Subject: Re: [patch net 1/2] mlxsw: spectrum: Fix refcount bug on span entries

From: Ido Schimmel <[email-masked]>
Date: Fri, 11 Nov 2016 14:49:28 +0200

On Fri, Nov 11, 2016 at 11:20:41AM +0100, Jiri Pirko wrote:
> From: Yotam Gigi <[email-masked]>
> 
> When binding port to a newly created span entry, its refcount is set 0
> even though it has a bound port. That leeds to unexpected behaviour when

s/leeds/leads/

> the user tries to delete that port from the span entry.
> 
> Change the binding process to increase the refcount of the bound entry
> even if the entry is newly created, and add warning on the process of
> removing bound port from entry when its refcount is 0.
> 
> Fixes: 763b4b70afcd3 ("mlxsw: spectrum: Add support in matchall mirror TC offloading")

You only need the first 12 characters.

> Signed-off-by: Yotam Gigi <[email-masked]>
> Signed-off-by: Jiri Pirko <[email-masked]>
> ---
>  drivers/net/ethernet/mellanox/mlxsw/spectrum.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
> index 1ec0a4c..d75c1ff 100644
> --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
> +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum.c
> @@ -269,17 +269,18 @@ static struct mlxsw_sp_span_entry
>  	struct mlxsw_sp_span_entry *span_entry;
>  
>  	span_entry = mlxsw_sp_span_entry_find(port);
> -	if (span_entry) {
> -		span_entry->ref_count++;
> -		return span_entry;
> -	}
> +	if (!span_entry)
> +		span_entry = mlxsw_sp_span_entry_create(port);
>  
> -	return mlxsw_sp_span_entry_create(port);
> +	span_entry->ref_count++;

mlxsw_sp_span_entry_create() can return NULL. You can look at
mlxsw_sp_fib_entry_get() for reference.

> +	return span_entry;
>  }
>  
>  static int mlxsw_sp_span_entry_put(struct mlxsw_sp *mlxsw_sp,
>  				   struct mlxsw_sp_span_entry *span_entry)
>  {
> +	WARN_ON(!span_entry->ref_count);
> +
>  	if (--span_entry->ref_count == 0)
>  		mlxsw_sp_span_entry_destroy(mlxsw_sp, span_entry);
>  	return 0;
> -- 
> 2.7.4
>