linux-kernel - Re: [PATCH net-next v6 2/9] vsock: add net to vsock skb cb

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Message-ID: <bnsgxged7onwkc4jxxttt6b5yb5ct5xekhybdhcduy75rwwprh@u5o6o3gtgvlj>
Date: Fri, 26 Sep 2025 18:15:37 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Bobby Eshleman <bobbyeshleman@...il.com>,
	g@...rzare-redhat.smtp.subspace.kernel.org
Cc: Shuah Khan <shuah@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Stefan Hajnoczi <stefanha@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, 
	Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	Eugenio Pérez <eperezma@...hat.com>, "K. Y. Srinivasan" <kys@...rosoft.com>, 
	Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>, 
	Bryan Tan <bryan-bt.tan@...adcom.com>, Vishnu Dasa <vishnu.dasa@...adcom.com>, 
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, virtualization@...ts.linux.dev, netdev@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	linux-hyperv@...r.kernel.org, berrange@...hat.com, Bobby Eshleman <bobbyeshleman@...a.com>
Subject: Re: [PATCH net-next v6 2/9] vsock: add net to vsock skb cb

On Tue, Sep 16, 2025 at 04:43:46PM -0700, Bobby Eshleman wrote:
>From: Bobby Eshleman <bobbyeshleman@...a.com>
>
>Add a net pointer and orig_net_mode to the vsock skb and helpers for

Why? (Please try to always add the reason we are doing something in each 
commit to simplify the life of reviewers but also for the future).

It takes a lot of time to understand why we need to store these info for 
each skb.

>getting/setting them.  This is in preparation for adding vsock NS
>support.
>
>Signed-off-by: Bobby Eshleman <bobbyeshleman@...a.com>
>
>---
>Changes in v5:
>- some diff context change due to rebase to current net-next
>---
> include/linux/virtio_vsock.h | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
>diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>index 0c67543a45c8..ea955892488a 100644
>--- a/include/linux/virtio_vsock.h
>+++ b/include/linux/virtio_vsock.h
>@@ -13,6 +13,8 @@ struct virtio_vsock_skb_cb {
> 	bool reply;
> 	bool tap_delivered;
> 	u32 offset;
>+	struct net *net;
>+	enum vsock_net_mode orig_net_mode;
> };

This structure starting to get big and isn't optimized in terms of 
layout. Since it's basically in every packet, should we start thinking 
about optimizing this structure?

Thanks,
Stefano

>
> #define VIRTIO_VSOCK_SKB_CB(skb) ((struct virtio_vsock_skb_cb *)((skb)->cb))
>@@ -130,6 +132,27 @@ static inline size_t virtio_vsock_skb_len(struct sk_buff *skb)
> 	return (size_t)(skb_end_pointer(skb) - skb->head);
> }
>
>+static inline struct net *virtio_vsock_skb_net(struct sk_buff *skb)
>+{
>+	return VIRTIO_VSOCK_SKB_CB(skb)->net;
>+}
>+
>+static inline void virtio_vsock_skb_set_net(struct sk_buff *skb, struct net *net)
>+{
>+	VIRTIO_VSOCK_SKB_CB(skb)->net = net;
>+}
>+
>+static inline enum vsock_net_mode virtio_vsock_skb_orig_net_mode(struct sk_buff *skb)
>+{
>+	return VIRTIO_VSOCK_SKB_CB(skb)->orig_net_mode;
>+}
>+
>+static inline void virtio_vsock_skb_set_orig_net_mode(struct sk_buff *skb,
>+						      enum vsock_net_mode orig_net_mode)
>+{
>+	VIRTIO_VSOCK_SKB_CB(skb)->orig_net_mode = orig_net_mode;
>+}
>+
> /* Dimension the RX SKB so that the entire thing fits exactly into
>  * a single 4KiB page. This avoids wasting memory due to alloc_skb()
>  * rounding up to the next page order and also means that we
>
>-- 
>2.47.3
>