linux-kernel - Re: [PATCH 1/6] hyperv: Make remove callback of hyperv driver void returned

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Message-ID: <Y48pdr9DEmXShhFR@liuwe-devbox-debian-v2>
Date:   Tue, 6 Dec 2022 11:37:26 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Dawei Li <set_pte_at@...look.com>
Cc:     gregkh@...uxfoundation.org, johannes@...solutions.net,
        robert.jarzmik@...e.fr, jgross@...e.com, sstabellini@...nel.org,
        oleksandr_tyshchenko@...m.com, roger.pau@...rix.com,
        srinivas.kandagatla@...aro.org, bgoswami@...cinc.com,
        mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
        kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, alsa-devel@...a-project.org,
        linuxppc-dev@...ts.ozlabs.org, xen-devel@...ts.xenproject.org,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] hyperv: Make remove callback of hyperv driver void
 returned

On Mon, Dec 05, 2022 at 11:36:39PM +0800, Dawei Li wrote:
> Since commit fc7a6209d571 ("bus: Make remove callback return
> void") forces bus_type::remove be void-returned, it doesn't
> make much sense for any bus based driver implementing remove
> callbalk to return non-void to its caller.
> 
> This change is for hyperv bus based drivers.
> 
> Signed-off-by: Dawei Li <set_pte_at@...look.com>
[...]
> -static int netvsc_remove(struct hv_device *dev)
> +static void netvsc_remove(struct hv_device *dev)
>  {
>  	struct net_device_context *ndev_ctx;
>  	struct net_device *vf_netdev, *net;
> @@ -2603,7 +2603,6 @@ static int netvsc_remove(struct hv_device *dev)
>  	net = hv_get_drvdata(dev);
>  	if (net == NULL) {
>  		dev_err(&dev->device, "No net device to remove\n");
> -		return 0;

This is wrong. You are introducing a NULL pointer dereference.

>  	}
>  
>  	ndev_ctx = netdev_priv(net);
> @@ -2637,7 +2636,6 @@ static int netvsc_remove(struct hv_device *dev)
>  
>  	free_percpu(ndev_ctx->vf_stats);
>  	free_netdev(net);
> -	return 0;
>  }
>  
>  static int netvsc_suspend(struct hv_device *dev)
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index ba64284eaf9f..3a09de70d6ea 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -3756,7 +3756,7 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
>   *
>   * Return: 0 on success, -errno on failure
>   */

This comment is no longer needed in the new world.

But, are you sure you're modifying the correct piece of code?

hv_pci_remove is not a hook in the base bus type. It is used in struct
hv_driver.

The same comment applies to all other modifications.

Thanks,
Wei.