netdev - Re: [RFC PATCH net-next v2 1/2] net: veth: Page pool creation error handling for existing pools only

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Date: Wed, 2 Aug 2023 10:56:15 +0200
From: Jesper Dangaard Brouer <hawk@...nel.org>
To: Liang Chen <liangchen.linux@...il.com>, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 linyunsheng@...wei.com
Cc: hawk@...nel.org, ilias.apalodimas@...aro.org, daniel@...earbox.net,
 ast@...nel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next v2 1/2] net: veth: Page pool creation error
 handling for existing pools only



On 01/08/2023 08.19, Liang Chen wrote:
> The failure handling procedure destroys page pools for all queues,
> including those that haven't had their page pool created yet. this patch
> introduces necessary adjustments to prevent potential risks and
> inconsistency with the error handling behavior.
> 
> Signed-off-by: Liang Chen <liangchen.linux@...il.com>
> ---
>   drivers/net/veth.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
> index 614f3e3efab0..509e901da41d 100644
> --- a/drivers/net/veth.c
> +++ b/drivers/net/veth.c
> @@ -1081,8 +1081,9 @@ static int __veth_napi_enable_range(struct net_device *dev, int start, int end)
>   err_xdp_ring:
>   	for (i--; i >= start; i--)
>   		ptr_ring_cleanup(&priv->rq[i].xdp_ring, veth_ptr_free);
> +	i = end;
>   err_page_pool:
> -	for (i = start; i < end; i++) {
> +	for (i--; i >= start; i--) {

I'm not a fan of this coding style, that iterates backwards, but I can
see you just inherited the existing style in this function.

>   		page_pool_destroy(priv->rq[i].page_pool);
>   		priv->rq[i].page_pool = NULL;
>   	}

The page_pool_destroy() call handles(exits) if called with NULL.
So, I don't think this incorrect walking all (start to end) can trigger 
an actual bug.

Anyhow, I do think this is more correct, so you can append my ACK for 
the real submission.

Acked-by: Jesper Dangaard Brouer <hawk@...nel.org>