linux-kernel - Re: [PATCH net-next] virtio_net: Fix error code in __virtnet_get_hw

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Date: Sun, 12 May 2024 12:01:55 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Jason Wang <jasowang@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	virtualization@...ts.linux.dev, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH net-next] virtio_net: Fix error code in
 __virtnet_get_hw_stats()

On Fri, May 10, 2024 at 03:50:45PM +0300, Dan Carpenter wrote:
> The virtnet_send_command_reply() function returns true on success or
> false on failure.  The "ok" variable is true/false depending on whether
> it succeeds or not.  It's up to the caller to translate the true/false
> into -EINVAL on failure or zero for success.
> 
> The bug is that __virtnet_get_hw_stats() returns false for both
> errors and success.  It's not a bug, but it is confusing that the caller
> virtnet_get_hw_stats() uses an "ok" variable to store negative error
> codes.

The bug is ... It's not a bug ....

I think what you are trying to say is that the error isn't
really handled anyway, except for printing a warning,
so it's not a big deal.

Right?

I don't know why can't get_ethtool_stats fail - we should
probably fix that.


> Fix the bug and clean things up so that it's clear that
> __virtnet_get_hw_stats() returns zero on success or negative error codes
> on failure.
> 
> Fixes: 941168f8b40e ("virtio_net: support device stats")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>  drivers/net/virtio_net.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 218a446c4c27..4fc0fcdad259 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -4016,7 +4016,7 @@ static int __virtnet_get_hw_stats(struct virtnet_info *vi,
>  					&sgs_out, &sgs_in);
>  
>  	if (!ok)
> -		return ok;
> +		return -EINVAL;
>  
>  	for (p = reply; p - reply < res_size; p += le16_to_cpu(hdr->size)) {
>  		hdr = p;
> @@ -4053,7 +4053,7 @@ static int virtnet_get_hw_stats(struct virtnet_info *vi,
>  	struct virtio_net_ctrl_queue_stats *req;
>  	bool enable_cvq;
>  	void *reply;
> -	int ok;
> +	int err;
>  
>  	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_DEVICE_STATS))
>  		return 0;
> @@ -4100,12 +4100,12 @@ static int virtnet_get_hw_stats(struct virtnet_info *vi,
>  	if (enable_cvq)
>  		virtnet_make_stat_req(vi, ctx, req, vi->max_queue_pairs * 2, &j);
>  
> -	ok = __virtnet_get_hw_stats(vi, ctx, req, sizeof(*req) * j, reply, res_size);
> +	err = __virtnet_get_hw_stats(vi, ctx, req, sizeof(*req) * j, reply, res_size);
>  
>  	kfree(req);
>  	kfree(reply);
>  
> -	return ok;
> +	return err;
>  }
>  
>  static void virtnet_get_strings(struct net_device *dev, u32 stringset, u8 *data)