RDMA/ucma: Support querying when IB paths are not reversible

The current query_route call can return up to two path records.  The
assumption being that one is the primary path, with optional support
for an alternate path.  In both cases, the paths are assumed to be
reversible and are used to send CM MADs.

With the ability to manually set IB path data, the rdma cm can
eventually be capable of using up to 6 paths per connection:

	forward primary, reverse primary,
	forward alternate, reverse alternate,
	reversible primary path for CM MADs
	reversible alternate path for CM MADs.

(It is unclear at this time if IB routing will complicate this)  In
order to handle more flexible routing topologies, add a new command to
report any number of paths.
Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/core/ucma.c

@@ -750,6 +750,38 @@ static ssize_t ucma_query_addr(struct ucma_context *ctx,
 	return ret;
 }
 
+static ssize_t ucma_query_path(struct ucma_context *ctx,
+			       void __user *response, int out_len)
+{
+	struct rdma_ucm_query_path_resp *resp;
+	int i, ret = 0;
+
+	if (out_len < sizeof(*resp))
+		return -ENOSPC;
+
+	resp = kzalloc(out_len, GFP_KERNEL);
+	if (!resp)
+		return -ENOMEM;
+
+	resp->num_paths = ctx->cm_id->route.num_paths;
+	for (i = 0, out_len -= sizeof(*resp);
+	     i < resp->num_paths && out_len > sizeof(struct ib_path_rec_data);
+	     i++, out_len -= sizeof(struct ib_path_rec_data)) {
+
+		resp->path_data[i].flags = IB_PATH_GMP | IB_PATH_PRIMARY |
+					   IB_PATH_BIDIRECTIONAL;
+		ib_sa_pack_path(&ctx->cm_id->route.path_rec[i],
+				&resp->path_data[i].path_rec);
+	}
+
+	if (copy_to_user(response, resp,
+			 sizeof(*resp) + (i * sizeof(struct ib_path_rec_data))))
+		ret = -EFAULT;
+
+	kfree(resp);
+	return ret;
+}
+
 static ssize_t ucma_query(struct ucma_file *file,
 			  const char __user *inbuf,
 			  int in_len, int out_len)
@@ -771,6 +803,9 @@ static ssize_t ucma_query(struct ucma_file *file,
 	case RDMA_USER_CM_QUERY_ADDR:
 		ret = ucma_query_addr(ctx, response, out_len);
 		break;
+	case RDMA_USER_CM_QUERY_PATH:
+		ret = ucma_query_path(ctx, response, out_len);
+		break;
 	default:
 		ret = -ENOSYS;
 		break;

include/uapi/rdma/rdma_user_cm.h

@@ -115,7 +115,8 @@ struct rdma_ucm_resolve_route {
 };
 
 enum {
-	RDMA_USER_CM_QUERY_ADDR
+	RDMA_USER_CM_QUERY_ADDR,
+	RDMA_USER_CM_QUERY_PATH
 };
 
 struct rdma_ucm_query {
@@ -145,6 +146,12 @@ struct rdma_ucm_query_addr_resp {
 	struct sockaddr_storage dst_addr;
 };
 
+struct rdma_ucm_query_path_resp {
+	__u32 num_paths;
+	__u32 reserved;
+	struct ib_path_rec_data path_data[0];
+};
+
 struct rdma_ucm_conn_param {
 	__u32 qp_num;
 	__u32 qkey;