NFS: send state management on a single connection.

With NFSv4.1, different network connections need to be explicitly
bound to a session.  During session startup, this is not possible
so only a single connection must be used for session startup.

So add a task flag to disable the default round-robin choice of
connections (when nconnect > 1) and force the use of a single
connection.
Then use that flag on all requests for session management - for
consistence, include NFSv4.0 management (SETCLIENTID) and session
destruction
Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/nfs4proc.c

@@ -5992,7 +5992,7 @@ int nfs4_proc_setclientid(struct nfs_client *clp, u32 program,
 		.rpc_message = &msg,
 		.callback_ops = &nfs4_setclientid_ops,
 		.callback_data = &setclientid,
-		.flags = RPC_TASK_TIMEOUT,
+		.flags = RPC_TASK_TIMEOUT | RPC_TASK_NO_ROUND_ROBIN,
 	};
 	int status;
 
@@ -6058,7 +6058,8 @@ int nfs4_proc_setclientid_confirm(struct nfs_client *clp,
 	dprintk("NFS call  setclientid_confirm auth=%s, (client ID %llx)\n",
 		clp->cl_rpcclient->cl_auth->au_ops->au_name,
 		clp->cl_clientid);
-	status = rpc_call_sync(clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
+	status = rpc_call_sync(clp->cl_rpcclient, &msg,
+			       RPC_TASK_TIMEOUT | RPC_TASK_NO_ROUND_ROBIN);
 	trace_nfs4_setclientid_confirm(clp, status);
 	dprintk("NFS reply setclientid_confirm: %d\n", status);
 	return status;
@@ -7639,7 +7640,7 @@ static int _nfs4_proc_secinfo(struct inode *dir, const struct qstr *name, struct
 		NFS_SP4_MACH_CRED_SECINFO, &clnt, &msg);
 
 	status = nfs4_call_sync(clnt, NFS_SERVER(dir), &msg, &args.seq_args,
-				&res.seq_res, 0);
+				&res.seq_res, RPC_TASK_NO_ROUND_ROBIN);
 	dprintk("NFS reply  secinfo: %d\n", status);
 
 	put_cred(cred);
@@ -7977,7 +7978,7 @@ nfs4_run_exchange_id(struct nfs_client *clp, const struct cred *cred,
 		.rpc_client = clp->cl_rpcclient,
 		.callback_ops = &nfs4_exchange_id_call_ops,
 		.rpc_message = &msg,
-		.flags = RPC_TASK_TIMEOUT,
+		.flags = RPC_TASK_TIMEOUT | RPC_TASK_NO_ROUND_ROBIN,
 	};
 	struct nfs41_exchange_id_data *calldata;
 	int status;
@@ -8202,7 +8203,8 @@ static int _nfs4_proc_destroy_clientid(struct nfs_client *clp,
 	};
 	int status;
 
-	status = rpc_call_sync(clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
+	status = rpc_call_sync(clp->cl_rpcclient, &msg,
+			       RPC_TASK_TIMEOUT | RPC_TASK_NO_ROUND_ROBIN);
 	trace_nfs4_destroy_clientid(clp, status);
 	if (status)
 		dprintk("NFS: Got error %d from the server %s on "
@@ -8481,7 +8483,8 @@ static int _nfs4_proc_create_session(struct nfs_client *clp,
 	nfs4_init_channel_attrs(&args, clp->cl_rpcclient);
 	args.flags = (SESSION4_PERSIST | SESSION4_BACK_CHAN);
 
-	status = rpc_call_sync(session->clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
+	status = rpc_call_sync(session->clp->cl_rpcclient, &msg,
+			       RPC_TASK_TIMEOUT | RPC_TASK_NO_ROUND_ROBIN);
 	trace_nfs4_create_session(clp, status);
 
 	switch (status) {
@@ -8557,7 +8560,8 @@ int nfs4_proc_destroy_session(struct nfs4_session *session,
 	if (!test_and_clear_bit(NFS4_SESSION_ESTABLISHED, &session->session_state))
 		return 0;
 
-	status = rpc_call_sync(session->clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
+	status = rpc_call_sync(session->clp->cl_rpcclient, &msg,
+			       RPC_TASK_TIMEOUT | RPC_TASK_NO_ROUND_ROBIN);
 	trace_nfs4_destroy_session(session->clp, status);
 
 	if (status)
@@ -8811,7 +8815,7 @@ static int nfs41_proc_reclaim_complete(struct nfs_client *clp,
 		.rpc_client = clp->cl_rpcclient,
 		.rpc_message = &msg,
 		.callback_ops = &nfs4_reclaim_complete_call_ops,
-		.flags = RPC_TASK_ASYNC,
+		.flags = RPC_TASK_ASYNC | RPC_TASK_NO_ROUND_ROBIN,
 	};
 	int status = -ENOMEM;
 
@@ -9330,7 +9334,7 @@ _nfs41_proc_secinfo_no_name(struct nfs_server *server, struct nfs_fh *fhandle,
 
 	dprintk("--> %s\n", __func__);
 	status = nfs4_call_sync(clnt, server, &msg, &args.seq_args,
-				&res.seq_res, 0);
+				&res.seq_res, RPC_TASK_NO_ROUND_ROBIN);
 	dprintk("<-- %s status=%d\n", __func__, status);
 
 	put_cred(cred);

include/linux/sunrpc/sched.h

@@ -126,6 +126,7 @@ struct rpc_task_setup {
 #define RPC_CALL_MAJORSEEN	0x0020		/* major timeout seen */
 #define RPC_TASK_ROOTCREDS	0x0040		/* force root creds */
 #define RPC_TASK_DYNAMIC	0x0080		/* task was kmalloc'ed */
+#define	RPC_TASK_NO_ROUND_ROBIN	0x0100		/* send requests on "main" xprt */
 #define RPC_TASK_SOFT		0x0200		/* Use soft timeouts */
 #define RPC_TASK_SOFTCONN	0x0400		/* Fail if can't connect */
 #define RPC_TASK_SENT		0x0800		/* message was sent */

net/sunrpc/clnt.c

@@ -995,6 +995,24 @@ rpc_task_get_xprt(struct rpc_clnt *clnt)
 	return xprt;
 }
 
+static struct rpc_xprt *
+rpc_task_get_first_xprt(struct rpc_clnt *clnt)
+{
+	struct rpc_xprt_switch *xps;
+	struct rpc_xprt *xprt;
+
+	rcu_read_lock();
+	xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
+	if (xprt) {
+		atomic_long_inc(&xprt->queuelen);
+		xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch);
+		atomic_long_inc(&xps->xps_queuelen);
+	}
+	rcu_read_unlock();
+
+	return xprt;
+}
+
 static void
 rpc_task_release_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
 {
@@ -1042,7 +1060,11 @@ void rpc_task_release_client(struct rpc_task *task)
 static
 void rpc_task_set_transport(struct rpc_task *task, struct rpc_clnt *clnt)
 {
-	if (!task->tk_xprt)
+	if (task->tk_xprt)
+		return;
+	if (task->tk_flags & RPC_TASK_NO_ROUND_ROBIN)
+		task->tk_xprt = rpc_task_get_first_xprt(clnt);
+	else
 		task->tk_xprt = rpc_task_get_xprt(clnt);
 }