RDMA/core: Add wait/retry version of ibnl_unicast

Add a wait/retry version of ibnl_unicast, ibnl_unicast_wait,
and modify ibnl_unicast to not wait/retry.  This eliminates
the undesirable wait for future users of ibnl_unicast.

Change Portmapper calls originating from kernel to user-space
to use ibnl_unicast_wait and take advantage of the wait/retry
logic in netlink_unicast.
Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Chien Tin Tung <chien.tin.tung@intel.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>

drivers/infiniband/core/iwpm_msg.c

@@ -174,7 +174,7 @@ int iwpm_add_mapping(struct iwpm_sa_data *pm_msg, u8 nl_client)
 		goto add_mapping_error;
 	nlmsg_request->req_buffer = pm_msg;
 
-	ret = ibnl_unicast(skb, nlh, iwpm_user_pid);
+	ret = ibnl_unicast_wait(skb, nlh, iwpm_user_pid);
 	if (ret) {
 		skb = NULL; /* skb is freed in the netlink send-op handling */
 		iwpm_user_pid = IWPM_PID_UNDEFINED;
@@ -251,7 +251,7 @@ int iwpm_add_and_query_mapping(struct iwpm_sa_data *pm_msg, u8 nl_client)
 		goto query_mapping_error;
 	nlmsg_request->req_buffer = pm_msg;
 
-	ret = ibnl_unicast(skb, nlh, iwpm_user_pid);
+	ret = ibnl_unicast_wait(skb, nlh, iwpm_user_pid);
 	if (ret) {
 		skb = NULL; /* skb is freed in the netlink send-op handling */
 		err_str = "Unable to send a nlmsg";
@@ -312,7 +312,7 @@ int iwpm_remove_mapping(struct sockaddr_storage *local_addr, u8 nl_client)
 	if (ret)
 		goto remove_mapping_error;
 
-	ret = ibnl_unicast(skb, nlh, iwpm_user_pid);
+	ret = ibnl_unicast_wait(skb, nlh, iwpm_user_pid);
 	if (ret) {
 		skb = NULL; /* skb is freed in the netlink send-op handling */
 		iwpm_user_pid = IWPM_PID_UNDEFINED;

drivers/infiniband/core/netlink.c

@@ -232,11 +232,21 @@ int ibnl_unicast(struct sk_buff *skb, struct nlmsghdr *nlh,
 {
 	int err;
 
-	err = netlink_unicast(nls, skb, pid, 0);
+	err = netlink_unicast(nls, skb, pid, MSG_DONTWAIT);
 	return (err < 0) ? err : 0;
 }
 EXPORT_SYMBOL(ibnl_unicast);
 
+int ibnl_unicast_wait(struct sk_buff *skb, struct nlmsghdr *nlh,
+		      __u32 pid)
+{
+	int err;
+
+	err = netlink_unicast(nls, skb, pid, 0);
+	return (err < 0) ? err : 0;
+}
+EXPORT_SYMBOL(ibnl_unicast_wait);
+
 int ibnl_multicast(struct sk_buff *skb, struct nlmsghdr *nlh,
 			unsigned int group, gfp_t flags)
 {

include/rdma/rdma_netlink.h

@@ -63,6 +63,16 @@ int ibnl_put_attr(struct sk_buff *skb, struct nlmsghdr *nlh,
 int ibnl_unicast(struct sk_buff *skb, struct nlmsghdr *nlh,
 			__u32 pid);
 
+/**
+ * Send, with wait/1 retry, the supplied skb to a specific userspace PID.
+ * @skb: The netlink skb
+ * @nlh: Header of the netlink message to send
+ * @pid: Userspace netlink process ID
+ * Returns 0 on success or a negative error code.
+ */
+int ibnl_unicast_wait(struct sk_buff *skb, struct nlmsghdr *nlh,
+		      __u32 pid);
+
 /**
  * Send the supplied skb to a netlink group.
  * @skb: The netlink skb