed, 22 Mar 2023 21:36:24 +0300	[thread overview]
Message-ID: <50bb0210-1ed7-42fb-b5f6-8d97247209b5@sberdevices.ru> (raw)
In-Reply-To: <f0b283a1-cc63-dc3d-cc0c-0da7f684d4d2@sberdevices.ru>

Both of these functions have no effect when input argument is 0, so to
avoid useless spinlock access, check argument before it.

Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
---
 net/vmw_vsock/virtio_transport_common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 9e87c7d4d7cf..312658c176bd 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -302,6 +302,9 @@ u32 virtio_transport_get_credit(struct virtio_vsock_sock *vvs, u32 credit)
 {
 	u32 ret;
 
+	if (!credit)
+		return 0;
+
 	spin_lock_bh(&vvs->tx_lock);
 	ret = vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt);
 	if (ret > credit)
@@ -315,6 +318,9 @@ EXPORT_SYMBOL_GPL(virtio_transport_get_credit);
 
 void virtio_transport_put_credit(struct virtio_vsock_sock *vvs, u32 credit)
 {
+	if (!credit)
+		return;
+
 	spin_lock_bh(&vvs->tx_lock);
 	vvs->tx_cnt -= credit;
 	spin_unlock_bh(&vvs->tx_lock);
-- 
2.25.1
