Re: [PATCH rdma-next v1 06/11] RDMA/nldev: Add support to get status of all counters

From: Mark Zhang
Date: Tue Sep 28 2021 - 08:51:27 EST


On 9/28/2021 7:52 PM, Jason Gunthorpe wrote:
On Tue, Sep 28, 2021 at 05:12:39PM +0800, Mark Zhang wrote:
On 9/28/2021 1:30 AM, Jason Gunthorpe wrote:
On Wed, Sep 15, 2021 at 02:07:25AM +0300, Leon Romanovsky wrote:
+static int stat_get_doit_default_counter(struct sk_buff *skb,
+ struct nlmsghdr *nlh,
+ struct netlink_ext_ack *extack,
+ struct nlattr *tb[])
+{
+ struct rdma_hw_stats *stats;
+ struct ib_device *device;
+ u32 index, port;
+ int ret;
+
+ if (!tb[RDMA_NLDEV_ATTR_DEV_INDEX] || !tb[RDMA_NLDEV_ATTR_PORT_INDEX])
+ return -EINVAL;
+
+ index = nla_get_u32(tb[RDMA_NLDEV_ATTR_DEV_INDEX]);
+ device = ib_device_get_by_index(sock_net(skb->sk), index);
+ if (!device)
+ return -EINVAL;
+
+ port = nla_get_u32(tb[RDMA_NLDEV_ATTR_PORT_INDEX]);
+ if (!rdma_is_port_valid(device, port)) {
+ ret = -EINVAL;
+ goto end;
+ }
+
+ stats = ib_get_hw_stats_port(device, port);
+ if (!stats) {
+ ret = -EINVAL;
+ goto end;
+ }
+
+ if (tb[RDMA_NLDEV_ATTR_STAT_HWCOUNTER_DYNAMIC])
+ ret = stat_get_doit_stats_list(skb, nlh, extack, tb,
+ device, port, stats);
+ else
+ ret = stat_get_doit_stats_values(skb, nlh, extack, tb, device,
+ port, stats);

This seems strange, why is the output of a get contingent on a ignored
input attribute? Shouldn't the HWCOUNTER_DYNAMIC just always be
emitted?

The CMD_STAT_GET is originally used to get the default hwcounter statistic
(the value of all hwstats), now we also want to use this command to get a
list of counters (just name and status), so kernel differentiates these 2
cases based on HWCOUNTER_DYNAMIC attr.

Don't do that, it is not how netlink works. Either the whole attribute
should be returned or you need a new get command

Will add a new get command for backward compatibility, thanks.