linux-kernel - Re: [PATCH net-next] virtio_net: Fix napi_skb_cache

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Message-ID: <20240905-sassy-aboriginal-crocodile-cfadde@devvm32600>
Date: Thu, 5 Sep 2024 02:03:21 -0700
From: Breno Leitao <leitao@...ian.org>
To: Leonardo Bras <leobras@...hat.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	rbc@...a.com, horms@...nel.org,
	"open list:VIRTIO CORE AND NET DRIVERS" <virtualization@...ts.linux.dev>,
	"open list:NETWORKING DRIVERS" <netdev@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] virtio_net: Fix napi_skb_cache_put warning

Hello Leonardo, good to see you here,

On Tue, Sep 03, 2024 at 01:28:50PM -0300, Leonardo Bras wrote:
> Please help me check if the following is correct:
> ###
> Any tree which includes df133f3f9625 ("virtio_net: bulk free tx skbs") 
> should also include your patch, since it fixes stuff in there.
> 
> The fact that the warning was only made visible in 
> bdacf3e34945 ("net: Use nested-BH locking for napi_alloc_cache.")
> does not change the fact that it was already present before.
> 
> Also, having bdacf3e34945 is not necessary for the backport, since
> it only made the bug visible.
> ###
> 
> Are above statements right?

That is exactly correct.

The bug was introduced by df133f3f9625 ("virtio_net: bulk free tx
skbs"), but it was not visible until bdacf3e34945 ("net: Use nested-BH
locking for napi_alloc_cache.") landed.

You don't need bdacf3e34945 ("net: Use nested-BH locking for
napi_alloc_cache.") patch backported if you don't want to.

I hope it helps,
--breno