netdev-genl: Add PID for the NAPI thread

In the threaded NAPI mode, expose the PID of the NAPI thread.
Signed-off-by: Amritha Nambiar <amritha.nambiar@intel.com>
Reviewed-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
Link: https://lore.kernel.org/r/170147335818.5260.10253384006102593087.stgit@anambiarhost.jf.intel.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/netdev-genl.c

@@ -163,6 +163,7 @@ netdev_nl_napi_fill_one(struct sk_buff *rsp, struct napi_struct *napi,
 			const struct genl_info *info)
 {
 	void *hdr;
+	pid_t pid;
 
 	if (WARN_ON_ONCE(!napi->dev))
 		return -EINVAL;
@@ -183,6 +184,12 @@ netdev_nl_napi_fill_one(struct sk_buff *rsp, struct napi_struct *napi,
 	if (napi->irq >= 0 && nla_put_u32(rsp, NETDEV_A_NAPI_IRQ, napi->irq))
 		goto nla_put_failure;
 
+	if (napi->thread) {
+		pid = task_pid_nr(napi->thread);
+		if (nla_put_u32(rsp, NETDEV_A_NAPI_PID, pid))
+			goto nla_put_failure;
+	}
+
 	genlmsg_end(rsp, hdr);
 
 	return 0;