netdev - Re: [patch iproute2-next 1/3] devlink: query ifname for devlink port instead of map lookup

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Date:   Mon, 7 Nov 2022 08:16:42 -0700
From:   David Ahern <dsahern@...il.com>
To:     Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org
Cc:     sthemmin@...rosoft.com, kuba@...nel.org, moshe@...dia.com,
        aeedm@...dia.com
Subject: Re: [patch iproute2-next 1/3] devlink: query ifname for devlink port
 instead of map lookup

On 11/4/22 4:23 AM, Jiri Pirko wrote:
> From: Jiri Pirko <jiri@...dia.com>
> 
> ifname map is created once during init. However, ifnames can easily
> change during the devlink process runtime (e. g. devlink mon).

why not update the cache on name changes? Doing a query on print has
extra overhead. And, if you insist a per-print query is needed, why
leave ifname_map_list? what value does it serve if you query each time?


> Therefore, query ifname during each devlink port print.
> 
> Signed-off-by: Jiri Pirko <jiri@...dia.com>
> ---
>  devlink/devlink.c | 46 +++++++++++++++++++++++++++++++---------------
>  1 file changed, 31 insertions(+), 15 deletions(-)
> 
> diff --git a/devlink/devlink.c b/devlink/devlink.c
> index 8aefa101b2f8..680936f891cf 100644
> --- a/devlink/devlink.c
> +++ b/devlink/devlink.c
> @@ -864,21 +864,38 @@ static int ifname_map_lookup(struct dl *dl, const char *ifname,
>  	return -ENOENT;
>  }
>  
> -static int ifname_map_rev_lookup(struct dl *dl, const char *bus_name,
> -				 const char *dev_name, uint32_t port_index,
> -				 char **p_ifname)
> +static int port_ifname_get_cb(const struct nlmsghdr *nlh, void *data)
>  {
> -	struct ifname_map *ifname_map;
> +	struct genlmsghdr *genl = mnl_nlmsg_get_payload(nlh);
> +	struct nlattr *tb[DEVLINK_ATTR_MAX + 1] = {};
> +	char **p_ifname = data;
> +	const char *ifname;
>  
> -	list_for_each_entry(ifname_map, &dl->ifname_map_list, list) {
> -		if (strcmp(bus_name, ifname_map->bus_name) == 0 &&
> -		    strcmp(dev_name, ifname_map->dev_name) == 0 &&
> -		    port_index == ifname_map->port_index) {
> -			*p_ifname = ifname_map->ifname;
> -			return 0;
> -		}
> -	}
> -	return -ENOENT;
> +	mnl_attr_parse(nlh, sizeof(*genl), attr_cb, tb);
> +	if (!tb[DEVLINK_ATTR_PORT_NETDEV_NAME])
> +		return MNL_CB_ERROR;
> +
> +	ifname = mnl_attr_get_str(tb[DEVLINK_ATTR_PORT_NETDEV_NAME]);
> +	*p_ifname = strdup(ifname);
> +	if (!*p_ifname)
> +		return MNL_CB_ERROR;
> +
> +	return MNL_CB_OK;
> +}
> +
> +static int port_ifname_get(struct dl *dl, const char *bus_name,
> +			   const char *dev_name, uint32_t port_index,
> +			   char **p_ifname)
> +{
> +	struct nlmsghdr *nlh;
> +
> +	nlh = mnlu_gen_socket_cmd_prepare(&dl->nlg, DEVLINK_CMD_PORT_GET,
> +			       NLM_F_REQUEST | NLM_F_ACK);
> +	mnl_attr_put_strz(nlh, DEVLINK_ATTR_BUS_NAME, bus_name);
> +	mnl_attr_put_strz(nlh, DEVLINK_ATTR_DEV_NAME, dev_name);
> +	mnl_attr_put_u32(nlh, DEVLINK_ATTR_PORT_INDEX, port_index);
> +	return mnlu_gen_socket_sndrcv(&dl->nlg, nlh, port_ifname_get_cb,
> +				      p_ifname);
>  }
>  
>  static int strtobool(const char *str, bool *p_val)
> @@ -2577,8 +2594,7 @@ static void __pr_out_port_handle_start(struct dl *dl, const char *bus_name,
>  	char *ifname = NULL;
>  
>  	if (dl->no_nice_names || !try_nice ||
> -	    ifname_map_rev_lookup(dl, bus_name, dev_name,
> -				  port_index, &ifname) != 0)
> +	    port_ifname_get(dl, bus_name, dev_name, port_index, &ifname) != 0)
>  		sprintf(buf, "%s/%s/%d", bus_name, dev_name, port_index);
>  	else
>  		sprintf(buf, "%s", ifname);