Subject: Re: [RFC PATCH v1 03/10] net: qrtr: support identical node ids

From: Simon Horman <[email-masked]>
Date: Sat, 19 Oct 2024 10:18:17 +0100

On Fri, Oct 18, 2024 at 01:18:21PM -0500, Denis Kenzior wrote:
> Add support for tracking multiple endpoints that may have conflicting
> node identifiers. This is achieved by using both the node and endpoint
> identifiers as the key inside the radix_tree data structure.
> 
> For backward compatibility with existing clients, the previous key
> schema (node identifier only) is preserved. However, this schema will
> only support the first endpoint/node combination.  This is acceptable
> for legacy clients as support for multiple endpoints with conflicting
> node identifiers was not previously possible.
> 
> Signed-off-by: Denis Kenzior <[email-masked]>
> Reviewed-by: Marcel Holtmann <[email-masked]>
> Reviewed-by: Andy Gross <[email-masked]>
> ---
>  net/qrtr/af_qrtr.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/net/qrtr/af_qrtr.c b/net/qrtr/af_qrtr.c
> index be275871fb2a..e83d491a8da9 100644
> --- a/net/qrtr/af_qrtr.c
> +++ b/net/qrtr/af_qrtr.c
> @@ -418,12 +418,20 @@ static struct qrtr_node *qrtr_node_lookup(unsigned int nid)
>  static void qrtr_node_assign(struct qrtr_node *node, unsigned int nid)
>  {
>  	unsigned long flags;
> +	unsigned long key;
>  
>  	if (nid == QRTR_EP_NID_AUTO)
>  		return;
>  
>  	spin_lock_irqsave(&qrtr_nodes_lock, flags);
> -	radix_tree_insert(&qrtr_nodes, nid, node);
> +
> +	/* Always insert with the endpoint_id + node_id */
> +	key = (unsigned long)node->ep->id << 32 | nid;

Hi Denis,

On systems with 32-bit longs, such as ARM, this will overflow.

> +	radix_tree_insert(&qrtr_nodes, key, node);
> +
> +	if (!radix_tree_lookup(&qrtr_nodes, nid))
> +		radix_tree_insert(&qrtr_nodes, nid, node);
> +
>  	if (node->nid == QRTR_EP_NID_AUTO)
>  		node->nid = nid;
>  	spin_unlock_irqrestore(&qrtr_nodes_lock, flags);
> -- 
> 2.45.2
> 
>