NFSv4: Allow multiple connections to NFSv4.x (x>0) servers

If the user specifies the -onconn=<number> mount option, and the transport
protocol is TCP, then set up <number> connections to the server. The
connections will all go to the same IP address.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/client.c

@@ -175,6 +175,7 @@ struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init)
 	clp->cl_rpcclient = ERR_PTR(-EINVAL);
 
 	clp->cl_proto = cl_init->proto;
+	clp->cl_nconnect = cl_init->nconnect;
 	clp->cl_net = get_net(cl_init->net);
 
 	clp->cl_principal = "*";
@@ -493,6 +494,7 @@ int nfs_create_rpc_client(struct nfs_client *clp,
 	struct rpc_create_args args = {
 		.net		= clp->cl_net,
 		.protocol	= clp->cl_proto,
+		.nconnect	= clp->cl_nconnect,
 		.address	= (struct sockaddr *)&clp->cl_addr,
 		.addrsize	= clp->cl_addrlen,
 		.timeout	= cl_init->timeparms,

fs/nfs/internal.h

@@ -82,6 +82,7 @@ struct nfs_client_initdata {
 	struct nfs_subversion *nfs_mod;
 	int proto;
 	u32 minorversion;
+	unsigned int nconnect;
 	struct net *net;
 	const struct rpc_timeout *timeparms;
 	const struct cred *cred;

fs/nfs/nfs4client.c

@@ -859,7 +859,8 @@ static int nfs4_set_client(struct nfs_server *server,
 		const size_t addrlen,
 		const char *ip_addr,
 		int proto, const struct rpc_timeout *timeparms,
-		u32 minorversion, struct net *net)
+		u32 minorversion, unsigned int nconnect,
+		struct net *net)
 {
 	struct nfs_client_initdata cl_init = {
 		.hostname = hostname,
@@ -875,6 +876,8 @@ static int nfs4_set_client(struct nfs_server *server,
 	};
 	struct nfs_client *clp;
 
+	if (minorversion > 0 && proto == XPRT_TRANSPORT_TCP)
+		cl_init.nconnect = nconnect;
 	if (server->flags & NFS_MOUNT_NORESVPORT)
 		set_bit(NFS_CS_NORESVPORT, &cl_init.init_flags);
 	if (server->options & NFS_OPTION_MIGRATION)
@@ -1074,6 +1077,7 @@ static int nfs4_init_server(struct nfs_server *server,
 			data->nfs_server.protocol,
 			&timeparms,
 			data->minorversion,
+			data->nfs_server.nconnect,
 			data->net);
 	if (error < 0)
 		return error;
@@ -1163,6 +1167,7 @@ struct nfs_server *nfs4_create_referral_server(struct nfs_clone_mount *data,
 				XPRT_TRANSPORT_RDMA,
 				parent_server->client->cl_timeout,
 				parent_client->cl_mvops->minor_version,
+				parent_client->cl_nconnect,
 				parent_client->cl_net);
 	if (!error)
 		goto init_server;
@@ -1176,6 +1181,7 @@ struct nfs_server *nfs4_create_referral_server(struct nfs_clone_mount *data,
 				XPRT_TRANSPORT_TCP,
 				parent_server->client->cl_timeout,
 				parent_client->cl_mvops->minor_version,
+				parent_client->cl_nconnect,
 				parent_client->cl_net);
 	if (error < 0)
 		goto error;
@@ -1271,7 +1277,8 @@ int nfs4_update_server(struct nfs_server *server, const char *hostname,
 	set_bit(NFS_MIG_TSM_POSSIBLE, &server->mig_status);
 	error = nfs4_set_client(server, hostname, sap, salen, buf,
 				clp->cl_proto, clnt->cl_timeout,
-				clp->cl_minorversion, net);
+				clp->cl_minorversion,
+				clp->cl_nconnect, net);
 	clear_bit(NFS_MIG_TSM_POSSIBLE, &server->mig_status);
 	if (error != 0) {
 		nfs_server_insert_lists(server);

include/linux/nfs_fs_sb.h

@@ -58,6 +58,7 @@ struct nfs_client {
 	struct nfs_subversion *	cl_nfs_mod;	/* pointer to nfs version module */
 
 	u32			cl_minorversion;/* NFSv4 minorversion */
+	unsigned int		cl_nconnect;	/* Number of connections */
 	const char *		cl_principal;  /* used for machine cred */
 
 #if IS_ENABLED(CONFIG_NFS_V4)