SUNRPC: xprt_load_transport() needs to support the netid "rdma6"

According to RFC5666, the correct netid for an IPv6 addressed RDMA
transport is "rdma6", which we've supported as a mount option since
Linux-4.7. The problem is when we try to load the module "xprtrdma6",
that will fail, since there is no modulealias of that name.

Fixes: 181342c5ebe8 ("xprtrdma: Add rdma6 option to support NFS/RDMA IPv6")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

1 files changed, 49 insertions, 16 deletions

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index f6c17e75f20e..57f09ea3ef2a 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -151,31 +151,64 @@ out:
 }
 EXPORT_SYMBOL_GPL(xprt_unregister_transport);
 
+static void
+xprt_class_release(const struct xprt_class *t)
+{
+	module_put(t->owner);
+}
+
+static const struct xprt_class *
+xprt_class_find_by_netid_locked(const char *netid)
+{
+	const struct xprt_class *t;
+	unsigned int i;
+
+	list_for_each_entry(t, &xprt_list, list) {
+		for (i = 0; t->netid[i][0] != '\0'; i++) {
+			if (strcmp(t->netid[i], netid) != 0)
+				continue;
+			if (!try_module_get(t->owner))
+				continue;
+			return t;
+		}
+	}
+	return NULL;
+}
+
+static const struct xprt_class *
+xprt_class_find_by_netid(const char *netid)
+{
+	const struct xprt_class *t;
+
+	spin_lock(&xprt_list_lock);
+	t = xprt_class_find_by_netid_locked(netid);
+	if (!t) {
+		spin_unlock(&xprt_list_lock);
+		request_module("rpc%s", netid);
+		spin_lock(&xprt_list_lock);
+		t = xprt_class_find_by_netid_locked(netid);
+	}
+	spin_unlock(&xprt_list_lock);
+	return t;
+}
+
 /**
  * xprt_load_transport - load a transport implementation
- * @transport_name: transport to load
+ * @netid: transport to load
  *
  * Returns:
  * 0:		transport successfully loaded
  * -ENOENT:	transport module not available
  */
-int xprt_load_transport(const char *transport_name)
+int xprt_load_transport(const char *netid)
 {
-	struct xprt_class *t;
-	int result;
+	const struct xprt_class *t;
 
-	result = 0;
-	spin_lock(&xprt_list_lock);
-	list_for_each_entry(t, &xprt_list, list) {
-		if (strcmp(t->name, transport_name) == 0) {
-			spin_unlock(&xprt_list_lock);
-			goto out;
-		}
-	}
-	spin_unlock(&xprt_list_lock);
-	result = request_module("xprt%s", transport_name);
-out:
-	return result;
+	t = xprt_class_find_by_netid(netid);
+	if (!t)
+		return -ENOENT;
+	xprt_class_release(t);
+	return 0;
 }
 EXPORT_SYMBOL_GPL(xprt_load_transport);